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Adsorption Cooling from Low Temperature Waste Heat

Updated: Aug 18, 2022

The Issue

A lot of waste heat from industrial processes, power plants and burning of biomass goes to... welll... waste. This is a shame, as this waste heat can be turned into free cooling. Even low grade waste heat down to about 60 degrees Celsius can be converted into cooling through the process of adsorption.

Our Approach

At the University of Kuala Lumpur, Gombak campus, we installed an adsorption chiller from the German company Invensor, a project funded by the German government through the RoCABT program. This small 10 kW cooling adsorption machine was meant for demonstration and research purposes for the university staff and students. For ease of installation, the adsorption chiller installation was done inside a shipping container, which would make it easy to move it to new locations in the future.

The adsorption chiller system consists of three water borne loops:

  • HOT WATER LOOP Tapping of waste heat in the range 45 - 100 degrees Celsius

  • CHILLED WATER LOOP Producing chilled water in the range 10 - 25 degrees Celsius

  • RECOOLING WATER LOOP: Producing low temperature waste heat in the range of 20 - 37 degrees Celsius

The 10 degree Celsius chilled water can be used for cooling buildings, for example, for air-conditioning and/or for floor slab cooling. A simplified diagram and the technical specification for the Invensor LTC 10 e adsorption chiller are shown below at nominal operating conditions:

The diagram shows that adsorption chiller removes heat, both from the free heat source at 72 degrees Celsius (hot water loop) and from the object being cooled at 10 degrees Celsius (chilled water loop). To ensure preservation of energy, an equivalent amount of energy is ejected from the adsorption chiller, which is done in the recooling water loop at a low temperature of 31.3 degrees Celsius. For a short video explanation of the adsorption cooling process, click here: The illustration below is taken from the this video:

For the actual installation, the heat source was for simplicity a 18 kW diesel water heater placed on the roof of the container. The recooling loop was a evaporative air cooler placed outdoors on the ground. And the chilled water was pumped through a car radiator with forced ventilation from a standing fan. See photos and as-built installation diagram below:

Our Findings

Three energy meter were installed on each of the water loops for monitoring of the following parameters:

  • Energy flow (kW)

  • Water flow (m3/hour)

  • Inlet temperature (degC)

  • Outlet temperature (degC)

The three Kamstrup energy meters can be see below:

The installation worked. The heat from the diesel water heater was indeed turned into cooling through the process of adsorption cooling. The snapshot of the above meter readings show that 1.6 kW of cooling is produced from 8.6 kW of waste heat.

Unfortunately, due to time constraints no detailed performance measurements were done of the system before handing it over to the university. According to the Invensor brochure, the coefficient of performance (COP) of this small adsorption chiller for nominal operation is 0.52, but can go up to maximum 0.75.

The adsorption chiller is currently being used by a research team that obtain the free heat source for solar thermal collectors (July 2022). Stay posted for their research results, which will include the coefficient of performance figures of this adsorption chiller.


Acknowledgement: A big thank you to Martin Zuckermaier for a great collaboration on this project, which was his brainchild. Also thank you to UniKL for being a willing partner for this research demonstration project installation.


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