Researchers at Yale are looking at an unexpected source of inspiration to enhance solar panel efficiency: the giant clams (Tridacna gigas) of the Western Pacific. These mollusks, living in tropical coral reefs, might revolutionize our approach to solar energy.
The giant clams themselves don't perform photosynthesis but host symbiotic algae on their mantle, which do it for them. These algae, known as zooxanthellae, live symbiotically with the clams and provide nutrients through photosynthesis. In return, the clam offers a protected environment and access to sunlight for the algae.
These giant clams possess a sophisticated internal architecture made of vertical columns covered with a thin light-diffusing layer. This configuration, according to researchers, could make clams the most efficient solar energy harvesting systems in the world.
Alison Sweeney, an associate professor at Yale, explains that despite their exposure to intense sunlight, the clams are actually very dark inside. This characteristic allows for a much more efficient solar conversion than current technologies.
The study published in
PRX: Energy describes an analytical model to determine the maximum efficiency of photosynthetic systems based on the geometry and light diffusion properties of the clams. This research is part of a series of studies exploring biological mechanisms that could inspire new sustainable materials and designs.
The giant clams of Palau, with their symbiotic algae arranged in vertical columns, absorb sunlight after it has been scattered by cells called iridocytes. This arrangement allows for optimal light absorption since the light is evenly distributed around each column of algae.
Credit: Yale University Yale Office of Public Affairs and Communications
The model developed by Sweeney and her team also includes the adaptive behaviors of the clams, such as their ability to stretch in response to variations in sunlight. This adaptation increases quantum efficiency to 67%, compared to only 14% for natural systems like green leaves in tropical environments.
A comparison is made with boreal spruce forests, which share similar light diffusion mechanisms and geometries to the clams, achieving nearly the same quantum efficiency.
Quantum efficiency
Quantum efficiency is a key measure in photobiology and semiconductor physics. It represents the capability of a system to convert photons into electrons. In the context of photosynthetic systems or solar panels, this measure determines how efficiently absorbed light is converted into usable energy.
More specifically, quantum efficiency is defined as the ratio between the number of photons converted into electrons and the total number of photons incident on the system. For instance, a quantum efficiency of 67% means that out of 100 photons received, 67 are converted into electrons.
This measure is crucial for evaluating and comparing the performance of natural and artificial energy systems. In the case of the studied giant clams, their unique structure enables a quantum efficiency far superior to current technologies, thus providing avenues to improve future photovoltaic devices.