Final Report Summary - INTENSOL (Transparent Fresnel Based Concentrated Photovoltaic Thermal System)
Executive Summary:
The Intensol project set out to develop a hybrid solar PV/Thermal system based upon high concentration PV with liquid cooling and a solar thermal ‘afterheater’ concept for the integrated supply of electricity and hot water.
The system is based on the development of novel cost effective Fresnel lens based concentrators working with liquid cooled triple junction PV cell technology. Product will be equipped with integrated liquid cell cooling and heat recuperation system, positioned by high accuracy two axes tracking system and guided by an adaptive control system. It enables energy output optimization (electrical and thermal), maintaining the solar cell temperature and thermal fluid temperatures at optimal levels for the required output and insolation conditions.
All components and systems have been integrated and optimized as an autonomous unmanned cogeneration power plant unit in a form of new commercial product, the INTENSOL. INTENSOL is therefore a development of the following combination of key innovative technologies:
• Cost effective Fresnel lens based concentrators
• Triple junction cells (TJC)
• Solar cell Heat management, TJC cooling and additional heat recuperation system
• Optimization process for electrical and thermal power output
• Highly accurate low profile two axis tracking system
• Advanced guidance and control system
The project developed a number of intermediate prototypes but has completed with a integrated final prototype installed in Croatia incorporating:
• Novel low profile 2-axis tracker
• Glass Fresnel lens panels based on a roll to roll manufactured PMMA Fresnel lens laminated using a novel approach to solar glass panels
• Liquid cooled individual high concentration solar cell assemblies based on a CPU cooler approach optimised to minimise the thermal gradient from solar cell to cooling liquid and able to highly effectively cool cells at solar concentrations of 1,000
• Control algorithms integrating clock based high accuracy solar position estimation, sun sensor and maximum power output fine tuning, with specific safety conditions particularly associated with ensuring cells are always actively cooled when on sun
• Optional after heaters based on either high efficiency flat solar thermal panels or medium concentration solar thermal system
Project Context and Objectives:
The objective of the Intensol project was to develop an efficient and cost effective solar energy system for combined electrical and thermal energy production that uses direct solar radiation as the primary energy source.
In order to achieve those objectives the consortium developed a combination of a state of the art liquid cooled High Concentration PV Solar System which is based on a combination of the latest developments in high concentration optics and photovoltaic technology along with solar thermal components (fully integrated liquid cooling for the PV cells minimising the thermal gradient), showing the system can be put in series with a number of modular solar thermal systems (flat panel, low low to medium concentration) resulting in a product that is able to produce electricity and heat from one integrated system.
The system is based on the development of novel cost effective Fresnel lens based concentrators working with triple junction PV cell technology. Product will be equipped with integrated liquid cell cooling and heat recuperation system, positioned by high accuracy low profile two axis tracking system and guided by an adaptive control system integrating control of the tracker, electrical nad thermal systems. It should enable energy output optimization (electrical and thermal), maintaining the solar cell temperature and thermal fluid temperatures at optimal levels for the required output and insolation conditions and ensuring system safety at all times.
All components and systems will be integrated and optimized as an autonomous unmanned cogeneration power plant unit in a form of new commercial product, the INTENSOL. INTENSOL is therefore a development of the following combination of key innovative technologies:
- Cost effective Fresnel lens based concentrators
- Triple junction cells (TJC)
- Solar cell Heat management, TJC cooling and additional heat recuperation system
- Optimization process for electrical and thermal power output
- Highly accurate low profile two axis tracking system
- Advanced guidance and control system
The ultimate goal is to achieve all this whilst seeking a target installed price of around 3-4 euros per peak watt.
Project Results:
Summary
Technical progress and achievements
1. A detailed evaluation and design exercise was conducted, including full system evaluation, optics design, spectral radiation evaluation and load and thermal modeling.
2. The HCPVT cooler block was evaluated and several designs implemented and evaluated. A low cost arrangement was designed meeting the requirements, based on CPU cooling units design. An final overall receiver arrangement was constructed with a low thermal path between cell and the top copper block of the liquid cooler, using thin solder layers both between the cell and a high thermal conductivity ceramic receiver (on which the electrical connections and bypass diode were mounted) solder bonded to the copper block forming the top part of the liquid cooler.
3. The primary optics were designed and fabricated and supplied to partners, in PMMA panels bonded to a PMMA support for prototype 1 and in glass panels for final prototype – both in a 3 by 1 lens arrangement with 350mm square Fresnel lenses. The primary Fresnel lens optics were produced using a roll to roll production process, and the lens film was laminated using a solvent bond process to PMMA sheet (in prototype 1) and using a novel UV cured low weathering silicone adhesive formulated by Microsharp to solar glass (in the final prototype),
4. A range of secondary optics were evaluated including silicone and glass designs. A reflective secondary was supplied for the initial prototypes and an improved reflective secondary optics for the final prototype based on evaluations for relative costs and performance
5. 40 receiver modules were supplied by Quantasol along with operating data for the first prototype. 7 cell wafers were supplied by IQE for the final prototype which were converted (electrode added and diced) by CESI into approximately 250 cells and mounted (solder bonded) on aluminium nitride ceramic plates (integrating electrodes and bypass diode) by Aurel. These ceramic plates were in turn solder bonded onto machined copper blocks (the top component of the liquid cooling assembly) by Aurel and in turn the copper blocks were integrated into a full receiver module by iXscient
6. A two axis, low profile, tracker was constructed by Novamina for the first prototype. ITAV designed, simulated, optimized and constructed a large, low profile, tracker for the final prototype which was delivered and assembled at Novamina in Croatia
7. The ITAV first prototype module, with a Novamina designed liquid cooler and integrated receivers was assembled and tested in Croatia using the Novamina tracker
8. The iXscient first prototype module was constructed and tested at Microsharp on its central pole tracker in the UK
9. Xscient designed an aluminium module for the second prototype, incorporating 4 units of the 3 by 1 lens array and 12 receiver modules. A first example was constructed in Uk and delivered to Microsharp, the final 16 modules constructed at Novamina
10. The final prototype was assembled at Novamina in Croatia incorporating:
• The low profile tracker from ITAV
• The aluminum modules (16) with integrated glass primary optics, receiver units from iXscient
• Tracker actuators and control system, plus electrical and fluidic connections and management from Novamina
WP 1: Development of high concentrating Fresnel lens based on low cost optical film
Task 1.1 Optical Design Specifications
ITAV, Novamina, Microsharp and iXscient cooperated in developing the overall system design, including generic issues relating to balance between heat and electrical outputs, generic CPV design issues and some specific aspects of the INTENSOL design. This work is detailed in Deliverable D1.1.
iXscient and Microsharp cooperated in the development of the specifications for the system optics. These were derived from the overall system specifications and design developed by the consortium and written up in deliverable: D1.1: Specification and Design document. In general, from the point of view of the optics, the necessary elements include:
• The size of the system optical units should be small in number and each large in size in order to minimize the loss of energy that would result from an increase in the number of units and decrease in size – this follows from volume and surface area considerations.
• The concentration ratio should be high since we are able to actively remove heat using liquid cooling and therefore in order to maximize the flow of heat and minimise the overall system costs, a concentration level of around 1000 should be sought.
As a result it was decided to produce a lens which would achieve (at 80% efficiency of the optics) a 1000 times solar concentration on a 1 cm by 1 cm cell (this is a standard size for the triple junction cell industry).
The maximum size that a lens master can be constructed is around 500mm diameter (this is due to constraints on the cutting machine that Microsharp have access to). This can generate a lens 350 mm by 350mm. The final solar concentration should therefore be approximately 900-1000 times.
Choice of Lens Focal Depth
The lens design requires a choice of focal depth. Generally as the focal depth increases the efficiency of the lens increases, but the total materials required for the module increases and the off axis tolerance decreases. Therefore as short a focal depth as possible consistent with a good performance is required.
The calculations for the efficiency of the lenses takes into account:
• Reflective losses from the front surface of the film, which increases with angle of the lens to the light
• Refractive losses (Fresnel losses) from the prisms at the back of the lens
• Losses that arise from manufacturing issues at the facet apex resulting in non-optical performance of part of the prism facet – in this case two manufacturing approaches are examined – a half radius tool and a full radius tool. The full radius tool (of between 1 and 3 microns) is the more accurate to actual manufacturing practice
• The proportion of light with wavelengths from 300nm to 1600nm falling inside the target collection size (see above)
A focal depth of approximately 45 cm was therefore recommended.
Optical Design and Simulation
Based on this initial focal depth estimate, Light Tools (a ray tracing software package) was used to optimize the design of 350 by 350mm lens, seeking to jointly maximize the efficiency whilst minimizing the focal length. An additional ray tracing software package, TracePro, was also used.
The efficiency of the lens (in fact total optical set up including secondary) is extremely important as a wide off axis angular tolerance enables easier module assembly and lower tracker accuracies.
Off-axis angle(°) 0, 0 0, 0.5 0.5 0.5 0, 1 1, 1
Efficiency (%) 80.89 79.56 78.10 69.27 60.83
Efficiency at Different Off-axis Angles
The simulations show good results and therefore the lens design was finalised.
Choice and Selection of secondary
A wide variety of options for the secondary optics in the system were considered, including glass and silicone secondaries. Following examination of the cost and relative performance options a simpler alternative of a wide tapered reflective rectangular secondary was selected, since this was a low cost and simple option.
Table 1: reflective secondary parameters (final prototype)
Exit size 1 cm
Entry size 5 cm
Height 5 cm
Slope angle 26.5 degrees
This design has the benefit of being simple and cheap (costing less than 30 Euro cents in volume).
Quantasol analysis of location spectral conditions
In order to understand the requirements for the spectral performance of the system (optics, solar cell), Quantasol performed a spectral analysis of the target Croatian location and related this to specific designs of triple junction cells which could optimally perform in this location.
In conclusion, it is possible to increase annual power output by around 6% by choosing a triple junction cell which matched to the target spectral balance.
Following the withdrawal of Quantasol from the project IQE provided fairly basic triple junction cells for use in the project. However an introduction was made with their partner company Solar Junction and discussions indicated that cells with efficiencies of approximately 44% could be sourced in the near future, which exceed even the performance of the optimized Quantasol cells.
Task 1.2 Exploration of outer surface coating for AR, anti-scratch and self-cleaning
A review was undertaken by iXscient to examine possible beneficial coatings for the primary optics. Several problems affect CPV lenses which reduce their efficiency. These can be listed as:
1. Reflection of the top flat surface
2. Reflection of the Fresnel (underside) facets
3. Water droplet condensation on the top surface
4. Water droplet condensation on the Fresnel facets
5. Dust and sand blown scratching on the flat outer surface
6. Dirt, dust and organic residues deposited on the outer flat surface which block the light
For antifogging coatings, no coating with suitable lifetime were identified. No cost effective solutions were identified for antiscratch, but the development of a lens film to glass lamination process by Microsharp obviated this issue, provided any further coatings were scratch resistant.
For AR coatings, only single layer coatings were considered due to cost and lifetime issues. Three types of coatings are potentially useable:
• Sol-gel coatings
• Khepricoat (DSM)
• Solarphire (PPG)
These coatings are only applicable to glass. In the final Intensol prototype detailed discussions were held with the suppliers of Khepricoat (DSM), which has been developed for standard PV panel outer surface. It retains the scratch resistance of glass. Costings obtained indicate that this is a cost effective solution for improving the performance of the primary optics.
Since the optics are tracked with regard to the sun, the total transmittance of the planar glass is increased from around 93% (flat glass reflection) to over 96% (a 3-4% improvement in transmission).
In conclusion for the final prototype of the INTENSOL system, glass based optics were used and Khepricoat is the chosen solution for outer coating.
Task 1.3 Lens prototype fabrication and testing
Development and Manufacture of Lens
From the lens design parameters, a master disc was diamond cut on a copper blank for the large flat lens design. Plastic replicas from this master were cast directly for testing, and for nickel electroplating to form the manufacturing shim.
Lens Testing Setup
iXscient conducted a detailed appraisal, in collaboration with Microsharp, of the components and setup needed for improvement to Microsharp’s lens testing arrangements.
This work was summarized in deliverable D1.2: Lens Test Report
Lens Testing on Final Primary Optics
This is summarized in deliverable D6.1 Industrial testing of performances and functioning of the Fresnel lenses with two axis tracking function . The final glass assemblies are around 77% efficient and have an acceptance angle on the final receiver assembly of around 0.75 degrees.
Task 1.4 Development of lamination for 3D lenses
The lens films are manufactured using Microsharp’s standard UV microoptics roll to roll production system. A base film (250 micron thick PMMA from Evonic) is coated with a thin layer of a specific UV curable acrylic resin specifically developed and optimized at Microsharp to achieve long lifetime under solar weathering conditions. The coated sheet is exposed to UV radiation when in contact with a moulding drum on which the mould for the 3 by 1 lens is mounted. The cured, cast optical structure is wound as a sheet.
