Photovoltaics Photovoltaics, the use of semiconductor materials to convert sunlight directly into electricity (and which has been used extensively in space programmes), has seen costs come down from approximately US $1 per kilowatt-hour in 1980 to 20-30 cents per kilowatt-hour today. And with increasing scales of manufacturing and increasing emphasis on thin-film devices, it is expected that electricity costs from photovoltaics will fall below 10 cents per kilowatt-hour early in the next decade. Current annual world production has reached 150 megawatts peak (MWp), and is growing at more than twenty percent per year. This corresponds to a doubling time of less than four years, and many new or expanded manufacturing plants are going on line. In 1998, total production globally increased 20.4 percent compared to 1997, reaching 151.7 MW. The United States leads with total production of 53.7 MW, followed by Japan with 49.2 MW. Since Biomass Many locations in the world are fortunate to have large resources of organic material, called biomass. It occurs in a variety of forms (wood, grasses, crops and crop residues) and can be converted into usable energy in a number of ways. We can burn it, as has been done for centuries and is being done extensively today with wood in developing parts of the world. This runs the risk of adding to existing deforestation, soil loss, declining farm productivity, and increasing likelihood of seasonal flooding. In the long run, one of the most effective ways to use biomass is likely to be gasification, where the gas resulting from conversion of the biomass can either be used as fuel for high efficiency combustion turbines, or as synthesis material for producing liquid fuels. Biomass materials can also serve as a feedstock to produce ethanol, which can be used as a transportation fuel and as an industrial chemical, thus reducing dependence on petroleum. A large number of projects are underway to determine how to cost-effectively use biomass for energy production - e.g., co-firing of biomass and coal in utility boilers, and biogasification of a broad range of organic materials such as bagasse, wood, grasses and even alfalfa. Biomass-based electricity has the important advantage of being a baseload technology (i.e., it can be operated 24 hours a day, unlike electricity derived from intermittent renewable resources such as solar and wind), and is carbon neutral - i.e., the carbon dioxide released during its use is recaptured by the biomass during its growth. Electricity costs are expected to be competitive as long as biomass resource costs remain reasonable, and the revenue to be derived from sale of biomass resources can be an important component in rural economic development. Biomass makes a significant contribution to the energy balance of the IEA, representing about 3 percent of total primary energy supply (TPES). For a number of IEA countries, biomass is one of the major inputs to TPES. Globally, biomass contributes about 14 percent of total final energy demand. For many IEA countries, wood for heating is the major use of biomass, although there is an increasing use of urban and industrial waste to produce electricity and heat as well as biofuels for transport. Increasingly, the use of solid fuels or biogas is expanding in modern combustion systems, such as for cogeneration or industrial processes. Solar Thermal Solar thermal technologies, that provide heat and hot water for residential, commercial and industrial end uses, have a long history of commercial applications. The most widespread applications involve solar architecture (building design) and solar hot water heating. Large numbers of solar thermal systems have been installed over the past 25 years, especially in Europe, Asia and North America. Some analysts have estimated that up to 30 million square metres of solar thermal collectors deliver as much as 16.7 TWh of energy per year. Another form of solar energy uses concentrated sunlight to create heat that can be used to generate steam and/or electricity. Solar thermal electric technologies (traditionally known as solar thermal, but increasingly referred to as concentrating solar power to differentiate it from solar heating of residential air and water) comes in three "flavours": troughs that concentrate sunlight along the axis of parabolic collectors (354 megawatts of parabolic troughs have been operating in the U.S. Mojave Desert since the 1980s and delivering electricity to the California grid); power towers with a central receiver surrounded by a field of concentrating mirrors (experimental towers are currently operating in the U.S. and Spain); and dish-engine systems that use radar-type dishes to focus sunlight on heat-driven engines such as the Stirling engine (currently being tested in 7.5 and 25 kilowatt versions). Electricity costs from the parabolic trough units are in the 10-12 cents