PHOtovoltaic STEel Roof: ready to plug BIPV roofing steel envelope based on green innovative technologies and processes

PROJECT DESCRIPTION

BACKGROUND

Solar power output is expected to grow by at least 25% annually over the next 10 years. In order to further enhance the impact of photovoltaic (PV) electricity production, technology costs must be lowered to achieve grid parity.

Two generations of PV technologies have been in mass production to date. These are: mono and polycrystalline silicon (1st generation PV with 86% market share); and second-generation thin film technologies, such as amorphous silicon (a-Si), cadmium telluride (CdTe), and copper-indium-gallium-selenide (CIGS). Thin film PV is expected to reach 20% market share by 2016. A recent study shows that CIGS thin film technologies have a lower carbon footprint than crystalline silicon PV.

OBJECTIVES

The objective of the LIFE-PHOSTER project was to demonstrate cost-effective production processes for steel CIGS solar cells on a pilot scale. The aim was to prepare an innovative steel frame, combining roof and base components, that would lead to lower greenhouse gas emissions and eliminate the need for an aluminium support.

The CIGS coating would be connected directly to the new steel frame. Because the material has a high absorption coefficient, meaning it is efficient at absorbing sunlight, a much thinner film is required than for other semiconductor materials. CIGS devices also offer benefits for end-of-life recycling over other PV technologies.

RESULTS

The PHOSTER project enabled the development of a new universal eco-designed roofing envelope, composed of flexible thin film PV modules mounted on a steel substrate, which did not exist at all before the project. This very innovative achievement was possible thanks to the association of Arcelor Mittal with the Commissariat l'Energie Atomique (CEA), Advanced Coatings & Construction Solutions and Arcelor Mittal Construction. This new solution directly integrates PV cells within flexible steel roofs for industrial buildings, with savings on raw materials and energy (reduced by 15% during the project, with a 28% reduction expected with planned improvements), shorter production times and reductions on the emission of greenhouse gases throughout the whole life cycle of the product. These benefits will be enhanced at the industrial scale, through mass production and economies of scale.

In particular, the solution developed makes it possible to:

reduce by about 50% the GWP (Global Warming Potential) with respect to a framed PV module installed on a metallic roof, representing a gain of more than 70 kg CO2 eq. per module square meter compared to existing solutions;

reduce by 40% the GWP and the primary energy demand for manufacturing of the PV modules;

increase by 8.8% the energy produced (kWh/kWp) thanks, in particular, to the reduction of shadow effects;

produce modules recyclable at a minimum rate of 90% (including 100% of the steel part); and

avoid the use of cadmium, a toxic, rare and hazardous metal commonly used to produce solar cells element.

The project had a high demonstration value, as the technology developed was very innovative with a strong commercial potential. The new product was developed as part of the long-term commercial strategy of the Arcelor Mittal group. During the project, it was already raising interest among other companies and potential clients. The project team actively disseminated material concerning the technology at national and international level, in particular thanks to the involvement of Arcelor Mittal in the European Photovoltaic Industry Association and the "Office franco-allemand pour les Energies Renouvelables".

The solution developed also contributes to the implementation of several EU directives dealing with climate change issues, in particular, the Energy Efficiency Directive (2006/32/EC), the Renewable Energy Directive (2009/28/EC), which aims to increase the use of renewable energy sources, and the European Energy Performance of Buildings Directive (2010/31/EU). The project also contributes to the implementation of the REACH regulation by avoiding the use of cadmium.

The project has a clear long-term benefit for climate change mitigation. Coordinating beneficiary, Arcelor Mittal Maizires Research, calculated that with a target market penetration of 5% (from 2025), 2 000 000 m of non-residential roofs could be equipped each year with Phoster modules in Europe, representing a capacity of production of 100 MWh (million Watt hour) installed yearly. This represents a reduction of GHG emissions of more than 100 000 TeqCO2 per year from 2025, and already of 3 416 TeqCO2 in 2020. The project team estimated that the replication of this new technology in Europe would lead to a reduction of around 16 tons of waste containing cadmium.

Furthermore, the innovative solution developed within the project will make it possible to achieve a faster "grid parity" (about 0.5/Watt-peak (Wp) Watt production), allowing solar energy to be competitive compared to other technologies.