New Zealand Rock Properties: Determining Thermal Properties of Shallow Soils

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 (ground source) 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 a network of shallow ground temperature monitoring sites in different soil types around New Zealand. These temperatures are used to calculate thermal properties such as thermal diffusivity and volumetric heat capacity, which are key properties used in the design of the ground loop configuration for geothermal heat pump installations. This project aims to provide fundamental supporting information to support the design, development and application of geothermal heat pumps.