421 Efficiency of Solar Cells

As indicated above, PV cells behave in this fashion:

1. Power output increases linearly with solar flux.

2. Power output increases linearly with decreasing cell temperature.

3. Power output increases linearly with cell size (follows from 1 above).

Output voltage, volts

FIGURE 4.10

Example current-voltage characteristics of a silicon cell showing the effects of solar irradiance level and load resistance.

Output voltage, volts

FIGURE 4.10

Example current-voltage characteristics of a silicon cell showing the effects of solar irradiance level and load resistance.

It is easy to show that efficiency of a PV cell or array is given by an equation of this type:

The reference efficiency is given by the manufacturer and is usually 12 to 18%. The temperature coefficient of efficiency f is 0.004 C1. If one knows the average solar radiation, I, the average cell, panel, or array output (in units of watts) can be found from e = n a I

The same approach can be used to find instantaneous output if the instantaneous solar radiation and cell temperature are used in the two expressions above.

Solar Stirling Engine Basics Explained

Solar Stirling Engine Basics Explained

The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.

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