Sorption Energy Seeking to Commercialize Waste Heat-Driven Adsorption Heat Pump Technology for Vehicle Air Conditioning

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Although the heating and cooling provided by a single generator is discontinuous, it can be made continuous by operating two or more generators out of phase.

While the basic concepts behind adsorption heat pumps are well known, the challenge has been in the required size of the systems; the basic adsorption cycle has low efficiency, which requires methods for recovery of heat between adsorbent beds, and the inherently low thermal conductivity of available adsorbent materials results in low power densities and machines of high capital cost.

The University of Warwick researchers developed an adsorption systems design that significantly shrinks these devices making them small and light enough for use in both domestic heating and automotive air conditioning.

In a paper published in January in the journal Heat Transfer Engineering, Critoph et al. describe a prototype compact sorption generator using an activated-carbon/ammonia pair based on a plate heat exchanger concept.

The heat exchanger uses nickel brazed shims and spacers to create adsorbent layers only 4 mm thick between pairs of liquid flow channels of very low thermal mass. The prototype sorption generator manufactured has been evaluated under the European Union (EU) car air-conditioning testing conditions.

While driven with waste heat from the engine coolant water (at 90 °C), a pair of the current prototype generators (loaded with about 1 kg carbon in each of two beds) has produced an average cooling power of 1.6 kW with 2-kW peaks.

Sorption Energy’s technology will work well in current vehicles with diesel or gasoline engines, and is expected to work with hybrid electric vehicles incorporating internal combustion engines.

This technology is expected to cost no more than the current systems which are driven by a compressor. Several components are common, but the compressor will be replaced, and the additional components provided by Sorption Energy can be manufactured at an acceptable cost.

(A hat-tip to John!)

Resources

• Robert E. Critoph; Steven J. Metcalf; Zacharie Tamainot-Telto (2010) Proof of Concept Car Adsorption Air-Conditioning System Using a Compact Sorption Reactor. Heat Transfer Engineering, Volume 31, Issue 11 pages 950 – 956 doi: 10.1080/01457631003604459

• M A Lambert, B J Jones (2006) Automotive Adsorption Air Conditioner Powered by Exhaust Heat. Part 1: Conceptual and Embodiment Design. Proc. IMechE, Part D: J. Automobile Engineering. Volume 220, Number 7 doi: 10.1243/09544070JAUTO221