Whether you operate a small commercial building or manage a district heating network, Seasonal Thermal Energy Storage (STES) is a powerful way to decarbonize heating—minimizing emissions and cutting long-term costs. We use a Borehole Thermal Energy Storage (BTES) system for large-scale, seasonal heat capture, providing stable, predictable energy when needed. Our unique hexagonal-ring design offers flexible storage and retrieval at different temperatures, ensuring maximum efficiency regardless of your application. By switching to BTES, you reduce reliance on fossil fuels, lower emissions, and gain greater control over your heating expenses.
Whether you’re harnessing surplus heat from industrial processes or capturing solar energy for colder months, our Borehole Thermal Energy Storage (BTES) seamlessly integrates with your existing heating system to provide heat when you need it. Store heat underground for winter, cut your heating bills, reduce emissions, and even cool your facilities during summer. It’s a truly adaptable solution that evolves with your energy needs, giving you greater independence from conventional fuels.
Store heat in Spring and Summer to reduce your heating bills during Autumn and Winter.
Capture and store industrial waste heat for more efficient energy usage.
Reduce your dependence on external fuel sources and stabilize your supply.
Replace fossil fuels with stored thermal energy to shrink your carbon footprint.
Regulate building temperature by extracting ambient heat to your thermal storage.
Utilize the storage to ensure you have year-round stable and efficient heating and cooling.
Long duration storage provides a mechanism to capture excess heat during warmer months for use during cooler months. It’s particularly useful for district heating networks that tend to have a steady supply year-round. This results in excess heat during the summer, while winter demand exceeds available production. Seasonal storage resolves this demand timing issue. The same concept applies to companies that have a waste heat stream, which can be captured to produce heating in the winter.
Properly sizing thermal storage is crucial to matching heat supply with demand. With over ten successful installations ranging from tens of kilowatt-hours to 1 GWh, we’ve honed our dimensioning expertise. By adjusting the number of rings and drilling depth, we can scale the storage capacity to meet specific thermal requirements—ensuring a cost-effective and reliable solution every time.
Our BTES features a unique hexagonal ring formation, engineered for straightforward installation and scalable to capacities ranging from 300 MWh up to 6 GWh. Each ring is subdivided into sectors, with a smart controller continuously monitoring temperatures to optimize performance. The storage core remains the hottest, while each successive ring cools toward the outer edge. By selecting the appropriate number of rings and drilling depth—based on your annual demand—we can tailor the system to your needs. The table below illustrates the smallest and largest capacities for each ring size, assuming a clay geology.
The table below illustrates the smallest and largest capacities for each ring size, assuming a clay geology.
| Rings [r] |
Diameter [m] |
Depth [m] |
Area [m2] |
Boreholes [bh] |
Storage Capacity* [MWh] |
Power [kW] |
|---|---|---|---|---|---|---|
| 6 | 30 | 15 | 590 | 126 | 380 | 110 |
| 6 | 30 | 30 | 590 | 126 | 760 | 189 |
| 8 | 40 | 20 | 1040 | 216 | 900 | 216 |
| 8 | 40 | 40 | 1040 | 216 | 1800 | 432 |
| 10 | 50 | 25 | 1630 | 330 | 1700 | 413 |
| 10 | 50 | 50 | 1630 | 330 | 3500 | 825 |
| 12 | 60 | 30 | 2340 | 468 | 3000 | 702 |
| 12 | 60 | 60 | 2340 | 468 | 6000 | 1404 |
| Rings [r] |
Diameter [m] |
Depth [m] |
Area [m2] |
Boreholes [bh] |
Storage Capacity* [MWh] |
Power [kW] |
|---|---|---|---|---|---|---|
| 6 | 30 | 15 | 590 | 126 | 380 | 110 |
| 6 | 30 | 30 | 590 | 126 | 760 | 189 |
| 8 | 40 | 20 | 1040 | 216 | 900 | 216 |
| 8 | 40 | 40 | 1040 | 216 | 1800 | 432 |
| 10 | 50 | 25 | 1630 | 330 | 1700 | 413 |
| 10 | 50 | 50 | 1630 | 330 | 3500 | 825 |
| 12 | 60 | 30 | 2340 | 468 | 3000 | 702 |
| 12 | 60 | 60 | 2340 | 468 | 6000 | 1404 |
*Capacity changes depending on drilling depth, delta T and geology of the site.
A typical BTES installation starts with excavation, which can take one to five days. Drilling follows and may last anywhere from two weeks to three months, depending on the project size and number of rigs. Once drilling is complete, installing the bunker and commissioning the storage takes about one to two weeks. After that, the system operates for 30 plus years, and the land above can be used as a car park, sports field, or other light-purpose area.
A pit of approximately 1.5m is excavated where the BTES will be installed. Excavation is typically completed in just one to five days, depending on the storage size and the number of excavators.
The required number of boreholes will be drilled in the pit. Drilling takes between two weeks and three months, depending on the storage size and number of drilling rigs.
