Thermodynamic Efficiency of Water Vapor/Solid Chemical Sorption Heat Storage for Buildings: Theoretical Limits and Integration Considerations

The theoretical limits of water sorbate-based chemical sorption heat storage are investigated in this study. First, a classification of thermochemical heat storage is proposed based on bonding typology. Then, thermodynamics of chemical solid/gas sorption is introduced. The analysis of the reaction enthalpy from the literature indicates that this value is only slightly varying for one mole of water. Using this observation, and with the help of thermodynamic considerations, it is possible to derive conclusions on energy efficiency of closed and open heat storage systems. Whatever the salt, the main results are (1) the energy required for evaporation of water is, at least, 65% of the available energy of reaction, and (2) the maximum theoretical energy efficiency of the system, defined as the ratio of the heat released to the building over the heat provided to the storage, is about 1.8. Considering the data from literature, it is also possible to show that perfectly working prototypes have an energy efficiency about 49%. Based on those results, it is possible to imagine that for the best available material, a perfect thermochemical heat storage system would correspond to 12 times water with a temperature difference about 50 °C. Such solution is definitely competitive, provided that some difficult issues are solved—issues that are discussed throughout this paper.

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Thermodynamic Efficiency of Water Vapor / Solid Chemical Sorption Heat Storage for Buildings: Theoretical Limits and Integration Considerations

10.20944/preprints201904.0079.v1 ◽

2019 ◽

Author(s):

Frédéric Kuznik

Keyword(s):

Energy Efficiency ◽

Water Vapor ◽

Heat Storage ◽

Storage Systems ◽

Thermodynamic Efficiency ◽

Reaction Enthalpy ◽

Available Energy ◽

Thermochemical Heat Storage ◽

Sorption Heat

The theoretical limits of water sorbate based chemical sorption heat storage are investigated in this study. First, a classification of \textit{thermochemical heat storage} is proposed based on bonding typology. Then, thermodynamics of chemical solid/gas sorption is introduced. The analysis of the reaction enthalpy from the literature indicates that this value is only slightly varying for one mole of water. Using this observation, and with the help of thermodynamical considerations, it is possible to derive conclusions on energy efficiency of closed and open heat storage systems. Whatever the salt, the main results are 1) the energy required for evaporation of water is, at least, 65% of the available energy of reaction and 2) the maximum theoretical energy efficiency of the system is about 1.8.

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Thermodynamic and kinetic study of the dehydration process of CaO/Ca(OH) 2 thermochemical heat storage system with Li doping

Chemical Engineering Science ◽

10.1016/j.ces.2015.07.053 ◽

2015 ◽

Vol 138 ◽

pp. 86-92 ◽

Cited By ~ 26

Author(s):

J. Yan ◽

C.Y. Zhao

Keyword(s):

Kinetic Study ◽

Heat Storage ◽

Storage System ◽

Dehydration Process ◽

Li Doping ◽

Thermochemical Heat Storage

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Thermochemical heat storage system for preventing battery thermal runaway propagation using sodium acetate trihydrate/expanded graphite

Chemical Engineering Journal ◽

10.1016/j.cej.2021.133536 ◽

2021 ◽

pp. 133536

Author(s):

Jiahao Cao ◽

Ziye Ling ◽

Shao Lin ◽

Yangjing He ◽

Xiaoming Fang ◽

...

Keyword(s):

Sodium Acetate ◽

Heat Storage ◽

Storage System ◽

Expanded Graphite ◽

Thermal Runaway ◽

Sodium Acetate Trihydrate ◽

Acetate Trihydrate ◽

Thermochemical Heat Storage

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Thermochemical energy storage – from fundamental research to TRL IV

E3S Web of Conferences ◽

10.1051/e3sconf/201910802013 ◽

2019 ◽

Vol 108 ◽

pp. 02013

Author(s):

Piotr Babiński ◽

Michalina Kotyczka – Morańska ◽

Jarosław Zuwała

Keyword(s):

Energy Storage ◽

Heat Carrier ◽

Storage Tank ◽

Storage Capacity ◽

Heat Storage ◽

Solid Medium ◽

Storage System ◽

Reversible Reactions ◽

Thermochemical Heat Storage ◽

Fundamental Research

The paper presents the results of the fundamental research devoted to the application of MgSO4 as a heat carrier for thermochemical seasonal storage system devoted for household application followed by the results of 35kWh storage tank (TRL IV) charging and discharging tests. Seasonal thermochemical heat storage, based on the reversible reactions of hydratation and dehydratation of a solid medium gives an opportunity to accumulate the energy with a storage capacity exceeding 300-400 kWh/m3.

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Optimal Design of Combined Two-Tank Latent and Metal Hydrides-Based Thermochemical Heat Storage Systems for High-Temperature Waste Heat Recovery

Energies ◽

10.3390/en13164216 ◽

2020 ◽

Vol 13 (16) ◽

pp. 4216 ◽

Cited By ~ 1

Author(s):

Serge Nyallang Nyamsi ◽

Mykhaylo Lototskyy ◽

Ivan Tolj

Keyword(s):

Energy Storage ◽

Melting Point ◽

Heat Recovery ◽

Waste Heat Recovery ◽

Heat Storage ◽

Waste Heat ◽

Storage Systems ◽

Storage System ◽

Metal Hydrides ◽

Thermochemical Heat Storage

The integration of thermal energy storage systems (TES) in waste-heat recovery applications shows great potential for energy efficiency improvement. In this study, a 2D mathematical model is formulated to analyze the performance of a two-tank thermochemical heat storage system using metal hydrides pair (Mg2Ni/LaNi5), for high-temperature waste heat recovery. Moreover, the system integrates a phase change material (PCM) to store and restore the heat of reaction of LaNi5. The effects of key properties of the PCM on the dynamics of the heat storage system were analyzed. Then, the TES was optimized using a genetic algorithm-based multi-objective optimization tool (NSGA-II), to maximize the power density, the energy density and storage efficiency simultaneously. The results indicate that the melting point Tm and the effective thermal conductivity of the PCM greatly affect the energy storage density and power output. For the range of melting point Tm = 30–50 °C used in this study, it was shown that a PCM with Tm = 47–49 °C leads to a maximum heat storage performance. Indeed, at that melting point narrow range, the thermodynamic driving force of reaction between metal hydrides during the heat charging and discharging processes is almost equal. The increase in the effective thermal conductivity by the addition of graphite brings about a tradeoff between increasing power output and decreasing the energy storage density. Finally, the hysteresis behavior (the difference between the melting and freezing point) only negatively impacts energy storage and power density during the heat discharging process by up to 9%. This study paves the way for the selection of PCMs for such combined thermochemical-latent heat storage systems.

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