Research &

Read more about Racell’s research and development

Research & Development

At Racell, research and development are key to our success. Over the years we have participated in numerous projects with the aim of improving our production and implementation of solar energy. Notably in relation to issues of implementation, we have worked with partners from various fields related to the construction industry. We have cooperated with architects, construction companies, leading consulting groups, and research teams at universities.


As a pioneering company, Racell has taken out many patents covering the value chain relevant to our endeavors. The Racell expertise ranges from quarts; silicon purification; crystal growing; wafering; semiconductor and cell manufacturing; over manufacturing of multifunctional modules; mounting systems to complete PV and CHP-C smart grid systems.

Selected Research & Development projects

Monitoring program for an optimization of a new type of energy supply system with heat pump and battery storage for single family houses

RACELL Saphire Technologies ApS

ELFORSK:   2018 – 2020

A measuring programme is carried out in order to document the simulated operation of a BIPVT-E pilot system (PVT-energy absorber, heat pump and battery etc.) under a realistic consumption pattern. The detailed monitoring data is collected to allow optimisation of the system performance preparing for an intelligent system that can control all components according to efficiency, comfort and economy.

In ELFORSK project 349-054 a full-scale PVT-E system was developed. It included PVT-energy absorber, heat pump and battery for single family homes. The test system was installed spring 2018 in a model house. Simulations of the system indicates that the system can cover the heat requirements in the entire home and almost half of the power consumption, incl. power supply for the heat pump.

Through a two-year measuring programme, the project group documented the performance of the PVT-E “PV Thermal-Energy absorber” system under realistic operation conditions partly to optimize the system key components and operation, partly to use the documentation for focused marketing aimed at the 400,000 homeowners in Denmark, who are today using oil or natural gas boilers.

With the analysis of a full year operation, the project group were able to evaluate the system potential to be covering the need to charge an electric vehicle and the system ability to deliver flexibility to the grid and other system services.

It is the ambition that the BIPVT-E system can be an attractive alternative to conventional heat sources (oil and natural gas), that it within 2030 can contribute to cost-effective realisation of the national Danish obligations to the reduction of greenhouse gases.

Project partners:   DTU, COWI, Rubrik, Danfoss, KAB


RACELL Saphire Technologies ApS

EUDP:          2017 – 2020

The Project objectives were to develop new innovative PVT technology making it applicable and affordable for single family houses and for commercial buildings. Radical cost-reductions were to be gained by enabling complete replacement of the old roof with the new type of watertight PVT modules.

The concept being developed was to include future integration into both large-scale grid and district heating in combination with heat pumps, storage tanks and battery storage. The technology should prove a future cost-effective alternative to fossil fuels and introduce more flexibility in the grid with reliable PVT heat-, cooling- and electrical supply to the end user day and night all year round.

The Smart Solar System project and new PVT technology were successfully developed proving cost-effective full self-reliance by PVT energy via a single-family terrace house.

A power and distribution company, BEOF, was a project partner since one important project goal was to consider how local heat distribution could be organized technically by pooling some houses in clusters, sharing the same PVT-E and BIPVT-E energy source, heat pump, storage and smart grid control system.

The new PVT technology also successfully proved itself fully feasible for complete self-reliant cooling and heating of control towers and buildings in airports in Rønne and Copenhagen. Airports were chosen in order to develop solutions for extraordinarily challenging requirements for energy supply reliability.

As a direct result of this project, 42 similar single-family terrace houses will be renovated in 2021 and provided with PVT modules abolishing all the existing gas boilers.

Project  partners:   RNN, Naviair, COWI, DTU, Rubrik, BEOF, Rockwool, Danfoss and ELFORSK

IEA pVT task participation


EUDP:          2017 – 2020

DTU and RACELL were the Danish participants in the IEA (International Energy Agency) SHC (Solar Heating & Cooling) programme task 60 project on Photovoltaic thermal collector, PVT systems: ”Application of PVT Collectors”.

The objective of the project was, through participation in the international IEA Task 60 project Application of PVT Collectors, to provide an overview of the state of the art of PVT technology. Further, simulation models both for the performance of PV panels and for a PVT/heat pump system were developed and validated by means of measurements for PVT panels and for the PVT/heat pump system.

