Short-term storage systems of thermal energy for buildings: a review

Abstract

Thermal energy storage in buildings is essential to reduce energy consumption, to switch electrical consumption from on-peak period to off-peak period and to develop the use of intermittent renewable energy sources. Several systems designed to store thermal energy on a short-term scale (maximum a few days of storage) are presented in previous publications. However, there are no available comparisons of these systems and their conditions of use. This paper details these different designs for short-term scale thermal energy storage, regarding (i) their passive or active nature, (ii) their usage conditions and (iii) their performances. In the first section, the thermal properties of materials are listed. In particular, advantages and problems associated with phase change materials are presented. Subsequently, thermal storage systems are presented in two parts, on the one hand, passive systems and on the other hand active systems, according to the fluid used. For each system, the advantages of substituting sensible storage with latent storage are highlighted. Furthermore, an original and comparative analysis of published studies attempts to define some criteria and requirements for efficient use of latent storage. This review demonstrates that an exhaustive comparison of the systems encounters difficulties, due to the differences between the studies with respect to experimental measurements and weather data and the lack of similar comparison criteria, such as decrement factor, efficiency and cost. IntroductionNowadays, global warming is one of the most worrying problems in the world. The Intergovernmental Panel on Climate Change foresees an increase in average Earth temperature, possibly reaching 68C by 2050. Thus, we need to find more efficient ways to utilize energy in order to significantly reduce both energy consumption and greenhouse gas emissions. In the particular field of building, which represents almost 40% of the world's total energy consumption, sustainable buildings need to take advantage of renewable and waste energy to become ultralow energy buildings. The main difficulty of renewable energy use is that most renewable energy sources (especially wind energy and solar energy) are intermittent, providing time-dependent energy densities. In addition, energy consumption of buildings is, in most cases, also intermittent, depending on the building's use and its inhabitants' activities and behaviour.Thus, thermal energy storage (TES) is often considered as one of the most promising technologies for building applications. Recently, increasing attention has been paid to the utilization of this technology since it has considerably a high potential to meet society's needs for more effective and environmentally benign energy use. Indeed, on the one hand, TES technology allows the correction of the time mismatch between energy demand and the economically most favourable supply of energy (i.e. during off-peak hours). On the other hand, this technology is well adapted to

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