Final Report Summary - SOLARGAIN (Low-cost switchable reflective polymeric solar heat gain control films for energy-efficient smart-window applications)
Executive Summary:
Energy savings and reduction of carbon emissions are currently keys to improving economic performance in the building sector. Many tax incentives subsidise reductions of carbon emissions and energy savings reduce the operational expenses of company sites and increase the profitability of companies.
The SolarGain technology provides a switchable and fully adjustable filter that captures infrared sun radiation energy and can reduce the amount of sun radiation energy across windows by approximately 2/3. The novel feature of the SolarGain technology is that the film technology allows to regulation/adjustment of the reflection of infrared sun radiation energy from 0% to 66%.
The SolarGain film consists of giant birefringent optical (GBO) elements that are assembled from multi-layer films made by co-extrusion of transparent polymers. GBO film is designed to be a reflective polarizer, which reflects light of one polarization direction and is transparent for the other polarization direction. If two reflective polarizers are located one behind the other, the intensity of reflected and transmitted light can be tuned by varying the relative rotation angle of the films. In case of the SolarGain technology this is done electro-optically by using a liquid crystals layer between the polarisers. The liquid crystals (with transparent electrodes attached) in between two GBO reflective polarizers, realize a switchable polymeric window film for solar heat gain control.
The SolarGain film uniquely enables the regulation of solar infrared radiation penetration into buildings and hence heating effect on buildings by either:
• in summer, shielding from excessive sun radiation and therefore save air-conditioning costs or
• in winter, maximising penetration of sun heat radiation and therefore save heating costs.
The SolarGain consortium developed a model to analyse the cost effectiveness of the SolarGain film and compared these with non-switchable films. The analysis shows that SolarGain films are more cost effective the non-switchable films and have an ROI of 5.2 years compared to an ROI of 5.9 years for non-switchable window films. Final production costs estimates allowed this model to be revaluated with ROI reducing to 3.5 years for SolarGain switchable film.
The attractive return of investment of the SolarGain film provides a compelling reasoning for the uptake of the SolarGain technology into the market for windows and doors, a market with a current value in Europe of $31 billion. The consortium is planning to build a business around the SolarGain technology which is expected to break even in year 4 after commercialisation and is likely to generate an accumulative profit of €25 million within 10 years.
Project Context and Objectives:
The overall objective of the SolarGain project was to develop an innovative low-cost all polymeric switchable reflective Solar Heat Gain Control (SHGC) film. This film will be used either as a retro-fit solution or in new window assemblies to control heat/energy loss in winter months and solar heat gain (overheating) during summer months. Whilst a key desirable feature in a buildings architecture, providing enhanced natural lighting (for occupier comfort) and reduced artificial lighting (for lower energy consumption), windows are recognised as a key weak spot within a buildings energy efficiency. Within Europe, the inferior energy efficiency of windows has been demonstrated to represent ~ 10% of a buildings total energy use. Considerable research has been invested towards the development of low-energy window designs that contribute net ‘zero energy balance’ to buildings efficiency. Whilst significant progress has been made towards the development of cost-effective super-insulating window designs (typically combining triple glazing, low-emissivity coatings and highly insulating spacer and window-frame systems) more limited progress has been made towards the development of cost-effective technologies for the control of solar heat gain. Existing solutions for solar heat gain control primarily target use of a film or coating applied across the window surface to control the passage of light and thus, heat build-up in the room. First-generation SHGC films utilise passive additives or coatings selectively to absorb specific wavelengths of light. Although achieving an effective reduction in solar heat gain such films have static properties (which prevent transmission of heat into a room during winter months) and typically have inferior visible-light transmission (reducing natural day lighting of the room, resulting in reduced occupier comfort and increased artificial lighting use). Consequently static SHGC films have been demonstrated to provide limited or negative energy savings.