Due to the complex interaction between the different components of PVT systems and buildings, there are many different designs of PVT systems and it is not easy to optimize the design of PVT systems.

A demonstration heat pump system with PVT panels produced by RACELL Technologies has been tested in the laboratory test facilities at the Department of Civil Engineering, Technical University of Denmark. The PVT panels were connected to a heating system consisting of two storage tanks and a heat pump. A TRANSYS simulation model of the system has been developed and validated by means of measurements from the tested system. Calculations with the validated model elucidated how best to design the system.

Experimental investigations on roof mounted PVT panels and vertical façade integrated PVT panels have been carried out to elucidate their performances in real weather conditions. The measured performances were compared to calculated performances using a simulation model.

Furthermore, measurements of performances of full-scale PVT systems in buildings at different locations in Denmark with different Racell PVT type modules were analysed.

The results of the project were presented at an international 3-day seminar meeting for all interested at the Technical University of Denmark. Presentations by both Danish and international experts in the field were given. The project results formed a good basis for further development of PVT panels and PVT systems.

Danish Project partner:   RACELL.

"COOL PVT" White PVT modules for building integration - developing & test

RACELL Saphire Technologies ApS

EUDP:          2015 – 2017

The goal of the project was to develop completely new PVT module types with invisible solar cells as well as an unprecedented high aesthetic quality that can be used for white or bright facades.

Also the PVT modules must supply power, high temperature heating as well as cooling and will be fully integrated into the building. The modules must be cost competitive with existing solutions on the market.

The project succeeded in developing innovative technologies and achieved the following results:

(1) To make the actual solar cells completely invisible at the same time as the color of the module can be selected over the entire color scale including white. The different color shades resulted in different losses, however, only on between 5 and 30% of the initial optimum output

(2) Cooling energy uptake via black-body-sky radiation was recorded and modular prototypes were optimized for this

(3) Combination of white modules that can also absorb heat via a built-in absorber were built and proven efficient

(4) All the newly developed module types could be building integrated

(5) Developing a type of module that could be insulated at the front with transparent and compact material to achieve the same high temperatures as for traditional solar collector modules

(6) The “COOL PVT” modules proved to work ideally with a heat pump and for periods worked optimally also without the heat pump.

Due to the many color shades, different textures, textures and 3D phenomena that were developed in the project, it became possible to initiate comprehensive dissemination work, where among other things a major Scandinavian architectural competition was held based on the innovative new types of Cool PVT modules.

Project partners:   RACELL, DTU, COWI, MAP Architects, Solar City Denmark

Solar CHP & Cooling for commercial buildnings and local distribution

RACELL Saphire Technologies ApS

EUDP:          2016 – 2018

The project objective was to facilitate via new clean technologies that any typical commercial building can become its own actual energy source, a self-reliant building based on renewable energy only. The building becomes its own energy generator of electricity, heating and cooling.

This optimistic objective was to be reached by developing new types of Building Integrated PV Thermal hybrid panels “PVT”. By designing the appropriate components (heat-pump, batteries, storage tanks and intelligent control), an independent local Combined Heat Power and Cooling System “Solar CHP-C” should be accomplished. The Solar CHP should also be beneficially integrated with district heating systems.

Several commercial building types were investigated, also in different climatic and geographic areas. Adaptable Solar CHP-C system types were developed for these. The results showed that customised and cost-effective PVT modules could be produced for the specific buildings and that surprisingly all energy consumption (Electrical Power, Heating and Cooling) for the commercial building could be fully covered by the innovative Building Integrated PVT / Solar CHP-C system. The building became its own 100% power source.

Project partners: DTU, Castellum, Albertslund Fjernvarme, PlanEnergi, Cowi, Lithium Balance,  Arkitema, Priedemann Facade Lab, Map Architects

RE-VALUE: Value Creation by Energy Renovation, Refurbishment and Transformation of the Built Environment – Modelling and Validating of Utility and Architectural Value

Aarhus Universitet

Innovationsfonden:   2016 – 2019

Energy renovation of residential building benefits the operating budget, but it also has a number of other parameters such as social, cultural, architectural, and health consequences. These “soft” values are not normally included in the renovation or operating budget. The research project will develop budget models that that can determine the impact from energy renovation on the “soft” values so that the residents’ well-being becomes an integral part of the total budget value.

