IEA Solar Heating and Cooling Programm - NachhaltigWirtschaften.at

IEA SHC Task 38 Solar Air Conditioning and Refrigeration
Subtask A Report, Date:…
chillers. Thus, small particles from fabrication, e.g. swarfs, circulate through the whole hot
water circuits and may cause pollution of filters which can lead to measurement errors.
Actually, the flow meter in the gas boiler circuit was not working accurately due to the
problem mentioned above. For avoiding this kind of problem a careful flushing of the total
circuit after the installation is recommended.
The entry of small particles through the open wet cooling towers caused the pollution of the
cooling water circuit. This led to a serious problem as the volume flow rates were much lower
than normally and consequently too high cooling water temperatures entered the chiller. The
solution of the problem was reached by the installation of an automated filter backwashing
system, which starts every 16 minutes, and by a daily elutriation of the cooling towers. This
circumstance should be considered by the installation of open cooling towers in areas with a
high density of plants.
At the beginning, one of the two absorption chillers was not working due to a vacuum
leakage. As an insolvency procedure of the chiller manufacturer was in progress in 2009 it
took one year to solve the problem in the respective chiller. However, a general
recommendation in order to avoid such problems cannot be given.
A special characteristic of the suninverse absorption chiller is the great flexibility in terms of
driving temperature range. After the start phase of the chiller the chilled water production can
be kept up until the driving temperatures drops slightly below 60°C. Since the second chiller
was repaired and thus both chillers could be operated, the driving circuits were connected in
series in order to test the above mentioned characteristic. The advantage of the serial
connection is an increase in the temperature spread for the collector system. The experience
that could be made with this connection variation was consistently positive. The first
absorption chiller produces chilled water for supply air cooling and dehumidification, the
second chiller supplies preferentially chilled ceilings and a cooling shaft on a higher chilled
water temperature level. The operation of the chillers is stable; there are no start and stop
phases and the operation of the chillers can be kept up continuously for several hours.
Anyway, the common parallel connection of the chillers’ generators with the hot water
storage is also possible by switching a valve.
The acceptance of the solar autonomous air-conditioning during summer by the occupants
(teachers, students) is big and it is stated as fully sufficient.
Furthermore, there is no extra input of fossil fuel for the chillers’ operation necessary in order
to overcome short periods with room air states outside the comfort range.
7 Conclusions
The plant for solar autonomous air-conditioning in summer in the low energy building of the
Technical College Butzbach is built up relatively complex. In this case the reason lies in the
testing of different connection variations in the driving and chilled water circuit, also for
educational purposes.
The intended system operation was not possible due to the malfunction of one chiller in 2009
and the big delay of the reparation due to the insolvency process of the chiller manufacturing
company. Further disturbances of the system’s operation were caused by increased shading
of the collector as a result of construction measures and pollution problems in the cooling
water circuit. It is evident that the heat rejection is still a weak link in the component chain
and it deserves closer attention also from the manufacturer’s part.
Beyond that, the operation of the collector, of the absorption chiller 1 and the other hydraulic
components has been very reliable. No damage results from collector stagnations. In spite of
the above mentioned disturbances the occupants affirmed their satisfaction with the system
at the final project meeting in September 2010. They also pointed out that the room air
states in the seminar rooms improved significantly. The chosen concept, especially with