Testing of High-Performance Concrete as a Thermal Energy Storage Medium at High Temperatures

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Joel E. Skinner ◽  
Matthew N. Strasser ◽  
Brad M. Brown ◽  
R. Panneer Selvam
Keyword(s):  
Heat Transfer ◽  
Stainless Steel ◽  
Energy Storage ◽  
Heat Exchanger ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
High Performance Concrete ◽  
Thermal Strain ◽  
Heat Transfer Fluid ◽  
Interface Materials

Concrete is tested as a sensible heat thermal energy storage (TES) material in the temperature range of 400–500 °C (752–932 °F). A molten nitrate salt is used as the heat transfer fluid (HTF); the HTF is circulated though stainless steel heat exchangers, imbedded in concrete test prisms, to charge the TES system. During charging, significant cracking occurs in both the radial and longitudinal directions in the concrete prisms. The cracking is due to hoop stress induced by the dissimilar thermal strain rates of concrete and stainless steel. A 2D finite element model (FEM) is developed and used to study the stress at the prism/exchanger interface. Polytetrafluoroethylene (PTFE) and a heat-curing, fibered paste (HCFP) are tested as interface materials to mitigate the stress in the concrete. Significant reduction in the size and number of cracks is observed after incorporating interface materials. A heat exchanger with a helical fin configuration is incorporated to improve the heat transfer rate in the concrete. Testing confirms that the fins increase the rate of heat transfer in the concrete; however, large cracks form at each of the fin locations. Only the HCFP is tested as an interface material for the finned heat exchanger. The HCFP decreases the number and size of the cracks, however, not to the desired hairline levels.

Testing of High Performance Concrete as a Thermal Energy Storage Medium at High Temperatures

2011 ◽  
Author(s):  
Joel E. Skinner ◽  
Brad M. Brown ◽  
R. Panneer Selvam
Keyword(s):  
Heat Transfer ◽  
Stainless Steel ◽  
Energy Storage ◽  
Heat Exchanger ◽  
High Performance ◽  
Fossil Fuels ◽  
High Performance Concrete ◽  
Aluminum Foil ◽  
Interface Materials ◽  
Steel Heat

In recent years, the mission to become energy independent from fossil fuels has become a higher priority. Solar energy is an ideal solution because it does not have the environmental impact of the fossil fuels. One key to the transition to solar energy is improved energy storage for when collection is prohibited by weather variation and during nighttime hours. Concrete has a low material cost and is reported to be $1/kWhthermal [1]. Concrete as a sensible heat thermal energy storage material has been tested to temperatures of 390°C with an embedded steel heat exchanger using synthetic oil as a heat transfer fluid [2]. The energy storage efficiency of concrete can be improved by raising the maximum charging temperature. This paper reports the testing to further the peak temperature to 450–500°C by using high performance concrete developed by the University of Arkansas. A molten nitrate salt was selected along with stainless steel heat exchanger. The testing is of a laboratory scale with a single 3/4 inch pipe imbedded in a 4 inch by 4 inch concrete cross section. During testing, the differences in the materials’ thermal expansion produce stress at the pipe/concrete interaction zone. After testing with no interface material, the high tensile stress in the concrete caused large radial and longitudinal tension cracks that would hinder adequate heat transfer. Three interface materials between the concrete and stainless steel pipe were tested: Teflon© tape, Deacon 8875, and aluminum foil. For Teflon tape and Deacon 8875, the concrete stress was minimized and produced only small micro-cracks. To improve the heat transfer in the concrete, testing of a pipe with radial fins was conducted. The pipe consisted of a continuous helicoidal, auger style. During testing, large cracks occurred at each of the fin locations which demonstrated the need for a stress reducing material. Yet, only Deacon 8875 and aluminum foil were able to be applied to the unique radial fins. The results of the testing are reported and compared in the article. The Teflon® tape had the fastest heat transfer of all the interface materials. Testing was considered a success on a single tube laboratory scale. Future multiple tube testing is a viable option.

Effect of High Temperatures and Heating Rates on High Strength Concrete for Use as Thermal Energy Storage

2010 ◽  
Author(s):  
Emerson E. John ◽  
W. Micah Hale ◽  
R. Panneer Selvam
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Molten Salt ◽  
High Temperatures ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Heat Transfer Fluid ◽  
Heating Rates ◽  
Storage Media ◽  
Concrete Mixtures

In recent years due to rising energy costs as well as an increased interest in the reduction of greenhouse gas emissions, there is great interest in developing alternative sources of energy. One of the most viable alternative energy resources is solar energy. Concentrating solar power (CSP) technologies have been identified as an option for meeting utility needs in the U.S. Southwest. Areas where CSP technologies can be improved are improved heat transfer fluid (HTF) and improved methods of thermal energy storage (TES). One viable option for TES storage media is concrete. The material costs of concrete can be very inexpensive and the costs/ kWhthermal, which is based on the operating temperature, are reported to be approximately $1. Researchers using concrete as a TES storage media have achieved maximum operating temperatures of 400°C. However, there are concerns for using concrete as the TES medium, and these concerns center on the effects and the limitations that the high temperatures may have on the concrete. As the concrete temperature increases, decomposition of the calcium hydroxide (CH) occurs at 500°C, and there is significant strength loss due to degeneration of the calcium silicate hydrates (C-S-H). Additionally concrete exposed to high temperatures has a propensity to spall explosively. This proposed paper examines the effect of heating rates on high performance concrete mixtures. Concrete mixtures with water to cementitious material ratios (w/cm) of 0.15 to 0.30 and compressive strengths of up to 180 MPa (26 ksi) were cast and subjected to heating rates of 3, 5, 7, and 9° C/min. These concrete mixtures are to be used in tests modules where molten salt is used as the heat transfer fluid. Molten salt becomes liquid at temperatures exceeding 220°C and therefore the concrete will be exposed to high initial temperatures and subsequently at controlled heating rates up to desired operating temperatures. Preliminary results consistently show that concrete mixtures without polypropylene fibres (PP) cannot resist temperatures beyond 500° C, regardless of the heating rate employed. These mixtures spall at higher temperatures when heated at a faster rate (7° C/min). Additionally, mixtures which incorporate PP fibres can withstand temperatures up to 600° C without spalling irrespective of the heating rate.

