Computation and assessment of solar electrolyzer field performance: comparing coupling strategies
Carbon-free solar fuel generation through use of photovoltaic-driven electrolyzers (PV-ECs) and photoelectrochemical cells (PECs) has recently grown to be a subject of much interest. Advancements have been provided through improved catalytic activity, high-performance tandem PV and extensive materials exploration, development and characterization. The generally accepted figure of merit is solar-to-fuel efficiency (SFE), measured with the device at standard testing conditions (STC) at ‘1 sun’ i.e., 1000 W m−2 insolation, clear sky spectrum, and 25 °C operating temperature. However, this does not offer a comprehensive measure of system performance as actual field operating conditions are rarely close to those used for testing. A thorough understanding of PV-EC field performance under realistic operating conditions can assist in holistic device design and scalability. Here, a model is developed to compute their real-life performance using hourly variation in solar irradiance and air temperature over a one-year period. It is then applied to two systems: a previously reported bench-scale high-efficiency CO2 PV-EC and a MW-scale solar H2O electrolysis system conceptually designed employing commercial solar panels and water electrolyzers. While the use of DC power optimizer devices was shown to increase annual gas yield by up to 5% for an optimally-matched directly-coupled system, the benefit is shown to be much higher for even slightly mismatched systems.