per kilowatt-hour range, but can be reduced. Costs of electricity from the other two solar thermal technologies are expected to be even lower than those of the parabolic trough systems, and could reach 4-6 cents per kilowatt-hour when manufactured in commercial quantities. Solar heating For the IEA as a whole, the market for solar thermal energy has expanded in  recent years, although it is stable or decreasing in the United States. In Europe, the market has grown by 18 percent per year throughout the 1990s. There are about 178 manufacturers in Europe and the United States. The companies are generally not large. For example, only 26 companies in Europe have more than 30 employees. Solar thermal power The market for high-temperature solar thermal power systems appears ready for major advances. The technologies are cost-effective and ready for commercial application in regions with the best solar resources. Plants built in the 1980s have proven to be highly reliable and competitive. They also have the advantage of providing dispatchable power when hybridized. While there are few commercial applications to date, forecasts show 700 MW of capacity by 2003 and 5,000 MW by 2010. Wind Many locations throughout the world offer large wind resources. Wind is the fastest growing energy technology in the world today (albeit starting from a small base). Today's highly reliable machines (typically technically available 95-98 percent of the time) provide electricity at under 5 cents per kilowatt-hour at selected sites with above average wind speeds of seven metres per second. The next generation of turbines, currently under development, is expected to cut these energy production costs even further. Use of wind energy is expanding rapidly in many parts of the world, with Europe's installed capacity now significantly exceeding that of the United States. Installed global wind capacity at the end of 1998 reached 9,600 megawatts, and large wind projects are being planned for both developed and developing parts of the world. Total installed capacity globally increased 35 percent to a total of over 9,600 MW between 1997 and 1998. This amounted to a total of 2,100 MW of new installed capacity in 1998. Most of the new installations were in Europe. The average size of installed wind turbines increased to more than 500 kW in the major markets. By the end of 1997 almost 130 turbines of 1 MW capacity or more were in operation. Danish companies command about 60 percent of the global market. Geothermal Geothermal resources - i.e., hot water or steam derived from reservoirs below the surface of the Earth - were first used to generate electricity in Italy in 1904. Today, more than 8,000 megawatts of geothermal power plants are installed worldwide. Rapid expansion of geothermal power is taking place in several regions of the world, most notably in Indonesia, the Phillippines, Mexico, and Central America. Geothermal is a baseload technology, and can be a low-cost option if the hot water or steam resource is at high temperature and near the Earth's surface, e.g., the hot dry steam available at Lardarello in Italy and at the Geysers in California. In the longer term, the energy stored in hot dry rock deeper beneath the Earth's surface has the potential to provide an even larger source of geother mal energy. Hydropower Hydropower is the most mature form of renewable energy, and is already providing a significant share (19 percent) of the world's electricity. Large potential exists for further hydropower development in many developing countries, but significant expansion in developed countries is unlikely to occur unless we succeed in addressing environmental concerns associated with land degradation, fish mortality and de-oxygenation of water passing through the hydropower turbines. Efforts are needed and are just underway to develop a "fish-friendly" turbine that will minimize these adverse environmental effects. Small hydro There is tremendous interest in small hydro applications, where there is good potential and few negative environmental impacts. While data are sketchy throughout the IEA, small hydro capacity in Europe expanded by 709 MW between 1993 and 1996 to reach 9,643 MW. Ocean Energy Ocean energy systems tap the renewable energy available in ocean waves, currents and tides. While still a number of years from commercial deployment, recent developments based on hard-earned past experience give hope that a critical threshold has been passed in designing practical systems. Tests of some advanced-design systems are now underway, and more are expected. Geothermal capacity is increasing. In the United States, the world's leader in geothermal energy, capacity reached 2,850 MW in 1998 and Italy has 558 MW for the same period. Japan increased capacity by 116 MW since 1995 and New Zealand its capacity by 59 MW. Total capacity globally stood at 8,240 MW in 1998.