Solar panel and biorefinery designers take note – iridescent giant clams living near tropical coral reefs are showing us how it’s done. These giant clams have intricate geometries that make them potentially the most efficient solar energy systems on Earth.

Alison Sweeney, an associate professor at Yale, explains, “It’s counter-intuitive to a lot of people, but clams, despite living in intense sunlight, are actually really dark on the inside. In truth, clams are more efficient at solar energy conversion than any existing solar panel technology.”

In a study published in the journal PRX: Energy, Sweeney’s research team presents an analytical model that reveals the maximum efficiency of photosynthetic systems based on the unique geometry and light-scattering characteristics of giant clams. This study is part of a series of research projects from Sweeney’s lab that explore how nature’s mechanisms can inspire sustainable materials and designs.

The focus of this particular study is on the solar energy potential of iridescent giant clams in the waters of Palau in the Western Pacific. These clams have single-celled algae growing on their surface, absorbing sunlight through vertical columns, with the help of a light-scattering layer called iridocytes.

The researchers emphasize the importance of both the algae’s arrangement and the light scattering by the iridocytes. The vertical columns of algae, parallel to incoming sunlight, ensure optimal sunlight absorption, enhanced by the scattering and filtering of light by the iridocytes.

By developing a model based on the giant clams’ geometry, Sweeney and her team calculated a quantum efficiency of 42%. However, when factoring in the clams’ stretching behavior in response to sunlight, the efficiency increased to an impressive 67%, compared to just 14% in green leaf systems.

The study also draws a fascinating comparison to boreal spruce forests, noting similar geometries and light-scattering mechanisms, albeit on a larger scale. This highlights the importance of biodiversity in achieving high solar efficiency.

Sweeney points out, “We can only study biodiversity where it is maintained, and we owe a debt to regions like Palau for preserving their natural ecosystems.” Such insights could pave the way for more efficient sustainable energy technologies.

For example, Sweeney envisions a future with solar panels that grow algae or stretchy plastic panels for wider light absorption. The study, funded by the Packard Foundation and the National Science Foundation, highlights the potential for nature-inspired innovation in the renewable energy sector.

With Amanda Holt as the first author and Lincoln Rehm as a co-author, both part of Sweeney’s research team, this study sheds light on the untapped potential of nature’s designs for a greener future.