Download PDF - Pan Stanford Publishing
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26 Introduction to SolarPowerfortheWorld<br />
Annex: Some Facts on PV<br />
• Thickness<br />
The thickness of PV modules is essentially determined by<br />
the supporting pane, normally glass. Solar cells are less than<br />
1/3 mm thick when they are made of silicon crystals and not<br />
more than 1/1000 mm thick when they are thin film.<br />
• Areas<br />
The area of a PV array of PV modules takes normally less<br />
than 10 m 2 /kW. It depends on the cell efficiencies and the<br />
packing density; 1 MW of PV occupies less than 1 ha (2.5<br />
acres); 1 GW occupies an area of less than 10 km 2 (3.86<br />
square miles).<br />
• Electricity Production<br />
For complete PV systems well oriented south at a fixed<br />
inclination corresponding to the latitude of the site, the<br />
annual electric energy production is better than 1000 kWh<br />
for every kW installed, even at bad or mediocre solar<br />
climates. The average for Germany in central Europe is<br />
900 kWh/kW, a capacity factor of 11%. This takes into<br />
account that a non-negligible part of the system park is<br />
not perfectly oriented south, or that systems have technical<br />
flaws. In parts of Germany with a better solar regime, up<br />
to 1300 kWh can be produced in a year. In the south of<br />
Europe, the yields are higher up to 2000 kWh. The same<br />
is true in most of the United States. PV systems employing<br />
solar tracking may yield some 15% to 30% more than<br />
the corresponding fixed-plate arrays; on the other hand,<br />
installation and operation costs are higher: a difficult tradeoff.<br />
• Energy Payback Time for Solar Cells<br />
Crystalline silicon cells have a payback time of less than<br />
2 years, i.e. they are operated for less than 2 years at an