Offshore floating PV yield considering wave effect

Abstract

The growing global energy demand and correlated rise in carbon emissions are increasing the need of renewable energy sources. This spread requires land to be occupied, competing with other activities such as agriculture and residency. This project can help the spread of photovoltaic (PV) technologies in an environment still little explored: the water. Offshore floating photovoltaic (OFPV) gains increasing attention in research due to a substantial reduction in land occupancy and a lower operating temperature. Therefore, this study aims to evaluate the power output of a OFPV system located in the North Sea considering the effect of the waves on tilt and azimuth of PV modules.

First, the JONSWAP spectrum theory was employed to simulate the sea surface. Then, the interaction between the waves and the floater was modelled to obtain the orientation of the PV modules. The system energy yield was simulated through the PVMD Toolbox, a physics-based tool developed by the PhotoVoltaic Materials Devices Group (PVMD Group) at Delft University of Technology. Finally, experimental analysis was conducted on a commercial string inverter emulating the DC power output from the OFPV modelled plant.

The waves generally cause lower irradiance hitting PV modules. However, fluctuations do not always have a negative influence. For example, the research found that with a calm sea, a system under the effect of waves produces 1% more than an offshore stationary 0° tilt plant. Nevertheless, the variable PV orientation scenario shows substantial losses for higher sea agitation states compared to the 0° tilt situation. Over a year, an OFPV under waves effect loses 0.84% and 17.97% of the production compared to stationary 0° and optimal installation tilt, respectively. From the laboratory activity, it appeared that with the same irradiance, the oscillations have a negative impact on the efficiency, especially that of the maximum power point tracking (MPPT) block, which reaches -3.2% with rough sea.

In the end, we can conclude that the power output losses are not as dramatic as expected and that the development of OFPV technology will probably depend on future costs for offshore installations and the competition for inland areas.