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Barrow Green is developing an energy-efficient hydrofluorocarbon-free cooling technology, invented at the U.S. Army Research Laboratory, for large-scale and small-scale uses.
About
Barrow Green, LLC is developing an elastocaloric cooling and heating technology, invented at the Army Research Laboratory (ARL), which does not utilize greenhouse gases as a refrigerant and which will be highly energy efficient. Elastocaloric cooling involves causing shape memory alloys (commonly nitinol (NiTi), an alloy of nickel and titanium) to undergo stress-induced phase changes and, correspondingly, to release or absorb heat. The Department of Energy and others have identified elastocaloric cooling as the most promising alternative to conventional vapor compression cooling. The obstacle to commercialization to date has been the large amount of force required to cause the requisite phase changes. Barrow Green's technology reduces the amount of force required and, correspondingly, has the potential to achieve energy efficiency significantly greater than that of conventional vapor compression technology. Elastocaloric development to date has been focused on the use of either tension or compression to cause uniaxial stress and, accordingly, to cause the requisite phase changes. A key obstacle to the development of elastocaloric cooling has been the amount of force needed to cause the requisite phase changes and, correspondingly, the need for bulky/expensive actuators to generate such force. Barrow Green's innovation is to reduce the amount of force required to cause a phase change by bending (rather than compressing or stretching) the shape memory alloys. Such reduction in force directly correlates with increased energy efficiency. Bending also allows elastocaloric material to be driven in a loop using a commercial off-the-shelf electric motor. During certain portions of the loop, the elastocaloric material is stressed and releases heat. During other portions, the stress is relaxed and the elastocaloric material absorbs heat. Increased heat transfer can be achieved with multiple loops. In addition, multiple stages, cascaded in a way where a stage heats or cools a subsequent stage, can be used to achieve greater temperature differences.
Key Benefits
Barrow Green's innovation does not utilize greenhouse gases as a refrigerant and has the potential to be more energy efficient than legacy vapor compression cooling technology. Other advantages include the technology’s (i) lightweight and compact size, (ii) low cost, (iii) low vibration, (iv) ability to operate in cooling and heating mode, (v) ability to separate the hot and cold zones (vi) ease of integration with existing HVAC and water systems and (vii) potential for commercial scalability. ARL’s dual-use cooling and heating technology can be used for both small-scale and large-scale applications.
Applications
Barrow Green's cooling and heating technology can be used for both small-scale and large-scale cooling and applications including air conditioners for structures and vehicles, refrigerators, and high performance wearables such as for personal protective equipment (PPE). The application relevant to this challenge is heating. Barrow Green's technology can be used to concentrate low grade waste heat into higher grade industrial heat and, accordingly, reduce the burning of fossil fuels.