Solar Hot Water - Solar Thermal

Solar panels are available in two main types – solar PV (for electricity), and solar thermal (for hot water). This section talks about Solar Thermal.

There are two different types of Solar Thermal collectors (panels) used for domestic hot water. Flat Plate and Evacuated Tube collectors. Flat plate collectors use the heat of the sun to generate hot water whereas Evacuated Tube collectors use sunlight to generate hot water. So, here in the UK Evacuated Tube collectors will operate effectively in colder conditions such as a bright winter’s day, whereas Flat Plate collectors will not be so effective. Unglazed plastic covered solar collectors are sometimes used to heat swimming pools which operate at lower water temperatures.

Both panels operate by using the sun’s energy to heat liquid contained within the panel or tubes. A controller monitors the temperature of the liquid in the panel and the temperature of the water in the hot water tank. Whenever the liquid in the panel is at a higher temperature than the water in the tank it is pumped through a heat exchanger which effectively increases the temperature of the water in the tank. A typical Solar Thermal system will be able to supply all your hot water needs in the summer months and as much as 50% of your needs at other times. Your conventional boiler or immersion heater will operate in the normal manner to heat water whenever the required temperature is not reached.

For domestic hot water you will typically need between 2 to 4 panels which will use approximately 3 to 4 sqm of roof space (swimming pools will need more space and can be ground or roof mounted). To make maximum use of the sun’s energy Solar Thermal systems need to be positioned in a southerly aspect (South West through to South East). You will sometimes need to replace your existing hot water tank or have space to install a cylinder next to your existing tank which will contain the heat exchanger (solar siphon). Some hot water systems are not compatible with Solar Thermal such as those using a combination boiler (Combi) or a system where no hot water tank is used.

Little or no ongoing maintenance is required. The panels need to be kept clean and generally rainwater does that very well. Just remember to keep any trees etc. that could cause shading cut well back.

To know how much energy your Solar Thermal system is generating you will have your own Naturalwatt webpage (your MicroGrid) that will display LIVE the amount of energy generated and amount of CO2 saved.

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