For the first prototype the resulting film was cut into 3 by 1 sheets and solvent bonded onto 3mm PMMA sheets using methyl chloride in which 5% acrylic had been dissolved. The resulting sheets where aligned to the lens centres and the edges laser cut to achieve correct positioning of the lenses on the sheets (with respect to the edges).
For the final prototype the lens films were laminated to optical glass sheets (precut and beveled to correct size). The lamination process used a UV curable silicone adhesive specifically developed by Microsharp to enable long lifetime of the resulting laminate based upon excellent solar weathering for the silicone and the preservation of a flexible join between the film and the glass to enable differential thermal expansion.
To achieve the lamination on the glass, since the glass sheets could not be edge cut to enable correct positioning post lamination with respect to the lens centres, the following steps are taken:
• The glass is coated with the silicone adhesive
• The film is laminated on the glass using pressure rollers
• On a specially constructed jig, the film is moved to align the lens centres with their correct positions with respect the glass edges
• The resulting sheet is exposed to UV light to cure the silicone adhesive
In a final production process, it is anticipated that a glass edge cutting process, for example using laser scribing and breakage or water cutting, would be employed to speed an automated lamination process with an automated method for finding the lens centres.
For the final prototype 64 of 3 by 1 glass panels were manufactured and delivered.
Task 1.5 Finalisation of automated manufacture/Production of lens parquet/Full production lens parquets for system
First Prototype
The lens masters were nickel replicated into 3 lens replicas and joined using laser welding into a 3 by 1 shim. This was mounted on a large diameter production drum and film was manufactured by Microsharp and subsequently solvent bonded onto 3mm PMMA sheet using the solvent lamination process.
Final prototype
64 Laminated glass lens panels were produced, checked and shipped to Novamina.
Task 1.6 Sourcing glass secondaries and development of bonding to cell/Demonstration of optics (efficiency, angular tolerance) in simulated and actual sun
Experimentation with cast silicone secondaries
Some initial experiments were conducted with casting solid silicone secondaries from novel silicones supplied to Microsharp with long lifetime and high solar intensity survival.
Following an analysis of glass secondary performance and costs, an improved reflective secondary design was retained for the final prototype.
Tests were carried out on the performance of the final glass primary lens working with the completed final receiver design.
The lens was measured for proportion light on target across the lens using a collimated white light source and the standard silicon photodiode arranged within a 1 cm by 1 cm aperture with the reflective secondary mounted around this aperture.
The resulting integrated performance for a square lens is 79% (73% for round lens).
This is sufficiently close to the 80% target to be acceptable.
Measurements of a silicon photodiode 9rpelacing the triple junction cell) were carried out on the final receiver arrangement with collimated on-axis light
Condition Test 1 Test 2 Test 3
No concentration 24 (3) 33 (3.5) 35 (3.5)
Concentration, with attenuation filter 225.3 (11) 311 (14) 333 (15)
Estimated solar concentration 939 942 951
The results are a little down on the estimated concentration of 968 (79% efficiency). The efficiency estimate from these test is 77% efficient.
Off axis relative performance was measured (again using the open circuit current of a silicon photodiode replacing the triple junction cell):
A maximum off axis tolerance angle of 0.75 degrees is suggested.
WP2: Development, design of a hybrid solar thermal system integrated in the HCPV
Task 2.1: Detailed definition of operating parameters, thermo-physical properties
ITAV provided a detailed investigation into the alternatives for operating parameters of a solar system producing both electricity and power, predominantly based on the use of triple junction cells. The results are included in the report D1.1 Specification and Design document.
Task 2.2 Design of Heat pipe cooling of concentrating PV cells
Following the design and specification exercise, including costings for heat pipes system and individual liquid cooling blocks, it was determined that, for a 10mm by 10mm cell operating under 1000 times concentration, the optimal approach was a single block for each cell. Therefore the core work activities in this area related to the design and testing of individual thermal blocks.
Quantasol provided initial details of the anticipated receiver on which the solar cells will be supplied to the partners. For the final prototype IQE provided details of the cells it supplied, which are similar but with somewhat reduced efficiency (34% instead of 39%).
Quantasol supplied 40 receiver units to iXscient (10mm by 10mm solar cells bonded onto ceramic receivers with bypass diodes). The cells had bonded glass cover slides.
IQE supplied sufficient cells to achieve 250 receivers for the final prototype. These were solder on ceramic bases which in turn were solder bonded on copper blocks (the top part of the liquid cooler).
Novamina Activities
Exploration using commercial CPU cooler block
Initial investigations into cell/receiver cooling used a transistor which simulated receiver under solar heating supplying heat which should be dissipated from the cell (receiver-a) at maximum insolation I=1000 W/m^2. The transistor was cooled with a commercial “Zalman“ water block for CPU cooling and cooling water flow was achieved using a water pump . The aim of the experiment was to determine the temperature of the transistor housing at a given flow, inlet water temperature and transistor power which represented receiver heat dissipation.
Measurement setup consisted of an electrical part (which served to generate heat through transistor power) and transistor cooling.
Conclusion
The ultimate goal of the experiment was to show that the selected cooler can dissipate heat from the receiver HCPV cell/receiver at maximum insolation with given water flow and thereby maintain the temperature of receiver / cells to approximately 50 οC. The results showed that the selected lquid cooler can, without any difficulties, dissipate heat with minimal increase in outlet water and transistor temperature. To be closer to the receiver temperature of the 50 οC significantly lower flows or greater cooling water inlet temperatures are required. Thus we can conclude that this type of water cooling is more than satisfactory for our HCPV cell but considering its high price (about € 40) and some other defects (difficult to isolate, assembly etc.) we concluded that it is necessary to seek a simpler and cheaper solution.
The next solution was simple aluminum made water cooler/block. Shape and dimensions were derived from the thermal analysis using finite element method according to the following design criteria:
• Geometry which allows easy isolation
• Simple production
• Expenses (material+production)
The aim was the same as for CPU water block cooling simulation and we used exactly same measurement line and procedures.
Description of aluminium water cooler
Cooler was made of one piece machined 30mm Al6063 rod with a cylindrical flow chamber.
Conclusion
The ultimate goal of the experiment was to show that the selected aluminium cooler can dissipate heat from the receiver HCPV cell/receiver at maximum insolation with given water flow and thereby maintain the temperature of receiver / cells at approximately 50 οC. The results showed that selected cooler can without any difficulties dissipate heat with minimal increase in outlet water and transistor temperature. Thus we can conclude that this type of water cooling is satisfactory for our HCPV cell cooling because we can maintain our cell/receiver temperature at temperatures 11 οC higher than inlet water temperature with given flow and heat dissipation (at highest insolation). This solution is cheap, simple and easy to manufacture.
New Cooler Design
Following the initial work and results of feedback from iXscient on the use of the Alphacool commercial CPU cooler, a new design including flow channels, was developed.
Conclusion
Some thermal interface material has to be applied fulfilling the following criteria:
• Has to sustain properties for long time (for eq. more than 10 years); thermal pastes used for CPU cooling aren't appropriate due to limited condition usage (normally indoor conditions) and limited lifetime (in average 2-3 years and then has to be exchanged).
• Has to be applied in as thin layer as possible
• Thermal conductance has to be as high as possible ( > 1 W/mK)
It is not possible to determinate cell temperature under certain radiation due to several reasons:
• Electrically loading the cell changes heating of cell (and temperature)
• Variation in sun radiation changes cell heating (- temperature)
Possible method is to determine maximal cell temperature is to fix receiver on the particular cooler, heated it up by means of calibrated light concentration and measuring Voc, determine cell temperature under different concentration.
iXscient activities
In parallel to the activities at Novamina, iXscient sourced CPU coolers from Alphacool which used a microchannel array. Each cooler cost approximately 8 Euros.
Enhanced liquid cooler for final prototype
Based on the liquid cooler design from Alphacool and the experience of the need for a permanent high thermal conductivity bond between the receiver and the cooling element, iXscient developed a completed final receiver design including the following features:
• The triple junction cell remains solder bonded to the ceramic base, as in the first prototype
• A high thermal conductivity ceramic is used (Aluminium Nitride)
• The ceramic based is solder bonded to the machined (microgrooved) copper cooling block, i.e. the top part of the liquid cooler
• The base of the liquid cooler is integrated into the receiver arrangement, incorporating a base plate to attach to the overall enclosure module, the back part of the liquid cooler and elements to support the electrical and fluidic connections plus the secondary optics
Task 2.3: Design of Heat Pipes Thermal Transfer Systems and After heater
The previous analysis had indicated that an arrangement linking several receiver modules to a liquid cooler using heat pipes was not cost effective or thermally acceptable and that individual liquid cooling units were preferentially mounted on each receiver. Therefore the heat pipe design and analysis was not pursued after this initial analysis. As detailed above, effective individual liquid cooling units were designed for each receiver.
The preferred thermal arrangement consists of an input cooling liquid temperature of around 30 degrees and an output temperature of around 50 degrees from the high concentration PV units alone.
The goal is an output temperature of between 100 and 150 degrees. It was determined early in the project that the costs of tracking a solar thermal unit on the tracker built for the HCPV units was too high (the tracker area was better served by fully covering with the HCPV units), and that therefore two alternative arrangements should be considered:
• Efficient flat plate solar thermal units are run in series (after) the HCPV, to achieve final temperatures of around 100 degrees
• A separate 1 axis tracking solar concentrator system would be used to achieve final temperatures of around 200 degrees
Both systems were evaluated in WP6.
Tasks 2.4: Prototype manufacture and Lab testing
iXscient Testing
1. The receivers were mounted in the iXscient module and the module was left to track with no active cooling for several sunny days. Unfortunately the cells underwent runaway thermal destruction.
The bond between receivers and cooling block was examined and appeared to be only partial. It was changed from the silver thermal paste to a single part thermal epoxy.
A decision was made to only expose the unit to sunlight when active cooling was being undertaken. A black plastic cover was used to prevent light entering the unit except when the pump is working.
The system is mounted on the Feina tracker which achieves a good tracking and the light was observed to be within the secondary at all times.
In the following the fan rate was put at maximum in order to maximally cool the incoming water. The temperature achieved was 29 degrees (ambient 28 degrees).
Pump Rate Block Temp In temp Out temp Voc
10 31 29 31 8.65 – 70 degrees
1 41 29 38 8.45 – 75 degrees
When the pump was halted, the block temperature reached 75 degrees (alarm condition) within 10 seconds. The pump was then restarted and at full pump rate the block temperature reduced rapidly (within 10 seconds) to 32 degrees.
In conclusion, the liquid cooling block is sufficiently efficient. The current issues arise from the thermal gradient from cell to cooler block and this needs to be adequately addressed.
Full cooled receivers mounted in testing module
• Two cells were mounted in module and connected in serial connection and one cooling line (1st & 2nd position from the left)
• The third receiver in line was replaced by a cell simulating element (aluminum plate for cooler contact surface temperature measuring)
• Thermo couples were placed on the water inlet, outlet and on the simulating element
• Water flow was 4 l/min
Testing phase no. 1: Tracker accuracy & cooling efficiency
Performing period: September 2011 - starting date 12; - ending date 16
Testing condition:
- absolutely clear sky (no cloud at all during testing period)
- air temperature: 30 - 33 deg. C
- wind velocity: 0 m/s
Results indicated excellent control of the cell temperatures but high thermal gradient (around 30 degrees),
Afterheater using medium concentration linear solar unit
A linear solar concentrator was assembled with an Archimedes solar receiver tube.
Due to the weather the system was set up but not tested under solar conditions.
System simulation
Simulations were conducted for one day in July using Matlab Simulink tool. HCPV coolingsystem was modelled according to the real prototype. Input parameters were:
• Optical efficiency: 0,85
• Electrical efficiency: 0,35
• Aperture area: 1,01 m2
• Ethylene/Glycol 60/40% mixtureNine cells cooling loop connected in serial configuration were simulated with constant inlet temperature of 25°C and insolation for the average day in July for Zagreb, Croatia.
Three scenarios were simulated:
• After Heater with only vacuum tube without tracking and secondary mirror with optimum season angle
• with secondary mirror (CPC type collector) with optimum season angle
• with single axis tracking with Fresnel lenses
• (all three simulation s were conducted with one vacuum tube 4.06 m long)
• Tube optical efficiency is 0.7 and heat loss coefficient is Ul=20 W/m2K (mean value).
• Mean ambient temperature Ta=25°C.
After Heater with only a vacuum tube without tracking and secondary mirror with optimum season angle
• Tube absorber surface is Ap= 0, 88 m2
• Mass flow rate is qm= 3kg/mi
Increase in heat transfer fluid temperature is around 3°C for peak periods which is very poor considering targeted temperatures. Temperature can be increased by reducing the flow rate but that would result in lower effectiveness of HCPV cooling and higher cell temperatures.
After heater with secondary mirror (CPC type collector) with optimum season angle
• Effective aperture area is Ap=4,4 m2
• Concentration ratio is C=5
The secondary mirror significantly improved HTF temperature increase. In this case it is around 14 °C. It is important to mention that flow rate was set at 3 kg/min because that is the usual value for low temperature solar systems. Higher flow rates for medium-high temperature applications are higher.
