Can solar for low income homes make sense?

James Green, SESSA Solar Water Heating Chair

The NSWHP rollout of solar water heaters, from 2010 to 2012 was beset with problems. Now 5 years later the President’s target of 1m SWH as announced in April 2010, has not only been missed by some 60% but the industry that was spawned has long since disappeared along with the lost investment in local manufacturing and in jobs and training of installers.

Rooftop PV

However yesterday September 10th 2015, President Zuma when providing an update to journalists on the Presidential Infrastructure Coordinating Commission (PICC), referred to specific areas of focus including the revitalizing of the roll out of solar water heaters with a target of 1,4m to be installed within the next 4 years. 

If it is ever really to be reintroduced, (ignoring government funding issues, R4,7b was allocated back in 2011 but its reality is a mystery), it can only make sense if the SWH’s chosen actually produce hot solar water, which was not the case with many of the 306,000 systems installed during 2011 and 2012.  

In the same way as being asked to buy a car without wheels, (pointless) an investment in a solar water heater needs to actually produce hot water, not just be an ugly decoration. Not enough power output – don’t install it.

To determine what minimum performance is necessary, the specific heat of water formula is used to determine the kWh needed to heat 100 litres from 11 °C (the cold water temperature in winter) to 40°C, the typical temperature for potable washing. The minimum SWH output needs to be 3,37 kWh (100l  × temperature differential of 29 °C ÷860 =3,37 kWh). Turning this into the SANS ‘Q’ factor results in a ‘Q’ figure 12,14 at 20MJ m2 p/d (3,37kWh ×3,6 (formula for kWh to ‘Q’) = ‘Q’ of 12,14). 

In reality this performance is woefully short, as at 25 litres per person per day and typically 5-6 persons in an RDP home, one needs at least 125 litres and preferably 150 litres of potable water at 40°C.  The solar output needs to be respectively 4,21kWh and 5,05kWh, which are ‘Q’ factor figures of 15,15 and 18,20 at 20MJ m2 p/d respectively.

The argument in favour of installing a SWH with the required minimum necessary performance is self evident, in that if it can only be used for 6 to 9 months of the year when cold water is warmer (therefore less performance is necessary), it fails in its purpose to provide hot water for washing at the time when hot water is needed most, and electricity will still be used during peak periods through kettles and hot plates.  Eskom failed when the program was under its stewardship to understand this, or maybe they did, only too well. 

The benefits of a socio economic uplift program in installing solar water heaters into low income homes, not only can improve the living standards of those people, it will save them money spent on electricity they can ill afford. It will also benefit Eskom in reducing MW peak demand through kettles and hot plates, and with approx. 5m RDP homes this is as much as 2,500MW peak. 

In times when job creation is so important, ongoing jobs in installation of SWH will continue, which is being proven not to be the case arising from the huge investment into REIPPP’s, wind, CSP and PV, when the sites become operational.  

With falling prices of rooftop solar PV, installing small systems with battery back up into rural homes not connected to the grid, can make sense. For low income homes with Eskom or municipal power, energy efficient lighting with LEDs, not CFL’s as they have proved not to last as long as projected, will also benefit both the homeowner and the grid. Micro grids in rural communities will potentially be a better alternative to building powerlines.

If there is ever going to be a ‘next time’, before government wasting funds on solar water heating systems that will not deliver, choose products that do, providing the return on investment that is needed.