Monitoring solar irradiance and PV module performance in mobile applications

The paper presents a comprehensive evaluation of a PV module attached to an electric vehicle using a custom developed PV monitoring system to estimate the effect of PV energy production on the driving range. A rigid crystalline silicon photovoltaic (PV) module with a nominal peak power of 192.4 W accompanied with four irradiance sensors (positioned horizontally and vertically to the left, right and back) was mounted on an electric car, and various driving scenarios were executed, with data recorded for analysis. The results of a two-month continuous monitoring of the car's usage mainly in the Central Slovenia region in late winter and early springtime, show that the daily energy generation by the installed PV module contributed an additional driving range of up to 5 km per day, totalling 93 km of additional range in the entire monitoring period. Based on irradiance monitoring results applied to a hypothetical case where all sides would be covered with a state-of-the-art PV, the driving range would extent to 471 km in total for the same period. When compared to a fixed, ideally installed PV module at our outdoor PV monitoring site in Ljubljana, the average performance ratio (PR) of the mobile PV module in the two-month period was 87 %, whereas the PR of the fixed installed PV module was 83 %. The energy yield varied significantly under the varying conditions resulting from different car usage scenarios and on average it reached 41 % of the fixed PV module's energy yield. Through real-world experiments and data collection, different car use cases under various driving and parking conditions are presented and evaluated in detail. From these, the base specifications of a dedicated mobile VIPV monitoring system are identified.