THERMAL ROCK PROPERTIES – COMPARISONS OF APPARENT VALUES DETERMINED FROM IN-SITU TEMPERATURE PROFILES, AND VALUES DETERMINED BY LABORATORY MEASUREMENTS

Abstract

New Zealand’s rocks and soils provide a clean, renewable, and 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 geothermal heat pump to provide heating in the winter and cooling in the summer. The amount of heat stored in the rocks and soils are largely influenced by local climatic factors, such as air temperature, sunshine hours, rainfall and the thermal properties of the rocks and soils.
This paper presents data from several shallow in-ground temperature monitoring sites in different soil types around New Zealand. Thermal diffusivity of the soils is determined from the in-situ temperature profiles and compared to values determined from laboratory measurements using a divided bar apparatus. Preliminary results indicate a close agreement in values. Further investigations into climatic influences and moisture content on thermal properties are underway.