This Small Business Innovation Research Phase I project focuses on developing thermoelastic materials with long fatigue life, suitable for refrigeration and cooling applications. Thermoelastic cooling (TC) is a new technology based on the latent heat generated and absorbed during the stress-induced phase transformation in a shape memory alloy (SMA). The efficiency of the thermoelastic cooling process is high, with a coefficient of performance (COP) estimated at 11.8, which is double that of state-of-the-art vapor compression technology. This technology, however, has drawbacks in its current preliminary form; these include a relatively low latent heat (~12 kJ/kg) and a limited fatigue life. The objective of this project will be to develop a new SMA material for TC applications, which features long fatigue life and small thermal hysteresis. Novel methods, such as thick-film synthesis and micro-indentation, will be used to prepare samples. The resulting materials will then be characterized based on hysteresis, latent heat, and stress-strain relationships.
The broader impact/commercial potential of this project is huge, with the resulting products having the potential to displace vapor compression technology in a variety of residential and commercial cooling and refrigeration applications. If successfully commercialized, this technology could reduce U.S. annual primary electricity consumption by up to 3.73 quads in 2030. Since the thermoelastic cooling method completely eliminates the need for an entire class of high global warming potential (GWP) greenhouse gases, namely hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs), the total CO2 savings could be as high as 368 million metric tons. A successful commercialization and deployment of products based on the TC method could create hundreds of quality domestic jobs, with most coming in the manufacturing sector.
According to the 2008 Buildings Energy Data Book, building space cooling and refrigeration will consume 7.46 quads of primary electricity and generate 447 million metric tons (MMT) of CO2 emission in 2030. It is equivalent to ~5% of primary energy consumption and ~5% of CO2 emissions in U.S. Currently, more than 90% of space cooling is provided by vapor compression (VC) based systems in the U.S. Refrigerants used in VC systems are a significant source of green house gas (GHG) emissions. Refrigerants such as hydrochloroflurocarbons (HCFC) or halofluorocarbons (HFC) have global warming potential (GWP) more than 1000 times that of CO2. In order to achieve more than incremental gains in efficiency and altogether eliminate HCFC/HFC refrigerants, a fundamental change must be made to the cooling/refrigeration method, which is dominated by vapor compression (VC) technology. There are several alternative technologies including electrocaloric, magnetocaloric, thermoacoustic, thermoelectric and thermoelastic. Based on our investigation, we found that only magnetocaloric and thermoelastic technologies show significant impacts to both energy efficiency and environment. Of the two methods, only thermoelastic heating/cooling technology has the potential for near-future commercialization due to its cost-savings. At MEST, we aim to develop the thermoelastic cooling technology toward early commercialization. A successful deployment of the technology is disruptive and will directly address energy saving and environmental issues, potentially saving the HVAC industry millions of dollars and significantly reducing GHG emissions. Currently, the thermoelastic technology has passed the concept-proof stage. With the support of NSF SBIR Phase I/IB, MEST has successfully conducted series of synthesis and optimization research of thermoelastic materials, specifically addressing the important two issues that are slowing down the commercialization process, i.e. low latent heat values and short fatigue life of the working material, from both theoretical evaluations and experimental characterizations. The project research results have shown a great opportunity for this technology to achieve commercial success. Additionally, the industrial partner through the Phase IB project will continue working with us to focus the development of the technology toward specific applications.
