Project on transparent solar cells for building integration

Elisabeth Tecza Andersen

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Project on transparent solar cells for building integration

More than 40 % of the energy is consumed by buildings
The on-going discussion on climate change, supported by the recently published intergovernmental Panel on Climate Change’s fourth assessment, imposes pressure upon CO2 releasing energy technologies. Moreover, in March 2007, the European Union established a mandatory target that 20 per cent of the energy consumed in the EU should come from renewable energy sources by 2020 (Commission of the European Communities Brussels, 2007). In order to build an energy system that is based on CO2 neutral renewable energy, lock-in mechanisms supporting carbon-based technologies have to be overcome.

Buildings account for at least 40 per cent of energy usage in the world and 84 per cent of the life cycle energy requirement of a building are spent during its use phase for heating, air conditioning, ventilation, lighting, hot water, etc. (World Business Council for Sustainable Development, 2007). Energy efficiency of buildings is thus a major challenge both for actors from the energy sector and the building industry. One solution is the integration of renewable energy into buildings. Particularly, the vision of zero net energy buildings has emerged, which means that the building as a whole produces as much energy as it consumes over a one year period (World Business Council for Sustainable Development, 2007). Building integrated photovoltaics is one of the most promising technologies for achieving this aim.

A sky scraper can provide more than 100 000 sqm façade
Building-integrated photovoltaics (BIPV) are photovoltaic materials that are used to replace conventional building materials in parts of the building envelope such as the roof, skylights, or facades. They are increasingly being incorporated into the construction of new buildings as a principal or ancillary source of electrical power, although existing buildings may be retrofitted with BIPV modules as well. The advantage of integrated photovoltaics over more common non-integrated systems is that the initial cost can be offset by reducing the amount spent on building materials and labour that would normally be used to construct the part of the building that the BIPV modules replace. Dye sensitised solar cells are the most promising technology in the BIPV field, due to the possibilities of making them transparent, flexible and lightweight. In addition, since BIPV are an integral part of the design, they generally blend in better and are more aesthetically appealing than other solar options due to the fact that they can be made into different colours. These advantages make BIPV, and Dye sensitised solar cells one of the fastest growing segments of the photovoltaic research.

The background to this project is the constantly growing market of building integrated photovoltaics and the increasing demand for highly efficient and multi-usable solar cells in different materials and colours. This can only be achieved using either Dye solar cells or Polymer solar cells. The market size for integrated solar cells in sky scraper glass façade is huge with one sky scraper providing more than 100 000 sqm façade.

The Nordic DSC project
The aim of the Nordic DSC project (2009-2012) is to use manufacturing design and process parameters to guide the development of nanotechnology for improved and novel solar cell systems towards production. Specifically the project will concentrate on developing nanomaterials, printing and thin film coating and sealing methods for use in the construction of NLAB Solar’s flexible, transparent solar cells for dual use in exterior architectural shading. New avenues for production will also be developed with regards to the above mentioned compression method. To move the 1DPC concept further towards commercialisation the following consortium has been formed.

The project consortium consists of NLAB Solar AB (manager), Ytkemiska Institutet AB, Scheiwiller Svensson Arkitektkontor AB, Danish Technological Institute, Aalto University School of Science and Technology, Fasadglas Bäcklin AB, and The Spanish National Research Council.

The project is supported by Nordic Innovation Centre.

The work at Danish Technological Institute
The Institute has been working on polymer based printable sealant system for use in the dye solar cells. In order to harvest the energy from the sun, the chemical system inside a solar cell must remain intact. Careful design of the chemical system inside the solar cell can make the system more robust but no matter how robust the chemistry inside is, it must still be protected against the elements when the solar cell is installed for electricity production. The first and foremost protection is a physical barrier consisting of the solar cell substrate and an edge sealant which together produce a cavity wherein the chemistry of light harvesting can take place. This physical barrier serves two purposes. Firstly, it must keep the materials, most notably the electrolyte, within the solar cell and secondly it must keep out unwanted materials. One of the key materials to keep out of the cell is water as it has been shown to degrade cell performance rapidly via hydrolytic and photocatalytic reactions.

Based on the research work at Danish Technological Institute, the following results have been obtained:

  • Identified polymer with good sealing properties
  • Developed a method for printing polymer sealing
  • Determined permeability of electrolyte and water
  • Developed a model for molecular diffusion in sealing materials

The figure shows the pilot plant for production of dye solar cells at NLAB Solar AB
Figure: Pilot plant for production of dye solar cells at NLAB Solar AB