scholarly journals Solar Salt Latent Heat Thermal Storage for a Small Solar Organic Rankine Cycle Plant

2019 ◽  
Vol 142 (3) ◽  
Author(s):  
Sol-Carolina Costa ◽  
Khamid Mahkamov ◽  
Murat Kenisarin ◽  
Mohammad Ismail ◽  
Kevin Lynn ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Latent Heat ◽  
Storage System ◽  
Organic Rankine Cycle ◽  
Heat Pipes ◽  
Rankine Cycle ◽  
Thermal Storage ◽  
Thermal Bonding ◽  
Solar Salt ◽  
Computational Fluid Dynamics Analysis

Abstract The design of the latent heat thermal storage system (LHTESS) was developed with a thermal capacity of about 100 kW h as a part of small solar plant based on the organic Rankine cycle (ORC). The phase change material (PCM) used is solar salt with the melting/solidification temperature of about 220 °C. Thermophysical properties of the PCM were measured, including its phase transition temperature, heat of fusion, specific heat, and thermal conductivity. The design of the thermal storage was finalized by means of the 3D computational fluid dynamics analysis. The thermal storage system is modular, and the thermal energy is delivered with the use of thermal oil, heated by Fresnel mirrors. The heat is transferred into and from the PCM in the casing using bidirectional heat pipes, filled with water. A set of metallic screens are installed in the box with the pitch of 8–10 mm to enhance the heat transfer from heat pipes to the PCM and vice-versa during the charging and discharging processes, which take about 4 h. This work presents a numerical study on the use of metallic fins without thermal bonding as a heat transfer enhancement method for the solar salt LHTESS. The results show that the absence of the thermal bonding between fins and heat pipes (there was a gap of 0.5 mm between them) did not result in a significant reduction of charging or discharging periods. As expected, aluminum fins provide better performance in comparison with steel ones due to the difference in the material conductivity. The main advantage observed for the case of using aluminum fins was the lower temperature gradient across the LHTESS.

scholarly journals Solar Salt Latent Heat Thermal Storage for a Small Solar Organic Rankine Cycle Plant

2018 ◽  
Author(s):  
Sol-Carolina Costa ◽  
Khamid Mahkamov ◽  
Murat Kenisarin ◽  
Kevin Lynn ◽  
Elvedin Halimic ◽  
...  
Keyword(s):  
Heat Pipe ◽  
Latent Heat ◽  
Storage System ◽  
Organic Rankine Cycle ◽  
Heat Pipes ◽  
Rankine Cycle ◽  
Thermal Storage ◽  
Working Fluid ◽  
External Diameter ◽  
Solar Salt

The design of the Latent Heat Thermal Storage System (LHTESS) was developed with thermal capacity of about 100 kWh as a part of small solar plant, based on the Organic Rankine Cycle (ORC). The phase change material (PCM) used is Solar salt with the melting/solidification temperature of about 220°C. Thermo-physical properties of the PCM were measured, including its phase transition temperature, heat of fusion, specific heat and thermal conductivity. The design of the thermal storage was finalized by means of the 3-D CFD analysis. The thermal storage system is made of six rectangular boxes with dimensions of 1 m (width) × 0.66 m (height) × 0.47 m (depth). The thermal energy is delivered to each of the thermal storage boxes with the use of thermal oil, heated by Fresnel mirrors. The heat is transferred into and from the PCM in the box using 40 bi-directional heat pipes with the external diameter of about 12 mm. The length of the heat pipe in the PCM box is 430 mm and it is placed in the cylindrical metallic protection cartridge, installed in the thermal storage vessel. The working fluid in the heat pipe is water. A set of metallic screens are installed in the box with the pitch of 8–10 mm to enhance the heat transfer from heat pipes to the PCM and vice-versa during the charging and discharging processes, which take about 4 hours. The one unit of the described thermal storage system is undergoing the laboratory tests. Preliminary results demonstrate that the performance of the thermal storage is in a good agreement with numerical predictions. After completion of final design modifications, all units will be assembled at the plant’s demonstration site and tested with the ORC turbine.

scholarly journals Development of a Small Solar Thermal Power Plant for Heat and Power Supply to Domestic and Small Business Buildings

2018 ◽  
Author(s):  
Khamid Mahkamov ◽  
Piero Pili ◽  
Roberto Manca ◽  
Arthur Leroux ◽  
Andre Charles Mintsa ◽  
...  
Keyword(s):  
Power Plant ◽  
Latent Heat ◽  
Thermal Power Plant ◽  
Thermal Power ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Thermal Storage ◽  
Solar Thermal ◽  
Solar Thermal Power ◽  
Solar Field

