Final Report Summary - FABRIGEN (Fabric structures for solar power generation)
Executive Summary:
FabriGen addresses the need to bring innovative products to the solar energy market to achieve the ambitious European targets for renewable energy generation. The FabriGen project aims to combine photovoltaic materials, both organic (OPV) and inorganic (CIGS and aSi) with tensile fabrics to enable the construction of solar-power generating fabric structures (TensilePV). These structures could be connected to the grid, or used for distributed power generation, and will enable generators to participate in Feed-In-Tariff (FIT) and other governmental incentive schemes that are being offered to promote the uptake of renewable energy technologies. Fabric-based TensilePV systems will reduce the cost of solar power towards that of conventional power (grid-parity) and so ultimately will not be reliant on governmental incentive schemes.
Product concept
The FabriGen product is a tensile membrane material that incorporates PV modules that can be used in a large variety of tensile membrane structures to generate electrical power directly from sunlight. The FabriGen structures are used for off-grid local power, or on-grid to offset, or feed power into national grids.
Project plan outline
The FabriGen project will implement commercial roll-to-roll printing technologies to deposit and pattern state-of-the-art PV materials and produce large-area PV modules (20 cm in research, scaling up to 100 cm roll width). Means to integrate the PV fabrication processes with polyester fabric membranes is being developed. A key aspect of the research is the development and integration of barrier and encapsulation layers to provide long-life performance needed for outdoor use (preventing water and oxygen permeation and blocking UV radiation). The use of innovative materials is being used to give enhanced UV response and improved resistance to UV degradation. The completed modules will be designed to meet EN61646 to prepare for micro-generation certification and exploitation in the market.
Benefits
• Dual-purpose structures e.g. shades, shelters, walkways, car ports, barns, thus offsetting the cost significantly
• Large areas can be covered at lower cost that glass panels
• Complex shapes to maximise solar collection
• Lower installation costs
• Lightweight, easy and low cost to transport
• Easy to move and relocate – e.g. farmers can use fallow ground and rotate with crop cycles
• Easier to replace and redistribute for re-use.
Target specifications and successes
• Cell efficiency: >10% - Achieved, with TensileCIGS.
• Module efficiency: >7% - Achieved, with TensileCIGS.
• Cost per Watt: <1 €/Wp – Achieved a roadmap towards this
• Power generation
• capacity (1 sun): >70 W/m2 - Achieved, with TensileCIGS
• Lifetime: >20 years – Achieved, by demonstrating successful integration of existing technologies into within tensile membranes.
• Levelised cost of electricity: <0.1€/kWh – is achievable with Fabrigen 2 and a productive manufacturing process.
•
Project Achievements
We have successfully built demonstrator units incorporating three different PV technologies.
These units are TensilePV membrane structures, each 6m long, by up to 3m wide and either meet the target specifications, or – in terms of production costs - demonstrate a clear roadmap to achieving the target specifications.
Project Context and Objectives:
The project: Fabric Structures for Solar Power Generation (FabriGen), addresses the need to bring innovative products to the solar energy market to achieve the ambitious European targets for renewable energy generation. The FabriGen project aims to combine organic photovoltaic (OPV) materials with tensile fabrics to enable the construction of solar-power generating fabric structures. These structures could be connected to the grid, or used for distributed power generation, and will enable generators to participate in Feed-In-Tariff (FIT) schemes that are being offered to promote the uptake of renewable energy technologies. Fabric-based OPV systems will reduce the cost of solar power towards that of conventional power (grid-parity) and so ultimately will not be reliant on FIT schemes.
The FabriGen project will implement commercial roll-to-roll printing technologies to deposit and pattern state-of- the-art PV materials and produce large-area PV modules (20cm in research, scaling up to 100cm roll width). Means to integrate the PV fabrication processes with polyester fabric membranes will be developed. A key aspect of the research will be development and integration of barrier and encapsulation layers to provide long-life performance needed for outdoor use (preventing water and oxygen permeation and blocking UV radiation). The use of innovative materials to give enhanced UV response and improved resistance to UV degradation will be researched. Compliance testing to EN61646 will be carried out on fabricated PV modules to prepare for microgeneration certification and exploitation in the market.
FabriGen product concept
The FabriGen product is a tensile membrane material that incorporates photovoltaic (PV) modules that can be used in a large variety of tensile membrane structures to generate electrical power directly from sunlight (Figure 1). The FabriGen product will be compliant with European and international standards and regulations regarding Feed-In-Tariff (FIT) schemes. This means that whether the FabriGen structures are used
for off-grid local power, or on-grid to offset, or feed power into national grids, the power generated will qualify for FIT payments, and so provide operators of the FabriGen product with an on-going revenue stream that will provide a return-on-investment.
Figure 1. In the FabriGen concept, flexible organic photovoltaic (OPV) solar cells are integrated with fabrics to enable the cost- effective production of clean, green electricity in tensile structures.
Table 1. Target specification for the FabriGen product
Table 1 lists the target specification for the FabriGen product. Achieving these figures in a flexible solar fabric would transform the solar energy market. There is nothing on the market today that achieves these specifications. Research and development are required to combine emerging research on OPV materials with large area printing technologies and develop cost-effective means to integrate solar cells with tensile membranes. The aim is to develop a new capability that can be rapidly productionised and taken to the market. In the short-to-medium term, feed-in-tariffs (currently 0.3-0.5 €/kWh in many European countries) mean that
there is significant incentive to invest in solar PV technologies with an interim performance specification, which can gradually increase towards the target listed in Table 1.
Appropriateness of the FabriGen project and objectives
In Table 23 we map the identified needs for solar PV to the proposed FabriGen product solution and the relevant research objective for the FabriGen project. This shows that the Objectives of the project are linked to the identified needs of the solar PV industry.
Need FabriGen solution Relevant Objectives
Accelerate uptake of solar PV Fabric structures with integrated PV that qualify for FIT payments.
Combine shading and solar power generation. Objective 8
Objective 9
Reduce the levelised cost of electricity 1(LCOE) for PV systems through:
Lower purchase costs Large area roll-to-roll fabrication using commercial printing processes
Low cost, printable electrode Objective 3
Objective 4
Objective 6
Lower installation costs Low-cost tensile structures covering large areas Direct integration of PV modules Objective 6
Objective 7
Objective 9
High-efficiency PV materials, modules and systems. PV materials development, new module designs and understanding UV downshifter enhancements Objective 1
Objective 2
Objective 5
Long-life PV materials, modules and systems. UV absorbers and down-shifters
Advanced barrier and encapsulation technologies Objective 5
Table 2. The Objectives of the project are linked to the identified needs of the solar PV industry
Benefits
Fabric-based solar generation structures have the following advantages over solid glass panels:
• Offers the opportunity to construct dual-purpose structures e.g. shades, shelters, walkways, car ports, barns, etc. therefore offsetting the cost significantly.
• Large areas can be covered at lower cost that glass panels
• Can construct complex shapes to maximise solar collection
• Lower installation costs
• Environmental benefits from manufacture, use and disposal , through non-toxic, organic materials
• Lightweight, easy and low cost to transport – very important for developing counties
• Easy to move and relocate – e.g. farmers can use fallow ground and rotate with crop cycles
• Less fragile than glass panels
• Easier to replace and redistribute for reuse
1.1. Progress Beyond the State of the Art Fabric-structures
1 The LCOE is the cost per kWh generated, including purchase, installation and maintenance costs
The materials and technology of fabric structures have been developed to the point where fabric architecture is now common in buildings and constructions in many countries – particularly to provide shade in hot climates. Fabric structures are lightweight structures that incorporate fabric membrane material, and include air-inflated, air-supported, cable net, frame-supported, geodesic dome, grid shell, tensegrity (cable-and-strut) and tensile membrane structures. The light weight of the materials makes fabric architectural construction easier and cheaper than standard building designs, especially when vast open spaces have to be covered, although fabric structures allow for projects of all scales. Fabric structures are used for sheltering large public areas, such as stadia, public transportation terminals, shopping malls and arcades, as well as smaller shades for car parking, playgrounds, schools, sports facilities, bus stops, restaurants, cafes, seating areas, office buildings and boat docks. Fabric shade sails are often used within glass buildings to provide shade from direct sunlight. In developing countries the use of fabric structures to provide shade from the sun and shelter from the wind during the day and to retain heat at night is well established. As such fabric structures offer an ideal platform for solar power generation – enabling large area coverage with low materials use and construction costs.
The idea of combining fabric structures with solar PV is not new. For example a PVC-PV tensile structure pavilion was included in a design exhibition in 19982 and a US project3 reported on the feasibility of integrating amorphous silicon PV modules into tent fabric in 2001. Only recently, however has the development of roll-to-roll production processes for flexible and efficient PV modules based on thin-film technologies made these a realistic commercial proposition.
Current solutions
PV systems can be classified as ground-based (stand-alone systems e.g. solar farms), building-applied (BAPV)
(e.g. roof mounted panels), and building-integrated (BIPV) (where PV is integrated with building function e.g roof tiles, skylights). The majority of solar PV systems in use today employ solid, flat-panel PV modules, with the PV material encapsulated in glass.
For fabric-integrated PV, lightweight and flexible thin-film PV modules are required. The alternative technologies suited to flexible PV manufacture4 include amorphous Si (a-Si), Copper Indium Gallium diSelenide (CIGS), Dye- Sensitized Solar Cell (DSSC) and Organic Photovoltaics (OPV). These are compared in Table 3.
FLEXIBLE PV a‐Si CIGS/CIS DSSC OPV
Major Manufacturers Unisolar Ascent Solar, Dyesol Konarka
Nanosolar, Sony Solarmer (R&D)
Solopower G24i
Miasole
European Flexcell Flisom AG G24i Konarka
manufacturers PVflex Solar Dyesol UK Heliatek (R&D)
CIS Solartechnik 3G Solar
Odersun SolarPrint
Solarion
Cell Efficiency [%] 5-8% 7-11% product <10% product <5% product
product 18% R&D 8% R&D
Lifetime [yrs] 25 years 10+ years expected Poor outdoor Not fully proven
expected (UV) lifetime 80% degradtion over 3 year
Typ. 100 hrs. claimed
Maturity Mature Emerging products Prototypes Emerging products
Table 3. Comparison of flexible PV technologies
The efficiency of flexible thin-film PV technologies is lower than the solid panels (crystalline silicon cell solar modules have efficiencies up to 24%, and are typically <18%). Of the flexible technologies, CIGS have recorded the highest efficiency, followed by amorphous-Si, DSSC and OPV. However raw efficiency measures are not the
whole story. First of all these are typically quoted under ‘standard’ laboratory illumination5. In real life (particularly in Northern Europe) illumination is often indirect (due to cloud cover). In these conditions low-refractive index cells (DSSC and OPV) are more effective at capturing scattered, low-angle, light. In addition CIGS cells contain Indium, which is relatively scarce and could have an impact on CIGS competitive position6. A major drawback to dye-sensitized cell technology is the electrolyte solution, which is made up of volatile organic solvents and must be carefully sealed. This, along with the fact that the solvents permeate plastics, has precluded large-scale outdoor application and integration into flexible structures. New solvent-free DSSC technologies are being developed however there is still concern over the UV degradation of dyes, which make them unsuitable for prolonged outdoor use. At present, the relatively low volume and lack of competition in flexible PV production mean that these low-costs have yet to fully materialize on the market. Unisolar quote a system price (for a large 500kW project in California) as currently 4$/W and an unsubsidized LCOE of 0.19$/kWh which is comparable to conventional c-Si panel figures. With efficiency improvements (to 12%) and manufacturing cost reductions Unisolar are targeting a system price of 2.5$/W and LCOE of 0.12$/kWh. However the Unisolar amorphous Silicon modules are not very flexible and are poor in overcast conditions. No current technologies are commercially attractive for widespread adoption in the tensile fabric market.
Fabric-structure solar PV products are beginning to emerge. For example FTL Solar Inc. (Texas, USA) use flexible thin-film CIGS PV modules from Ascent Solar (Colorado, USA) that are integrated (by attachment and lamination) to flexible composite fabrics (Figure 5). FTL Solar’s products claim to be the first and only pre- fabricated, mass-produced photovoltaic (PV) tensile structures, although as yet they have not received IEC 61646 certification. In Europe, HighTex GmbH in conjunction with SolarNext AG have developed prototype tensile membrane structures that incorporate amorphous silicon thin-film PVs from VHF-Technologies SA (Flexcell) in Switzerland (Figure 6). These are not believed to be available commercially as yet. Other PV players are developing amorphous silicon fabric PV products, including PowerFilm, Inc. As discussed above, there are limitations to non-organic PV technologies which use rare materials and/or high-cost and complex production methods e.g. high-temperature vacuum deposition methods. To date, the few actual products on fabric membranes are simple (e.g. saddle-shape) tensile sheets aimed at stand-alone systems providing off-grid local power, e.g. charging batteries in military field camps. There are still questions over the ability to fabricate more complex stretched fabric shapes (e.g. arch, wave, highpoint) due to the physical effect of, and on, the PV modules which currently are not very flexible. While these market entrants will have some success in the solar fabric market, the current cost of these products do not make a good business case for large scale use in microgeneration solar farms or for domestic use, where solid panels continue to be the best option.
