Biomimicry in technology: sparkly clams and floating photovoltaics
By Mihira Reddy, GRC 2024 Global Essay Competition Top 30
Solar systems are the second most widely used renewable energy sources in the world after hydropower, comprising almost 31% of installed renewable energy in 2022 and boasting a capacity of 1053 GW (Pourasl, Reza Vatankhah Barenji, and Khojastehnezhad 2023). If solar energy systems were not constricted to land, there would be a significant increase in both solar capacity and efficiency. This is where floating photovoltaics (FPVs) come in: FPV systems can generate 0.6% to 4.4% more energy compared to traditional land-based systems, and efficiency improvements can range from 0.1% to 4.45% (C.j. et al. 2024). Furthermore, FPVs eliminate the need for increasingly scarce urban land and can mitigate land use conflicts (Krishna Kant Dixit and Arti Badhoutiya 2022). This begs the question as to why FPV systems have not been widely implemented; a question with a rather simple answer: they have several disadvantages that must be considered alongside their various benefits, including but not limited to high maintenance costs, harsher aquatic environmental conditions, and biofouling of the material. Improvements in technology need to be utilized to make FPVs more feasible in a variety of areas. Biomimicry has been an increasingly effective way to advance technology, by modeling living organisms to foster scientific innovations. In the case of FPVs, the giant clam may be the organism for the job. This essay provides insight into the giant clam and how biomimicry can lead to advancements in floating PV technology, greatly benefiting our planet.
Recently, in an interesting development, the geometry of giant, iridescent clams discovered by researchers were used to model a theoretical solar transformer with a quantum efficiency (turning photons into electrons) of up to 67%, as compared to the 3% captured by farm crops for photosynthesis and 20% captured by mass-produced solar cells. The living solar clams can even reach an efficiency beyond this 67%, due to a variety of additional mechanisms that enable this, such as algae columns. The researchers have suggested the design of sustainable biomass systems optimized by the adaptation achieved by giant clams (Holt, Rehm, and Sweeney 2024). However, the adaptations of these giant clams may be used for technological change beyond photosynthetic systems and for solar energy systems as well, namely in improving the technology of floating photovoltaics, and revolutionizing energy production through FPV systems.
Figure 1: (a) The absolute efficiency of the vertical cylinder model of algae seen in the giant clams. b) The absolute efficiency of the random-layer of algae mode.
In an email to Live Science, researcher Dan Morse wrote "The brilliantly reflective cells of the giant clam actually redirect photons from sunlight deeper into the clam's tissue, gently and uniformly illuminating millions of symbiotic algae that live there, so they can provide nutrients to their animal host by photosynthesis." (Laura Geggel 2022)
These sparkling clams have photonic crystal structures that improve their energy efficiency. These crystals can be used to scatter light in floating photovoltaics, and a mimicry of the clams crystal structures can result in enhanced light efficiency, while dissipating light within the solar panel to reduce overheating, decreasing photodamage and optimizing space use. Today’s solar cells often overheat when exposed to direct sunlight, which leads to a decrease in efficiency (Pollution Solutions 2014). Using the properties of the giant clam, researchers can develop a solar panel that can stay cool even when exposed to direct sunlight. This self-cooling panel would be a game changer in increasing efficiency.
The layer of iridescent cells called iridocytes in the mantle of the clam scatter light depending on wavelength and angle, and can back-reflect non-productive light (Holt et al. 2014). In FPV systems, a main problem is aquatic ecosystem disturbance as sunlight may not reach the biotic components below the floating photovoltaics. Taking inspiration from the clam, floating PVs can be made to distribute photosynthetically productive wavelengths back into the ocean below, drastically reducing the effects on algae, phytoplankton and other aquatic life.
Furthermore, clams respond to sunlight like sunflowers. In a statement, the lead researcher Alison Sweeney said “Clams like to move and groove throughout the day.” (Luntz 2024) The mantle tissue of the clam inflates, and the columns of algae in the tissue get further apart. The locations of algal columns in active living clam tissue were visualized by using a bright light-emitting diode depicting the expansion of algal columns (Holt, Rehm, and Sweeney 2024). Without this stretching, clams and algae would catch 43% of the energy as compared to 67% – although it is still better than everywhere else, it's much lower. Implementing a stretchy sustainable plastic material technology as mentioned by Sweeney can be adopted for FPVs and would greatly increase efficiency, and reduce maintenance costs.
Figure 2:
Additionally, to reduce maintenance costs of FPVs, antifouling and anti-leaching coatings inspired by the mucus of the clam can be implemented. Moreover, stacking few PV cells in a vertical cylinder similar to the clam in a solar panel, where light is scattered onto a few parallel pillars as opposed to the traditional perpendicular way can lead to a rise in efficiency while decreasing maintenance costs. Also, bioengineered algae can be incorporated in layers into FPV systems that capture unused light wavelengths, as suggested by Sweeney, who stated "One could envision a new generation of solar panels that grow algae..." (Luntz 2024).
In conclusion, biomimicry can help build technologies that can solve all types of problems, especially within the field of sustainability. Giant clams, in specific, can serve as a source of inspiration for various technologies, including biofuels, photosynthetic systems, as well as floating photovoltaics. The integration of biomimicry into FPV technology is an opportunity to address some of the challenges faced by this renewable energy solution as they could become more cost effective and efficient. Research is still needed to make these inspirational clams into actual practical solutions, and future studies should focus on developing and testing biomimetic designs such as algae-integrated FPVs to revolutionize solar energy production.
Bibliography
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