75% of the buildings that exist today will still be in operation in 2040. Hence, a considerable amount of the existing building mass must undergo a substantial renovation to comply with the ambition. Energy renovation is hence a societal challenge, which dramatically will affect the built environment. The overall objective of the RE-VALUE project was to develop and demonstrate the validity of a generic renovation assessment method. This method will allow client and decision makers to identify cost-efficient solution in terms of energy performance as well as create utility and architectural values. The transformation towards a more energy-efficient building mass will thus dramatically affect the built environment.

This assessment model has provided technical solutions, architectural solutions, indoor climate and health solutions, and sustainable construction process solutions.


Project partners: Racell, Enemærke og Petersen, Develco, Deas, Brabrand Bolgiforening, Wicotec Kirkebjerg, AART Architects, Amplex.

PV-StarLight / Architectural BIPV Modules with Built-In Light Diodes

Racell Saphire Technologies ApS

EUDP:   2014 – 2017

The general project aim was to increase the use of photovoltaic in urban areas by improving the architectural expression and exploit surfaces in building integrated solar PV through the use of built-in LEDs. The project aimed to develop new technologies and demonstrate the possibilities in a catalogue, showing examples for large building facades, large visible roof areas and for large area screens. The building integrated modules should, as an important goal, be able to utilize the light diodes with no significant diminishment of the PV energy production of the solar cells.

In the project period, we successfully managed to develop technologies providing (1) a high density of LEDs as part of the PV cells i. e. inside the PV module laminate, (2) programable & remote-controlled LEDs, (3) integration of LEDs in ultra large area PV modules, (4) BIPV modules that can function as actual video screens.

Project partners:  Solar City Denmark, MAP Architects, PRIEDEMANN/ Facade-Lab, COWI 

Demonstration of combined solar cell- and solar collector module (PVT) for apartment buildings (Phase II)

Racell Saphire Technologies ApS

EUDP:   2014 – 2017                                                                                                                                                                                                                                        :   2014 – 2017EUDP:   2014 – 2017 

The project will demonstrate that solar energy modules can transform an old multi-story residential building into a beautiful self- sufficient architectural building getting free renewable electrical and thermal energy and free façade insulation from the innovative modules. The area used by the residents in a multi-story building is much higher than the roof area available for solar modules. Thus, the facades of the building must also be used for PV if possible. The aim of the project was to demonstrate efficient use of the limited space in a multi-story urban building for renewable energy supply for self-sufficiency from solar BIPV/T modules. The aim was also to prove and demonstrate that the combination of all features such as Cost effectiveness – Building integration – Architecture – Insulation could realistically be made in one BIPVT unit.

The demonstration of this multifunctional energy building renovation was tested and simulated by detailed minute by minute continuous measurements over 3 years with a large number of parameters. This innovative multifunctional integration and insulation by such high thermal energy efficiency generated from architectural PV modules has not been shown elsewhere on residential building blocks.

For building renovations: The project demonstrated successfully, as expected from the previous evaluation project phase 1, that this PVT and energy efficiency system will be cost effective for many old buildings in cities that need renovation anyway. Thus, the energy gains from this PVT system could significantly reduce the other costs of a standard building renovation. For new buildings: new multi-story buildings, such as the new very demanding residential block and the “BOLIG+” concept which should generate more energy than it uses, this demonstration project proved the potentials of cost efficiency and energy efficient solutions.

Project partners: DTU, Solar City Denmark, MAP Architects, PRIEDEMANN/Facade-Lab

SunTune - High-efficiency solar cells by spectral transformation using nano-optical enhancement

Aarhus Universitet

Innovationsfonden:   2015 – 2019

The SunTune project seeks to develop new solar cells that can convert light to power from a broader spectrum of the frequencies that make up sunlight.

