Low-Temperature geothermal – a decarbonising solution for covered crop growers in New Zealand?

Abstract

Low-temperature geothermal energy can provide a lowcarbon, energy efficient solution for low-temperature heat users in New Zealand. Many places in the world are already utilising their ambient and low-temperature geothermal resources for space heat and cooling, including residential and commercial buildings, district heating systems, retirement villages, schools, swimming pools, and greenhouses.
The Netherlands is a standout example of converting their greenhouses from using natural gas to utilising their natural deep 80°C water resources (located at ~2-3km depths). The Netherland has set a target of 43% of greenhouse heating to be sources by geothermal by 2030, removing more that 30PJ of natural gas combustion on an annual basis.
Many covered crop growers in New Zealand, are seeking means to decarbonise their operations and are investigating the potential of utilising geothermal for their heating needs. GNS Science is working with New Zealand’s horticulture industry to investigate the potential of low-medium temperature geothermal resources to meet heating demands for covered crop growers. Initial work will focus on understanding the potential of ambient groundwater systems. These cool groundwater temperatures remain stable throughout the year, providing an ideal heat source for ground-source heat pump systems to convert to an optimum space heating temperature to distribute through the soil and air within the glasshouse. Other sources of stable low-grade temperatures include the natural thermal gradient of the shallow sediments and rocks, and surface water (including seawater, lakes and rivers).
This paper discusses the opportunities of using geothermal resources in New Zealand, for decarbonizing the horticulture industry.