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Researchers have measured the power loss of a 50 W panel placed in a 30-meter wave tank. Based on ten different scenarios, they were able to draw up an empirical equation for predicting power loss, with the highest loss measured being 12.7%.
Scientists from the UK and Australia have built an experimental setup to measure solar energy loss due to wave motion in floating photovoltaic (FPV) arrays. Based on their results, they were also able to derive an empirical equation showing that power loss is predictable across rotational amplitude.
“Solar panels undergo periodic wave motions, which causes a continuous change in the tilt angle. The variation in the tilt angle is a suboptimal process and causes a loss of efficiency in energy use,” the academics explain. “Although the mismatch phenomenon is known to exist, there has been a lack of scientific analysis on how wave-induced FPV motions are related to energy efficiency.”
To investigate this phenomenon, the team installed 21 units of 500 W halogen spotlights on top of a wave tank. It was 30 m long and 1.5 m wide and filled with fresh water to a depth of 1.5 m, with fins on one side and a beach on the other. A 50 W monocrystalline photovoltaic panel was then placed on a catamaran-shaped float with two hulls made of extruded polystyrene (XPS) material. A four-point mooring system was attached to slow the panel from drifting.
A calm water situation was measured as a reference, as well as ten different wave scenarios. The amplitude, length and frequency of the waves were different. According to their measurements, the lowest power loss of 1.5% was recorded for a wave amplitude of 0.025 m, a wavelength of 1.561 m and a wave frequency of 1 Hz. On the other hand, the most severe power loss of 12.7% was recorded for a wave amplitude of 0.05 m, a wavelength of 1.730 m and a wave frequency of 0.95 Hz. In the first case, the step amplitude was 2.9?, and in the second, it was 6.7?.
“It should be noted that the wave conditions tested were limited by the size of the installation and were therefore generally smaller than those of real seas, meaning that real-life pitch angles will be larger and greater energy loss is expected,” the team notes. “One way to get around this is to use the empirically derived equation, which can be introduced with untested conditions.”
According to the researchers, it was found that the power loss value can be predicted by the sine function of the pitch amplitude. “In practice, for an FPV system with a known power rating in calm water, experiments/simulations/analysis can be used to determine its roll amplitude in waves, and then its power loss due to the dominant wave environment can be predicted by the empirical equation, estimating its power rating in deployed sea conditions,” they noted.
As a suggested solution to wave-induced power loss, the group has also proposed the application of breakwater attachment to a floating solar farm. “The additional construction cost would not be significant compared to FPV in calm waters, as the main additional component is the barrier breakwater, i.e. the cost does not increase proportionally with the surface coverage,” they stressed.
The results were presented in “ Floating solar power loss due to motions induced by ocean waves: An experimental study,” published in Ocean Engineering . Researchers from Britain’s Cranfield University, University College London and Australia’s University of New South Wales carried out the study. |
