High-Temperature Latent Heat Storage Technology to Utilize Exergy of Solar Heat and Industrial Exhaust Heat

Abstract

Summary Latent heat storage (LHS) using phase change materials is quite attractive for utilization of the exergy of solar energy and industrial exhaust heat because of its high‐heat storage capacity, heat storage and supply at constant temperature, and repeatable utilization without degradation. In this article, general LHS technology is outlined, and then recent advances in the uses of LHS for high‐temperature applications (over 100 °C) are discussed, with respect to each type of phase change material (e.g., sugar alcohol, molten salt, and alloy). The prospects of future LHS systems are discussed from a principle of exergy recuperation. In addition, the technologies to minimize exergy loss in the future LHS system are discussed on the basis of the thermodynamic analysis by ‘thermodynamic compass’. Copyright © 2016 John Wiley & Sons, Ltd.

Molten salts: Potential candidates for thermal energy storage applications

“…For example, volume expansion ratio of one of the most commonly used molten salt PCM, that is, NaCl (T m $ 800 C), is 0.26 . 218 • Another issue is incongruent melting, which reduces the reversibility of the phase change process and, as a result, the heat storage capacity. 219 Therefore, before a salt hydrate can be employed as a PCM, fundamental study into its thermal characteristics, such as phase change temperature, sub-cooling behavior, nucleation rate, and enthalpy curve, is required.…”

“…In spite of the low cost and mouldable characteristics of molten salts, they face a few concerns in successful application at CSPPs and NPPs: Due to low thermal conductivity (under 1 W/m K) of applied molten salts in LHTS systems, development of novel and cost‐effective nanomodifiers has to be focused besides understanding the dispersion phenomenon to derive maximum benefit. High volume expansivity of most organic PCMs makes it unsuitable for them to be capsuled owing to thermal stress generation. For example, volume expansion ratio of one of the most commonly used molten salt PCM, that is, NaCl ( T m ~ 800°C), is 0.26 218 Another issue is incongruent melting, which reduces the reversibility of the phase change process and, as a result, the heat storage capacity 219 .…”

Development of a new methodology for validating thermal storage media: Application to phase change materials

“…However, it is in the field of latent heat storage materials, which are usually called phase change materials (PCMs), where we can find the majority of these studies. This is due to the large number of PCMs that are suitable for applications in a very wide temperature range (from 0°C to 800°C). Taking into account that the thermophysical properties that make PCMs suitable as storage media are phase change temperature ( T ph‐ch ) and enthalpy (Δ H ph‐ch ), Figure represents Δ H ph‐ch vs T ph‐ch for PCMs that undergo solid‐liquid transitions together with the temperature ranges of the possible storage applications.…”

Preparation and characterization of erythritol/polyaniline form‐stable phase change materials containing silver nanowires

“…19 However, graphite-based supporting materials are generally soft and elastic, which would result in possible leakage of PCMs when the form-stable PCMs were pressed. In addition, inorganic materials such as polysiloxane, 3 silica aerogel, 8 and vermiculite 20 have also been applied to form-stabilize some sugar alcohols such as ME. However, the latent heat storage capacity was not very high.…”

“…Graphite-based materials are another kind of important supporting materials. In addition, inorganic materials such as polysiloxane, 3 silica aerogel, 8 and vermiculite 20 have also been applied to form-stabilize some sugar alcohols such as ME. 19 However, graphite-based supporting materials are generally soft and elastic, which would result in possible leakage of PCMs when the form-stable PCMs were pressed.…”