K. Nithyanandam

ANALYSIS OF A LATENT THERMOCLINE ENERGY STORAGE SYSTEM FOR CONCENTRATING SOLAR POWER PLANTS

The primary purpose of a thermal energy storage system in a concentrating solar power (CSP) plant is to extend the operation of plant at times when energy from the sun is not adequate by dispatching its stored energy. Storing sun’s energy in the form of latent thermal energy of a phase change material (PCM) is desirable due to its high energy storage density which translates to less amount of salt required for a given storage capacity. The objective of this paper is to analyze the dynamic behavior of a packed bed encapsulated PCM energy storage subjected to partial charging and discharging cycles, and constraints on charge and discharge temperatures as encountered in a CSP plant operation. A transient, numerical analysis of a molten salt, single tank latent thermocline energy storage system (LTES) is performed for repeated charging and discharging cycles to investigate its dynamic response. The influence of the design configuration and operating parameters on the dynamic storage and delivery performance of the system is analyzed to identify configurations that lead to higher utilization. This study provides important guidelines for designing a storage tank with encapsulated PCM for a CSP plant operation.Copyright

Design and Analysis of Metal Foam Enhanced Latent Thermal Energy Storage With Embedded Heat Pipes for Concentrating Solar Power Plants

Thermal energy Storage is a critical component of Concentrating Solar Power (CSP) plant, enabling uninterrupted operation of plant during periods of cloudy or intermittent solar weather. Investigations of Latent Thermal Energy Storage (LTES) which utilizes Phase Change Material (PCM) as a heat storage medium is considered due to its high energy storage density and low capital cost. However, the low thermal conductivity of the PCM restricts the solidification rate of the PCM leading to inefficient heat transfer between the PCM and the HTF which carries thermal energy to the power block. To address this, LTES embedded with heat pipes and PCM’s stored within the framework of porous metal foams possessing one to two orders of magnitude higher thermal conductivity than the PCM are considered in the present study. A transient, computational analysis of the metal foam (MF) enhanced LTES system with embedded heat pipes is performed to investigate the enhancement in the thermal performance of the system for different arrangement of heat pipes and design parameter of metal foams, during both charging and discharging operation.Copyright

Numerical Analysis of Latent Thermal Energy Storage System With Embedded Thermosyphons

Latent thermal energy storage (LTES) system offers high energy storage density and nearly isothermal operation for concentrating solar power generation. However, the low thermal conductivity possessed by the phase change material (PCM) used in LTES system limits the heat transfer rates. Utilizing thermosyphons to charge or discharge a LTES system offers a promising engineering solution to compensate for the low thermal conductivity of the PCM. The present work numerically investigates the enhancement in the thermal performance of charging and discharging process of LTES system by embedding thermosyphons. A transient, computational analysis of the LTES system with embedded thermosyphons is performed for both charging and discharging cycles. The influence of the design configuration of the system and the arrangement of the thermosyphons on the charge and discharge performance of the LTES installed in a concentrating solar power plant (CSP) is analyzed to identify configurations that lead to improved effectiveness.Copyright

COMPUTATIONAL MODELING OF LATENT THERMAL ENERGY STORAGE SYSTEM WITH EMBEDDED HEAT PIPES

Due to the intermittent nature of solar energy availability, storing sun’s energy in the form of latent thermal energy of a phase change material (PCM) is an effective technique that is widely used in energy storage and load management applications. In a Latent Thermal Energy Storage System (LTES), a heat transfer fluid (HTF) exchanges energy with a PCM. The advantages of an LTES include its isothermal operation and high energy storage density. However, the low thermal conductivity of PCM poses a significant disadvantage due to reduction in the rate at which the PCM can be melted (charging) or solidified (discharging). This paper explores an approach to reducing the thermal resistance of PCM in a LTES through embedded heat pipes. A heat pipe is a passive heat transfer device that efficiently transfers large amount of energy between the PCM and HTF thus indirectly amplifying the effective thermal conductivity of PCM. A transient computational analysis of a shell and tube LTES embedded with heat pipes is performed for charging to determine the position of melt front and energy stored as a function of time. The influence of the number and orientation of heat pipes and design configuration of the system is analyzed to identify configurations that lead to improved effectiveness.Copyright

Analysis and Design of Dye Sensitized Solar Cells

Dye sensitized solar cells (DSC) are an attractive alternative to the conventional photovoltaic cell because of their low cost electricity production from solar radiation. The advantages of a DSC include the ability to generate power without emitting pollutants and requiring no fuel. While modeling of the physical and transport phenomena in DSC has been widely reported in the literature, a thorough analysis to quantitatively determine the optimal design and operating configuration in installation is lacking. The present study incorporates a model of the DSC coupled with a model to predict global irradiance on a terrestrial surface to analyze the hourly, daily, monthly and annual performance of a DSC installation over a wide range of design and operating parameters. Optimum design and operating parameters are derived from the analysis.Copyright

Techno-Economic Analysis of Concentrating Solar Power Plants With Integrated Latent Thermal Storage Systems

Integrating a thermal energy storage (TES) in a concentrating solar power (CSP) plant allows for continuous operation even during times when solar radiation is not available, thus providing a reliable output to the grid. In the present study, the cost and performance models of an encapsulated phase change material thermocline storage system are integrated with a CSP power tower system model to investigate its dynamic performance. The influence of design parameters of the storage system is studied for different solar multiples of the plant to establish design envelopes that satisfy the U.S. Department of Energy SunShot Initiative requirements, which include a round-trip exergetic efficiency greater than 95% and storage cost less than

Computational Modeling of Dynamic Response of a Latent Thermal Energy Storage System With Embedded Heat Pipes

15/kWht for a minimum discharge period of 6 hours. From the design windows, optimum designs of the storage system based on minimum LCOE, maximum exergetic efficiency, and maximum capacity factor are reported and compared with the results of two-tank molten salt storage system. Overall, this study presents the first effort to construct a latent thermal energy storage (LTES)-integrated CSP plant model, that can help decision makers in assessing the impact, cost and performance of a latent thermocline energy storage system on power generation from molten salt power tower CSP plant.Copyright

Analysis and optimization of a latent thermal energy storage system with embedded heat pipes

Concentrated solar power plants (CSP) are being explored as the leading source of renewable energy for future power generation. Storing sun’s energy in the form of latent thermal energy of a phase change material (PCM) is desirable for use on demand including times when solar energy is unavailable. Considering a latent thermal energy storage (LTES) system incorporating heat pipes to enhance heat transfer between the heat transfer fluid (HTF) and the PCM, this paper explores the dynamic response of the LTES system subjected to repeated cycles of charging and discharging. A transient computational analysis of a shell-and-tube LTES embedded with two horizontal heat pipes (HHP) is performed for repeated charging and discharging of the PCM to analyze the dynamic performance of the LTES and the augmentation in the cyclic performance of the LTES embedded with heat pipes is investigated. A model low temperature phase change material system is considered in the present study, with the physical results being scalable to high temperature systems used in CSP plants.Copyright