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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 exact size of the vessel and insulation layers and the shape of the roof are optimized by minimizing the total investment cost of the storage system under three technical constraints: remaining within the maximum allowable values of both temperature and stress in the steel structure, and avoiding excessive cooling and consequent solidification of the molten salt during long periods of no solar input.
Abstract: This paper presents an optimal design procedure for internally insulated, carbon steel, molten salt thermal storage tanks for parabolic trough solar power plants. The exact size of the vessel and insulation layers and the shape of the roof are optimized by minimizing the total investment cost of the storage system under three technical constraints: remaining within the maximum allowable values of both temperature and stress in the steel structure, and avoiding excessive cooling and consequent solidification of the molten salt during long periods of no solar input. The thermal, mechanical and economic aspects have been integrated into an iterative step-by-step optimization procedure, which is shown to be effective through application to the case study of a 600 MW h thermal storage system. The optimal design turns out to be an internally insulated, carbon steel storage tank characterized by a maximum allowable height of 11 m and a diameter of 22.4 m. The total investment cost is about 20% lower than that of a corresponding AISI 321H stainless steel storage tank without internal protection or insulation.

81 citations

Journal ArticleDOI
TL;DR: In this paper, a series of well-configured general charts bearing curves of energy storage effectiveness against four dimensionless parameters grouped up from the storage tank dimensions, properties of the fluid and filler material, and operational conditions (such as mass flow rate of fluid and energy charge and discharge periods).

74 citations

Journal ArticleDOI
TL;DR: In this article, a thermal energy storage (TES) system for a concentrated solar power (CSP) plant with the dimensions and operating conditions of a parabolic trough plant was designed.

58 citations

Journal ArticleDOI
TL;DR: In this article, the effect of porosity on discharge effectiveness of the storage tank with different commercially available Heat Transfer Fluids (HTFs) is investigated with porosity, e varied from 0.1 to 0.7 for all the HTFs.

43 citations

Journal ArticleDOI
TL;DR: In this article, a new numerical simulation platform has been developed to evaluate the thermal and mechanical response of a thermocline tank for concentrated solar power plants compared with the commonly-built two-tank system.

29 citations