Green Side Out - The green lifestyle

Photo by Gili Soffer

Recent research and development in production has resulted in new solar cells that are getting more and more efficient. Photovoltaic cells have been made from a single material, silicon, which achieves about 25 percent efficiency. New stacked material cells are gaining up to 40 percent or better efficiency in converting light to electrical power energy.

Silicon is used because it is available, though not cheap, but it wastes a lot of sun energy as heat. By using a system of alloys, conversion of almost a full spectrum of sunlight to electrical current is possible. New alloys incorporate indium, gallium, and nitrogen along with some elements of nitrogen and arsenic. They will be more durable and less expensive than single silicon layers.

Research into solar cells and their efficiency has been directed toward making photovoltaic cells more efficient and at the same time, less costly. The return time of the investment has been reduced, that is, the time it takes to recoup the initial cost of production and installation, versus the rewards in lower energy costs from reaping solar energy.

A stacked group of different band gap materials brings better efficiency in capturing and using sunlight energy for electrical current in multi-junction cells. Even a two layer cell of different materials can offer better efficiency than using only silicon material in the cell. Making cells thinner and more light weight are desirable also, to reduce costs. But with thinner silicon cells, efficiency is lost. There is a shortage of refined silicon, which also is keeping solar cell prices higher.

New designs in panel top grid construction are aimed toward better electricity conduction and lower power loss, while allowing more of the cell visible to absorb light. Changes in the bottom layer are also showing an effect on efficiency. Being able to reflect lost light back up to the silicon means a greater amount of light energy can be captured and absorbed.

Solar cells are made of two layers of and light needs to pass through the top layer to reach the second for conversion into electricity. Using typical silver lines on top can be improved by interweaving the silver with copper coated wires that conduct electricity better and do not diffuse when heated to high temperatures through the silicon to create a short circuit.

New solar cells are being designed that use an optical concentrator to increase sunlight intensity, thus resulting in capturing more electricity from the photovoltaic cells. Much current research can be credited to U.S. Department of Energy’s “Solar America Initiative”. The major goal is to reduce costs and open markets, and reduce dependence on foreign oil. New highly efficient units can reduce costs through increased efficiency with fewer but better solar cells.

The target cost for PV system installation is $3 per watt, down from $4. Electricity production cost goals are $0.08 to $0.10 cents per kilowatt-hour. Solar cells are getting more and more efficient, and their use will grow in the coming years as prices for installation and costs decrease and benefits from the lower cost energy production increases.