a b s t r a c tA concept of thermal battery based on advanced metal hydrides was studied for heating and cooling of cabins in electric vehicles. The system utilized a pair of thermodynamically matched metal hydrides as energy storage media. The pair of hydrides that was identified and developed was: (1) catalyzed MgH 2 as the high temperature hydride material, due to its high energy density and enhanced kinetics; and (2) TiV 0.62 Mn 1.5 alloy as the matching low temperature hydride. Further, a proof-of-concept prototype was built and tested, demonstrating the potential of the system as HVAC for transportation vehicles.Ó 2015 Published by Elsevier B.V.

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In this study, the results of NREL’s continued work on experimental characterization of the thermal performance of free-surface jets of automatic transmission fluid impinged on a heated target surface are presented. The measured heat transfer coefficients are useful for understanding factors influencing performance of driveline fluid-based cooling systems for electric machines and help designers in developing high-performance, power-dense and reliable machines. Experiments were carried out for different fluid and target surface temperatures (50°C, 70°C, and 90°C for the fluid and 90°C, 100°C, 110°C, and 120°C for the target surface). Impinging jet velocities (0.5 m/s to 7.5 m/s) and the jet position on the target surface (center versus edge) were also varied. The impinging angle was kept at 90° relative to the target surface. It was found that higher target surface temperature increased heat transfer coefficients, namely, increasing surface temperature from 90°C to 120°C enhanced heat transfer coefficient values at higher impinged jet velocities (7.5 m/s) by up to 15%.

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Thermal energy storage in subsurface soils can produce both inexpensive capacity and storage timescales of the order of a year. In concept, storing excess ambient or solar heat in summer for future winter use and winter “cold” for summer air conditioning can provide essentially zero-carbon space heating and cooling. An innovative ground coupling using a reversible (pump-assisted) thermosiphon with its high heat flux characteristics, intrinsic to two-phase heat pipes, as an inground heat exchanger is proposed and its performance is evaluated in a series of lab-scale experiments. Extraction and injection of heat from/into the water-saturated sand with a single thermosiphon unit representing a cell in an array of thermosiphons is modeled. These results demonstrate that near freezing point of water, due to weak or no natural convection, heat transfer is mainly due to conduction. Also, due to low energy input requirement for pumping working fluid and high heat transfer potential of the reversible thermosiphon, seasonal thermal energy or “cold” storage can be provided for low energy air conditioning applications.