scholarly journals Thermodynamic Performance of a Brayton Pumped Heat Energy Storage System: Influence of Internal and External Irreversibilities

Entropy ◽  
2021 ◽  
Vol 23 (12) ◽  
pp. 1564
Author(s):  
David Pérez-Gallego ◽  
Julian Gonzalez-Ayala ◽  
Antonio Calvo Hernández ◽  
Alejandro Medina

A model for a pumped thermal energy storage system is presented. It is based on a Brayton cycle working successively as a heat pump and a heat engine. All the main irreversibility sources expected in real plants are considered: external losses arising from the heat transfer between the working fluid and the thermal reservoirs, internal losses coming from pressure decays, and losses in the turbomachinery. Temperatures considered for the numerical analysis are adequate for solid thermal reservoirs, such as a packed bed. Special emphasis is paid to the combination of parameters and variables that lead to physically acceptable configurations. Maximum values of efficiencies, including round-trip efficiency, are obtained and analyzed, and optimal design intervals are provided. Round-trip efficiencies of around 0.4, or even larger, are predicted. The analysis indicates that the physical region, where the coupled system can operate, strongly depends on the irreversibility parameters. In this way, maximum values of power output, efficiency, round-trip efficiency, and pumped heat might lay outside the physical region. In that case, the upper values are considered. The sensitivity analysis of these maxima shows that changes in the expander/turbine and the efficiencies of the compressors affect the most with respect to a selected design point. In the case of the expander, these drops are mostly due to a decrease in the area of the physical operation region.

2018 ◽  
Vol 44 ◽  
pp. 00190
Author(s):  
Paweł Wojcieszak ◽  
Ziemowit Malecha

Cryogenic Energy Storage (CES) systems are able to improve the stability of electrical grids with large shares of intermittent power plants. In CES systems, excess electrical energy can be used in the liquefaction of cryogenic fluids, which may be stored in large cryogenic vessels for long periods of time. When the demand for electricity is high, work is recovered from the cryogen during a power cycle using ambient or waste heat as an upper heat source. Most research is focused on liquid air energy storage (LAES). However, natural gas can also be a promising working fluid for the CES system. This paper presents a natural gas-based CES system, coupled with a low temperature packed bed cold storage unit. The cold, which is stored at a low temperature level, can be used to increase the efficiency of the cryogenic liquefiers. The model for the packed bed in a high grade cold storage unit was implemented and then compared with the experimental data. The impact of cold recycling on the liquefaction yield and efficiency of the cryogenic energy storage system was investigated


Author(s):  
VJ Manoj Praveen ◽  
R Vigneshkumar ◽  
N Karthikeyan ◽  
A Gurumoorthi ◽  
R Vijayakumar ◽  
...  

This investigation studied the packed bed thermal energy storage system with concrete and air used as the energy storage material and working fluid respectively. Three different configurations of packed bed arrangements such as regular ring, staggered ring and staggered ring with clearance are studied. The temperature distribution outcome of the experimental values compared with three-dimensional transient based computational simulation. The flow influencing parameters such as pressure drop, turbulence intensity, design of packed beds, the surface area of packed beds, the void fraction of the system discussed. Experimental results are in excellent agreement with simulation results. It is observed that staggered ring arrangement with the clearance for packed bed have better charging and discharging profile compared to the other two arrangements.


2018 ◽  
Author(s):  
Ana Belén Hernández ◽  
Iñigo Ortega-Fernández ◽  
Irantzu Uriz ◽  
Asier Ortuondo ◽  
Iñaki Loroño ◽  
...  

Author(s):  
Shobhana Singh ◽  
Kim Sørensen

Abstract In the present paper, a high-temperature packed bed energy storage system of volume 175,000m3 is numerically investigated. The system is a underground packed bed of truncated conical shape, which comprises of rocks as a storage medium and air as a heat transfer fluid. A one-dimensional, two-phase model is developed to simulate the transient behavior of the storage. The developed model is used to conduct a parametric study with a wide range of design parameters to investigate the change in performance during both charging and discharging operation. Results show that the model satisfactorily predicts the dynamic behavior, and the truncated conical shaped storage with a rock diameter of 3cm, insulation thickness up to 0.6m and charging-discharging rate of 553kg/s leads to lower thermal losses and higher energy efficiencies. The paper provides useful insight into the transient performance and efficiency of a large-scale packed bed energy storage system within the range of parameters investigated.


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