African energy
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Solar radiation, temperature variations, and seasonal differences
The performance of solar water heaters is determined by type and where it is operating. The levels of solar radiation across South Africa vary considerably, as does the ambient and cold water temperatures.
By
James Green
The SABS tests solar water heaters at an average of 20MJ / m 2 per day, being an average for the country. Areas such as Upington are as high as 23.5MJ / m 2 per day and coastal areas typically lower at 18.5MJ / m 2 per day, as a result of higher humidity, clouds, and coastal fog. Johannesburg and Pretoria are very close to 20.5MJ / m 2 per day.
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