Geoheat: Geothermal Heat

Geoheat is a reliable, low-carbon energy source derived from geothermal energy in the Earth's crust, used in a variety of industries and direct applications.

NO or LOW CARBON – Depending on the application, geothermal can reduce the atmospheric greenhouse gas emissions by between 80 to 100% relative to natural gas supplied heat for the same duty.

COST EFFECTIVE – Geoheat is supplying delivered energy at an industrial scale at ~$10 / GJ (including the cost of carbon). This is cheaper than other renewable options and fossil fuels.

RENEWABLE – Geothermal energy is renewable energy, recognised as such in New Zealand law (RMA 1991). Sustainable management of geothermal energy resources provides an underpinning ethos for businesses seeking to future proof energy supply with sustainability credentials.

AVAILABLE – Commercial and industrial energy can be delivered from established geoheat suppliers with lead times as short as 12 months. Geothermal Heat pump technology enables ambient / low temperature geothermal to be accessed, with these temperatures accessible across much of NZ, particularly where groundwater is accessible.

PROVEN AT SCALE – Geoheat resources and energy use has been proven at individual supply scales at capacities up to 100 MWth, supplying ~3PJ of energy per annum.

LOW RISK – Geoheat has been used in New Zealand for over 60 years, and is backed by a wealth of established engineering expertise able to support plant design, installation, maintenance and operation.

Geoheat Explained

Geoheat is heat derived from geothermal energy in the Earth’s crust, it is tomorrow’s energy available today, with well-established technologies in use to harness this reliable, low-carbon energy source. In Aotearoa New Zealand, Geoheat is used in the pulp and paper and timber industries, in food processing, horticulture, floriculture, agriculture, aquaculture, heating / cooling applications, tourism, spa and health & balneology (therapeutical bathing) applications.

Geoheat is drawn from ambient to high temperature sources and depending on the temperature required may be augmented with a heat pump to boost (or reduce) the temperature supplied to the application.

Industrial scale use occurs at Kawerau, Tauhara, Mokai and Ohaaki, often associated with high temperature geothermal electricity generation operations.

Medium and smaller sized facilities occur in places such as Rotorua, Tauranga, Tokaanu, Taupō, Te Aroha, Miranda, Hamner Springs and Maruia Hot Springs. The facilities are often based on bathing type activities requiring temperatures of less than 60oC with supply capacity of less than 5 MWth.

Ambient temperature geothermal with heat pump augmentation is geographically spread all across New Zealand. Christchurch has seen a significant uptake in the use of this technology as part of the post 2010 / 2011 earthquake rebuilding. A paper by Seward and Carey (2020) discusses four Christchurch facilities that have adopted groundwater aquifer GSHP (ground source heat pump) systems. Ambient geothermal GSHP systems using groundwater at 15oC have been assessed for the Whakatane Growers and the Whakatane Hospital facilities replacing fossil fired heating systems as part the Bay of Plenty Regional Energy Transition Accelerator work (Carey et al 2024).

There is wide applicability of ambient geothermal using GSHP technology in the covered crop sector across New Zealand as this sector looks to decarbonise.

Geoheat in Action

Wood Pellet Manufacturing – Taupō

Wood pellet manufacturer, Nature’s Flame, taps into Contact Energy’s Tauhara geothermal industrial heat supply, enabling them to dry 150,000 tonnes of pellets per annum, which are then used in assisting both Fonterra and Open Country Dairy to decarbonise parts of their dairy processing operations. Annual GHG (greenhouse gas) emissions reductions of 84,000 tonnes are achieved at the Fonterra Te Awamutu site and 35,000 tonnes at Open Country’s Waharoa site.

Kiln Drying Timber – Kawerau, Taupō, Ohaaki

Carter Holt Harvey (Kawerau), Sequal Lumber (Kawerau), Tenon (Taupō) and Ohaaki Thermal Kilns (Ohaaki) using geothermal energy in kiln drying timber. The Kawerau operations use geothermal steam, the Taupō operation uses two phase geothermal fluid and the Ohaaki operation geothermal water.

Tissue Paper Manufacturing - Kawerau

Tissue and toilet paper manufacturer Essity, at Kawerau, made headlines when it switched its tissue manufacturing processes to geothermal in 2010. This dramatically reduced the company’s carbon emissions (a reduction of 17,000 tonnes per annum), as well as increased the reliability of their manufacturing processes. Essity is in the process of converting one of two of its paper machines, KPM3, completely to geothermal. This $15.5 million project is a first for the world and will further reduce the site carbon emissions by 6400 tonnes per annum. The Government Investment in Decarbonising Industry fund supported the project with a grant of $1.65 million.

