This is an excerpt from EERE Network News, a weekly electronic newsletter.

September 17, 2003

Advances in Solar Power Aim for a Touchdown

Solar power technologies advance, in many ways, much like a football team marching down the field: while everyone hopes for that big touchdown pass, most progress is actually achieved gradually, through the combined efforts of many people pushing ahead in every way they can. Three recent news items demonstrate the diversity of approaches that are advancing solar power technologies.

Electrical engineers at Princeton University are trying an end-run around conventional techniques that could yield huge yardage. While most solar cells are built from silicon and other inorganic materials, the Princeton engineers are developing organic solar cells—solar cells built around thin films of organic chemicals. Using a new processing technique, with support in part from DOE's National Renewable Energy Laboratory, the engineers boosted the efficiency of two-layer organic solar cells by 50 percent. Although organic solar cells currently convert only about 3 percent of the sunlight that hits them into electricity, the Princeton researchers are confident of combining new materials and processing techniques to achieve at least 5 percent efficiency, and possibly as high as 10 percent. Although that would be low compared to silicon solar cells, the low cost of the organic solar cells could make them cost-competitive. See the Princeton press release.

Another way to advance solar power is to get more value out of each solar cell, an approach that might be compared to finding a way to make your football passes go farther. A promising technique is to integrate the solar cells into buildings, allowing them to serve a function for the building while also producing power. The latest attempt at such building-integrated solar cells comes from the Rensselaer Polytechnic Institute (RPI), which has built solar cells into pyramid-shaped devices incorporated between the panes of a window. The devices help shade the interior from the sun's harshest rays, while allowing soft daylight into the building. At the same time, the solar cells in the devices generate power. RPI is currently testing two working prototypes of the window system. See the RPI press release.

But real football fans know that a good passing game is best matched by the ability to move the ball on the ground. It's not as glamorous, but the game often hinges on those able to inch the ball ahead with sheer muscle. The solar power equivalent may be the process of growing silicon ingots. Crystalline-silicon solar cells still dominate the solar power market, and arguably the hardest part of making them is the process of growing crystalline silicon ingots, which are then cut up into wafers to create solar cells. Shell Solar has been working with the Northwest Energy Efficiency Alliance to improve the energy efficiency of its crystal-growing furnaces, with considerable success. According to Shell Solar, the company has cut the power use of its furnaces by 30 percent while reducing the time needed to grow a crystal by up to 40 percent. The company has also increased its crystal yield while greatly lowering its use of argon gas. See the Shell Solar press release.