7. MATERIALS FOR ADVANCED COOLING APPLICATIONS

 

In U.S. residential and commercial buildings, space cooling (air conditioners) used about 3.4 Quads of primary energy in 2004, and refrigeration and freezers used about 2.3 Quads more.  In the industrial sector, process cooling used about 0.7 Quads.  And in the transport sector, air conditioning is a large load that constrains down-sizing of hybrid vehicle engines; overall, A/C accounts for roughly one-fifth of the power required by a mid-sized sedan traveling at 60 mph on a hot summer day.  Combined, these various cooling requirements total roughly 7 Quads of primary energy per year.

 

Another problem concerns the adverse environmental impact of the refrigerant gas used in the mechanical vapor compression cycles of conventional air conditioners and refrigerators.  Although the refrigerant gases used today are considered safe for the ozone layer (per the Montreal Protocol), they are strong greenhouse gases.  Per molecule, the refrigerant R-134a used in vehicles, for example, has 1300 times the direct Global Warming Potential of carbon dioxide over a 100-year period.  Current vehicular air conditioners leak 10 to 70 grams of R134-a year; the European Union (EU) requires that new model cars introduced in 2011, and all new cars by 2017, not use R134-a.  There are also large refrigerant losses from residential and commercial air conditioners and refrigerators.  According to the Intergovernmental Panel on Climate Change (IPCC) overall, these and other halocarbons contribute about 0.34 W/m2 of radiative forcing, as of 2005, which is about one-fifth of that due to CO2 alone, at 1.66 W/m2.

 

The Department of Energy is seeking the development of advanced technologies for space cooling in buildings and vehicles, and for refrigeration in residential, commercial, and industrial applications.  The new cooling technologies not only should be more energy efficient than current technologies but also should not use refrigerants that contribute to global warming.  New technologies that might be successfully developed for advanced cooling applications include, but are not limited to, ThermoElectrics (TE), MagnetoCalorics, ElectroCalorics, and ThermoTunneling.  Important contributory technologies also include advanced heat exchangers and advanced dehumidification technologies.  These technologies also could allow systems to be reconfigured in advantageous ways.  For example, vehicles cooling systems could be placed where most convenient, instead of being constrained to a position for belt-driven mechanical compression.  Some of these technologies, particularly ThermoElectrics (TE), have long been used for cooling applications, but commercially available units typically have efficiencies of just one-fifth to one-tenth that of mechanical vapor compression cycles.  Advances in TE materials offer the potential for raising these efficiencies significantly above those of conventional mechanical systems.

 

Approaches of interest should significantly reduce energy consumption compared to conventional mechanical vapor compression cycles and eliminate the use of refrigerants that provide a net contribution to global warming, while achieving costs at or below current levels for comparable systems.  In addition, the new technologies should be lighter, more compact, and more durable than conventional refrigeration technologies.  Grant applications must:  (1) include a review of the state-of-the-art for both the technology application being targeted and the proposed technology; (2) address the potential public benefits that the proposed technology would provide; and (3) address the ease of implementation of the new technology.  Phase I should include a preliminary design, along with a measurement of refrigeration cell performance.  The measurement method should be described and should be within the state of the art; however, as such measurements may be extremely difficult (as, for example, with nanoscale thermoelectrics), a test may be devised to verify the amount of cooling for a given level of power supplied. 

 

Grant applications are sought only in the following topics.

 

 

a. Buildings Refrigeration and Air Conditioning—Conventional air conditioners, heat pumps and refrigerators, which collectively use 5.3 quads of energy in the U.S., achieve cooling through a mechanical vapor compression cycle (VCC).  Although the efficiency of the best VCC systems is on the order of 40–45% of Carnot efficiency, these efficiency numbers may be approaching asymptotic values; hence, the opportunity for further improvement could be limited.  Continuing progress in materials and manufacturing techniques may make advanced cooling technologies more attractive for building applications.  Grant applications are sought to develop improved materials and manufacturing techniques that have the potential to provide improved cost-vs-performance compared to conventional VCC technologies.  Proposed concepts may address a particular segment of this broad application area (e.g., commercial refrigeration).  In addition, technologies of interest must:  (1) have the potential for very high reliability; (2) be amenable to installation without reliance on skill sets not commonly available in most communities; and (3) offer significantly improved efficiency while avoiding refrigerants with climate change impacts. 

 

Questions – contact Sam Baldwin (Sam.Baldwin@ee.doe.gov)

 

 

b. Vehicular Air Conditioning—Grant applications are sought to develop new vehicular air conditioning systems that not only can provide improved energy efficiency and avoid refrigerants with net greenhouse gas impacts, but also can withstand the accelerations, vibrations, and temperature excursions typically experienced in vehicle use in the U.S.  The vehicle’s Heating, Ventilation and Air Conditioning (HVAC) system should be able to provide a nominal cabin temperature less than 70oF with a worst case ambient temperature of 122oF.  Grant applications should demonstrate an understanding of the requirements of a vehicle OEM (Original Equipment Manufacturer) with respect to desired heating and cooling loads, installation space, and interface parameters for specific vehicles.  The Phase I project should include the preparation of a road map with major milestones leading to a production model of a vehicular HVAC system; this road map would form the basis for a follow on program.

