Water loading lift and heat storage density prediction of adsorption heat storage systems using Dubinin-Polanyi theory—Comparison with experimental results

Calcium oxide/Calcium hydroxide can be utilized as a reaction system for thermochemical heat storage. It features a high storage capacity, is cheap, and does not involve major environmental concerns. Operationally, different fixed-bed reactor concepts can be distinguished; direct reactor are characterized by gas flow through the reactive bulk material, while in indirect reactors, the heat-carrying gas flow is separated from the bulk material. This study puts a focus on the indirectly operated fixed-bed reactor setup. The fluxes of the reaction fluid and the heat-carrying flow are decoupled in order to overcome limitations due to heat conduction in the reactive bulk material. The fixed bed represents a porous medium where Darcy-type flow conditions can be assumed. Here, a numerical model for such a reactor concept is presented, which has been implemented in the software DuMux. An attempt to calibrate and validate it with experimental results from the literature is discussed in detail. This allows for the identification of a deficient insulation of the experimental setup. Accordingly, heat-loss mechanisms are included in the model. However, it can be shown that heat losses alone are not sufficient to explain the experimental results. It is evident that another effect plays a role here. Using Bayesian inference, this effect is identified as the reaction rate decreasing with progressing conversion of reactive material. The calibrated model reveals that more heat is lost over the reactor surface than transported in the heat transfer channel, which causes a considerable speed-up of the discharge reaction. An observed deceleration of the reaction rate at progressed conversion is attributed to the presence of agglomerates of the bulk material in the fixed bed. This retardation is represented phenomenologically by mofifying the reaction kinetics. After the calibration, the model is validated with a second set of experimental results. To speed up the calculations for the calibration, the numerical model is replaced by a surrogate model based on Polynomial Chaos Expansion and Principal Component Analysis.

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The Impact of Active and Passive Thermal Management on the Energy Storage Efficiency of Metal Hydride Pairs Based Heat Storage

Energies ◽

10.3390/en14113006 ◽

2021 ◽

Vol 14 (11) ◽

pp. 3006

Author(s):

Serge Nyallang Nyamsi ◽

Ivan Tolj

Keyword(s):

Heat Transfer ◽

Energy Storage ◽

Thermal Management ◽

Metal Hydride ◽

Heat Storage ◽

Energy Storage Density ◽

Storage Efficiency ◽

Transfer Enhancement ◽

Storage Density ◽

Energy Storage Efficiency

Two-tank metal hydride pairs have gained tremendous interest in thermal energy storage systems for concentrating solar power plants or industrial waste heat recovery. Generally, the system’s performance depends on selecting and matching the metal hydride pairs and the thermal management adopted. In this study, the 2D mathematical modeling used to investigate the heat storage system’s performance under different thermal management techniques, including active and passive heat transfer techniques, is analyzed and discussed in detail. The change in the energy storage density, the specific power output, and the energy storage efficiency is studied under different heat transfer measures applied to the two tanks. The results showed that there is a trade-off between the energy storage density and the energy storage efficiency. The adoption of active heat transfer enhancement (convective heat transfer enhancement) leads to a high energy storage density of 670 MJ m−3 (close to the maximum theoretical value of 755.3 MJ m−3). In contrast, the energy storage efficiency decreases dramatically due to the increase in the pumping power. On the other hand, passive heat transfer techniques using the bed’s thermal conductivity enhancers provide a balance between the energy storage density (578 MJ m−3) and the energy efficiency (74%). The utilization of phase change material as an internal heat recovery medium leads to a further reduction in the heat storage performance indicators (142 MJ m−3 and 49%). Nevertheless, such a system combining thermochemical and latent heat storage, if properly optimized, can be promising for thermal energy storage applications.

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Artificial Neural Network Simulation of Energetic Performance for Sorption Thermal Energy Storage Reactors

Energies ◽

10.3390/en14113294 ◽

2021 ◽

Vol 14 (11) ◽

pp. 3294

Author(s):

Carla Delmarre ◽

Marie-Anne Resmond ◽

Frédéric Kuznik ◽

Christian Obrecht ◽

Bao Chen ◽

...