The total annual radiation from the Sun on the surface of the earth is almost 10,000 times more powerful than our annual global power consumption. However, the exploitation of solar energy is still not sufficiently cost effective. In order to improve this, one must develop less expensive solar cells and/or increase their efficiency. Conventional solar cells will normally suffer a 70% loss from the incoming solar energy, among other things because the long-wavelength part of the sunlight is not absorbed. SunTune will exploit the long-wavelength light by effectively “tuning” the sunlight spectrum inside the solar cell to better match the range of efficient current generation. To achieve this, a method for the (up-) conversion of two low-energy photons into one high-energy photon (which can then generate current) will be developed. SunTune will optimize this process by employing advanced nanotechnology inside the solar cell. This will lead to an increased current generation – particularly during morning- and evening-light illumination, where the long-wavelength light is more abundant. The project investigates the underlying physical mechanisms and develops materials, which support the most efficient conversion of light. The consortium consists of a unique collection of Danish and international researchers with expertise of pivotal importance for the execution of the project, and of representatives from Danish companies, which are active in solar cell manufacturing as well as in promoting their use for the production of electricity. SunTune will thus contribute to the goal of making Denmark independent of fossil fuels by 2050.

Project partners: DTU, SDU, RACELL, ISC-Konstanz, ENIIG

Development of a combined solar PV and solar collector module (PVT) for apartment buildings (Phase I)

Racell Saphire Technologies ApS

EUDP:   2013 – 2014

The project aims to develop a PVT module that combines insulation with a solar panel as an integrated building component intended for the renovation of apartment buildings. The building envelope is converted to an active device that is thermally insulated and delivers electricity and heat.

The project should develop a PVT module which is integrated with the insulation of the façade wall. The focus is on typical apartment buildings. The module will be a building element that is fully integrated with the wall or roof of the building. It will be glued or screwed directly onto the building wall or acts as a roof. Mounting rails and installation of these become unnecessary.

This integration of solar PV with solar collectors means that solar cells will be warmer, whereby the production of electricity will decline (0.5 % per C). To counteract this, the module is cooled by a solar collector, thereby increasing the electricity production.

This Phase 1 comprised development and testing of PVT modules. A subsequent Phase 2 is the development of a total solution, including the thermal part, heat pumps and a battery solution and demonstration on a large scale on a residential building in Nørrebrogade.

The project was based on Racell’s technology and production equipment for manufacturing of PVT modules with monocrystalline cells. These will be integrated with insulation solutions from the company STO Denmark, which has developed flexible solutions to insulation of external walls.

In Phase 1 of the project some of the most decisive results were two innovative module types (both being patented). One included an innovative mounting element, an Omega steel profile incapsulated together with the PV cells, so that any mounting system element could be adapted to this profile. Thus, it would fit both with the REDAir and the STO systems. A variant of this new technology proved that an 8m2 and 200 kg heavy PV iSOL glass module could be mounted on a raw wall within 30 minutes only. The second innovative breakthrough was a light-weight module to be mounted on any roof, reducing the system weight from 31 kg/m2 to only 12 kg/m2. Measurements and stress tests combined with theoretical calculations of the static effects and wind suction and loads proved that this new type would be extremely durable. Also, in the case of fire. Another successful result was that the PV iSOL module enabled drilling and cutting in the actual module.

Project partners: DTU, STO, MAP Architects, A/B Nørrebrogade 223, Arkitema Architects

Plug and Play PVT Roof by STRONG lightweight BIPV modules ”Hercules”

Egedal kommune

EUDP:   2013 – 2017                                                                                                                                                                                                                                       

The aim of the project was to develop very large self-sustainable PV or PVT modules with associated flashings which can replace existing roofing on storage buildings such as sport halls, sheds, warehouses, etc. where very long, 4m or longer, large modules are needed. For the first time ever, it was demonstrated that PVT modules could be fully integrated as the actual self-bearing roof. After developing the PVT modules and mounting techniques, it was proven that it is possible to mount a PVT Hercules roof of 250m2 and within 2 days only. Faster than a standard roof. The self-sustainable modules were set up at a sports facility where they produce much more energy than the building could consume. Building integration of solar energy installations is gaining interest and the project has contributed to the dissemination of architectural custom installations for solar energy. Hercules modules and engineering were also developed and planned for a large school, a sports hall with 1000 m2 roof and for a 5000 m2 PVT solar park.

Project partners: Municipality of Egedal, RAMBØLL, MAP Architects, TST-C GmbH, DTI, Lindab

Large scale solar production technology meets architects.