After Heater with single axis tracking with Fresnel lenses
• Effective aperture area is Ap=19,3 m2
• Concentration ratio is C=22
As was assumed, best results were obtained for system with single axis tracking. In insolation peak period temperature increase was around 22°C with 10kg/min flow rate.
WP3: Development of concentrator panels with two axis tracking Function
Task 3.1: Material definition and design properties of light weight concentrator module
Both ITAV and iXscient developed first prototype modules in order to mount and test the receivers, coolers, and tracking arrangement. ITAV developed a 3 by 3 unit and iXscient a 1 by 3 unit.
iXscient designed the 12 receiver unit aluminium module for the final prototype.
ITAV First Prototype Module
ITAVs design was based on a framework of aluminium spars, using standard aluminium extrusions. The sides were of glass and the bottom aluminium.
The following shows the weight budget of the ITAV module:
Aluminum profiles 34 Kg
Aluminum walls and bottom sheet 18 Kg
PMMA lens and support 6 Kg
TOTAL 58 Kg
Aperture area 1,16m2
Aperture area / total area 0,725
Mass / total area 36,25 Kg/m2
The unit was built, including optics supplied by Microsharp/iXscient, and sent to Croatia.
iXscient first prototype module
The purpose of the iXscient module was to develop (over the course of the project) improved primary and secondary optics, and characterise their performance in terms of electrical and thermal behaviour.
The overall unit is a 3 by 1 arrangement. The receivers are liquid cooled using standard acquacool CPU cooling units. A computer liquid cooling pump, reservoir and cooling radiator was used to perfuse the unit.
The unit was delivered to Microsharp (with Microsharp optics integrated) and mounted on its current commercial (Feina FP9) tracker at its site in UK.
Final Prototype Module
iXscient designed the final prototype module to take the glass primary optics and the receiver modules.
A square box system including supports for 4 of 3 by 1 glass lens panels, and the polycarbonate plate elements was completed. One prototype was supplied to Microsharp and 18 modules to Novamina.
Task 3.2: Two axis tracking system actuator system design
The tracker design needs to take into consideration the requirements from the DOW:
1. Tracking in two axis:
• East-West rotation: -100° to 100° (azimuthal)
• Inclination: -10° to 75° (zenith)
2. Tracking pointing accuracy below 0.2°
3. It has to be modular to carry a variable number of modules. Maximum module area 30 m2
4. Control, Guidance – Predefined trajectory with optical sensor in internal closed loop
5. Safe position for standing high speed winds (up to 25 m/s)
6. Temperature range: -20 to 60 °C
7. UV resistant
8. Not add too much mass of the system, thereby reducing pointing accuracy or increasing the costs of the tracker (Overall mass per square meter, tracker plus modules?)
9. Be highly reliable, not compromising the overall lifetime and operating uptime of the system
Novamina designed a single module tracking unit for the first prototype and ITAV a low profile 18 module 2 axis tracker for the final prototype.
Task 3.3: Inclined support and rotating carousel design
The initial Novamina Tracker design consisted of 2 moving frames in total balance (no rotation moment due to weight of frames containing the CPVT module). Movements were implemented by means of 2 linear actuators and chain drive.
Inspiralia final prototype tracker design and construction
The work of INSPIRALIA during the second period has been focus on the mechanical design of a dual-axis tracking system. The final design fulfills functional specifications together with a cost effective design taking into account a future industrial production. The mechanical analysis has been performed with a CAE software, particularly with SOLIDWORKS 2010 software.
The functional requirements were established in the description of work. Values are:
- The pitch angle variation ranges between -40º≤φ≤70º . The lowest angular value has been enhanced and the highest has been slightly decreased compared to the initial requirements.
- Roll angle: -100º≤θ≤100º
- Tracker overall accuracy: 0.2º
- Target cost: 100€/m2
- Target weight 100kg/m2
In addition to these functional requirements, drive system (rods, bearings...) must withstand thermal expansions/ contractions derived from a temperature variation ranging from -20ºC to 60ºC.
Two designs were presented to the Consortium in order to be evaluated taking into account the following factors: size, weight, foundation, actuating system, redundancy, aesthetics and final price. Regarding that parameters the Consortium agreed with the most suitable configuration for INTENSOL objectives.
The design dual-axis tracker comprises next set of elements main frame, support legs, transmission mechanism, linear actuators and electric motors. Structural elements are all made from steel S275JR.
The Main frame has two main functions: to support the Main Frame transmitting the loads to the ground, and additionally it holds electrical motor platform. It has two main requirements: to permit modules (eight per frame) to be installed and rotated corresponding to pitch movement and to permit a roll amplitude rotation ranging from -100º to +100º. Main frame consists of two steel rectangular grid structures. There exist eight cells for each grid, corresponding with each module position. Each grid is supported by two legs which are fixed to floor trough a foundation. These elements provides main frame with the necessary elevation above ground in order to perform roll movement about its longitudinal axis.
Driven mechanisms consist in an electric motor responsible for performing roll movement and two linear actuators for pitch rotation. Different parts that compose the whole system are joined by means of rods and pins which make possible movement transmission between parts,
Dimensioning of tracking structure is based on a static finite element analysis, through evaluation of different load conditions by consideration of different orientation angles and wind velocities. Operational condition is based on a maximum wind velocity equals to 16 m s-1 and dimensioning is govern by maximum deformation criteria (point accuracy not less than 0.2deg). Survival condition is based on a structural strength requirement (maximum equivalent stress not exceeding material yield stress on any point of the structure) after consideration of a maximum wind velocity of 29 m s-1. Static wind loads (pressures) are derived from national standard “CTE SE April 99 “.
In order to select the actuators, multibody tests have been performed regarding the whole assembly properties (masses, inertias, etc.). Since the module centre of gravity is not defined, it has been estimated at 60% of the total module height. In order to analyse requirement for the roll movement (-100º - +100º) electric motor, an optimization process has been perform to adjust the centre of rotation. Taking into account the results of the optimization, the electric motor has been selected, with a reduction able to work with 1378 Nm and a peak load of 2300 Nm.
As with the roll movement, an adjusted design has been perform in order to get a design suitable for use commercial standard actuators. Finally LIMOSS MD120 linear actuator was selected, with a stroke of 600 mm and a maximum load capacity of 8000 N
The joints were selected taking into account the guarantee functional requirements related to accuracy, durability and expansion/ contraction due to thermal changes, without forgetting the cost and maintainability objectives.
Manufacturing process is one of the key factors to take into consideration along first stages in design process in order to avoid problems regarding standard components, supply sizes, stock availability.
3.4: Prototype manufacture and Lab testing
The ITAV low profile 16 modules tracker design was assembled at Insiralia and then shipped to Novamina.
To support its installation Inspiralia has prepared and send to Novamina a complete installation dossier composed by 26 pages with a full description of recommended practices for installation procedure.
WP 4: Advanced guidance and control system
Task 4.1 Modeling and Simulation
Novamina developed initial concepts of integrated calendar and time controller with solar sensor and these were modeled.
Task 4.2 Guidance and Control System Algorithm Design
Based on the initial methods for integrating timing and sun direction signals, an initial system was developed to control the linear actuators to be used on the tracker.
The INTENSOL control system is built upon three main control strategies fused in one hybrid.
From lowest accuracy to highest:
• High accuracy sun position calculation
• Sun sensor measurements
• Maximum output power measurements
Sun calculator and heliotrack controller give us accuracy under 0.2⁰, however due to mechanical imperfections of installed modules we need additional controller to get maximal power from cells. That is why MCPC controller was implemented in existing hybrid (Sun calculator-heliotrack) control software which is detailed explained in D4.1.
The control strategy is chosen based on feedback from the sun sensors: if the Heliotrack sensor is not sufficiently illuminated, the sun calculator will provide input for actuator controller. When insolation is high enough the Heliotrack sensor will take over control of tracker and finally when tracker is in a fully sun pointing position the MCPC will initiate fine tuning and take over control.
Additional safety measures were implemented to cover conditions which might cause damage to the system including water pressure, temperature measurements (to indicate problems with cooling), wind speed, snow load and electrical problems with the inverter and grid.
An easy to use graphical interface was set up to enable control of the final prototype tracker systems.
Task 4.3 Guidance and Control System Test
Tracking accuracy testing
One lens parquet was used due to easier handling. Namely, during pre-testing it was noticed that the lens should be covered to prevent overheated spots near secondaries when focus is not inside secondary (causing "burning" of gaskets and bottom plate coating.
Tracking accuracy was significantly improved (compared to result in the initial phase where accuracy was 0.5 an. deg) and the achieved value was better than 0.1 deg.
• Actuator regulation steps based on built in hall sensor is in-between 0.5 angular deg. Using additional outside sensor it is possible to get much more sensitive positioning.
• Changes in 0.5 angular deg moves lens focus on the edge of cell (consequence: Isc decrease for approx. 20 %)
• Additional 0.5 angular (total 1 deg), moves focus in the middle of secondary sloped side what had the result of decreasing Isc to 50 % ( related to Ics with focus exactly in the middle of cell surface).
In conclusion the tracking accuracy should be increased by using additional sensor (for eq. 4 coordinate sun sensitive sensor (= focus sensing) with moving sensing accuracy of 0.1 degrees in any direction).
WP 5: Integration into overall component
Package objective:
Based on works, reports referred in WP1-WP4 the Technical board defined final design, integration work details and prototype manufacture procedure. Mechanical assembly of all novel hardware components, all software component interface and system integration will be done and prototype will be completed. Procedures for future massive manufacturing process were optimized and delivered as manufacturing process technology report.
Task.5.1: Manufacture the Heat management system
Working drawings have been produced from concept design.
A Stand alone afterheating concept was designed. Cost analysis had shown significant un-feasibility of a fully integrated overall heating system if the afterheating were to be installed on the 2 axis tracker together with HCPV part.
Stand alone after heating concept gives more flexibility concerning combining of various different types of solar heaters (heat regines) heating up PV system cooling fluid in the second thermal circuit (by means of multi heating sourced pipe exchanger immersed in fresh water storage).
Manufacture Heat management system.
The heat management system was developed and prototype was built.
System involves the following control & executing functions:
• PV cells overheating protection (by means of PV cooling fluid temperature, flow and pressure measuring and acting function in order to run PV modules out of sun focus to prevent overheating and consequently cells destruction).
• PV cell cooling system control system can turn on by pass cooling circuit in case if there will be no secondary water consumption (and consequently no possibility to exchange heat of PV cells cooling fluid in fresh water storage)
Task 5.2: Manufacture solar collector system
PV solar modules were produced according to the production drawings provided by iXscient, these were delivered directly to Novamina.
The glass focusing lens panels supplied by Microsharp were assembled on the modules.
The fully assembled solar receiver units supplied by iXscient were mounted on the modules.
Tracking system elements produced by ITAV were assembled on site according drawings and assembly instructions.
Additional improvements on tracking system were performed in order to make fine adjusting of overall collector system on site.
Task 5.3: Control system SW, HW platform integration
Control and governing HW and SW system was assembled and integrated with mechanical part of PV solar collector system.
The control system manages and supervises all needed functions in order to assure overall system runs accurate and safe:
• running tracker according implemented 4 way governing algorithm (real time moving, tracker actual position tracking (mechanical position), sun focussing tracking (by means of 4 quadrant photo sensing feedback), maximum PV power point tracking of the all modules output in order to compensate any mechanical imperfection in tracking system (by means of current measuring and fine adjusting of tracker position to assure maximum of current
• assuring fast reaction in order to move out of fully tracked position (sun focus) in case of some overheating emergency.
• stowing modules to a safe position during night (and when system is exposed to some not-normal running conditions; e.g. high wind).
5.4: Transport components and assemble whole system in Croatia
All components were delivered to Novamina:
• Tracker
• Modules
• Receivers
• Lens panels
Novamina assembled and integrated the components with the actuators and control systems at its site in Croatia.
WP6: testing of all components, individual functions + overall performance
The full Intensol system was fully assembled at Novamina site at month 24. This was mainly due to the delays in the delivery of the receiver modules due a series of circumstances initially arising from the withdrawal of Quantasol from the project. However, in addition there were some issues with the tracker system in terms of mounting arrangements, and finally the weather in Croatia in December 2012 (and January 2013) was extremely poor and therefore no full testing at this stage of the intensol final prototype has been possible. However the consortium is committed to continue the activities on the system and run it operating in the spring and summer of 2013.
Industrial testing of performances was performed on partial sub-systems and overall PV collector system as well.
Testing period of PV solar system was during winter period under condition without direct sun light. Thus some tests were limited concerning obtained results.
Task 6.2: Industrial testing of performances and functioning of hybrid solar thermal system
Hybrid solar system was separately tested during the summer 2012.
