Environmental Engineering Reference
In-Depth Information
Table 6.4
Levelled Heat Costs in
/kWh
therm
for Solar Thermal Systems for
Domestic Water Heating without Return on Capital and with Annual
Operating Costs of
€
€
40
Substituted amount of energy
Annual 2300 kWh
therm
Annual 1150 kWh
therm
Lifetime
20 years
15 years
20 years
15 years
Investment costs
€
5000
0.13
0.16
0.25
0.32
€
3500
0.09
0.12
0.19
0.24
€
2500
0.07
0.09
0.14
0.18
€
1800
0.06
0.07
0.11
0.14
€
1000
0.04
0.05
0.08
0.09
kWh
therm
and the solar fraction 50 per cent. Hence 2000 kWh
therm
of useful
heat can be substituted by the solar energy system each year. Assuming an
average efficiency for the conventional reference system of 85 per cent, the
annual substituted amount of conventional energy is 2353 kWh
therm
. This
amount of energy is used in the following calculations as the annually
produced energy. However, if the solar energy system is installed in the Earth's
sunbelt region, the solar fraction can be up to 100 per cent and the substituted
energy much higher. In contrast, if the heat demand is lower, the substituted
energy decreases as well. Relatively low annual maintenance costs of
31 are
assumed and the pump of the solar cycle of this example requires 60 kWh
el
of
electricity at a price of
€
0.15/kWh
el
(
9 per year). For an investment cost
A
0
€
€
of
3300, annual operating costs
A
i
of
40 and an operating period of
n
=20
€
€
years, the calculations become:
C
tot
=
A
0
+20·
A
i
=
€
3300 + 20 ·
€
40 =
€
4100
C
a
=
C
tot
/
n
=
205
€
C
E
=
C
a
/
E
a
=
205/2353 kWh
therm
=
0.087/kWh
therm
€
€
Table 6.4 shows the calculations for different investment costs, operating
periods and substituted amount of energy. In moderate climates such as those
of central Europe, the solar heat generation costs are often above the costs of
conventional heating systems. Solar pool heating systems are usually
competitive due to much lower investment costs. The relative investment costs
of large solar thermal systems and solar district heating systems are also lower
so that they can operate at lower cost.
Calculations with return on capital
In addition to the calculations described above without return on capital,
investors usually expect payments of interest for their investment of the order
of usual paid rates for comparable investments. Starting with the payment
A
0
