Solar water heaters: 5 general misconceptions
When not confused with photovoltaics, a solar hot water system or heaters suffers from a few preconceived ideas that can lead to a lot of confusion. First of all, let’s remember that a solar water heating system produces hot water, and not electricity.
A solar HWS can cover 100% of your hot water needs
FALSE: A solar water heater helps to reduce your electricity consumption for domestic or commercial hot water, but it requires a significant amount of additional power to meet all your needs. It can provide about 50% of what you need, but the rest comes from an electrical system within the water tank.
There is a solution to further reduce your electricity consumption: coupling a thermodynamic water heater or heat pump unit with a solar water heater. This can reduce your electricity needs by up to 90%.
A solar water heater is not as easily adaptable as the solar energy system
FALSE: A solar energy system is less restrictive in that it does not need to supply a boiler but only a hot water tank. Thus, it requires less surface area for solar collectors. In addition, the installation is less complex and fits perfectly into a small space.
The slope of the roof does not affect the performance of a solar water heating system
FALSE: The slope of the roof is very important to maximise the efficiency of the solar radiation received. The idea is that a maximum of light rays should be received at an angle of 90° to the collector surface.
The optimum value depends on the location and also on the date, as the sun does not travel the same path across the sky in summer and winter. The question is therefore whether you want to favour one season for your solar hot water production over another.
A good compromise is to take a value equal to the latitude of the location + the inclination of the sun according to the time of the year. The final result is between 25 and 70°. For Perth, 30° is often recommended and facing north.
A solar water heater pollutes
FALSE: The internal part (water heater) must be separated from the external part (solar panels). The inside is just as recyclable as a conventional water heater. The panels consist of vacuum glass tubes or a black heat absorber covering a window.
It is not particularly polluting. The only polluting element is the heat transfer fluid that transmits the heat to the heater. It can emit powerful greenhouse gas but the doses are minimal. As long as there are no leaks and the fluids are taken care of by a professional at the end of the installation’s life, there is no particular environmental risk.
Solar Water Heating is only profitable in hot area or countries
FALSE: As soon as solar energy is mentioned, “northern countries” would not be entitled to benefit from it? Wrong!
Even if it is true that the yield will be lower in areas where the sun does not shine as often, it remains profitable in most cases. Solar thermal collectors work with very low heat radiation and the extreme operating temperatures are in the range of -40°C to +70°C. The only thing that will change is the optimal inclination as seen above.
Find more on solar panels with this PDF guide from the department of commerce!
