Solar Sneaks in the Back Door

"California Supports PV with Net Energy Metering" (p. 6) reports that residential customers in California with photovoltaic (PV) systems will soon be charged for "net" electricity use, rather than receiving separate bills for that home's consumption (at a high rate) and generation (at a low rate). This decision-modest as it is-sets the stage for additional use of photovoltaic in homes. For homes already on the grid, it means that anybody can add a PV collector (such as the new PV shingles discussed in "Atlanta House a Showcase for Energy Efficiency," p. 8) to provide a portion of the home's electrical demand-with much less ancillary equipment and oversight. Batteries and complex controls-the bugaboo of many PV systems-aren't needed because the utility grid serves as a sort of economic storage for the power. The lack of storage batteries would make PV more environmentally benign. On the other hand, people may want to retain batteries so that they have a source of energy during a supply interruption. It's too early to know what configuration will be the most popular, so we will have to wait and watch.

Another trend is the increasing number of PV applications that are graduating from the "gadgets" catalogs to sensible alternatives. These generally occur when connecting to the grid is unacceptably expensive. One application of PV is particularly intriguing. Thanks to falling costs of PV arrays, many homes are now using PVs to operate exterior lights (see "Small PV Grows in the Garden," p. 6). This option is attractive because these low-voltage systems can be easily installed without connecting to the house's 120-volt wiring. But the system is feasible only because high-efficiency lights can stretch the battery's capacity to a few hours per night. PV-powered attic ventilation fans have also hit the market. In Japan, at least two companies sell a PV air conditioner. The cost of the electricity is very high (over $1/kWh), and the utilities are encouraging customers to buy these units in order to reduce the summer electrical peak.

Other PV applications are beginning to appear, such as powering small pumps and battery chargers. In each case, they are attractive because the cost of the alternative is unusually high, and the application itself uses the electricity very efficiently. As the cost of PV falls-and the efficiency of devices increases-solar will find more applications. It won't happen overnight as some enthusiasts would like, but gradually, first in the odd niches and then in mainstream applications.


 
 

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