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

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1 Basic physical principles of photovoltaics

Solar photovoltaic (PV) cells directly harness an energy source that is by far the most abundant of those available on the planet: as you have seen, the net solar power input to the Earth is more than 6 500 times humanity’s current rate of use of fossil and nuclear fuels.

Figure 1 The International Space Station is powered by large arrays of solar photovoltaic panels with a combined output of around 130 kW

The PV cell in its most common form is made almost entirely from silicon, the second most abundant element in the Earth’s crust. It has no moving parts and can therefore in principle (if not yet in practice) operate for an indefinite period without wearing out. And its output is electricity, probably the most useful of all energy forms.

Photovoltaic cells consist, in essence, of a junction between thin layers of two different types of semiconductor, known as p-type (positive) and n-type (negative), which we’ll look at next.

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