This year marks the 50th birthday of the silicon solar cell. In the last 50 years, this technology has come a long way. Solar cells (along with a battery for storage) are often the preferred power source for electrical devices that can't be easily plugged into the electrical grid. Their convenience has enabled them to penetrate many markets, and they can now be seen along the road powering emergency phones, flashing lights, and in many other applications. In the last few years, the most rapidly growing solar-cell market has been rooftop systems that provide electricity for the house or business underneath the roof.
With the recent growth of the rooftop market, the year 2004 may mark a second milestone—solar-cell power production may top 1 GW. A conventional power plant generates about 1 GW of electricity. Thus, the production of solar cells is reaching a volume that inspires the vision of large-scale production of solar electricity.
Arizona, California, and other states are responding to this opportunity by offering incentives to install solar electrical systems on rooftops or in large fields that are operated by the utilities. The rooftop installations deliver the power where it's needed and offset the retail cost of electricity. Depending on the incentives that are offered, these systems may have payback times of only a few years. Arizona Public Service (APS) is installing fields of systems that rotate to follow the movement of the sun. APS has found that the fields of solar systems can be installed more cheaply and generate more power than similar rooftop systems, opening the possibility for solar systems to be used for wholesale electricity generation. So, stayed tuned, it may not be too many more years before your utility gives you the option of purchasing solar electricity!