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
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Dr. Kyriakos Zygourakis
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 Dr. Alejandro J. Garcia Cuellar
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Project BackgroundNorth 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
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Fig. 1B Evacuated Tube Solar Collectors
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 Fig. 1C Ammonia Absorption Refrigeration
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