After 5 years, the Geothermal: the Next Generation programme is coming to a close.
Here, we summarise the Techno-Economics component of the research. This research is closing the knowledge gap for advancing understanding of the superhot geothermal opportunity for New Zealand. One end the work investigated superhot resources and at the other, the possible market that these resources might supply energy into. Both point to superhot geothermal contributing, possibly quite significantly, into the New Zealand energy sector, particularly the electricity sector between 2037 and 2050, and beyond.
Between these end points, studies considered how useful it might be to access superhot geothermal resources using wellbore modelling to compare current geothermal well outputs with possible superhot well outputs. Indicative geological prognoses were prepared and at-depth temperature and pressure conditions were identified seeking to provide information for well design. The use of higher temperature fluids points to more efficient geothermal power plants.
The material below provides more information on the completed work. This is early information in seeking to increase technology readiness of superhot geothermal. Further technical progress and a range of studies must be undertaken before superhot is commercially viable. Progressing superhot to commercial technology is undoubtably going to be challenging, however there is no information prepared through the GNG programme, that indicates that New Zealand should not continue to take up the superhot geothermal opportunity. The possible rewards for the nation are very significant.
A superhot geothermal inventory for onshore Taupō Volcanic Zone geothermal prospects was compiled by GNS Science. Considering only identifiable resource volumes, outside of any regulatory protected geothermal systems, and within the depth range of 3.5 to 6 km, the inventory identifies that there is a possible additional geothermal electricity capacity for New Zealand of up to ~3.5 GWe, producing about 29 TWh /yr.
An electricity market modelling study forecast that superhot geothermal power plants could contribute additional capacity of up to 2 GWe to the New Zealand grid by 2050. The study identified that up to 2 GWe of capacity (15 TWh/yr of generation) would be cost effective to construct between 2037 and 2050 in a fully renewable electricity generation scenario event if the cost to construct superhot is twice the cost of current geothermal facilities construction and 1.3 GWe would be cost competitive if gas peaking electricity generation is still allowed beyond 2037.
This requirement for additional capacity is a consequence of the significant increase in demand, and hence requirement for electricity generation forecast to be required as New Zealand transitions to Net Zero.
This is a strategic Net Zero opportunity for New Zealand. It should be investigated and evaluated, working towards realising superhot geothermal generation as part of the nation’s energy transition.
Accessible data & publications:
Higher geothermal temperatures should enable more efficient use of the extracted geothermal energy. The most likely sector in New Zealand to utilise superhot geothermal is the electricity sector. Process heat might be a secondary taker of energy from an electricity facility, but the process heat industry itself is unlikely to be the primary developer / operator of an superhot geothermal energy supply because of the larger quantities of heat energy that are required for an electricity generation facility and the much smaller amounts utilised by a process heat facility.
Additional research and inquiry should be embarked upon now to ensure superhot geothermal developments can align with New Zealand’s low carbon economy and energy sector aspirations. Sector-wide roll out ideally needs to occur before 2050. Working backwards, pilot and scale up demonstration of supercritical energy production would be needed by about 2040, and thus, the first exploration wells need to be drilled by 2030 or soon after.
Strategically, there are four questions to be addressed:
Addressing each of these questions requires expert activity across science, engineering, finance, planning/regulatory, and societal and political engagement.
Accessible data & publications:
Appropriate well designs need to be developed to access superhot geothermal resources.
Well bore modelling has been undertaken seeking to forecast possible superhot geothermal well production at different feed-zone depths, with different casing configurations. For well design, information on the likely underground formations and conditions that are to be drilled through to reach the targeted production zone location(s) need to be assessed. Four indicative prognoses have been developed. These will need to be revisited once actual sites for drilling superhot wells are known. Design pressures, temperatures and fluid composition need to be adequately specified for design to enable appropriate materials and componentry to be specified. Some R+D and innovation is expected to be required for well design and drilling.
Because of the efficiency advantages gained from the higher supply temperatures, the power output for a given thermal input will be greater for facilities supplied from superhot geothermal resources than from sub-critical geothermal plant. This should result in a requirement for smaller power plant heat rejection systems for an equivalent plant output. Further work could usefully be undertaken to consider power plant facilitates appropriate for the New Zealand circumstances.
Accessible data & publications: