Fig 2 illustrates the cooling system for the office and seminar rooms as well as for the server room. Office and seminar rooms are supplied with fresh air via a ventilation system, in which cooling coils are integrated to transfer the cold to the rooms. During working hours, an average air change

of 0.85 was assumed, outside of working hours, only the constant infiltration rate of 0.15 was considered.

For the server room, both a recirculation and a fresh air ventilation system were integrated. The cold production system itself was designed as a solar air conditioning system. From all the different technologies available for heat driven cooling systems, an absorption chiller with a capacity of 50 kW for producing cold water was used and integrated into the system model [6]. In addition, heating, cooling and re-cooling circuits are completing the solar air conditioning system. The heating circuit consists of a solar collector field, a heat storage tank and a thermal back-up heater. The main component of the cooling circuit is a cooling coil for the supply of the building and the server room with cold. For this, the cooling energy is taken from a cold water store. As re­cooling, a wet cooling tower was used.

The cooling system is controlled depending on the temperatures in the building as well as in the server room. Within the office and seminar rooms, the active cooling system operates when the temperature exceeds 26°C For the server room, two different cooling modes have been implemented:

■ In case that the ambient temperature is significantly below the desired server room temperature of 23°C, a fresh air ventilation with an air change of up to 60/h is applied.

■ In case of higher ambient temperatures, the recirculation system in combination with the cooling system is used.

2. Results