by Jincy Varughese
In Europe, large flat spaces of land with direct normal irradiance (DNI) levels high enough to support solar utilities are uncommon. Diendorfer et. al (2014), a team of researchers in Vienna, saw untapped potential in the Mediterranean Sea and began researching the feasibility of offshore solar power plants. Aside from the availability of open spaces, building solar power plants offshore has two main advantages. First, a system that revolves on a vertical axis can be easily implemented and is efficient at sun-tracking. Second, unlimited water is readily available for the cooling processes required at solar thermal power plants. In this paper, the use of both Parabolic Trough Collectors (PTC) and Pneumatic Pre-Stressed Solar Concentrators (PPC) are considered. The study evaluates the performance of a preliminary floating solar power plant using a model that accounts for platform motion, sea state, and solar irradiance.
As the motion of the waves can change the angles of the panels, thus affecting the efficiency of solar power plants, sea state along with the irradiance levels must be included as variables in the model. Hourly direct solar irradiance values for the Mediterranean Sea were calculated using data on global horizontal irradiance from 1991 to 1993. Sea state variables which include wave height, mean wave period, and wave direction were also incorporated into the model as was platform motion.
The study found that wave motion and direction has little effect on the efficiency of the power plant during normal operating conditions. Diendorfer et. al did find that efficiency falls in the presence of choppy waves but the performance loss in comparison to land systems is small and also results from a reduction in DNI during stormy weather as well. The study also found that using PPC in offshore solar power plants was more effective than PTC in ensuring alignment, lower in cost, and more resistant to salt water. Although offshore solar power plant development is still in its early stages, Diendorfer et. al conclude that offshore plants are an efficient and feasible means of increasing Europe’s energy supply.
Diendorfer, C., M. Haider, and M. Lauermann. 2014. Performance Analysis of Offshore Solar Power Plants. Energy Procedia 49, 2462-471. http://www.sciencedirect.com/science/article/pii/S1876610214007152.