WKSP I IEA

Objectives
Reducing operating costs and increasing energy efficiency and user comfort are self-evident goals in the planning process for office buildings. Based on this principle, more and more office buildings in Germany have been built with energy pile, geothermal probe or foundation absorber systems for heating and cooling since the mid-1990s. Heat pumps connected to the ground extract heat from the ground in winter and make it available to the building for heating purposes. The ground cools down and can be used as a heat sink for cooling the building during the summer months.
The system concepts are developed to suit the geological conditions, the building structure and the heating and cooling requirements of the building. To date, highly complex simulation software has been used in the planning process. Simple planning modules are not currently available for widespread use. There is a lack of systematic studies of implemented systems.

The BMWi-funded research and development project "WKSP - Heat and cold storage in the foundation area of energy-efficient office buildings" is attempting to close this gap with the help of a large-scale field test.
Initial results of the scientific analysis of the operating behavior and energy efficiency as well as findings and experiences of planners, building owners and operators show that the general functionality of these systems is given. However, a lack of experience in planning, implementation and operation often leads to problems in practice.
The decisive factor for successful operation is generally not the heat and cold storage system itself, but the sensible technical and operational integration of the system into the complex overall system consisting of the subsoil, technical systems, building and user. Depending on the temperatures in the ground, the combination with surface systems as low-temperature heating and high-temperature cooling systems is ideal. Due to the relatively small temperature range of geothermal systems compared to conventional systems and the thermal system inertia, operating errors in geothermal systems often have significant and long-term consequences. The basic prerequisite for a balanced seasonal energy balance in the ground and thus for long-term operation of the systems is metrological documentation of the actual function of buildings and systems for heat and cold storage in the foundation area. This is the only way to uncover deviations from planning assumptions and errors step by step, optimize operation and shorten the adjustment phase.

The aim is to pool the experience gained from the WKSP project for future projects, optimize planning tools and develop operating rules. There is still a need for optimization and development in order to achieve full user acceptance and better cost-effectiveness of geothermal probe storage systems, energy pile systems and foundation absorbers. As part of a continuation of the WKSP project, further objects are to be measured more precisely with regard to the temperatures underground and the carryover of heat from the geothermal probe field through the groundwater flow, and deviations between simulated and measured values in reality are to be investigated.

• Institute of Foundation Engineering and Soil Mechanics, TU Braunschweig Meteocontrol GmbH, Augsburg International cooperation partners: WKSP is part of the Annex 20 project of the International Energy Agency (IEA).

• Federal Ministry of Economics and Technology (BMWi)