Environmental Engineering Reference
In-Depth Information
power generation is realised. The low-temperature heat (of about 70 °C) pro-
duced after the electricity generation process is provided to consumers living in
a housing estate (SFH-I) built according to the low-energy design (3,000 h/a)
by means of a small district-heating grid (DH-II, return temperature of about
55 °C). Heat production costs are calculated by means of credits for the heat
supplied by the cogeneration plant at a price of 0.032 €/kWh respectively
8.9 €/GJ (about 26,000 GJ/a).
Based on these frame conditions the investment costs for such plants are discussed
first. Then the operation costs are analysed, and on this basis the energy provision
costs are presented.
Investments.
The costs for drilling the wells including the casings are subject to
considerable variations due to changing geological conditions. On average, the
costs for wells of depths between 4,000 and 5,000 m amount to approximately
1,500 €/m. However, costs do not increase linearly with increasing depths; up to a
depth of 3,000 m costs amount to approximately 1,000 €/m.
The costs of such a well are predominantly determined by the costs for renting
and operating a drilling rig (including personnel and costs for the Diesel fuel),
which on average account for 36 % of the total cost of a well. About 4 % of the
total costs are needed for site preparation and restoration of the drilling site, once
the well is successfully produced, whereas approximately 15 % correspond to
drilling bits and directional drilling services, 12 % correspond to the drilling fluid
and cementation, 20 % to well casing including riser, and 12 % to well head com-
pletion. These shares may vary considerably depending on the local conditions.
Additionally, approximately 235,000 € is needed for the required well pumps
(Table 10.4).
Costs for stimulation are even more uncertain, as according to the geological
conditions at a certain location different frac technologies, frac pressures, frac
proppants, and the quantities to be pressed into the underground need to be ap-
plied. These frac methods are state-of-the-art processes as far as crude oil and
natural gas production is concerned. However this is not true for geothermal
power generation. This is why the costs for, for example, one frac of a fluid vol-
ume of 250 m
3
and approximately 60 t of proppants are conservatively estimated
at 360,000 €. However, if a drilling rig needs to be transferred and installed at a
specific site, costs may rise up to 550,000 €.
Costs for the basic aboveground geothermal fluid circuit including tubes,
valves, and control equipment are strongly varying depending on the ground con-
ditions (e.g. rocky underground densely covered with buildings or sandy agricul-
tural underground). Here the costs are estimated at roughly 600 €/m. For addi-
tional system components directly linked to the thermal water cycle (such as slop
system, filter, etc.) the costs, due to the very different and site specific arrange-
ments, are globally assumed to correlate with the geothermal capacity as 25 €/kW.
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