A concrete-based thermal battery has been developed that can store heat previously discarded during the cooling process at datacentres and reuse it. The technology collects waste heat generated by servers and supplies it to cooling facilities and industrial processes. Attention is focused on whether it can raise datacentre energy efficiency and broaden the use of waste heat.

On Oct. 14, IT outlet TechRadar reported that a research team at Lehigh University in the United States built a thermal storage system that can store heat generated by datacentre computing equipment and draw on it when needed.

The key is to collect heat produced during cooling in a separate storage unit instead of releasing it outside immediately, and then use it in line with demand. Datacentres generate varying amounts of heat depending on server loads, while actual demand for thermal energy may not coincide with when it is produced. The heat battery is designed to reduce that time gap and use waste heat more efficiently.

The prototype has a thermal storage capacity of 150 kWh. In tests, it withstood temperatures of up to 500 degrees. Its energy efficiency exceeded 70 percent after one full charge and discharge cycle. The result shows that a substantial portion of stored thermal energy can be recovered for reuse.

The system combines a specially designed cement-based material with thermosyphons. The thermosyphons rapidly move heat within the storage unit. The researchers described the approach, which combines different heat storage mechanisms within a concrete structure, as a "hybrid array". It is designed to deliver heat quickly while maintaining a relatively stable temperature so stored energy can be drawn out as needed.

It has 2 charging methods. It can directly recover waste heat generated by datacentre servers. It also supports heating the storage unit using electricity. That allows flexible operation, such as storing heat when waste heat is produced and using electric heating depending on power supply conditions.

Attention is also focused on the ability to raise the temperature of heat recovered from a datacentre to a range of 120 to 220 degrees for use. Heat at that temperature can be supplied to absorption chillers, which could help reduce reliance on electric refrigeration equipment. Stored heat can also be used for drying processes, district heating and industrial heat sources.

It is also significant that heat discarded during datacentre cooling can be linked to external energy demand. Previously, heat removed to keep servers operating reliably was often released into the atmosphere. With a thermal storage system, it can be supplied to nearby industrial facilities or district heating. Actual utilisation, however, may vary depending on distance to heat demand sites, the cost of building infrastructure such as piping, and required temperature conditions.

Potential applications are not limited to cooling and heating. The researchers also proposed supplying stored heat to low-temperature Rankine cycle equipment for power generation. They also expect the scale of deployment can be expanded from kilowatt-class to megawatt-class facilities. They see possible applications in high-temperature solar thermal systems, reducing industrial emissions and producing electricity in line with demand.

Separating when heat is stored from when it is used could also benefit datacentre operations. Server loads and cooling demand vary by time of day, but a heat battery can store waste heat even if it cannot be used immediately and supply it when needed. That could raise the utilisation of thermal energy and allow more flexible energy operations across the facility, the researchers said.

Development is moving beyond an early research stage into follow-on commercialisation. The technology received some U.S. federal energy-related funding and has now been licensed to a private energy company. Further development is expected that takes into account integration with existing energy infrastructure.

Even so, further verification is needed to determine whether performance seen in the prototype can be replicated in large-scale datacentres. That is because losses during heat storage and recovery, facility construction costs and long-term operational stability must be confirmed.

As the spread of artificial intelligence increases datacentre power consumption and cooling burdens, technologies that store waste heat for reuse are emerging as one option to improve energy efficiency. If concrete-based heat batteries expand into commercial facilities, they could help build an energy circulation structure that uses heat previously discarded by datacentres for cooling, heating and industrial processes.