The SolarGain consortium has developed a transparent and colourless, dynamic (switchable) reflective solar heat gain control film that may be incorporated within existing highly-insulating sealed window unit designs for dynamic control of solar heat gain. The SolarGain film is a multi-layer film which operates in the infra-red region giving control to the amount of radiated heat whilst retaining a constant level of visible light transmission. The number of films in the multi-layer stack are minimised to ensure that the SolarGain technology is cost competitive and large areas of film can be controlled from one source.
The technology requires a small voltage to switch the film and can be supplied as part of a window unit. The SolarGain technology is competitive on cost with existing current state of art alternatives.
Project Results:
A list summarising the scientific and technological objectives is shown thus:
Scientific Objectives:
1. Electro-optic Chromophore: To understand how the chromophore chemical structure influences its electro-optic (effect and activity); stability (thermal and photochemical); and optical (absorption profile) properties.
2. Electro-optic Polymer: To understand the relationships between the chromophore chemistry; method of chromophore incorporation within the host polymer (additive, side chain/cross-linking group); the polymer properties (rheology, glass transition temperature etc.); the chromophore poling method (applied electric field, photo-assisted poling) and process (electric/optical field strength, temperature profile and time); poling stabilisation methods (radiation induced cross linking); and resulting electro-optic polymer properties (EO-activity; effect and poling stability; tensile and flexural strength, etc.).
Multilayer switchable reflective film: To understand further the complex relationships between the multilayer film structure and properties (difference of refractive index between alternating layers in the ‘on’ and ‘off’ electro-optic states, number of layers, individual layer thicknesses and differences (gradient) in layer thicknesses through the film structure, and total film thickness); and the resulting film optical properties in the on and off states (light transmittance, absorption and reflection profiles).
Technological Objectives
1. To develop a novel electro-optic chromophore chemistry achieving: a thermal stability > 280 °C; limited (< 5%) absorption within the visible spectrum, a hyperpolarisability (as a function of molecular weight) and high photochemical stability (< 2% degradation after irradiation in oxygen saturated solutions for 100 minutes).
2. To develop an electro-optic polymer incorporating the novel chromophore chemistry, achieving: a polymer glass transition temperature between 150 °C and 200 °C; an electro-optic co-efficient r33 >22 pm V-1 at < 20% chromophore addition; > 90% chromophore poling in < 10 minutes at poling voltages of < 100 V μm-1; and a poling stability > 90% after 7 days at 50 °C, retaining an r33 > 20 pm V-1.
3. To develop a multilayer film structure comprising alternating layers of two (or more) polymer materials, one of which is an electro-optic polymer, having a difference in refractive index < 0.03 in the off state and > 1.0 in the on state, a layer thickness from < 200 nm and comprising > 200 layers; achieving a light transmittance > 0.7 in the off state and a solar heat gain co-efficient < 0.05 in the on state; and requiring < 1.5 V power for film activation.
4. To develop the required production processes for manufacture of the solar heat gain control film incorporating:
• A reactive extrusion process for grafting of the electro-optic chromophore to the target polymer achieving > 70% graft reaction conversion efficiency with < 5% chromophore deactivation and > 95% removal of unreacted chromophores and reaction by-products.
• A complex die design enabling the co-extrusion of alternating die design enabling the co-extrusion of alternating multilayer film structures comprising > 200 layers with a layer thickness from <200nm and enabling >15% controlled gradient variation of layer thicknesses through the multilayer structure.
• A tri-extrusion or surface coating process for application of a conductive surface film or coating enabling controlled application of an electric fiels through the film structure and retaining a visible light transmittance >0.60 (off state).
• A production process for poling of the solar heat gain control film, achieving > 90% chromophore poling (orientation) in < 10 minutes at poling voltages of <100 V μm-1. 5) To develop sealed-window unit and associated production processes, incorporating the novel solar heat gain control film and state-of-the-art photovoltaic and sensor technology, achieving an insulation performance (U-value) < 1.2 W m-2 K-1, light transmittance > 0.45 (off state), solar heat gain co-efficient < 0.05 (on state), > 15 years acceptable performance lifetime, self-powering and automated activation, and < €60 m-2 manufacturing cost.