Tensile fabric integration and electronics connection
An important contributor to solar cell costs are the fabrication and integration steps need to facilitate electrical connections and integrate solar modules with supporting structures – in this case the tensile fabrics. There are different types of fabric used for outdoor tensile structures, including PVC Coated Polyester, Teflon Coated Glass cloth, Silicon Glass, PTFE or ETFE, Acrylic coated cotton, Cotton Canvas, PVC on Polyester Mesh and Nylon Rip-stop. The FabriGen project coordinator, Inside2Outside is a tensile structure designer, manufacturer and suppler and has extensive knowledge of tensile materials and design issues. The project will study the suitability of different fabrics for use with PV modules, and investigate methods to integrate PV fabrication with flexible fabrics. At least initially the solar modules will be produced separately on rolls of PET or similar substrates and then combined with fabrics by lamination or other methods. However the project will investigate the potential to print layers directly on rolls of fabric or fabric multilayers. Coatema, in cooperation with Solar Integrated Technology (SIT), has previously developed production plants for the lamination of flexible solar cells. SIT is the world´s market leader for integrated solar roofs. Coatema will be the ideal partner to advise the Fabrigen project.
Tensile fabric forms are curvilinear in 3-dimensions, and the standard rectilinear format of current PV modules are unlikely to make best use of fabric area. Fraunhofer Institute for Solar Energy will look at the issues and opportunities with designing and fabricating OPV modules in complex-shaped fabric structures. This will include an investigation of module power-matching in a multi-module power generation system.
Project Results:
Individual organic photovoltaic modules were fabricated in a sheet-to-sheet process. In parallel, a roll-to-roll process for the fabrication of these modules was established. Flow charts for both processes are given in figures 1 and 2, respectively.
Fig.1: Scheme of inorganic PV modules integrated into tensile membranes, side and top view.
Fig. 2: Model of the small scale canopy with integrated hexagonal shaped organic PV modules.
Individual organic PV modules (sheet-to-sheet process)
Fig. 3: Flow chart for the integration of individual organic PV modules into tensile membranes.
Roll-to-roll production of PV modules
Fig. 4: Flow chart for the roll-to-roll fabrication of PV modules and integration into tensile membranes.
The following conclusions with scientific, technical, practical and commercial implications were derived on the basis of the experiments carried out:
- As part of the activities in WTask 2 of WP4 three organic UV-absorbing materials were obtained and tested: (i) Benzophenone-4 and its sodium salt, (ii) 4-Hydroxybenzophenone and (iii) Tinuvin 1130. All three materials are known UV-absorbers with good absorption capability in the UVA/UVB range in addition to low absorption in the visible light spectrum.
- ETFE sheets were studied and implemented as substrate material. It was established, that the front side of these sheets exhibited lower mean surface roughness with better wettability compared to the back side.
- A multitude of layers based on two kinds of polymer dispersions (U300 and C700) were deposited. The dispersions were chosen according to the target specifications of the FabriGen product in terms of cost, processability, possibility for R2R manufacture and OPV performance when attached to tensile membranes. The surface characterization showed an increase in mean roughness. It was established that deposited layers from the C700 dispersion exhibit a higher surface roughness compared to those from U300.
- The sessile drop test on deposited layers indicates a decrease in contact angle which is indicative of better wettability. This implies potential for further implementation of the deposited films in OPV devices.
- Deposited films from the C700 dispersion exhibited a higher thickness. After 6 depositions by a spring-loaded hand proofer uniformity of the thickness for both C700 and U300 films was observed.
- Electrochemical impedance spectroscopy of samples with an increasing number of deposited layers from both dispersions (U300,C700) revealed that U300 has a higher initial barrier ability and durability behavior. A densification effect of the deposited layers was detected after 5-6 deposition counts.
- Spectral absorption test revealed that the concentration of the UVA-material in the deposited layer is directly correlated with the UV-filtering capability with higher concentrations inducing better UV-absorption. However the quantity of UVA-material introduced in the film forming solution was limited to ≈6% for technical reasons.
- UV-light illumination test conducted in an inert and in uncontrolled environment revealed a strong dependence of the photodecay of the UVA-material on the presence of both oxygen and moisture. In order to ensure the longevity and UV-filtering capability of the films a good barrier protective layer with low WVTR and OTR must be present.
- It was confirmed that deposited layers containing all three UVAs showed a good absorption capacity. Tinuvin 1130-containing films showed the best results characterized by higher absorption. A feasibility study of the application of this material in polymer solutions is part of ongoing tests. The result will be important from a practical point of view.
- Further weatherability studies for all organic UVAs are underway to determine aging and photodegradation behavior.
- Photoelectrochemical behavior of samples was tested by EIS via sol-gel route. Zn and Zn-Ag containing samples exhibited a change of electrical resistance under UV-irradiation. UV-illumination of TiO2 containing samples resulted in carbonization of organic moieties. Addition of Ag led to corrosion and electrode detachment. No electrical properties were registered after high temperature treatment. Bad repeatability was observed in the results of the experiments.
- All synthesized Sm- doped boron phosphate glasses showed a strong effect of luminescence. It was concluded that Sm doped ZnO-B2O3-P2O5 glasses are reliable and effective for the goals and further success of the FabriGen project. From the experiments it can be concluded that the optimum amount of rare earth oxide in boron phosphate glass is 0.5 mole%. Increasing the concentration above this value results in a decrease of emission. This finding is important from a practical and commercial perspective.
- The effect of luminescence in Tellurite and Eu- doped glasses was lower compared to Sm- doped boron phosphate glasses. Their emission spectrum is of a similar nature but has a lower intensity. A shifting effect of the excitation peaks from the UV region to the low-wave values of the visible spectrum occurs, in comparison to Sm doped ZnO-B2O3-P2O5 glasses. They are excited by a light source with wavelengths in the visible region (between 400 – 500 nm) and exhibit emission between 500-700 nm. This behavior makes them less applicable for the requirements of the FabriGen project.
- Several tests for the application of Sm- and Eu-containing glass powders were carried out. These results were inconclusive and further tests are ongoing.
- FTIR spectroscopy study of ZnO-B2O3-P2O5-Ln2O3 (where Ln is Sm, Eu) confirms that there are two types of water molecules present in the glass structure. Closely positioned molecules of boric acid associate due to the formation of “bridge” hydrogen bonds between neighboring OH groups. Some of the OH groups remain in a free state as they do not participate in “bridge” formation. Instead they are directed inside the powder particles, and do not react with atmospheric water. Other “free” OH groups are directed to the outside and are a contributing factor for the adsorption of water molecules from the atmosphere. Moreover, C-O bond vibrations from atmospheric CO2 molecules were also detected. The other vibrations that were B-O-B identified are trigonal BO3 units and ionic B2O72- group. Furthermore, P-O-P and O-P-O vibrations from PO4 tetrahedra were identified and are increasing with respect to the increase of Sm content. A Sm+ ion is situated between the layers of the matrix. Increasing its concentration leads to an intensity increase across all bands. This intensity increase is most probably due to the contribution of more BO4 groups and O- bonds structure formation. It can be accepted that the O- ion comes from Sm2O3 and serves as a link between the building units in the glass network.
- TGA/DTA study of (ZnO)20.5(TeO2)79(Sm2O3)0.5 batch sample shows crystallization of the α-TeO2, ZnTeO3.and Zn2Te3O8 phases. For the glass sample, the crystallization of the same compounds was established at the same temperature. The glass transition temperature was observed at 321 0C. The stability analysis showed that the glass is considerably stable, but this high reflective index glass sample contains a low amount of ZnO, high TeO2 content and high price, respectively.
- DTA analysis of ZnO-B2O3-P2O5-Ln2O3 (where Ln is Sm, Eu) system shows quite a different behavior. In the batch state the samples displayed few pronounced melting peaks followed by barely visible exothermic peaks which correspond to the formation of Zn3BPO4 and ZnO:P2O5 compounds. Regarding glass samples, glass transition temperature of 509°C and a well expressed first γ-Zn2P2O7 crystallization peak, are detected. The last two thermal effects are due to melting of β- Zn2P2O7 and Zn3BPO4 compounds. The stability analysis confirmed that these high ZnO containing glasses, with low refractive index samples, are quite stable and applicable for practical applications. They could be recommended after a study of the crystallization process for a better LDC effect and future integration in OPV devices.
- It was determined that OPV devices, being complex multi layered units with many interfaces and different morphology changes present degradation problems. The encapsulation depends on the technology applied, materials used (including UVAs) and the desired OPV device properties. The optimum selection from these three fields leads to optimum device lifetime. Two new methods (optical tensiometer and adhesion tests) were set up, successfully learned and applied for surface layer characterization by single-layer deposition. Prototype multiple layered samples were investigated after effective integration of materials for a multilayered OPV device. Further UV illumination experiments are in progress. Another prototype flexible hexagonal OPV device (F-ISE origin) was created by the direct thin-film encapsulation process in an inert atmosphere. Some samples of the most recent flexible configurations of OPV devices will be the object of further UV degradation tests (WT4.3). This will be performed according to the EN 61646 standard test requirements, UV preconditioning tests (testing procedure of standards ISE 61345 & ISO 4892), and robustness of terminations test according to the standard IES60068.2:21.
Figure 5: different device configurations used to test the functionality of the PV-inks.
Prototype PV-Modules with commercial OPV materials
Fraunhofer ISE has prepared complete prototype modules using an ITO-free device stack which was developed prior to FabriGen and has a high potential for cost reduction against6 usual device stacks based on ITO. As PV-material the well-studied and commercially available Polymer P3HT in combination with PC61BM was used.
PET films Mitsubishi Hostaphan RNK 50 2CSR were mounted on glass carriers with an adhesive polymer (GelFilm). The surface of the PET film substrates were cleaned with a cleanroom paper and ethanol and blow dried with nitrogen afterwards. Prior to further processing the films were dried in vacuum for ca. 14 h. As the bottom electron contact a stack of 7.5 nm chromium, 100 nm aluminium and again 7.5 nm Chromium was evaporated at a pressure of less than 8E-6 mbar. Aluminium was evaporated thermally whereas chromium was evaporated with an electron beam source.
The photoactive layer was deposited by slot-die coating with a Coatema Easy-Coater in a sheet-to-sheet process. The coating was done with a speed of 1 m/min, a coating gap of 50 µm and a wet film thickness of 10.5 µm. After drying at room temperature these parameters resulted in a dry film thickness of 220 nm. The samples with the dried films were annealed at 80 °C for 10 min inside a glove box filled with clean nitrogen. As a coating solution a mixture of P3HT and PC61BM in o-xylene was used with a solid content of 25.5 mg per ml o-xylene. The coating solution was stirred at 90 °C for ca. 48 h prior to usage.
With a delay of ca. 18 h a PEDOT:PSS layer was coated on top the photoactive layer. The coating was done by the slot-die technique with a speed of 1 m/min, a coating gap of 50 µm and a wet film thickness of 18.2 µm resulting in a dry film thickness of 200 nm. The PEDOT:PSS films were dried at room temperature and subsequently annealed at 80 °C for 10 min inside a glove box.
The contact pads and the surrounding areas were wiped with a cleanroom paper and ethanol first to remove the PEDOT:PSS layer and with a cleanroom paper and o-xylene in a second step to remove the photoactive layer. On the edge of the solar cell elements a fine line was wiped with a mixture of ethanol and o-xylene to remove both layers in one step.
In a following step a grid and support structured (two separate masks) consisting of a 100 nm silver layer were thermally evaporated.
The modules were annealed at 120 °C for 10 min inside a glove box. On the contact pads a copper foil with a conductive adhesive was applied and the substrate film was cut in the shape of the module. The encapsulation was done entirely inside the glove box. An aluminium barrier film (supplied by CPI) was used as the back barrier. Transparent barrier films from Fraunhofer POLO or from 3M were used as the front barrier. A barrier adhesive from tesa was laminated on both back barrier and front barrier in ambient air and transferred into the glove box. With a laminator first the front barrier and subsequently the back barrier were laminated on the module after illuminating them with a UV-lamp for 1 min. In a last step the outlines of the modules were cut and holes were cut into the front barrier to contact the electrodes via the copper foil.
The modules where characterized inside a glove box. Current-voltage curves where measured in the dark and illuminated with a class C sun simulator. A mismatch factor of 1.14 was used, calculated with a small single cell with the same layer stack. The current density was derived from the current and the total active area of 60.84 cm² On each module six single cells are connected in series.
The photovoltaic performance parameters were determined from the JV-curve measured with a solar simulator, the device temperature was about 30°C, deviating slightly from standard test conditions. The charge of modules gave quite coherent performance at around1.7% efficiency, best devices approached 2%
Figure 6: diagrammatic representation of the cell-lamination concept
Figure 7: Coatema ‘click and coat’ production line
Figure 8: hand-feeding the web, leading to tension issues and ‘rolling’ of the fabric in the lamination nip
Demonstrator materials
The demonstrator was formed with a PSA stack front and back, and with a Melinex 401 top-sheet to provide mechanical protection. The Melinex 401 is not UV stable, however in work packages 3 and 4 UV stable protective materials were identified and products containing them were sourced. A UV-protecting acrylic lacquer used by the automotive industry was found in WP3 to be a suitable material for removing the UV light from visible light so this was to be applied once the panels were in place on the tensile structure.
The image in Figure 9 shows the panels with the active cells laminated onto the 1 x 1 m tensile structure. While the cells and lamination stacks initially looked very good, it was found that over time the front-sheet would start to peel away from the back-sheet due to the discrepancy between the force applied to the tensile membrane to stretch across the form and the ability of the front-sheet to conform.
This problem would later be solved in WP3 and WP6.1 where the method of laminating a PVC front-sheet to the modules allowed the front to be flexible, and then mechanically welded to the tensile fabric only at the edges of the cells, so negating any delamination effects in the middle of the panels.
