The modernisation of conference rooms in a hotel in Bremen, Germany, required the installation of an air-conditioning system. Because of the limited space in the plenum above the suspended ceilings, the air ducts for conventional air conditioning could not be installed. The application of a cooled ceiling allowed a reduction in the airflow volume to the minimum needed to meet indoor air quality standards. This helped to solve the space problems in this project. Supply air enters the rooms through outlets in the walls near the floor. Air distribution in the rooms is based on displacement ventilation, which means that the supply air temperature has to be only 3 K below room air temperature. For thermal comfort and to prevent condensation at the ceiling, the room air must be dehumidified. One hundred percent outdoor air is used as supply air, which is then cooled and dehumidified by desiccant cooling. The thermal energy to operate this system comes from a cogeneration unit (gas engine). The principle of this concept and the results obtained in the first year of operation are presented in this paper.

KEYWORDS: Germany, air conditioning, radiant cooling, desiccants, cooling, hotels, displacement ventilation, modernising, indoor air, quality, ceilings, dehumidifying, ventilation, ceiling cooling.