June 23, 2021

Team Profile:
What can Geothermal Energy be Used For?
contributor(s)

Melissa Climo

photo credit:
GNS Science

Geothermal energy has a range of uses, which depend on the fluid temperature at the surface. Applications range from bathing at low temperatures, up to industrial processes and electricity generation at high temperatures. Geothermal fluids can also be used for minerals production processes, and support tourist ventures.

Uses for geothermal energy depend on the fluid temperature at the surface.

Electricity Generation

The highest fluid temperatures are used to generate renewable electricity at geothermal power stations in the Taupō Volcanic Zone and at Ngāwhā, supplying around 17% of New Zealand’s electricity generation.

100 megawatt geothermal power plant in Kawerau, New Zealand. (Credit: Rjglewis)

Direct Heat Use

Processes which need heat can successfully use geothermal energy directly, instead of relying on electricity or fossil fuels.

Many sectors (e.g. tourism, aquaculture, agriculture, industrial, commercial and residential) directly utilise geothermal heat in a range of applications, including timber drying, pulp and paper processing, milk processing, aquaculture, flower growing, vegetable growing, bathing, space heating and cooling, and water heating.

Bathing has the most operations, and industrial process heat uses the most energy. There are over 200 examples of commercial use of high and lower temperature geothermal energy in the Taupo Volcanic Zone, and many other lower temperature operations throughout the country. Check out this Geothermal Use Database for more info.

Geothermally-heated greenhouses at Mokai (Source: GNS Science)

Tourism

Tourism is arguably New Zealand’s oldest geothermal business venture, attracting both domestic and international visitors. Unique volcanic and geothermal environments provide a combination of nature-based, ecological, cultural, historical, wellness/health, geological heritage, industrial and extreme (adventure) tourism experiences.

Geothermal tourist parks offer an opportunity for visitors to explore natural geothermal environments.

Some Central North Island tourism sites combine Māori culture and the geothermal experience, such as at Te Puia, Rotorua (Credit: Fraser Clements).

Mineral Production

Below ground, geothermal fluids are heated as they travel through rock bodies. They interact with the rocks and become increasingly saturated with various minerals and metals, some of which could be processed into saleable products. Historical ventures have mined for sulphur and cinnabar (an ore of mercury) from the Earth, and current geothermally-produced minerals include halloysite clay in Northland, zeolite from Ngakuru, and perlite near Tokoroa.

Recovery of dissolved minerals and metals from geothermal fluids has also been explored. New Zealand fluids contain elements such as silica, lithium and boron, as well as gold and silver, carbonates and sulphates. Additional saleable products could also include sulphuric acid and carbon dioxide.

Geo40 are extracting silica from geothermal fluids at Ohaaki, and testing a process to recover lithium. (Credit: Geo40)

Why Supercritical?

Supercritical geothermal fluids (>5 km, >400°C) offer significantly more energy than conventional geothermal fluids found at current depths (~3.5 km) and reservoir temperatures (<350°C). Supercritical will not replace these conventional resources, but rather complement existing developments, offering potential to increase efficiency, and potentially enable new developments.

A supercritical geothermal well could produce up to ten times the energy of a currently drilled geothermal well. The higher temperatures offered by supercritical geothermal might open an opportunity to supply process heat for higher temperature industrial applications, beyond the current 220°C maximum. And the mineral content of Aotearoa's supercritical fluids is still unknown.

The Geothermal: The Next Generation research programme aims to explore and understand New Zealand’s supercritical resources, with a view to extending the applications for geothermal energy in New Zealand, decarbonising industry and powering sustainable economic growth opportunities.

Reference: Lindal, B., 1973. Industrial and other Application of Geothermal Energy. In: Armstead, H.C.H., Geothermal Energy, UNESCO, Paris, pp.135-148.

 

 

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Geothermal
geothermal energy use
learning
direct use
electricity generation
geothermal tourism
minerals

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