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Monday, 21 October 2019

New adsorbent material for more efficient cooling systems running on light

The ICN2 Supramolecular NanoChemistry and Materials group, led by ICREA Prof. Daniel Maspoch, has proven that efficient and sustainable chilling systems could be built thanks to a new bidimensional material of the covalent-organic frameworks class (called TpPa-1). They would be based on an absorption/desorption cooling cycle and would run on solar energy. This research has been published on Advanced Energy Materials.

Cooling systems – such as air conditioning devices – contribute strongly to the global fuel consumption and greenhouse gas emissions. Therefore, it is necessary to develop technologies able to take advantage of renewable energy or waste heat, which is the byproduct of other processes.

Conventional and widespread cooling systems are based on the compression refrigeration cycle, in which energy has to be applied to increase the pressure of the fluid flowing in the device. The chilling effect is produced when, in a following step, the fluid rapidly expands again. Adsorption-based cooling systems are promising alternatives, since they require less energy and emit less CO2. In them, the compression/decompression cycle is replaced by a reversible adsorption/desorption one. Energy is in turn required for the absorbent material to release the fluid – previously soaked up--, but solar radiation or waste heat are sufficient for this purpose.

The efficiency of these systems depend strongly on the specific adsorbent and adsorbate (i.e. the refrigerant fluid) employed. Water can be used as the fluid and porous materials such as silica, activated carbon, and zeolites are currently applied as sorbents in commercially available adsorption chillers and heat pumps. These materials, though, provide poor efficiency, hence other options are being investigated.

Covalent Organic Frameworks (COFs) are a class of porous and crystalline materials that have been proposed as possible sorbents, thanks to their remarkable water uptake and their chemical stability to water and acid. Researchers of the ICN2 Supramolecular NanoChemistry and Materials group, led by ICREA Prof. Daniel Maspoch, have proven for the first time that one of these new materials can indeed be employed as sorbent in adsorption-based cooling processes. Specifically, they studied the TpPa-1, which is a bidimensional imine-based COF crystal.

As described in a paper recently published on Advanced Energy Materials, the authors of this study tested the cooling process mimicking standard operating conditions of a cogeneration plant that works at a typical temperature of 65  ͦC. It showed good performance and efficiency. It was also demonstrated that visible light can be used to drive the cooling system, since it is sufficient to make the TpPa-1 crystal release the adsorbed water.

Other porous materials, of the metal-organic frameworks (MOFs) class, had actually been tested before in absorbed-based cooling systems and had produced good results. Nevertheless, their long-term stability in water-based applications was a main concern. The TpPa-1, on the contrary, can guarantee not only a comparable efficiency, but also improved stability and durability.

 

Article Reference:

Javier Pérez‐Carvajal, Gerard Boix, Inhar Imaz, and Daniel Maspoch, The Imine‐Based COF TpPa‐1 as an Efficient Cooling Adsorbent That Can Be Regenerated by Heat or Light, Adv. Energy Materials, 03 Sept. 2019;

https://doi.org/10.1002/aenm.201901535