Task 6.3: Industrial testing of performances and functioning of advanced guidance and control system
Control and governing HW and SW system functions were tested in order to prove tracking accuracy and emergency actions (based on incorporated features specified in task 5.3.).
To the lack of sun, there was no condition to test sun focussing tracking and maximum PV power point tracking of the all modules output in order to compensate any mechanical imperfection in tracking system (there was no PV output).
Guidance and control system testing passed successfully.
Task 6.4: Industrial testing of performances and functioning of the complete prototype
Overall tracking system functionality was tested (mechanical mowing parts and integrated guidance and control system).
Tracking accuracy was tested and some issues regarding improving in tracker design were noticed (e.g. transmission backlash in connection of some moving parts; module parallelism adjusting; etc).
Electrical performance and overall PV efficiency weren’t tested due to the testing condition.
6.5: Demonstration activities and Final Demonstration Event
A demonstration event for the Intensol system will be organized by iXscient and Novamina in collaboration with the SME partners for summer 2013, when the system is fully tested and debugged.
Potential Impact:
Impacts and Benefits
The 2 year period of the project (2011 and 2012) covered a very difficult period in the development of solar energy systems. In this time the cost per peak watt for standard PV system dropped from around 5.5 dollar per peak watt to just above 4US$. The cost for PV modules dropped from 1.85 to less than 1. This has been due to the massive growth of low cost Chinese PV modules makers. A number of large and small solar energy companies have ceased to operate as a result of these changes. In particular companies which have taken alternative routes (compared to standard silicon PV panels) have found it hard to provide systems that compete commercially, with full installed cost now approaching 4 dollar per peak watt. Concentrated Solar Power remains a difficult area commercially as large increases in supplied volumes are necessary to reduce costs, but these are difficult to achieve in competition with conventional PV. In addition concentrated PV can only be installed in areas of high direct solar and the major countries installing solar energy are still located in temperate climates – such as Germany – and this limits the use of concentrated PV.
The project aimed to achieve to main developments:
1. By using a liquid cooled HCPV system the levels of concentration compatible with efficient operation could be increased, or run at high levels (around 1,000 compared to the 300 to 700 representing the bulk of HVPV)
2. By utilising the increased temperatures from the liquid cooled HCPV some of the benefits of providing hot water in addition to electricity could be provided.
3. Finally the project aimed to provide a complete modular system which could be operated in small scale, industrial or potentially roof mounted operations.
The goal was also to incorporate technologies which had the potential, when scaled to large volumes, of reducing the costs to levels competitive with standard PV installations, with the hot water production as a value added product. These included:
• The production of the primary optics
• The design of the tracker system
Further work would be required to reduce the costs of the module boxes, for example by using mass produced plastics.
The project succeeded well in (1) above. Further changes to the system to increase the levels of solar concentration (and therefore decrease the overall costs of the system) appear to be very feasible since the qualty of the water cooling appears to be very good. Solar concentrations of around 1,200 should be possible, with primary lenses of around 40 cm by 40 cm. In terms of provided an integrated system which could deliver hot water at temperatures which are highly useful, for example 150 degrees C, the pure HCPV cooling system is unable to do this, as the PV cells would be operating at too high a temperature. The project had always anticipated this and additional solar thermal (concentrated or non-concentrated) were part of the design. An initial analysis showed that the solar thermal afterheaters did not represent sufficient value if they were included in the area on the tracker – a high cost resource. Therefore the 2-axis tracker was limited to the HCPV component. Simple, high efficiency flat panel solar heaters were adequate to raise the temperature to around 100 degrees, and concentrated 1-axis tracking system was useable for temperatures up to 150 degrees. Therefore the Intensol system can be seem as a modular arrangement consisting of the core HCPV system plus optional solar thermal components, which can be used in the following way:
• The HCPV system is used alone (no hot water production) and a passive cooling radiator is integrated in the water circulation loop
• The HCPV system plus a fixed array of high quality (double glazed or evacuated thermal tube) flat solar thermal panels are used and the system delivers hit water up to around 100 degrees C. This is sufficient for hot water and thermally driver cooling systems, for example for a factory, office or hotel
• The HCPV system is integrated with a 1-axis linear concentrator system to achieve temperatures of around 150 degrees. This is useable for industrial purposes such as heating and drying.
The Intensol system has a current total cost of around 11 dollars per peak watt installed (including tracker). This is more expensive than tracked flat panel PV. In order to become commercially viable the project therefore needs to perform the following activities (in addition to all the improvements noted as a result of small deficiencies in the performance of the system which will inevitably be noted over the course of the its testing):
• The overall bill of materials and assembly costs need to be reduced to approximately one third of its current value. A full installed cost price to the customer of 4 US$ per peak watt is required
• The performance of the system need to be increased as far as is possible, particularly by incorporating solar cells with highest performance. Currently Solar Junction provides such cells and these need to be tested and incorporated.
On the basis that these developments are achievable following the testing and overall redesign of the system, then Intensol system can be a viable alternative to flat panel PV and flat panel solar thermal for thee applications, particularly since it should utilise reduced installation areas, thereby maximising the benefit of e.g. limited roof area for industrial or commercial buildings.
Impacts and Benefits of the Intensol system
Clean energy using solar power systems is a politically desirable goal, since it provides electricity (and heat) with a definite cost structure over the coming years, thereby reducing uncertainties associated with cost increases in fossil fuel prices and the dependence of European economies on unstable or unreliable foreign suppliers
There are significant economic benefits to whole economies and to individual consumers of the use of cost effective and useful solar energy. It is anticipated that a combination of increases in fossil fuel costs and the introduction of carbon taxes or similar will make well designed and lower cost solar energy eventually (around the 2015-2020 time frame) cost competitive with energy from fossil fuels even without any specific subsidies
Development of quality, cost effective European solar energy systems will contribute to the economy and to jobs. Currently the PV industry appears to be moving more and more to China based on commoditised flat silicon PV panels. Solar energy based more on the types of technologies in the car industry and advanced wafer epixtaxy favour European production. Therefore, if the design of the Intensol system can be sufficiently cost engineered, there is great potential to perform the manufacture of the system e.g. in Eastern Europe with specific components from western Europe (e.g. the solar cells from IQE).
The approach of the Intensol system is such that it can be envisaged that a progressive set of technological improvement can lead to its continuing development to achieve lower costs and better performance. These include improvements in the engineering systems (electrical ,fluidic, heat management, tracker) . optical (better lenses and secondary) and solar cell (improved efficiencies). Therefore this type of system can be driver of technological improvements in Europe.
The Intensol system, being a source of solar electricity and heat, has environmental benefits with reductions in the emission of carbon dioxide (utilisation of carbon based fuels).
Clearly the level of such benefits relates to the installed volumes.
Overall all the anticipated results of the supply and uses of such systems is broadly beneficial.
Potential markets for the Intensol system
As detailed above, in order to compete effectively with flat panel PV and solar thermal systems given their very large decreases in costs over the last 2 years, the Intensol system need to be cost engineered to reduce it (in volume) installed cost to around US3.25 per peak watt. This is the target in the original proposal. The approximate power output of the single module Intensol system (when fully engineered and including state of the art triple junction cells) is 7.5 kW. Therefore the installed cost of the single module system needs to be around $US25,000 (19,250 euros). The current bill of materials and assembly price is estimated at $US88,000 (single prototype) and therefore a price reduction to less than a third is required. With appropriate changes and the required volumes this still anticipated to be possible.
The target market for high concentration systems will always be reduced compared to flat panel PV as they require installation in regions with a very high proportion of clear sky days, and (as with all solar systems) their economics improves with the annualised solar intensity at a location.
Suitable locations including Southern Europe (Italy, Spain ,Greece, Croatia) and non European countries such as North African and Middleastern countries. It is anticipated that the in general the electrical power and hot water provided by the systems will be consumer locally. The target types are:
• Industrial, such as production facilities
• Offices
• Hotels
• Public sector facilities such as Hospitals
• Combined heat and power facilities (integrated with other power sources) for denser residential developments
The major changes in the solar PV and energy markets of the last 2 years have made predictions of sales difficult, at this stage the consortium is intent on determining the ability to cost engineer the Intensol system to the required target. It is felt that with this achieved, plus data on the system operation, installation in hotels, industrial sites and offices should be possible, with sales building over a period of time of perhaps around 5 years. It is currently anticipated that a further 24 months of development is required.
Customer pay back period. The pay back period for installation of an Intensol system at the target price is still anticipated to be between 3-5 years, depending on grid electricity prices.
Benefits to partners. The achievement of the final Intensol system with lifetime, performance and cost meeting the current targets, would achieve significant benefits for the partners:
• Ability to supply components to the system
• Sales and income from system sales
• Retention and increase in jobs
Actual values will depend on the cost targets achieved and the state of the solar PV market in the years ahead, which is highly unpredictable (as judged by the last 2 years).
Dissemination and Exploitation
Discussions were held with both the SMEs and RTD partners to ensure that concepts developed during the programme would be fully protected.
Microsharp developed and filed a new patent within the project covering a solar thermal hybrid system: Solar Energy Apparatus. However search reports and evaluation by the EPo indicated that there was prior art making it difficult to develop an acceptable patent. In addition the patent itself covered an integrated PV and thermal receiver and evaluation within the project had indicated that the thermal component of the system should be separate (and not mounted on the tracker at all). The patent therefore had ceased to reflect the actual designs within the Intensol project. The patent was therefore dropped.
Microsharp and iXscient carried out an evaluation of the different components of the system with regard to protection.
The following system element dissemination was performed to partners:
Cell bonding process from iXscient to Microsharp
Receiver design from iXscient to Microsharp/Emergo/Sadel
Module design from iXscient to Microsharp/Emergo/Sadel
Low profile tracker design from Inspiralia to Microsharp/Emergo/Sadel
Control system including algorithms and software from Novamina to Emergo/Sadel (plus Microsharp)
Liquid cooling HCPV system from Novamina/iXscient to Microsharp/Emergo/Sadel/IQE
Overall system including solar thermal elements from Novamina/iXscient/Insiralia to Microsharp/Emergo/Sadel/IQE
Dissemination of the results through papers and press has been limited in this project, since the partners have been developing a system of commercial value and the project partners have, at this stage, mostly have Ip retention on the basis of know how, potetial designs and trade secrets. However in the coming year strong efforts will be made, on the basis of the completed performance of the system, to perform this dissemination.
Future funding & investment plans
Discussions between the SME partners: Microsharp, Emergo, Sadel and Einvest indicated the following roles in developing the Intensol system for funding and investment:
Microsharp and Emergo to complete initial aspects of exploitation plan in terms of completion, debugging, modifications and testing of the Intensol system, along with a detailed further analysis of how to reduce costs to one third of initial prototype costs
Sadel to evaluate the further markets and installation prospects of the system given the very fast changes the PV and solar energy market is undergoing at the present time
Eninvest to explore potential in Easter Europe including funding and investment arrangements.
IQE to assist in integration of state of the art, advanced high concentration solar cells
The goal is to bring together the completed system along with the changes required for cost reduction with a renewed market analysis (as of 2014-2015) to enable investment and initial installations of small systems.
Exploitation planning
An exploitation plan has been completed.
Currently the cost of the system per peak watt is only just in the ball park of being able to sell, so long as the cost decreases with volume are real. Therefore there is a need for the system to:
1. Be restructured to decrease the cost targeting reductions to achieve around a full installed cost of $US 3-4 per peak watt
2. Be improved to increase the power output via better optics (with increased concentration ratio) and improved solar cells – contacts are already underway with Solar Junction to source their 44% efficient cells
3. Generate a set of test results to enable focussing on the key areas for improvement and begin to provide the information needed for the investors and users of the system.
Set of activities and time line
Firstly the consortium will explore again the balance between PV only passive cooled system compared to PV/Thermal liquid cooled systems – is the benefit of e.g. 50-60 degree hot water sufficiently beneficial, is there a genuine benefit to liquid cooling to get concentration factor up, is the danger of catastrophic damage sufficiently under control (tracker to rapidly move out of solar focus). This will determine the specific role of a combied concentrated Pv and thermal system with liquid cooling.
Practical activities:
1. Modify the tracker to overcome and correct all problems associated with tracker design and arrive at a consistent solution and design including reductions of mass
2. Modify and put into full implementation the cooling system
3. Connect the system with the inverter and connect it to a load and monitor over a period of time
4. Extend adapt and complete the control system, including full documentation of the algorithms, sensors, control issues
5. Test all the components over the summer of 2013
6. Explore all the components of the system to identify designs which reduce costs of each element
• Module design integrated with the fluidic back plate
• Plastic module
• Modified tracker
7. For PV - continue discussion with Solar Junction to full identify a costed upgrade to the receiver operating with 44% efficient cells
8. Build next prototype based upon improvement in system – increased efficiency and reduction in price, and re-evaluate with respect to commercial outcomes – need to achieve an installed peak watt price of <$US4.
