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District heating operators

Cost effective heating solutions minimal CO2 impact.

Large scale energy storage

The storage maintains heat efficiently for months with minimal losses and operates at just 1% of today’s battery cost. This enables long-term control of energy costs, including lower operating costs and a clear path towards fossil-free district heating.

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Financing of Grensle's energy storage at the customer's premises

The facility is built next to the district heating network to minimize heat losses and connection costs. The district heating operator can choose between two financing options for the energy storage:
 
Option 1: Grensle finances, builds and owns the energy storage facility. The district heating company buys heat at an agreed cost, with the option to buy the facility from Grensle at a later stage. This will be the option that Grensle advocates for customers during the first five-year period. The option burdens Grensle’s cash, which is why the company needs to raise large amounts of external capital.
 
Option 2: The district heating company finances and owns the energy storage facility. Grensle takes care of construction, commissioning and maintenance through a long-term service agreement. When the technology is scaled up and Grensle sees that many customers want to own the energy storage themselves, this option will also be offered.
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Seasonal usage

The storage maintains heat efficiently for months with minimal losses and operates at just 1% of today’s battery cost. This enables long-term control of energy costs, including lower operating costs and a clear path towards fossil-free district heating.

180 days storage cycle in Grensles large-scale mineral storages. Save energy from summer to winter.

Go for a full storage and shut dow your combustion boilers. Go to zero C02-emissions.

Become CO2-neutral and make your heat customers more satisfied by charging your storage with 100% renewable energy.

FAQ

Our system uses electricity from renewable sources to heat a large mass of rock. The heat is then stored within the rock and can be extracted later to generate electricity or provide heat. This is achieved using a heat exchanger system that circulates air through the hot rock, transferring the heat energy to where it is needed. This process allows us to store energy efficiently and release it when required, bridging the gap between renewable energy production and consumer demand.

Thermal energy storage offers several key benefits, including improved grid stability, increased utilisation of renewable energy sources, and reduced reliance on fossil fuels. By storing excess energy produced during peak renewable generation times, we can provide a consistent and reliable supply of clean energy even when the sun is not shining or the wind is not blowing. This makes renewable energy more dependable and cost effective.

Our hot rock thermal energy storage system is compatible with a wide range of renewable energy sources, including solar, wind, and hydroelectric power. Any excess electricity generated from these sources can be efficiently stored in our system, providing a versatile solution for integrating various renewable energy technologies into the grid. This flexibility makes our technology an ideal choice for diverse energy landscapes.

Our hot rock thermal energy storage system is designed for long duration energy storage, capable of retaining heat for days, weeks or even months. This capability is essential for seasonal energy storage, such as saving solar energy from summer for use in winter. The longevity of energy storage depends on several factors, but our systems are optimised to minimise heat loss and ensure maximum energy retention over extended periods.

District heating companies can either let Grensle finance and own the facility, purchasing heat at an agreed price, or choose to own it themselves while Grensle manages construction, commissioning, and maintenance through a service agreement.

By storing cheap, renewable energy and using it during peak demand, operators can significantly lower operational costs and stabilize their energy supply. The investment also provides independence from volatile waste and fuel markets.

Grensle’s technology is fully scalable—from smaller, local systems to large-scale seasonal storage capable of supplying entire cities. When built at scale, the system becomes even more cost-efficient.

The storage is designed for more than 50 years of operation, with minimal maintenance requirements and no risk of degradation over time. It is built from natural, non-toxic materials, ensuring both safety and sustainability.

By replacing combustion-based heat production, Grensle’s technology eliminates local emissions and dependence on imported fuels such as waste, biomass, coal, or gas. This enables district heating networks to reach their CO₂-reduction goals faster and operate entirely fossil-free.