5. To develop a laminated window-film material and production process, integrating the novel solar heat gain control film and state-of-the-art photovoltaic and sensor technology, that may be retrofitted to existing window stock (residential and non-residential), achieving a light transmittance > 0.60 (off state), solar heat gain co-efficient < 0.05 (on state), self-powering and automated activation, > 10 years’ acceptable performance lifetime and < €30 m-2 manufacturing cost.
Potential Impact:
The SolarGain consortium has developed a switchable window film that provides protection against heat radiation from sunlight as well as protection against loss of heat energy by radiation through windows in heated buildings. The SolarGain technology is fully adjustable and allows regulation of the level of heat penetration in the range of 0% - 70% thus improving occupier comfort and increasing the energy efficiency of a building using the SolarGain technology.
An ROI model has been created based on a 20,000m² office block situated in a southern European climate typical for Spain, Italy or Greece. The model assumes an average outside temperature of 15°C and sun radiation energy of 4.5kWh/m² day. The benefit of the SolarGain technology is that it utilises sun radiation energy in summer (shielding two thirds of the sun radiation energy) and winter (containing two thirds of the internal heat energy). Hence the SolarGain technology reduces in contrast to non-switchable films the winter heating cost and therefore reduces the annual heating and cooling cost by €10,500 as opposed to €6,200 for non-switchable films. Based on cost SolarGain is calculated to give 59% additional cost savings on heating and cooling per annum in the case of the example used. The ROI for an end user purchasing the SolarGain technology is calculated to be 5.2 years as opposed to 5.9 years for non-switchable window films.
The consortium is currently anticipating that full commercialisation of the system will be achieved approximately 18 months after project end. The value of the European window and door market is according to Freedonia market information about €23 billion. The SolarGain consortium hopes to achieve a market penetration of between 0.5% and 1% within 10 years post project. In the first year of commercialisation the consortium expects to sell about 460m² of the SolarGain window technology and to increase sales to 300,000m² per annum within 10 years, equivalent to a sales value of €20 million. Including cost for installation, sales & marketing and further development, the consortium expects in year 10 a cumulative profit of about €25 million.
List of Websites:
www.solargain.eu
Energy savings and reduction of carbon emissions are currently keys to improving economic performance in the building sector. Many tax incentives subsidise reductions of carbon emissions and energy savings reduce the operational expenses of company sites and increase the profitability of companies.
The SolarGain technology provides a switchable and fully adjustable filter that captures infrared sun radiation energy and can reduce the amount of sun radiation energy across windows by approximately 2/3. The novel feature of the SolarGain technology is that the film technology allows to regulation/adjustment of the reflection of infrared sun radiation energy from 0% to 66%.
The SolarGain film consists of giant birefringent optical (GBO) elements that are assembled from multi-layer films made by co-extrusion of transparent polymers. GBO film is designed to be a reflective polarizer, which reflects light of one polarization direction and is transparent for the other polarization direction. If two reflective polarizers are located one behind the other, the intensity of reflected and transmitted light can be tuned by varying the relative rotation angle of the films. In case of the SolarGain technology this is done electro-optically by using a liquid crystals layer between the polarisers. The liquid crystals (with transparent electrodes attached) in between two GBO reflective polarizers, realize a switchable polymeric window film for solar heat gain control.
The SolarGain film uniquely enables the regulation of solar infrared radiation penetration into buildings and hence heating effect on buildings by either:
• in summer, shielding from excessive sun radiation and therefore save air-conditioning costs or
• in winter, maximising penetration of sun heat radiation and therefore save heating costs.
The SolarGain consortium developed a model to analyse the cost effectiveness of the SolarGain film and compared these with non-switchable films. The analysis shows that SolarGain films are more cost effective the non-switchable films and have an ROI of 5.2 years compared to an ROI of 5.9 years for non-switchable window films. Final production costs estimates allowed this model to be revaluated with ROI reducing to 3.5 years for SolarGain switchable film.