Figure 9: the cells welded into the 1 m x 1 m tensile structure for out-door testing at I2O
Step Protocol
1.0 OPV Production
1.1 Back-contacts to be formed at CPI
1.2 Organic materials to be coated at F-ISE
1.3 Silver front contacts to be printed at Coatema
2.0 Encapsulation
2.1 Back-barrier preparation
2.1.1 PSA to be laminated to PET side of Al-foil laminate
2.2 Front-barrier preparation
2.2.1 PSA to be laminated to the back-side of the front-barrier
2.2.2 PSA to be laminated to the front-side of the front-barrier
2.3 Front and back laminate to be de-gassed (moisture removal)
2.4 OPV panels to be laminated onto the back-barrier
2.4.1 Electrical contact and bus-bars to be laid-up
2.4.2 Front-sheet to be laminated to the OPC cells
2.5 PVC to be laminated to the front-sheet
2.6 PVC-coated cells to be welded to the tensile fabric
3.0 Electrical contacts cut into the WVTR protection structure`
4.0 Tensile fabric with cells to the formed into tensile structure
4.1 Electrical connections made to inverters
Table 10: the production run for producing the large-area modules.
Figure 11: a short CIGS sub-module.
Figure 12: 2x short modules welded to 1.2 m wide on lime-green tensile fabric.
Figure 13: The small CIGS module on top on a 6m long, 2.4 m wide CIGS/Si module on tensile fabric.
Silicon Cell Large Area Fabrication
For the production of a module made of silicon cells, it was determined that a 6m by 1m structure would be made. This would be constructed by producing two 6m by 0.5m wide stripes containing 7 silicon solar cells each (figure 5). The cells on each stripe would be electrically connected in parallel through a 20mm wide copper tape busbar 100µm thick (figure 6). From the technical specification provide from the manufactures this should give 160W output at full sun (at 80V and approximately 2A). 30µm copper tape 9mm wide was attached at the positive and negative electrodes on the silicon cell with electrically conductive adhesive already on the copper tape, with enough material spare to attach to the busbars. During production the busbars were laid either side of the silicon cells (figure 5 & 6). Finally four stripes of 100 µm thick tinned copper tape 20mm wide were attached at either end of the busbar and folded over on themselves; this allows for flexibility of construction of final structure as external connections can be made at either end of the module.
Figure 14 Electrical connections for Si Cells
Figure 15 Copper tape electrical connections
CIGS Cell Large Area Fabrication
For the production of a module made of CIGS cells, it was determined that a 6m by 1m structure would be made, similar to that of the silicon cells. This would be constructed by producing two 6m by 0.5m wide stripes made up of 18 rows each contain 3 CIGS cells (figure 7). The 3 CIGS cells in each row are connected in series, whilst each row is connected in parallel. This should give an output of 200W (at 55.5V and 3.8A) according to the manufactures specifications. The cells in each row are connected by 30µm thick copper tape 12mm wide with the electrically conductive adhesive attached to the electrodes of the CIGS cells. The busbar also uses the same 30µm thick copper tape 12mm wide with the electrically conductive adhesive connected to the copper tape at the end of each row. Finally four stripes of 100 µm thick tinned copper tape 20mm wide were attached at either end of the busbar and folded over on themselves; this allows for flexibility of construction of final structure as external connections can be made at either end of the module.
Figure 16 Electrical connections for CIGS Cells
Figure 17 Copper tape electrical connections
Roll to roll production of OPV cells
For roll to roll production of OPV cells, it was decided that CPI would produce a reel of film with back contacts designed by the Fraunhofer ISE. This material was then coated with OPV inks at Fraunhofer ISE and the top contact added at Coatema. As with the silicon and CIGS cells a module 6m by 0.5m was made. The electrical connections were made between cells were made in parallel via busbars running either side of the structure; Due to technical limitations of the printing machine used for the silver grid deposition, i.e. a missing registration unit in web direction, it was not possible to form a series interconnection of subunits in the web direction. This resulted in the situation that the OPV module consists of 6m long cell strips and only 6 of these strips connected in series across the web width. This leads to a significant power loss for the single modules, but this issue can easily be solved by either connecting several of these elements in series or use a 2D registration system in a production line and connect several subunits in series in web direction.
Figure 18 Back contacts for OPV cells
Figure 19 Electrical connection of OPV cells
Figure 20: Reel-up of the finished back-contact film
Once the mask was removed, the material was reel-up for sending to F-ISE. Figure 21 shows part of the completed reel of material.
Figure 21: The reel of back-contact material to be shipped to F-ISE
Figure 22: the silver ink after it was cured
Figure 23: application of the Tensile PVC onto the substrate containing the cells
The image below is of the full stack; back contacts, OPV materials, front-contact and water-protection encapsulation and PVC top-sheet. There is some reticulation of the OPV coating from the areas without back-contacts; however this is insignificant because these are non-active areas of the device, see Figure 24.
Figure 24: one of the 120 mm repeats showing a set of 6 cells in series.
After the cells had completed the lamination process at Coatema they were shipped as a continuous roll to I2O where they were welded into a tensile structure. The Figures 25 and 26 show the cells laid out on the welding surface prior to construction. Fortunately the consortium partners had made an excessive number of modules for the final demonstrators as one of the modules had been shortened by an unknown party between lamination at Coatema and shipping to I2O, therefore one of the larger cells no longer had an intact water-barrier envelope.
Figure 25: some of the OPV cells at I2O pre-lamination
Figure 26: the cells as above, the ‘shortened’ one 2nd from the right
The cells were then welded onto tensile fabric to form the final demonstrator, Figure 24 shows the flexible CIGS and Si welded onto a blue tensile fabric prior to being stretched into a barrel-arch.
Figure 27: CIGS and Si cells welded onto a blue tensile fabric 6 m x 2.4 m
The active PV layer was prepared onto the final barrier layer ‘sandwich’ incorporating mechanical decoupling layers and the electrical connections on a roll to roll process at Coatema as described in deliverable 6.2
Figure 28. 6m OPV cells being prepared for high frequency bonding onto the tensile PV membrane
The final barrier layer sandwich was stretched out flat prior to bonding onto the tensile membrane, using high frequency welding techniques. Pockets were added around the membrane to allow the tensilePV membrane to be incorporated into a frame.
Figure 29. 6m TensileOPV membrane in a frame prior to tensioning.
Similar techniques were used to prepare the inorganic tensilePV membranes.
The final barrier layer sandwich was stretched out flat prior to bonding onto the tensile membrane, using high frequency welding techniques. Pockets were added around the membrane to allow the tensilePV membrane to be incorporated into a frame.
Figure 30. TensilePV CIGS membrane tensioned into Barrel arch frame.
Potential Impact:
The principle means of dissemination of the knowledge gained through the project will be through commercial exploitation.
Some parts of the findings from the project were written up and published in seven publications:
- V. Bozhilov, S. Kozhukharov, E. Bubev, M. Machkova, V. Kozhukharov, “Application of TiO2 and its derivatives for alternative energetic sources”, Proceedings of “Angel Kanchev” University of Ruse (Bulgaria), 51, (9.1) (2012), 36 – 40. Link - http://conf.uni-ruse.bg/bg/docs/cp12/9.1/9.1-6.pdf
- E. Bubev, S. Kozhukharov, V. Bozhilov, M. Machkova, V. Kozhukharov, “Employment of photosensitized TiO2 in photoelectrochemical energetic sources”, Proceedings of “Angel Kanchev” University of Ruse (Bulgaria), 51, (9.1) (2012), 69 – 73. Link - http://conf.uni-ruse.bg/bg/docs/cp12/9.1/9.1-12.pdf
- Valentin Bozhilov, E. Bubev,S. Kozhuharov, V. Kozhuharov, M. Machkova, “Barrier layers for application in organic solar cells”, Second International Conference on Materials for Energy, DECHEMA, Convention Center Karlsruhe, Germany 12-16 May 2013.
- E. Bubev, Valentin Bozhilov, S. Kozhuharov, V. Kozhuharov, M. Machkova, “UV- protection for Organic Photovoltaic Solar Cells” Second International Conference on Materials for Energy, DECHEMA, Convention Center Karlsruhe, Germany 12-16 May 2013.
- V. Bozhilov, S. Kozhukharov, E. Bubev, M. Machkova, V. Kozhukharov, „Classification and functional characterization of the basic types of photovoltaic elements“, Bulgarian Chemical Communications, v. 45, Special Edition A (269 – 273) 2013.
- E. Bubev - RES Summer school in TEI Patras, Greece ,1-12July 2012, Presentation -“DEGRADATION AND STABILITY OF ORGANIC PHOTOVOLTAIC CELLS”. Link - http://dasta.teipat.gr/system/files/moke/Degradation%20and%20Stability%20of%20Organic%20Solar%20Cells.pdf
Trade exhibitions, conferences and summer schools also benefited from the knowledge gained through the Fabrigen project:
- R.E.S. Summer school in TEI Patras, Greece , 1-12 July 2012 (Eng. E.Bubev)
- National Chemical Conference - Technical University “A. Kanchev”, Russe, Bulgaria, Nov. 2012
- International LII Annual Conference of Spanish SECV, 03 - 06 October 2012 Burgos, Spain, participation with report as invited lecturer.
- PRACE Autumn School on Massively Parallel Architectures and Molecular Simulations in The National Centre for Supercomputing Applications, 24 to 28th of September, 2012 in ,Sofia, Bulgaria.
- International Second International Conference on Materials for Energy, DECHEMA, 10-13 May 2013, Convention Center Karlsruhe, Germany).
- R.E.S. Summer school in TEI Patras, Greece ,01-12July 2013,Patras (Eng.V.Bozhilov)
- Participation of 2 PhD students from FabriGen team in "Center of mathematical modeling and computer simulation for training & development of young researchers", Project No BG051PO001-3.3.06-2014 (http://www.uctm.edu/mmcentre/) .
- Trade exhibition participation:
- “Energy Efficiency & Renewable Energy” organized from Inter Expo Center, Sofia, 28-30 March 2012; http://iec.bg/bg ;
- South-East European PV Exibition,Sofia,Bulgaria, 29-31May 2012 in parallel with South-East European Solar Ex. (SEE Solar) http://www.eeandres.viaexpo.com/en/seesolar
The principle trade exhibition was LOPEC ‘Large area Printed EleCtronics exhibition and conference (LOPEC) At Messe Munchen, Germany, on the 26th to the 28th May, 2014, during which the Fabrigen project featured on two stands – Coatema and Fraunhofer ISE and a presentation was given,
Commercial Exploitation:
Improving the competitiveness of the SME participants
Section 1 of this proposal has demonstrated that there is a fundable need for innovation to reduce the levelised Cost of Electricity (LCOE) of grid-connected PV systems and to offer innovative products to the solar energy market. FIT polices provide an opportunity for increased private sector research and development, spurring innovation and cost reductions. A recent paper highlights the opportunities for SME-led innovation in the PV energy sector, in particular by harnessing the strength of R&D and supply-chain clusters across Europe12. The domestic rooftop market is being aggressively targeted in many countries, however there is an opportunity to offer innovative PV solutions using fabric structures for public and commercial spaces e.g. for public transport companies, retail and commercial businesses, farmers, schools and local Government.
The rewards for solar PV providers will be significant: the global solar energy market is expected to reach $34 billion investment per year in 2010 and over $100 billion new investments per year by 2050. Europe, with over 65% market, holds a leading share in the global photovoltaic (PV) market in 2010. Germany with 43% share would be the world leader in PV market. Allied to this there are political mandates (including the EU2020 renewable energy targets, and SEII solar PV targets) and public demand for green policies.
The conventional solar panel market is facing PV system cost declines and global competition, with growing influence of Chinese PV module and system suppliers. The European lead in PV is under threat from the growing PV R&D and supply market power of US, Far East and China. Leading utilities and independent power producers are increasingly sourcing modules on the spot market. To address this competition, there has been a move to non-silicon and thin-film PV technologies (e.g. CdTe, CIGS and amorphous silicon thin film modules) however these only show marginal benefits, and have very similar installation requirements to conventional solar panels. This market background offers an opportunity for the SME participants in this consortium to develop a new product for the solar power market that has the potential for lower cost modules - through the use of printed OPV technology, and lower installation costs - through large-area, low-cost fabric structures.
An important benefit of the project is that the components technologies and methods developed for OPV fabrication are likely to have spin-off applications and benefits in other fields – particularly Organic Light Emitting Displays (OLEDs) and other printed electronics applications. All printed electronics devices require printed conductors, and most require barrier and encapsulation layers (in fact the barrier specifications for OLEDs are even more stringent than for OPV devices). The OLED and printed electronics markets are actually larger than the OPV market
Through this project the SMEs in the consortium will each improve their competitiveness as described below:
Inside2Outside Ltd.
Current business: Design, manufacture and supply of tensile fabric structures – primarily in the UK
Threats: Fabric structure manufacturers are facing slow growth against a background of increasing cost of raw materials and a slowdown in economic conditions. There is a continuing trend toward using fabric in building projects in place of traditional (and often more expensive and less efficient) materials such as steel and concrete, however the market is very competitive. Until the economy rebounds, the architectural building market segment is likely to be sluggish and difficult for SMEs.
New business opportunities: The FabriGen project offers Inside2Outside the opportunity to develop a new business stream in solar fabric structures and solutions that will make them highly differentiated in the market, and able to offer a product that meet the aspirations of the new economy i.e. ‘green’, sustainable and revenue- generating. As discussed FITs offer an opportunity to enter the market with products that are currently uncompetitive against fossil-fuel alternatives. This will enable Inside2Outside to establish and grow the business whilst reducing the LCOE further through lower supply and installation costs (through volume purchasing and sales) and higher efficiency modules (further research). Over time the FIT’s will reduce, however by then Inside2Outside will have a thriving business and will be reinvesting in R&D. International collaboration will enable I2O to benefit from the experience and contacts made through this project.
