In the UK, the majority of solar
thermal systems are used to preheat DHW (Domestic Hot Water).
During the summer the water can be heated to very high temperatures
and little or no additional heat input is required. However,
in winter, the relatively low levels of solar energy mean that
additional heat input is required from the primary heating system
such as gas central heating boiler or electric immersion heater. By installing larger areas of solar
panels, it is possible to produce enough heat to contribute to the
space heating demands as well in new homes. Solar thermal panels, normally
cheaper, un-insulated types, are also used to heat swimming pools
during the summer.
In all cases, it is essential to provide frost protection during the
winter and overheat protection to prevent boiling during the summer. The
potential for damage to the home, the occupants and the products
themselves resulting from the very high temperatures sometimes
experienced by these systems illustrate why it is essential to use
only qualified designers, installers and quality products.
As a significant proportion of the
total cost is attributable to the installation, (labour, new hot
water cylinder, controls etc.), it is not usually cost effective to
install solar thermal in existing homes at current energy prices;
this may change as systems become cheaper, installations more
competitive and energy prices rise. The payback is obviously
quicker for homes where the primary fuel is expensive, as in the
case of electric, LPG or oil heating.
An ever increasing proportion of the
heat in homes is being consumed by DHW; this is particularly true
for newer homes where the insulation standards are better and thus
less heat is required for space heating. This, combined with
the relatively lower marginal capital cost for new-build, implies a
favourable market in this sector, particularly if novel, integrated
systems are considered. Solar thermal technology may also be
considered economically viable where the alternative means of
compliance with regulations (e.g. Code for Sustainable Homes, Merton
Rule) is prohibitive, and where it would therefore not be possible
to otherwise develop a new-build housing scheme.