December 1, 2005

… On the other hand, plastic can replace silicon

Solar cell panels made out of everyday plastics could provide an affordable alternative to the expensive silicon-based panel.

"Solar energy is a clean alternative energy source, said Yang Yang, an engineering professor at the UCLA Henry Samueli School of Engineering and Applied Science. "It's clear, given the current energy crisis, that we need to embrace new sources of renewable energy that are good for our planet. I believe very strongly in using technology to provide affordable options that all consumers can put into practice."

Yang's team is working on a new plastic (or polymer) solar cell, which they are looking at producing at 10% to 20% of the current cost of traditional cells, making the technology more widely available.

The price for quality traditional solar modules typically is around three to four times more expensive than fossil fuel. While prices have dropped since the early 1980s, the solar module itself still represents nearly half of the total installed cost of a traditional solar energy system.

Currently, nearly 90% of solar cells in the world consist of a refined, highly purified type of silicon, the same material used in manufacturing integrated circuits and computer chips. High silicon demand from the computer industry sharply reduced the availability of the material, resulting in prohibitively high costs that rule out solar energy as an option.

Made of a single layer of plastic sandwiched between two conductive electrodes, the team from UCLA said its solar cell is easy to mass-produce and costs much less to make, about one-third of the cost of traditional silicon solar technology. The polymers used in its construction are commercially available in such large quantities that Yang hopes cost-conscious consumers worldwide will quickly adopt the technology.

Independent tests on the solar cell already have received high marks. The National Renewable Energy Laboratory (NREL), in Golden, Colo., helped the UCLA team ensure the accuracy of their efficiency numbers. The efficiency of the cell is the percentage of energy the solar cell gathers from the total amount of energy, or sunshine, that actually hits it.

Right now the cell is at a 4.4 efficiency rating, Yang said. He thinks he will be able to double the efficiency percentage in a very short period of time. The target for polymer solar cell performance is ultimately about 15% to 20% efficiency, with a 15-20 year lifespan. Large-sized silicon modules with the same lifespan typically have a 14% to 18% efficiency rating.

"We hope that ultimately solar energy can be extensively used in the commercial sector as well as the private sector," Yang said. "Imagine solar cells installed in cars to absorb solar energy to replace the traditional use of diesel and gas. People will vie to park their cars on the top level of parking garages so their cars can be charged under sunlight."