Report: Underground heat storage of higher temperatures

In the research report ‘Thermal efficiency of high and middle high temperature heat storage in the ground,’ existing projects were investigated. The report concerned systems of MTO (Middle Temperature Storage, 30-60oC ) and HTS systems (High Temperature Storage, >60oC). In these systems, excesses of heat can be stored underground until they can be used. The most important advantage of the systems is that direct heat can be delivered without needing additional heat sources. This makes these systems more energy efficient than lower temperature WKO systems.

The research has been carried out by IF Technology. It is part of the research ‘More energy from aquifers’ that is being jointly carried out by IF and DLV glass and energy under the heading of the Glasshouse as Energy Source.

In the Netherlands, heat storage in an aquifer with temperatures above 25˚C is permitted, providing there are no apparent or unacceptable consequences for the underground environment. Heat storage is a technique that has been in use since the 1990s, but has not enjoyed any great breakthroughs. This is due to the cost/benefit and energy efficiency ratios of the system. It is expected that the demand for large scale heat storage will increase in the future due to a bigger focus on the use of residual heat, geothermic and solar heat.

In the Netherlands, 7 MTS/HTS large scare heat storage systems have been brought into use in the last 30 years (not taking closed systems into account). Three of these have, for various reasons, already ceased working. In the report, the thermic efficiency of a number of projects has been assessed and development guidance suggested in order to improve the efficiency of new systems. In addition to this, an important point is the system integration (the collaboration between the under and above ground systems). Often, after the initial development of the system the design coordination between the various elements causes problems due to many separate parties involved in the development of the system having an effect on the whole system.

This project is being financed by the programme Glasshouse as Energy Source, the innovation and action programme from LTO Glaskracht Nederland and the ministry of Economic Affairs.

Source: energiek2020