An altenative to a gas geyser is a solar geyser, especially in areas where sunshine is in abundance. Alternatively you can use a solar geyser as an energy saving device.
High pressure?
You will need high pressure under the following conditions:
- Your water source does not deliver enough pressure to fill the geyser that is located on your roof. This is usually not a problem in cities or towns, but could be a problem in the coutryside.
- The warmwater delivery to the taps are poor and it takes forever to prepare for a bath.
- If you like to shower with strong waterpressure the solution is a high pressure system.
- You stay in an area where the waterpipes freeze in winter.
Pressure pump size and installation?
For a high pressure system in the countryside you normally would need to install a pressure pump. You could install the pump at the main inlet. This would mean that any water used in the house will cause the pump to start up to maintain a constant pressure.
If your cold water pressure is sufficient, you could also install the pressure pump on the hot water inlet only. This method would save you a bit of energy as well. Why would you want the pump to start up if you flush the toilet?
A variance could be to have high pressure cold water at your shower outlets as well. This will ensure you have similar pressure at both the hot and cold water outlets. Hence temperature regulation would be good.
The solar tubes in blue below conducts the heat to a tip that is located inside the geyser tank. This almost works like a soldering iron tip. There is thus no water in the blue tubes and therefore the tubes are unlikely to burst in freezing temperatures.
You do not need a massive pressure pump and probably do not want it either, as you could end up causing leaks or bursts in pipes if the pressure is too much. I would suggest a volume pump rather that a pressure pump.
A .37kW pump would be sufficient for a normal household (example images are attached below). It should also not cause leakages, even in old farmhouses.
Low pressure?
Everything in such a setup would be gravity fed. Low pressure geysers are usually a bit cheaper than high pressure geysers. The tubes in blue below will usually be filled with water, unlike a high pressure geyser. Again, if you stay in an area that is prone to freezing temperatures in winter, the possibility of a tube bursting is a reality.
Considerations?
The drawback will be that the hot water temperature will be at its lowest at sunrise. You can usually expect hot water from around 10am onwards, depending on the season, outdoor temperature etc.
You will have to install the geyser in a north-facing direction, normally on your roof.
Using an element?
Be sure to use a solar geyser that allows for an element to be installed. You can then always warm up the water that way if need be. Be sure to install an element that has a pocket to accept a thermostat. That way the power will automatically be cut once the set temperature is reached.
If you use solar power for your house it is adviseable to install a smaller kW element rather than a bigger rated element. A 100lt geyser with a 2kW element will be a good match and should get the water to the correct temperature in about an hour.
Size of solar geyser?
This mainly depends on the number of people in the household. The rule of thumb is 50lt of water per day per person minimum. Thus for 2 people a 100lt geyser will be sufficient, but a 150lt would probably be better.
Having said that, if you primarily work with solar power, the smaller the geyser, the quicker the water will be hot. So there is always a tradeoff to be made.
Each of the blue tubes are usually an indication of the seize of the solar geyser. From the below image one can see there are 15 tubes. So in all likelyhood we are looking at a 150lt solar geyser here.
Deur: Johan Swart