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Passive, Non-powered Re-chargeable Heat Storage Systems for Cold Climate Operations



OBJECTIVE: The objective of this topic is to develop products that can store and deliver heat without the need for power. 

DESCRIPTION: Extremity protection for the current Extended Cold Weather Clothing System (ECWCS) utilizes a series of garments designed to be worn within tightly defined temperature ranges. For the hands, Soldiers can increase protection by switching from gloves to mittens. A similar option exists for wearing boots with progressively higher levels of insulative capabilities. The trade off to higher insulation under the current system is the loss of dexterity and increased weight, both of which impact mission execution and success. Improvements in thermal extremity protection will offer a cognitive benefit to Soldier performance as well as enable better dexterity for operations—such as shooting— which combined will improve Soldier lethality in extreme operating conditions. Many athletic and sportswear companies are now selling garments with built-in heating elements, from socks and gloves to full jackets, thus allowing a wearer to maintain thermal comfort with less bulk. However, to date, the majority of these systems require the use of power. In addition to the power challenge, many systems are not Berry amendment compliant, limiting procurement options. The focus of efforts under this topic call will be on developing material systems that can store and deliver heat to a Soldier in the field without the need for a power input. Material systems must be able to be recharged for additional heat release cycles in a field or deployed setting. 

PHASE I: Phase I of the proposal must demonstrate feasibility of the technical approach through development of a preliminary material concept. The material must demonstrate successful heat release that is initiated without a power input. The heat release must be compatible with applications adjacent to human skin without the risk of burns (< 44° C for direct contact systems over 6 hours). By the end of Phase I, a feasibility study of scale up must be completed, including an estimate of material cost. There must also be a coherent prototype design for fabrication in later Phases. Sample material (3 prototypes or formulations) must be delivered at the end of Phase I. Heat generation should be sustainable for at least 3 hours. Number of recharges during the life of the material is to be estimated. Technologies at the end of Phase I should be at TRL 4. 

PHASE II: Phase II will focus on scale up of the successful Phase I technology into prototypes for lab and field simulated evaluation. Prototypes and material must demonstrate successful heat storage and release for at least 3 hours. The form factor of the prototype is left to the discretion of the principal investigators (PI). Prototype materials must demonstrate consistent function in varying environmental exposures (high humidity, wind, etc), including after pro-longed exposure to temperatures as low as -40 ⁰ C. The final deliverable must also include a commercialization assessment and the viability of mass production for the technology. Deliverables to include production cost estimate, technical data package, final report, and 3 prototypes. Technologies at this stage should be at a TRL 4 to 5. 

PHASE III: Phase III will demonstrate scalability and operational application of the proposed technology. The technology developed under this effort has direct application to Soldier operational clothing and individual equipment. The results of this effort may culminate in a material that can be fielded as an insert to complement the current ECWCS system or could be directly integrated into the textile layers of the ECWCS. While the focus of this effort is use at the Soldier level, technologies could be extrapolated to other military applications, for example, maintenance of military equipment in cold temperatures for optimal performance, icing prevention of critical tools, weapons, and equipment etc. Successful materials may also find commercial applications in passive or latent heat storage for energy optimization systems and infrastructure maintenance (thermal regulation, ice prevention etc), recreational gear for cold weather activities, and non-military police and rescue forces. 


1: Holmer et al, 2010, International Journal of Occupational Safety and Ergonomics (JOSE), 16(3), 387–404, "A Review of Technology of Personal Heating Garments"

2:  Riffat et al, 2015, Renewable and Sustainable Energy Reviews, 41, 356-367, "The Latest Advancements on Thermochemical Heat Storage Systems"

3:  Ghafoor et al, 2016, Energy Conversion and Management, 115, 132-158, "A Review of the Performances Enhancement of PCM Based latent heat Storages System within the Context of Materials, Thermal Stability and Compatibility"

4:  Zeiler et al, 2014, Proceedings of the 8th Windsor Conference, "personal heating

5:  energy use and effectiveness"

KEYWORDS: Personal Heating, Thermal Comfort Management, Powerless Heating 

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