The technical planning of the system was done by a group of engineering companies, named Rittgen 1(Fachbereich Heizung, Sanitar, Luftung) and Becker 2(Fachbereich Elektrotechnik). Supervisor was the Staatsbauamt (LBB3) Trier.

The earth heat exchanger starts his function in the year 2000, but today the measurement system is already not completely installed.

The air flow from outside is 15 mT(h m2), or 20-30 mT(h-Person). The dimensioning foundation for this are the rules in [DIN 1946], which defines the higher flow of both calculation possibilities. The single flows are given in figure 3.

Ingenieurburo Josef Rittgen, Am Weidengraben 7, 54292 Trier Ingenieurburo Klaus Becker, Herzogenbuscher StraBe 1, 54292 Trier Landesamt Liegenschafts — und Baubetreuung

The air in and out volume flow can be regulated by frequency controlled ventilators with a pressure sensor signal. The air conditioning systems have momentarily to be started manually in the rooms.

An additional CO2-Monitoring System controls the air inlet stream between the two 80% and 100% ventilator power level. In order to keep the noise level under the limit of 40 dB in the lecture rooms, sound damper were installed. Finally the fresh air has to be cleaned with a fine dust filter of class F7.

The installed heat recovery system at the Umwelt-Campus, with the help of a 14kW electrical heat pump, guarantees a gap free and continuous working condition in winter. The pipes for the recovery heat exchange were mounted symmetrically parallel to the earth heat exchanger concrete air pipes.

The heat pump has fixed working hours and works continuously from 07:00 to 19:00 a clock during the lecture times and variable working times for special courses, seminars, workshops etc. at weekend. This kind of control is to be preferred because of the slow time dependence of the heat exchange processes. As a result of experiences, the earth around the air pipes needs approximately three days to get a stationary temperature load after a cooling down period. The intermittent heat exchange process and the distances in the pipe circuit are arguments against a temperature controlled working condition for the heat

The buildings of the Campus are provided with a complex sensor, measurement and actor system for the automation system, which supervises and controls with a central DDC[33] all parameters, equipments and functions. All pumps, valves, drivers, louvers and adjusting flap valves temperature and are time dependent controlled with a software, and most of the process data are to be stored and evaluated. For this, all over the building there are microprocessor controlled units (PCU’s[34]), wich are interconnected for communication via a LAN bus system.

Additional to the sensors for the building control, the earth for the heat storage and both concrete air pipes have 48 PT100[35] sensors (4-wires) and two pressure head sensors systems[36] for an indirect velocity measurement. 24 temperature sensors were for this purpose installed in the earth in distances of 6m, 17,5m, 30m and 54m.

With 16 more sensors, at the same distances, the inner surface temperature of the concrete pipes is measured sideways and on the top. The remaining 8 sensors are room temperature sensors, which are mounted approximately 20 cm away from the inner concrete surface of the pipes into the air inlet flow.

These data are used to guide the actual status of the air earth heat exchanger with D/A — converter[37] via a bus system to a central process controller. With this, it is possible to store all data for detailed analysis and to give information on public displays for students and visitors.