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© geoENERGIE Konzept GmbH

© Hubacher Engineering
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German and Swiss design consultants report

Rüdiger Grimm

Managing partner of geoENERGIE Konzept GmbH – an internationally active specialist design office for geothermal energy, which was founded in January 2007

Around 25,000 ground source heat pumps are currently installed each year in Germany. In order to achieve efficient and sustainable operation, a smooth interaction between the building services technology, geothermal engineers and drilling technology is imperative – it is only when this tallies that the system will show a correspondingly high annual performance factor. However, the operating data is not even known for many systems. This means that planning, installation and operating errors are therefore not even recognised, making them difficult to alleviate when problems occur.
Therefore a substantial focus of our daily work as planning consultants for shallow geothermal energy is concerned with advising customers about implementing monitoring systems at an early stage. This can occur at different processing levels and ranges from the simple recording of the heating and electricity requirements and determining the annual performance factor to detailed online monitoring with data transferred at one-minute intervals.
At any rate it should be noted that official requirements stipulated in water law-related authorisations, such as for example the submission of annual balances or the regular measurement of subsoil temperatures, do not represent excessive demands but ultimately benefit the user.

Peter Hubacher

Owner of the Hubacher Engineering office in Engelburg, Switzerland

Despite intensive research, the efficiency of heat pump systems has still not reached the desired level. In Switzerland, field monitoring has been conducted for more than 16 years. The researchers opted at the beginning for a simple recording system so that the budget could cover as large a range of systems as possible. The monitoring of field systems was intended to close the initial gaps in knowledge. That has proved worthwhile, since the initially very modest results regarding the efficiency of small heat pumps triggered a competitive process that has positively influenced the development of heat pumps. Whereas the annual performance factor APF for air-water heat pumps was initially around 2.6, today 3.0 or even higher APF values can be expected. With brine-water heat pumps, the value has increased from around 3.4 to 4.0–4.5.
The field monitoring has provided the manufacturing companies and installers with a diverse range of experience values and operating information, which, with a sample size of 280 systems, is also statistically secured. The most important aspects concern not just mean values for the APF, the degree of utilisation, susceptibility to malfunctions, operating behaviour and running times as well as the heat production and electricity consumption but also suitable hydraulic systems and the maintenance and servicing costs. Such research projects make it easier to find answers to issues relating to energy policy and electricity consumption, including concerning electricity grid loads.

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