Quantity of ammonia in dew

Abstract

This study investigates experimentally the impact of droplets on the performance of solar photovoltaic (PV) cells due to dropwise condensation or rain falling on their cover. Dew formation occurs frequently in various climates including in semi-arid regions suitable to PV cell deployment. Then, droplets present on the cover of solar cells can negatively affect the cell power generation and efficiency due to optical effects. Here, semi-transparent glass covers were prepared without or with surface treatments and covered with acrylic droplets with contact angle ranging between 25° and 77° and surface area coverage between 19% and 49%. The current vs. voltage curves of commercial polycrystalline silicon solar cells with dry and droplet-covered glass covers were measured under simulated solar irradiation at incidence angle varying between 0° and 85°. For incident angles θi ≤ 30°, the droplets did not affect the performance of the PV cells. However, for incident angles θi > 30°, the presence of droplets caused the maximum power and energy conversion efficiency of the PV cells to decrease significantly, particularly for large droplet contact angle and/or surface area coverage. Such performance degradation was attributed to the fact that the incident light was back-scattered through the droplets instead of being trapped by total internal reflection at the cover/air interface before being eventually absorbed by the solar cell. The study also shows that the hourly energy production of PV cells can decrease significantly with dew formation, based on actual weather conditions. These results highlight the importance of selecting durable hydrophilic solar cell cover.