The 2 Types of Solar Hot Water
There are 2 main types of solar hot water that you need to choose between when you you want to heat your water with the sun:
- Solar Hot Water Panel Based Systems
- Heat Pump Systems
Solar Hot Water Panel Based Systems
The first type - solar panel based systems - use a flat solar collector that is placed on your roof which absorbs the sun's rays and transfers the heat from those sunrays directly to your household water which is pumped through those panels.
The water heats up as the sun hits it. When the sun isn't shining, you obviously can't heat the water with solar energy, so you need to have a backup fuel source, usually gas or electricity. Of course to avoid using this electricity or gas you store the hot water in a well insulated tank.
Generally these systems can provide from half to all of your home's hot water depending on where you live and how efficient your solar hot water panels are. In Hobart, you'll het about 50% of your water heated by the sun. In Darwin, you may get 100%.
Here's a typical panel based system. This one has its hot water tank integrated with the panels.:
Heat Pump Systems
A lot of people believe that the second type of solar hot water system - the heat pump - isn't really a proper 'solar' powered system. These people are wrong! People believe this because a heat pump system has no solar panels. However heat pump systems have don't need any solar panels because they use a different type of solar energy. Where 'conventional' solar hot water systems need sunlight to heat the water, heat pumps pull solar heat out of the air around us and use this heat to increase your water temperature. Although it sounds unlikely there is actually enough heat in the surrounding air - even on a winter's day - to heat your water right up to boiling!
Heat pump systems do use electricity to remove the heat from the air and transfer it to your water (they are basically air conditioners in "heat-mode"), but generally they use 75% less electricity heating your water in this way - compared to a conventional electric water heater - which is no more sophisticated than your kettle!
Here is a typical heat pump system - you can see the similarities to an air conditioner!
And if aesthetics are important to you, don't worry, you can get really sexy looking ones (to an engineer like me anyway!) with the heat pump integrated into the cylinder so it is almost invisible.