The biggest boosts in power were seen in the situations where improvements are most needed: in locations far from the equator, in winter months and on cloudier days. The new findings, based on both computer modeling and outdoor testing of real modules, have been published in the journal Energy and Environmental Science .
“I think this concept could become an important part of the future of photovoltaics,” explained the paper's senior author, Jeffrey Grossman, the Carl Richard Soderberg Career Development Associate Professor of Power Engineering at MIT.
The MIT team initially used a computer algorithm to explore an enormous variety of possible configurations, and developed analytic software that can test any given configuration under a whole range of latitudes, seasons and weather. Then, to confirm their model's predictions, they built and tested three different arrangements of solar cells on the roof of an MIT laboratory building for several weeks.
While the cost of a given amount of energy generated by such 3-D modules exceeds that of ordinary flat panels, the expense is partially balanced by a much higher energy output for a given footprint, as well as much more uniform power output over the course of a day, over the seasons of the year, and in the face of blockage from clouds or shadows. The improvements make power output more predictable and uniform, which could make integration with the power grid easier than with conventional systems, the authors say. The basic physical reason for the improvement in power output — and for the more uniform output over time — is that the 3-D structures' vertical surfaces can collect much more sunlight during mornings, evenings and winters, when the sun is closer to the horizon, said co-author Marco Bernardi, a graduate student in MIT's Department of Materials Science and Engineering (DMSE).
Accoridng to Grossman the time is ripe for such an innovation because solar cells have become less