Can renewable energy sources power the world?
Can renewable energy sources power the world?

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Can renewable energy sources power the world?

6 Large PV power plants

Large, PV power systems, many on a multi-megawatt scale, have been built to supply power for local or regional electricity grids in a number of countries, including Germany, Switzerland, Italy, China, India and the USA.

Land used for PV can often be compatible with its use for other purposes. For example the 1 MW ‘sun farm’ shown in Figure 10 has been designed to allow ‘wildlife-friendly’ plants to live underneath the PV arrays. The need to avoid overshading of one ground-mounted panel by another, particularly in winter, means that they may only occupy 30–50% of the ground area, particularly at high latitudes, leaving space for wildlife and plants.

Figure 10 This 1 MW ‘sun farm’ in Lincolnshire, UK, is adjacent to a wind farm, with the aim of enabling the higher electricity contribution from wind in winter to compensate for lower electricity output from PV, and vice versa in summer (source: Ecotricity)

Large PV power plants are attractive in those areas of the world that have substantially greater annual total solar radiation than northern Europe, such as North Africa or southern California. Such areas also have clearer skies, which means that the majority of the radiation is direct, making tracking and concentrating systems effective and further increasing the annual energy output.

Figure 11 A 48 MWp solar PV facility in Boulder City, Nevada, USA commissioned in 2011. It uses cadmium telluride cells (Source: Sempra generation).

Activity 3

What do you think are the advantages and disadvantages of large, stand-alone PV plants compared with building-integrated PV systems?

Answer

Advantages:

Large stand-alone PV plants can:

  • Take advantage of economies of scale in purchasing and installing large numbers of PV modules and associated equipment
  • Be located on sites that are optimal in terms of solar radiation

Disadvantages:

  • The electricity they produce is not used onsite and has to be distributed by the grid, which involves transmission losses, and the price paid for the power by a local electricity utility may only be the ‘wholesale’ price at which it can buy power from other sources.
  • Large plants also require substantial areas of land, which has to be purchased or leased, adding to costs – although low-value ‘waste’ land, for example alongside motorways, can be used.
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