Survey of Thermal Energy Storage for Parabolic Trough Power Plants

2002 ◽  
Vol 124 (2) ◽  
pp. 145-152 ◽  
Author(s):  
Ulf Herrmann ◽  
David W. Kearney
Keyword(s):  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Power Plants ◽  
Storage Capacity ◽  
State Of The Art ◽  
Storage System ◽  
Heat Transfer Fluid ◽  
Parabolic Trough ◽  
Tank Storage

A literature review was carried out to critically evaluate the state of the art of thermal energy storage applied to parabolic trough power plants. This survey briefly describes the work done before 1990 followed by a more detailed discussion of later efforts. The most advanced system is a 2-tank-storage system where the heat transfer fluid (HTF) also serves as storage medium. This concept was successfully demonstrated in a commercial trough plant (13.8MWe SEGS I plant; 120MWht storage capacity) and a demonstration tower plant (10MWe Solar Two; 105MWht storage capacity). However, the HTF used in state-of-the-art parabolic trough power plants 30-80MWe is expensive, dramatically increasing the cost of larger HTF storage systems. Other promising storage concepts are under development, such as concrete storage, phase change material storage, and chemical storage. These concepts promise a considerable cost reduction compared to the direct 2-tank system, but some additional R&D is required before those systems can be used in commercial solar power plants. An interesting and likely cost-effective near-term option for thermal energy storage for parabolic trough power plants is the use of an indirect 2-tank-storage, where another (less expensive) liquid medium such as molten salt is utilized rather than the HTF itself.

Assessment of Thermal Energy Storage for Parabolic Trough Solar Power Plants

Solar Energy ◽  
2004 ◽  
Author(s):  
David Kearney ◽  
Henry Price
Keyword(s):  
Energy Storage ◽  
Molten Salt ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Power Plants ◽  
Solar Power ◽  
Storage System ◽  
Parabolic Trough ◽  
Levelized Cost Of Electricity ◽  
Cost Of Electricity

Parabolic trough power plant technology is one of the most demonstrated solar power options commercially available. While trough power plants are the least expensive solar option, cost of electricity still exceeds that needed to directly compete with conventional fossil-fired large-scale central power technologies. Several evaluations have been done that identify a series of mechanisms for significant cost reduction over the next decade. One of the opportunities for improving the economics of parabolic trough plants is the development of lower cost and more efficient thermal energy storage (TES) technologies. This paper focuses on several of the TES technologies currently under development, namely: the use of an indirect molten-salt storage system, the use of molten-salt as a heat transfer fluid in the solar field and thermal energy storage system, and the development of new types of storage fluids. The assessment compares the cost and performance of these candidate thermal energy storage technologies by evaluating their impact on the levelized cost of electricity from the plant. This analysis is updated based on work conducted on these technologies during the last year.

scholarly journals Molten Nitrate Salt Development for Thermal Energy Storage in Parabolic Trough Solar Power Systems

2008 ◽  
Author(s):  
Robert W. Bradshaw ◽  
Nathan P. Siegel
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Molten Salt ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Power Plants ◽  
Heat Transfer Fluid ◽  
Working Fluid ◽  
Parabolic Trough ◽  
Heat Transfer Fluids

Thermal energy storage can enhance the utility of parabolic trough solar power plants by providing the ability to match electrical output to peak demand periods. An important component of thermal energy storage system optimization is selecting the working fluid used as the storage media and/or heat transfer fluid. Large quantities of the working fluid are required for power plants at the scale of 100-MW, so maximizing heat transfer fluid performance while minimizing material cost is important. This paper reports recent developments of multi-component molten salt formulations consisting of common alkali nitrate and alkaline earth nitrate salts that have advantageous properties for applications as heat transfer fluids in parabolic trough systems. A primary disadvantage of molten salt heat transfer fluids is relatively high freeze-onset temperature compared to organic heat transfer oil. Experimental results are reported for formulations of inorganic molten salt mixtures that display freeze-onset temperatures below 100°C. In addition to phase-change behavior, several properties of these molten salts that significantly affect their suitability as thermal energy storage fluids were evaluated, including chemical stability and viscosity. These alternative molten salts have demonstrated chemical stability in the presence of air up to approximately 500°C in laboratory testing and display chemical equilibrium behavior similar to Solar Salt. The capability to operate at temperatures up to 500°C may allow an increase in maximum temperature operating capability vs. organic fluids in existing trough systems and will enable increased power cycle efficiency. Experimental measurements of viscosity were performed from near the freeze-onset temperature to about 200°C. Viscosities can exceed 100 cP at the lowest temperature but are less than 10 cP in the primary temperature range at which the mixtures would be used in a thermal energy storage system. Quantitative cost figures of constituent salts and blends are not currently available, although, these molten salt mixtures are expected to be inexpensive compared to synthetic organic heat transfer fluids. Experiments are in progress to confirm that the corrosion behavior of readily available alloys is satisfactory for long-term use.

