High-Temperature Liquid-Fluoride-Salt Closed-Brayton-Cycle Solar Power Towers

2006 ◽  
Vol 129 (2) ◽  
pp. 141-146 ◽  
Author(s):  
Charles W. Forsberg ◽  
Per F. Peterson ◽  
Haihua Zhao
Keyword(s):  
High Temperature ◽  
High Temperatures ◽  
Solar Power ◽  
Heat Storage ◽  
Solar Furnace ◽  
Working Fluid ◽  
Fluoride Salt ◽  
Power Cycle ◽  
Solar Power Tower ◽  
The Cost

Liquid-fluoride-salt heat transfer fluids are proposed to raise the heat-to-electricity efficiencies of solar power towers to about 50%. The liquid salt would deliver heat from the solar furnace at temperatures between 700°C and 850°C to a closed multireheat Brayton power cycle using nitrogen or helium as the working fluid. During the daytime, hot salt may also be used to heat graphite, which would then be used as a heat storage medium to make night-time operations possible. Graphite is a low-cost high-heat-capacity solid that is chemically compatible with liquid fluoride salts at high temperatures. About half the cost of a solar power tower is associated with the mirrors that focus light on the receiver, and less than one-third is associated with the power cycle and heat storage. Consequently, increasing the efficiency by 20–30% has the potential for major reductions in the cost of electricity. Peak temperatures and efficiencies of current designs of power towers are restricted by (1) the use of liquid nitrate salts that decompose at high temperatures and (2) steam cycles in which corrosion limits peak temperature. The liquid-fluoride-salt technology and closed Brayton power cycles are being developed for high-temperature nuclear reactors. These developments may provide the technology and industrial basis for an advanced solar power tower.

scholarly journals Analysis of a Fluidized-Bed Particle/Supercritical-CO2 Heat Exchanger in a Concentrating Solar Power System

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Zhiwen Ma ◽  
Janna Martinek
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Heat Exchanger ◽  
Fluidized Bed ◽  
High Efficiency ◽  
Solar Power ◽  
Concentrating Solar Power ◽  
Power Cycle ◽  
Temperature Heat ◽  
The Cost

Abstract Concentrating solar power (CSP) development has focused on increasing the energy conversion efficiency and lowering the capital cost. To improve performance, CSP research is moving to high-temperature and high-efficiency designs. One technology approach is to use inexpensive, high-temperature heat transfer fluids and storage, integrated with a high-efficiency power cycle such as the supercritical carbon dioxide (sCO2) Brayton power cycle. The sCO2 Brayton power cycle has strong potential to achieve performance targets of 50% thermal-to-electric efficiency and dry cooling at an ambient temperature of up to 40 °C and to reduce the cost of power generation. Solid particles have been proposed as a possible high-temperature heat transfer or storage medium that is inexpensive and stable at high temperatures above 1000 °C. The particle/sCO2 heat exchanger (HX) provides a connection between the particles and sCO2 fluid in emerging sCO2 power cycles. This article presents heat transfer modeling to analyze the particle/sCO2 HX design and assess design tradeoffs including the HX cost. The heat transfer process was modeled based on a particle/sCO2 counterflow configuration, and empirical heat transfer correlations for the fluidized bed and sCO2 were used to calculate heat transfer area and estimate the HX cost. A computational fluid dynamics simulation was applied to characterize particle distribution and fluidization. This article shows a path to achieve the cost and performance objectives for a particle/sCO2 HX design by using fluidized-bed technology.

scholarly journals Performance modeling and techno-economic analysis of a modular concentrated solar power tower with latent heat storage

2018 ◽  
Vol 217 ◽  
pp. 143-152 ◽  
Author(s):  
Jonathan E. Rea ◽  
Christopher J. Oshman ◽  
Michele L. Olsen ◽  
Corey L. Hardin ◽  
Greg C. Glatzmaier ◽  
...  
Keyword(s):  
Economic Analysis ◽  
Latent Heat ◽  
Performance Modeling ◽  
Solar Power ◽  
Heat Storage ◽  
Concentrated Solar Power ◽  
Latent Heat Storage ◽  
Solar Power Tower

scholarly journals Calculated and experimental evaluation heat pump distiller on pentane as working substance

2020 ◽  
Vol 324 ◽  
pp. 02007
Author(s):  
Gennady A. Ilyn ◽  
Ilya I. Malafeev ◽  
Vladimir B. Sapojnikov
Keyword(s):  
High Temperature ◽  
High Efficiency ◽  
Recovery Phase ◽  
High Energy ◽  
Heat Pumps ◽  
Working Fluid ◽  
Vapor Compression ◽  
The Cost ◽  
Reliable Methods ◽  
High Temperature Vapor

