Don’t Lose Your Cool: Thermal Storage for Smart Heating and Cooling

Heating and cooling are among the largest and most persistent forms of energy consumption. In the European Union, they account for approximately 40% of final energy use in buildings, making them a formidable barrier to achieving meaningful reductions in greenhouse gas emissions. With rising energy prices and populations, and shifting climate patterns, it is becoming increasingly apparent that more regenerative, circular approaches are needed to improve efficiency and sustain demand.

At its core, thermal storage involves capturing heat or cold when it is available, or cheaper to produce, and releasing it later when needed. The traditional linear energy system operates on a wasteful model: energy is generated, consumed, and ultimately discarded as waste heat. A circular‑economy approach, by contrast, seeks to keep resources in use for as long as possible, capturing and reusing thermal energy to reduce both primary energy demand and emissions.

How thermal storage fits with new regulations

The European Union has already begun to recognise the transformative potential of energy efficiency within broader climate policy. The revised Energy Efficiency Directive (EU/2023/1791), published in 2023, establishes “energy efficiency first” as a legal principle underpinning policy decisions. That is, the question to consider is whether to improve the efficiency of existing energy systems first, before investing in entirely new energy infrastructure. The Directive also sets a binding target to reduce final energy consumption by 11.7% by 2030, compared to 2020 projections, and obliges member states to integrate efficiency measures across sectors including heating and cooling.

The 2023 revision of the Energy Efficiency Directive not only established binding energy‑consumption targets but also placed a renewed emphasis on heating and cooling planning. For example, cities with populations exceeding 45,000 must now develop local heating and cooling plans to support the transition to decarbonised thermal systems by 2050. Such requirements create significant opportunities to integrate thermal storage into public‑sector buildings, which can set precedents for broader market adoption. Thermal storage innovations provide effective means for compliance with new regulation, shifting demand away from peak periods and integrating renewable sources more effectively.

Companies leading the way

One of the most promising domains within thermal storage is the use of phase change materials (PCMs). These materials store energy through transitions between solid and liquid phases, and absorb or release heat at specific temperatures. PCMs enable a form of thermal buffering that can smooth out temperature fluctuations, reducing the burden on heating and cooling equipment. Empirical studies have shown that integrating PCMs into heating, ventilation and air conditioning (HVAC) systems can achieve energy savings of 10 to 30% and reduce peak loads by 20 to 50%. This makes them a compelling option for nearly zero‑energy building strategies and broader decarbonisation efforts.

Among the companies advancing this field, PhaseStor stands out for its development of bio‑based PCMs derived from plant oils and fatty acids. These materials offer an environmentally sensitive alternative to conventional paraffin‑based PCMs, many of which rely on fossil fuel feedstocks. By creating PCMs from renewable, biodegradable sources, PhaseStor reduces the carbon footprint associated with manufacturing and contributes to a more circular materials economy. Bio‑based PCMs can be integrated into building envelopes, thermal batteries, and heat‑recovery systems, helping to capture and store heat that would otherwise be wasted.

Phase Energy offers a complementary approach, combining organic wax PCMs with inorganic salt hydrates to create a versatile suite of thermal storage solutions. Salt hydrates, in particular, offer high energy density and fast thermal response at relatively low cost, making them well suited for both residential and industrial applications. By pairing these with organic materials, often selected for their thermal stability and safety, Phase Energy provides systems capable of operating across a wide range of temperatures. With cooling demand projected to rise as heatwaves become more frequent, such innovations will likely become central to climate‑adaptation strategies as well as decarbonisation.

One of the most groundbreaking developments in thermal storage comes from Barocal, a company pioneering the use of barocaloric materials - solid materials that undergo temperature changes when pressure is applied. Unlike conventional PCMs, which rely on melting or freezing processes, barocaloric materials remain solid at all times, undergoing phase transitions that absorb or release heat in response to changes in pressure. This solid‑state approach avoids the use of refrigerants, many of which have associated environmental hazards, and offers the potential for compact, high‑energy‑density storage systems. The environmental benefits of eliminating refrigerants are significant, particularly as EU regulations tighten around their use and phase‑out schedules.

A radically different approach to cooling is adopted by Unitech Synergies. Their TOVENVOR system provides refrigerant‑free cooling and energy‑recovery technology while simultaneously recovering thermal energy that would otherwise be wasted. Using a toroidal venturi vacuum process, TOVENVOR delivers cooling and converts heat into electricity that can be used to offset its own energy demand. Unlike conventional cooling systems which reject heat to the environment, this closed‑loop approach treats heat as a recoverable resource. By capturing and reusing this energy, the technology aims to improve overall efficiency while reducing peak electricity demand. Additionally, the system does not use refrigerants at all, thereby eliminating concerns associated with refrigerant leaks and their environmental impact. By combining cooling with energy recovery, Unitech demonstrates how next-generation cooling technologies can improve efficiency while supporting increasingly stringent sustainability objectives.

Conclusion

The cumulative effect of these technical and policy developments is a growing recognition that thermal storage can serve as a cornerstone of the future energy system. By storing heat and cold more intelligently, buildings become more efficient and resilient and energy flows become more circular. Waste heat can be captured from industrial and commercial buildings; stored in bio‑based, inorganic, or solid‑state materials; and redistributed when demand arises. At the grid level, thermal storage can help integrate variable renewables by shifting thermal loads away from peak times, reducing strain on electricity networks and lowering costs for consumers.

As the EU advances toward its 2030 and 2050 climate objectives, bringing thermal storage technologies into buildings, districts, and industries becomes not only desirable but necessary. Innovative companies like PhaseStor, Phase Energy, and Barocal are already showing what this future could look like, offering a more regenerative and efficient heating and cooling model. Turning thermal energy from a linear, waste‑heavy resource into a circular, optimised system represents one of the most promising pathways for reducing emissions and supporting the ecological transition for households and communities across Europe and the world.