Thermal Properties of New Zealand’s Rocks and Soils

Abstract

New Zealand’s rocks and soils provide a sustainable energy source for heating and cooling of buildings. Incoming solar energy is absorbed and stored by the earth, creating a relatively constant ground temperature year round that can be utilised with a ground source heat pump (GSHP) to provide heating in the winter and cooling in the summer. Part 1 presents an update of below-ground temperature measurements in several locations around New Zealand. Temperature monitoring boreholes installed at Wairakei (Taupo), Raukura (Hamilton) and Lincoln (Canterbury) are logging in situ temperatures at depth, from the surface down to 13 m. These temperatures can be used to calculate thermal properties of the soils. Part 2 presents a desktop study of New Zealand’s climatic areas, common soil types and geology. Air temperature was spatially combined with soil type, soil temperature and geology to identify areas of unique temperature and ground properties. This regional scale study highlights areas of unique ground and climate properties in which to install future in-ground temperature monitoring borehole. The data presented in this paper aims to provide fundamental information to improve the design of GSHP ground loops in New Zealand.