One of the most common and reliable methods of water treatment is the method of thermal distillation. Despite the reliability of the method, its application is constrained by high energy intensity. The most effective way to reduce the cost of production of distillate is the use of thermal transformers, providing regenerate and heat recovery phase transformations of the distillate. The use of working fluid with the most favorable thermodynamic properties is of paramount importance for the creation of high efficiency thermotransformers. The work is considered working fluid for high-temperature heat pumps and the results of the calculation-experimental study of high-temperature vapor compression heat-pumping distiller on natural working substance n-pentan.

Fluidized-Bed Heat Transfer Modeling for the Development of Particle/Supercritical-CO2 Heat Exchanger

2017 ◽  
Author(s):  
Zhiwen Ma ◽  
Janna Martinek
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Heat Exchanger ◽  
Fluidized Bed ◽  
Solid Particles ◽  
Heat Transfer Modeling ◽  
Power Cycle ◽  
Heat Exchanger Design ◽  
Temperature Heat ◽  
The Cost

Concentrating solar power (CSP) technology is moving toward high-temperature and high-performance design. One technology approach is to explore high-temperature heat-transfer fluids and storage, integrated with a high-efficiency power cycle such as the supercritical carbon dioxide (s-CO2) Brayton power cycle. The s-CO2 Brayton power system has great potential to enable the future CSP system to achieve high solar-to-electricity conversion efficiency and to reduce the cost of power generation. Solid particles have been proposed as a possible high-temperature heat-transfer medium that is inexpensive and stable at high temperatures above 1,000°C. The particle/heat exchanger provides a connection between the particles and s-CO2 fluid in the emerging s-CO2 power cycles in order to meet CSP power-cycle performance targets of 50% thermal-to-electric efficiency, and dry cooling at an ambient temperature of 40°C. The development goals for a particle/s-CO2 heat exchanger are to heat s-CO2 to ≥720°C and to use direct thermal storage with low-cost, stable solid particles. This paper presents heat-transfer modeling to inform the particle/s-CO2 heat-exchanger design and assess design tradeoffs. The heat-transfer process was modeled based on a particle/s-CO2 counterflow configuration. Empirical heat-transfer correlations for the fluidized bed and s-CO2 were used in calculating the heat-transfer area and optimizing the tube layout. A 2-D computational fluid-dynamics simulation was applied for particle distribution and fluidization characterization. The operating conditions were studied from the heat-transfer analysis, and cost was estimated from the sizing of the heat exchanger. The paper shows the path in achieving the cost and performance objectives for a heat-exchanger design.

Primary Study on Carbon Dioxide Power Cycle of HTGR

2008 ◽  
Author(s):  
Chengjie Duan ◽  
Xiaoyong Yang ◽  
Jie Wang ◽  
Suyuan Yu
Keyword(s):  
Carbon Dioxide ◽  
High Temperature ◽  
Physical Properties ◽  
Critical Pressure ◽  
Working Fluid ◽  
Brayton Cycle ◽  
Power Cycle ◽  
Pressure Cycle ◽  
Cycle Efficiency ◽  
Thermal Physical Properties

At present, power cycles used in HTGR are indirect steam Rankine cycle and helium Brayton cycle. Using water or helium as working fluid which transform thermal energy into mechanical energy for HTGR power cycle has many disadvantages. Steam cycle could choose steam system which is similar to conventional coal-fired power plant, but because of the limit of material and equipments, there is big temperature difference between the steam and the helium, that makes big loss of thermal power and lowers the cycle efficiency. Helium can reach a high temperature in HTGR Brayton cycle and it has good stability, but because of helium has big isentropic exponent and low density, it is difficult to compress and makes helium turbine has shorter blades and more stages than normal gas turbine. Carbon dioxide has good thermal stability and physical properties. To avoid the reaction of CO2 with graphite and canning of fuel element at high temperature, it should be used in an indirect cycle as second loop working fluid. CO2 has appropriate critical pressure and temperature (7.38MPa, 304.19K) and can choose three types of cycle: supercritical cycle, subcritical-pressure cycle and trans-critical-pressure cycle (CO2 sometimes works under supercritical pressure, some times under subcritical-pressure). Carbon dioxide cycle works in a high pressure, so it makes pressure loss lower. When CO2 works close to its critical point, its density become larger than other conditions, and not change very much, this permits to reduce compress work. The thermal physical properties of carbon dioxide are totally different from helium due to CO2 works as real gas in the cycle. That causes the calculation of CO2 thermal physical properties, heat transfer and power cycle efficiency become difficult and need to be iterated. A systematic comparison between helium and carbon dioxide as working fluid for HTGR has been carried out. An empirical equation had been selected to estimate the thermal physical properties of carbon dioxide. Three types of carbon dioxide power cycle have been analyzed and the thermal efficiency has been calculated. A detailed introduction to the basic calculation process of the CO2 cycle thermal efficiency had been presented in the paper.

