CURRENT STATUS OF SOLAR ENERGY TECHNOLOGIES AND MARKETS

7.2.1 TECHNOLOGIES AND RESOURCES

Solar energy refers to sources of energy that can be directly attributed to the light of the sun or the heat that sunlight generates (Bradford, 2006). Solar energy technologies can be classified along the following continu­um: 1) passive and active; 2) thermal and photovoltaic; and 3) concentrat­ing and non-concentrating. Passive solar energy technology merely col­lects the energy without converting the heat or light into other forms. It includes, for example, maximizing the use of day light or heat through building design (Bradford, 2006; Chiras, 2002).

In contrast, active solar energy technology refers to the harnessing of solar energy to store it or convert it for other applications and can be broad­ly classified into two groups: (i) photovoltaic (PV) and (ii) solar thermal. The PV technology converts radiant energy contained in light quanta into electrical energy when light falls upon a semiconductor material, causing electron excitation and strongly enhancing conductivity (Sorensen, 2000).

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Estimates of Technical Potential of Renewable Energy Resources

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Renewable Energy Technologies

 

FIGURE 1: Technical potential of renewable energy technologies

 

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Two types of PV technology are currently available in the market: (a) crys­talline silicon-based PV cells and (b) thin film technologies made out of a range of different semi-conductor materials, including amorphous silicon, cadmium-telluride and copper indium gallium diselenide. Solar thermal technology uses solar heat, which can be used directly for either thermal or heating application or electricity generation. Accordingly, it can be di­vided into two categories: (i) solar thermal non-electric and (ii) solar ther­mal electric. The former includes applications as agricultural drying, solar water heaters, solar air heaters, solar cooling systems and solar cookers (e. g. Weiss et al., 2007); the latter refers to use of solar heat to produce steam for electricity generation, also known as concentrated solar power (CSP). Four types of CSP technologies are currently available in the mar­ket: Parabolic Trough, Fresnel Mirror, Power Tower and Solar Dish Col­lector (Muller-Steinhagen and Trieb, 2004; Taggart 2008a and b; Wolff et al., 2008).

Solar energy technologies have a long history. Between 1860 and the First World War, a range of technologies were developed to generate steam, by capturing the sun’s heat, to run engines and irrigation pumps (Smith, 1995). Solar PV cells were invented at Bell Labs in the United States in 1954, and they have been used in space satellites for electricity generation since the late 1950s (Hoogwijk, 2004). The years immediately following the oil-shock in the seventies saw much interest in the develop­ment and commercialization of solar energy technologies. However, this incipient solar energy industry of the 1970s and early 80s collapsed due to the sharp decline in oil prices and a lack of sustained policy support (Brad­ford, 2006). Solar energy markets have regained momentum since early 2000, exhibiting phenomenal growth recently. The total installed capacity of solar based electricity generation capacity has increased to more than 40 GW by the end of 2010 from almost negligible capacity in the early nineties (REN21, 2011).

Solar energy represents our largest source of renewable energy supply. Effective solar irradiance reaching the earth’s surface ranges from about

0. 06kW/m2 at the highest latitudes to 0.25kW/m2 at low latitudes. Figure 1 compares the technically feasible potential of different renewable energy options using the present conversion efficiencies of available technologies. Even when evaluated on a regional basis, the technical potential of solar energy in most regions of the world is many times greater than current total primary energy consumption in those regions (de Vries et al. 2007).

Table 1 presents regional distribution of annual solar energy potential along with total primary energy demand and total electricity demand in year 2007. As illustrated in the table, solar energy supply is significantly greater than demand at the regional as well as global level.

TABLE 1: Annual technical potential of solar energy and energy demand (Mtoe)

Region

Minimum

technical

potential

Maximum

technical

potential

Primary energy

demand (2008)

Electricity

demand

(2008)

North America

4,322

176,951

2,731

390

Latin America & Caribbean

2,675

80,834

575

74

Western Europe

597

21,826

1,822

266

Central and Eastern Europe

96

3,678

114

14

Former Soviet Union

4,752

206,681

1,038

92

Middle East & North Africa

9,839

264,113

744

70

Sub-Saharan Africa

8,860

227,529

505

27

Pacific Asia

979

23,737

702

76

South Asia

907

31,975

750

61

Centrally Planned Asia

2,746

98,744

2,213

255

Pacific OECD

1,719

54,040

870

140

Total

37,492

1,190,108

12,267

1,446

Note: The minimum and maximum reflect different assumptions regarding annual clear sky irradiance, annual average sky clearance, and available land area. Source: Johansson et al. (2004); IEA (2010)

Kurokawa et al. (2007) estimate that PV cells installed on 4% of the surface area of the world"s deserts would produce enough electricity to meet the world"s current energy consumption. Similarly, EPIA (2007) es­timates that just 0.71% of the European land mass, covered with current PV modules, will meet the continent’s entire electricity consumption. In many regions of the world 1 km2 of land is enough to generate more than 125 gigawatt hours (GWh) of electricity per year through CSP technology. In China, for example, 1% (26,300 km2) of its “wasteland” located in the northern and western regions, where solar radiation is among the highest in the country, can generate electricity equivalent to 1,300 GW—about double the country’s total generation capacity projected for year 2020 (Hang et al, 2007). In the United States, an area of 23,418 km2 in the sun­nier southwestern part of the country can match the present generating capacity of 1,067 GW (Mills and Morgan, 2008).

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