Research

LOW-COST SOLAR THERMAL COLLECTORS FOR ABSORPTION REFRIGERATION SYSTEMS
Cooling With The Sun's Help

Team

Howard Schmidt, Ph.D., (co-PI) Chemical and Biomolecular Engineering Department, Rice University
Kyriacos Zygourakis, Ph.D., (co-PI) Chemical and Biomolecular Engineering Department, Rice University
Alejandro J. Garcia-Cuellar, Ph.D., (co-PI) Solar Energy and Thermal-Fluid Sciences, Tecnologico de Monterrey

Dr. Howard Schmidt

Dr. Kyriakos Zygourakis

Dr. Alejandro J. Garcia Cuellar

North America, with only 6% of the worlds’ population, accounts for nearly 40% of the world's refrigeration market.  About 18% of US electricity consumption is used for air conditioning.  Energy consumption for air conditioning is naturally proportionately higher in the American South and Southwest, due to higher insolation (solar energy flux).  The same solar insolation that creates the need for air conditioning could also provide a wonderfully renewable energy source to power absorption-based refrigeration systems. 

Indeed, this was demonstrated at full-scale (Fig. 1A) by Prof. Jose Manrique-Valadez and co-workers at Tecnologico de Monterrey in Monterrey, Mexico over a decade ago.  They were among the first to realize that simple thermally-driven refrigeration cycles, e.g. ammonia dilution, could be used in place of the nearly ubiquitous Freon-compression cycle.  Since the ammonia-dilution cycle only needs a heat source of about 150C, evacuated tube solar collectors (ETSC, Fig. 1B) are used as the primary energy source.  The evacuated tubes used in the demo system can reach a peak temperature of 300C, even without concentrating mirrors or active pointing devices.    Cooling is performed using a commercially available Servall ammonia refrigeration unit after retrofitting with a custom generator (ammonia separator; white component in Fig 1C).  Comfortable temperatures are achieved with roughly 80% reduction in electricity consumption (electricity is still used for fans and pumps).

While technically successful and environmentally appealing, this approach has not yet entered wide-spread use, however, due primarily to the cost of the evacuated tube solar collectors.  These cost today about $1K - $2K per m2, and 10-20 m2 are needed for a typical American residence.

The objective of this project is therefore to develop a simple method of realizing suitable solar collectors at greatly reduced cost (~3-10x).  Two primary approaches will be explored: large area vacuum envelopes, and translucent nanostructured insulation.  Candidate designs will be modeled using finite element methods (e.g. COMSOL Multiphysics) and production costs estimated.  Promising approaches will be fabricated at modest scale (~1 square foot panels) at Rice, and then these prototypes characterized and tested in Monterrey.

Fig. 1A All Solar Demonstration House, Monterrey, Mexico

Fig. 1B Evacuated Tube Solar Collectors

Fig. 1C Ammonia Absorption Refrigeration

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