Editor –

Mike Roussos’ article, ‘Could the cost of SA’s solar geyser push outweigh the benefits?’, published on page 63 of the April 30–May 6, 2010, edition of Engineering News, calls for a reply.

The subsidy for solar water heating serves not only to save on average daily electricity consumptions, but is also part of a much broader policy that includes inducing the public to adopt a long-overdue new lifestyle.

As part of a quid pro quo to justify its 
unavoidable continuation of conventional (partly World Bank-funded) fossil-fuel power plant construction, government has committed itself to other steps which will limit or reduce South Africa’s future carbon footprint. 
This is an international obligation. 
The solar water heating subsidies are to be seen in this light – as are plans to proceed with solar power generation stations.

A major further consideration is, undoubtedly, that of job creation, where solar water heating will outperform sophisticated power generation by far. 
It has been estimated that, for every 500 solar water heating systems installed, one job will be created permanently for installing and, thereafter, maintaining these systems.

Moreover, it is part of government’s policy (see the editorial and lead article in the May 7–13, 2010, edition of Engineering News) that local manufacture is to be the engine driving the solar water heater project in the future. 
For this to succeed, some impediments and bottlenecks will have to be removed.

Obviously, it is hoped that these policy considerations will not be so misused that they result in poor quality and short life expectancies which, as Roussos correctly laments, are true of some locally manufactured conventional geysers.

Local manufacture (in which this writer is about to participate), over and above mere installation, can make a major contribution to the South African economy, including additional job creation and skills development, and there is also potential to export.

It is true that some conventional, locally produced hot water geysers, despite bearing the South African Bureau of Standards mark, have very poor life expectancies and heat storage qualities, and are only slightly improved, if at all, by unsightly geyser blankets. 
There is no justification for this. 
These products can, and should, be manufactured to much superior standards in both respects.
 I still have three conventional geysers in my house, two of which  have survived for well over 30 years.

It is also true that some cheap imported solar water heating products or some poorly installed solar water heating systems may have poor life expectancies overall. 
But it is equally true that the better-quality products, even if guaranteed for only ten years, if correctly installed, used and maintained, can realistically be expected to last at least twice that long.

With regard to the actual power savings in financial terms, it is not only the total daily consumption that counts, but also when that consumption takes place in relation to the grid’s peak demand times. 
This can, and should be, controlled by available control devices. Likewise, the frequent on- and off-switching, whenever even small bits of hot water are drawn, can be avoided by increasing the temperature interval set by the thermostat between the water temperatures at which switching on and switching off occurs.

Roussos would probably agree that the National Energy Regulator of South Africa-recommended feed-in tariff for concentrating solar power stations of about R6/kWh could also not be justified if the calculations made in his article were to be the sole criterion. 
I have no quarrel with that feed-in tariff for as long as it serves the common purpose of producing a workable and all-embracing mix of renewable-energy technologies capable of at least becoming economically justifiable within a reasonable time.



Dr Hans Hahn (PrSciNat)

hans@hahn.co.za