IEA Solar Heating and Cooling Programm - NachhaltigWirtschaften.at

IEA SHC Task 38 Solar Air Conditioning and Refrigeration Subtask A Report A-D3b, Date: December 2010
c) Combined heat and power plants (CHP):
The primary energy for heat taken from a CHP plant is calculated according to the following
equation:
RES
H
fuel
Q
fuel
CHP
W
el
el
Where Q CHP is the heat produced by the CHP plant, H fuel is the fuel used (in kWh) and W el is
the electricity produced. The electricity produced by the CHP replaces electricity in the power
grid, thus el is the primary energy factor for the electricity in the grid. Expressed in CHP
efficiencies this gives:
RES
th
1
el
fuel
el
Where th is the thermal efficiency of the CHP and el is the electric efficiency of the CHP.
With this formalism, the efficiency of the heat source RES has to be considered as equal to 1.
In order to compare different systems in different locations the same average primary factors
for electricity ( elect =0.4 kWh el /kWh PE ) and fuel ( fuel = fossil =0.9 kWh fuel /kWh PE ) should be
used. Local values should be used in order to evaluate the performance of the system in a
specific surrounding.
For Freiburg ( th =49.2%; el =26.2%), using average values for elec =0.4 kWh el /kWh PE and
fuel =0.9 kWh fuel /kWh PE (natural gas) we obtain an average value for the CHP of
RES =1.08 kWh heat /kWh PE , with local values ( fossil =0.909 kWh fuel /kWh PE ;
elec =0.36 kWh el /kWh PE ) we obtain an average value for the CHP of RES =1.32
kWh heat /kWh PE .
For Gleisdorf thermal and electrical efficiency of the two bio-fuel (rapeseed oil) CHP’s needs
to be estimated based on data sheets, because fuel consumption was not measured. The
following values were assumed: th =45%; el =24%. Using average values for elec =0.4 and
fuel = 2.35 kWh fuel /kWh PE (rapeseed oil) we obtain an average value for the CHP of:
RES = -2.53 kWh heat /kWh PE . This negative value shows that the produced electricity is
replacing more non renewable energy from conventional (fossil) electricity production ( el x
fuel = 0.24 x 2.35 = 0.564 kWh el /kWh PE instead of 0.4 kWh el /kWh PE ) than non renewable
energy remains in the produced heat by the rapeseed oil fired CHP.
To present the results more clearly, the graphs of the fractional primary energy savings are
divided into summer and winter. This way, systems that were only operated or monitored in
summer can be taken out from the winter graphs.
3.5.1 Summer
All 11 monitored systems could be analyzed for summer operation. In Figure 5 all systems
that have no backup system in summer or a cold backup system are shown.
Fractional primary energy
savings, -
80%
60%
40%
20%
0%
-20%
-40%
-60%
-80%
-100%
Jun Jul Aug
Zaragoza 2008 Maclas 2009 Perpignan 2009 Graz 09/10 Sattledt 2007
Chambéry 09/10 Butzbach 2009 Garching 2009
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