Keeping the lights on: An ongoing report of local power conditions
Uploaded: Tuesday, February 20, 2001 2 p.m.

What is solar power?
Process has grown less expensive

What is thin and light, won't fry a bird at the slightest touch and drives PG&E corporate officers crazy?

Power generated by solar cells.

Solar power has been around since 1941, when Russell Ohi devised the silicon solar cell. A use wasn't found, however, until the space program created the need for power other than what is generated by batteries.

That development created a cottage industry that honed and refined the photovoltaic system to the point where it became viable and then commonplace. Recently NASA employees spent considerable time getting a solar array unfolded for the new space station.

In 1996, NASA launched its Near Earth Asteroid Rendezvous (NEAR) satellite to study an asteroid. The satellite, the first to draw all of its power from solar energy, has now traveled 2 million miles.

Research conducted to accomplish the scientific programs has refined solar power's abilities to where it can be used on earth to provide electricity at a near affordable price.

What are solar cells? They are made of silicon, either single crystalline or multicrystalline, which convert direct sunlight into electricity. What is silicon? Try sand--the stuff you find on the beach.

The very thin cell is made up of four layers: a back contact, two layers of silicon and the blue surface that reflects sunlight. Each cell generates electricity.

A new product should bring the prices down even further--thin film cells that cost just 1 percent of the cost of a crystalline cell and are easy to manufacture, according to the National Institute for Scientific Education.

A single solar cell doesn't generate enough juice to power much of anything, except maybe a weak light bulb, a pocket calculator or a watch. Put a lot of them together and you can power a flashlight, an AM/FM radio, a laptop computer, a home, a business, or even a corporate office.

Solar power creates a direct current that has to be converted to power. That is accomplished by an inverter mounted on the house or business. Because the electricity has been converted to AC, it can be put back into the regular power grid.

One array can generate 120 watts. The Ebenhoech home, a Palo Alto Utilities demonstration project, has 24 Astropower AP 1206 modules, is rated at 2,880 DC watts and at 2,568 AC watts. Each module generates 120 watts. In all, the panels provide 70 percent of the household's needs for electricity. The cost in 1999 was $18,188 or $6.32 per watt before rebate. Gunn High School has large 12 AstroPower LAP-460 panels, rated at 5,520 DC watts or 4,688 AC watts. The cost, in 1999 figures, was $43,408 or $7.80 per DC watt.

--Marv Snow


Palo Alto Online
© 2000 Palo Alto Online.