A Forward Feedback Control Scheme for a Solar Thermochemical Moving Bed Countercurrent Flow Reactor

2021 ◽  
Author(s):  
Assaad Al Sahlani ◽  
Kelvin Randhir ◽  
Nesrin Ozalp ◽  
James Klausner
Keyword(s):  
Energy Storage ◽  
Feedback Control ◽  
Dynamic Response ◽  
Flow Reactor ◽  
Input Power ◽  
Solar Flux ◽  
Hybrid Reactor ◽  
System Response ◽  
Flow Rates ◽  
Storage Media

Abstract Pelletized thermochemical energy storage media has the potential for long duration energy storage. The production of charged solid state energy storage media can be done within a cylindrical cavity chemical reactor that captures concentrated solar radiation from a solar field. Temperature stability of a solar reactor is directly influenced by the solar flux intercepted. This paper presents a low-order physical model to simulate the dynamic response of temperature inside a tubular plug-flow reactor prototype. Solid granular particles are fed to the tube from the top whereas a counter-current flowing gas enters the tube from the bottom. An in-house code was developed to model transient heat transfer of the tube wall, gas, and moving particles. The model was preliminarily validated with packed beds for different temperatures ranges and two gas flow rates. Dynamic response of the reactor temperature is simulated for different input power and gas/particle flow rates. The results show that the system response can be controlled efficiently by utilizing input power (solar flux) as a control parameter. A conventional PI controller is designed to control the temperature inside the reactor and to maintain it during the solar flux intermittency. Controller parameters are tuned using the Ziegler-Nichols method to ensure optimal system response. The results show that the feedback control model is successful in tracking different reference reactor temperatures within reasonable settling time of 30 minutes and eliminated overshoot. This study can be extended to include a hybrid reactor with a multi-input, multi-output variable system.

scholarly journals The LVRT Control Scheme for PMSG-Based Wind Turbine Generator Based on the Coordinated Control of Rotor Overspeed and Supercapacitor Energy Storage

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 518
Author(s):  
Xiangwu Yan ◽  
Linlin Yang ◽  
Tiecheng Li
Keyword(s):  
Energy Storage ◽  
Wind Turbine ◽  
Low Voltage ◽  
Specific Capacity ◽  
Coordinated Control ◽  
Input Power ◽  
Voltage Sags ◽  
Rotor Speed ◽  
Control Scheme ◽  
Supercapacitor Energy Storage

With the increasing penetration level of wind turbine generators (WTGs) integrated into the power system, the WTGs are enforced to aid network and fulfill the low voltage ride through (LVRT) requirements during faults. To enhance LVRT capability of permanent magnet synchronous generator (PMSG)-based WTG connected to the grid, this paper presents a novel coordinated control scheme named overspeed-while-storing control for PMSG-based WTG. The proposed control scheme purely regulates the rotor speed to reduce the input power of the machine-side converter (MSC) during slight voltage sags. Contrarily, when the severe voltage sag occurs, the coordinated control scheme sets the rotor speed at the upper-limit to decrease the input power of the MSC at the greatest extent, while the surplus power is absorbed by the supercapacitor energy storage (SCES) so as to reduce its maximum capacity. Moreover, the specific capacity configuration scheme of SCES is detailed in this paper. The effectiveness of the overspeed-while-storing control in enhancing the LVRT capability is validated under different levels of voltage sags and different fault types in MATLAB/Simulink.

Characterization of an Air-PCM Energy Storage Design for Air Handling Unit Applications

2017 ◽  
Author(s):  
Sarah Wert ◽  
Cynthia A. Cruickshank ◽  
Dominic Groulx
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Testing Temperature ◽  
Storage Device ◽  
Flow Rates ◽  
Transfer Rates ◽  
Melting Temperatures ◽  
Air Handling Unit ◽  
Vertically Aligned

This paper will discuss the characterization of an air-PCM storage design for commercial air handling unit (AHU) applications during winter. The air-PCM storage design consists of two rows of 29 aluminum flat plate containers (0.45 m × 0.35 m × 0.01 m) filled with PCM, vertically aligned leaving an air channel between each plate of 0.011 m wide. The storage device was placed within a closed air loop which conditions the air to the desired testing temperature and velocity. The PCM selected for testing was RT44HC with a melting temperature of 44 °C. This PCM was chosen for its similar properties to other PCMs having lower melting temperatures (in the range of 5 to 18°C) that could be used in actual HVAC application implementation. The system was instrumented and calibrated with Type T thermocouples and a velocity sensor. The system was tested at various inlet temperatures (55°C to 63°C for charging and 12°C to 25°C for discharging) and flow rates. The instantaneous heat transfer rates and total energy storage were calculated for each test from the data collected. The results provide a baseline value for heat transfer rates in a simple air-PCM design, to be used for model validation.

