Harnessing direct solar energy – a progress report
Activity 1
Photovoltaic cells and solar collectors
Explain the difference between the two solar technologies that currently produce electricity: photovoltaic cells and solar collectors.
Teachers notes
Photovoltaic cells convert light directly into electricity. Most photovoltaic cells are based on silicon. When light strikes the junction in a thin slice of silicon, it causes a movement of electrons. Photovoltaic cells have no moving parts to wear out and produce no polluting waste products.
Solar collectors focus sunlight from a large area on to a central vessel in which water is heated to become very high temperature steam. The expanding steam can power a turbine and generate electricity. This can be done on a large enough scale that it can be sent across a power grid. Alternatively the heat may be used to drive a chemical reaction resulting in a transportable substance that can release its energy later – possibly to be turned into electricity.
Posted February 1997.