The next generation of solar power might be waiting beneath the Pacific waves, in the form of an armchair-sized clam. Newly-discovered cells in the clam’s mantle concentrate sunlight from multiple directions straight into photosynthetic symbionts in the clam’s body called zooxanthellae. These cells help also mitigate the impacts of excessive heat, a problem in current photovoltaic cells, and as an added bonus help give giant clams their beautiful, vibrant colors. Taking full advantage of geometry, the zooxanthellae are arranged in columns along the side of the clam’s body, not just underneath the shell opening, allowing the maximum number of zooxanthellae to take advantage of the sunlight directed in by the mantle cells. Thus, even with the shell mostly closed, the little zooxanthellae can continue to photosynthesize away no matter what the position of the sun is.
If this sounds familiar, that’s because it mirrors existing technology but is far superior. The mantle cells effectively make the clam’s body into a type of solar plant called a concentrating solar plant. Located primarily in desert areas, these facilities use computer-programmed mirrors to direct sunlight onto a pipe filled with water or oil and heat it. The resulting steam will power a turbine to generate electricity.
The whole process is described by Frank Kreith and Richard Meyer in American Scientist. Kreith and Meyer point out that the computer guided moving mirrors are very expensive, so adapting the clam’s ability to direct sunlight from multiple directions without moving would be a major breakthrough. Concentrated solar plants have a large footprint, taking up habitat needed by wildlife, a problem that might be mitigated by the clam’s compact design. The clam may even prove valuable for traditional solar panels; a coating derived from the mantle shells could allow photovoltaic cells to operate efficiently under higher temperatures than is currently possible.
So long live the clams! As if an iridescent, dishwasher sized clam was not amazing enough, now they have also solved problems that have stumped solar engineers. It is a pity that these magnificent bivalves, which can weigh upwards of 200kg and live more than 100 years, are under threat, desired for both sushi and traditional medicine. Whenever an amazing discovery is made in such an unlikely place, it’s a powerful motivation to preserve life in all its diverse forms. When in search of the next great inspiration, nowhere is too offbeat to look. Leave no clam unturned!