 

Questions – contact Sam Baldwin (Sam.Baldwin@ee.doe.gov)

 

 

c. Industrial Process Refrigeration—Grant applications are sought for the development and application of new materials and technology systems that exploit waste or secondary heat for use in industrial process refrigeration, yet do not use refrigerants that could impact climate change.  “Industry” is taken here in the broadest sense, to cover manufacturing, food processing, and space cooling in large commercial applications.  Grant applications must demonstrate that the proposed approach will have a lower price and higher performance than current adsorption chillers or other available technologies.  

 

Questions – contact Sam Baldwin (Sam.Baldwin@ee.doe.gov)

 

 

d. Utility and Industrial Heat Exchangers—In electrical utilities and in many process industries, improved heat transfer by heat exchangers offers great potential for improving process energy efficiency.  Therefore, grant applications are sought for innovative heat exchanger materials and systems that provide significant cost-effective improvements in efficiency.  Approaches of interest include the development of improved materials of construction; improved heat transfer fluid materials, including nanostructured fluids; and improved heat exchanger design.  Grant applications must:  (1) identify and characterize a target application; (2) analyze the potential benefits of the proposed new heat exchanger technology; and (3) account for issues related to heat exchanger costs, ease of retrofit and installation, and maintenance, in order to make the innovation commercially viable.  

 

Questions – contact Sam Baldwin (Sam.Baldwin@ee.doe.gov)

 

 

References:

Thermoelectrics:

 

1        Fairbanks, J, "Thermoelectric Generators for Near-Term Automotive Applications and Beyond", Plenary  Presentation , European Thermoelectric Conference '06, Cardiff, Wales, April 10-11, 2006  (Full Text available at:  http://www1.eere.energy.gov/vehiclesandfuels/pdfs/deer_2006/session6/2006_deer_fairbanks.pdf)

 

2        Bell, Lon, "Role of Thermoelectrics in Vehicle Efficiency Increases", 11th Diesel Engine Emissions Reduction Conference, Chicago, Illinois, August 21-25, 2005 (Full text available at:  http://www1.eere.energy.gov/vehiclesandfuels/pdfs/deer_2005/session6/2005_deer_bell.pdf)

 

3        Robert F., “Semiconductor Advance May Help Reclaim Energy From ‘Lost’ Heat”, Science, 31 March 2006, V.311, p.1860 (Full text available at:  http://www.sciencemag.org/cgi/content/summary/311/5769/1860a)

 

4        Jianlin Liu, “Thermoelectric Coolers and Power Generators Using Self-assembled Ge Quantum Dot Superlattices”, University of California Energy Institute, September 2004 (Full text available at: http://repositories.cdlib.org/ucei/basic/FSE005/)

 

5        M. S. Dresselhaus, et. al., “Investigation of Low-Dimensional Thermoelectrics”, (Full text is available at:  http://www-rcf.usc.edu/~scronin/pubs/d888.pdf)

 

 

MagnetoCalorics:

 

1        K.A. Gschneider, Jr., V.K. Pecharsky, and A.O. Tsokol, “Recent developments in MagnetoCaloric Materials,” Rep. Prog. Phys, V.68 (2005) 1479-1539 (Full text available at: http://www.iop.org/EJ/abstract/0034-4885/68/6/R04/)

 

2        C. Zimm, et al., “Description and Performance of a Near-Room Temperature Magnetic Refrigerator,” Advances in Cryogenic Engineering, Editor: P. Kittel, Plenum Press, New York, 1998. (ISBN 0-3064-58071)

 

 

ElectroCalorics:

 

1        A.S. Mischenko, et al., ”Giant Electrocaloric Effect in Thin-Film PbZr0.95Ti 0.05O3,”  Science, 3 March 2006, V.311, p.1270-1271. (Full text available at: http://www.sciencemag.org/cgi/reprint/311/5765/1270.pdf)

 

 

ThermoTunneling:

 

1        M. Savin, et al., ”Efficient electronic Cooling in Heavily Doped Silicon by Quasi particle Tunneling”, Applied Physics Letters, Vol.79, N.10, pp.1471-1473. (Full text available at: http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=APPLAB000079000010001471000001&idtype=cvips&prog=normal)

 

2        Yoshikazu Hishinuma, et al., “Measurements of cooling by room-temperature thermionic emission across a nanometer gap”, Journal of Applied Physics, V.94, N.7, 1 October 2003, pp.4690-4696 (Full text available at: http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=JAPIAU000094000007004690000001&idtype=cvips&prog=normal)

 

 

Heat Exchangers: 

 

1        W.Y. Saman and S. Alizadeh, “Modeling and Performance Analysis of a Cross-Flow Type Plate Heat Exchanger for Dehumidification/Cooling”, Solar Energy, V.70, N.4, pp.361-372, 2001 (Full text is available at: http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6V50-42DP0X2-5-2G&_cdi=5772&_user=10&_orig=search&_coverDate=12%2F31%2F2001&_sk=999299995&view=c&wchp=dGLbVtb-zSkWA&md5=5ade5f8fa2848a8512e92f0f687d1769&ie=/sdarticle.pdf)

 

 

Dehumidification:

 

1        Brookhaven National Laboratory, “Independent control of Sensible and Latent Cooling”, Research Report EP 87-15, June 1989 (URL: http://www.osti.gov/energycitations/basicsearch.jsp search by report number)

 

2        IPCC: Intergovernmental Panel on Climate Change, “Climate Change 2007: The Physical Science Basis”, Eds. Susan Solomon, et al. 2007. (URL: http://www.ipcc.ch/index.html See the Technical Summary, page 32.)