By Eamonn Ryan
South Korean researchers have developed a prototype cooling system capable of using waste heat at temperatures as low as 40°C – potentially opening a new route for recovering low-grade heat from factories and data centres.
If that heat can be converted into useful cooling, it creates the possibility of a more integrated energy system.
Frimufilms | Magnific.com
What if some of the heat currently rejected into the atmosphere could instead be used to produce cooling? That is the proposition behind a new chemical adsorption heat pump developed by researchers at the Korea Institute of Machinery and Materials (KIMM), working with Chung-Ang University.
The system has demonstrated cooling using waste heat at approximately 40°C, a significant development because conventional adsorption cooling systems generally require substantially higher-temperature heat sources. KIMM says traditional systems typically require heat above 70°C.
The research team has produced a 10kW-class prototype, which is currently undergoing demonstration testing. The development was reported by Korea’s National Research Council of Science and Technology in August and subsequently highlighted by HVAC&R industry publications.
Using heat instead of electricity
Unlike conventional vapour-compression air-conditioning systems, where electrical energy drives a compressor, the KIMM system uses heat as the energy input to the cooling process. At its core is a chemical adsorption heat pump. Heat is supplied to an adsorption bed, causing refrigerant to be released and allowing the refrigeration cycle to operate. In this case, the system is designed to extract useful cooling from a relatively low-temperature waste-heat source.
This could be particularly interesting for facilities where heat is continuously generated but is too cool to be economically useful for conventional heat recovery.
Factories are an obvious application, but KIMM specifically identifies data centres as another potential source. These facilities generate enormous quantities of low-grade heat as they reject the thermal energy produced by IT equipment.
Instead of simply rejecting all of that heat through cooling towers, dry coolers or other heat-rejection equipment, a system such as this could potentially recover a portion of it and use it to assist with the cooling requirement.
A different type of compressor
The project also incorporates an electrochemical compressor developed by the Chung-Ang University research team. Unlike a conventional mechanical compressor, the electrochemical compressor has no moving parts, meaning that it can operate with very low noise and vibration. KIMM says this could make the technology suitable for applications where noise is a concern, including hospitals, schools and residential buildings.
The researchers have also developed a large-area ammonia compressor as part of the work. Ammonia is a natural refrigerant widely used in industrial refrigeration, although its application in new types of cooling equipment brings its own requirements for system design, safety and refrigerant management.
Improving the adsorption bed
Another claimed advance is the performance of the system’s adsorption bed, which is the component at the heart of the thermally driven cooling process. KIMM reports a specific cooling power of 346.5W/kg, which it says is more than twice the performance of comparable international technologies. The figure is a laboratory/research performance metric rather than evidence that a commercial system is ready for widespread deployment.
That distinction is important. The current development is a 10kW-class prototype, and the researchers are continuing demonstration work before moving towards field applications and commercialisation.
Why it matters to HVAC&R
The significance of the research is less about replacing conventional chillers tomorrow and more about expanding the range of heat sources that can potentially be integrated into cooling systems. Low-grade heat is abundant. Industrial processes, data centres and other facilities continually produce thermal energy that may be difficult to reuse because of its relatively low temperature.
If that heat can be converted into useful cooling, it creates the possibility of a more integrated energy system in which waste heat becomes part of the cooling solution rather than simply another load that has to be rejected.
For HVAC designers, this raises interesting questions about how future buildings and industrial facilities could be designed around heat recovery. Rather than considering cooling, heating and heat rejection as separate systems, there may be increasing opportunities to link them together.
The technology is not yet at that stage. The KIMM team is currently conducting demonstration tests on its 10kW-class prototype, with further research planned to advance the technology towards field demonstration.
Nevertheless, the development illustrates an increasingly important direction for HVAC&R: using energy that would otherwise be wasted to reduce the energy required for cooling. As cooling demand continues to rise, finding ways to make better use of every available energy source could become just as important as improving the efficiency of the cooling equipment itself.
