A Dual Half-Bridge Converter with Adaptive Energy Storage to Achieve ZVS over Full Range of Operation Conditions

Thermal energy storage systems help to couple thermal energy generation and process demand in cogeneration facilities. One single deposit with two design temperatures and one main temperature step in sensible thermal energy storage define the thermocline systems. Performance of one high size real thermocline thermal energy storage system is analysed. Starting from temperature and mass flow rate data registered by the plant control system, one advanced thermodynamic analysis is performed. The quality of heat storage is analysed in terms of evaluation of the stratification in the thermocline zone. The temperature data registered at 21 positions is extended by displacement analysis generating detailed profiles. Fraction of recoverable heat, thermocline width, stratification indices based on energy and exergy analysis, and mean temperature gradients in the thermocline region are calculated. These parameters are monitored under real operation conditions of the plant. The calculated parameters are studied to check their distribution and correlation. First and Second Law indices show parallel behaviour and two values are found that delimit situations of high and low values of mean temperature gradients. It was observed that buoyancy generates uniform forced movement with the right water temperature entering the diffusers, but good control strategies are essential to avoid mixing. The system demonstrated great stability in this use.

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Aero-Thermal Design and Testing of Advanced Turbine Blades

Volume 3: Heat Transfer; Electric Power; Industrial and Cogeneration ◽

10.1115/97-gt-066 ◽

1997 ◽

Cited By ~ 1

Author(s):

M. Haendler ◽

D. Raake ◽

M. Scheurlen

Keyword(s):

Gas Turbines ◽

Full Range ◽

Turbine Blades ◽

Design Procedure ◽

Thermal Design ◽

Test Facility ◽

Optical Pyrometer ◽

Electrical Systems ◽

Operation Conditions ◽

Improved Performance

Based on the experience gained with more than 80 machines operating worldwide in 50 and 60 Hz electrical systems respectively, Siemens has developed a new generation of advanced gas turbines which yield substantially improved performance at a higher output level. This “3A-Series” comprises three gas turbine models ranging from 70 MW to 240 MW for 50 Hz and 60 Hz power generation applications. The first of the new advanced gas turbines with 170 MW and 3600 rpm was tested in the Berlin factory test facility under the full range of operation conditions. It was equipped with various measurement systems to monitor pressures, gas and metal temperatures, clearances, strains, vibrations and exhaust emissions. This paper presents the aero-thermal design procedure of the highly thermal loaded film cooled first stage blading. The predictions are compared with the extensive optical pyrometer measurements taken at the Siemens test facility on the V84.3A machine under full load conditions. The pyrometer was inserted at several locations in the turbine and radially moved giving a complete surface temperature information of the first stage vanes and blades.

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Hydraulic Stability Analysis of a Large Prototype Francis Turbine Based on Field Test

Journal of Fluids Engineering ◽

10.1115/1.4040973 ◽

2018 ◽

Vol 140 (11) ◽

Cited By ~ 3

Author(s):

Weiyu Wang ◽

Qijuan Chen ◽

Donglin Yan

Keyword(s):

Full Range ◽

Pressure Fluctuations ◽

Field Tests ◽

Francis Turbine ◽

Operation Conditions ◽

Amplitude Increase ◽

Long Time ◽

The Time Domain ◽

Frequency Band Energy ◽

Hydraulic Stability

Long time field tests of a 200 MW prototype Francis turbine over its full range of operation were conducted. From the experimental data, the time domain and frequency domain characteristics of the pressure fluctuations in the Francis turbine at different operation conditions were analyzed. Furthermore, the reason for the amplitude increase of pressure fluctuations and the correlation between the vibration and the pressure fluctuation was studied by using a multidimensional frequency band energy ratio analysis method. Based on the above analysis, some hydraulic stability characteristics of the large prototype Francis turbine are found, and other results are also obtained.

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The Periodic Transient Kinetics Method for Investigation of Kinetic Process Dynamics Under Realistic Conditions: Methanation as an Example

10.26434/chemrxiv.14653395 ◽

2021 ◽

Author(s):

Dominik Meyer ◽

Jens Friedland ◽

Jannik Schumacher ◽

Robert Güttel

Keyword(s):

Energy Storage ◽

Transport Processes ◽

Kinetic Process ◽

Chemical Energy ◽

Unsteady State ◽

Transient Kinetics ◽

Length Scales ◽

Process Dynamics ◽

Operation Conditions ◽

Catalyzed Reactions

Due to rising interest for the integration of chemical energy storage into the electrical power grid, the unsteady-state operation of chemical reactors is gaining more and more attention with emphasis on heterogeneously catalyzed reactions. The transient response of those reactions is influenced by effects on different length scales, ranging from the active surface via the individual porous catalyst particle up to the full-scale reactor. The challenge, however, is to characterize unsteady-state effects under realistic operation conditions and to assign them to distinct transport processes. Therefore, the periodic transient kinetics (PTK) method is introduced, which allows for the separation of kinetic process dynamics at different length scales experimentally under realistic operation conditions. The methodology also provides the capability for statistical analysis of the experimental results and therefore improved reliability of the derived conclusions. Therefore, the PTK method provides the experimental basis for model-based derivation of reaction kinetics valid under dynamic conditions. The applicability of the methodology is demonstrated for the methanation reaction chosen as an example process for heterogeneously catalyzed reactions relevant for chemical energy storage purposes.

