Most Efficient Solar Panels Ever Found
In the shallow tropical reefs off Palau are enormous clams of the genus Tridacna. While very beautiful, they might seem otherwise unremarkable. However, a closer look at the shimmering blue flesh within their four-foot-long shells reveals an astonishing discovery: these clams host the most efficient solar panels ever found, according to new research.
“The fact that nobody could explain why a clam was iridescent really just stuck with me,” says Alison Sweeney, a Yale University biophysicist and co-author of the study.
In previous research, Sweeney and her colleagues found that despite their impressive iridescence, the clams’ fleshy mantles reflect only about 5 percent of the bright sunlight that hits them. The rest of the light is absorbed and directed to photosynthetic algae within the clam’s body, serving as a food source. This absorption rate is remarkably efficient for photosynthesis; by comparison, terrestrial forests like the Amazon reflect much more light, reducing their photosynthetic efficiency. Specialized cells called iridocytes line the mantle’s surface, containing transparent, protein-rich platelets that diffuse light inward.
In new research published in PRX Energy, Sweeney’s team examined the arrangement of the clams’ symbiotic algae, which are neatly organized in modified tubes extending from the digestive system. Unlike the random distribution of photosynthetic machinery in leaves, the clam’s algae form orderly columns stretching from the iridocyte layer into the flesh. “The clam basically plants them as if it were an agricultural field,” Sweeney explains. (The algae also travel between clams in pellets of feces.)
Modeling this system, the team calculated that its theoretical efficiency at the first step of photosynthesis, where chlorophyll absorbs a photon, is 43 percent—more than twice the efficiency of most current solar panels and three times that of a tropical leaf. Previous measurements in the wild suggested an even higher efficiency of over 60 percent. The new study resolved this discrepancy by considering that clams might inflate and deflate their mantles throughout the day to optimize sunlight exposure, bringing the modeled efficiency to 67 percent.
Sweeney hopes this work can inspire the design of algae-stocked bioreactors, demonstrating how biological solutions can address technological challenges.
Here is a video that shows some of these amazing clams. The best footage starts at 8:32.