Using technologies such as photovoltaic, solar heating, solar thermal energy, solar architecture, molten salt power plants, and artificial photosynthesis from the radiant light and heat from the Sun, solar energy is harnessed.
Solar energy technologies’ long history is between 1860 and the First World War. Technologies were developed to generate steam by using the sunlight’s heat that runs engines and pumps. Solar energy technologies were classified as passive and active, thermal and photovoltaic, and concentrating and non-concentrating. Passive solar energy technology merely harnesses the energy without conversion of heat or light into other forms while active solar energy technology refers to the harnessing of solar energy to store it or convert it for other applications which can be classified into two groups, photovoltaic (PV) and solar thermal. Solar PV cells were invented at Bell Labs in the United States in 1954, and they were used in space satellites for electricity generation since the late 1950s. PV technology converts stored radiant energy in light quanta into electrical energy when light touches upon a semiconductor material, that causes electron excitation and strongly enhancing conductivity. There are two types of PV technology are currently available in the market, crystalline silicon-based PV cells and thin-film technologies that are made out of different semi-conductor materials which include cadmium-telluride amorphous silicon, and copper indium gallium diselenide. And the two types of PV systems exist in the markets are the grid-connected or centralized systems and the off-grid or decentralized systems. The recent trend is strong growth in centralized PV development operating as centralized power plants with installations over 200 kW. The leading markets for these applications include the United States Germany, Spain, and Italy. Solar thermal technologies use solar heat that can be used directly for thermal/heating applications or electricity generation. Accordingly, it can be categorized into two, the solar thermal electric and solar thermal nonelectric. Solar thermal nonelectric includes applications such as solar water heaters, solar cookers, solar air heaters, solar cooling systems, and agricultural drying while solar thermal electric refers to the use of solar heat to produce steam for electricity generation, also known as concentrated solar power (CSP). There are four types of CSP technologies that are currently available in the market, the Parabolic Trough, Power Tower, Fresnel Mirror, and Solar Dish Collector.
The largest source of renewable energy supply is represented by Solar Energy. Effective solar irradiance reaching the surface of the Earth ranges from about 0.06kW/m2 at the highest latitudes to 0.25kW/m2 at low latitudes. Some examples of large solar thermal projects currently under construction or in the development stage around the world include a 500 MW solar thermal plant which is in Spain, a 500MW solar dish park in California, and 30 MW plants, one each in India, Egypt, Morocco, and Mexico. A German solar energy technology company, Solar Millennium AG, is working with its Chinese counterpart, Inner Mongolia Ruyi Industry Co. Ltd., to build a multi-billion dollar CSP plant in northern China that can generate 1 GW by 2020. The Mediterranean Solar Plan announced in July 2008 that seeks to pursue the development of 20 GW of renewable energy for the Mediterranean region. Some private companies have announced plans to develop 100 GW CSP capacity in the Sahara Desert to supply electricity to Europe. The CSP market first emerged in the early 1980s but lost pace because of the absence of government support in the United States. By the early 1990s, off-grid applications accounted for about twenty percent of the market, based on power volume, while grid-connected systems accounted for about eleven percent. The rest of the market was comprised of remote stand-alone applications such as water pumping, communications, consumer products, leisure, and so forth. Between 1995 and 1998, for the first time, the market share of grid-connected systems eclipsed off-grid systems when it grew to twenty-three of the PV installations. Since that time the grid-connected PV capacity has dominated the market through growth rates. In 2006 and 2007, this market attained fifty percent annual increases in cumulative installed capacity then in 2008 the growth further increased to seventy percent. However, a recent strong revival of this market is evident with 14.5 GW in different stages of development across twenty countries and 740 MW additional CSP capacity between 2007 and 2010 while many regions of the world, the Southwestern United States, Spain, China, Morocco, South Africa, Israel, India, and Algeria, provide suitable conditions for the deployment of CSP. The market activity focused in the Southwestern United States and Spain, is supported by investment tax credits, feed-in tariffs, and favorable policies.
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Now, a wide variety of solar energy technologies compete in different energy markets, remarkably centralized power supply, off-grid or stand-alone applications, and grid-connected distributed power generation. Large-scale PV and CSP technologies, for instance, compete with technologies to serve the centralized grid. On the other hand, small-scale solar energy systems, which are part of distributed energy resource (DER) systems, compete with several other technologies such as diesel generation sets, off-grid wind power, etc. The traditional approach to comparing the cost of generating electricity from different technologies depends on the “Levelized cost” method. In electricity systems, which encounter expensive natural gas, the Levelized cost of simple cycle gas turbine technologies is much higher compared to other conventional technologies for the reason that the utilities dispatch this technology only when the other technologies are unavailable, resulting in a small capacity utilization factor. Although in some systems where the major source for electricity generation is natural gas, a gas-fired power plant could be also used to serve the baseload. In such cases, the capacity factor could be as high as eighty-five percent and its Levelized cost would be lower.
The installation of solar energy technologies has an overwhelming growth at the global level over the last decade. The growth of solar energy has been phenomenal in recent years because of improvements in technologies resulting in a reduction of cost and government policies supporting renewable energy development and utilization. Understanding the technical, economic, and policy aspects in the development and deployment of solar energy while the cost of solar energy has declined rapidly, it is still more costly than the cost of conventional energy technologies. Solar energy benefits from regulatory and fiscal mandates and incentives that include tax credits and exemptions, preferential interest rates, feed-in-tariff, renewable portfolio standards, and voluntary green power programs in many countries. Despite the huge potential in technical, development, and large-scale, market-driven deployment of solar energy technologies world-wide must overcome a few technical and financial barriers. Maintaining and increasing electricity supplies from solar energy will require the continuation of potentially costly policy supports unless these barriers are overcome.