Coatema Coating Machinery GmbH
Current business: Coatema is manufacturer of high quality coating and laminating plants. From manufacturing product development to commissioning in the areas of textiles, paper, foil, nanotechnologies, film, solar cells, fuel cells, batteries, medical applications, glass, and single aggregates or turn-key production plants.
Threats: Coatema is a highly respected company, and has won this respect through continuous innovation and R&D. However as part of the European equipment manufacturing sector Coatema is subject to the common threats facing European manufacturers – particularly SME manufacturers – of overseas competition and a difficult industrial investment environment. To maintain their position Coatema need to look ahead to new opportunities for their coating and laminating capabilities.
New business opportunities: The Fabrigen project offers Coatema the opportunity to find a new and large market for both their coating and lamination equipment. By working with researchers at an early stage they can offer their production expertise and make sure that their own R&D matches future demands. Coatema are the ideal partner to develop a pilot-production line for the FabriGen product. This project fits well with Coatema’s other R&D activities, for example the FP7 projects Flexlas and Clean4Yield.
RTD partners
Whilst the intention is for the RTD partners to hand over IP in return for payment, this does not mean that direct monetary return is the only, or indeed the prime, motivation for the RTD performers. The RTD partners, Fraunhofer ISE, UCTM, DZP Technologies and The Centre for Process (CPI) Innovation all thrive on research activity, knowledge generation, and the exchange of ideas with peers. Maintaining their institutions at the forefront of technological development is important for their future prospects. In addition they will bring background IP which may be built on an exploited in the FabriGen and solar cell projects (in agreement with the partners). In this way the project provide the exploitation links to industry that the RTD partners need.
Fraunhofer ISE gained valuable knowledge on printing Silver on top of organic functional layers. This knowledge will be exploited by Fraunhofer to acquire new research projects. Encouraged by the good results of the project Fraunhofer has ordered a rotary screen printing unit to extend the R2R coating equipment which was used to deposit the organic functional layers. The complete R2R processing of the ITO-free organic PV modules may not be directly exploitable as a commercial product as the power conversion efficiency of those modules is yet too low but the consortium gained a sound basis for follow up projects.
Inside2outside received an Excel-tool which helps to design the circuitry of an installation which makes this process faster and helps to prevent from under- or over dimensioning circuitry (Copper lanes or cables), saving cost by guaranteeing the quantitative addition of the power output of the subunits (modules) within the PV System using a reasonable dimensioning thus cost for the circuitry.
DZP Technologies itself is a commercial SME start-up that has background IP in printed electronics technology that will be brought into the project which significantly benefited the project in terms of achieving the objectives. New knowledge gained through the project has been considerable: As a result of their participation in the Fabrigen project, DZP have decided to invest their own resources in further advancing the development of next generation PV. The company is now sponsoring an EngD student at the University of Surrey who is based in the company and continuing the research on printable hybrid PV. In this way, these is increased R&D spending, supporting innovation, training of post-graduate students, and the development of clean technologies in accordance with the EU targets for renewable energy generation;
Development of PV structures which do not make use of Indium Tin Oxide (ITO) - One of the main achievements of the project is the demonstration of flexible solar cells deposited on non-ITO substrates. This approach was adopted by DZP from the very beginning of the project, and later adopted by the other partners and incorporated into the demonstration module. This is major outcome, as this technological solution circumvents the use of ITO. The later material is not only expensive and unsustainable, but it is unsuitable for flexible electronic and opto-electronic devices due to its brittleness. Cracks are easily formed in ITO during flexible, resulting in shorting and failure of the devices. During Fabrigen, effort thus focused on using aluminium substrates and back electrodes. This material is not only cheaper, but also suitable manufacturing processes are already scaled up for the production of aluminium foils and lamination of plastic substrates. The problem with aluminium oxidation was solved at CPI and FISE by using a protective Cr layer on top of the aluminium film.
Development of hybrid PV material and processes - Most initial work in Fabrigen focused on using hybrid Copper phthalocyanine (CuPc)/TiO2 hybrid inks, as well as the analogues with ZnO. This was justified by previous promising results obtained at DZP which showed good photodiode performance of printed CuPc compositions. Hybrid inks and deposition methods were successfully developed and demonstrated by DZP. However, during Fabrigen, it was found that the CuPc based materials exhibit low conversion efficiency due to their relatively poor absorption, typically much less than 1%. This finding was confirmed not only for printed, but also for deposited films of pure CuPc. Additionally, strong degradation effects were found on light irradiation, especially from the UV part of the spectrum.
Regardless of the poor performance of the CuPc PV cells, the generated new knowledge may have strong impact on future PV technologies. Importantly, the materials and processes developed during the Fabrigen work, can be transferred to newly discovered, highly efficient materials such as organic-inorganic lead halide perovskites. Perovskite PV cells which are recently reported to exhibit efficiencies in excess of 10%, can be produced using DZP methodology by replacing the CuPc absorber with lead halide perovskite absorber, whilst retaining the TiO2 scaffold structure. The perovskite material in this case offers dramatically improved efficiency due to the broader absorption spectrum of the lead halide perovskite, and the longer diffusion length as compared to the CuPc material.
Development of silicon PV inks - Another material which was specifically developed during the Fabrigen project includes water-based silicon inks based on nano-crystalline silicon and amorphous silicon. Related deposition processes were also developed and silicon films can now be routinely printed using screen or flexographic printing at temperatures as low as 120 °. The new materials and processes are thus suitable for use on flexible plastic substrates. The silicon printed films exhibit significantly improved stability compared the CuPc analogues and deserve further detailed investigations. Given the time constrains of Fabrigen, this work was carried out only on small cells (up to 2 x 2 cm), and no scale-up development was carried out.
UCTM has developed a series of teaching tools to BSC and MSC levels as follows:
- IV characteristics measurements
- Electrochemical Impedance Spectroscopy & Cyclic voltametry
- Atomic Force Microscope
- Contact angle measurements and interpretation
- Color characteristics OPV measurements
- UV testing of organic materials
- Laboratory tests and OPV aging phenomena determination (UV, to, τ, atmosphere)
- UV-Vis spectroscopy measurements
- Thermal behavior of the materials & simultaneous TG-DTA and TG-DSC analysis
CPI has developed further knowledge of Integration of solar modules to tensile membranes; welding method combined with a separate WVTR barrier versus a single laminated stack; Patterning of overlay of cells to allow flex; Corrugated PV cells and stress-relief layer and Hexagonal PV cells and electrode patterning.
Exploitation plan and returns to the consortium partners
The outline plan for the route to market in the primary market for the FabriGen technology shows where the consortium partners are planned to benefit from their position in the supply chain. In this scenario Inside2Outside will be key license holder for the overall FabriGen technology developed in the project as they are in the prime position to exploit the results, and bring consequent benefits to the other partners. It is planned for Inside2Outside to license manufacture of the OPV modules and lamination/integration with tensile fabrics as this will require volume manufacture. Coatema will be the preferred manufacturer and supplier of specialist production machinery for the roll-to-roll fabrication and lamination of the OPV fabric and will license IP as necessary to support production. Distribution to the European and global market will need a market partner (or partners) and a large number of distributers. Companies such as SKYShades, an Australian company that focuses on the delivery of tension membrane fabrication products through a global licensed distribution network, and who are already making moves in fabric PV systems. Sky Shades is represented in Australia, South East Asia, India, North America, South Africa, South America and China.
Market size
The exploitation plan focuses on the use of TensilePV fabric solar materials for local power generation as well as grid- connected power generation. However the largest market in the short term is grid-connected applications that are eligible for FIT schemes e.g typically with a scalable size of installed system up to 5MWp. This is an area where SKYShades and others cannot yet access, due to the relatively short outdoor life of the OPV modules, and relatively high cost of alternative PV technologies. In 2008 NanoMarkets predicted that the worldwide market for OPV photovoltaics will total about $40 million in 2012 and by 2015 reach $450 million. However these figures are based on the use of OPV devices primarily for local power and battery charging in consumer devices. With the efficiency and lifetime increases planned in this project, OPV modules will be a realistic and attractive option for larger power generation schemes, and, when certified for FIT schemes, the potential market will increase hugely. For example in the SEII scenario, European PV capacity will increase from the current 26GWp to supply 12% of European electricity demand by 2020 i.e. approximately 400GWp PV capacity. If we assume that only 5% of this demand is produced by solar PV fabrics at a cost of 3€/Wp (current) falling to 1 €/Wp (2020) this gives a current European market size of €3.9billion growing to €20billion by 2020.
Inside2Outside has been working on a business plan for the UK with the distributor network. With the setting up a worldwide network dedicated to the supply and installation of tensile PV. With the added performance and lifetime expected from the Fabrigen modules, it is anticipated that two years post market introduction that FabriGen solar PV systems are supplied and installed through 125 distributors in the UK alone, each exceeding a £1,000,000 turnover with about 8% net profit i.e. a £125m turnover and £10m profit. Expanding into Europe we estimate that this could reach €1billion turnover by 2020. Thus, with a very modest market penetration, the returns are substantial. This turnover will lead to a significant increase in European economic activity and increase in employment for fabric suppliers, component suppliers, manufacturers, designers, testing and certification companies, distributers and installers. The EPIA estimated that 30 full-time equivalent (FTE) jobs are created for each MW of solar power modules produced and installed, suggesting that 600,000 jobs across the PV supply chain could be created by 2020 for solar fabric PV systems. In addition this will make a significant contribution to the European renewable energy targets and reduction in CO2 emission.
Estimated Time-to-Market and Further Development Activities
The FabriGen project has led to a prototype demonstration of fabric-integrated PV modules. In addition the fabrication processes has developed to 100cm wide web. The next stage will be to implement these processes in a pilot-production plant which will provide TensilePV fabrics for the first commercial launch of the FabriGen products. Since the aim is to use conventional printing processes and equipment as much as possible it may be possible to use an existing roll-to-roll printing production line and convert this with the specialist processes, materials and techniques needed for TensilePV manufacture. The European printing industry is under severe pressure from Far East competition, the downturn in the economy and the reduction in printed material demand, hence there is an opportunity for printers to diversify into electronic materials printing. The consortium includes Coatema Coating Machinery who are European leaders in taking processes from R&D through to turn- key production solutions. They have extensive experience in printing equipment, multi-functional coating equipment and laminating solutions, for both solvent and water-based processes.
Figure 16. Coatema design and manufacture turn-key roll-to-roll coating and lamination machinery, such as the system here.
Given sufficient support and funding, we estimate a time to market post-project of 12 -18 months for the first mass-produced FabriGen PV fabrics, although smaller manufacturing quantities will be produced in this period for full certification and extended lifetime testing, and for marketing purposes.
European Community/ Societal Impact
As discussed in Section 1, if Europe is to meet the ambitious 2020 targets for renewable energy then there needs to be dramatic acceleration of installed PV systems. Without action the threat of climate change and rising global temperatures are likely to have severe economic and social consequences. The European community will not be isolated from these issues, as economic trade, food production, resource scarcities all have global repercussions. Current PV technologies, if adopted more widely, will have a large part to play in providing the PV capacity needed, however there is no doubt that new innovations are needed in order to allow PV to compete without subsidy, and as shown the market potential is huge. As usual, however, it is likely to be the poorest countries who will suffer the most from climate change, as crops fail and severe weather events ruin economies and lives. The potential for low cost, easily-transported OPV fabric-based local power for lighting, irrigation, communications and entertainment etc., could have a dramatic effect on lives in what are known as ‘resource-poor’ countries. Many of these same countries have a high solar resource, which could transform their economies if it can be captured and converted to useful energy.
For purchasers of the system there are substantial returns to be made from the investment, which may lead to offers of free installation in return for FIT payments (which is already happening in the solar industry). Alternatively this could lead to income generation for landowners and property holders. For example there is an opportunity to target farmers who could construct fabric PV structures as dual-use structures, e.g. for storage of crops, animal shelters etc, or who could use fallow or set-aside land as areas to construct fabric solar farms. This has the advantage over conventional panels that it would be cheaper to install and relatively easy to move fabric structures. Table below shows the potential costs and return from a farm building roof covered with FabriGen solar PV fabric, with a Wp of100W/m2 over a 20-year period, using current UK FIT rates. A payback period of 6 years, with potential returns many times the initial investment will provide a high incentive to invest in the FabriGen technology.
Roof space 500 m2
Installed cost £126.00 per m2
CO2 production 0.435 tonnes per MWh
Feed-in tariff (guaranteed 20 years) £0.1238 per kWh
Peak power for installation 49,060 Wp
Cost of electricity £0.10 per kWh
Electricity cost inflation 6% per annum
Output 850 kWh per kW installed
Annual output 41,700 kWh
Initial Cost of installation £63,000
Payback period (incl capital allowances) 6 Years
Net value of project (net profit) £330,108 Over 20 years
Table 11. Example installation of a TensilePV system for a farm building project, showing a net profit of
£0.33 million pounds over 20 years, with today’s level of Feed-in-Tariffs in the UK, for an initial investment of
£60k.
Justification of Trans-national Approach
Whilst Germany dominates the solar PV market in Europe, and a high number of the leading research, development and production enterprises, there is a need for higher PV adoption in other countries in the EU. Already the FIT tariffs are being reduced in Germany, while other countries are introducing generous tariffs. Any exploitation therefore needs to be flexible and transnational with regard to market. The project makes use of this leading expertise in Germany and allies this with expertise from other countries to provide both a wide research expertise and a transnational exploitation opportunity.
Robert Carpenter, Inside2Outside Ltd. (+44) 1480 409297
Robert.carpenter@inside2outside.co.uk.
