Íkopark Hartberg, Austria

Description of the application

Office building cooling (+ heating and hot water)

General description of the system

The 30.4 kW DEC system has a heat energy input from 12m▓ flat plate collectors and a 30 kW biomass boiler as auxiliary heat source. The peak cooling load of the building is 20 kW and the peak heating load is 24 kW. The number of heating demand hours is 3560 per year. The heating and cooling supply is distributed through air ducts with heat recovery.

Central air-conditioning unit


open cycle (DEC)

Nominal air volume flow rate

 6,000 m3/h

Minimum air volume flow rate

 - m3/h

Desiccant cooling system type

solid desiccant

Desiccant type

Silica Gel

Cooling capacity

30.4 kW (max)

Brand of desiccant unit


Solar thermal

Collector type


Brand of collector

Vacuum-tube collector

Collector area

12 m2 gross area

Tilt angle, orientation

70░ south

Collector fluid


Typical operation temperature



Heat storage

3 m3 water

Cold storage


Auxiliary heating support


Use of auxiliary heating system

heating & cooling

Auxiliary chiller


System performance

Annual cooling load/annual regeneration heat = annual COP = 0.6
kWh primary energy/kWh cooling = solar fraction = 1.66
Daily solar gain = 60 kWh, gain on collector surface 430 kWh/m▓ collector area
Daily electricity demand =65 kWh for AHU, pumps, water treatment etc.
Average collector efficiency is 40%.
The adiabatic operation mode, which does not need the regeneration heat, is important for the enlargement of the COP to 0.6.

System reliability and overall success of the installation

The users and owners of the buildings are satisfied.
The use of the DEC plant is normal satisfying. In case of disturbances there are not yet the suitable persons available to repair, due to the not well known technology. Main problem is the hygiene of the open water basins. Biological cleaning of the water by a biocide and UV-light (254 nm) together with water quality checks is a practical way.  
The centralized cooling system needs a large amount of electricity for ventilation. If renewable heat is used fort the regenerator, the CO2 emissions are significantly reduced.
The following items could be learned at the Hartberg DEC:

  1. The control strategy for all year round operation is not fully developed.
  2. Water treatment have to include also the biologic cleaning (biocide and UV-radiation) of the water. Time by time, especially after long periods without operation, the air humidification facilities have to be cleaned.
  3. Service intervals should be fixed and a staff of educated people is necessary.
  4. Especially protections against lightning damages in the control have to be executed specially in the country side.
  5. The temperature for the regeneration has to be high enough to avoid to high indoor air humidity. 

General information

Type of building  Office building
Location  Hartberg, Austria
Auxiliary heating support  Biomass
In operation since  2000-09
System operated by  Íkopark Hartberg
Air-conditioned area  280 m2
- capacity  30.4 kW max

Specific information

Further specific information about the system are included in the filled in technical questionnaire.


250 K


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

Charlotta Wikler