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
energy factors is shown and then another comparison assuming the same fossil fuel primary
energy factor for all 5 systems.
Fractional primary energy savings, -
100%
80%
60%
40%
20%
0%
-20%
-40%
-60%
-80%
-100%
-120%
-140%
-160%
Nov Dec Jan Feb Mar Apr
Graz 09/10 Chambéry 09/10 Butzbach 2009 Gröbming 09/10 Freiburg 09/10
Figure 7: Fractional primary energy savings for the winter months for the 5 systems where sufficient
monitoring data are available (real primary energy conversion factors)
The system in Graz uses the municipal district heating network as backup (Primary energy
factor 0.96). The fractional primary energy savings are relatively small in November to
February which is clear because of the weather conditions and the very small tilt angle of the
collectors (11°, optimized for summer operation). However, the primary energy savings
reached are still higher (because of the use of district heat instead of a purely fossil backup
source). The primary energy savings assuming the primary energy factor of fossil fuels is
shown in Figure 8. In March and April already much higher savings could be reached.
The system in Chambéry uses electricity as backup source. This is why the fractional primary
energy savings are very negative in months where a lot of backup energy is needed. Figure
8 shows that the situation improves significantly if a gas boiler as backup is used. But in
December and January, the savings are still negative because of high heat losses from the
storage tank. Obviously, an electric heating element as backup source would not make
sense in a real application, but has been used in this experimental installation for simplicity
reasons.
In Butzbach, a natural gas boiler is used as backup heat source. But due to storage heat
losses the primary fractional energy savings are negative in months without much solar
gains.
The system in Gröbming was only monitored in February, March and April. Using 10 as
primary energy factor for biomass, fractional primary energy savings of roughly 90% were
reached. Assuming a fossil primary energy factor makes it more comparable to the other
systems still. Even with that assumption siginifcant savings could be reached. Obviously, the
values increase with increasing solar gains.
Finally, the system in Freiburg uses the adsorption chiller as heat pump in the winter months.
This system concept reaches approximately 35% fractional primary energy savings for all
winter months. These savings have two sources: the primary energy factor for the heat from
the CHP unit and the heat pump effect of the chiller. Using a natural gas boiler as backup
savings are still achieved, but in a range of only 10%. Savings could be increased if the solar
energy is directly used for heating, which was not implemented in the installed system.
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