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Applications General Home Consumer Business Generators Stand Alone Battery Hybrid
Net Metering Utility Power Utility Grid
The Sacramento Municipal Utility District (SMUD) operates this 2-megawatt photovoltaic power plant at Rancho Seco, California. The utility also works with residential and commercial customers on several robust PV programs. As part of the PV Pioneer Program, which SMUD launched in 1993, the utility has installed more than 550 PV systems on the rooftops of customers who volunteered to turn their homes into miniature power plants and help to increase the use of PV. SMUD would like to meet 20% of its customers' energy needs with non-hydro renewable sources by 2011.
When should utilities consider PV power? Actually, large-scale photovoltaic power plants, which consists of many PV arrays working together, can be very useful to utilities in a variety of ways.
For example, utilities can build PV plants much more quickly than they can build conventional fossil or nuclear power plants, because PV arrays are fairly easy to install and connect. Also, utilities can build PV power plants where they're most needed in the grid, because siting PV arrays is usually much easier than siting a conventional power plant. And, unlike conventional power plants, modular PV plants can be expanded incrementally as demand increases. Finally, PV power plants consume no fuel and produce no air or water pollution while they silently generate electricity. This makes PV power an attractive option for utilities that want or need to cut fuel costs while meeting local environmental regulations.
So, why aren't more utilities building PV plants? There are actually several reasons. For example, using current utility accounting practices, PV-generated electricity still costs more than electricity generated by conventional plants in most places, and regulatory agencies require most utilities to supply the lowest-cost electricity. Furthermore, photovoltaic systems produce power only during daylight hours, and their output thus can vary with the weather. Utility planners must therefore treat a PV power plant differently than they would treat a conventional plant.
Despite these obstacles, more utilities are becoming more involved in PV power. For example, DOE, the Electric Power Research Institute, and several utilities have formed a joint venture called Photovoltaics for Utility-Scale Applications (PVUSA). This project operates three pilot test stations in different parts of the country for utility-scale PV systems. The pilot projects allow utilities to experiment with newly developing PV technologies with little financial risk.
In another experiment, utilities are exploring connecting PV systems to the utility grid in places where they have a higher value. For example, adding PV generation near the places where the electricity is used prevents the energy losses associated with sending an electric current long distances through conventional power lines. This means the PV system is worth more to the utility when it can be placed near the customer.
PV systems could also be installed at places in utility distribution system service areas where the population is increasing rapidly. In these places, using PV systems could eliminate a utility's need to increase the size of power lines as well as entire servicing areas. Installing PV systems near other utility distribution equipment, such as substations, can also prevent overloading of the equipment in the substation. For an example of a utility-scale PV application, see the case study in this section.
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