Optimal Settings for Direct Geothermal Use Investigated with Numerical Modelling

Abstract

Geothermal energy has been used in the central part of the North Island of New Zealand since people first settled there. Traditionally it was used for bathing and cooking. During the 20th century, uses expanded to include heating and cooling of buildings, green houses and aquaculture farming. Direct geothermal use tends to be located in areas where there is a known heat source with easily accessible heated water; many of New Zealand’s direct use applications are focussed within the Taupo Volcanic Zone, or in areas with hot springs such as Hanmer Springs in the South Island. With the New Zealand government’s ambitious targets to reduce fossil fuel dependencies, clean and efficient sources of energy will become increasingly important. Determining the potential, and potential limitations, of low-temperature geothermal energy will be important to help in establishing the contribution that it can make to the nation’s energy ambitions.
This project aims to identify the ideal settings for low-temperature heat extraction. We will use numerical modelling to determine what rock properties and thermal characteristics result in usable low-temperature geothermal systems. We will distinguish key settings that are suitable for different direct use technologies such as ground-source heat pumps, residential warm water extraction or direct heating for small-scale commercial industry. We can then start to build up a map of the most promising types of geothermal use for different regions in New Zealand.