Technological watch

Solar photovoltaic (PV) modules submerged underwater can provide useful power to various types of electronic sensors and robotic vehicles, which may be used for scientific research and defense applications. In the present work, outdoor performance evaluation of a 50 W monocrystalline PV module submerged in water is presented. Experiments were conducted in the morning and noontime to study the effect of varying solar irradiance on module power output. At a depth of?~?0.3 m underwater, the module provided 20.77 W of power, showing a power loss of about 35% in the noontime. Reduction in photocurrent was the dominant factor responsible for the observed power loss. Water also provided cooling to the PV module, and consequently no significant variation in open-circuit voltage was observed. Appreciable values of power were obtained for various water depths and varying solar irradiance values. Spectral response study showed that visible light (400–700 nm) is poorly absorbed, and the infra-red (700–1100 nm) region of the solar spectrum is significantly absorbed by water. Consequently, a substantial drop in photocurrent is observed even at shallow water depths of 5–10 cm. Si solar cells may find practical use in submarine PV applications due to their good visible light response.