The attractive return of investment of the SolarGain film provides a compelling reasoning for the uptake of the SolarGain technology into the market for windows and doors, a market with a current value in Europe of $31 billion. The consortium is planning to build a business around the SolarGain technology which is expected to break even in year 4 after commercialisation and is likely to generate an accumulative profit of €25 million within 10 years.
Project Context and Objectives:
The overall objective of the SolarGain project was to develop an innovative low-cost all polymeric switchable reflective Solar Heat Gain Control (SHGC) film. This film will be used either as a retro-fit solution or in new window assemblies to control heat/energy loss in winter months and solar heat gain (overheating) during summer months. Whilst a key desirable feature in a buildings architecture, providing enhanced natural lighting (for occupier comfort) and reduced artificial lighting (for lower energy consumption), windows are recognised as a key weak spot within a buildings energy efficiency. Within Europe, the inferior energy efficiency of windows has been demonstrated to represent ~ 10% of a buildings total energy use. Considerable research has been invested towards the development of low-energy window designs that contribute net ‘zero energy balance’ to buildings efficiency. Whilst significant progress has been made towards the development of cost-effective super-insulating window designs (typically combining triple glazing, low-emissivity coatings and highly insulating spacer and window-frame systems) more limited progress has been made towards the development of cost-effective technologies for the control of solar heat gain. Existing solutions for solar heat gain control primarily target use of a film or coating applied across the window surface to control the passage of light and thus, heat build-up in the room. First-generation SHGC films utilise passive additives or coatings selectively to absorb specific wavelengths of light. Although achieving an effective reduction in solar heat gain such films have static properties (which prevent transmission of heat into a room during winter months) and typically have inferior visible-light transmission (reducing natural day lighting of the room, resulting in reduced occupier comfort and increased artificial lighting use). Consequently static SHGC films have been demonstrated to provide limited or negative energy savings.
The SolarGain consortium has developed a transparent and colourless, dynamic (switchable) reflective solar heat gain control film that may be incorporated within existing highly-insulating sealed window unit designs for dynamic control of solar heat gain. The SolarGain film is a multi-layer film which operates in the infra-red region giving control to the amount of radiated heat whilst retaining a constant level of visible light transmission. The number of films in the multi-layer stack are minimised to ensure that the SolarGain technology is cost competitive and large areas of film can be controlled from one source.
The technology requires a small voltage to switch the film and can be supplied as part of a window unit. The SolarGain technology is competitive on cost with existing current state of art alternatives.
Project Results:
A list summarising the scientific and technological objectives is shown thus:
Scientific Objectives:
1. Electro-optic Chromophore: To understand how the chromophore chemical structure influences its electro-optic (effect and activity); stability (thermal and photochemical); and optical (absorption profile) properties.
2. Electro-optic Polymer: To understand the relationships between the chromophore chemistry; method of chromophore incorporation within the host polymer (additive, side chain/cross-linking group); the polymer properties (rheology, glass transition temperature etc.); the chromophore poling method (applied electric field, photo-assisted poling) and process (electric/optical field strength, temperature profile and time); poling stabilisation methods (radiation induced cross linking); and resulting electro-optic polymer properties (EO-activity; effect and poling stability; tensile and flexural strength, etc.).
Multilayer switchable reflective film: To understand further the complex relationships between the multilayer film structure and properties (difference of refractive index between alternating layers in the ‘on’ and ‘off’ electro-optic states, number of layers, individual layer thicknesses and differences (gradient) in layer thicknesses through the film structure, and total film thickness); and the resulting film optical properties in the on and off states (light transmittance, absorption and reflection profiles).
Technological Objectives
1. To develop a novel electro-optic chromophore chemistry achieving: a thermal stability > 280 °C; limited (< 5%) absorption within the visible spectrum, a hyperpolarisability (as a function of molecular weight) and high photochemical stability (< 2% degradation after irradiation in oxygen saturated solutions for 100 minutes).
2. To develop an electro-optic polymer incorporating the novel chromophore chemistry, achieving: a polymer glass transition temperature between 150 °C and 200 °C; an electro-optic co-efficient r33 >22 pm V-1 at < 20% chromophore addition; > 90% chromophore poling in < 10 minutes at poling voltages of < 100 V μm-1; and a poling stability > 90% after 7 days at 50 °C, retaining an r33 > 20 pm V-1.
