Mobile thermal energy storage (M-TES) is a technology adapted to the transport of heat intended for residential or tertiary heating, or even for certain industries. It is an alternative to conventional heating solutions, such as heating networks or individual boilers. This alternative is interesting if the construction of a heat pipe is not profitable or possible and particularly if the production and consumption of heat are irregular. It makes it possible to avoid the investment costs associated with the construction of boiler rooms, but above all to reduce (or control) GHG emissions at the point of use of heat.
Figure 1: Principle of an M-TES cycle (Lahoud et al. 2025)
The heat sources to be prioritized are the waste heat from industrial processes and that from electrical cogeneration: moderate heats (< 150°C) and difficult to valorize near their production. M-TES containers are designed to be suitable for transport and are generally transported by road (Figure 1). The electrification of road transport would significantly extend the Range of this heat (>45km), as the use of diesel does not make the process profitable ecologically speaking over long distances.
In practice, an M-TES system consists of 4 components:
- A thermal energy storage unit: tank filled with a material capable of storing significant quantities of thermal energy, and equipped with a heat exchanger.
- A control and measurement system: monitoring the state of charge/discharge of the storage and its operation.
- A transport system.
- Connection points at the point of charge (at the heat source) and at the point of discharge of the storage (at the level of the heat consumer).
The key element in this technology is the heat storage material. Many technologies are being studied with generally low levels of maturity. Only some PCM (phase change material) technologies are commercially available but are still far from being widespread. PCMs are materials that can store a significant portion of latent heat during their phase change in addition to their sensitive heat storage capacity. This property gives them a significant heat storage capacity.
Figure 2: Classification of Phase Change Materials (PCM) (Mika et al 2025)
Commercialized PCM solutions, such as that of Enetech, offer 24-ton tanks that can store 7GJ (2 MWh) that can be released at a power of 150 kW. The energy density is thus slightly better (0.3 MJ/kg) than that of water but could increase even more in the coming years. These systems would become competitive from a storage capacity of 0.4 MJ/kg, and many families of PCMs have yet to be explored (figure 2) and represent an interest not only for M-TES but for thermal storage solutions in general, particularly for buildings (inertia, insulation) and solar thermal energy.
In addition to PCMs, other technologies that are still not very mature present an interesting potential for M-TES, particularly thermochemical storage technologies by adsorption/desorption or by chemical reaction, and can achieve, on the one hand, a significant energy density but also better stability (allowing heat to be stored over longer periods of time).
M-TES are particularly interesting for countries with cold climates. They are only really so today if heating networks are not already generalized and if the production of fatal or decarbonized heat affects the territory. This may be the case in France, Germany and Poland. Beyond that, the deployment of heavy electric vehicles and the possible deployment of SMR within 10 years could fuel synergies with this paradigm shift in district heating.