African energy
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Gas boilers enjoy the advantage of instant hot water , potentially saving on the heat loss of stored hot water , but the cost per litre of hot water is in theory very similar to an electrical resistance element , based on protection of Eskom ’ s prices and the minimum costs of gas as set by the Department of Energy and NERSA .
Heating oil boilers enjoy a cost advantage over gas , not because they are more efficient , but because paraffin does not suffer VAT and is subsidised by the government .
Solar photo voltaic ( PV ), where electricity is generated from solar panels , is not a suitable option for heating water using the existing electrical resistance elements in the geyser . Comparatively , the costs are up to five times higher than using solar water heating technology .
Based on South Africa ’ s high solar radiation , solar water heating should be the winner in terms of cost versus reward ( depending on the system chosen ).
However , a combination of hot water heating energy technologies may be the best solution , particularly on larger hot water requirements ( commercial applications like hotels and hospitals ). For example , solar is used to preheat and is then topped up by either gas , heating oil , or heat pumps . PA
James Green is the CEO of Ubersolar and Pay As You Go Solar , and a member of the SESSA Council .
‘ Solar water heaters are rubbish ’ – or are they ?
Untrue headlines , fictional news , and falsehoods . Conspiracy theories are reaching new heights across the world , particularly in the UK ( Brexit ), in the US ( Trump ), and , of course , in South Africa .
By
James Green
Having got your attention , there is , unfortunately , a certain amount of truth in the statement , “ Solar water heaters are rubbish ,” since many consumers and indeed plumbers think exactly that .
The problem is not that the heaters are rubbish ; rather , the problem is misinformation , lack of understanding , and unrealistic expectations . While the Department of Energy states , “ Water heating accounts for a third to half of the energy consumption in the average household ,” and Eskom says , “ An electrical element geyser will use up to 40 % of the average household ’ s energy costs ,” solar water heater suppliers have claimed savings of up to 40 – 60 % of the home ’ s monthly electricity bill .
Well maybe , but only if the solar water heater is sized correctly and the power output matches the kilowatthours being used to heat water . In more than 90 % of cases , this has not happened .
Studying the output of solar water heaters reveals that most solar systems are only about 70 % efficient in replacing the electricity normally used in heating the tank ’ s volume . Amazingly , power output in kilowatt-hours on solar thermal systems is almost never mentioned on information sheets and websites .
At the same time , ‘ savings calculators ’ for solar water heaters suggest anywhere between 35 % and 45 %
Continued on page 19 >> www . plumbingafrica . co . za March 2017 Volume 23 I Number 1