Adsorption Chillers: creating cooling from excess heat
What does and adsorption chiller do?
Adsorption Chillers produce 8 to 10 C cooling from low grade, 60 to 95 C heat source.
How does an Adsorption chiller work?
The adsorption chiller uses water, yes simple clean H2O, as the refrigerant. The refrigerant water is boiled under a vacuum at 3 to 7 C, creating the cooling effect. The water vapour produced is adsorbed onto the surface of silica gel. Yes, the silica gel that you find in those little sachets keeping foods and goods dry. When the silica gel surface is fully loaded with water, it is dried using the low grade heat 60 to 95 C with the recovered water returned to start the cycle again. This process is simple and uses safe materials.
How much energy does an Adsorption Chiller use and create?
This question has two aspects to the answer, electrical energy and the conversion efficiency of heat to cooling.
Adsorption chillers convert the heat to cooling with an electrical coefficient of performance, or COP, of around 10. So, 1 KW of electrical energy is used to create 10 KW of cooling, which is 3 to 5 times higher than some conventional refrigeration systems. This is extremely energy efficient and reduces their owners electrical cooling costs.
The proportion of thermal heat energy converted to cooling depends on several factors such as the temperature of the heat source, but as a rule of thumb, the cooling is around 65% of the heating. The thermal COP is 0.65. Adsorption chillers are remarkably efficient, producing cooling with a minimal of power and low grade heat; using the safe refrigerant, water.
Who can use Adsorption Chillers?
Operations that have access to heat and require cooling. Common heat examples include:
1. Combined Heat and Power Generators and Fuel Cells
2. Refrigeration compressors
3. Compressed air systems
4. Solar Thermal Hot Water collectors
5. Geothermal sources
6. Waste Process heat from industry
What are suitable applications for Adsorption Chillers?
- Dairy Farms – which require power, heating and cooling every day of the year.
- Commercial Buildings – with power and heating useful for winter and power and cooling attractive for summer conditions
- Meat Works – with combined heat and power plant. Power used for plant and equipment, hot water for washing, heat recover available from refrigeration systems and cooling useful for assisting the refrigeration system.
If you require power, heat and/or cooling then an Adsorption Chiller may suit your application.
Can Adsorption Chilling assist with lower temperature cooling applications?
Yes. While adsorption chilling is limited by the boiling temperature of water under vacuum and therefore limited to 8 to 10 C, it can be combined with a refrigeration system via a heat exchanger to provide a hybrid solution with traditional refrigeration temperatures.