Design for the environment: SHJ module with ultra-low carbon footprint

Abstract

The photovoltaic (PV) industry is reaching an inflection point to become a major source of energy. Last decades brought important technical progression in modules' yield and durability. Already available technical solutions might reach the highest power output and the lowest environmental impact in a module. Nevertheless, cost remains the major driver for innovation; top PV panels must combine cost/delay/yield to reach reasonable market share. Our paper presents the development of silicon heterojunction (SHJ) modules with exemplary power and reliability with significantly reduced environmental impact and components sourced from Europe. In order to guide the technology choice in the design phase, we performed a Life Cycle Assessment (LCA) sensitivity study. For a standard PV module, we identify the main steps to improve in order to reduce its environmental footprint. This guided us to tackle the components with the highest impact on the carbon footprint, namely the wafer, glass front sheet and aluminium frame. The proposed improvements will be tested from technical and economic point of view and assembled within one PV module. At the cell scale, we achieved the reduction of the carbon footprint by reducing the thickness of the wafers issued from the European value chain. Optimisation of metallisation and cell interconnection has limited the consumption of silver (Ag), a critical raw metal. At the module level, we implemented the reduction of glass thickness and the replacement of the aluminium frame with a natural fibre-based frame in a glass-backsheet module configuration. In addition, we applied a ‘design for recycling’ approach for the choice of encapsulant and backsheet. The combination of these innovations led us to the realisation of a 566-Wp recyclable module using a tiling interconnection, cells with an average efficiency of 22.57% with a carbon footprint of 313 kgCO₂eq/kWp.