Heat from the sun can be captured using flat or tubular solar thermal collector panels. These contain a glycol/water mix which becomes hot under glass in a similar way to a greenhouse. The glycol stops the liquid from freezing in winter and the system is held under pressure, dampened by an expansion vessel, to minimise boiling and pump cavitation when high temperatures are reached in the summer.

The heated liquid is generally pumped from the panels through a heat exchanger coil within a hot water cylinder where it transfers the heat to the domestic hot water. This type of system can also be used to very good effect to heat swimming pools.

To maximise the storage of the thermal energy captured a slightly larger hot water cylinder than normal is used and the stored water is brought up to a higher temperature than is usual, making it necessary to regulate the temperature of the domestic hot water supply with a thermostatic valve.

A controller automatically starts and stops the system based on the comparative temperatures of the panels and the water in the cylinder, and the system should provide much of the hot water for a domestic household from April through until October and up to about 10% of the needs during the UK winter.

Not all household would benefit from this type of system but if designed and configured correctly in conjunction with the existing central heating system solar thermal collectors can work exceedingly well in the UK.