Scientists from the United Kingdom and Australia have built an experimental setup to measure solar power loss due to wave motion in deployments of floating PV (FPV) panels. Based on their results, they were also able to derive an empirical equation that shows the power loss is predictable through the rotational amplitude.
“Solar panels undergo periodic motions with the waves, causing a continuous change in tilt angle. The tilt angle variation is a sub-optimal process and leads to a loss of energy harnessing efficiency,” said the academics. “While the mismatch phenomenon is known to exist, there has been a lack of scientific analysis on how the wave-induced motions of FPV are linked with energy efficiency.”
To investigate this phenomenon, the team installed 21 units of 500 W halogen floodlights on top of a wave tank. It measured 30 m long and 1.5 meters wide and was filled with fresh water to a depth of 1.5 m, with flappers on one side and a beach on the other. A 50 W monocrystalline PV panel was then placed on a catamaran-shaped floater with two hulls made of extruded polystyrene (XPS) material. A four-pointing mooring approach was set to restrain the panel's drifting.
A calm-water setting was measured for reference, in addition to ten different scenarios of waves. Those differed in their wave amplitude, wavelength, and wave frequency. Per their measurement, the lowest power loss of 1.5% was measured under a wave amplitude of 0.025 m, wavelength of 1.561 m, and wave frequency of 1 Hz. On the other hand, the most severe power loss of 12.7% was recorded in the case of wave amplitude of 0.05 m, wavelength of 1.730 m, and wave frequency of 0.95 Hz. In the first case, the pitch amplitude was 2.9◦, and in the latter, it was 6.7◦.
Image: Cranfield University, Ocean Engineering, CC BY 4.0
“It should be noted that the tested wave conditions were limited by the facility size and thus generally smaller than those in real seas, which means the pitch angles in real life will be bigger and higher energy loss is expected,” said the team. “A way to get around this is to use the derived empirical equation, which can be inputted with conditions that are not tested.”
According to the researchers, it was found that the power loss value can be predicted by the sin function of the pitch amplitude. “In practice, for an FPV system with a known power rating on calm water, experiments/simulations/analytics may be used to ascertain its rotational amplitude in waves, and then its power loss due to the dominating wave environment may be predicted by the empirical equation, estimating its power rating on deployed sea conditions,” they highlighted.
As a suggested solution to the wave-induced power loss, the group has also proposed the application of breakwaters attachment to a floating solar farm. “The additional building cost would not be significant with respect to calm-water FPV, as the main additional component is the breakwater in the barrier, i.e., the cost does not increase proportionally with the surface coverage,” they emphasized.
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 the UK's Cranfield University, University College London, and Australia's University of New South Wales have conducted the study.
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