The right storage solution for the right energy system
There is no single solution for large-scale thermal energy storage.
The optimal technology depends on local conditions, including energy demand, available heat and cooling sources, geology, temperature levels, available land and the surrounding energy infrastructure.
At Thermox Technology, we take a system-level approach to identify how different technologies can work individually or together to optimize district heating and cooling.
Underground Thermal Energy Storage
Large-scale storage for seasonal energy balancing
Underground thermal energy storage enables large quantities of surplus heat or cooling to be stored for months and used when demand is higher.
By shifting energy between seasons, these systems can help district heating and cooling networks make better use of waste heat and renewable energy while reducing the need for peak and reserve capacity.
Best suited for: Large district energy systems with substantial seasonal imbalances and access to surplus energy.
ATES
Aquifer Thermal Energy Storage
ATES stores heat and cooling in underground groundwater reservoirs, typically using separate warm and cold wells.
Where hydrogeological conditions are suitable, ATES can provide very high efficiency and low storage costs. However, its applicability depends strongly on local groundwater conditions and permitting requirements.
Best suited for: Urban areas, campuses, commercial districts and data centres with suitable aquifers.
BTES
Borehole Thermal Energy Storage
BTES uses fields of closely spaced boreholes to store thermal energy in the surrounding bedrock.
It is a robust and predictable technology with a long service life and can be deployed in many geological environments. Its main limitations are the land area required and relatively high initial investment.
Best suited for: Residential developments, new urban districts and municipal energy systems.
PTES
Pit Thermal Energy Storage
PTES stores large volumes of heated water in insulated, excavated reservoirs.
The technology is relatively simple and can offer very low storage costs at large scale. Its main requirement is access to substantial land area, making it particularly attractive outside dense urban environments. The analysis also notes typical operating temperatures of approximately 40–90°C.
Best suited for: District heating systems with available land, solar thermal installations and smaller cities or communities.
Solid-Material Thermal Storage
Storing energy in concrete, rock or other solid materials
Thermal energy can also be stored in solid materials such as concrete, stone or slag, either above or below ground.
These solutions are robust, avoid groundwater-related risks and can sometimes be integrated directly into buildings or infrastructure. Their thermal capacity and heat-transfer performance can, however, be lower than water-based alternatives.
Best suited for: Industrial applications, infrastructure and building-integrated solutions.
High-Temperature Thermal Storage
Thermal storage for industrial applications
High-temperature storage uses materials such as molten salts or ceramics to store energy at temperatures typically between 200°C and 600°C.
The technology offers high energy density and can be integrated with industrial processes or electricity generation. For conventional district heating, however, these temperature levels may be unnecessarily high and the systems more complex and costly.
Best suited for: Power generation and industrial energy systems requiring high-temperature heat.
Power-to-Heat & Short-Term Storage
Turning electricity into flexible heat
Electric boilers and heat pumps can convert surplus or low-cost electricity into heat, which can then be stored in accumulator tanks.
This provides fast-response flexibility and is well suited to peak shaving and short-term optimization. It is not, however, seasonal storage on its own.
Best suited for: Short-term flexibility, peak shaving and as a complement to seasonal thermal storage.
Cold Thermal Energy Storage
Storing cooling for when it is needed
Cold can be stored using technologies such as ice or snow storage and used later during periods of high cooling demand.
These systems can provide highly efficient cooling and are particularly useful for reducing summer cooling peaks.
Best suited for: District cooling, hospitals, commercial buildings and other facilities with significant cooling demand.
Combining technologies
Thermal storage technologies should not necessarily be viewed as competing alternatives.
A future district energy system may combine seasonal storage, ATES or BTES, heat pumps, Power-to-Heat, short-term storage and recovered waste heat to create the most efficient overall solution.
The objective is not to select a technology in isolation, it is to optimize the complete energy system.
Finding the right solution
Every district heating and cooling system is different.
We evaluate energy flows, seasonal demand, available waste heat, temperature levels, geology, land availability and existing infrastructure to identify the most suitable storage concept.
Technology, expertise and collaboration ,applied to the energy system as a whole.
THERMOX 