Racell Saphire Technologies ApS

ForskEL:   2007 – 2010

The project objective was to focus on establishing a foundation for the production of cost-efficient PVs and develop PV modules meeting architectural requirements. The full value chain from silicon crystals to the production of cells for the production of modules was partly reformed and redeveloped so that the technology can easily be adjusted and meet the architectural requirements in the future.

Several new innovative multifunctional module types were designed and tested. A connection with cost-effective new innovative special cells was established. Furthermore, new power supply systems have been developed to suit the multifunctional special modules. Finally, principles were developed for new types of production equipment and a new type of module production plant, which can produce complex modules at the same price as standard modules.

Project partners: Henning Larsen Architects A/S, Aarhus University, Grundfos Management A/S, Damarks Tekniske Universitet; Holcher Industriel Design ApS

Technical silicon for high-efficiency PV cells

Racell Saphire Technologies ApS

ForskEL:   2006 – 2012

The project proved that by focused control on the mix of certain impurities in the MG Si feedstock followed by focused gettering during cell processing, stable low-cost MG Si based high efficiency cells could be mass produced at the same high level as for EG Si based cells. Several MG based modules were produced and proved homogeneity and repeatability.

Causes and defect structures for instabilities in MG Si cells by reverse voltage breakdown were found. The role of impurity complexes or clusters were systematically analysed. Unknown clusters distributed at micro boundaries were discovered. These vast numbers of clusters could be used for internal gettering. Some new complexes turned out to have a far more significant impact than the hitherto typically suspected impurities. For example, whereas researchers typically have tried to reduce the midgap energy levels created by complex pairs of Fe-B, B-O, Cu-related defects, it was found by surprise that in the MG Si material, S and Na are active electrically and found in large concentrations. The project has introduced new methodologies of detecting and differentiating high impact impurity complexes. Thus, new MG Si based ultra-high efficiency cell designs can be developed in the future radically minimizing the energy consumption used for purifying the crystalline Si material. The energy pay-back time for PV is thus reduced by orders of magnitude without reducing the efficiency and stability of the PV cells.

Project partners: Aarhus University, ELKEM

Kosteffektive Intelligente Solceller "KIS"

Racell Saphire Technologies ApS

ForskEL:   2005 – 2012

The KIS project aim was to develop new intelligent c-Si cells through innovative production processes at low costs. This was to be achieved by the inclusion of integrated circuits in the actual PV wafer thus facilitating several new applications and designs providing cost effectiveness, intelligence, cell safety against hot spots, stability, and less load and ohmic losses. The KIS cells also provide higher yearly kWh yield compared to traditional high efficiency cells.

The inspiration for the KIS project was the fact that, although PV cells are based on semiconductor material known to be used for the integrated circuit industry, state-of-the-art is that the solar cell has got only one single semiconductor component, namely the emitter diode forming the pn-junction of the cell. So far, all attempts made to introduce new additional semiconductor components into the solar cell wafer have failed. The technological barrier for this has been the lack of alternatives to the extremely expensive Photoresist masking technique and thus the lack of cost-effective technologies for achieving the integration of IC components inside the solar wafer. However, with the KIS project, we have actually managed to integrate new additional semiconductor components in the solar wafer without using Photoresist and without compromising the production costs by combining new designs and new technologies.

Other outcomes from the KIS project are cost benefits from: (1) very large wafer area (2) enabling use of very low-cost Silicon (3) Low current, higher cell efficiency and elimination of the metal grid (4) higher yearly kWh yield by integrated bypass diodes (5) eliminating hot-spot risks and fire hazards and (6) reducing costs of installation of modules. The large area KIS wafer designs are expected to considerably reduce both the Silicon costs, the wafer production costs, the cell production costs, and the module production costs. Further important economic benefits were achieved by the system energy harvesting gains. By introducing a built-in bypass diode for every single cell unit, the new KIS cell modules are expected to provide 5-35% higher yearly kWh/m2 yields than modules based on standard PV cells. Furthermore, the resulting small currents from the small cells could also reduce the use of metal grids on the cell surface, bringing a twofold benefit, higher efficiency and less use of expensive silver pastes. In total the KIS design and production technologies are assumed to halve the material and production costs for solar cells.

Project partners: Aarhus University – Institute of Physics