Power Electronics

Power Electronics in Alternative Energy

 

Wind, water, and sunlight are the keys to a new generation of power sources. Fuel cells and microturbines offer efficiency ways to convert fuels to electricity. The raw power from these sources must be conditioned before it can be used by standard electrical loads. This power conditioning function is where power electronics plays an important role.

 

Solar power is generally used to convert the sun's energy into either of two more readily useable forms: hot liquid such as in a solar water heating plant or solar thermal power plant, or directly into electric current such as generated by photovoltaic cells. Hot liquid systems can be used to generate steam to drive turbines and generators. The largest demonstration systems even include thermal energy storage so power can be produced continuously. Photovoltaic systems can use static power inverters to convert their initial low-voltage dc power into ac power suitable to run a given load or to feed into the power grid.

 

The electrical current available from photovoltaic systems is supplied at very low voltages that depend on a number of factors including the angle of the sunlight and level of cloud cover. This variation of output voltage and output power means that we need some way of regulating controlling the output of the photovoltaic system; this task is often accomplished using adjustable boost converters that can keep the output voltage of a solar cell bank constant regardless of sun angle. Once a constant voltage is available, an inverter converts the solar power to ac so it can be fed into the power grid.

 

Photovoltaic current is now more than ever becoming a growing source of power. Thanks to recent developments in thin film photovoltaics, the cost per kilowatthour is not far above a target level of US $0.10/kWhr.

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