FabriGen addresses the need to bring innovative products to the solar energy market to achieve the ambitious European targets for renewable energy generation. The FabriGen project aims to combine photovoltaic materials, both organic (OPV) and inorganic (CIGS and aSi) with tensile fabrics to enable the construction of solar-power generating fabric structures (TensilePV). These structures could be connected to the grid, or used for distributed power generation, and will enable generators to participate in Feed-In-Tariff (FIT) and other governmental incentive schemes that are being offered to promote the uptake of renewable energy technologies. Fabric-based TensilePV systems will reduce the cost of solar power towards that of conventional power (grid-parity) and so ultimately will not be reliant on governmental incentive schemes.
Product concept
The FabriGen product is a tensile membrane material that incorporates PV modules that can be used in a large variety of tensile membrane structures to generate electrical power directly from sunlight. The FabriGen structures are used for off-grid local power, or on-grid to offset, or feed power into national grids.
Project plan outline
The FabriGen project will implement commercial roll-to-roll printing technologies to deposit and pattern state-of-the-art PV materials and produce large-area PV modules (20 cm in research, scaling up to 100 cm roll width). Means to integrate the PV fabrication processes with polyester fabric membranes is being developed. A key aspect of the research is the development and integration of barrier and encapsulation layers to provide long-life performance needed for outdoor use (preventing water and oxygen permeation and blocking UV radiation). The use of innovative materials is being used to give enhanced UV response and improved resistance to UV degradation. The completed modules will be designed to meet EN61646 to prepare for micro-generation certification and exploitation in the market.
Benefits
• Dual-purpose structures e.g. shades, shelters, walkways, car ports, barns, thus offsetting the cost significantly
• Large areas can be covered at lower cost that glass panels
• Complex shapes to maximise solar collection
• Lower installation costs
• Lightweight, easy and low cost to transport
• Easy to move and relocate – e.g. farmers can use fallow ground and rotate with crop cycles
• Easier to replace and redistribute for re-use.
Target specifications and successes
• Cell efficiency: >10% - Achieved, with TensileCIGS.
• Module efficiency: >7% - Achieved, with TensileCIGS.
• Cost per Watt: <1 €/Wp – Achieved a roadmap towards this
• Power generation
• capacity (1 sun): >70 W/m2 - Achieved, with TensileCIGS
• Lifetime: >20 years – Achieved, by demonstrating successful integration of existing technologies into within tensile membranes.
• Levelised cost of electricity: <0.1€/kWh – is achievable with Fabrigen 2 and a productive manufacturing process.
•
Project Achievements
We have successfully built demonstrator units incorporating three different PV technologies.
These units are TensilePV membrane structures, each 6m long, by up to 3m wide and either meet the target specifications, or – in terms of production costs - demonstrate a clear roadmap to achieving the target specifications.
Project Context and Objectives:
The project: Fabric Structures for Solar Power Generation (FabriGen), addresses the need to bring innovative products to the solar energy market to achieve the ambitious European targets for renewable energy generation. The FabriGen project aims to combine organic photovoltaic (OPV) materials with tensile fabrics to enable the construction of solar-power generating fabric structures. These structures could be connected to the grid, or used for distributed power generation, and will enable generators to participate in Feed-In-Tariff (FIT) schemes that are being offered to promote the uptake of renewable energy technologies. Fabric-based OPV systems will reduce the cost of solar power towards that of conventional power (grid-parity) and so ultimately will not be reliant on FIT schemes.
The FabriGen project will implement commercial roll-to-roll printing technologies to deposit and pattern state-of- the-art PV materials and produce large-area PV modules (20cm in research, scaling up to 100cm roll width). Means to integrate the PV fabrication processes with polyester fabric membranes will be developed. A key aspect of the research will be development and integration of barrier and encapsulation layers to provide long-life performance needed for outdoor use (preventing water and oxygen permeation and blocking UV radiation). The use of innovative materials to give enhanced UV response and improved resistance to UV degradation will be researched. Compliance testing to EN61646 will be carried out on fabricated PV modules to prepare for microgeneration certification and exploitation in the market.
FabriGen product concept
The FabriGen product is a tensile membrane material that incorporates photovoltaic (PV) modules that can be used in a large variety of tensile membrane structures to generate electrical power directly from sunlight (Figure 1). The FabriGen product will be compliant with European and international standards and regulations regarding Feed-In-Tariff (FIT) schemes. This means that whether the FabriGen structures are used
for off-grid local power, or on-grid to offset, or feed power into national grids, the power generated will qualify for FIT payments, and so provide operators of the FabriGen product with an on-going revenue stream that will provide a return-on-investment.
Figure 1. In the FabriGen concept, flexible organic photovoltaic (OPV) solar cells are integrated with fabrics to enable the cost- effective production of clean, green electricity in tensile structures.
Table 1. Target specification for the FabriGen product
Table 1 lists the target specification for the FabriGen product. Achieving these figures in a flexible solar fabric would transform the solar energy market. There is nothing on the market today that achieves these specifications. Research and development are required to combine emerging research on OPV materials with large area printing technologies and develop cost-effective means to integrate solar cells with tensile membranes. The aim is to develop a new capability that can be rapidly productionised and taken to the market. In the short-to-medium term, feed-in-tariffs (currently 0.3-0.5 €/kWh in many European countries) mean that
there is significant incentive to invest in solar PV technologies with an interim performance specification, which can gradually increase towards the target listed in Table 1.
Appropriateness of the FabriGen project and objectives
In Table 23 we map the identified needs for solar PV to the proposed FabriGen product solution and the relevant research objective for the FabriGen project. This shows that the Objectives of the project are linked to the identified needs of the solar PV industry.
Need FabriGen solution Relevant Objectives
Accelerate uptake of solar PV Fabric structures with integrated PV that qualify for FIT payments.
Combine shading and solar power generation. Objective 8
Objective 9
Reduce the levelised cost of electricity 1(LCOE) for PV systems through:
Lower purchase costs Large area roll-to-roll fabrication using commercial printing processes
Low cost, printable electrode Objective 3
Objective 4
Objective 6
Lower installation costs Low-cost tensile structures covering large areas Direct integration of PV modules Objective 6
Objective 7
Objective 9
High-efficiency PV materials, modules and systems. PV materials development, new module designs and understanding UV downshifter enhancements Objective 1
Objective 2
Objective 5
Long-life PV materials, modules and systems. UV absorbers and down-shifters
Advanced barrier and encapsulation technologies Objective 5
Table 2. The Objectives of the project are linked to the identified needs of the solar PV industry
Benefits
Fabric-based solar generation structures have the following advantages over solid glass panels:
• Offers the opportunity to construct dual-purpose structures e.g. shades, shelters, walkways, car ports, barns, etc. therefore offsetting the cost significantly.
• Large areas can be covered at lower cost that glass panels
• Can construct complex shapes to maximise solar collection
• Lower installation costs
• Environmental benefits from manufacture, use and disposal , through non-toxic, organic materials
• Lightweight, easy and low cost to transport – very important for developing counties
• Easy to move and relocate – e.g. farmers can use fallow ground and rotate with crop cycles
• Less fragile than glass panels
• Easier to replace and redistribute for reuse
1.1. Progress Beyond the State of the Art Fabric-structures
1 The LCOE is the cost per kWh generated, including purchase, installation and maintenance costs
The materials and technology of fabric structures have been developed to the point where fabric architecture is now common in buildings and constructions in many countries – particularly to provide shade in hot climates. Fabric structures are lightweight structures that incorporate fabric membrane material, and include air-inflated, air-supported, cable net, frame-supported, geodesic dome, grid shell, tensegrity (cable-and-strut) and tensile membrane structures. The light weight of the materials makes fabric architectural construction easier and cheaper than standard building designs, especially when vast open spaces have to be covered, although fabric structures allow for projects of all scales. Fabric structures are used for sheltering large public areas, such as stadia, public transportation terminals, shopping malls and arcades, as well as smaller shades for car parking, playgrounds, schools, sports facilities, bus stops, restaurants, cafes, seating areas, office buildings and boat docks. Fabric shade sails are often used within glass buildings to provide shade from direct sunlight. In developing countries the use of fabric structures to provide shade from the sun and shelter from the wind during the day and to retain heat at night is well established. As such fabric structures offer an ideal platform for solar power generation – enabling large area coverage with low materials use and construction costs.
The idea of combining fabric structures with solar PV is not new. For example a PVC-PV tensile structure pavilion was included in a design exhibition in 19982 and a US project3 reported on the feasibility of integrating amorphous silicon PV modules into tent fabric in 2001. Only recently, however has the development of roll-to-roll production processes for flexible and efficient PV modules based on thin-film technologies made these a realistic commercial proposition.
Current solutions
PV systems can be classified as ground-based (stand-alone systems e.g. solar farms), building-applied (BAPV)
(e.g. roof mounted panels), and building-integrated (BIPV) (where PV is integrated with building function e.g roof tiles, skylights). The majority of solar PV systems in use today employ solid, flat-panel PV modules, with the PV material encapsulated in glass.
For fabric-integrated PV, lightweight and flexible thin-film PV modules are required. The alternative technologies suited to flexible PV manufacture4 include amorphous Si (a-Si), Copper Indium Gallium diSelenide (CIGS), Dye- Sensitized Solar Cell (DSSC) and Organic Photovoltaics (OPV). These are compared in Table 3.
FLEXIBLE PV a‐Si CIGS/CIS DSSC OPV
Major Manufacturers Unisolar Ascent Solar, Dyesol Konarka
Nanosolar, Sony Solarmer (R&D)
Solopower G24i
Miasole
European Flexcell Flisom AG G24i Konarka
manufacturers PVflex Solar Dyesol UK Heliatek (R&D)
CIS Solartechnik 3G Solar
Odersun SolarPrint
Solarion
Cell Efficiency [%] 5-8% 7-11% product <10% product <5% product
product 18% R&D 8% R&D
Lifetime [yrs] 25 years 10+ years expected Poor outdoor Not fully proven
expected (UV) lifetime 80% degradtion over 3 year
Typ. 100 hrs. claimed
Maturity Mature Emerging products Prototypes Emerging products
Table 3. Comparison of flexible PV technologies
The efficiency of flexible thin-film PV technologies is lower than the solid panels (crystalline silicon cell solar modules have efficiencies up to 24%, and are typically <18%). Of the flexible technologies, CIGS have recorded the highest efficiency, followed by amorphous-Si, DSSC and OPV. However raw efficiency measures are not the
whole story. First of all these are typically quoted under ‘standard’ laboratory illumination5. In real life (particularly in Northern Europe) illumination is often indirect (due to cloud cover). In these conditions low-refractive index cells (DSSC and OPV) are more effective at capturing scattered, low-angle, light. In addition CIGS cells contain Indium, which is relatively scarce and could have an impact on CIGS competitive position6. A major drawback to dye-sensitized cell technology is the electrolyte solution, which is made up of volatile organic solvents and must be carefully sealed. This, along with the fact that the solvents permeate plastics, has precluded large-scale outdoor application and integration into flexible structures. New solvent-free DSSC technologies are being developed however there is still concern over the UV degradation of dyes, which make them unsuitable for prolonged outdoor use. At present, the relatively low volume and lack of competition in flexible PV production mean that these low-costs have yet to fully materialize on the market. Unisolar quote a system price (for a large 500kW project in California) as currently 4$/W and an unsubsidized LCOE of 0.19$/kWh which is comparable to conventional c-Si panel figures. With efficiency improvements (to 12%) and manufacturing cost reductions Unisolar are targeting a system price of 2.5$/W and LCOE of 0.12$/kWh. However the Unisolar amorphous Silicon modules are not very flexible and are poor in overcast conditions. No current technologies are commercially attractive for widespread adoption in the tensile fabric market.
Fabric-structure solar PV products are beginning to emerge. For example FTL Solar Inc. (Texas, USA) use flexible thin-film CIGS PV modules from Ascent Solar (Colorado, USA) that are integrated (by attachment and lamination) to flexible composite fabrics (Figure 5). FTL Solar’s products claim to be the first and only pre- fabricated, mass-produced photovoltaic (PV) tensile structures, although as yet they have not received IEC 61646 certification. In Europe, HighTex GmbH in conjunction with SolarNext AG have developed prototype tensile membrane structures that incorporate amorphous silicon thin-film PVs from VHF-Technologies SA (Flexcell) in Switzerland (Figure 6). These are not believed to be available commercially as yet. Other PV players are developing amorphous silicon fabric PV products, including PowerFilm, Inc. As discussed above, there are limitations to non-organic PV technologies which use rare materials and/or high-cost and complex production methods e.g. high-temperature vacuum deposition methods. To date, the few actual products on fabric membranes are simple (e.g. saddle-shape) tensile sheets aimed at stand-alone systems providing off-grid local power, e.g. charging batteries in military field camps. There are still questions over the ability to fabricate more complex stretched fabric shapes (e.g. arch, wave, highpoint) due to the physical effect of, and on, the PV modules which currently are not very flexible. While these market entrants will have some success in the solar fabric market, the current cost of these products do not make a good business case for large scale use in microgeneration solar farms or for domestic use, where solid panels continue to be the best option.
