Evaluation of Heat Output Densities of Lithium Chloride-Modified Magnesium Hydroxide for Thermochemical Energy Storage

Ishitobi, Hiroyuki; Hirao, Naoya; Ryu, Junichi; Kato, Yukitaka

doi:10.1021/ie302841y

Cited by 42 publications

(104 citation statements)

References 22 publications

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“…[15,16] Although the Mg(OH) 2 /MgO TCES cycle is well known, [15,[17][18][19][20] low cycle stability and incomplete hydration impede application. In literature, different efforts were made to improve the reactivity and thermal conductivity of the material by addition of lithium salts, [21][22][23] increasing the reaction rate, and the preparation of composite materials with expanded graphite. [20,[24][25][26] The issue of limited reactivity and low cycle stability is mainly related to the kinetic inhibition of the critical dissociation of water on the MgO surface.…”

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confidence: 99%

Calcium Doping Facilitates Water Dissociation in Magnesium Oxide

Müller

Knöll

Ruh

et al. 2017

Advanced Sustainable Systems

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is the most ubiquitously used form of energy, including in electricity generation, power plants, or industry. [5] In this context, in 2011, the International Energy Agency estimated in a report entitled "Solutions for a low-carbon energy future" that global energy loss through waste heat accounts for two-third of the overall energy production. [6] Therefore, methods suitable for reduction of waste heat or reutilization thereof could contribute significantly to a sustainable energy management. [7][8][9] Among the different approaches to this challenge, thermochemical energy storage (TCES) is a highly appealing concept, since by means of a reversible chemical reaction, a suitable material energy is converted from thermal to chemical energy. The charged material may be stored for any period of time without further losses or additional infrastructure (such as insulation), until, by addition of the proper reactant, the discharging reaction, releasing the stored energy in form of heat, is initiated. [2,[10][11][12] The economic benefit of implementing TCES cycles in the energy management was demonstrated by several economic feasibility studies, illustrating that, e.g., with the waste heat from Lenzing AG, [13] Calcium doping of magnesium oxide results in significantly increased water dissociation rates, thus enhancing both hydration rate and reaction completeness of hydration compared to pure MgO. For a series of mixed magnesiumcalcium oxides (Mg x Ca 1−x O) with varying Ca contents between 0% and 40%, the material of a composition Mg 0.9 Ca 0.1 O shows the fastest rehydration, transforming completely within 80 min to the mixed hydroxide. In consecutive dehydration/rehydration cycles, reasonable cycle stability is found. A "regeneration" of the aged material (reactivity reduced by excessive cycling) in liquid water re-establishes the initial rehydration reactivity. Density functional theory calculations support the experimental findings, confirming that calcium doping can reduce the energy of the rate limiting water dissociation reaction, exploiting both electronic and steric (size) effects. Three major requirements for future sustainable energy management have been established including reduction of greenhouse gas emissions, promotion and increased use of renewable energy sources, and enhancing the efficiency of energy use. [1,2] Whereas the first two issues are widely discussed and the subject of international treaties such as the Kyoto protocol [3] and the Paris agreement, [4] awareness of the poor overall efficiency of today's energy economy is rather limited. Heat

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confidence: 99%

Calcium Doping Facilitates Water Dissociation in Magnesium Oxide

Müller

Knöll

Ruh

et al. 2017

Advanced Sustainable Systems

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“…It was assumed that LiCl/Mg(OH) 2 was dehydrated at ~300 °C in the reactor, and LiCl/MgO was hydrated at ~140 °C, with a water vapor pressure of 57.8 kPa. The preparation procedure of LiCl/Mg(OH) 2 in bench-scale was shown in our previous paper [20].…”

Section: Materials For Thermochemical Energy Storagementioning

confidence: 99%

“…In previous studies [20,21], dehydration was performed at 300 °C for 30 min and hydration was performed at 110-150 °C for 80 min, for LiCl/Mg(OH) 2 . The heat output density of LiCl/Mg(OH) 2 at a dehydration temperature of 300 °C, hydration temperature of 140 °C, and water vapor pressure of 57.8 kPa was 872 kJ kg 1 .…”

Section: Materials For Thermochemical Energy Storagementioning

confidence: 99%

“…LiCl, Mg(OH) 2 , MgO, and H 2 O have low toxicities; Thus, LiCl/Mg(OH) 2 is an eco-friendly material for fabricating TcES systems. LiCl/Mg(OH) 2 showed a high heat output density (1.40 × 10 3 kJ kg 1 at a dehydration temperature of 300 °C, hydration temperature of 110 °C, water vapor pressure of 57.8 kPa, and vapor supply for 80 min) [20,21]. Though it is necessary to investigate the required amount of TcES material to evaluate its potential for load leveling, it has not been sufficiently studied.…”

Section: Introductionmentioning

confidence: 99%

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Combination of Thermochemical Energy Storage and Small Pressurized Water Reactor for Cogeneration System

2015

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In recent decades, small nuclear reactors for cogeneration systems have been studied. Generally, nuclear plants are operated at steady state, but the heat demand load is not steady. Load leveling using thermochemical energy storage (TcES) is a potential method for overcoming this problem. In this work, the heat load of a town was assumed, and the required amount of TcES material for load leveling was estimated. The amount of material required, relative to the volume of the nuclear reactor vessel, was acceptable for installing a TcES system at the nuclear plant.

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“…Ishitobi et al [13,14] developed new chemical heat storage material, which was proposed to use for MgO/H 2 O chemical heat pump, by mixing LiCl to pure Mg(OH) 2 ;…”

Section: Introductionmentioning

confidence: 99%