Solar Thermal Heat Utilisation - Renewable Energy: Technology, Economics and Environment - page 158

solar cover of the domestic hot water demand (i.e. systems without long-term heat
storage) collector areas of about 0.9 to 1.2 m 2 per person and a storage volume of
40 to 60 l per square metre of collector area can be expected. In the case of sys-
tems with long-term heat storage, the store should have a volume of 2 to 3 m 3 per
square metre of collector area. The collector area itself would have to be between
0.4 and 0.7 m 2 per GJ annual demand for heat supply. Systems designed for par-
tial solar coverage of space heating and domestic hot water supply can achieve
useful heat gains at the exit of the solar system (i.e. at the outlet of the storage) of
around 900 to 1,370 MJ/(m 2 a) or 250 to 380 kWh/(m 2 a) /4-15/. If the solar dis-
trict heating system is only used to support solar domestic hot water supply, the
specific yields are higher since the storage losses are lower in that case (see
/4-15/, /4-16/, /4-17/).
Further applications. At the given radiation and temperature levels in Central
and Northern Europe, solar thermal heat use is efficient if heat is required at a
comparatively low temperature level, and the demand for heat and the availability
of solar radiation, either occur simultaneously or at least do not occur at totally
different times. In addition to the domestic hot water supply of private house-
holds, this is mainly the case in many public facilities. One example is the provi-
sion of water for showering in public sports facilities, particularly if the facilities
are mainly or exclusively run during the summer (e.g. open air tennis courts).
Other examples where a high demand for heat may also occur during the summer
include camping sites, small hotels, hospitals and old people's homes as well as
nursing homes /4-19/, /4-20/. In addition, there are other applications of solar
energy.
− Flat-plate collectors can be integrated into existing networks for district heating
at comparatively low cost. The collectors directly feed into the return-flow of a
district heating network and can thus cover part of the demand for heat, espe-
cially during the summer /4-15/, /4-17/.
− By using highly efficient flat-plate collectors or vacuum pipe collectors, heat at
temperatures of more than 90 °C (typically between 90 and 120 °C) can be
supplied for industrial use or for BTS (Businesses, Trade and Service Sector,
others; mainly small consumers) even under the given radiation conditions in
Central and Northern Europe, without having to apply radiation concentration.
− For many industrial uses hot water at temperatures of up to 60 °C (e.g. photo
laboratories, washing of parts) is required. These temperatures can be gener-
ated with solar energy.
− Hay and grain harvested during the summer can be dried using solar power. Air
collectors can be used for this purpose.
− For larger buildings with a requirement for year-round heating and cooling,
solar collectors can be used for heating during the summer, at night and during
the winter for cooling purposes.
− Solar collectors can also be used to cool rooms via sorption-supported air con-
ditioning processes in the summer.