operating temperature increases. Also, the larger the energy gap of the material, the smaller the dark current The ratio of source current to dark current should be made as large as possible for improved operation Single-crystal silicon is still the dominant technology for fabricating PV devices. Polycrystalline, semicrys- talline, and amorphous silicon technologies are developing rapidly to challenge this Highly innovative tech- nologies such as spheral cells are being introduced to reduce costs. Concentrator systems typically employ ilium arsenide or multiple junction cells. Many other materials and thin-film technologies are under inves- tigation as potential candidates PV applications range from milliwatts(consumer electronics) to megawatts(central station plants). They are suitable for portable, remote, stand-alone, and utility-interactive applications. PV systems should be con- sidered as energy sources and their design should maximize the conversion of insolation into useable electrical form. Power requirements of practical loads are met using an energy storage and reconversion system or utility interconnection. Concentrating systems have been designed and operated to provide both electrical and low- grade thermal outputs with combined peak utilization efficiencies approaching 60% The vigorous growth of PV technology is manifested by a doubling of world PV module shipments in six years-from 42 MW in 1989 to 84 MW in 1995. Tens of thousands of small(<1 kW)systems are in operation around the world. Thousands of kilowatt-size systems(1 to 10s of kw) also have been installed and are in operation. Many intermediate-scale systems(10 to 100s of kw)and large-scale systems(1 MW or larger)are being installed by utility-and government-sponsored programs as proof-of-concept experiments and to glean valuable operational data. By 1988, nearly 11 Mw of Pv was interconnected to the utility system in the United States alone. Most were the 1-to 5-kW range. The two major exceptions are the 1-MW Hesperia-Lugo project installed in 1982 and the 6.5-MW Carrisa Plains project installed in 1984, both in California. In Germany, a 340-kW system began operation in 1988 as part of a large program. Switzerland had a plan to install 1 MW of PV in 333 roof-mounted units of 3 kW each. By 1990, the installed capacity of Pv in Italy exceeded 3 MW. Many nations have recognized the vast potential of Pv and have established their own PV programs within the past decade. A view of the 500 kW flat-plate grid-connected PV system installed and operated by the city of Austin electric utility depart ment in Austin, Texas is shown in Figure 60.2. From a capital cost of $7000/kW in 1988 with an associated levelized energy cost of 32</kWh, even with a business-as-usual scenario, a twofold reduction to $3500/kw by 2000 and an additional 3-to-1 reduction to $1175/kW by 2030 are being projected. The corresponding energy costs are 15 and 5</kWh, respectively. These FIGURE 60.2 A view of the city of Austin PV-300 flat-plate grid-connected photovoltaic system. Courtesy of the city of Austin electric utility department) e 2000 by CRC Press LLC© 2000 by CRC Press LLC operating temperature increases. Also, the larger the energy gap of the material, the smaller the dark current. The ratio of source current to dark current should be made as large as possible for improved operation. Single-crystal silicon is still the dominant technology for fabricating PV devices. Polycrystalline, semicrys￾talline, and amorphous silicon technologies are developing rapidly to challenge this. Highly innovative tech￾nologies such as spheral cells are being introduced to reduce costs. Concentrator systems typically employ gallium arsenide or multiple junction cells. Many other materials and thin-film technologies are under inves￾tigation as potential candidates. PV applications range from milliwatts (consumer electronics) to megawatts (central station plants). They are suitable for portable, remote, stand-alone, and utility-interactive applications. PV systems should be con￾sidered as energy sources and their design should maximize the conversion of insolation into useable electrical form. Power requirements of practical loads are met using an energy storage and reconversion system or utility interconnection. Concentrating systems have been designed and operated to provide both electrical and low￾grade thermal outputs with combined peak utilization efficiencies approaching 60%. The vigorous growth of PV technology is manifested by a doubling of world PV module shipments in six years — from 42 MW in 1989 to 84 MW in 1995. Tens of thousands of small (<1 kW) systems are in operation around the world. Thousands of kilowatt-size systems (1 to 10s of kW) also have been installed and are in operation. Many intermediate-scale systems (10 to 100s of kW) and large-scale systems (1 MW or larger) are being installed by utility- and government-sponsored programs as proof-of-concept experiments and to glean valuable operational data. By 1988, nearly 11 MW of PV was interconnected to the utility system in the United States alone. Most were in the 1- to 5-kW range. The two major exceptions are the 1-MW Hesperia-Lugo project installed in 1982 and the 6.5-MW Carrisa Plains project installed in 1984, both in California. In Germany, a 340-kW system began operation in 1988 as part of a large program. Switzerland had a plan to install 1 MW of PV in 333 roof-mounted units of 3 kW each. By 1990, the installed capacity of PV in Italy exceeded 3 MW. Many nations have recognized the vast potential of PV and have established their own PV programs within the past decade. A view of the 300 kW flat-plate grid-connected PV system installed and operated by the city of Austin electric utility depart￾ment in Austin, Texas is shown in Figure 60.2. From a capital cost of $7000/kW in 1988 with an associated levelized energy cost of 32¢/kWh, even with a business-as-usual scenario, a twofold reduction to $3500/kW by 2000 and an additional 3-to-1 reduction to $1175/kW by 2030 are being projected. The corresponding energy costs are 15 and 5¢/kWh, respectively. These FIGURE 60.2 A view of the city of Austin PV-300 flat-plate grid-connected photovoltaic system. (Courtesy of the city of Austin electric utility department.)