Raduk Sally Awuor^1,, Waweru Mugo¹, Mulati David¹

Autonomous underwater vehicles are increasingly used for surface ocean exploration, remote sensing, water-quality monitoring and detailed mapping of ocean floor. These devices typically rely on rechargeable batteries like lithium-ion, and piezoelectric propulsion systems, to provide the electrical energy required to power the vehicles thrust systems. However, some of these devices can incorporate energy harnessing systems such as Photovoltaic (PV) systems, where they can utilize available solar irradiance within the upper layers of the water column, to extend their operational range. In this article, we report on underwater performance of polycrystalline photovoltaic modules under different depths and water conditions. Electrical performance characteristics were analyzed with regard to modified irradiance spectrum traversing water medium. The physical and chemical composition of the water column was investigated and its influence on the decay of irradiance, from white light source, was monitored. A decay in irradiance with depth, from at air mass an irradiance drop to at was noted, and continued to decrease to up to a depth of . The pH of the water column analyzed was and the salinity of the medium was , practical salts units. The measured total dissolved substance in parts per million was 25.6 𝑝𝑝, conductivity in micro Siemens of 51.3µ𝑆/𝑐𝑚 of the column solution and resistivity values of 19.3𝑘Ω. 𝑐𝑚 were also recorded. The concentration of salts in the solution was also monitored and the values of potassium and sodium obtained were and respectively. A comparative analysis was as well carried out on the percentage loss of irradiance with depth and temperature variations at 12.3^oC and 27.7^oC. Most amphibious drones designed for shallow depths typically have power wattages ranging from to , and from the irradiance values by plotting the power curves, a maximum power value of was obtained.

Underwater, Photovoltaic module, lamp irradiance, Attenuation