The Heat Vault Company
Trees store energy from seasons to years.
So must we.
AEVOLITH™ (ay-vo-lith) means eternal stone. It is the Product range brand name for The Heat Vault Company.
HEAT VAULT
Heat Vault is a Geological Thermal Energy Storage (G-TES) system. We drill multiple 50–200 meter boreholes into solid natural rock. Mineral-insulated cables convert electricity to heat, while flexible steel pipework circulates heat carrier fluids in closed loops. This charges the rock to 300°C, allowing for the direct discharge of hot fluid for heating, power, or cooling.
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THE BATTERY REIMAGINED
Comparisons can be tricky. But here's a simple guide. Man-made batteries like Lithium-ion (and other chemistries like sodium) store electricity and supply electricity. They need to be manufactured. Often from exotic materials, which are scarce.
And when built they last for just a few hours and cost a few hundred dollars per kilowatt-hour. They suit rapid responses to ailments of power grids. But are totally uneconomic for long-duration energy storage at the scale required to solve big storage needs. Different battery processes, such as vanadium flow also address the half-day to day storage market.
Thermal batteries, which store heat and supply heat, last longer than power batteries, though still only hours. As containerized systems they suit individual industrial decarbonization markets. But limited by scale, they best serve a megawatt-hour market on a daily cycle of storage need.
Heat Vault stores thermal energy in natural rocks underground. The Earth's Crust is the battery. So there is no limit on scale of storage and gigawatt-hour or even terawatt-hour storage is achievable.
Nor is there a significant limitation on duration, which can be as short as power batteries or as long as decades.
No storage device is manufactured. There are no requirements for critical minerals to be found, processed, used or shipped.
And at less than €200/MWh to build, no other battery system competes.
Heat Vault is bigger scale, longer duration and lower cost than the rest. And it stores heat capable of supplying heat, cooling or power, something unattainable with other technology.
ECONOMIC ADVANTAGE
Our Swedish test-bed proves high efficiency over multiple years. Heat Vault enables true energy arbitrage: take in energy when prices are lowest (or even negative) and supply it when demand peaks. By de-coupling intake from supply, we offer an unassailable "economic value efficiency" that daily-cycle batteries cannot match.
PROVEN SUCCESS
SHOWCASE TEST-BED SITE
We built a Showcase site in Western Sweden at the scale of 1 GWh, built in ancient metamorphic rocks. Even at this relatively small scale capacity and footprint (twenty meters diameter), it is one of the largest such thermal storage capacities. And apart from the clutter of pipes and wires (it is a test-bed after all!), all the storage is underground to fifty meters deep. It has run successfully for two years. In this time we have collected data and simulated the input of 95 degrees celsius hot water, 165 degrees celsius steam and built our own solar PV park with inclined and vertical arrays to model renewables electricity input. As well as energy inputs and outputs we tested how long the storage would last - it's longer than two years! And counting.
MUNICIPAL HEAT SECTOR BLUEPRINT
Sweden has more than 500 municipal heating companies each with similar needs to transform from burning materials like domestic waste and biomass. We spent a year sponsored by the Swedish Energy Agency to analyze the whole heating system for the city of Härnösand in Eastern Sweden. This allowed the development of new options for the heating sector which progressively eliminates hydrocarbons, avoids stranded assets, resolves issues of seasonality, optimizes power and heat supply, reduces or eliminates use of biomass and replacement of ageing biomass assets and makes greater use of renewables excess power and thermal energy storage.
THE BIG PICTURE
Annually, Sweden exports 30 TWh of surplus renewables electricity while dumping 75 TWh of nuclear thermal energy into the sea. Storing this could satisfy the national district heating demand of 55 TWh and prevent a 90% drop in renewable asset value caused by grid flooding.
The Alternative? Continuing to burn biomass and waste costing €15 billion in asset replacement and €1.5 billion annually in feedstock. Between rising EU carbon taxes and the pressure on our forests, "business as usual" is no longer plausible.
Big-scale storage isn't just an option—it’s an imperative.