African energy
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In contrast, London or Berlin is about 50 % of South Africa’ s average solar radiation. Rome is similar to Durban.
The performance of solar water heaters, as tested by SANS 6211, also assumes perfect orientation( true north) and inclination being latitude + 10 %. Absolutely no shade from trees or obstruction is assumed.
In real life, further complications arise as a result of seasonal variations in weather patterns. For example, in the Highveld, the winters are generally clear and sunny, while in the Cape they suffer far more cloudy and rainy conditions. In summer, however, the levels of solar radiation in the Cape are far higher than what they are in winter and much higher than that of the Highveld.
The same solar water heater installed in Johannesburg and in Cape Town will have considerable day-to-day variances in performance.
At the same time, while the performance( kWh output) of a solar water heater in the Cape is likely to be lower than the performance of a solar water heater in Johannesburg in winter, the cold water temperature that is to be heated will be several degrees colder in Johannesburg than in the Cape. The same scenario exists for areas like Durban. So to a greater or lesser extent the performance variances are offset against each other.
When choosing a solar water heater for homes or for systems with commercial application, the deemed kWh output, as tested by SANS, is the starting point to determine the potential payback on capital and return on investment( along with the cost). As mentioned earlier, there will be distinct differences dependent on the variation in location and the actual installation( orientation, shade, and so on); the actual savings for each system can be empirical only with baselines created by monitoring and evaluation, both pre- and post-installation. PA
James Green is the CEO of Ubersolar and Pay As You Go Solar, and a member of the SESSA Council.
Deemed kWh output, as tested by SANS, is the starting point to determine the potential payback. www. plumbingafrica. co. za April 2017 Volume 23 I Number 2