scholarly journals Performance Evaluation of a Small-Scale Latent Heat Thermal Energy Storage Unit for Heating Applications Based on a Nanocomposite Organic PCM

2019 ◽  
Vol 3 (4) ◽  
pp. 88 ◽  
Author(s):  
Maria K. Koukou ◽  
George Dogkas ◽  
Michail Gr. Vrachopoulos ◽  
John Konstantaras ◽  
Christos Pagkalos ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Thermal Behavior ◽  
Latent Heat ◽  
Flow Rate ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Heat Transfer Fluid ◽  
Small Scale ◽  
Solidification Processes

A small-scale latent heat thermal energy storage (LHTES) unit for heating applications was studied experimentally using an organic phase change material (PCM). The unit comprised of a tank filled with the PCM, a staggered heat exchanger (HE) for transferring heat from and to the PCM, and a water pump to circulate water as a heat transfer fluid (HTF). The performance of the unit using the commercial organic paraffin A44 was studied in order to understand the thermal behavior of the system and the main parameters that influence heat transfer during the PCM melting and solidification processes. The latter will assist the design of a large-scale unit. The effect of flow rate was studied given that it significantly affects charging (melting) and discharging (solidification) processes. In addition, as organic PCMs have low thermal conductivity, the possible improvement of the PCM’s thermal behavior by means of nanoparticle addition was investigated. The obtained results were promising and showed that the use of graphite-based nanoplatelets improves the PCM thermal behavior. Charging was clearly faster and more efficient, while with the appropriate tuning of the HTF flow rate, an efficient discharging was accomplished.

scholarly journals Testing the performance of a prototype thermal energy storage tank working with organic phase change material for space heating application conditions

2019 ◽  
Vol 116 ◽  
pp. 00038 ◽  
Author(s):  
Maria K. Koukou ◽  
Michail Gr. Vrachopoulos ◽  
George Dogkas ◽  
Christos Pagkalos ◽  
Kostas Lymperis ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Phase Change ◽  
Phase Change Material ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Finned Tube ◽  
Heat Transfer Fluid ◽  
Outlet Temperature ◽  
Change Material

A prototype Latent Heat Thermal Energy Storage (LHTES) unit has been designed, constructed, and experimentally analysed for its thermal storage performance under different operational conditions considering heating application and exploiting solar and geothermal energy. The system consists of a rectangular tank filled with Phase Change Material (PCM) and a finned tube staggered Heat Exchanger (HE) while water is used as Heat Transfer Fluid (HTF). Different HTF inlet temperatures and flow rates were tested to find out their effects on LHTES performance. Thermal quantities such as HTF outlet temperature, heat transfer rate, stored energy, were evaluated as a function of the conditions studied. Two commercial organic PCMs were tested A44 and A46. Results indicate that A44 is more efficient during the charging period, taking into account the two energy sources, solar and heat pump. During the discharging process, it exhibits higher storage capacity than A46. Concluding, the developed methodology can be applied to study different PCMs and building applications.

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.

Performance Based Cost Modeling of Phase Change Thermal Energy Storage for High Temperature Concentrating Solar Power Systems

2009 ◽  
Author(s):  
Russell Muren ◽  
Diego A. Arias ◽  
Brian Luptowski
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Phase Change ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Heat Transfer Fluid ◽  
Energy Output ◽  
System Component ◽  
Precipitate Formation ◽  
The Cost

Sizing and cost models were developed for thermal energy storage (TES) systems utilizing cascaded phase change materials (PCM) as the storage media in a variety of configurations. The sizing model is based on an energy balance around a characteristic fundamental element of the system, consisting of a steel pipe embedded in a matrix of phase change material. Due to the transient behavior PCM system, the sizing model requires time and space integrations. The model accounts for decreases in thermal performance caused by precipitate formation on the surface of the pipe and predicts the resulting transient power output. The model calculates the required tank and pipe sizes, the amounts of heat transfer fluid and PCM, as well as the land area for the configuration. Using a cost metric approach, the cost of each system component is estimated. Furthermore, the effect of several technological pitfalls, including: pinch point heat transfer, precipitate buildup, and transient energy output have been investigated. Prices are shown to depend heavily on system configuration. Specifically, prices are shown to be most dependent on precipitate formation during discharge and consequently the size of the necessary heat transfer area of heat exchangers. The cost of different configurations vary from $40/kWh to $100/kWh.

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.

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