Environmental Engineering Reference
In-Depth Information
452
for geothermal systems) because of their lower costs due to little space consump-
tion and short installation periods compared to systems installed in ducts.
Individual connection of each
customer to the grid
Connection with the grid from
house to house
Hybrid connection (combination
of both options)
Distribution line
Main distribution line
Consumer line
Fig. 10.7
Transmission routings (see /10-2/)
Because of the moisture within the soil, corrosion resistance is the major re-
quirement to be met by the distribution system. Also, moistening of the insulation
needs to be prevented with regard to limiting heat losses. Primarily, plastic jacket
pipes equipped with steel medium pipes are applied. Alternatively, plastic medium
pipes can be used. For sub-lines and house connections flexible metal or plastic
medium tubes are suitable, which are laid "from the coil". These kinds of tubes
are laid faster and reduce the risk to damages.
Last but not least house substations are required to link the district heating sys-
tem to the existing heating system within the house. Such substations are available
in a standardised design and are supplied with all accessories required for the
connection of the building to the district heating system. Direct and indirect sub-
stations are distinguished.
−
In direct substations heating water from the district heating system flows
through all components of the heat distribution system installed within the re-
spective house. The temperature is controlled by simply adding cooler water. In
most cases direct systems are more cost-effective compared to indirect systems
/10-2/.
−
Indirect systems are characterised by a heat exchanger located between the
district heating system and the heat distribution system installed within the re-
spective house. The main benefits of such an indirect system result from the in-
dependence of the house heat distribution system from the pressure conditions
and water properties of the district heating system.
Overall system layout.
Due to the high investment costs for tapping geothermal
energy resources, in general, geothermal heating stations have necessarily to be
connected to large district heating systems. For this reason, it is advisable to first
check all opportunities of establishing or extending a district heating system at the
planned site before considering geothermal heat supply. Supply systems of a ther-
mal capacity of 5 MW constitute in most cases a lower limit for the supply of
mainly household customers. This might not be true if there is a really favourable
annual load duration curve of the given heat demand with a high volume of full
load hours (e.g. low-temperature heat demand by a big company running on three-
Search WWH ::
Custom Search