List of Websites:
www.intensol.eu
Main contacts:
Ernest Vlacic: Emergo:
ernest.vlacic@emergo.hr
Nicholas Walker: Microsharp: n.walker@microsharp.co.uk: +44 7788583376
The Intensol project set out to develop a hybrid solar PV/Thermal system based upon high concentration PV with liquid cooling and a solar thermal ‘afterheater’ concept for the integrated supply of electricity and hot water.
The system is based on the development of novel cost effective Fresnel lens based concentrators working with liquid cooled triple junction PV cell technology. Product will be equipped with integrated liquid cell cooling and heat recuperation system, positioned by high accuracy two axes tracking system and guided by an adaptive control system. It enables energy output optimization (electrical and thermal), maintaining the solar cell temperature and thermal fluid temperatures at optimal levels for the required output and insolation conditions.
All components and systems have been integrated and optimized as an autonomous unmanned cogeneration power plant unit in a form of new commercial product, the INTENSOL. INTENSOL is therefore a development of the following combination of key innovative technologies:
• Cost effective Fresnel lens based concentrators
• Triple junction cells (TJC)
• Solar cell Heat management, TJC cooling and additional heat recuperation system
• Optimization process for electrical and thermal power output
• Highly accurate low profile two axis tracking system
• Advanced guidance and control system
The project developed a number of intermediate prototypes but has completed with a integrated final prototype installed in Croatia incorporating:
• Novel low profile 2-axis tracker
• Glass Fresnel lens panels based on a roll to roll manufactured PMMA Fresnel lens laminated using a novel approach to solar glass panels
• Liquid cooled individual high concentration solar cell assemblies based on a CPU cooler approach optimised to minimise the thermal gradient from solar cell to cooling liquid and able to highly effectively cool cells at solar concentrations of 1,000
• Control algorithms integrating clock based high accuracy solar position estimation, sun sensor and maximum power output fine tuning, with specific safety conditions particularly associated with ensuring cells are always actively cooled when on sun
• Optional after heaters based on either high efficiency flat solar thermal panels or medium concentration solar thermal system
Project Context and Objectives:
The objective of the Intensol project was to develop an efficient and cost effective solar energy system for combined electrical and thermal energy production that uses direct solar radiation as the primary energy source.
In order to achieve those objectives the consortium developed a combination of a state of the art liquid cooled High Concentration PV Solar System which is based on a combination of the latest developments in high concentration optics and photovoltaic technology along with solar thermal components (fully integrated liquid cooling for the PV cells minimising the thermal gradient), showing the system can be put in series with a number of modular solar thermal systems (flat panel, low low to medium concentration) resulting in a product that is able to produce electricity and heat from one integrated system.
The system is based on the development of novel cost effective Fresnel lens based concentrators working with triple junction PV cell technology. Product will be equipped with integrated liquid cell cooling and heat recuperation system, positioned by high accuracy low profile two axis tracking system and guided by an adaptive control system integrating control of the tracker, electrical nad thermal systems. It should enable energy output optimization (electrical and thermal), maintaining the solar cell temperature and thermal fluid temperatures at optimal levels for the required output and insolation conditions and ensuring system safety at all times.
All components and systems will be integrated and optimized as an autonomous unmanned cogeneration power plant unit in a form of new commercial product, the INTENSOL. INTENSOL is therefore a development of the following combination of key innovative technologies:
- Cost effective Fresnel lens based concentrators
- Triple junction cells (TJC)
- Solar cell Heat management, TJC cooling and additional heat recuperation system
- Optimization process for electrical and thermal power output
- Highly accurate low profile two axis tracking system
- Advanced guidance and control system
The ultimate goal is to achieve all this whilst seeking a target installed price of around 3-4 euros per peak watt.
Project Results:
Summary
Technical progress and achievements
1. A detailed evaluation and design exercise was conducted, including full system evaluation, optics design, spectral radiation evaluation and load and thermal modeling.
2. The HCPVT cooler block was evaluated and several designs implemented and evaluated. A low cost arrangement was designed meeting the requirements, based on CPU cooling units design. An final overall receiver arrangement was constructed with a low thermal path between cell and the top copper block of the liquid cooler, using thin solder layers both between the cell and a high thermal conductivity ceramic receiver (on which the electrical connections and bypass diode were mounted) solder bonded to the copper block forming the top part of the liquid cooler.
3. The primary optics were designed and fabricated and supplied to partners, in PMMA panels bonded to a PMMA support for prototype 1 and in glass panels for final prototype – both in a 3 by 1 lens arrangement with 350mm square Fresnel lenses. The primary Fresnel lens optics were produced using a roll to roll production process, and the lens film was laminated using a solvent bond process to PMMA sheet (in prototype 1) and using a novel UV cured low weathering silicone adhesive formulated by Microsharp to solar glass (in the final prototype),
4. A range of secondary optics were evaluated including silicone and glass designs. A reflective secondary was supplied for the initial prototypes and an improved reflective secondary optics for the final prototype based on evaluations for relative costs and performance
5. 40 receiver modules were supplied by Quantasol along with operating data for the first prototype. 7 cell wafers were supplied by IQE for the final prototype which were converted (electrode added and diced) by CESI into approximately 250 cells and mounted (solder bonded) on aluminium nitride ceramic plates (integrating electrodes and bypass diode) by Aurel. These ceramic plates were in turn solder bonded onto machined copper blocks (the top component of the liquid cooling assembly) by Aurel and in turn the copper blocks were integrated into a full receiver module by iXscient
6. A two axis, low profile, tracker was constructed by Novamina for the first prototype. ITAV designed, simulated, optimized and constructed a large, low profile, tracker for the final prototype which was delivered and assembled at Novamina in Croatia
7. The ITAV first prototype module, with a Novamina designed liquid cooler and integrated receivers was assembled and tested in Croatia using the Novamina tracker
8. The iXscient first prototype module was constructed and tested at Microsharp on its central pole tracker in the UK
9. Xscient designed an aluminium module for the second prototype, incorporating 4 units of the 3 by 1 lens array and 12 receiver modules. A first example was constructed in Uk and delivered to Microsharp, the final 16 modules constructed at Novamina
10. The final prototype was assembled at Novamina in Croatia incorporating:
• The low profile tracker from ITAV
• The aluminum modules (16) with integrated glass primary optics, receiver units from iXscient
• Tracker actuators and control system, plus electrical and fluidic connections and management from Novamina
WP 1: Development of high concentrating Fresnel lens based on low cost optical film
Task 1.1 Optical Design Specifications
ITAV, Novamina, Microsharp and iXscient cooperated in developing the overall system design, including generic issues relating to balance between heat and electrical outputs, generic CPV design issues and some specific aspects of the INTENSOL design. This work is detailed in Deliverable D1.1.
iXscient and Microsharp cooperated in the development of the specifications for the system optics. These were derived from the overall system specifications and design developed by the consortium and written up in deliverable: D1.1: Specification and Design document. In general, from the point of view of the optics, the necessary elements include:
• The size of the system optical units should be small in number and each large in size in order to minimize the loss of energy that would result from an increase in the number of units and decrease in size – this follows from volume and surface area considerations.
• The concentration ratio should be high since we are able to actively remove heat using liquid cooling and therefore in order to maximize the flow of heat and minimise the overall system costs, a concentration level of around 1000 should be sought.
As a result it was decided to produce a lens which would achieve (at 80% efficiency of the optics) a 1000 times solar concentration on a 1 cm by 1 cm cell (this is a standard size for the triple junction cell industry).
The maximum size that a lens master can be constructed is around 500mm diameter (this is due to constraints on the cutting machine that Microsharp have access to). This can generate a lens 350 mm by 350mm. The final solar concentration should therefore be approximately 900-1000 times.
Choice of Lens Focal Depth
The lens design requires a choice of focal depth. Generally as the focal depth increases the efficiency of the lens increases, but the total materials required for the module increases and the off axis tolerance decreases. Therefore as short a focal depth as possible consistent with a good performance is required.
The calculations for the efficiency of the lenses takes into account:
• Reflective losses from the front surface of the film, which increases with angle of the lens to the light
• Refractive losses (Fresnel losses) from the prisms at the back of the lens
• Losses that arise from manufacturing issues at the facet apex resulting in non-optical performance of part of the prism facet – in this case two manufacturing approaches are examined – a half radius tool and a full radius tool. The full radius tool (of between 1 and 3 microns) is the more accurate to actual manufacturing practice
• The proportion of light with wavelengths from 300nm to 1600nm falling inside the target collection size (see above)
A focal depth of approximately 45 cm was therefore recommended.
Optical Design and Simulation
Based on this initial focal depth estimate, Light Tools (a ray tracing software package) was used to optimize the design of 350 by 350mm lens, seeking to jointly maximize the efficiency whilst minimizing the focal length. An additional ray tracing software package, TracePro, was also used.
The efficiency of the lens (in fact total optical set up including secondary) is extremely important as a wide off axis angular tolerance enables easier module assembly and lower tracker accuracies.
Off-axis angle(°) 0, 0 0, 0.5 0.5 0.5 0, 1 1, 1
Efficiency (%) 80.89 79.56 78.10 69.27 60.83
Efficiency at Different Off-axis Angles
The simulations show good results and therefore the lens design was finalised.
Choice and Selection of secondary
A wide variety of options for the secondary optics in the system were considered, including glass and silicone secondaries. Following examination of the cost and relative performance options a simpler alternative of a wide tapered reflective rectangular secondary was selected, since this was a low cost and simple option.
Table 1: reflective secondary parameters (final prototype)
Exit size 1 cm
Entry size 5 cm
Height 5 cm
Slope angle 26.5 degrees
This design has the benefit of being simple and cheap (costing less than 30 Euro cents in volume).
Quantasol analysis of location spectral conditions
In order to understand the requirements for the spectral performance of the system (optics, solar cell), Quantasol performed a spectral analysis of the target Croatian location and related this to specific designs of triple junction cells which could optimally perform in this location.
In conclusion, it is possible to increase annual power output by around 6% by choosing a triple junction cell which matched to the target spectral balance.
Following the withdrawal of Quantasol from the project IQE provided fairly basic triple junction cells for use in the project. However an introduction was made with their partner company Solar Junction and discussions indicated that cells with efficiencies of approximately 44% could be sourced in the near future, which exceed even the performance of the optimized Quantasol cells.
Task 1.2 Exploration of outer surface coating for AR, anti-scratch and self-cleaning
A review was undertaken by iXscient to examine possible beneficial coatings for the primary optics. Several problems affect CPV lenses which reduce their efficiency. These can be listed as:
1. Reflection of the top flat surface
2. Reflection of the Fresnel (underside) facets
3. Water droplet condensation on the top surface
4. Water droplet condensation on the Fresnel facets
5. Dust and sand blown scratching on the flat outer surface
6. Dirt, dust and organic residues deposited on the outer flat surface which block the light
For antifogging coatings, no coating with suitable lifetime were identified. No cost effective solutions were identified for antiscratch, but the development of a lens film to glass lamination process by Microsharp obviated this issue, provided any further coatings were scratch resistant.
For AR coatings, only single layer coatings were considered due to cost and lifetime issues. Three types of coatings are potentially useable:
• Sol-gel coatings
• Khepricoat (DSM)
• Solarphire (PPG)
These coatings are only applicable to glass. In the final Intensol prototype detailed discussions were held with the suppliers of Khepricoat (DSM), which has been developed for standard PV panel outer surface. It retains the scratch resistance of glass. Costings obtained indicate that this is a cost effective solution for improving the performance of the primary optics.
Since the optics are tracked with regard to the sun, the total transmittance of the planar glass is increased from around 93% (flat glass reflection) to over 96% (a 3-4% improvement in transmission).
In conclusion for the final prototype of the INTENSOL system, glass based optics were used and Khepricoat is the chosen solution for outer coating.
Task 1.3 Lens prototype fabrication and testing
Development and Manufacture of Lens
From the lens design parameters, a master disc was diamond cut on a copper blank for the large flat lens design. Plastic replicas from this master were cast directly for testing, and for nickel electroplating to form the manufacturing shim.
Lens Testing Setup
iXscient conducted a detailed appraisal, in collaboration with Microsharp, of the components and setup needed for improvement to Microsharp’s lens testing arrangements.
This work was summarized in deliverable D1.2: Lens Test Report
Lens Testing on Final Primary Optics
This is summarized in deliverable D6.1 Industrial testing of performances and functioning of the Fresnel lenses with two axis tracking function . The final glass assemblies are around 77% efficient and have an acceptance angle on the final receiver assembly of around 0.75 degrees.
Task 1.4 Development of lamination for 3D lenses
The lens films are manufactured using Microsharp’s standard UV microoptics roll to roll production system. A base film (250 micron thick PMMA from Evonic) is coated with a thin layer of a specific UV curable acrylic resin specifically developed and optimized at Microsharp to achieve long lifetime under solar weathering conditions. The coated sheet is exposed to UV radiation when in contact with a moulding drum on which the mould for the 3 by 1 lens is mounted. The cured, cast optical structure is wound as a sheet.
