Eco-efficiency of CdTe photovoltaics with tracking systems

Abstract

Eco-efficiency is a management practice based on creating more value with less environmental impact. Tracking systems provide the benefit of boosting the specific yield (kWh/kWp/yr) of photovoltaic (PV) systems, therefore requiring fewer modules per kWh produced than fixed-tilt systems. Although life cycle balance of system (BOS) environmental impacts for tracking systems are higher per kWh produced than for fixed-tilt systems, this difference is counteracted by tracking systems requiring fewer modules manufactured upstream and decommissioned downstream per kWh produced than fixed-tilt systems. The life cycle carbon footprint and energy payback time/non-renewable energy payback time (EPBT/NREPBT) of utility-scale cadmium telluride (CdTe) PV systems in the U.S. Southwest range from 16-17 g CO2e/kWh and 0.6-0.7 yr, respectively, with impacts for tracking systems slightly (1-3%) lower than for fixed-tilt systems. Similarly, although tracking systems have slightly higher construction and operations and maintenance (O&M) costs per watt than fixed-tilt systems, these costs are counteracted by the improved specific yield of tracking systems, resulting in lower cost per kWh in the U.S. Southwest case study considered in this evaluation (global horizontal irradiation of 1952-2094 kWh/m2/yr). Because tracking systems have the potential to create more value (kWh/$) with less life cycle environmental impact, they provide an eco-efficient strategy for improving the sustainability of PV systems. A key factor influencing the eco-efficiency of tracking systems is the tracking energy gain relative to fixed-tilt systems, which generally ranges from 10-24% over tropical and subtropical latitudes and is determined by project design, site latitude, and the proportion of diffuse horizontal insolation to global horizontal insolation at the site.