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Journal ArticleDOI

Comparative study of single and multi-layered packed-bed thermal energy storage systems for CSP plants

21 Oct 2017-Applied Solar Energy (Allerton Press)-Vol. 53, Iss: 3, pp 276-286
TL;DR: In this paper, the effect of phase change materials (PCM) on the discharge duration of a multi-layer thermal energy storage (TES) system was analyzed for a storage tank operating between 563 and 663 K with bed dimensions of 12 and 14.38 m using solar salt as Heat Transfer Fluid (HTF).
Abstract: The Multi-layered Thermal Energy Storage (TES) tank consists of three regions–top and bottom part is packed with suitable Phase Change Materials (PCM) and low-cost pebbles are placed in the middle region, whereas entire tank portion is filled by solid fillers in Single-layered tank system. For a storage tank operating between 563 and 663 K with bed dimensions of 12 and 14.38 m using Solar salt as Heat Transfer Fluid (HTF), it is observed that the duration of discharge for multi-layered tank is 5.32 h whereas it is 4.19 h for single-layered tank with a Reynolds number of 10. The effect of intermediate melting temperature range of PCMs are also analyzed by taking PCMs with sharp as well as intermediate melting ranges. Further, comparison of single and multi-layered systems is carried out by analyzing the temperature profiles and width of both PCM layers. The width of top and bottom PCM layers of tank is varied from 0 to 30% to analyze its effect on the discharging duration. It is observed that multi-layered system provides extra discharge of 1 h with introduction of PCM at top and bottom with a width of 10%. Discharge duration increases with increase in PCM width whereas the percentage increase in duration of discharge with increase in PCM width is comparatively less. It is also seen that PCMs with sharp melting point performs better compared to one having intermediate range of melting temperatures. Multi-layered configuration concept offers best possibilities as integration to CSP plants with desired efficiency.
Citations
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Journal ArticleDOI
TL;DR: In this article, the authors focus on the application of various phase change materials based on their thermophysical properties, in particular, the melting point, thermal energy storage density and thermal conductivity of the organic, inorganic and eutectic phases.

813 citations

Journal ArticleDOI
TL;DR: In this article, a cascade type phase change materials (PCM) energy storage system for solar thermal electricity plants with its technical assessment is presented, using four buckets with the PCM organized based on melting temperature and the latent energy of the materials.

122 citations

Journal ArticleDOI
TL;DR: In this paper, a solar powered jaggery industry with freeze pre-concentration is proposed with conventional and modified heating pans, which can mitigate nearly 2015.95 to 3062.15 tons of CO2 emission during its 25 years of lifespan under 300 clear days of operation each year.

17 citations

Journal ArticleDOI
TL;DR: In this article, a thermal energy storage tank size of 1m height and 0.250m diameter with a 0.030m size of filler material packed with an average porosity of 0.3 for the storage capacity of 150kWh/m3 is used for solar process heating applications.

14 citations

Journal ArticleDOI
TL;DR: In this article , the performance advantage of the packed bed PCM storage unit design is analyzed in comparison, and the impacts of key geometric parameters of a packed bed unit were numerically investigated.
Abstract: Heat transfer enhancement and optimization are found to be essential for the PCM (phase change material) thermal energy storage design. In this work, the performance advantage of the packed bed PCM storage unit design is analyzed in comparison, and the impacts of key geometric parameters of a packed bed unit were numerically investigated. The optimized shell-and-tube design, based on the hexagonal circle configuration, serves as the benchmark for the comparison. The thresholds of the bed and PCM-capsule diameter ratio,D/d, is found, above which the effective energy storage capacity of the packed bed would be higher than that of an optimal shell-and-tube unit. The threshold of D/d can be quantitatively correlated to the superficial velocity of the heat transfer fluid, providing a pathway for the tailored design of a packed bed PCM thermal storage system. In conclusion, it was found that packed bed units are advantageous due to their larger surface-to-volume ratio, in particular in large-scale applications. This work proposes a numerical analysis based framework to design packed bed PCM storage units in comparison with shell-and-tube units so that a proper type of PCM thermal storage design can be selected under a specific geometric and operational condition.

4 citations

References
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Journal ArticleDOI
TL;DR: In this paper, the thermal behavior of a packed bed of combined sensible and latent heat thermal energy storage (TES) unit with a constant temperature bath/solar collector is investigated.

357 citations

Journal ArticleDOI
TL;DR: In this article, a comprehensive, two-temperature model was developed to investigate energy storage in a molten-salt thermocline, where the volume-averaged mass and momentum equations were employed with the Brinkman-Forchheimer extension to the Darcy law used to model the porous medium resistance.

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Journal ArticleDOI
TL;DR: In this paper, a two-dimensional, two-phase model for heat transfer and fluid dynamics within the packed-bed molten salt thermocline thermal storage system is presented, which is used to investigate the general thermal behavior of a discharging process of the system and evaluate the interstitial heat transfer coefficient, the effective thermal conductivity and effect of the thermal conductivities of solid fillers.

210 citations

Journal ArticleDOI
TL;DR: Based on the well-known solution of Maxwell [1] for the thermal conductivity of dilute dispersions of spheres and the improved form of Maxwell's equation developed by Chiew and Glandt [2], two general correlation for keff estimation are proposed as discussed by the authors.

177 citations

Journal ArticleDOI
TL;DR: In this paper, a comprehensive model of a dual-medium thermocline tank that includes both the heterogeneous filler region as well as the composite tank wall is formulated, and the model accounts separately for the rock and molten-salt regions in view of their different thermal properties.

142 citations