For the first prototype the resulting film was cut into 3 by 1 sheets and solvent bonded onto 3mm PMMA sheets using methyl chloride in which 5% acrylic had been dissolved. The resulting sheets where aligned to the lens centres and the edges laser cut to achieve correct positioning of the lenses on the sheets (with respect to the edges).
For the final prototype the lens films were laminated to optical glass sheets (precut and beveled to correct size). The lamination process used a UV curable silicone adhesive specifically developed by Microsharp to enable long lifetime of the resulting laminate based upon excellent solar weathering for the silicone and the preservation of a flexible join between the film and the glass to enable differential thermal expansion.
To achieve the lamination on the glass, since the glass sheets could not be edge cut to enable correct positioning post lamination with respect to the lens centres, the following steps are taken:
• The glass is coated with the silicone adhesive
• The film is laminated on the glass using pressure rollers
• On a specially constructed jig, the film is moved to align the lens centres with their correct positions with respect the glass edges
• The resulting sheet is exposed to UV light to cure the silicone adhesive
In a final production process, it is anticipated that a glass edge cutting process, for example using laser scribing and breakage or water cutting, would be employed to speed an automated lamination process with an automated method for finding the lens centres.
For the final prototype 64 of 3 by 1 glass panels were manufactured and delivered.
Task 1.5 Finalisation of automated manufacture/Production of lens parquet/Full production lens parquets for system
First Prototype
The lens masters were nickel replicated into 3 lens replicas and joined using laser welding into a 3 by 1 shim. This was mounted on a large diameter production drum and film was manufactured by Microsharp and subsequently solvent bonded onto 3mm PMMA sheet using the solvent lamination process.
Final prototype
64 Laminated glass lens panels were produced, checked and shipped to Novamina.
Task 1.6 Sourcing glass secondaries and development of bonding to cell/Demonstration of optics (efficiency, angular tolerance) in simulated and actual sun
Experimentation with cast silicone secondaries
Some initial experiments were conducted with casting solid silicone secondaries from novel silicones supplied to Microsharp with long lifetime and high solar intensity survival.
Following an analysis of glass secondary performance and costs, an improved reflective secondary design was retained for the final prototype.
Tests were carried out on the performance of the final glass primary lens working with the completed final receiver design.
The lens was measured for proportion light on target across the lens using a collimated white light source and the standard silicon photodiode arranged within a 1 cm by 1 cm aperture with the reflective secondary mounted around this aperture.
The resulting integrated performance for a square lens is 79% (73% for round lens).
This is sufficiently close to the 80% target to be acceptable.
Measurements of a silicon photodiode 9rpelacing the triple junction cell) were carried out on the final receiver arrangement with collimated on-axis light
Condition Test 1 Test 2 Test 3
No concentration 24 (3) 33 (3.5) 35 (3.5)
Concentration, with attenuation filter 225.3 (11) 311 (14) 333 (15)
Estimated solar concentration 939 942 951
The results are a little down on the estimated concentration of 968 (79% efficiency). The efficiency estimate from these test is 77% efficient.
Off axis relative performance was measured (again using the open circuit current of a silicon photodiode replacing the triple junction cell):
A maximum off axis tolerance angle of 0.75 degrees is suggested.
WP2: Development, design of a hybrid solar thermal system integrated in the HCPV
Task 2.1: Detailed definition of operating parameters, thermo-physical properties
ITAV provided a detailed investigation into the alternatives for operating parameters of a solar system producing both electricity and power, predominantly based on the use of triple junction cells. The results are included in the report D1.1 Specification and Design document.
Task 2.2 Design of Heat pipe cooling of concentrating PV cells
Following the design and specification exercise, including costings for heat pipes system and individual liquid cooling blocks, it was determined that, for a 10mm by 10mm cell operating under 1000 times concentration, the optimal approach was a single block for each cell. Therefore the core work activities in this area related to the design and testing of individual thermal blocks.
Quantasol provided initial details of the anticipated receiver on which the solar cells will be supplied to the partners. For the final prototype IQE provided details of the cells it supplied, which are similar but with somewhat reduced efficiency (34% instead of 39%).
Quantasol supplied 40 receiver units to iXscient (10mm by 10mm solar cells bonded onto ceramic receivers with bypass diodes). The cells had bonded glass cover slides.
IQE supplied sufficient cells to achieve 250 receivers for the final prototype. These were solder on ceramic bases which in turn were solder bonded on copper blocks (the top part of the liquid cooler).
Novamina Activities
Exploration using commercial CPU cooler block
Initial investigations into cell/receiver cooling used a transistor which simulated receiver under solar heating supplying heat which should be dissipated from the cell (receiver-a) at maximum insolation I=1000 W/m^2. The transistor was cooled with a commercial “Zalman“ water block for CPU cooling and cooling water flow was achieved using a water pump . The aim of the experiment was to determine the temperature of the transistor housing at a given flow, inlet water temperature and transistor power which represented receiver heat dissipation.
Measurement setup consisted of an electrical part (which served to generate heat through transistor power) and transistor cooling.
Conclusion
The ultimate goal of the experiment was to show that the selected cooler can dissipate heat from the receiver HCPV cell/receiver at maximum insolation with given water flow and thereby maintain the temperature of receiver / cells to approximately 50 οC. The results showed that the selected lquid cooler can, without any difficulties, dissipate heat with minimal increase in outlet water and transistor temperature. To be closer to the receiver temperature of the 50 οC significantly lower flows or greater cooling water inlet temperatures are required. Thus we can conclude that this type of water cooling is more than satisfactory for our HCPV cell but considering its high price (about € 40) and some other defects (difficult to isolate, assembly etc.) we concluded that it is necessary to seek a simpler and cheaper solution.
The next solution was simple aluminum made water cooler/block. Shape and dimensions were derived from the thermal analysis using finite element method according to the following design criteria:
• Geometry which allows easy isolation
• Simple production
• Expenses (material+production)
The aim was the same as for CPU water block cooling simulation and we used exactly same measurement line and procedures.
Description of aluminium water cooler
Cooler was made of one piece machined 30mm Al6063 rod with a cylindrical flow chamber.
Conclusion
The ultimate goal of the experiment was to show that the selected aluminium cooler can dissipate heat from the receiver HCPV cell/receiver at maximum insolation with given water flow and thereby maintain the temperature of receiver / cells at approximately 50 οC. The results showed that selected cooler can without any difficulties dissipate heat with minimal increase in outlet water and transistor temperature. Thus we can conclude that this type of water cooling is satisfactory for our HCPV cell cooling because we can maintain our cell/receiver temperature at temperatures 11 οC higher than inlet water temperature with given flow and heat dissipation (at highest insolation). This solution is cheap, simple and easy to manufacture.
New Cooler Design
Following the initial work and results of feedback from iXscient on the use of the Alphacool commercial CPU cooler, a new design including flow channels, was developed.
Conclusion
Some thermal interface material has to be applied fulfilling the following criteria:
• Has to sustain properties for long time (for eq. more than 10 years); thermal pastes used for CPU cooling aren't appropriate due to limited condition usage (normally indoor conditions) and limited lifetime (in average 2-3 years and then has to be exchanged).
• Has to be applied in as thin layer as possible
• Thermal conductance has to be as high as possible ( > 1 W/mK)
It is not possible to determinate cell temperature under certain radiation due to several reasons:
• Electrically loading the cell changes heating of cell (and temperature)
• Variation in sun radiation changes cell heating (- temperature)
Possible method is to determine maximal cell temperature is to fix receiver on the particular cooler, heated it up by means of calibrated light concentration and measuring Voc, determine cell temperature under different concentration.
iXscient activities
In parallel to the activities at Novamina, iXscient sourced CPU coolers from Alphacool which used a microchannel array. Each cooler cost approximately 8 Euros.
Enhanced liquid cooler for final prototype
Based on the liquid cooler design from Alphacool and the experience of the need for a permanent high thermal conductivity bond between the receiver and the cooling element, iXscient developed a completed final receiver design including the following features:
• The triple junction cell remains solder bonded to the ceramic base, as in the first prototype
• A high thermal conductivity ceramic is used (Aluminium Nitride)
• The ceramic based is solder bonded to the machined (microgrooved) copper cooling block, i.e. the top part of the liquid cooler
• The base of the liquid cooler is integrated into the receiver arrangement, incorporating a base plate to attach to the overall enclosure module, the back part of the liquid cooler and elements to support the electrical and fluidic connections plus the secondary optics
Task 2.3: Design of Heat Pipes Thermal Transfer Systems and After heater
The previous analysis had indicated that an arrangement linking several receiver modules to a liquid cooler using heat pipes was not cost effective or thermally acceptable and that individual liquid cooling units were preferentially mounted on each receiver. Therefore the heat pipe design and analysis was not pursued after this initial analysis. As detailed above, effective individual liquid cooling units were designed for each receiver.
The preferred thermal arrangement consists of an input cooling liquid temperature of around 30 degrees and an output temperature of around 50 degrees from the high concentration PV units alone.
The goal is an output temperature of between 100 and 150 degrees. It was determined early in the project that the costs of tracking a solar thermal unit on the tracker built for the HCPV units was too high (the tracker area was better served by fully covering with the HCPV units), and that therefore two alternative arrangements should be considered:
• Efficient flat plate solar thermal units are run in series (after) the HCPV, to achieve final temperatures of around 100 degrees
• A separate 1 axis tracking solar concentrator system would be used to achieve final temperatures of around 200 degrees
Both systems were evaluated in WP6.
Tasks 2.4: Prototype manufacture and Lab testing
iXscient Testing
1. The receivers were mounted in the iXscient module and the module was left to track with no active cooling for several sunny days. Unfortunately the cells underwent runaway thermal destruction.
The bond between receivers and cooling block was examined and appeared to be only partial. It was changed from the silver thermal paste to a single part thermal epoxy.
A decision was made to only expose the unit to sunlight when active cooling was being undertaken. A black plastic cover was used to prevent light entering the unit except when the pump is working.
The system is mounted on the Feina tracker which achieves a good tracking and the light was observed to be within the secondary at all times.
In the following the fan rate was put at maximum in order to maximally cool the incoming water. The temperature achieved was 29 degrees (ambient 28 degrees).
Pump Rate Block Temp In temp Out temp Voc
10 31 29 31 8.65 – 70 degrees
1 41 29 38 8.45 – 75 degrees
When the pump was halted, the block temperature reached 75 degrees (alarm condition) within 10 seconds. The pump was then restarted and at full pump rate the block temperature reduced rapidly (within 10 seconds) to 32 degrees.
In conclusion, the liquid cooling block is sufficiently efficient. The current issues arise from the thermal gradient from cell to cooler block and this needs to be adequately addressed.
Full cooled receivers mounted in testing module
• Two cells were mounted in module and connected in serial connection and one cooling line (1st & 2nd position from the left)
• The third receiver in line was replaced by a cell simulating element (aluminum plate for cooler contact surface temperature measuring)
• Thermo couples were placed on the water inlet, outlet and on the simulating element
• Water flow was 4 l/min
Testing phase no. 1: Tracker accuracy & cooling efficiency
Performing period: September 2011 - starting date 12; - ending date 16
Testing condition:
- absolutely clear sky (no cloud at all during testing period)
- air temperature: 30 - 33 deg. C
- wind velocity: 0 m/s
Results indicated excellent control of the cell temperatures but high thermal gradient (around 30 degrees),
Afterheater using medium concentration linear solar unit
A linear solar concentrator was assembled with an Archimedes solar receiver tube.
Due to the weather the system was set up but not tested under solar conditions.
System simulation
Simulations were conducted for one day in July using Matlab Simulink tool. HCPV coolingsystem was modelled according to the real prototype. Input parameters were:
• Optical efficiency: 0,85
• Electrical efficiency: 0,35
• Aperture area: 1,01 m2
• Ethylene/Glycol 60/40% mixtureNine cells cooling loop connected in serial configuration were simulated with constant inlet temperature of 25°C and insolation for the average day in July for Zagreb, Croatia.
Three scenarios were simulated:
• After Heater with only vacuum tube without tracking and secondary mirror with optimum season angle
• with secondary mirror (CPC type collector) with optimum season angle
• with single axis tracking with Fresnel lenses
• (all three simulation s were conducted with one vacuum tube 4.06 m long)
• Tube optical efficiency is 0.7 and heat loss coefficient is Ul=20 W/m2K (mean value).
• Mean ambient temperature Ta=25°C.
After Heater with only a vacuum tube without tracking and secondary mirror with optimum season angle
• Tube absorber surface is Ap= 0, 88 m2
• Mass flow rate is qm= 3kg/mi
Increase in heat transfer fluid temperature is around 3°C for peak periods which is very poor considering targeted temperatures. Temperature can be increased by reducing the flow rate but that would result in lower effectiveness of HCPV cooling and higher cell temperatures.
After heater with secondary mirror (CPC type collector) with optimum season angle
• Effective aperture area is Ap=4,4 m2
• Concentration ratio is C=5
The secondary mirror significantly improved HTF temperature increase. In this case it is around 14 °C. It is important to mention that flow rate was set at 3 kg/min because that is the usual value for low temperature solar systems. Higher flow rates for medium-high temperature applications are higher.
