The battery project has come down to two options — enlarging Lake Onslow or the portfolio approach, which draws on producing biomass-based energy logs, using other technologies and ramping up geothermal energy.
Biomass uses logs burned in a boiler to produce high-pressure steam. This steam flows over a series of turbine blades, causing them to rotate. The rotation of the turbine drives a generator, producing electricity.
Ministry of Business, Innovation and Employment NZ battery project acting manager Susan Hall said supply-chain logistics was a key factor to work through when considering a biomass dry-year solution.
She said New Zealand had several locations with concentrations of sustainably-managed exotic forest, enough to supply a biomass plant.
In a dry year, it would take about 560,000 tonnes of sustainably-managed logs out of circulation, which is about 1.5% of New Zealand’s annual exotic log harvest. It could be built in any part of NZ.
"Using biomass to support a dry-year solution doesn’t necessarily require a new and complex transport system. The concept is based around redirecting low-quality logs that would otherwise be transported to a port for export.
"To minimise emissions associated with transporting logs, the base case considers the power plant should be located within 70km of the forestry plantations."
The base case also involves a steady stream of log supplies to a stockpile, rather than variable movements, which will smooth out the demand for labour and trucks.
"One of the key issues identified was constraints on the supply of truck drivers ... a focus on truck driver recruitment would be required in order to provide the additional capacity required if this option was to proceed. Although rail may offer an alternative transport option."
She said while the portfolio approach was likely to include biomass and geothermal technologies, it may include other technologies.
The battery project would talk to the market about solutions and technologies they might offer and firm up how a portfolio approach could work.