The central bunker will be installed, and all pipes will be connected. Bunker Installation and storage commissioning takes approximately one to two weeks, even for large sites.
The storage is covered with layers of sand and insulation. Ground above is reusable. Good uses include car park, sports field, recreational area, or light structure.
Many people assume that thermal storage is just another form of ground-source geothermal heating, but there’s a crucial distinction between the two. Although both involve drilling boreholes, there is a key difference which we will explain in this section.
Traditional geothermal boreholes extract natural pre-existing thermal energy from deep underground. To find sufficient heat, drilling to a significant depth is typically required.
In contrast, BTES systems use shallow boreholes. They inject heat into the ground, raising the base soil temperature considerably and effectively creating a shallow geothermal heat source. Only the heat that was added is subsequently extracted.
Our storage system is engineered to capture and store heat in water up to 90 °C, accommodating everything from industrial waste heat and surplus district heating to renewable solar thermal. This versatility gives you the freedom to tap into the most cost-effective, eco-friendly options available. Plus, we can convert excess electricity into stored heat via a heat pump—supporting grid balancing and ensuring no energy goes to waste.
Our Borehole Thermal Energy Storage (BTES) can take heat from various sources at different temperatures up to 90°C—all within the same storage. Because the core remains the hottest area and the outer rings are cooler, we strategically inject or extract heat to/from the optimal location for maximizing efficiency.
In the absence of a source of heat, solar thermal panels can be installed either on land mounted frames, on top of an existing roof, or in place of an existing roof. Our solar thermal panels have multiple associated patients.
Waste heat from industry can be captured and stored for later use. The smart controller can take heat at different temperatures from various waste heat streams, feeding those to the BTES.
Water can be used to cool servers in a datacenter, which generates a significant waste heat stream. This heat can be stored in the BTES and retrieved to heat buildings or to add to a district heating network.
Our long duration thermal storage is designed to harness a wide range of diverse heat sources in the form of hot water up to 90 °C. The system allows capture of multiple sources and temperatures into a single storage.
BTES Storages can be distributed throughout the district heating network, or near the heat production facility. The smart controller connects to the district heating network through a heat exchanger.
Waste heat from hydrogen production can be stored for later use. When local demand is low, it can be fed into a district heating network, improving energy efficiency and reducing reliance on fossil fuels.
During summer, ambient building heat can be extracted from the air conditioning HVAC system. This excess heat is transferred through an air-to-water heat changer and stored in BTES for later use.
In the absence of a source of heat, solar thermal panels can be installed either on land mounted frames, on top of an existing roof, or in place of an existing roof. Our solar thermal panels have multiple associated patients.
Waste heat from industry can be captured and stored for later use. The smart controller can take heat at different temperatures from various waste heat streams, feeding those to the BTES.
Water can be used to cool servers in a datacenter, which generates a significant waste heat stream. This heat can be stored in the BTES and retrieved to heat buildings or to add to a district heating network.
Our long duration thermal storage is designed to harness a wide range of diverse heat sources in the form of hot water up to 90 °C. The system allows capture of multiple sources and temperatures into a single storage.
BTES Storages can be distributed throughout the district heating network, or near the heat production facility. The smart controller connects to the district heating network through a heat exchanger.
Waste heat from hydrogen production can be stored for later use. When local demand is low, it can be fed into a district heating network, improving energy efficiency and reducing reliance on fossil fuels.
During summer, ambient building heat can be extracted from the air conditioning HVAC system. This excess heat is transferred through an air-to-water heat changer and stored in BTES for later use.
The two business cases below highlight the strong financial returns of our Borehole Thermal Energy Storage (BTES) systems. In one scenario, a 1 GWh BTES fueled by waste heat can achieve a payback of under two years, fully installed. In the other, a 300 MWh BTES with solar thermal panels can achieve breakeven in just five years—even with the cost of solar collectors included. We ensure commercial viability by standardizing our designs and using our smart controller to balance heating demand and supply with maximum efficiency, providing a swift return on investment for diverse energy needs.
You can explore some of our customer references showcasing both the electrical and thermal solutions. From commercial buildings to industrial facilities, these case studies highlight some of the possibilities with our systems. Book a call to find out how we can help you lower your energy costs.
Complete our short questionnaire, and we’ll craft a detailed proposal tailored to your specific requirements. From emission reductions, to cost savings, to payback timelines and installation details, our team will provide a comprehensive breakdown—ensuring you have all the information you need to make a confident decision.
Whether you’re looking for electrical or thermal solutions, or a way to further optimize your energy strategy, our full range of products is designed to meet your evolving needs. Explore what else we offer to discover how we can help you achieve even greater savings and resilience.
We’d love to hear from you. Whether you have questions, want a personalized quote, or are ready to start your energy storage journey, our team is here to help. Fill out the form below and we’ll be in touch soon.
Heliostorage Oy
Sokojantie 879
67500 Kokkola
Finland
+358 44 972 8921
sales@heliostorage.com