After Heater with single axis tracking with Fresnel lenses
• Effective aperture area is Ap=19,3 m2
• Concentration ratio is C=22
As was assumed, best results were obtained for system with single axis tracking. In insolation peak period temperature increase was around 22°C with 10kg/min flow rate.
WP3: Development of concentrator panels with two axis tracking Function
Task 3.1: Material definition and design properties of light weight concentrator module
Both ITAV and iXscient developed first prototype modules in order to mount and test the receivers, coolers, and tracking arrangement. ITAV developed a 3 by 3 unit and iXscient a 1 by 3 unit.
iXscient designed the 12 receiver unit aluminium module for the final prototype.
ITAV First Prototype Module
ITAVs design was based on a framework of aluminium spars, using standard aluminium extrusions. The sides were of glass and the bottom aluminium.
The following shows the weight budget of the ITAV module:
Aluminum profiles 34 Kg
Aluminum walls and bottom sheet 18 Kg
PMMA lens and support 6 Kg
TOTAL 58 Kg
Aperture area 1,16m2
Aperture area / total area 0,725
Mass / total area 36,25 Kg/m2
The unit was built, including optics supplied by Microsharp/iXscient, and sent to Croatia.
iXscient first prototype module
The purpose of the iXscient module was to develop (over the course of the project) improved primary and secondary optics, and characterise their performance in terms of electrical and thermal behaviour.
The overall unit is a 3 by 1 arrangement. The receivers are liquid cooled using standard acquacool CPU cooling units. A computer liquid cooling pump, reservoir and cooling radiator was used to perfuse the unit.
The unit was delivered to Microsharp (with Microsharp optics integrated) and mounted on its current commercial (Feina FP9) tracker at its site in UK.
Final Prototype Module
iXscient designed the final prototype module to take the glass primary optics and the receiver modules.
A square box system including supports for 4 of 3 by 1 glass lens panels, and the polycarbonate plate elements was completed. One prototype was supplied to Microsharp and 18 modules to Novamina.
Task 3.2: Two axis tracking system actuator system design
The tracker design needs to take into consideration the requirements from the DOW:
1. Tracking in two axis:
• East-West rotation: -100° to 100° (azimuthal)
• Inclination: -10° to 75° (zenith)
2. Tracking pointing accuracy below 0.2°
3. It has to be modular to carry a variable number of modules. Maximum module area 30 m2
4. Control, Guidance – Predefined trajectory with optical sensor in internal closed loop
5. Safe position for standing high speed winds (up to 25 m/s)
6. Temperature range: -20 to 60 °C
7. UV resistant
8. Not add too much mass of the system, thereby reducing pointing accuracy or increasing the costs of the tracker (Overall mass per square meter, tracker plus modules?)
9. Be highly reliable, not compromising the overall lifetime and operating uptime of the system
Novamina designed a single module tracking unit for the first prototype and ITAV a low profile 18 module 2 axis tracker for the final prototype.
Task 3.3: Inclined support and rotating carousel design
The initial Novamina Tracker design consisted of 2 moving frames in total balance (no rotation moment due to weight of frames containing the CPVT module). Movements were implemented by means of 2 linear actuators and chain drive.
Inspiralia final prototype tracker design and construction
The work of INSPIRALIA during the second period has been focus on the mechanical design of a dual-axis tracking system. The final design fulfills functional specifications together with a cost effective design taking into account a future industrial production. The mechanical analysis has been performed with a CAE software, particularly with SOLIDWORKS 2010 software.
The functional requirements were established in the description of work. Values are:
- The pitch angle variation ranges between -40º≤φ≤70º . The lowest angular value has been enhanced and the highest has been slightly decreased compared to the initial requirements.
- Roll angle: -100º≤θ≤100º
- Tracker overall accuracy: 0.2º
- Target cost: 100€/m2
- Target weight 100kg/m2
In addition to these functional requirements, drive system (rods, bearings...) must withstand thermal expansions/ contractions derived from a temperature variation ranging from -20ºC to 60ºC.
Two designs were presented to the Consortium in order to be evaluated taking into account the following factors: size, weight, foundation, actuating system, redundancy, aesthetics and final price. Regarding that parameters the Consortium agreed with the most suitable configuration for INTENSOL objectives.
The design dual-axis tracker comprises next set of elements main frame, support legs, transmission mechanism, linear actuators and electric motors. Structural elements are all made from steel S275JR.
The Main frame has two main functions: to support the Main Frame transmitting the loads to the ground, and additionally it holds electrical motor platform. It has two main requirements: to permit modules (eight per frame) to be installed and rotated corresponding to pitch movement and to permit a roll amplitude rotation ranging from -100º to +100º. Main frame consists of two steel rectangular grid structures. There exist eight cells for each grid, corresponding with each module position. Each grid is supported by two legs which are fixed to floor trough a foundation. These elements provides main frame with the necessary elevation above ground in order to perform roll movement about its longitudinal axis.
Driven mechanisms consist in an electric motor responsible for performing roll movement and two linear actuators for pitch rotation. Different parts that compose the whole system are joined by means of rods and pins which make possible movement transmission between parts,
Dimensioning of tracking structure is based on a static finite element analysis, through evaluation of different load conditions by consideration of different orientation angles and wind velocities. Operational condition is based on a maximum wind velocity equals to 16 m s-1 and dimensioning is govern by maximum deformation criteria (point accuracy not less than 0.2deg). Survival condition is based on a structural strength requirement (maximum equivalent stress not exceeding material yield stress on any point of the structure) after consideration of a maximum wind velocity of 29 m s-1. Static wind loads (pressures) are derived from national standard “CTE SE April 99 “.
In order to select the actuators, multibody tests have been performed regarding the whole assembly properties (masses, inertias, etc.). Since the module centre of gravity is not defined, it has been estimated at 60% of the total module height. In order to analyse requirement for the roll movement (-100º - +100º) electric motor, an optimization process has been perform to adjust the centre of rotation. Taking into account the results of the optimization, the electric motor has been selected, with a reduction able to work with 1378 Nm and a peak load of 2300 Nm.
As with the roll movement, an adjusted design has been perform in order to get a design suitable for use commercial standard actuators. Finally LIMOSS MD120 linear actuator was selected, with a stroke of 600 mm and a maximum load capacity of 8000 N
The joints were selected taking into account the guarantee functional requirements related to accuracy, durability and expansion/ contraction due to thermal changes, without forgetting the cost and maintainability objectives.
Manufacturing process is one of the key factors to take into consideration along first stages in design process in order to avoid problems regarding standard components, supply sizes, stock availability.
3.4: Prototype manufacture and Lab testing
The ITAV low profile 16 modules tracker design was assembled at Insiralia and then shipped to Novamina.
To support its installation Inspiralia has prepared and send to Novamina a complete installation dossier composed by 26 pages with a full description of recommended practices for installation procedure.
WP 4: Advanced guidance and control system
Task 4.1 Modeling and Simulation
Novamina developed initial concepts of integrated calendar and time controller with solar sensor and these were modeled.
Task 4.2 Guidance and Control System Algorithm Design
Based on the initial methods for integrating timing and sun direction signals, an initial system was developed to control the linear actuators to be used on the tracker.
The INTENSOL control system is built upon three main control strategies fused in one hybrid.
From lowest accuracy to highest:
• High accuracy sun position calculation
• Sun sensor measurements
• Maximum output power measurements
Sun calculator and heliotrack controller give us accuracy under 0.2⁰, however due to mechanical imperfections of installed modules we need additional controller to get maximal power from cells. That is why MCPC controller was implemented in existing hybrid (Sun calculator-heliotrack) control software which is detailed explained in D4.1.
The control strategy is chosen based on feedback from the sun sensors: if the Heliotrack sensor is not sufficiently illuminated, the sun calculator will provide input for actuator controller. When insolation is high enough the Heliotrack sensor will take over control of tracker and finally when tracker is in a fully sun pointing position the MCPC will initiate fine tuning and take over control.
Additional safety measures were implemented to cover conditions which might cause damage to the system including water pressure, temperature measurements (to indicate problems with cooling), wind speed, snow load and electrical problems with the inverter and grid.
An easy to use graphical interface was set up to enable control of the final prototype tracker systems.
Task 4.3 Guidance and Control System Test
Tracking accuracy testing
One lens parquet was used due to easier handling. Namely, during pre-testing it was noticed that the lens should be covered to prevent overheated spots near secondaries when focus is not inside secondary (causing "burning" of gaskets and bottom plate coating.
Tracking accuracy was significantly improved (compared to result in the initial phase where accuracy was 0.5 an. deg) and the achieved value was better than 0.1 deg.
• Actuator regulation steps based on built in hall sensor is in-between 0.5 angular deg. Using additional outside sensor it is possible to get much more sensitive positioning.
• Changes in 0.5 angular deg moves lens focus on the edge of cell (consequence: Isc decrease for approx. 20 %)
• Additional 0.5 angular (total 1 deg), moves focus in the middle of secondary sloped side what had the result of decreasing Isc to 50 % ( related to Ics with focus exactly in the middle of cell surface).
In conclusion the tracking accuracy should be increased by using additional sensor (for eq. 4 coordinate sun sensitive sensor (= focus sensing) with moving sensing accuracy of 0.1 degrees in any direction).
WP 5: Integration into overall component
Package objective:
Based on works, reports referred in WP1-WP4 the Technical board defined final design, integration work details and prototype manufacture procedure. Mechanical assembly of all novel hardware components, all software component interface and system integration will be done and prototype will be completed. Procedures for future massive manufacturing process were optimized and delivered as manufacturing process technology report.
Task.5.1: Manufacture the Heat management system
Working drawings have been produced from concept design.
A Stand alone afterheating concept was designed. Cost analysis had shown significant un-feasibility of a fully integrated overall heating system if the afterheating were to be installed on the 2 axis tracker together with HCPV part.
Stand alone after heating concept gives more flexibility concerning combining of various different types of solar heaters (heat regines) heating up PV system cooling fluid in the second thermal circuit (by means of multi heating sourced pipe exchanger immersed in fresh water storage).
Manufacture Heat management system.
The heat management system was developed and prototype was built.
System involves the following control & executing functions:
• PV cells overheating protection (by means of PV cooling fluid temperature, flow and pressure measuring and acting function in order to run PV modules out of sun focus to prevent overheating and consequently cells destruction).
• PV cell cooling system control system can turn on by pass cooling circuit in case if there will be no secondary water consumption (and consequently no possibility to exchange heat of PV cells cooling fluid in fresh water storage)
Task 5.2: Manufacture solar collector system
PV solar modules were produced according to the production drawings provided by iXscient, these were delivered directly to Novamina.
The glass focusing lens panels supplied by Microsharp were assembled on the modules.
The fully assembled solar receiver units supplied by iXscient were mounted on the modules.
Tracking system elements produced by ITAV were assembled on site according drawings and assembly instructions.
Additional improvements on tracking system were performed in order to make fine adjusting of overall collector system on site.
Task 5.3: Control system SW, HW platform integration
Control and governing HW and SW system was assembled and integrated with mechanical part of PV solar collector system.
The control system manages and supervises all needed functions in order to assure overall system runs accurate and safe:
• running tracker according implemented 4 way governing algorithm (real time moving, tracker actual position tracking (mechanical position), sun focussing tracking (by means of 4 quadrant photo sensing feedback), maximum PV power point tracking of the all modules output in order to compensate any mechanical imperfection in tracking system (by means of current measuring and fine adjusting of tracker position to assure maximum of current
• assuring fast reaction in order to move out of fully tracked position (sun focus) in case of some overheating emergency.
• stowing modules to a safe position during night (and when system is exposed to some not-normal running conditions; e.g. high wind).
5.4: Transport components and assemble whole system in Croatia
All components were delivered to Novamina:
• Tracker
• Modules
• Receivers
• Lens panels
Novamina assembled and integrated the components with the actuators and control systems at its site in Croatia.
WP6: testing of all components, individual functions + overall performance
The full Intensol system was fully assembled at Novamina site at month 24. This was mainly due to the delays in the delivery of the receiver modules due a series of circumstances initially arising from the withdrawal of Quantasol from the project. However, in addition there were some issues with the tracker system in terms of mounting arrangements, and finally the weather in Croatia in December 2012 (and January 2013) was extremely poor and therefore no full testing at this stage of the intensol final prototype has been possible. However the consortium is committed to continue the activities on the system and run it operating in the spring and summer of 2013.
Industrial testing of performances was performed on partial sub-systems and overall PV collector system as well.
Testing period of PV solar system was during winter period under condition without direct sun light. Thus some tests were limited concerning obtained results.
Task 6.2: Industrial testing of performances and functioning of hybrid solar thermal system
Hybrid solar system was separately tested during the summer 2012.
Task 6.3: Industrial testing of performances and functioning of advanced guidance and control system
Control and governing HW and SW system functions were tested in order to prove tracking accuracy and emergency actions (based on incorporated features specified in task 5.3.).
