How to Make a Thermal Battery: A Guide for New Zealand Industry

Thermal energy storage is emerging as one of the most promising tools for decarbonising industry. It allows us to stockpile energy as heat, then use it when we need it — bridging the gap between cheap but variable renewable electricity and industrial processes that demand a constant, reliable supply of heat.

At Carbon Partners, we see thermal batteries as a practical, near-term solution for New Zealand industry. They can connect our growing renewable electricity supply with factories, food processors, and exporters that still rely heavily on fossil fuels for process heat.

So how do you make a thermal battery? And what’s the right scale for New Zealand? Let’s break it down.

Step 1: Choose Your Energy Source

The first step is deciding where the heat comes from. Most systems today are power-to-heat: electricity goes in, heat comes out. The simplest method is resistive heating — running a current through a material, just like a toaster element, but at industrial scale.

Some systems connect directly to renewable sources such as wind turbines or solar panels that aren’t hooked up to the grid. Others draw power from the grid at times when electricity is cheap or abundant, helping to balance demand with supply.

Another approach is to capture and store waste heat from existing processes, which boosts efficiency and reduces fuel use. While waste-heat-based systems may not reach the extreme temperatures of electricity-charged systems, they can still provide valuable savings, especially in high-temperature industries like cement, steel, and glass.

Step 2: Choose Your Storage Material

The next question is: what holds the heat?

Thermal batteries need storage media that are cheap, durable, and capable of withstanding very high temperatures. Options include:

Bricks or carbon blocks – proven, low-cost, and capable of exceeding 1,000°C.
Crushed rock or composite mixtures – simple, scalable, and locally sourced.
Molten materials – such as salts or metals, which can be pumped and circulated, offering flexibility but adding system complexity.

The choice depends on cost, durability, and the kind of heat delivery required.

Step 3: Choose Your Delivery Method

Once the heat is stored, how do you get it back out?

Direct heat – the simplest method, blowing air or gas over the storage medium to produce hot air or steam.
Electricity generation – converting heat back into electricity via turbines or thermophotovoltaics, though this usually reduces efficiency.
Combined heat and power (CHP) – providing both steam for industrial processes and some electricity when needed.

For most New Zealand industrial users, direct heat and steam are the priorities. Exactly what’s needed for drying, pasteurisation, sterilisation, and cooking.

The Global Push: Thermal Battery Alliance

Globally, a wave of new companies and research programmes are building large-scale thermal batteries. Members of the Thermal Battery Alliance include Rondo Energy, Antora Energy, Malta, and others, each exploring different materials and configurations.

One clear trend is towards very large systems — often 300MWh and above. This scale makes sense globally because:

Economies of scale – fixed costs (steel vessels, insulation, controls) are better spread over large units.
Target customers – global cement, steel, and chemical plants consume thousands of MWh of heat daily.
Thermal efficiency – larger volumes retain heat more effectively than small units.
Investor appetite – big projects offer dramatic, immediate emissions cuts.

But this scale doesn’t necessarily suit New Zealand. Our industries – dairy plants, food factories, timber mills – are typically medium-sized, needing 100-200 MWh of thermal storage at a time. That’s where local innovation comes in.

Made in New Zealand: Right-Sized Thermal Batteries

At Carbon Partners, we’re working to design and deploy smaller-scale thermal batteries, specifically tailored to New Zealand’s industrial landscape.

Sized for our needs – 100 to 200MWh (and larger) units fit the load profile of most local sites.
Flexible siting – modular, smaller systems can be installed at multiple plants instead of one giant facility.
Lower entry cost smaller units reduce capital risk for first movers.
Designed for renewables – these batteries will be charged by New Zealand’s abundant wind, solar, and hydro resources, providing low-carbon steam and heat on demand.

By building here in New Zealand, we can cut dependence on imported fossil fuels, strengthen industrial competitiveness, and demonstrate solutions that the world’s mid-sized industrial nations will also need.

Summary

Thermal batteries are not science fiction. They are being deployed today, overseas at massive scale, and soon here in New Zealand at the right scale for our industries.

With the right design, they can store cheap renewable electricity, deliver reliable high-temperature heat, and slash emissions from some of our hardest-to-abate sectors.

At Carbon Partners, we believe the future of industrial energy in New Zealand is renewable, reliable, and thermal.