Solar PV could theoretically supplement grid-power during daylight hours to reduce generating costs and environmental emissions. However, at this scale serious disadvantages emerge:

• The daily intensity of the sunlight varies dramatically because of cloud cover.

• Solar power is greater in the summer whilst the demand for electricity is lower.

• Should future solar PV power rise above 20% of the total electricity supply, then existing grid systems built to be dominated by coal, oil and nuclear generation would have to be modified

Despite these caveats, the potential of solar PV is enormous. If photovoltaic conversion with 10% efficiency was installed over an area of 500,000km2 (about 1.3% of the area of tropical deserts) humanity’s present energy requirements would be met. That outlook is probably far off. Of the electricity generated from all alternative energy sources in the early 21^st century, solar PV contributes only about 0.0.2%, with solar thermal generation a little more significant at 0.06%.

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