To the lack of sun, there was no condition to test sun focussing tracking and maximum PV power point tracking of the all modules output in order to compensate any mechanical imperfection in tracking system (there was no PV output).
Guidance and control system testing passed successfully.
Task 6.4: Industrial testing of performances and functioning of the complete prototype
Overall tracking system functionality was tested (mechanical mowing parts and integrated guidance and control system).
Tracking accuracy was tested and some issues regarding improving in tracker design were noticed (e.g. transmission backlash in connection of some moving parts; module parallelism adjusting; etc).
Electrical performance and overall PV efficiency weren’t tested due to the testing condition.
6.5: Demonstration activities and Final Demonstration Event
A demonstration event for the Intensol system will be organized by iXscient and Novamina in collaboration with the SME partners for summer 2013, when the system is fully tested and debugged.
Potential Impact:
Impacts and Benefits
The 2 year period of the project (2011 and 2012) covered a very difficult period in the development of solar energy systems. In this time the cost per peak watt for standard PV system dropped from around 5.5 dollar per peak watt to just above 4US$. The cost for PV modules dropped from 1.85 to less than 1. This has been due to the massive growth of low cost Chinese PV modules makers. A number of large and small solar energy companies have ceased to operate as a result of these changes. In particular companies which have taken alternative routes (compared to standard silicon PV panels) have found it hard to provide systems that compete commercially, with full installed cost now approaching 4 dollar per peak watt. Concentrated Solar Power remains a difficult area commercially as large increases in supplied volumes are necessary to reduce costs, but these are difficult to achieve in competition with conventional PV. In addition concentrated PV can only be installed in areas of high direct solar and the major countries installing solar energy are still located in temperate climates – such as Germany – and this limits the use of concentrated PV.
The project aimed to achieve to main developments:
1. By using a liquid cooled HCPV system the levels of concentration compatible with efficient operation could be increased, or run at high levels (around 1,000 compared to the 300 to 700 representing the bulk of HVPV)
2. By utilising the increased temperatures from the liquid cooled HCPV some of the benefits of providing hot water in addition to electricity could be provided.
3. Finally the project aimed to provide a complete modular system which could be operated in small scale, industrial or potentially roof mounted operations.
The goal was also to incorporate technologies which had the potential, when scaled to large volumes, of reducing the costs to levels competitive with standard PV installations, with the hot water production as a value added product. These included:
• The production of the primary optics
• The design of the tracker system
Further work would be required to reduce the costs of the module boxes, for example by using mass produced plastics.
The project succeeded well in (1) above. Further changes to the system to increase the levels of solar concentration (and therefore decrease the overall costs of the system) appear to be very feasible since the qualty of the water cooling appears to be very good. Solar concentrations of around 1,200 should be possible, with primary lenses of around 40 cm by 40 cm. In terms of provided an integrated system which could deliver hot water at temperatures which are highly useful, for example 150 degrees C, the pure HCPV cooling system is unable to do this, as the PV cells would be operating at too high a temperature. The project had always anticipated this and additional solar thermal (concentrated or non-concentrated) were part of the design. An initial analysis showed that the solar thermal afterheaters did not represent sufficient value if they were included in the area on the tracker – a high cost resource. Therefore the 2-axis tracker was limited to the HCPV component. Simple, high efficiency flat panel solar heaters were adequate to raise the temperature to around 100 degrees, and concentrated 1-axis tracking system was useable for temperatures up to 150 degrees. Therefore the Intensol system can be seem as a modular arrangement consisting of the core HCPV system plus optional solar thermal components, which can be used in the following way:
• The HCPV system is used alone (no hot water production) and a passive cooling radiator is integrated in the water circulation loop
• The HCPV system plus a fixed array of high quality (double glazed or evacuated thermal tube) flat solar thermal panels are used and the system delivers hit water up to around 100 degrees C. This is sufficient for hot water and thermally driver cooling systems, for example for a factory, office or hotel
• The HCPV system is integrated with a 1-axis linear concentrator system to achieve temperatures of around 150 degrees. This is useable for industrial purposes such as heating and drying.
The Intensol system has a current total cost of around 11 dollars per peak watt installed (including tracker). This is more expensive than tracked flat panel PV. In order to become commercially viable the project therefore needs to perform the following activities (in addition to all the improvements noted as a result of small deficiencies in the performance of the system which will inevitably be noted over the course of the its testing):
• The overall bill of materials and assembly costs need to be reduced to approximately one third of its current value. A full installed cost price to the customer of 4 US$ per peak watt is required
• The performance of the system need to be increased as far as is possible, particularly by incorporating solar cells with highest performance. Currently Solar Junction provides such cells and these need to be tested and incorporated.
On the basis that these developments are achievable following the testing and overall redesign of the system, then Intensol system can be a viable alternative to flat panel PV and flat panel solar thermal for thee applications, particularly since it should utilise reduced installation areas, thereby maximising the benefit of e.g. limited roof area for industrial or commercial buildings.
Impacts and Benefits of the Intensol system
Clean energy using solar power systems is a politically desirable goal, since it provides electricity (and heat) with a definite cost structure over the coming years, thereby reducing uncertainties associated with cost increases in fossil fuel prices and the dependence of European economies on unstable or unreliable foreign suppliers
There are significant economic benefits to whole economies and to individual consumers of the use of cost effective and useful solar energy. It is anticipated that a combination of increases in fossil fuel costs and the introduction of carbon taxes or similar will make well designed and lower cost solar energy eventually (around the 2015-2020 time frame) cost competitive with energy from fossil fuels even without any specific subsidies
Development of quality, cost effective European solar energy systems will contribute to the economy and to jobs. Currently the PV industry appears to be moving more and more to China based on commoditised flat silicon PV panels. Solar energy based more on the types of technologies in the car industry and advanced wafer epixtaxy favour European production. Therefore, if the design of the Intensol system can be sufficiently cost engineered, there is great potential to perform the manufacture of the system e.g. in Eastern Europe with specific components from western Europe (e.g. the solar cells from IQE).
The approach of the Intensol system is such that it can be envisaged that a progressive set of technological improvement can lead to its continuing development to achieve lower costs and better performance. These include improvements in the engineering systems (electrical ,fluidic, heat management, tracker) . optical (better lenses and secondary) and solar cell (improved efficiencies). Therefore this type of system can be driver of technological improvements in Europe.
The Intensol system, being a source of solar electricity and heat, has environmental benefits with reductions in the emission of carbon dioxide (utilisation of carbon based fuels).
Clearly the level of such benefits relates to the installed volumes.
Overall all the anticipated results of the supply and uses of such systems is broadly beneficial.
Potential markets for the Intensol system
As detailed above, in order to compete effectively with flat panel PV and solar thermal systems given their very large decreases in costs over the last 2 years, the Intensol system need to be cost engineered to reduce it (in volume) installed cost to around US3.25 per peak watt. This is the target in the original proposal. The approximate power output of the single module Intensol system (when fully engineered and including state of the art triple junction cells) is 7.5 kW. Therefore the installed cost of the single module system needs to be around $US25,000 (19,250 euros). The current bill of materials and assembly price is estimated at $US88,000 (single prototype) and therefore a price reduction to less than a third is required. With appropriate changes and the required volumes this still anticipated to be possible.
The target market for high concentration systems will always be reduced compared to flat panel PV as they require installation in regions with a very high proportion of clear sky days, and (as with all solar systems) their economics improves with the annualised solar intensity at a location.
Suitable locations including Southern Europe (Italy, Spain ,Greece, Croatia) and non European countries such as North African and Middleastern countries. It is anticipated that the in general the electrical power and hot water provided by the systems will be consumer locally. The target types are:
• Industrial, such as production facilities
• Offices
• Hotels
• Public sector facilities such as Hospitals
• Combined heat and power facilities (integrated with other power sources) for denser residential developments
The major changes in the solar PV and energy markets of the last 2 years have made predictions of sales difficult, at this stage the consortium is intent on determining the ability to cost engineer the Intensol system to the required target. It is felt that with this achieved, plus data on the system operation, installation in hotels, industrial sites and offices should be possible, with sales building over a period of time of perhaps around 5 years. It is currently anticipated that a further 24 months of development is required.
Customer pay back period. The pay back period for installation of an Intensol system at the target price is still anticipated to be between 3-5 years, depending on grid electricity prices.
Benefits to partners. The achievement of the final Intensol system with lifetime, performance and cost meeting the current targets, would achieve significant benefits for the partners:
• Ability to supply components to the system
• Sales and income from system sales
• Retention and increase in jobs
Actual values will depend on the cost targets achieved and the state of the solar PV market in the years ahead, which is highly unpredictable (as judged by the last 2 years).
Dissemination and Exploitation
Discussions were held with both the SMEs and RTD partners to ensure that concepts developed during the programme would be fully protected.
Microsharp developed and filed a new patent within the project covering a solar thermal hybrid system: Solar Energy Apparatus. However search reports and evaluation by the EPo indicated that there was prior art making it difficult to develop an acceptable patent. In addition the patent itself covered an integrated PV and thermal receiver and evaluation within the project had indicated that the thermal component of the system should be separate (and not mounted on the tracker at all). The patent therefore had ceased to reflect the actual designs within the Intensol project. The patent was therefore dropped.
Microsharp and iXscient carried out an evaluation of the different components of the system with regard to protection.
The following system element dissemination was performed to partners:
Cell bonding process from iXscient to Microsharp
Receiver design from iXscient to Microsharp/Emergo/Sadel
Module design from iXscient to Microsharp/Emergo/Sadel
Low profile tracker design from Inspiralia to Microsharp/Emergo/Sadel
Control system including algorithms and software from Novamina to Emergo/Sadel (plus Microsharp)
Liquid cooling HCPV system from Novamina/iXscient to Microsharp/Emergo/Sadel/IQE
Overall system including solar thermal elements from Novamina/iXscient/Insiralia to Microsharp/Emergo/Sadel/IQE
Dissemination of the results through papers and press has been limited in this project, since the partners have been developing a system of commercial value and the project partners have, at this stage, mostly have Ip retention on the basis of know how, potetial designs and trade secrets. However in the coming year strong efforts will be made, on the basis of the completed performance of the system, to perform this dissemination.
Future funding & investment plans
Discussions between the SME partners: Microsharp, Emergo, Sadel and Einvest indicated the following roles in developing the Intensol system for funding and investment:
Microsharp and Emergo to complete initial aspects of exploitation plan in terms of completion, debugging, modifications and testing of the Intensol system, along with a detailed further analysis of how to reduce costs to one third of initial prototype costs
Sadel to evaluate the further markets and installation prospects of the system given the very fast changes the PV and solar energy market is undergoing at the present time
Eninvest to explore potential in Easter Europe including funding and investment arrangements.
IQE to assist in integration of state of the art, advanced high concentration solar cells
The goal is to bring together the completed system along with the changes required for cost reduction with a renewed market analysis (as of 2014-2015) to enable investment and initial installations of small systems.
Exploitation planning
An exploitation plan has been completed.
Currently the cost of the system per peak watt is only just in the ball park of being able to sell, so long as the cost decreases with volume are real. Therefore there is a need for the system to:
1. Be restructured to decrease the cost targeting reductions to achieve around a full installed cost of $US 3-4 per peak watt
2. Be improved to increase the power output via better optics (with increased concentration ratio) and improved solar cells – contacts are already underway with Solar Junction to source their 44% efficient cells
3. Generate a set of test results to enable focussing on the key areas for improvement and begin to provide the information needed for the investors and users of the system.
Set of activities and time line
Firstly the consortium will explore again the balance between PV only passive cooled system compared to PV/Thermal liquid cooled systems – is the benefit of e.g. 50-60 degree hot water sufficiently beneficial, is there a genuine benefit to liquid cooling to get concentration factor up, is the danger of catastrophic damage sufficiently under control (tracker to rapidly move out of solar focus). This will determine the specific role of a combied concentrated Pv and thermal system with liquid cooling.
Practical activities:
1. Modify the tracker to overcome and correct all problems associated with tracker design and arrive at a consistent solution and design including reductions of mass
2. Modify and put into full implementation the cooling system
3. Connect the system with the inverter and connect it to a load and monitor over a period of time
4. Extend adapt and complete the control system, including full documentation of the algorithms, sensors, control issues
5. Test all the components over the summer of 2013
6. Explore all the components of the system to identify designs which reduce costs of each element
• Module design integrated with the fluidic back plate
• Plastic module
• Modified tracker
7. For PV - continue discussion with Solar Junction to full identify a costed upgrade to the receiver operating with 44% efficient cells
8. Build next prototype based upon improvement in system – increased efficiency and reduction in price, and re-evaluate with respect to commercial outcomes – need to achieve an installed peak watt price of <$US4.
List of Websites:
www.intensol.eu
Main contacts:
Ernest Vlacic: Emergo:
ernest.vlacic@emergo.hr
Nicholas Walker: Microsharp: n.walker@microsharp.co.uk: +44 7788583376