Sorption cooling

Sorption cooling is a technology that uses heat to produce cold. ECN is working in particular on solid sorption cooling. The working principle is based on reversible (chemical) reactions of a vapour with a solid. A general description of this principle is described elsewhere.

In this case the system uses silica gel as the solid and water as the vapour. With this system it is possible to generate cooling of about 5-10ºC from (waste) heat of 60-90ºC. Cooling is produced by evaporation of water. Water vapour is absorbed by the hygroscopic silica gel. The (waste) heat is necessary to regenerate the silica. During this phase the water vapour is desorbed from the salt.  

ECN is working both on stationary and mobile applications of these systems.

The picture below shows the total test installation. This installation is designed, build, and tested at ECN (left picture) and achieves the expected performance, namely generate 5 kW cooling from 8 kW of heat. After the initial tests at ECN, the installation is moved to Italy. The cooler is connected at a small gas engine at the Fiat Research Centre to demonstrate its performance in the intended application (right picture). One of the most important objectives of this development is to obtain a system that has a high power density. This enables compact systems. This can be achieved by improving the heat and mass transport through the silica gel. The rate of release and uptake of water vapour by silica gel can be improved by increasing the heating and cooling rate of the silica gel. A larger cooling effect can then be obtained by a smaller quantity of silica gel.  

Mobile application

The second development in this category relates to the development of a sorption cooler for the transport sector. Air-conditioning is increasingly being used within this sector. This leads to increased fuel use and emissions. Objective here is to develop a sorption cooler that is driven by the waste heat of the engine. This reduces fuel use and emissions. Obviously, the requirements with respect to compactness and weight are even more stringent than for the above-mentioned stationary application.  

The development will consist of two phases: research and development of a lab scale prototype, followed by the development of two demo’s that will be incorporated and tested in a passenger car and a truck.  

The time lag between the need for cold and the availability of heat from the engine forms, in addition to compactness and weight, the greatest challenge for this development. It will take a while for the engine to heat up after a cold start just at the moment the need for cooling is the largest. Research into heat and cold storage will therefore be an important part of the development of the system.