Tensile fabric integration and electronics connection
An important contributor to solar cell costs are the fabrication and integration steps need to facilitate electrical connections and integrate solar modules with supporting structures – in this case the tensile fabrics. There are different types of fabric used for outdoor tensile structures, including PVC Coated Polyester, Teflon Coated Glass cloth, Silicon Glass, PTFE or ETFE, Acrylic coated cotton, Cotton Canvas, PVC on Polyester Mesh and Nylon Rip-stop. The FabriGen project coordinator, Inside2Outside is a tensile structure designer, manufacturer and suppler and has extensive knowledge of tensile materials and design issues. The project will study the suitability of different fabrics for use with PV modules, and investigate methods to integrate PV fabrication with flexible fabrics. At least initially the solar modules will be produced separately on rolls of PET or similar substrates and then combined with fabrics by lamination or other methods. However the project will investigate the potential to print layers directly on rolls of fabric or fabric multilayers. Coatema, in cooperation with Solar Integrated Technology (SIT), has previously developed production plants for the lamination of flexible solar cells. SIT is the world´s market leader for integrated solar roofs. Coatema will be the ideal partner to advise the Fabrigen project.
Tensile fabric forms are curvilinear in 3-dimensions, and the standard rectilinear format of current PV modules are unlikely to make best use of fabric area. Fraunhofer Institute for Solar Energy will look at the issues and opportunities with designing and fabricating OPV modules in complex-shaped fabric structures. This will include an investigation of module power-matching in a multi-module power generation system.
Project Results:
Individual organic photovoltaic modules were fabricated in a sheet-to-sheet process. In parallel, a roll-to-roll process for the fabrication of these modules was established. Flow charts for both processes are given in figures 1 and 2, respectively.
Fig.1: Scheme of inorganic PV modules integrated into tensile membranes, side and top view.
Fig. 2: Model of the small scale canopy with integrated hexagonal shaped organic PV modules.
Individual organic PV modules (sheet-to-sheet process)
Fig. 3: Flow chart for the integration of individual organic PV modules into tensile membranes.
Roll-to-roll production of PV modules
Fig. 4: Flow chart for the roll-to-roll fabrication of PV modules and integration into tensile membranes.
The following conclusions with scientific, technical, practical and commercial implications were derived on the basis of the experiments carried out:
- As part of the activities in WTask 2 of WP4 three organic UV-absorbing materials were obtained and tested: (i) Benzophenone-4 and its sodium salt, (ii) 4-Hydroxybenzophenone and (iii) Tinuvin 1130. All three materials are known UV-absorbers with good absorption capability in the UVA/UVB range in addition to low absorption in the visible light spectrum.
- ETFE sheets were studied and implemented as substrate material. It was established, that the front side of these sheets exhibited lower mean surface roughness with better wettability compared to the back side.
- A multitude of layers based on two kinds of polymer dispersions (U300 and C700) were deposited. The dispersions were chosen according to the target specifications of the FabriGen product in terms of cost, processability, possibility for R2R manufacture and OPV performance when attached to tensile membranes. The surface characterization showed an increase in mean roughness. It was established that deposited layers from the C700 dispersion exhibit a higher surface roughness compared to those from U300.
- The sessile drop test on deposited layers indicates a decrease in contact angle which is indicative of better wettability. This implies potential for further implementation of the deposited films in OPV devices.
- Deposited films from the C700 dispersion exhibited a higher thickness. After 6 depositions by a spring-loaded hand proofer uniformity of the thickness for both C700 and U300 films was observed.
- Electrochemical impedance spectroscopy of samples with an increasing number of deposited layers from both dispersions (U300,C700) revealed that U300 has a higher initial barrier ability and durability behavior. A densification effect of the deposited layers was detected after 5-6 deposition counts.
- Spectral absorption test revealed that the concentration of the UVA-material in the deposited layer is directly correlated with the UV-filtering capability with higher concentrations inducing better UV-absorption. However the quantity of UVA-material introduced in the film forming solution was limited to ≈6% for technical reasons.
- UV-light illumination test conducted in an inert and in uncontrolled environment revealed a strong dependence of the photodecay of the UVA-material on the presence of both oxygen and moisture. In order to ensure the longevity and UV-filtering capability of the films a good barrier protective layer with low WVTR and OTR must be present.
- It was confirmed that deposited layers containing all three UVAs showed a good absorption capacity. Tinuvin 1130-containing films showed the best results characterized by higher absorption. A feasibility study of the application of this material in polymer solutions is part of ongoing tests. The result will be important from a practical point of view.
- Further weatherability studies for all organic UVAs are underway to determine aging and photodegradation behavior.
- Photoelectrochemical behavior of samples was tested by EIS via sol-gel route. Zn and Zn-Ag containing samples exhibited a change of electrical resistance under UV-irradiation. UV-illumination of TiO2 containing samples resulted in carbonization of organic moieties. Addition of Ag led to corrosion and electrode detachment. No electrical properties were registered after high temperature treatment. Bad repeatability was observed in the results of the experiments.
- All synthesized Sm- doped boron phosphate glasses showed a strong effect of luminescence. It was concluded that Sm doped ZnO-B2O3-P2O5 glasses are reliable and effective for the goals and further success of the FabriGen project. From the experiments it can be concluded that the optimum amount of rare earth oxide in boron phosphate glass is 0.5 mole%. Increasing the concentration above this value results in a decrease of emission. This finding is important from a practical and commercial perspective.
- The effect of luminescence in Tellurite and Eu- doped glasses was lower compared to Sm- doped boron phosphate glasses. Their emission spectrum is of a similar nature but has a lower intensity. A shifting effect of the excitation peaks from the UV region to the low-wave values of the visible spectrum occurs, in comparison to Sm doped ZnO-B2O3-P2O5 glasses. They are excited by a light source with wavelengths in the visible region (between 400 – 500 nm) and exhibit emission between 500-700 nm. This behavior makes them less applicable for the requirements of the FabriGen project.
- Several tests for the application of Sm- and Eu-containing glass powders were carried out. These results were inconclusive and further tests are ongoing.
- FTIR spectroscopy study of ZnO-B2O3-P2O5-Ln2O3 (where Ln is Sm, Eu) confirms that there are two types of water molecules present in the glass structure. Closely positioned molecules of boric acid associate due to the formation of “bridge” hydrogen bonds between neighboring OH groups. Some of the OH groups remain in a free state as they do not participate in “bridge” formation. Instead they are directed inside the powder particles, and do not react with atmospheric water. Other “free” OH groups are directed to the outside and are a contributing factor for the adsorption of water molecules from the atmosphere. Moreover, C-O bond vibrations from atmospheric CO2 molecules were also detected. The other vibrations that were B-O-B identified are trigonal BO3 units and ionic B2O72- group. Furthermore, P-O-P and O-P-O vibrations from PO4 tetrahedra were identified and are increasing with respect to the increase of Sm content. A Sm+ ion is situated between the layers of the matrix. Increasing its concentration leads to an intensity increase across all bands. This intensity increase is most probably due to the contribution of more BO4 groups and O- bonds structure formation. It can be accepted that the O- ion comes from Sm2O3 and serves as a link between the building units in the glass network.
- TGA/DTA study of (ZnO)20.5(TeO2)79(Sm2O3)0.5 batch sample shows crystallization of the α-TeO2, ZnTeO3.and Zn2Te3O8 phases. For the glass sample, the crystallization of the same compounds was established at the same temperature. The glass transition temperature was observed at 321 0C. The stability analysis showed that the glass is considerably stable, but this high reflective index glass sample contains a low amount of ZnO, high TeO2 content and high price, respectively.
- DTA analysis of ZnO-B2O3-P2O5-Ln2O3 (where Ln is Sm, Eu) system shows quite a different behavior. In the batch state the samples displayed few pronounced melting peaks followed by barely visible exothermic peaks which correspond to the formation of Zn3BPO4 and ZnO:P2O5 compounds. Regarding glass samples, glass transition temperature of 509°C and a well expressed first γ-Zn2P2O7 crystallization peak, are detected. The last two thermal effects are due to melting of β- Zn2P2O7 and Zn3BPO4 compounds. The stability analysis confirmed that these high ZnO containing glasses, with low refractive index samples, are quite stable and applicable for practical applications. They could be recommended after a study of the crystallization process for a better LDC effect and future integration in OPV devices.
- It was determined that OPV devices, being complex multi layered units with many interfaces and different morphology changes present degradation problems. The encapsulation depends on the technology applied, materials used (including UVAs) and the desired OPV device properties. The optimum selection from these three fields leads to optimum device lifetime. Two new methods (optical tensiometer and adhesion tests) were set up, successfully learned and applied for surface layer characterization by single-layer deposition. Prototype multiple layered samples were investigated after effective integration of materials for a multilayered OPV device. Further UV illumination experiments are in progress. Another prototype flexible hexagonal OPV device (F-ISE origin) was created by the direct thin-film encapsulation process in an inert atmosphere. Some samples of the most recent flexible configurations of OPV devices will be the object of further UV degradation tests (WT4.3). This will be performed according to the EN 61646 standard test requirements, UV preconditioning tests (testing procedure of standards ISE 61345 & ISO 4892), and robustness of terminations test according to the standard IES60068.2:21.
Figure 5: different device configurations used to test the functionality of the PV-inks.
Prototype PV-Modules with commercial OPV materials
Fraunhofer ISE has prepared complete prototype modules using an ITO-free device stack which was developed prior to FabriGen and has a high potential for cost reduction against6 usual device stacks based on ITO. As PV-material the well-studied and commercially available Polymer P3HT in combination with PC61BM was used.
PET films Mitsubishi Hostaphan RNK 50 2CSR were mounted on glass carriers with an adhesive polymer (GelFilm). The surface of the PET film substrates were cleaned with a cleanroom paper and ethanol and blow dried with nitrogen afterwards. Prior to further processing the films were dried in vacuum for ca. 14 h. As the bottom electron contact a stack of 7.5 nm chromium, 100 nm aluminium and again 7.5 nm Chromium was evaporated at a pressure of less than 8E-6 mbar. Aluminium was evaporated thermally whereas chromium was evaporated with an electron beam source.
The photoactive layer was deposited by slot-die coating with a Coatema Easy-Coater in a sheet-to-sheet process. The coating was done with a speed of 1 m/min, a coating gap of 50 µm and a wet film thickness of 10.5 µm. After drying at room temperature these parameters resulted in a dry film thickness of 220 nm. The samples with the dried films were annealed at 80 °C for 10 min inside a glove box filled with clean nitrogen. As a coating solution a mixture of P3HT and PC61BM in o-xylene was used with a solid content of 25.5 mg per ml o-xylene. The coating solution was stirred at 90 °C for ca. 48 h prior to usage.
With a delay of ca. 18 h a PEDOT:PSS layer was coated on top the photoactive layer. The coating was done by the slot-die technique with a speed of 1 m/min, a coating gap of 50 µm and a wet film thickness of 18.2 µm resulting in a dry film thickness of 200 nm. The PEDOT:PSS films were dried at room temperature and subsequently annealed at 80 °C for 10 min inside a glove box.
The contact pads and the surrounding areas were wiped with a cleanroom paper and ethanol first to remove the PEDOT:PSS layer and with a cleanroom paper and o-xylene in a second step to remove the photoactive layer. On the edge of the solar cell elements a fine line was wiped with a mixture of ethanol and o-xylene to remove both layers in one step.
In a following step a grid and support structured (two separate masks) consisting of a 100 nm silver layer were thermally evaporated.
The modules were annealed at 120 °C for 10 min inside a glove box. On the contact pads a copper foil with a conductive adhesive was applied and the substrate film was cut in the shape of the module. The encapsulation was done entirely inside the glove box. An aluminium barrier film (supplied by CPI) was used as the back barrier. Transparent barrier films from Fraunhofer POLO or from 3M were used as the front barrier. A barrier adhesive from tesa was laminated on both back barrier and front barrier in ambient air and transferred into the glove box. With a laminator first the front barrier and subsequently the back barrier were laminated on the module after illuminating them with a UV-lamp for 1 min. In a last step the outlines of the modules were cut and holes were cut into the front barrier to contact the electrodes via the copper foil.
The modules where characterized inside a glove box. Current-voltage curves where measured in the dark and illuminated with a class C sun simulator. A mismatch factor of 1.14 was used, calculated with a small single cell with the same layer stack. The current density was derived from the current and the total active area of 60.84 cm² On each module six single cells are connected in series.
The photovoltaic performance parameters were determined from the JV-curve measured with a solar simulator, the device temperature was about 30°C, deviating slightly from standard test conditions. The charge of modules gave quite coherent performance at around1.7% efficiency, best devices approached 2%
Figure 6: diagrammatic representation of the cell-lamination concept
Figure 7: Coatema ‘click and coat’ production line
Figure 8: hand-feeding the web, leading to tension issues and ‘rolling’ of the fabric in the lamination nip
Demonstrator materials
The demonstrator was formed with a PSA stack front and back, and with a Melinex 401 top-sheet to provide mechanical protection. The Melinex 401 is not UV stable, however in work packages 3 and 4 UV stable protective materials were identified and products containing them were sourced. A UV-protecting acrylic lacquer used by the automotive industry was found in WP3 to be a suitable material for removing the UV light from visible light so this was to be applied once the panels were in place on the tensile structure.
The image in Figure 9 shows the panels with the active cells laminated onto the 1 x 1 m tensile structure. While the cells and lamination stacks initially looked very good, it was found that over time the front-sheet would start to peel away from the back-sheet due to the discrepancy between the force applied to the tensile membrane to stretch across the form and the ability of the front-sheet to conform.
This problem would later be solved in WP3 and WP6.1 where the method of laminating a PVC front-sheet to the modules allowed the front to be flexible, and then mechanically welded to the tensile fabric only at the edges of the cells, so negating any delamination effects in the middle of the panels.
