Solar Thermal Heat Utilisation - Renewable Energy: Technology, Economics and Environment - page 159

4.3 Economic and environmental analysis
In the following, a selected number of solar thermal systems with technical pa-
rameters that reflect the current market spectrum are analysed under the aspects of
cost and selected environmental effects.
4.3.1 Economic analysis
The following five case studies will be looked at, considering the climate of
Würzburg (Germany) that could be used to cover the supply requirements out-
lined in Chapter 1. Their system parameters are shown in Table 4.6.
− Solar thermal system to support domestic water heating (SFH-I) with a collec-
tor area of 25 m 2 . It is a solar combined system for a house with a heat load of
5 kW (at an ambient temperature of -12 °C). Approximately 62 % of the aver-
age demand for domestic hot water of 200 l/d with a temperature of 45 °C is
met by solar energy. This is approximately the demand of a household with
four people. The solar fractional saving is around 44 %.
− The same system (i.e. a solar combined system), but for SFH-II with a heat
load of 8 kW. The solar fractional saving is around 31 %.
− Solar thermal system to support only domestic hot water heating in a household
(SFH-III) with a collector area of 7.4 m 2 . The demand for domestic hot water is
the same as in the first example.
− Central solar thermal system with heating support and domestic water heating
in multi-family houses (MFH) with a collector area of 60 m 2 and a two-pipe
network directly integrated into the heating system. Of the entire energy de-
mand for 10 flats (approximately 500 GJ/a) around 10.4 % are covered by solar
energy. The solar system is combined with a conventional boiler that meets the
remaining demand for domestic hot water and space heating in a heating centre
for all connected households.
− Solar thermal supported district heating system to meet the demand for space
heating and domestic hot water with a short-term storage (DH-I). The solar-
supported district heating system supported by solar thermal energy has a
boiler capacity of 1 MW and a demand for heat of 9.9 TJ/a on the heat sup-
plier's side. The network is designed with flow and return-flow temperatures of
95/60 °C at -12 °C. The solar fractional saving is 6.2 %. It is a two-pipe net-
work with domestic water heating directly with the consumer.
All collectors apart from the ones in the example SFH-III (decentralised domestic
water heating) where copper absorbers with a high-grade steel tray are used, are
selective flat-plate collectors (copper absorbers) with a mineral insulation layer
and a wooden frame that are installed inside the roof. The solar district heating
system (DH-I) additionally uses collector modules with particularly large areas.
The steel tanks to store the heat supplied with solar energy for decentralized
domestic water heating (SFH-III) and in solar combined systems (SFH-I and