In future, renewable energy resources will be an increasing component of New Zealand’s 2050 “zero carbon” energy portfolio, but the nation has some distance to go to achieve this target. All the carbon-friendly energy sources need to significantly increase their contribution.
Using recent Ministry of Business, Innovation and Employment (MBIE) data:
In 2018, New Zealand’s total primary energy supply (Figure 1) amounted to ~890 PJ. This is dominated by ~59% carbon-sourced fuels (oil 34%, natural gas 19% and coal 6%), and ~41% renewables (made up of geothermal 21%, hydro 10.6%, wood 6.8%, wind 0.8%, biogas 0.4%, Solar 0.1% and liquid biofuels 0.016%).
Electricity in New Zealand is predominantly generated from renewable sources. Hydro, geothermal and natural gas are the top three energy sources contributing to electricity production (Figure 2). In 2018, 155 PJ of electricity was generated, with 82% of that produced from renewable sources (hydro 61%, geothermal 17%, wind 5% and other renewable 2%) and 18% from carbon-based sources (12% gas, 3% coal and oil).
In 2018, New Zealand’s total energy consumed was ~590 PJ (Figure 3). This is dominated by consumption of 69% carbon-based fuels (oil 48%, natural gas 13, coal 4% and carbon-based electricity 4%), and 31% renewable energy sources (electricity 20%, other 11%). The ‘Renewable Other’ category includes wood, biogas, solar and geothermal direct heat supplies.
Geothermal accounts for about 5.5% of the total consumed energy, of which 4% is from geothermally produced electricity (~ 26PJ), and 1.5% is from direct geothermal energy use (~ 8PJ).
The 2017 recorded greenhouse gas equivalent total carbon emissions from the energy sector (from both supply and use) amounted to ~33,000 ktonnes CO2-e, with international air travel and shipping amounting to ~4,200 ktonnes CO2-e in additional emissions. A broad sub-sector breakdown of carbon emissions from energy supply and use in percentage terms is shown in Figure 4.
The geothermal contribution to greenhouse gas emissions amounted to 814.8 ktonnes in 2017 (ca. 2.5%). It is included in the fugitive (non-combustion) category of the figure below, because geothermal emissions are not associated with combustion processes.
Mclean and Richardson (2019) provide data on greenhouse gas emissions from New Zealand’s geothermal power plants since 2010. The annual emissions from geothermal electricity facilities amount to ~70% of the recorded total geothermal emissions where for 2017, Mclean and Richardson (2019) reported ~610 ktonnes CO2-e and for 2018 ~560 ktonnes.
Geothermal energy is a sound contributor to New Zealand’s energy supply. The challenge for the geothermal sector is to sustainably use conventional geothermal systems to the fullest possible extent, and to go beyond conventional resources, tapping into deeper supercritical heat resources - expected to offer substantial additional energy potential.