How Solar Works

How Solar Hot Water Systems Work

A Solar Hot water system works by using the sun’s rays to heat the water stored in your Hot water Cylinder in the Hot Press.

The graphic on the right shows the set up of a solar Hot Water System.

The sun’s rays hit the solar panels which are normally mounted on the roof of your house.
A special controller measures the temperature of the solar transfer liquid in the panels and turns on a pump when this temperature rises above the temperature in the bottom of the cylinder.
When the pump is running the solar transfer liquid transfers the heat from the solar panels to the cylinder.
There is no mixing between the water that you get from the hot taps and the solar transfer liquid.
To prevent damage to the system, the solar transfer liquid contains an antifreeze to ensure the system is not affected by freezing weather in winter.

The image on the left shows the average level of solar radiation falling on a 1m2 surface per annum, measured in kWh (the same measure as a unit of electricity). On average Irish households use 3,000 kWh per annum on water heating, therefore it is obvious from the above graphic that a properly sized system will provide a large portion of the annual hot water requirements.

Winter Versus Summer

Many people assume that Solar Water Heaters are only effective in the summer months.
While it is true that in the summer months a Solar water system will often provide 100% of a households hot water requirements, it is not true to say that they do nothing in the winter.
Solar panels do not need direct sunlight to operate.

In winter the supply of water to the hot water cylinder is considerably colder than in summer, therefore a very small increase in the temperature in the solar panels will start to reduce the amount of energy required to generate hot water.
There is a finite amount of energy required.