Enhancement of latent heat energy storage using embedded heat pipes

Robak, Christopher; Bergman, T. L.; Faghri, Amir

doi:10.1016/j.ijheatmasstransfer.2011.03.038

Cited by 188 publications

(39 citation statements)

References 16 publications

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“…25b) induces intermediate melting rates, where warm temperatures have not yet propagated extensively to the upper sections of the rod for t = 0.5 h. The melt region topographies are similar to those of the heat pipe at later times (t = 7 h) during which the rod is more uniformly-warm. The predictions are in qualitative agreement with experimental measurements of heat pipe-and rod-assisted PCM melting [60]. The temporal variations of the liquid PCM fraction are shown in Fig.…”

Section: De-fg36-08go18146 Research and Development For Novel Tes Syssupporting

confidence: 84%

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Research and Development for Novel Thermal Energy Storage Systems (TES) for Concentrating Solar Power (CSP)

Faghri¹,

Bergman²,

Pitchumani³

2013

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Executive Summary:The overall objective was to develop innovative heat transfer devices and methodologies for novel thermal energy storage systems for concentrating solar power generation involving phase change materials (PCMs). Specific objectives included embedding thermosyphons and/or heat pipes (TS/HPs) within appropriate phase change materials to significantly reduce thermal resistances within the thermal energy storage system of a large-scale concentrating solar power plant and, in turn, improve performance of the plant. Experimental, system level and detailed comprehensive modeling approaches were taken to investigate the effect of adding TS/HPs on the performance of latent heat thermal energy storage (LHTES) systems. Experimental results proved the superior performance of HPs to increase the heat transfer rates compared to finned and non-finned cases. Quantitatively, inclusion of heat pipes increased PCM melting rates by approximately 60%, while the fins were not as effective. During solidification, the heat pipe-assisted configuration transferred approximately twice the energy between a heat transfer fluid and the PCM, relative to both the fin-assisted LHTES and the non-heat pipe, non-fin configurations.Comprehensive multiphase multi-dimensional simulations were conducted to provide a better understanding of the fundamental physical phenomena involved in thermal energy storage in a phase change media with embedded TS/HPs, and also to provide input for the system level model. A system level model, leveraged by the input from the comprehensive model, was developed to predict the response of large-scale TS/HP-assisted LHTES systems in a computationally-effective manner. Consistent with the experimental results, the results of the system level model also demonstrated a significant increase in heat transfer rates associated with HP-assisted LHTES systems.The developed system level model was employed to predict the performance of a large-scale LHTES system utilizing multiple PCMs in a cascaded configuration. It was shown that the maximum exergy recovery can be achieved by using a cascaded configuration. Optimization studies were performed using the system level model and the preferred configurations of HPs in the LHTES systems were identified. Exergy analysis of LHTES systems was carried out considering the practical constraints imposed on the system in solar applications. Novel guidelines were proposed for design and optimization of LHTES systems for solar applications. Economic aspects of TS/HPassisted LHTES systems were also investigated and it was shown that these systems are cost competitive with the state of the art thermal energy storage systems currently in use. DE-FG36-08GO18146Research and Development for Novel TES Systems for CSP University of Connecticut 3 Background:Energy storage capability is desirable in solar and wind electric power applications due to the intermittent nature of the energy generated. In solar thermal generation, thermal energy storage is the preferred energy storage mode [1]...

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Section: De-fg36-08go18146 Research and Development For Novel Tes Syssupporting

confidence: 84%

“…Experimental: Robak et al [60] experimentally investigated latent heat thermal energy storage utilizing heat pipes or fins. Photographic observations, melting and solidification rates, and PCM energy storage quantities are reported.…”

Section: Project Results and Discussionmentioning

confidence: 99%

Research and Development for Novel Thermal Energy Storage Systems (TES) for Concentrating Solar Power (CSP)

Faghri¹,

Bergman²,

Pitchumani³

2013

Self Cite

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“…Motahar and Khodabandeh [33] reported improvements in the melting and solidification rates of a cylindrical PCM by utilizing heat pipes. An increase of 70% for the melting rate of a PCM with embedded heat pipes was reported by Robak et al [34]. Shabgard et al [35] investigated the impact of heat pipes on two configurations of PCM-based TES; one where the PCM surrounds tubes through which the heat transfer fluid (HTF) flows, and the second where the HTF cross-flows over tubes of encapsulated PCM.…”

Section: Introductionmentioning

confidence: 92%

Development of an Integrated Thermal Energy Storage and Free-Piston Stirling Generator for a Concentrating Solar Power System

2017

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Incorporating thermal energy storage (TES) into a concentrating solar power (CSP) system extends the power production hours, eliminating intermittency and reducing the Levelized Cost of the Energy (LCOE). The designed TES system was integrated with a 3 kW free-piston Stirling convertor. A NaF-NaCl eutectic salt was chosen as the phase change material (PCM) with a melting temperature of 680 • C. This eutectic salt has an energy density that is 5 to 10 times that of a typical molten salt PCM. In order to overcome the drawbacks of the material having a low thermal conductivity, heat pipes were embedded into the PCM to enhance the heat transfer rate within the system. Since the dish collector tracks the sun over the course of the day, two operational extremes were tested on the system; horizontal (zero solar elevation at sunrise/sunset) and vertical (solar noon). Although the system's performance was below the expectations due to improperly sized wicks in the secondary heat pipes, the results indicated that the Stirling engine was able to produce 1.3 kWh of electricity by extracting latent heat energy from the PCM; thus, the concept of the design was validated.

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“…By testing it numerically, improvements in design may be made quickly and cheaply and by understanding the flow phenomena inside the storage container, a more accurate representation can be set-up numerically. Robak et al argues that small laboratory scale tests may be built and analysed with lower melting temperature PCMs before larger systems are constructed and tested at higher temperatures for commercial viability [8]. This may aid initial design decisions and improve geometry layout for a particular application.…”

Section: Literature Studymentioning

confidence: 99%

Solar Thermal Energy Storage in Power Generation Using Phase Change Material with Heat Pipes and Fins to Enhance Heat Transfer

2015

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Phase change materials absorb or otherwise release heat at close to a constant temperature during its melting and solidification phases. This is a very sought after property in power generation, where a high temperature heat source is required within a narrow temperature range as heat input for the turbine. Solar tower technology provides a high temperature heat source, but unfortunately it is time dependent. A sufficient amount of this heat may be stored in a phase change storage system which can deliver dispatchable heat. In such a storage system the phase change material needs to be exposed to a sufficient heat transfer area to melt or solidify at sufficient rates. In this study this is achieved with heat pipes with metallic fins. The analysis of this design included testing an experimental module during heat absorption and heat removal cycles, as well as a numerical analysis to model the storage module. To determine the parameters for a specific phase change storage system in a high temperature solar tower application the validated numerical thermal response simulation is incorporated. Certain solar input conditions and load cases are applied to the phase change storage system model and the size and geometry of the solar thermal storage system are determined from this analysis.

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Enhancement of latent heat energy storage using embedded heat pipes

Cited by 188 publications

References 16 publications

Research and Development for Novel Thermal Energy Storage Systems (TES) for Concentrating Solar Power (CSP)

Research and Development for Novel Thermal Energy Storage Systems (TES) for Concentrating Solar Power (CSP)

Development of an Integrated Thermal Energy Storage and Free-Piston Stirling Generator for a Concentrating Solar Power System

Solar Thermal Energy Storage in Power Generation Using Phase Change Material with Heat Pipes and Fins to Enhance Heat Transfer

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