Town Hall and Service Center in Gleisdorf, Austria

Description of the application

The system is supplying two office buildings with space cooling and space heating energy. One building is the Town Hall, an old construction from 1894, renovated in 2008. The other one is the Service Center next to the Town Hall, built in 2008. The technical devices are situated in the basement there. The Town Hall is a heavy weight building with small windows and the Service Center is a lightweight construction with a big glass façade all around with no external shading devices.
An absorption cooling machine is generating cold water for the fan coils in the Town Hall and for the ceiling cooling elements in the Service Center. The desiccant evaporative cooling (DEC) device is conditioning the supply air for the office rooms in the Service Center. During the cooling period, the system is autonomous solar thermally driven. District heating backup based on natural gas is used during the heating period. 

General description of the system

An open desiccant evaporative and a closed absorption cycle for generating cooling energy are employed. Both systems are using solar thermal generated heat to regenerate the processes. The sorption wheel is coated with silica gel and the absorption cooling machine uses water as refrigerant and lithium bromide as solvent. The desiccant device is conditioning the supply air of the Service-Center. The cold water, generated by the absorption cooling machine, is used to cover internal and external heat gains in both office buildings. In winter the desiccant air handling unit is able to recover up to 85% of the ventilation heat with both sorption and heat recovery wheels, the solar collectors are in assistance to the space heating. In summer and winter the solar generated heat is stored in one buffer storage and all demanded energy is taken out of it. The district heating backup is also heating the tank.

Central air-conditioning units


open cycle (DEC)

Nominal air volume flow rate

6,180 m3/h

Minimum air volume flow rate

2,400 m3/h

Desiccant cooling system type

solid desiccant

Desiccant type

Silica Gel

Cooling capacity

max. 35 kW

Brand of desiccant unit

Klingenburg HYSG


closed cycle

Nominal capacity

35 kWcold

Type of closed system

Absorption (water/lithium bromide)

Brand of chiller unit

Yazaki WFC SC10

Chilled water application

ceiling cooling elements and fan coils



Heat rejection system

wet open cooling tower (Baltimore FXT 27, 100 kW)

Solar thermal

Collector type

high temperature flat plate (Teflon foil between glass and absorber)

Brand of collector

ÖkoTech Gluatmugl HT

Collector area

302 m2 gross (134 m2 flat roof, 168 m2 solar trees)

Tilt angle, orientation

22°, 32° (flat roof) and 30° , 330° (solar trees)

Collector fluid


Typical operation temperature

88 °C driving temperature for the absorption cooling machine


Heat storage

1 x 4,600 l

Cold storage

1 x 1,000 l

Auxiliary heating support

natural gas fired district heating

Use of auxiliary heating system

during heating period

Auxiliary chiller


System performance

The absorption cooling machine was in-situ evaluated with a thermal coefficient of performance of 0.43 measured in average from May to September 2009. The electrical COP of the thermal powered cold generation by the absorption chiller was about 5, including solar heat production the electrical COP was about 4.5 for solar autonomous cooling.
The high temperature flat plate collectors were in-situ evaluated with an efficiency of 53% at irradiation of 690 W/m², 9 °C ambient and 63 °C mean collector temperature on February 11th, 2009, including all heat losses of primary solar loop and the external heat exchanger. According to the collector test data sheet the efficiency of only the collector itself would be 58% under this operating condition. The second collector field area on the “solar trees” was set into operation on September 1st, 2009. Solar autonomous cooling will be accomplished during the cooling period 2010. Solar gain of the first part of collector installed on the flat roof was about 400 kWh/m² during the period October 2008 until August 2009 with solar fraction of about 15%. The electrical COP of the solar thermal system was quite high: 66 in average for the same period (46 from October 2008 to April 2009 and 72 from May to August 2009).

System reliability and overall success of the installation

The monitoring of the whole plant started in October 2008. During the cooling period 2009 the cooling energy demand of the cold storage could be covered all time but the operation of the chiller hardly ever was steady state. But quite often the room temperatures in the Service Center exceeded the set point temperature. The reason seems to be a lack of cooling power output of the ceiling elements and switched off fan coils. Reasons for that are that most parts of the hydraulic loop of the ceilings are closed because window contacts detect open windows and therefore the controller stops cooling in the relevant room. Therefore, if the central controller switches off cooling, the chiller of course is switched off as well which is resulting in bad performing on and off operation. Lesson learned: the whole system including cold/heat distribution must work properly! Chiller and DEC system itself was operating without problems when overall control was asking for them.
Actually one mistake happened: The recooling return temperature from the cooling tower into the cooling machine was a certain time beneath 24°C and so the lithium bromide as solvent within the chiller crystallized. The lithium bromide could be melted again by heating up the whole machine long enough to about 90°C. The chiller is one year in operation since that time.

General information

Type of building  Office building
Location  Gleisdorf, Austria
In operation since  2008
System operated by  Community of Gleisdorf
Air-conditioned area  2,000 m2
Cooling load  Town Hall 38 kW, Service Centre 24 kW


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For more information on the project please feel free to contact:

Alexander Thür