| Work Detail |
Researchers at Delft University of Technology have modelled various floating offshore photovoltaic structures to discover the design parameters that affect durability and performance.
Using a multiphysics framework integrating mechanical and optoelectrical properties of offshore floating PV systems, researchers at Delft University of Technology (Netherlands) studied the structural loads experienced by various floating PV structures and the associated electrical energy losses.
“Simulations like the ones we performed shed light on which configurations will work best before they are implemented in a pilot system,” corresponding author Alba Alcañiz Moya told pv magazine , noting that the model allowed for things like fatigue testing, extreme loading, and platform lifecycle analysis, “all of which are not easy to do on a physical test rig.”
“Finally, developing such a framework allows us to develop a digital twin of the platform,” he added.
Several float configurations were examined, including single large floats and multiple small floats connected with free hinges. Structural design decisions, as well as wave motions and meteorological conditions such as high winds, irradiance, and optoelectronic performance, were input to calculate performance. The optoelectronic formulation was implemented numerically in Python using the Sandia National Laboratory PVLIB-Python modeling tool.
The results revealed a design trade-off for the number of floats. A lower number of floats seemed to induce less photovoltaic motion and achieve better performance, while a higher number of floats tended to allow for lower spring tension for a more durable structure.
“A greater number of floats increases the stability of the system, as the tension is distributed between them and the hinges allow for greater flexibility of movement. However, this flexibility of movement causes the modules to move more, increasing losses due to power mismatch,” explains Alcañiz Moya. “This compensation gives us the opportunity to identify the optimal balance for each location. In addition, our study provides us with the tools and knowledge necessary to specify this ideal configuration.”
The team looked at the influence of structural properties on power mismatch losses in various scenarios. “The Young’s modulus of the material is seen to influence only the longer floats, where the elastic response predominates,” he noted. “In contrast, changes in the cross-sectional fill ratio affect the shorter floats, where the rigid-body response prevails. The float beam thickness has the most significant effect at different float lengths.”
The results for the 25- and 50-float scenarios showed a dominant elastic response for low float thicknesses and a rigid-body response for high float thicknesses. “As a result, a thinner float resulted in lower mismatch losses, due to the higher strength of the hydroelastic response. A similar trend was observed when varying the fill ratio, with a low fill ratio offering lower power mismatch losses due to the hydroelastic response. Therefore, a low power mismatch loss scenario can be achieved by either a single long float with high flexural stiffness or multiple small floats with lower flexural stiffness,” the researchers say.
“The most surprising result for me was that the power mismatch losses caused by waves were not as high as I expected,” says Alcañiz Moya. “I imagined the modules of a floating system constantly moving due to waves, each with a different orientation. That should create huge power mismatch losses. However, the results showed relatively small power mismatch losses.”
In their concluding remarks, the group underlined the “symbiosis” between offshore wind and solar. “Opting for a large number of small floaters leads to a transition from elastic to rigid body response, with elastic stresses being minimal. Fortunately, the largest misalignment losses occur on sunny and windy winter days, i.e. during periods of low generation. This lower generation can be compensated by the wind turbines, fostering the symbiosis between the two offshore renewable energy sources,” it says.
Details of the study are reported in “ Structural Analysis and Power Losses in Floating Solar Platform in Offshore Environment,” published in Applied Energy .
Looking ahead, the researchers say they will focus on three-dimensional analysis, investigating irregularly shaped floating PV platforms and the interaction with mooring lines. “In addition, the hydroelastic model will be developed to account for ocean wave nonlinearity and structural response. Alternative locations and different floating structures, such as membranes, will also be studied,” they said. |