Figure 9: the cells welded into the 1 m x 1 m tensile structure for out-door testing at I2O
Step Protocol
1.0 OPV Production
1.1 Back-contacts to be formed at CPI
1.2 Organic materials to be coated at F-ISE
1.3 Silver front contacts to be printed at Coatema
2.0 Encapsulation
2.1 Back-barrier preparation
2.1.1 PSA to be laminated to PET side of Al-foil laminate
2.2 Front-barrier preparation
2.2.1 PSA to be laminated to the back-side of the front-barrier
2.2.2 PSA to be laminated to the front-side of the front-barrier
2.3 Front and back laminate to be de-gassed (moisture removal)
2.4 OPV panels to be laminated onto the back-barrier
2.4.1 Electrical contact and bus-bars to be laid-up
2.4.2 Front-sheet to be laminated to the OPC cells
2.5 PVC to be laminated to the front-sheet
2.6 PVC-coated cells to be welded to the tensile fabric
3.0 Electrical contacts cut into the WVTR protection structure`
4.0 Tensile fabric with cells to the formed into tensile structure
4.1 Electrical connections made to inverters
Table 10: the production run for producing the large-area modules.
Figure 11: a short CIGS sub-module.
Figure 12: 2x short modules welded to 1.2 m wide on lime-green tensile fabric.
Figure 13: The small CIGS module on top on a 6m long, 2.4 m wide CIGS/Si module on tensile fabric.
Silicon Cell Large Area Fabrication
For the production of a module made of silicon cells, it was determined that a 6m by 1m structure would be made. This would be constructed by producing two 6m by 0.5m wide stripes containing 7 silicon solar cells each (figure 5). The cells on each stripe would be electrically connected in parallel through a 20mm wide copper tape busbar 100µm thick (figure 6). From the technical specification provide from the manufactures this should give 160W output at full sun (at 80V and approximately 2A). 30µm copper tape 9mm wide was attached at the positive and negative electrodes on the silicon cell with electrically conductive adhesive already on the copper tape, with enough material spare to attach to the busbars. During production the busbars were laid either side of the silicon cells (figure 5 & 6). Finally four stripes of 100 µm thick tinned copper tape 20mm wide were attached at either end of the busbar and folded over on themselves; this allows for flexibility of construction of final structure as external connections can be made at either end of the module.
Figure 14 Electrical connections for Si Cells
Figure 15 Copper tape electrical connections
CIGS Cell Large Area Fabrication
For the production of a module made of CIGS cells, it was determined that a 6m by 1m structure would be made, similar to that of the silicon cells. This would be constructed by producing two 6m by 0.5m wide stripes made up of 18 rows each contain 3 CIGS cells (figure 7). The 3 CIGS cells in each row are connected in series, whilst each row is connected in parallel. This should give an output of 200W (at 55.5V and 3.8A) according to the manufactures specifications. The cells in each row are connected by 30µm thick copper tape 12mm wide with the electrically conductive adhesive attached to the electrodes of the CIGS cells. The busbar also uses the same 30µm thick copper tape 12mm wide with the electrically conductive adhesive connected to the copper tape at the end of each row. Finally four stripes of 100 µm thick tinned copper tape 20mm wide were attached at either end of the busbar and folded over on themselves; this allows for flexibility of construction of final structure as external connections can be made at either end of the module.
Figure 16 Electrical connections for CIGS Cells
Figure 17 Copper tape electrical connections
Roll to roll production of OPV cells
For roll to roll production of OPV cells, it was decided that CPI would produce a reel of film with back contacts designed by the Fraunhofer ISE. This material was then coated with OPV inks at Fraunhofer ISE and the top contact added at Coatema. As with the silicon and CIGS cells a module 6m by 0.5m was made. The electrical connections were made between cells were made in parallel via busbars running either side of the structure; Due to technical limitations of the printing machine used for the silver grid deposition, i.e. a missing registration unit in web direction, it was not possible to form a series interconnection of subunits in the web direction. This resulted in the situation that the OPV module consists of 6m long cell strips and only 6 of these strips connected in series across the web width. This leads to a significant power loss for the single modules, but this issue can easily be solved by either connecting several of these elements in series or use a 2D registration system in a production line and connect several subunits in series in web direction.
Figure 18 Back contacts for OPV cells
Figure 19 Electrical connection of OPV cells
Figure 20: Reel-up of the finished back-contact film
Once the mask was removed, the material was reel-up for sending to F-ISE. Figure 21 shows part of the completed reel of material.
Figure 21: The reel of back-contact material to be shipped to F-ISE
Figure 22: the silver ink after it was cured
Figure 23: application of the Tensile PVC onto the substrate containing the cells
The image below is of the full stack; back contacts, OPV materials, front-contact and water-protection encapsulation and PVC top-sheet. There is some reticulation of the OPV coating from the areas without back-contacts; however this is insignificant because these are non-active areas of the device, see Figure 24.
Figure 24: one of the 120 mm repeats showing a set of 6 cells in series.
After the cells had completed the lamination process at Coatema they were shipped as a continuous roll to I2O where they were welded into a tensile structure. The Figures 25 and 26 show the cells laid out on the welding surface prior to construction. Fortunately the consortium partners had made an excessive number of modules for the final demonstrators as one of the modules had been shortened by an unknown party between lamination at Coatema and shipping to I2O, therefore one of the larger cells no longer had an intact water-barrier envelope.
Figure 25: some of the OPV cells at I2O pre-lamination
Figure 26: the cells as above, the ‘shortened’ one 2nd from the right
The cells were then welded onto tensile fabric to form the final demonstrator, Figure 24 shows the flexible CIGS and Si welded onto a blue tensile fabric prior to being stretched into a barrel-arch.
Figure 27: CIGS and Si cells welded onto a blue tensile fabric 6 m x 2.4 m
The active PV layer was prepared onto the final barrier layer ‘sandwich’ incorporating mechanical decoupling layers and the electrical connections on a roll to roll process at Coatema as described in deliverable 6.2
Figure 28. 6m OPV cells being prepared for high frequency bonding onto the tensile PV membrane
The final barrier layer sandwich was stretched out flat prior to bonding onto the tensile membrane, using high frequency welding techniques. Pockets were added around the membrane to allow the tensilePV membrane to be incorporated into a frame.
Figure 29. 6m TensileOPV membrane in a frame prior to tensioning.
Similar techniques were used to prepare the inorganic tensilePV membranes.
The final barrier layer sandwich was stretched out flat prior to bonding onto the tensile membrane, using high frequency welding techniques. Pockets were added around the membrane to allow the tensilePV membrane to be incorporated into a frame.
Figure 30. TensilePV CIGS membrane tensioned into Barrel arch frame.
Potential Impact:
The principle means of dissemination of the knowledge gained through the project will be through commercial exploitation.
Some parts of the findings from the project were written up and published in seven publications:
- V. Bozhilov, S. Kozhukharov, E. Bubev, M. Machkova, V. Kozhukharov, “Application of TiO2 and its derivatives for alternative energetic sources”, Proceedings of “Angel Kanchev” University of Ruse (Bulgaria), 51, (9.1) (2012), 36 – 40. Link - http://conf.uni-ruse.bg/bg/docs/cp12/9.1/9.1-6.pdf
- E. Bubev, S. Kozhukharov, V. Bozhilov, M. Machkova, V. Kozhukharov, “Employment of photosensitized TiO2 in photoelectrochemical energetic sources”, Proceedings of “Angel Kanchev” University of Ruse (Bulgaria), 51, (9.1) (2012), 69 – 73. Link - http://conf.uni-ruse.bg/bg/docs/cp12/9.1/9.1-12.pdf
- Valentin Bozhilov, E. Bubev,S. Kozhuharov, V. Kozhuharov, M. Machkova, “Barrier layers for application in organic solar cells”, Second International Conference on Materials for Energy, DECHEMA, Convention Center Karlsruhe, Germany 12-16 May 2013.
- E. Bubev, Valentin Bozhilov, S. Kozhuharov, V. Kozhuharov, M. Machkova, “UV- protection for Organic Photovoltaic Solar Cells” Second International Conference on Materials for Energy, DECHEMA, Convention Center Karlsruhe, Germany 12-16 May 2013.
- V. Bozhilov, S. Kozhukharov, E. Bubev, M. Machkova, V. Kozhukharov, „Classification and functional characterization of the basic types of photovoltaic elements“, Bulgarian Chemical Communications, v. 45, Special Edition A (269 – 273) 2013.
- E. Bubev - RES Summer school in TEI Patras, Greece ,1-12July 2012, Presentation -“DEGRADATION AND STABILITY OF ORGANIC PHOTOVOLTAIC CELLS”. Link - http://dasta.teipat.gr/system/files/moke/Degradation%20and%20Stability%20of%20Organic%20Solar%20Cells.pdf
Trade exhibitions, conferences and summer schools also benefited from the knowledge gained through the Fabrigen project:
- R.E.S. Summer school in TEI Patras, Greece , 1-12 July 2012 (Eng. E.Bubev)
- National Chemical Conference - Technical University “A. Kanchev”, Russe, Bulgaria, Nov. 2012
- International LII Annual Conference of Spanish SECV, 03 - 06 October 2012 Burgos, Spain, participation with report as invited lecturer.
- PRACE Autumn School on Massively Parallel Architectures and Molecular Simulations in The National Centre for Supercomputing Applications, 24 to 28th of September, 2012 in ,Sofia, Bulgaria.
- International Second International Conference on Materials for Energy, DECHEMA, 10-13 May 2013, Convention Center Karlsruhe, Germany).
- R.E.S. Summer school in TEI Patras, Greece ,01-12July 2013,Patras (Eng.V.Bozhilov)
- Participation of 2 PhD students from FabriGen team in "Center of mathematical modeling and computer simulation for training & development of young researchers", Project No BG051PO001-3.3.06-2014 (http://www.uctm.edu/mmcentre/) .
- Trade exhibition participation:
- “Energy Efficiency & Renewable Energy” organized from Inter Expo Center, Sofia, 28-30 March 2012; http://iec.bg/bg ;
- South-East European PV Exibition,Sofia,Bulgaria, 29-31May 2012 in parallel with South-East European Solar Ex. (SEE Solar) http://www.eeandres.viaexpo.com/en/seesolar
The principle trade exhibition was LOPEC ‘Large area Printed EleCtronics exhibition and conference (LOPEC) At Messe Munchen, Germany, on the 26th to the 28th May, 2014, during which the Fabrigen project featured on two stands – Coatema and Fraunhofer ISE and a presentation was given,
Commercial Exploitation:
Improving the competitiveness of the SME participants
Section 1 of this proposal has demonstrated that there is a fundable need for innovation to reduce the levelised Cost of Electricity (LCOE) of grid-connected PV systems and to offer innovative products to the solar energy market. FIT polices provide an opportunity for increased private sector research and development, spurring innovation and cost reductions. A recent paper highlights the opportunities for SME-led innovation in the PV energy sector, in particular by harnessing the strength of R&D and supply-chain clusters across Europe12. The domestic rooftop market is being aggressively targeted in many countries, however there is an opportunity to offer innovative PV solutions using fabric structures for public and commercial spaces e.g. for public transport companies, retail and commercial businesses, farmers, schools and local Government.
The rewards for solar PV providers will be significant: the global solar energy market is expected to reach $34 billion investment per year in 2010 and over $100 billion new investments per year by 2050. Europe, with over 65% market, holds a leading share in the global photovoltaic (PV) market in 2010. Germany with 43% share would be the world leader in PV market. Allied to this there are political mandates (including the EU2020 renewable energy targets, and SEII solar PV targets) and public demand for green policies.
The conventional solar panel market is facing PV system cost declines and global competition, with growing influence of Chinese PV module and system suppliers. The European lead in PV is under threat from the growing PV R&D and supply market power of US, Far East and China. Leading utilities and independent power producers are increasingly sourcing modules on the spot market. To address this competition, there has been a move to non-silicon and thin-film PV technologies (e.g. CdTe, CIGS and amorphous silicon thin film modules) however these only show marginal benefits, and have very similar installation requirements to conventional solar panels. This market background offers an opportunity for the SME participants in this consortium to develop a new product for the solar power market that has the potential for lower cost modules - through the use of printed OPV technology, and lower installation costs - through large-area, low-cost fabric structures.
An important benefit of the project is that the components technologies and methods developed for OPV fabrication are likely to have spin-off applications and benefits in other fields – particularly Organic Light Emitting Displays (OLEDs) and other printed electronics applications. All printed electronics devices require printed conductors, and most require barrier and encapsulation layers (in fact the barrier specifications for OLEDs are even more stringent than for OPV devices). The OLED and printed electronics markets are actually larger than the OPV market
Through this project the SMEs in the consortium will each improve their competitiveness as described below:
Inside2Outside Ltd.
Current business: Design, manufacture and supply of tensile fabric structures – primarily in the UK
Threats: Fabric structure manufacturers are facing slow growth against a background of increasing cost of raw materials and a slowdown in economic conditions. There is a continuing trend toward using fabric in building projects in place of traditional (and often more expensive and less efficient) materials such as steel and concrete, however the market is very competitive. Until the economy rebounds, the architectural building market segment is likely to be sluggish and difficult for SMEs.
New business opportunities: The FabriGen project offers Inside2Outside the opportunity to develop a new business stream in solar fabric structures and solutions that will make them highly differentiated in the market, and able to offer a product that meet the aspirations of the new economy i.e. ‘green’, sustainable and revenue- generating. As discussed FITs offer an opportunity to enter the market with products that are currently uncompetitive against fossil-fuel alternatives. This will enable Inside2Outside to establish and grow the business whilst reducing the LCOE further through lower supply and installation costs (through volume purchasing and sales) and higher efficiency modules (further research). Over time the FIT’s will reduce, however by then Inside2Outside will have a thriving business and will be reinvesting in R&D. International collaboration will enable I2O to benefit from the experience and contacts made through this project.