Tūaropaki - Mokai

Tūaropaki Trust is an Ahu Whenua trust is involved in business ventures at Mokai, centred on sustainability and the circular economy. The geothermal resource is tapped into not just for generating electricity, but also industrial scale geoheat supplied to the Gourmet Mokai greenhouses and used to create process steam for the Miraka milk processing facility.

Tnue - Taupō

Total Nutrient Use Efficiency (Tnue) is the first tenant in the He Ahi Eco-Industrial Park, Taupō, with the facilities completed at the end of 2023 and production scheduled to commence in February 2024. Tnue, part financed (37%) by NZ Green Investment Finance Limited produces specialist fertiliser, with the geoheat being used in the manufacture of the control release membrane on the granules. The controlled release improves environmental outcomes by increasing the nutrient use, with more nitrogen being taken up by the plants and less nitrogen leached to the ground water.

Wai Ariki Hot Springs and Spa - Rotorua

The Wai Ariki Hot Springs and Spa is a NZD 60 Million Ngāti Whakaue venture that uses geothermal energy to heat the pools and the facility. With the entrance guarded by six statues of Ngāti Whakaue tīpuna, Wai Ariki is uniquely built on Ngāti Whakaue culture, healing practices and manaakitanga (hospitality). There are a range of bathing and spa experiences, such as Wai Whakaora (Restorative Journey) and Te Āhuru Mōwai (The Sanctuary).

Baywave Aquatic and Leisure Centre - Mount Maunganui

The Baywave TECT Aquatic and Leisure Centre in Mount Manganui, with the biggest wave pool in New Zealand, uses low temperature geothermal water from beneath the site to heat the pools and other water facilities. Consents allow the take of up to ~30MWth of heat.

Arts Centre - Christchurch

The Christchurch Art Centre uses 13oC aquifer water from ~130m below the site with the temperatures augmented with heat pumps supplying up to 2.4 MWth to the buildings on site. This energy system was retrofitted as part of the refurbishment undertaken after the 2011 Christchurch earthquake. This poster provides more detail, whilst this paper covering the project was presented at the 2020 World Geothermal Congress.

He Ahi Eco-Industrial Park - Taupō

The He Ahi Eco-Industrial Park under development by Te Pae o Waimihia with Contact Energy supplying geothermal energy opens up the opportunity for geoheat supply to small and medium sized enterprises who up to now have been unable to access geothermal heat because of the high hurdle of the entry capital required. The 45 hectare site north east of Taupō has ~40 sites, half of which can be supplied with geoheat operates on contract leasing for the facilities, with geothermal energy purchased through a separate supply contract.

International Case Studies

Further examples of geoheat uses can found in these case studies from the International Energy Agency (IEA) Geothermal.

Where is Geoheat Available?

Geoheat is available New Zealand wide with natural thermal energy stored in the crust and groundwater systems. The subsurface temperature remains relatively stable year-round compared with the more variable ambient air temperature. The map from Reyes et al (2010) below identifies thermal spring locations where some of this thermal energy emanates from the subsurface. Groundwater at ambient temperature is available across Aotearoa.

Geoheat Strategy for Aotearoa New Zealand

The Geoheat Strategy seeks to unlock potential, capitalise on interest in renewable energy, assist in coordinating effort and resources of both industry and the government in increasing geoheat energy use.

Achieving the goals of the Geoheat Strategy will contribute towards meeting Aotearoa’s low carbon energy goals, promote renewable energy, contribute to regional economic and social development, and further increase renewable and clean energy use which will assist in meeting our 2030 greenhouse gas reduction commitments.

Action Plans, developed every two years, are being used to implement the Strategy, providing guidance and enabling flexibility to adapt to the prevailing circumstances.

Future of Geoheat

New Zealand is a world leader in Geoheat with an understanding of the technological, economic and environmental benefits of geothermal use for heating and cooling. There is significant untapped potential that can be used to supply new and existing businesses with low carbon heat energy with flow on benefits, including creating employment in the ventures that use geothermal energy, and the businesses that service those ventures, enhancing regional economies.

Applications noted below are not yet in the NZ inventory but in operation in other places around the globe:

  • Fish drying / processing – Iceland (Ragnarsson et al 2021)
  • Fish farming (salmon / trout / sole / tilapia) – Iceland (Ragnarsson et al 2021) / USA (Blue Ridge Aquaculture, Virginia, USA).
  • Seaweed Drying – Iceland (Ragnarsson et al 2021)
  • Bioengineering / Bio genetics – Iceland ORF Genetics
  • Gourmet table salt production – Iceland (Ragnarsson et al 2021)
  • Diatomaceous earth processing – Iceland (Ragnarsson et al 2021)
  • Alligator / reptile tourist park - Colorado Gators, USA
  • Fruit dehydrating - Domo de San Pedro in Nayarit, Mexico.
  • Pavement Snow melting – Iceland, Japan, USA and Argentina (Lund 2005)

Geoheat Presentations