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
Fractional primary energy savings
150%
100%
50%
0%
-50%
-100%
-150%
-200%
-250%
-300%
Jun Jul Aug
Gröbming 09/10 (res PE factor) Gleisdorf 2010 (CHP PE factor) Freiburg 09/10 (CHP PE factor)
Gleisdorf 2010 (heat free)
Freiburg 09/10 (heat free)
Gröbming (fossil PE factor) Gleisdorf (fossil PE factor) Freiburg (fossil PE factor)
Figure 6: Fractional primary energy savings of the monitored systems with heat backup for the
summer months, primary energy factors as RES (solid columns), primary energy factors with heat
from CHP is for free (crossed columns) and fossil primary energy factor (hatched columns). In June
only Freiburg, in August only Freiburg and Gleisdorf, in August all 3 systems.
Die beiden “heat free” Varianten sehen fast gleich aus, vielleicht sollte man es doch besser
bunt machen!
Finally there are two systems with partly high negative fractional primary energy “savings”
which had good or very good total electrical COPs: Freiburg and Gleisdorf. The reason for
negative savings in this case is the use of a heat backup system rather than a cold backup
system. In both cases, these are combined heat and power plants with primary energy
factors RES better than the reference fossil fuel fossil . But the solar fractions of both plants are
too low to compensate for the lower seasonal performance factor of the thermally driven
chiller compared to the reference compression chiller.
In the case of Freiburg, the solar fraction is still relatively high, leading to only minus 5-45%
(Jun-Aug) savings in the case “CHP PE factor” but real savings of plus 39-49% (Jun-Aug) in
the case “heat free”.
In Gleisdorf, the system is mainly operated with non-solar but partly fossil and partly
renewable heat sources, which translates in case of “CHP PE factor” into minus 200%
“savings” in July (mainly natural gas boiler in operation) and 57% real savings in August
(mainly the rapeseed fired CHP in operation). In case of “heat free” in July again due to
natural gas boiler minus 213% “savings” are achieved, while in August the “savings” are only
minus 7% due to mainly CHP operation.
In the case “fossil PE factor” the last three columns each month are comparable in terms of
heat performance quality of the systems. They show clearly that both systems in Gleisdorf
and Freiburg with only cold demand and high ratio of heat backup do not reach high enough
solar fraction for “virtual” primary energy savings. The system in Gröbming is able to save
primary energy mainly thanks to comparably high domestic hot water demand (893 kWh) and
space heating demand (139 kWh) in comparison to only little cooling demand (175 kWh).
Concluding it can be stated that in solar cooling systems with heat backup based on CHP the
primary energy savings are strongly depending on the type of fuel the CHP is fired (fossil or
renewable) and how the boundary conditions for the CHP operation are defined (credit
thanks to electricity generation or waste heat for free).
3.5.2 Winter
For the winter months only for 5 systems there are sufficient data to analyze the fractional
primary energy savings. One important factor is again the used backup heat source.
Therefore, just like for the summer case first a comparison using the real existing primary
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