Computational Analysis of a Pipe Flow Distributor for a Thermocline Based Thermal Energy Storage System

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Samia Afrin ◽  
Vinod Kumar ◽  
Desikan Bharathan ◽  
Greg C. Glatzmaier ◽  
Zhiwen Ma
Keyword(s):  
Energy Storage ◽  
Molten Salt ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Computational Analysis ◽  
Storage System ◽  
Flow Distribution ◽  
Energy Storage System ◽  
Heat Transfer Fluid ◽  
Case Scenario

The overall efficiency of a concentrating solar power (CSP) plant depends on the effectiveness of thermal energy storage (TES) system (Kearney and Herrmann, 2002, “Assessment of a Molten Salt Heat Transfer Fluid,” ASME). A single tank TES system consists of a thermocline region which produces the temperature gradient between hot and cold storage fluid by density difference (Energy Efficiency and Renewable Energy, http://www.eere.energy.gov/basics/renewable_energy/thermal_storage.html). Preservation of this thermocline region in the tank during charging and discharging cycles depends on the uniformity of the velocity profile at any horizontal plane. Our objective is to maximize the uniformity of the velocity distribution using a pipe-network distributor by varying the number of holes, distance between the holes, position of the holes and number of distributor pipes. For simplicity, we consider that the diameter of the inlet, main pipe, the distributor pipes and the height and the width of the tank are constant. We use Hitec® molten salt as the storage medium and the commercial software Gambit 2.4.6 and Fluent 6.3 for the computational analysis. We analyze the standard deviation in the velocity field and compare the deviations at different positions of the tank height for different configurations. Since the distance of the holes from the inlet and their respective arrangements affects the flow distribution throughout the tank; we investigate the impacts of rearranging the holes position on flow distribution. Impact of the number of holes and distributor pipes are also analyzed. We analyze our findings to determine a configuration for the best case scenario.

scholarly journals Review of solid particle materials for heat transfer fluid and thermal energy storage in solar thermal power plants

2019 ◽  
Vol 1 (4) ◽  
Author(s):  
Alejandro Calderón ◽  
Camila Barreneche ◽  
Anabel Palacios ◽  
Mercè Segarra ◽  
Cristina Prieto ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Solid Particle ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Power Plants ◽  
Thermal Power ◽  
Heat Transfer Fluid ◽  
Thermal Power Plants ◽  
Solar Thermal Power

Numerical Study of Thermochemical Storage Using Ca(OH)2/CaO: High Temperature Applications

2016 ◽  
Author(s):  
Qasim A. Ranjha ◽  
Nasser Vahedi ◽  
Alparslan Oztekin
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Numerical Study ◽  
Storage System ◽  
Packed Bed ◽  
Heat Transfer Fluid ◽  
Operational Parameters ◽  
Storage And Retrieval

Thermal energy storage by reversible gas-solid reaction has been selected as a thermochemical energy storage system. Simulations are conducted to investigate the dehydration of Ca(OH)2 and the hydration of CaO for thermal energy storage and retrieval, respectively. The rectangular packed bed is heated indirectly by air used as a heat transfer fluid (HTF) while the steam is transferred through the upper side of the bed. Transient mass transport and heat transfer equations coupled with chemical kinetics equations for a two dimensional geometry have been solved using finite element method. Numerical results have been validated by comparing against results of previous measurements and simulations. The effect of geometrical and operational parameters including the material properties on overall storage and retrieval process has been investigated. The co-current and counter-current flow arrangements for steam and heat transfer fluid have been considered.

Exergy-Based Optimization of Sub- and Supercritical Thermal Energy Storage Systems

2014 ◽  
Author(s):  
Louis A. Tse ◽  
Reza Baghaei Lakeh ◽  
Richard E. Wirz ◽  
Adrienne S. Lavine
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage System ◽  
Heat Transfer Fluid ◽  
Energy And Exergy

In this work, energy and exergy analyses are applied to a thermal energy storage system employing a storage medium in the two-phase or supercritical regime. First, a numerical model is developed to investigate the transient thermodynamic and heat transfer characteristics of the storage system by coupling conservation of energy with an equation of state to model the spatial and temporal variations in fluid properties during the entire working cycle of the TES tank. Second, parametric studies are conducted to determine the impact of key variables (such as heat transfer fluid mass flow rate and maximum storage temperature) on both energy and exergy efficiencies. The optimum heat transfer fluid mass flow rate during charging must balance exergy destroyed due to heat transfer and exergy destroyed due to pressure losses, which have competing effects. Similarly, the optimum maximum storage fluid temperature is evaluated to optimize exergetic efficiency. By incorporating exergy-based optimization alongside traditional energy analyses, the results of this study evaluate the optimal values for key parameters in the design and operation of TES systems, as well as highlight opportunities to minimize thermodynamic losses.