Coatema Coating Machinery GmbH
Current business: Coatema is manufacturer of high quality coating and laminating plants. From manufacturing product development to commissioning in the areas of textiles, paper, foil, nanotechnologies, film, solar cells, fuel cells, batteries, medical applications, glass, and single aggregates or turn-key production plants.
Threats: Coatema is a highly respected company, and has won this respect through continuous innovation and R&D. However as part of the European equipment manufacturing sector Coatema is subject to the common threats facing European manufacturers – particularly SME manufacturers – of overseas competition and a difficult industrial investment environment. To maintain their position Coatema need to look ahead to new opportunities for their coating and laminating capabilities.
New business opportunities: The Fabrigen project offers Coatema the opportunity to find a new and large market for both their coating and lamination equipment. By working with researchers at an early stage they can offer their production expertise and make sure that their own R&D matches future demands. Coatema are the ideal partner to develop a pilot-production line for the FabriGen product. This project fits well with Coatema’s other R&D activities, for example the FP7 projects Flexlas and Clean4Yield.
RTD partners
Whilst the intention is for the RTD partners to hand over IP in return for payment, this does not mean that direct monetary return is the only, or indeed the prime, motivation for the RTD performers. The RTD partners, Fraunhofer ISE, UCTM, DZP Technologies and The Centre for Process (CPI) Innovation all thrive on research activity, knowledge generation, and the exchange of ideas with peers. Maintaining their institutions at the forefront of technological development is important for their future prospects. In addition they will bring background IP which may be built on an exploited in the FabriGen and solar cell projects (in agreement with the partners). In this way the project provide the exploitation links to industry that the RTD partners need.
Fraunhofer ISE gained valuable knowledge on printing Silver on top of organic functional layers. This knowledge will be exploited by Fraunhofer to acquire new research projects. Encouraged by the good results of the project Fraunhofer has ordered a rotary screen printing unit to extend the R2R coating equipment which was used to deposit the organic functional layers. The complete R2R processing of the ITO-free organic PV modules may not be directly exploitable as a commercial product as the power conversion efficiency of those modules is yet too low but the consortium gained a sound basis for follow up projects.
Inside2outside received an Excel-tool which helps to design the circuitry of an installation which makes this process faster and helps to prevent from under- or over dimensioning circuitry (Copper lanes or cables), saving cost by guaranteeing the quantitative addition of the power output of the subunits (modules) within the PV System using a reasonable dimensioning thus cost for the circuitry.
DZP Technologies itself is a commercial SME start-up that has background IP in printed electronics technology that will be brought into the project which significantly benefited the project in terms of achieving the objectives. New knowledge gained through the project has been considerable: As a result of their participation in the Fabrigen project, DZP have decided to invest their own resources in further advancing the development of next generation PV. The company is now sponsoring an EngD student at the University of Surrey who is based in the company and continuing the research on printable hybrid PV. In this way, these is increased R&D spending, supporting innovation, training of post-graduate students, and the development of clean technologies in accordance with the EU targets for renewable energy generation;
Development of PV structures which do not make use of Indium Tin Oxide (ITO) - One of the main achievements of the project is the demonstration of flexible solar cells deposited on non-ITO substrates. This approach was adopted by DZP from the very beginning of the project, and later adopted by the other partners and incorporated into the demonstration module. This is major outcome, as this technological solution circumvents the use of ITO. The later material is not only expensive and unsustainable, but it is unsuitable for flexible electronic and opto-electronic devices due to its brittleness. Cracks are easily formed in ITO during flexible, resulting in shorting and failure of the devices. During Fabrigen, effort thus focused on using aluminium substrates and back electrodes. This material is not only cheaper, but also suitable manufacturing processes are already scaled up for the production of aluminium foils and lamination of plastic substrates. The problem with aluminium oxidation was solved at CPI and FISE by using a protective Cr layer on top of the aluminium film.
Development of hybrid PV material and processes - Most initial work in Fabrigen focused on using hybrid Copper phthalocyanine (CuPc)/TiO2 hybrid inks, as well as the analogues with ZnO. This was justified by previous promising results obtained at DZP which showed good photodiode performance of printed CuPc compositions. Hybrid inks and deposition methods were successfully developed and demonstrated by DZP. However, during Fabrigen, it was found that the CuPc based materials exhibit low conversion efficiency due to their relatively poor absorption, typically much less than 1%. This finding was confirmed not only for printed, but also for deposited films of pure CuPc. Additionally, strong degradation effects were found on light irradiation, especially from the UV part of the spectrum.
Regardless of the poor performance of the CuPc PV cells, the generated new knowledge may have strong impact on future PV technologies. Importantly, the materials and processes developed during the Fabrigen work, can be transferred to newly discovered, highly efficient materials such as organic-inorganic lead halide perovskites. Perovskite PV cells which are recently reported to exhibit efficiencies in excess of 10%, can be produced using DZP methodology by replacing the CuPc absorber with lead halide perovskite absorber, whilst retaining the TiO2 scaffold structure. The perovskite material in this case offers dramatically improved efficiency due to the broader absorption spectrum of the lead halide perovskite, and the longer diffusion length as compared to the CuPc material.
Development of silicon PV inks - Another material which was specifically developed during the Fabrigen project includes water-based silicon inks based on nano-crystalline silicon and amorphous silicon. Related deposition processes were also developed and silicon films can now be routinely printed using screen or flexographic printing at temperatures as low as 120 °. The new materials and processes are thus suitable for use on flexible plastic substrates. The silicon printed films exhibit significantly improved stability compared the CuPc analogues and deserve further detailed investigations. Given the time constrains of Fabrigen, this work was carried out only on small cells (up to 2 x 2 cm), and no scale-up development was carried out.
UCTM has developed a series of teaching tools to BSC and MSC levels as follows:
- IV characteristics measurements
- Electrochemical Impedance Spectroscopy & Cyclic voltametry
- Atomic Force Microscope
- Contact angle measurements and interpretation
- Color characteristics OPV measurements
- UV testing of organic materials
- Laboratory tests and OPV aging phenomena determination (UV, to, τ, atmosphere)
- UV-Vis spectroscopy measurements
- Thermal behavior of the materials & simultaneous TG-DTA and TG-DSC analysis
CPI has developed further knowledge of Integration of solar modules to tensile membranes; welding method combined with a separate WVTR barrier versus a single laminated stack; Patterning of overlay of cells to allow flex; Corrugated PV cells and stress-relief layer and Hexagonal PV cells and electrode patterning.
Exploitation plan and returns to the consortium partners
The outline plan for the route to market in the primary market for the FabriGen technology shows where the consortium partners are planned to benefit from their position in the supply chain. In this scenario Inside2Outside will be key license holder for the overall FabriGen technology developed in the project as they are in the prime position to exploit the results, and bring consequent benefits to the other partners. It is planned for Inside2Outside to license manufacture of the OPV modules and lamination/integration with tensile fabrics as this will require volume manufacture. Coatema will be the preferred manufacturer and supplier of specialist production machinery for the roll-to-roll fabrication and lamination of the OPV fabric and will license IP as necessary to support production. Distribution to the European and global market will need a market partner (or partners) and a large number of distributers. Companies such as SKYShades, an Australian company that focuses on the delivery of tension membrane fabrication products through a global licensed distribution network, and who are already making moves in fabric PV systems. Sky Shades is represented in Australia, South East Asia, India, North America, South Africa, South America and China.
Market size
The exploitation plan focuses on the use of TensilePV fabric solar materials for local power generation as well as grid- connected power generation. However the largest market in the short term is grid-connected applications that are eligible for FIT schemes e.g typically with a scalable size of installed system up to 5MWp. This is an area where SKYShades and others cannot yet access, due to the relatively short outdoor life of the OPV modules, and relatively high cost of alternative PV technologies. In 2008 NanoMarkets predicted that the worldwide market for OPV photovoltaics will total about $40 million in 2012 and by 2015 reach $450 million. However these figures are based on the use of OPV devices primarily for local power and battery charging in consumer devices. With the efficiency and lifetime increases planned in this project, OPV modules will be a realistic and attractive option for larger power generation schemes, and, when certified for FIT schemes, the potential market will increase hugely. For example in the SEII scenario, European PV capacity will increase from the current 26GWp to supply 12% of European electricity demand by 2020 i.e. approximately 400GWp PV capacity. If we assume that only 5% of this demand is produced by solar PV fabrics at a cost of 3€/Wp (current) falling to 1 €/Wp (2020) this gives a current European market size of €3.9billion growing to €20billion by 2020.
Inside2Outside has been working on a business plan for the UK with the distributor network. With the setting up a worldwide network dedicated to the supply and installation of tensile PV. With the added performance and lifetime expected from the Fabrigen modules, it is anticipated that two years post market introduction that FabriGen solar PV systems are supplied and installed through 125 distributors in the UK alone, each exceeding a £1,000,000 turnover with about 8% net profit i.e. a £125m turnover and £10m profit. Expanding into Europe we estimate that this could reach €1billion turnover by 2020. Thus, with a very modest market penetration, the returns are substantial. This turnover will lead to a significant increase in European economic activity and increase in employment for fabric suppliers, component suppliers, manufacturers, designers, testing and certification companies, distributers and installers. The EPIA estimated that 30 full-time equivalent (FTE) jobs are created for each MW of solar power modules produced and installed, suggesting that 600,000 jobs across the PV supply chain could be created by 2020 for solar fabric PV systems. In addition this will make a significant contribution to the European renewable energy targets and reduction in CO2 emission.
Estimated Time-to-Market and Further Development Activities
The FabriGen project has led to a prototype demonstration of fabric-integrated PV modules. In addition the fabrication processes has developed to 100cm wide web. The next stage will be to implement these processes in a pilot-production plant which will provide TensilePV fabrics for the first commercial launch of the FabriGen products. Since the aim is to use conventional printing processes and equipment as much as possible it may be possible to use an existing roll-to-roll printing production line and convert this with the specialist processes, materials and techniques needed for TensilePV manufacture. The European printing industry is under severe pressure from Far East competition, the downturn in the economy and the reduction in printed material demand, hence there is an opportunity for printers to diversify into electronic materials printing. The consortium includes Coatema Coating Machinery who are European leaders in taking processes from R&D through to turn- key production solutions. They have extensive experience in printing equipment, multi-functional coating equipment and laminating solutions, for both solvent and water-based processes.
Figure 16. Coatema design and manufacture turn-key roll-to-roll coating and lamination machinery, such as the system here.
Given sufficient support and funding, we estimate a time to market post-project of 12 -18 months for the first mass-produced FabriGen PV fabrics, although smaller manufacturing quantities will be produced in this period for full certification and extended lifetime testing, and for marketing purposes.
European Community/ Societal Impact
As discussed in Section 1, if Europe is to meet the ambitious 2020 targets for renewable energy then there needs to be dramatic acceleration of installed PV systems. Without action the threat of climate change and rising global temperatures are likely to have severe economic and social consequences. The European community will not be isolated from these issues, as economic trade, food production, resource scarcities all have global repercussions. Current PV technologies, if adopted more widely, will have a large part to play in providing the PV capacity needed, however there is no doubt that new innovations are needed in order to allow PV to compete without subsidy, and as shown the market potential is huge. As usual, however, it is likely to be the poorest countries who will suffer the most from climate change, as crops fail and severe weather events ruin economies and lives. The potential for low cost, easily-transported OPV fabric-based local power for lighting, irrigation, communications and entertainment etc., could have a dramatic effect on lives in what are known as ‘resource-poor’ countries. Many of these same countries have a high solar resource, which could transform their economies if it can be captured and converted to useful energy.
For purchasers of the system there are substantial returns to be made from the investment, which may lead to offers of free installation in return for FIT payments (which is already happening in the solar industry). Alternatively this could lead to income generation for landowners and property holders. For example there is an opportunity to target farmers who could construct fabric PV structures as dual-use structures, e.g. for storage of crops, animal shelters etc, or who could use fallow or set-aside land as areas to construct fabric solar farms. This has the advantage over conventional panels that it would be cheaper to install and relatively easy to move fabric structures. Table below shows the potential costs and return from a farm building roof covered with FabriGen solar PV fabric, with a Wp of100W/m2 over a 20-year period, using current UK FIT rates. A payback period of 6 years, with potential returns many times the initial investment will provide a high incentive to invest in the FabriGen technology.
Roof space 500 m2
Installed cost £126.00 per m2
CO2 production 0.435 tonnes per MWh
Feed-in tariff (guaranteed 20 years) £0.1238 per kWh
Peak power for installation 49,060 Wp
Cost of electricity £0.10 per kWh
Electricity cost inflation 6% per annum
Output 850 kWh per kW installed
Annual output 41,700 kWh
Initial Cost of installation £63,000
Payback period (incl capital allowances) 6 Years
Net value of project (net profit) £330,108 Over 20 years
Table 11. Example installation of a TensilePV system for a farm building project, showing a net profit of
£0.33 million pounds over 20 years, with today’s level of Feed-in-Tariffs in the UK, for an initial investment of
£60k.
Justification of Trans-national Approach
Whilst Germany dominates the solar PV market in Europe, and a high number of the leading research, development and production enterprises, there is a need for higher PV adoption in other countries in the EU. Already the FIT tariffs are being reduced in Germany, while other countries are introducing generous tariffs. Any exploitation therefore needs to be flexible and transnational with regard to market. The project makes use of this leading expertise in Germany and allies this with expertise from other countries to provide both a wide research expertise and a transnational exploitation opportunity.
Robert Carpenter, Inside2Outside Ltd. (+44) 1480 409297
Robert.carpenter@inside2outside.co.uk.