Possible alternative approaches to the dry year problem

Non-hydro options are also being explored as possible ways to resolve the dry year problem in a 100% renewable electricity system.

In addition to pumped hydro and other hydro-based options, the NZ Battery Project is also looking at other possible technologies or approaches to address the dry year problem.

The NZ Battery Project team generated an initial long-list of alternative approaches, which were then screened against criteria and feedback received through targeted external engagement, and in consultation with the Technical Reference Group.

5 broad alternative technologies were identified as having the technical potential to help manage dry year risk:

  • biomass, biogas and biofuels
  • geothermal energy, including novel approaches to using it
  • hydrogen or other green vectors (e.g. green ammonia)
  • compressed or liquid air
  • flow batteries

Expert engineers were commissioned to assess the suitability of these 5 alternatives for long-term, large-scale renewable energy storage and whether they are applicable in a New Zealand context. Following this, hydrogen, flexible geothermal generation and bioenergy were found to have the most potential.  

None of these three options is likely to solve the dry year problem on its own, as they can’t practically store enough energy to meet the electricity needs during a dry year event. However, they each show potential in contributing to a multi-solution approach. 

Analysis into the feasibility of these 3 alternatives is continuing throughout the rest of this year. 

The Project is also exploring whether large-scale planned load reduction can play a role in addressing the dry year problem. This would involve forming agreements with large electricity consumers to reduce their demand when supply is scarce, such as during a dry year event.

Baseline scenario

Wind, solar and geothermal generation are existing technologies on the New Zealand electricity system. Given their costs and relative maturity, these technologies are expected to see increased investment in coming years. One option for solving the dry year problem in a 100% renewable electricity system is to rely exclusively on these technologies to meet increased demand for electricity and replace fossil-fuelled generation. The NZ Battery Project is using overbuild of renewables as a baseline scenario to compare against other options.

Last updated: 06 July 2022