Shallow geothermal energy is being used increasingly often in new office buildings. The advantage of this renewable energy source is that the ground can be used alternately for both heating and cooling purposes, depending on the season. The use of geothermal energy has been further promoted by the German Renewable Energies Heat Act (EEWärmeG), which has been in force since the start of 2009 and provides for the partial use of renewable energy sources for heating and cooling new buildings and for water heating in new buildings.

Shallow geothermal energy can be used very efficiently in combination with heating and cooling systems that operate at a temperature level close to that of the ground. In heating operation, the heating energy supplied by ground-source heat pumps is between three and five times the drive energy. Free cooling in summer is even more efficient, as electrical energy is only consumed by the circulation pumps. Annual system coefficients of performance ranging between 10 and 35 can thus be achieved.

involved in this comparatively new area are still relatively inexperienced with the technology available. These systems are very sensitive to errors and faults because of the low temperature differences between the ground and the heating/cooling equipment in the building. Faulty operation can reduce the current efficiency of the system, and can also affect its performance in the years to come.

A research project conducted by the Institute of Building Services and Energy Design (IGS) at the Technical University of Braunschweig and supported by the German Federal Ministry of Economics and Technology has investigated the energy efficiency and economic efficiency of eleven buildings that use borehole heat exchangers, energy piles or ground absorbers. The project also involved the optimisation of operation of five of the systems evaluated. One of the goals of the project was to develop operating rules based on the experience gathered. A similar project supported by the German Federal Ministry of Economics and Technology and concentrating on well systems and borehole heat exchanger systems is also being conducted by the Technical Equipment of Buildings Section at the Institute of Design and Building Construction at the Leibniz Universität Hannover. This project’s monitoring programme covers nine buildings where systems operation will be examined and optimised. This will provide a basis for improving planning tools for the design of system components located in the ground and for specifying measurement and control details for shallow geothermal systems.