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
Figure 5: Fractional primary energy savings of the monitored systems without heat backup for the
summer months
Five systems show positive fractional primary energy savings, in 3 cases these savings are
negative.
Let’s first look at the positive cases: The best is the system in Garching which already had
the best total electrical COP. The system reaches approximately 60% in July and August.
Four other systems (Perpignan, Butzbach, Graz and Chambéry) had reached total electrical
COPs between 3 and 5 which translate into fractional primary energy savings between
approximately 10 and 40%. While it is good that the primary energy savings of these systems
are positive, as has been said before all of the systems can still be optimized (especially in
terms of electricity consumption) which would further increase the fractional primary energy
savings.
The systems with negative fractional primary energy savings are the ones in Zaragoza,
Maclas and Sattledt which had already shown very low total electrical COPs. The fractional
primary energy savings of these systems can very likely become positive by means of
system optimization.
The three systems shown in Figure 6 use not only solar energy to operate the sorption chiller
but a pellets boiler (Gröbming), a gas driven CHP unit (Freiburg) and a combination of a
conventional gas boiler and different rapeseed oil fired CHP units (Gleisdorf) respectively.
For a differentiated analysis primary energy savings were calculated based on three different
boundary conditions and assumptions respectively:
1) Primary energy factor for the fuel is the “non renewable primary energy factor” for the
renewable heat sources (pellets in Gröbming: RES =0.9, RES =10 kWh fuel /kWh PE ; natural
gas CHP in Freiburg: RES =1, RES =1.08 kWh heat /kWh PE; rapeseed oil CHP in Gleisdorf:
RES =1, RES =-2.53 kWh heat /kWh PE (in Figure 6: “res PE factor” or “CHP PE factor”)
2) In case of CHP as auxiliary heater the heat is counted for free in terms of non renewable
primary energy consumption based on the assumption, that the CHP is operated
“electricity production controlled” and heat therefore is waste heat. (in Figure 6: “heat
free”)
3) For comparison reasons the auxiliary heater is assumed to be the reference natural gas
boiler with boiler efficiency boiler = 0.95 and primary energy factor of natural gas fossil =
0.9 kWh fuel /kWh PE (in Figure 6: “fossil PE factor”)
The system in Gröbming was only measured in August. At first sight it seems to be the best
system in this monitoring campaign (80% of fractional primary energy savings based on “res
PE factor” are reached). However, there are two reasons for that: First, the backup system
uses a wood pellets boiler with a primary energy factor of 10 kWh fuel /kWh PE . In addition,
unlike the other 10 systems, the system was also used for domestic hot water preparation.
Both factors are very positive for the performance of a solar heating and cooling system.
Mainly due to the different fuel type it makes it difficult to compare the results with the other
systems. Therefore, a comparison assuming the same (fossil) primary energy factor
(0.9 kWh fuel /kWh PE ) was performed. In Figure 6 this is shown in the three hatched columns
on the right hand side. For Gröbming, the fractional primary energy savings are thus reduced
to roughly 30%.
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