Numerical Analysis of Total Energy Storage of Nanofluidized Heat Transfer Fluid in Thermocline Thermal Energy Storage System

2014 ◽  
Author(s):  
Nazmul Hossain ◽  
Samia Afrin ◽  
Jesus D. Ortega ◽  
Vinod Kumar ◽  
Debjyoti Banerjee
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Base Fluid ◽  
Storage Capacity ◽  
Effective Properties ◽  
Heat Transfer Fluid ◽  
Cylindrical Tank ◽  
Thermo Physical Properties

Thermal energy storage (TES), when combined with a concentrating solar power (CSP) plant has potential to produce electricity at a cost-competitive rate to traditional sources of electricity production. In single tank TES system both the hot fluid and cold fluid settle in the same tank. The region of contact of these two fluids is called thermocline. Preservation of this thermocline region in the cylindrical tank during charging and discharging cycles depends on the uniformity of the velocity profile at any horizontal plane. So to maintain this thermocline region, a pipe flow distributor was placed near the inlet and outlet of the cylindrical tank. To optimize the efficiency of this single tank TES system is to increase the thermo-physical properties of heat transfer fluid. This addition will result in harnessing solar energy by increasing thermal efficiency of the thermodynamic cycles. Adding of nanoparticles, in the heat transfer fluid give rise of this thermo-physical properties i.e. thermal conductivity (k) and specific heat capacity (Cp). Hitec® molten salt is used as the base-fluid and synthesized with five different types of nanoparticles (SiO2, Al2O3, Fe3O4, ZnO and Ag) with different concentrations. The values of effective k and Cp are calculated for the new Hitec® nanofluid. The doping of nano-particles results in higher k and Cp when compared to the base fluid. Higher Cp is expected to improve the thermal storage capacity but higher value of k is expected to increase the thermal diffusivity, thereby affecting the performance of the thermocline. The diffusivity depends on the ratio of k to Cp and density of the effective properties. So there is a need to balance the effective properties to improve thermal storage performance. The total energy storage capacity is then checked by finite volume based computational fluid dynamics software. The simulation shows how the performance of the nanofluid changes at different concentrations in a single tank TES system during its charging-discharging cycle.

scholarly journals Experimental Investigation of PCM Spheres in Thermal Energy Storage System

2013 ◽  
Vol 367 ◽  
pp. 228-233 ◽  
Author(s):  
N.A.M. Amin ◽  
Azizul Mohamad ◽  
M.S. Abdul Majid ◽  
Mohd Afendi ◽  
Frank Bruno ◽  
...  
Keyword(s):  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage System ◽  
Packed Bed ◽  
Energy Storage System ◽  
Heat Transfer Fluid ◽  
Experimental Result ◽  
Small Scale ◽  
Storage Unit

This paper presents the experimental result of a small scale packed bed of random spheres with encapsulated PCM being charged and discharged. A vapor compression refrigerator and heated room with fan heater were used to supply constant heat transfer fluid at a minimum temperature of -28°C for charging and 16°C for discharging. Even though the temperature differences were not fixed in the experiments, the performance of the thermal energy storage is depicted in the form of effectiveness values. Different results were obtained for charging and discharging the thermal storage unit. The differences are expected to come from natural convection and super cooling. The super cooling during the charging process was as high as 6°C.

Experimental Study of Thermal Energy Storage Using Natural Porous Media

2017 ◽  
Author(s):  
A. J. Al Edhari ◽  
C. C. Ngo
Keyword(s):  
Experimental Study ◽  
Porous Media ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage System ◽  
Thermal Storage ◽  
Heat Transfer Fluid ◽  
Storage Unit ◽  
Storage Media

Thermal energy storage has been an area of research interest due to the need to store solar energy or excess energy for later use in many applications including district heating. The focus of a lot of research is on exotic and expensive storage media. This paper presents an experimental study of thermal energy storage using porous media readily available and commonly found in nature such as sand, soil, pebble rocks and gravel. This study also considers a simple and inexpensive thermal storage system which could be constructed easily and examines what could be done to increase the thermal storage performance. The thermal storage system examined in the present study was a thermal energy storage unit with embedded horizontal pipes carrying water as the heat transfer fluid for thermal charging. Different thermal storage configurations were examined by adjusting the thermal charging temperature and using different storage media. The temperature distribution within the storage media was monitored for 10 hours using a data acquisition system with K-type thermocouples. The results indicate that a thermal storage system using sand as storage media is slightly better compared with gravel or pebble rocks as storage media.

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