What is Green Heat?

Renewable Heat Technologies

Green heat is renewable heat or the generation of heat from renewable sources.

Biomass

Burning organic matter or biomass in boilers and stoves generates heat that can be used directly or to produce hot water or steam. The most common fuel used is wood.

Solar

Uses the sun to heat water or air in buildings, there are two types, active and passive.  Passive heating relies on architectural design; the building's siting, orientation, layout, materials, and construction are utilized to maximize the heating effect of sunlight falling on it.

Active solar systems use the energy from sunlight to heat a panel called a collector; there are two types of panel - evacuated tube and flat plate collectors. The heat warms a working liquid which can then be used either directly as hot water or can go through an exchanger and transfer the heat from a working liquid to the water.

Solar systems usually have a hot water tank, this stores the heat so that it can be used at any time. The amount of heat a system can provide is dependent on the surface area of the collector.

Ground source heat pumps

Half of the energy from the sun that hits the earth every day is absorbed by the ground. The result is that the ground remains at a constant temperature of between 10 and 15 Degrees C all year round at a depth of 1-2m below the surface.
A geothermal system consists of a geothermal unit, which is connected to a Ground Loop that is buried in the earth, usually to a depth of 1-2m. Water circulating through the loop pipe absorbs the heat from the ground and takes it back into the house.

The geothermal unit transfers the heat to air that is drawn through the unit and blows the warm air around the house using standard air ducts. Alternatively, the heat is distributed through pipes containing water for under-floor heating. Where space is at a premium ground source heat pumps can be installed in vertically bored holes, these can be 15 to 100m deep depending on energy need.

Air source heat pumps

These are electrically driven heat exchanger systems that warm cold air inside a building as it passes through an exchanger which extracts heat from the air outside. They are normally coupled with heating systems that require relatively low operating temperatures such as under-floor heating, but there are some systems that can integrate with conventional radiator systems, and some that produce warm air that is circulated through the building by fans.

Water source heat pumps

Water source heat pumps work in a similar way to ground source heat pumps with the exception that pipes are submerged in a river, stream or lake, where temperatures remain at a relatively constant level of between 7 and 12 degrees. The liquid in the pipes absorbs the heat. This heat is passed to a heat pump located inside the house.