The solar thermal identity… or should that be supremacy?

Solar thermal (also called solar heating collector) is a mature renewable energy technology. Solar collectors have recently been used not only for the preparation of hot water and pool water, but also for heating objects and devices. It can provide hot water at temperatures of between 55 and 65º C.

An efficient solar thermal system has the potential to meet nearly two-thirds of the hot water needs of a building. It works by absorbing energy from the sun and transferring it to heat water.

There are three main types of solar water heating systems:

• Flat-plate collectors: These are encased in a sheet of metal that absorbs the sun's energy and conducts heat to the water.
• Evacuated tubes: This is a coated or plated inner tube (absorber) contained in an outer tube (glass layer) which uses the sun’s energy to heat the water in an exchanger.
• Solar matting: Water is heated as it passes through hollow tubes made of flexible black material which can absorb sun rays.

Tip

The solar collector should ideally be mounted on the roof, facing between south-east and south-west. For small offices or houses, a system should occupy around 4 m2. Solar thermal systems are more easily integrated into new buildings than retrofitted to existing ones (more costly option). Nonetheless, they can be integrated into an existing gas-boiler system.

Solar thermal systems are economical where the demand for hot water is high. Savings are routinely higher with larger systems. Check with local authorities if planning permission is required (it might depend on the scale of the project).