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
A few systems show values below 3 which means that the system probably consumes more
electricity than a conventional compression chiller would.
A general conclusion is that in most systems the electricity consumption of the external
components of the cold production (pumps, fans) has not been optimized and is therefore too
high. In the best system in Figure 3 (Garching) the pump in the generator loop has been
exchanged against a more energy efficient one. In addition it is planned to replace the fan of
the dry cooler in the near future which would increase the electrical COP even further.
Another topic is the part load operation of the system. If a system is operated a lot in part
load but the external pumps are still operated at full speed, this will lead to low electrical
COPs. Optimized control strategies for this operation scenario are mandatory to ensure
primary energy savings of the system.
3.4 Total electrical COP of the Solar Cooling System
As a next step, the total electrical COP of the system can be calculated. This includes in
addition to the electrical consumers mentioned before, the electricity consumption of the
pumps in the solar circuit(s) and the electricity consumption of the auxiliary heater and the
associated pumps if applicable.
Total electrical COP, -
8
7
6
5
4
3
2
1
0
Jun Jul Aug
Zaragoza 2008 Maclas Perpignan 2009 Graz 09/10 Sattledt 2007
Chambéry 09/10 Butzbach 2009 Garching 2009 Gleisdorf 2010 Freiburg 09/10
Figure 4: Total electrical COP of 10 solar cooling systems
Figure 4 compares the total electrical COP of 10 systems only for the summer months. The
value for the system in Gröbming is not shown because the system was also used for DHW
preparation and space heating. Therefore, the value is significantly higher but not
comparable.
For the other 10 systems the trend is the same as described in the previous section. But the
total electrical COPs of the systems are obviously somewhat lower than for the cold
production itself, but the more critical factor seems to be the electricity consumption of the
pumps in the chiller circuits and the heat rejection system. These are the components that
need to be optimized in terms of component selection and control strategies.
3.5 Fractional Primary Energy Savings
Now, let’s take a look at the probably most important monitoring result of a solar heating and
cooling system: The primary energy saved by the system.
For this purpose, the primary energy ratio was calculated for both the monitored solar
heating and cooling system and for a conventional reference system delivering the same
amount of heating, cooling and domestic hot water.
The following assumptions were taken for the conventional reference system:
Space heating is done by a fossil fuel boiler without storage tank. The primary energy ratio
for space heating is calculated as follows:
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