For instance, the water-based nutrient solution in the solar panel will cause the oil to separate out. Ramachandra envisages a process similar to cream rising to the top in milk.
As he and his collaborators put it, "with at least a boundary layer of water on the diatoms, secreted oil droplets would separate under gravity, rising to the top of a tilted panel forming an unstable emulsion, which should progressively separate. The oil could then be skimmed, very similar to the cream that rises to the top of mammalian milk that has not been homogenized."
Many experts are intrigued by this study but point out that it is still too early to know how it will play out. Mark Hildebrand, a researcher at the Scripps Institution of Oceanography at the University of California, San Diego, says, "A major consideration" in development of such technology "is the economic costs of production."
To date, models have shown that "the only economically viable way to produce the large amount of biomass required to supplant a large portion of our fossil-fuel needs requires an open-pond system," Hildebrand says. Although he does not discount the value of systems such as proposed by Ramachandra, which could be especially useful for research, he says it's still too early to know.
"The basic concept is similar to proposing to grow agriculture crops in greenhouses instead of in open fields," he says. "On a large scale, it just costs too much."
But Ramachandra insists an advantage of the diatom solar panel is that it can be created and maintained with equipment and methods that are inexpensive. This is different from photovoltaic solar panels, which require sophisticated fabrication facilities, Ramachandra says. In tropical countries like India with an abundance of sunlight, biofuel-producing solar panels containing local diatoms could be placed in every village. Investigation has shown that diatom oil can be used as biofuel without further processing, says Ramachandra—another advantage. A further advantage is that diatoms consume carbon dioxide, so the diatom solar panels would be very sustainable.
So far, the team has cultured and studied different diatoms and explored approaches to genetically engineering them, but has yet to build a solar panel. Nevertheless, corporations such as Hindustan Unilever, Ltd., (the Indian subsidiary of the multinational Unilever) have shown interest by talking to the researchers a number of times.
The next step, Ramachandra says, is to figure out how to implement the diatom solar panel at the lowest possible cost.