3. To develop a multilayer film structure comprising alternating layers of two (or more) polymer materials, one of which is an electro-optic polymer, having a difference in refractive index < 0.03 in the off state and > 1.0 in the on state, a layer thickness from < 200 nm and comprising > 200 layers; achieving a light transmittance > 0.7 in the off state and a solar heat gain co-efficient < 0.05 in the on state; and requiring < 1.5 V power for film activation.
4. To develop the required production processes for manufacture of the solar heat gain control film incorporating:
• A reactive extrusion process for grafting of the electro-optic chromophore to the target polymer achieving > 70% graft reaction conversion efficiency with < 5% chromophore deactivation and > 95% removal of unreacted chromophores and reaction by-products.
• A complex die design enabling the co-extrusion of alternating die design enabling the co-extrusion of alternating multilayer film structures comprising > 200 layers with a layer thickness from <200nm and enabling >15% controlled gradient variation of layer thicknesses through the multilayer structure.
• A tri-extrusion or surface coating process for application of a conductive surface film or coating enabling controlled application of an electric fiels through the film structure and retaining a visible light transmittance >0.60 (off state).
• A production process for poling of the solar heat gain control film, achieving > 90% chromophore poling (orientation) in < 10 minutes at poling voltages of <100 V μm-1. 5) To develop sealed-window unit and associated production processes, incorporating the novel solar heat gain control film and state-of-the-art photovoltaic and sensor technology, achieving an insulation performance (U-value) < 1.2 W m-2 K-1, light transmittance > 0.45 (off state), solar heat gain co-efficient < 0.05 (on state), > 15 years acceptable performance lifetime, self-powering and automated activation, and < €60 m-2 manufacturing cost.
5. To develop a laminated window-film material and production process, integrating the novel solar heat gain control film and state-of-the-art photovoltaic and sensor technology, that may be retrofitted to existing window stock (residential and non-residential), achieving a light transmittance > 0.60 (off state), solar heat gain co-efficient < 0.05 (on state), self-powering and automated activation, > 10 years’ acceptable performance lifetime and < €30 m-2 manufacturing cost.
Potential Impact:
The SolarGain consortium has developed a switchable window film that provides protection against heat radiation from sunlight as well as protection against loss of heat energy by radiation through windows in heated buildings. The SolarGain technology is fully adjustable and allows regulation of the level of heat penetration in the range of 0% - 70% thus improving occupier comfort and increasing the energy efficiency of a building using the SolarGain technology.
An ROI model has been created based on a 20,000m² office block situated in a southern European climate typical for Spain, Italy or Greece. The model assumes an average outside temperature of 15°C and sun radiation energy of 4.5kWh/m² day. The benefit of the SolarGain technology is that it utilises sun radiation energy in summer (shielding two thirds of the sun radiation energy) and winter (containing two thirds of the internal heat energy). Hence the SolarGain technology reduces in contrast to non-switchable films the winter heating cost and therefore reduces the annual heating and cooling cost by €10,500 as opposed to €6,200 for non-switchable films. Based on cost SolarGain is calculated to give 59% additional cost savings on heating and cooling per annum in the case of the example used. The ROI for an end user purchasing the SolarGain technology is calculated to be 5.2 years as opposed to 5.9 years for non-switchable window films.
The consortium is currently anticipating that full commercialisation of the system will be achieved approximately 18 months after project end. The value of the European window and door market is according to Freedonia market information about €23 billion. The SolarGain consortium hopes to achieve a market penetration of between 0.5% and 1% within 10 years post project. In the first year of commercialisation the consortium expects to sell about 460m² of the SolarGain window technology and to increase sales to 300,000m² per annum within 10 years, equivalent to a sales value of €20 million. Including cost for installation, sales & marketing and further development, the consortium expects in year 10 a cumulative profit of about €25 million.
List of Websites:
www.solargain.eu