The small solar thermal power plant is being developed with funding from EU Horizon 2020 Program. The plant is configured around a 2-kWel Organic Rankine Cycle turbine and solar field, made of Fresnel mirrors. The solar field is used to heat thermal oil to the temperature of about 240 °C. This thermal energy is used to run the Organic Rankine Cycle turbine and the heat rejected in its condenser (about 18-kWth) is utilized for hot water production and living space heating. The plant is equipped with a latent heat thermal storage to extend its operation by about 4 hours during the evening building occupancy period. The phase change material used is Solar salt with the melting/solidification point at about 220 °C. The total mass of the PCM is about 3,800 kg and the thermal storage capacity is about 100 kWh. The operation of the plant is monitored by a central controller unit. The main components of the plant are being manufactured and laboratory tested with the aim to assemble the plant at the demonstration site, located in Catalonia, Spain. At the first stage of investigations the ORC turbine will be directly integrated with the solar filed to evaluate their joint performance. During the second stage of tests, the Latent Heat Thermal Storage will be incorporated into the plant and its performance during the charging and discharging processes will be investigated. It is planned that the continuous filed tests of the whole plant will be performed during the 2018–2019 period.

Conjugate Heat Transfer in Latent Heat Thermal Storage System With Cross Plate Fins

2015 ◽  
Vol 137 (10) ◽  
Author(s):  
Rajesh Alayil ◽  
C. Balaji
Keyword(s):  
Heat Transfer ◽  
Latent Heat ◽  
Phase Change Materials ◽  
Storage System ◽  
Thermal Storage ◽  
High Heat ◽  
Heat Fluxes ◽  
Isothermal Conditions ◽  
Latent Heat Capacity ◽  
Composite Heat

Latent heat thermal storage systems (LHTS) utilize their latent heat capacity to dissipate high heat fluxes while maintaining quasi-isothermal conditions. Phase change materials (PCMs) absorb a large amount of energy during their phase transformation from solid to liquid, maintaining quasi-isothermal conditions. However, they are often beset with low thermal conductivities which necessitate the use of a thermal conductivity enhancer (TCE) as it is impossible to design a device that can completely avoid sensible heat in the premelting or postmelting phase. In this study, the heat transfer performance of LHTS with cross plate fins as a TCE is numerically investigated for different values of fin thicknesses and fin numbers along the length and breadth. A hybrid artificial neural network coupled genetic algorithm (ANN–GA) is then used to obtain the optimized dimensions for the composite heat sink with cross plate fins as TCE for a fixed volume and a specific heat flux input. The numerically optimized configuration is finally validated with in-house experiments.

Heat Transfer Characterization and Optimization of Latent Heat Thermal Storage System Using Fins for Medium Temperature Solar Applications

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
Asmita Shinde ◽  
Sankalp Arpit ◽  
Pramod KM ◽  
Peddy V C. Rao ◽  
Sandip K. Saha
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Latent Heat ◽  
Optimum Design ◽  
Thermal Performance ◽  
Storage System ◽  
Thermal Storage ◽  
Solar Thermal ◽  
Medium Temperature ◽  
Fin Thickness

While solar thermal power plants are increasingly gaining attention and have demonstrated their applications, extending electricity generation after the sunset using phase change material (PCM) still remains a grand challenge. Most of the organic PCMs are known to possess high energy density per unit volume, but low thermal conductivity, that necessitates the use of thermal conductivity enhancers (TCEs) to augment heat transfer within PCM. In this paper, thermal performance and optimization of shell and tube heat exchanger-based latent heat thermal energy storage system (LHTES) using fins as TCE for medium temperature (<300 °C) organic Rankine cycle (ORC)-based solar thermal plant are presented. A commercial grade organic PCM, A164 with melting temperature of 168.7 °C is filled in the shell side and heat transfer fluid (HTF), Hytherm 600 flows through the tubes. A three-dimensional numerical model using enthalpy technique is developed to study the solidification of PCM, with and without fin. Further, the effect of geometrical parameters of fin, such as fin thickness, fin height, and number of fin on the thermal performance of LHTES, is studied. It is found that fin thickness and number of fin play significant role on the solidification process of PCM. Finally, the optimum design of the fin geometry is determined by maximizing the combined objective of HTF outlet temperature and solid fraction of PCM at the end of the discharging period. The latent heat thermal storage system with 24 fins, each of 1 mm thickness and 7 mm height, is found to be the optimum design for the given set of operating parameters.

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