On the cooling potential of elastocaloric devices for building ventilation

Abstract

Refrigerants in vapor-compression systems have a global warming potential thousands of times that of carbon dioxide, yet their spread on the market is unrivalled. Elastocaloric systems, based on solid state cooling, feature among the most promising alternatives. In this paper, an elastocaloric device for air ventilation (ECV) composed by parallel and serial connection of multiple shape memory alloy (SMA) films, is investigated via volume-based finite difference simulation in MATLAB and dynamic building simulation in TRNSYS considering eight cities across the globe. The models assume experimentally demonstrated thermal parameters for the elastocaloric phase transformation around room temperature and a single-storey reference building. The ECV operates according to an optimized, energy-saving logic that includes load partialization and recirculation. Parametric analyses suggest that moderate terminal velocities (~2 m/s) and a climate-specific design aimed at maximizing the use of the ECV device at nominal cooling capacity are key to reach building cooling needs reductions up to 70% in the considered scenarios. Partialization results in enhanced energy flexibility and conservation, whereas recirculation extends the ECV usability to extreme heat conditions. In absolute terms, the ECV works best under hot climates (e.g. Cairo, Dubai, Brisbane), with monthly cooling load reductions about 2/3-fold compared to cold locations (e.g. Milan, Hobart). The performance is extremely sensitive to the ventilation rate. Thermal zones requiring 1 to 2 air changes per hour are best suited. These findings provide initial insight into design criteria, opportunities and limitations on the use of elastocaloric devices for building ventilation to guide future experimental verification.