Environmental Engineering Reference
In-Depth Information
generally decrease with increasing plant size. Basically, the costs for the produc-
tion and injection well dominate the overall costs for a geothermal heating plant.
Besides the production and injection well, the main components of geothermal
heating stations are production and injection pumps, heat exchanger, filters, and
slop systems. If the geothermal fluid temperature is too low with regard to the
temperature level of the district heating network, heat pumps are additionally re-
quired.
With a share of approximately 51 respectively 30 % (DH-II respectively DH-
III) in both case studies, the two wells account for the major portion of the in-
vestment costs. Depending on the depth of the well, the drilling costs for the pro-
duction and the injection well vary widely; for average geological conditions they
might be in the order of magnitude of about 1,000 €/m.
Depending on pipe dimensions, site conditions (e.g. rocky or sandy ground) as
well as settlement structure the costs of the district heating network may vary
widely. However, an average price for a district heating network suitable for geo-
thermal heating stations is in the order of magnitude of 385 €/m. The investment
costs for house substations according to Table 10.2 include the costs for the con-
nection between the heating grid and the building as well as the expenses within
the building (e.g. domestic warm water storage).
The remaining expenses such as filter and slop system of the aboveground geo-
thermal fluid circuit as well as the planning of the heating plant influence the
overall investment costs only to a minor extent. This is also true for the heat ex-
changers as well as the construction costs (building including ground).
The indicated costs for heat supply from geothermal and, to cover peak loads,
fossil fuel energy include furthermore the costs for the peak load heating plant
(including boiler, burner, fuel storage or natural gas connection) as well as the
expenses for the CHP stations and the heat pumps (Table 10.2). However, with
regard to total costs they account only for a small portion of scarcely 4 and 11 %,
respectively.
Operation costs.
The running expenses (see Table 10.2) include the cost for repair
and maintenance, personnel, insurance and electricity (needed for example to
circulate geothermal fluid and to drive heat pumps) if the electrical energy is not
produced within the geothermal heating plant. However, when compared to in-
vestment costs they are relatively low (see Table 10.2). Fuel costs of the geother-
mal/fossil systems are indicated separately within Table 10.2.
Heat generation costs.
On the basis of an interest rate of 4.5% and a depreciation
period according to the technical lifetime, the heat production costs are calculated
for the reference plants described in Table 10.1 and shown in Table 10.2.
With regard to the technical lifetime the following assumptions have been
taken: 30 years for all geothermal plant components, 50 years for buildings and
the district heating network, 20 years for house substations, heat pumps and the
peak load boiler and 15 years for the CHP station.
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