MIT envisions DIY solar cells made from grass clippings
February 5, 2012
Research scientist Andreas Mershin has a dream to bring inexpensive solar power to the masses, especially those in developing countries. After years of research, he and his team at MIT's Center for Bits and Atoms, along with University of Tennessee biochemist Barry Bruce, have worked out a process that extracts functional photosynthetic molecules from common yard and agricultural waste. If all goes well, in a few years it should be possible to gather up a pile of grass clippings, mix it with a blend of cheap chemicals, paint it on your roof and begin producing electricity. Talk about redefining green power plants!
"Leaves and plants are nature's solar panels. The first step in photosynthesis is to change sunlight into a little bit of electricity that then gets converted into the processes of life," Mershin explained. "If we manage to somehow hijack the molecules that are responsible for photosynthesis in plants and other photosynthetic organisms, and use them to generate electricity for our own needs, this would represent a fantastic and disruptive new step in the way that we generate solar power or electricity in general."
Taking a cue from how light is harvested by densely-packed trees, Mershin and his team have fabricated tiny forests of zinc oxide nanowires interspersed with titanium dioxide "sponges." When this mini array is then coated with the photosynthetic molecule extract, the electricity produced can actually be harvested to do work. The major drawback currently is the low 0.1% efficiency of the experimental cells, but the ongoing flurry of research into biophotovoltaics is expected to boost that to commercially viable levels (at least 1-2%) fairly soon.
One of the team's biggest hurdles was figuring out how to keep the light-gathering molecules functional outside the cellular environment. Eventually, they managed to stabilize the chlorophyll-rich plant extract, also known as Photosystem I, with specially designed surfactant peptides, but then had to contend with the fact that some of its components are susceptible to damage by UV light. Luckily, both zinc oxide and titanium dioxide absorb UV and so afford protection as well as scaffolding for the delicate light-harvesting mixture.
The team's findings are detailed in the paper Self-assembled photosystem-I biophotovoltaics on nanostructured TiO2 and ZnO which was recently published in Nature.
In the video below, Mershin describes how this new approach to harvesting solar energy might bring truly green power to the people.