| Abstract |
Shallow geothermal energy is a renewable energy source, where the low enthalpy heat in the shallow subsurface can be exploited using borehole heat exchangers in a combination with heat pumps. Despite the energy saving and CO2 emission reduction potential of the technology, the utilisation of shallow geothermal energy in Denmark is relatively limited compared to e.g. Sweden and Germany. Today, the total number of ground source heat pumps in Denmark is around 27,000, currently increasing by 5,000 per year. By far, most of the existing installations are horizontal closed loop systems, while four to five hundred are borehole heat exchangers, and only some tens are groundwater based open loop systems. However, during the last couple of years the number of borehole heat exchangers has increased significantly, and in 2011 and 2012 more than a hundred new borehole heat exchangers were installed each year. In contrast to our neighbouring countries, the main part of Denmark is situated in a sedimentary basin dominated by soft sediments and variable depth to the water table. Only few investigations of the thermal properties of Danish sediments have been carried out, but preliminary results indicate that the energy extraction may be up to 40% lower for unfavourable geological scenarios compared to more favourable geological conditions, and better knowledge and local experience are needed. The 3-year project “GeoEnergy” aims at paving the way for a wider use of borehole heat exchangers by acquiring and disseminating know-how and developing tools and best practice for the design and installation of systems under typical Danish conditions. The main activities of the project are: – Collection and analysis of existing information and experience, as well as identification of key parameters for planning, design and installation of heat pump systems based on borehole heat exchangers. – A comprehensive mapping and measuring programme for surface temperatures, temperature gradients and thermal properties of different soil types and materials. – Optimization of system design with respect to environment and economy based on experience from existing installations and a new test site. The analysis includes drilling work and completion of boreholes, system control and automation, calculation of energy balance, energy storage (heating and cooling) and modelling of heat and fluid flow. – Development of a publically accessible webbased GIS application using and presenting relevant data from existing databases together with results of the measuring and mapping programme as a tool for system design. – Dissemination activities including training and education, workshops and seminars, technical guidelines and recommendations for the legal framework. |