Numerical Simulation of Single- and Dual-media Thermocline Tanks for Energy Storage in Concentrating Solar Power Plants

Mira-Hernández, Carolina; Flueckiger, Scott M.; Garimella, Suresh V.

doi:10.1016/j.egypro.2014.03.099

Cited by 22 publications

(6 citation statements)

References 27 publications

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“…Lower thermocline thickness in Cofalit® can be explained by a smaller thermal diffusivity Table 2. Mira-Hernández et al [10] observed a similar trend previously, thermocline thickness increases with the filler material thermal diffusivity. Moreover, a higher convection coefficient is expected in the Cofalit® case compared to alumina, due to non-homogeneities in the particle shapes.…”

Section: Thermocline Thicknesssupporting

confidence: 80%

“…Various researchers validated the 1D model approach to providing reliable temperature prediction of thermocline TES [ [39], [49]]. Also, the results from 2D and 3D models did not exhibit any significant temperatures variation on the radial axis [ [9], [10], [57]]. Moreover, the results of a 1D model generated similar accuracy of a 3D CFD model upon comparsion for the same TES [58].…”

Section: Numerical Modelingmentioning

confidence: 92%

“…It could account for up to 33% of total tank height [9], which reduces the efficiency of the system by shortening the useful time of operation and available heat. Mira-Hernández et al [10] concluded that using solid filler material in thermocline TES implies a larger thermocline thickness when compared to solely liquid storage, and the author ascribed that to the higher thermal diffusivity of the solid filler materials compared to the HTF. However, heat exchange limitation between HTF and solid filler when introducing the latter could be the first reason for a bigger thermocline thickness, then the thermal diffusion of solid filler.…”

mentioning

confidence: 99%

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Experimental evaluation of vitrified waste as solid fillers used in thermocline thermal energy storage with parametric analysis

Keilany

Milhé

Bézian

et al. 2020

Journal of Energy Storage

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This work presents the first use of Cofalit® (vitrified asbestos-containing waste) as a solid filler in pilot-scale thermocline thermal energy storage (TES). The thermocline size is 4 m³ connected to the MicroSol-R installation at the PROMES research facility in Odeillo, France. The study compares the thermal performance of the thermocline filled with Cofalit® to the reference case of alumina spheres for typical charge and discharge operations. It evaluates the actual thermal behavior of thermocline considering three leading performance indicators: process duration, thermocline thickness, and process efficiency. The investigation shows a 22% shorter charge duration in Cofalit® compared to alumina and 16% shorter discharge duration. Cofalit® exhibits about 16% lower thermocline thickness during both charge and discharge compared to alumina. The charge efficiency is slightly better in Cofalit® than alumina with an efficiency of 82% and 78%, respectively. Also, Cofalit® has a better discharge efficiency, 90% with respect to 84% for alumina. These results confim a good thermal performance of Cofalit® as filler material in thermocline TES. Considering the cost-saving and positive environmental impact of using Cofalit® as well as the good thermal performance of the thermocline filled with it, Cofalit® appears a very good filler material in TES. The obtained temperatures from radial positions indicate no significant variation during charge and discharge, and this confirms the one-dimensional thermal behavior of this setup. A parametric analysis is performed using a 1D continuous solid (C-S) model to investigate the influence of particle diameter, porosity, thermal conductivity, and volumetric heat capacity on the thermal performance of the thermocline. The analysis confirms the experimental findings, and it indicates that about a 10.9% longer process duration is associated with a 10% larger volumetric heat capacity and less affected with other parameters. Thermocline thickness is mainly affected by the diameter as well as the volumetric heat capacity of the solid filler; it grows 2.2% for each 10% diameter increase and around 3.23% for doubling the volumetric heat capacity. Charge efficiency demonstrates independency from evaluated properties. While discharge efficiency increases sharply at a tiny particle diameter before an optimum diameter value is reached, then it starts to decrease by 1.4% to each 10% bigger diameter.

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Section: Thermocline Thicknesssupporting

confidence: 80%

Section: Numerical Modelingmentioning

confidence: 92%

mentioning

confidence: 99%

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Experimental evaluation of vitrified waste as solid fillers used in thermocline thermal energy storage with parametric analysis

Keilany

Milhé

Bézian

et al. 2020

Journal of Energy Storage

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“…Modi et al found that Solar Salt performs best, for thermocline TES configuration, among three compared HTFs (Solar Salt, HITEC, Therminol) [13]. Mira-Hernández et al [14] studied the performance of 2 thermocline tanks, with and without filler material under cyclic operation assuming adiabatic external wall boundary conditions. Greater thermal diffusion is observed with filler material, which elongates the heat-exchange region.…”

Section: Introductionmentioning

confidence: 98%

Compatibility tests between Solar Salt and thermal storage ceramics from inorganic industrial wastes

Motte¹,

Falcoz²,

Véron³

et al. 2015

Applied Energy

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“…In the DMT tank, the temperature in the upper half of the filler bed is set to T h (600 C), and the temperature of the lower half is set to T l (300 C). In the SMT tank, for which thermal diffusion is slower, an initial thermocline region is included at half the height of the tank in between two isothermal regions at T h and T l ; a linear temperature distribution between the hot and cold extremes is imposed across the thermocline region [32]. A one-dimensional, steady-state radial conduction analysis is used to compute an initial temperature field for the insulation.…”

Section: Numerical Modelmentioning

confidence: 99%

Comparative Analysis of Single- and Dual-Media Thermocline Tanks for Thermal Energy Storage in Concentrating Solar Power Plants

Mira-Hernández

Flueckiger

Garimella

2015

Journal of Solar Energy Engineering

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A molten-salt thermocline tank is a low-cost option for thermal energy storage (TES) in concentrating solar power (CSP) plants. Typical dual-media thermocline (DMT) tanks contain molten salt and a filler material that provides sensible heat capacity at reduced cost. However, conventional quartzite rock filler introduces the potential for thermomechanical failure by successive thermal ratcheting of the tank wall under cyclical operation. To avoid this potential mode of failure, the tank may be operated as a singlemedium thermocline (SMT) tank containing solely molten salt. However, in the absence of filler material to dampen tank-scale convection eddies, internal mixing can reduce the quality of the stored thermal energy. To assess the relative merits of these two approaches, the operation of DMT and SMT tanks is simulated under different periodic charge/discharge cycles and tank wall boundary conditions to compare the performance with and without a filler material. For all conditions assessed, both thermocline tank designs have excellent thermal storage performance, although marginally higher firstand second-law efficiencies are predicted for the SMT tank. While heat loss through the tank wall to the ambient induces internal flow nonuniformities in the SMT design over the scale of the entire tank, strong stratification maintains separation of the hot and cold regions by a narrow thermocline; thermocline growth is limited by the low thermal diffusivity of the molten salt. Heat transport and flow phenomena inside the DMT tank, on the other hand, are governed to a great extent by thermal diffusion, which causes elongation of the thermocline. Both tanks are highly resistant to performance loss over periods of static operation, and the deleterious effects of dwell time are limited in both tank designs.

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Numerical Simulation of Single- and Dual-media Thermocline Tanks for Energy Storage in Concentrating Solar Power Plants

Cited by 22 publications

References 27 publications

Experimental evaluation of vitrified waste as solid fillers used in thermocline thermal energy storage with parametric analysis

Experimental evaluation of vitrified waste as solid fillers used in thermocline thermal energy storage with parametric analysis

Compatibility tests between Solar Salt and thermal storage ceramics from inorganic industrial wastes

Comparative Analysis of Single- and Dual-Media Thermocline Tanks for Thermal Energy Storage in Concentrating Solar Power Plants

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