Environmental Engineering Reference
In-Depth Information
City
Country
Solar
radiation
kWh/m 2 /year
Usable
energy
kWh/m 2 /year
Area of PV
panels
m 2
Venice
Italy
1,248
115
44
Sydney
Australia
1,840
174
29
Berlin
Germany
1,080
101
50
Notes: The efficiency levels of the solar PV plant are calculated at 10 per cent. The
columnontherightindicatestheareaneededtoproduce5,000kilowatt-hoursperyear,
the electricity consumption of a typical European household.
Source: www.nrel.gov .
Thin flexible film that can be stretched over almost any surface may help to resolve this
conflict. This removes the need to mount the cells on a rigid frame and opens up a range
of futuristic possibilities, including solar cars and solar clothing. However, thin-film cells
have significantly lower conversion efficiencies than silicon does. To compensate for this,
several different films may be layered to create what are known as multijunction PV cells.
In this case, each layer or junction (the word 'junction' is preferred since each cell already
consists of two layers, the p-layer and the n-layer) uses a different type of semiconductor,
each of which absorbs light from a different part of the colour spectrum. In this way, the
multijunction cell is able to maximise energy gain with a typical conversion efficiency
of 30 per cent. The downside of this technology is that it is more complex and therefore
expensive to produce. This disadvantage may be offset by concentrating the sunlight using
mirrors or lenses before it strikes the cells in a technique known as concentrated PV (CPV).
CPV systems are considerably more efficient than flat silicon panels, thus requiring less
PV material to produce the same amount of electricity (see Figure 4.27 ). 12
Search WWH ::




Custom Search