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Scientists’ Corner: Thermally activated cooling technologies

Scientists’ Corner: Thermally activated cooling technologies

The methods for producing cold utilizing heat source are called thermally activated cooling. They include adsorptionabsorption and desiccant cooling (solid desiccant cooling and liquid desiccant cooling).

Absorption and adsorption are both used to provide thermal compression of refrigerant instead of mechanical compression. Some energy demand for refrigeration is thus shifted from electrical to thermal energy, and primary energy consumption is also reduced. Regeneration of sorption material can be achieved by using a low-grade heat source.

Absorption is the process in which a substance in one phase is incorporated into another substance of a different phase. Adsorption refers to the use of a solid for adhering ions and molecules of another substance onto its surface. The main differences between absorption and adsorption are in the nature of the sorbent (liquid/solid) and the sorption cycle (continuous/batch). 

Desiccant cooling is another thermally activated technology; it works on the principle of incorporating desiccant dehumidification and the cooling unit, and its unique merit is that the sensible and latent heat can be processed separately. Desiccant cooling can be divided into solid desiccant and liquid desiccant cooling.

Within BRICKER, Spanish partner CARTIF aims to select the most appropriate chillers taking into account the heat source levels and the particular boundary and climate conditions in each demo site: cooling demand of the demonstration buildings, the outlet condensation temperature of the cogeneration units, the interaction with solar fields, biomass plants and the existing conventional heat production systems in the buildings.

Two chiller units will be installed in the Spanish (Administrative building) and Turkish (Hospital) demo sites. These chiller units will be selected with the idea to address the concept of trigeneration or CCHP (Combined Cooling, Heating and Power) being the simultaneous production of electricity, heating and/or cooling from one primary fuel. For the Spanish demo case, the technology selected is adsorption which allows using the water condensation of the ORC at low temperature (~ 70 ºC) to cover the cooling needs of the administrative building. On the other hand, for the Turkish demo site, there is still an open point regarding the technology to be used, being two the most feasible possibilities at this moment, adsorption in the same way than in the Spanish demo case, or a double effect absorption unit using directly as heat source, the heat provided by the solar system (through a heat exchanger oil-super heat water or steam) and an auxiliary gas boiler obtaining a higher efficiency.