Current and prospective environmental consequences of integrated vs added photovoltaic roof applications

Climate targets and economic competitiveness have led to large scale employment of photovoltaic (PV) devices. Next to that, technological developments in second and third generation PV, thin-film and flexible cells, has widened the possible application surfaces of PV. An example is building integrated PV, where the PV panels are an integral part of the building envelope. These building integrated photovoltaics (BIPV) are PV materials used to replace conventional building materials in parts of the building such as the roof, façade or windows. BIPV are distinguished from building added photovoltaic (BAPV) where the panels and frames are added to the building with their mounting structure (e.g. on a roof already covered by tiles) or stand-alone land based PV such as solar farms. The differences in these applications might lead to differences in available technology choices, techno-economical and environmental performance. To prevent negative consequences during transition to a zero-carbon energy supply, it is important to gain knowledge on these differences as early as possible.

An accepted tool to get insight in the environmental performance of a product is life cycle assessment (LCA). Although several authors contributed to shedding light on the differences in environmental performance between building added and building integrated PV, definition of integrated PV is not always restricted to the ones replacing part of building materials. Moreover, few authors (e.g. Kristjansdottir et al., 2016) have systematically compared the environmental impacts of providing electricity to houses using different PV systems. However, none of them has investigated these scenarios considering the electricity transition or looking into the inherent differences in replacement options. The aim of this research is to compare the environmental profiles for providing electricity to an average Dutch family house using building integrated or added systems. All systems were designed to fully provide this electricity demand in the first year. Over the 50 years period of analysis part of the electricity is supplied by the grid due to degradation. Differences in replaceability are also taken into account. Scenarios are compared under current and expected electricity provision from the grid.
The following technologies are considered in this research:
• flexible Copper-Indium-Gallium-Selenide (CIGS) semifabricates integrated in steel rooftiles “Integrated CIGS”
• rigid CIGS modules added on ceramic roof tiles “Rigid CIGS”
• rigid crystalline silicon modules, added in ceramic roof tiles “Rigid x-Si”. These are included as a benchmark as this is currently the most commonly PV technology.
Additionally, a scenario has been defined where added PV modules can be replaced after 30 years with more efficient cells. The current and expected future Dutch electricity mix from the grid are used in those scenarios. Inventory data for CIGS modules is taken from in-house data of the mass customization line at TNO and adapted from Van der Hulst et al. (2020). Silicon modules are modelled based on literature. All scenarios are assessed using ReCiPe, 2016. Preliminary results show that, thin-film cells have environmental benefits over benchmarks and flexible over rigid (in terms of carbon footprint and most impact categories). With the current electricity mix, replacing modules with higher efficiency modules has carbon footprint benefits (but not necessarily for other impact categories). If the grid mix itself contains more renewables, this benefit vanishes. In the presentation we also show the effects of changing electricity generation in the production and waste treatment.