Keyword(s):

Neural Network ◽

Artificial Neural Network ◽

Energy Storage ◽

Thermal Energy ◽

Temperature Difference ◽

Thermal Energy Storage ◽

Heat Storage ◽

Experimental Results ◽

Physical Models ◽

Artificial Neural

Sorption thermal heat storage is a promising solution to improve the development of renewable energies and to promote a rational use of energy both for industry and households. These systems store thermal energy through physico-chemical sorption/desorption reactions that are also termed hydration/dehydration. Their introduction to the market requires to assess their energy performances, usually analysed by numerical simulation of the overall system. To address this, physical models are commonly developed and used. However, simulation based on such models are time-consuming which does not allow their use for yearly simulations. Artificial neural network (ANN)-based models, which are known for their computational efficiency, may overcome this issue. Therefore, the main objective of this study is to investigate the use of an ANN model to simulate a sorption heat storage system, instead of using a physical model. The neural network is trained using experimental results in order to evaluate this approach on actual systems. By using a recurrent neural network (RNN) and the Deep Learning Toolbox in MATLAB, a good accuracy is reached, and the predicted results are close to the experimental results. The root mean squared error for the prediction of the temperature difference during the thermal energy storage process is less than 3K for both hydration and dehydration, the maximal temperature difference being, respectively, about 90K and 40K.

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A state-of-the-art review on hybrid heat pipe latent heat storage systems

Energy Conversion and Management ◽

10.1016/j.enconman.2015.08.044 ◽

2015 ◽

Vol 105 ◽

pp. 1178-1204 ◽

Cited By ~ 58

Author(s):

M.S. Naghavi ◽

K.S. Ong ◽

M. Mehrali ◽

I.A. Badruddin ◽

H.S.C. Metselaar

Keyword(s):

Heat Pipe ◽

Latent Heat ◽

Heat Storage ◽

State Of The Art ◽

Storage Systems ◽

Latent Heat Storage

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Solid Media Thermal Storage Development and Analysis of Modular Storage Operation Concepts for Parabolic Trough Power Plants

Journal of Solar Energy Engineering ◽

10.1115/1.2804625 ◽

2007 ◽

Vol 130 (1) ◽

Cited By ~ 41

Author(s):

Doerte Laing ◽

Wolf-Dieter Steinmann ◽

Michael Fiß ◽

Rainer Tamme ◽

Thomas Brand ◽

...

Keyword(s):

Heat Transfer ◽

Power Plants ◽

Heat Storage ◽

Storage Systems ◽

Storage System ◽

Sensible Heat ◽

Economic Optimization ◽

Parabolic Trough ◽

Solid Media ◽

Exergetic Analysis

Cost-effective integrated storage systems are important components for the accelerated market penetration of solarthermal power plants. Besides extended utilization of the power block, the main benefits of storage systems are improved efficiency of components, and facilitated integration into the electrical grids. For parabolic trough power plants using synthetic oil as the heat transfer medium, the application of solid media sensible heat storage is an attractive option in terms of investment and maintenance costs. For commercial oil trough technology, a solid media sensible heat storage system was developed and tested. One focus of the project was the cost reduction of the heat exchanger; the second focus lies in the energetic and exergetic analysis of modular storage operation concepts, including a cost assessment of these concepts. The results show that technically there are various interesting ways to improve storage performance. However, these efforts do not improve the economical aspect. Therefore, the tube register with straight parallel tubes without additional structures to enhance heat transfer has been identified as the best option concerning manufacturing aspects and investment costs. The results of the energetic and exergetic analysis of modular storage integration and operation concepts show a significant potential for economic optimization. An increase of more than 100% in storage capacity or a reduction of more than a factor of 2 in storage size and therefore investment cost for the storage system was calculated. A complete economical analysis, including the additional costs for this concept on the solar field piping and control, still has to be performed.

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