A Study of Supercritical Carbon Dioxide Power Cycle for Concentrating Solar Power Applications Using an Isothermal Compressor

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Jin Young Heo ◽  
Jinsu Kwon ◽  
Jeong Ik Lee
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Thermal Efficiency ◽  
Solar Power ◽  
Working Fluid ◽  
Brayton Cycle ◽  
Concentrating Solar Power ◽  
Power Cycle ◽  
Compressor Inlet ◽  
Supercritical Carbon

For the concentrating solar power (CSP) applications, the supercritical carbon dioxide (s-CO2) power cycle is beneficial in many aspects, including high cycle efficiencies, reduced component sizing, and potential for the dry cooling option. More research is involved in improving this technology to realize the s-CO2 cycle as a candidate to replace the conventional power conversion systems for CSP applications. In this study, an isothermal compressor, a turbomachine which undergoes the compression process at constant temperature to minimize compression work, is applied to the s-CO2 power cycle layout. To investigate the cycle performance changes of adopting the novel technology, a framework for defining the efficiency of the isothermal compressor is revised and suggested. This study demonstrates how the compression work for the isothermal compressor is reduced, up to 50%, compared to that of the conventional compressor under varying compressor inlet conditions. Furthermore, the simple recuperated and recompression Brayton cycle layouts using s-CO2 as a working fluid are evaluated for the CSP applications. Results show that for compressor inlet temperatures (CIT) near the critical point, the recompression Brayton cycle using an isothermal compressor has 0.2–1.0% point higher cycle thermal efficiency compared to its reference cycle. For higher CIT values, the recompression cycle using an isothermal compressor can perform above 50% in thermal efficiency for a wider range of CIT than the reference cycle. Adopting an isothermal compressor in the s-CO2 layout can imply larger heat exchange area for the compressor which requires further development.

Sintering of Solid Particulates Under Elevated Temperature and Pressure in Large Storage Bins for Thermal Energy Storage

2014 ◽  
Author(s):  
R. C. Knott ◽  
D. L. Sadowski ◽  
S. M. Jeter ◽  
S. I. Abdel-Khalik ◽  
H. A. Al-Ansary ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Size Distribution ◽  
Thermal Energy ◽  
Solar Power ◽  
Physical Characteristics ◽  
Working Fluid ◽  
Concentrated Solar Power ◽  
Power Cycle ◽  
Solid Particulates ◽  
Storage Bins

This research is a part of the DOE-funded SunShot project on “High Temperature Falling Particle Receiver.” Storing thermal energy using solid particulates is a way to mitigate the time of day dependency of concentrated solar power. Small particles may be stored easily, and can be used as a heat transfer medium to transfer heat to the power cycle working fluid through a heat exchanger. This study examines the physical characteristics of solid particulates of different materials kept inside large storage containers. Particle behavior at the expected high temperatures of the concentrated solar power cycle combined with the elevated pressure experienced within the storage container must be evaluated to assess the impact on their physical properties and ensure that the particles would not sinter thereby impacting flow through the system components particularly the receiver and heat exchanger. Sintering is a process of fusing two or more particles together to form a larger agglomerate. In the proposed concentrated solar power tower design, particles will experience temperatures from 600°C to 1000°C. The increase in temperature changes the physical characteristics of the particle, along with any impurities that could form particle to particle bonds. In addition, the hydrostatic pressure exerted on particles stored inside a storage unit increases the probability of sintering. Thus, it is important to examine the characteristics of particles under elevated temperatures and pressures. The experimental procedure involves heating particulates of a known mass and size distribution to temperatures between 600°C and 1000°C inside a crucible. As the temperature is held constant, the particulate sample is pressed upon by a piston pushing into the crucible with a known constant pressure. This process is repeated for different temperatures and pressures for varying lengths of time. The resulting particulates are cooled, and their size distribution is measured to determine the extent of sintering, if any, during the experiment. The particulates tested include various types of sand, along with alumina particles. The data from this experiment will allow designers of storage bins for the solid particulates to determine when significant sintering is expected to occur.

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