Expected water temperature from solar geysers

Because of the fact that "solar insolation" levels, (energy from the sun), across the country are highly variable it requires that products be both correctly sized and oriented for their installed location if they are to be able to provide a useful year round energy source.

To highlight this phenomenon, Sky Power has launched a graphical utility, which attempts to predict water temperature achievable from a solar water heating systems.

By entering the size of the geyser the Q factor of the solar collector product and the location of the installation the tool create a graph showing expected water temperature for each month of the year.

The utility can be downloaded from: http://www.skypower.co.za/content/calculators/power_demand.asp

Whilst it is a very simple computer modelling tool, it presents graphically the expected water temperature achievable from installing SWH systems at different locations across the country.
Expected water temperature is plotted with consideration to the size of the geyser and the power delivery capability of the product, as measured by the SABS (Q Factor). It is further adjusted to reflect the effect of solar energy levels at the installation site, in conjunction with the elevation of the collector and the effect of both cold water temperature and thermal losses throughout the year.

In South Africa collector elevation is very important as its effects the energy available to the system and varies dramatically between the higher and lower latitudes.

Above all this utility helps to highlight three issues:
Firstly that a "one a size fits all" design is not suitable for South Africa. It demonstrates that solar collectors need to be sized according to the location at which they will be installed and matched to the volume of water they are associated with.
Secondly, that to be effective in replacing electrical energy for the purposes of water heating, the system is required to be sufficiently powerful to work in winter whilst having the necessary control mechanisms to prevent overheating.
Thirdly, that certain products currently being marketed will produce very little temperature rise in winter conditions even if optimised through correct elevation.

Modular system designs such as active split systems offer greater flexibility and more importantly control in achieving useful energy delivery.

Possibilities further exist to upgrade such systems to include pool heating for example. On large scale projects other techniques provide the means to dump energy when required by the use of thermal dissipaters which harmlessly redistribute any excess energy back to the atmosphere.

Surprisingly such powerful systems with suitable control mechanisms to eliminate potential overheating problems are often no more expensive than many of the older passive systems.