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 Research on Energy Storage Interface Circuit and Its Control Principle Based on the L-LLC Resonant Bidirectional DC-DC Converter

2018 ◽  
Vol 36 (5) ◽  
pp. 926-932
Author(s):  
Ming Shen ◽  
Xiaobin Zhang
Keyword(s):  
Energy Storage ◽  
Dynamic Response ◽  
Optimal Trajectory ◽  
Hybrid Control ◽  
Power Grid ◽  
Operating Efficiency ◽  
Switching Frequency ◽  
Operation Performance ◽  
Interface Circuit ◽  
Zero Current Switching

Aiming at the low operating efficiency and poor dynamic response of energy storage interface circuit for flexible interface of connecting microgrid to power grid, the principle of PI or PID and optimal trajectory hybrid control based on the L-LLC resonant bidirectional DC-DC converter (L-LLC BDC) is proposed. It realize zero-voltage switching and zero-current switching for input switches and output rectifiers respectively, besides, it not only significantly reduce the computational complexity and further increase switching frequency, but also improve dynamic response of the converter remarkably. Using state-plane analysis, the operation status and characteristics of L-LLC-BDC are described in detail, based on that, the control system of the energy storage interface circuit is designed. In view of the principle of PI or PID and optimal trajectory hybrid control based on the L-LLC-BDC, the simulation shows that the correctness of theoretical analysis and the superiority of dynamic response and the operation performance of flexible interface of connecting microgrid to power grid is guaranteed.

RECOVERY OF STORED HEAT FROM SALT HYDRATE ENERGY STORAGE MEDIA

1986 ◽  
pp. 796-800
Author(s):  
J.C.O'C. Young ◽  
J.A. Collicutt ◽  
R.L. Rosborough
Keyword(s):  
Energy Storage ◽  
Salt Hydrate ◽  
Storage Media

scholarly journals A Hybrid PV-Battery System for ON-Grid and OFF-Grid Applications—Controller-In-Loop Simulation Validation

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 755 ◽  
Author(s):  
Umashankar Subramaniam ◽  
Sridhar Vavilapalli ◽  
Sanjeevikumar Padmanaban ◽  
Frede Blaabjerg ◽  
Jens Bo Holm-Nielsen ◽  
...  
Keyword(s):  
Renewable Energy ◽  
Energy Storage ◽  
Energy Systems ◽  
System Response ◽  
Renewable Energy Systems ◽  
Remote Locations ◽  
Power Fluctuations ◽  
Uninterruptible Power ◽  
Grid Side ◽  
Power Balancing

In remote locations such as villages, islands and hilly areas, there is a possibility of frequent power failures, voltage drops or power fluctuations due to grid-side faults. Grid-connected renewable energy systems or micro-grid systems are preferable for such remote locations to meet the local critical load requirements during grid-side failures. In renewable energy systems, solar photovoltaic (PV) power systems are accessible and hybrid PV-battery systems or energy storage systems (ESS) are more capable of providing uninterruptible power to the local critical loads during grid-side faults. This energy storage system also improves the system dynamics during power fluctuations. In present work, a PV-battery hybrid system with DC-side coupling is considered, and a power balancing control (PBC) is proposed to transfer the power to grid/load and the battery. In this system, a solar power conditioning system (PCS) acts as an interface across PV source, battery and the load/central grid. With the proposed PBC technique, the system can operate in following operational modes: (a) PCS can be able to work in grid-connected mode during regular operation; (b) PCS can be able to charge the batteries and (c) PCS can be able to operate in standalone mode during grid side faults and deliver power to the local loads. The proposed controls are explained, and the system response during transient and steady-state conditions is described. With the help of controller-in-loop simulation results, the proposed power balancing controls are validated, for both off-grid and on-grid conditions.

scholarly journals Development and Analysis of a Multi-Node Dynamic Model for the Simulation of Stratified Thermal Energy Storage

Energies ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 4275 ◽  
Author(s):  
Nora Cadau ◽  
Andrea De Lorenzi ◽  
Agostino Gambarotta ◽  
Mirko Morini ◽  
Michele Rossi
Keyword(s):  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Supply And Demand ◽  
District Heating ◽  
Energy Systems ◽  
High Flow ◽  
Market Penetration ◽  
Flow Rates ◽  
Smart Energy Systems

To overcome non-programmability issues that limit the market penetration of renewable energies, the use of thermal energy storage has become more and more significant in several applications where there is a need for decoupling between energy supply and demand. The aim of this paper is to present a multi-node physics-based model for the simulation of stratified thermal energy storage, which allows the required level of detail in temperature vertical distribution to be varied simply by choosing the number of nodes and their relative dimensions. Thanks to the chosen causality structure, this model can be implemented into a library of components for the dynamic simulation of smart energy systems. Hence, unlike most of the solutions proposed in the literature, thermal energy storage can be considered not only as a stand-alone component, but also as an important part of a more complex system. Moreover, the model behavior has been analyzed with reference to the experimental results from the literature. The results make it possible to conclude that the model is able to accurately predict the temperature distribution within a stratified storage tank typically used in a district heating network with limitations when dealing with small storage volumes and high flow rates.

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