Ourpower Guides - Solar Thermal - FAQ

How does a solar thermal system work?

• A solar thermal system consists of a number of components; a solar collector, a pump station, a solar controller and an indirect hot water storage tank.

• The solar collector, located on the roof, collects the sun'€™s energy and transfers the heat to the storage tank via the tanks internal heat exchanger. The storage tank allows the hot water to be stored until it is used at night or in the morning.

• The storage tank acts as a pre-heat tank for the existing hot water tank. As hot water is being drawn from the existing tank, hot water from the pre-heat tank replaces it.

What is the life expectancy of a solar thermal system?
The life expectancy of a solar system is between 20 and 30 years. If a solar system receives regular annual maintenance checks, they can last over 30 years. Although very little maintenance is required, it is recommended that a service contract be made with your qualified solar installer.

Can a solar water heating system be used in place of a traditional gas or electric hot water system?
In order to ensure proper efficiency of your water heating system, a solar energy system must be used in conjunction with a traditional gas or electric hot water system rather than as an alternative.

Do solar systems produce hot water in the winter?
Yes, but the amount produced will be less than in sunny summer months. Similarly, on cloudy days, solar thermal systems will still produce hot water, but less than when sunny, with about 20 - 30% of solar energy penetrating clouds.

Can I use a solar collector with my existing hot water system?
Yes, but typically a 2nd hot water tank, or a larger replacement tank will be sensible. In most cases a 2nd heating coil is required in the tank.

How much hot water will Solar Thermal supply?
Solar Thermal systems are capable of producing 100% of your hot water requirements on an annual basis. A lower-cost and ideally-sized Solar Thermal system would supply 100% of your hot water during the summer months and a significant proportion during the winter.

How safe is the Solar Thermal system?
It is totally safe.

• The collectors continue to operate efficiently at temperatures far below freezing.

• The only material in contact with the water is copper which is non-toxic.

• Solar Thermal collectors have been proven to withstand hailstorms as well as high winds.

What can a Solar Thermal system be used for?
Solar Thermal systems have been chosen for a wide variety of domestic and commercial applications. These installations range from domestic hot water systems, space heating, pools, spas, and hot tubs to commercial solar heating and air conditioning systems in airport terminals, hospitals, and hotels.

Could a Solar Thermal system heat my house?
Yes it could, although solar thermal is more suited to the production of hot water, particularly in the UK. There are a number of important factors to consider:

• In the UK, typically solar thermal energy is reduced in winter months, just when heating is needed.
• How the house is heated - radiant underfloor heating systems are best, as they operate at low temperatures.
• A full backup system should always be provided.
• To provide enough heating in the winter, the installation may need to be quite large. Therefore, situations where there is a significant summer requirement for hot water are preferred. Examples would be for use with a swimming pool or a hot tub.

What about maintenance?
No collector maintenance is required. The glass tubes are round and perfectly smooth; any dirt or dust is carried away by the wind and rain. There are no moving parts to wear out. All components are made from high grade stainless steel, copper or non-corrosive materials.

Is the Solar Thermal Collector a proven product?
There are over two million tubes in every-day use in over thirty thousand locations worldwide. There are hundreds of installations in North America from the Canadian north to the southern deserts.

Which type of panels/collectors are best, flat panel or evacuated tube?
There is no definitive answer to such a question. Typically, evacuated tube are easier to install (as they are modular and not in 1 piece); better insulated and so lose less heat back to the environment; better at absorbing solar radiation at different angles to the sun (i.e. throughout the day, or if roof faces away from South); easier to clean and less maintenance
Flat plate collectors are typically cheaper, and some may perform better in cloudy conditions.

What is a Closed System?
A Closed System is one where the liquid warmed in the collector is used to warm the hot water tank via a heat exchanger or coil in the tank. An Open System directly heats the hot water, and are more common in warmer climates where freezing conditions are not common.