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Study on LiBr-H2O Absorption Refrigeration System with Integral Storage

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.953-954.752 ◽

2014 ◽

Vol 953-954 ◽

pp. 752-756

Author(s):

Qi Chao Yang

Keyword(s):

Energy Storage ◽

Thermal Energy ◽

Thermal Energy Storage ◽

Storage Temperature ◽

Coefficient Of Performance ◽

Absorption Refrigeration ◽

Refrigeration System ◽

Operation Conditions ◽

Storage Methods ◽

Absorption Refrigeration System

The absorption thermal energy storage (TES) system stores the energy in the form of potential energy of solution and is a promising technology for efficient energy transformation process. The performance of the absorption refrigeration system with integral storage for cooling applications using LiBr-H2O as working pair under the condition without crystallization was analyzed on the basis of the first law of thermodynamics. Simulation was employed to determine the coefficient of performance (COP) and energy storage density (ESD) of the absorption TES system under different conditions such as the absorption temperature and storage temperature. The results show that the COP of the system is 0.7453 and ESD is 169.853 MJ/m3 under typical operation conditions in summer. A low absorption temperature yields both a higher COP and ESD. The solution heat exchanger could improve the COP of the system while has no effect on ESD. Results also showed that system has a good advantage when compared to other storage methods since it is do no need thermal insulation. The absorption TES may be considered as one of the promising thermal energy storage methods.

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Distributed Control Strategy for DC Microgrids of Photovoltaic Energy Storage Systems in Off-Grid Operation

Energies ◽

10.3390/en11102637 ◽

2018 ◽

Vol 11 (10) ◽

pp. 2637 ◽

Cited By ~ 3

Author(s):

Mingxuan Chen ◽

Suliang Ma ◽

Haiyong Wan ◽

Jianwen Wu ◽

Yuan Jiang

Keyword(s):

Energy Storage ◽

Power Systems ◽

Distributed Control ◽

Control Strategy ◽

Storage System ◽

Voltage Stabilizer ◽

Dc Microgrid ◽

Dc Microgrids ◽

Photovoltaic Energy ◽

Operation Conditions

DC microgrid systems that integrate energy distribution, energy storage, and load units can be viewed as examples of reliable and efficient power systems. However, the isolated operation of DC microgrids, in the case of a power-grid failure, is a key factor limiting their development. In this paper, we analyze the six typical operation modes of an off-grid DC microgrid based on a photovoltaic energy storage system (PV-ESS), as well as the operational characteristics of the different units that comprise the microgrid, from the perspective of power balance. We also analyze the key distributed control techniques for mode transformation, based on the demands of the different modes of operation. Possible reasons for the failure of PV systems under the control of a voltage stabilizer are also explored, according to the characteristics of the PV output. Based on this information, we propose a novel control scheme for the seamless transition of the PV generation units between the maximum PV power tracking and steady voltage control processes, to avoid power and voltage oscillations. Adaptive drooping and stabilization control of the state of charge of the energy storage units are also considered, for the protection of the ESS and for reducing the possibilities of overcharging and/or over-discharging. Finally, various operation conditions are simulated using MATLAB/Simulink, to validate the performance of the proposed control strategy.

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A Metaheuristic Algorithm for Flexible Energy Storage Management in Residential Electricity Distribution Grids

Mathematics ◽

10.3390/math9192375 ◽

2021 ◽

Vol 9 (19) ◽

pp. 2375

Author(s):

Ovidiu Ivanov ◽

Bogdan-Constantin Neagu ◽

Gheorghe Grigoras ◽

Florina Scarlatache ◽

Mihai Gavrilas

Keyword(s):

Genetic Algorithm ◽

Energy Storage ◽

Distribution System ◽

Global Climate ◽

Battery Management ◽

Operation Conditions ◽

Real Distribution ◽

Residential Electricity ◽

Local Storage ◽

National Governments

The global climate change mitigation efforts have increased the efforts of national governments to incentivize local households in adopting PV panels for local electricity generation. Since PV generation is available during the daytime, at off-peak hours, the optimal management of such installations often considers local storage that can defer the use of local generation to a later time. The energy stored in batteries located in optimal places in the network can be used by the utility to improve the operation conditions in the network. This paper proposes a metaheuristic approach based on a genetic algorithm that considers three different scenarios of using energy storage for reducing the energy losses in the network. Two cases considers the battery placement and operation under the direct control of the network operator, with single and multiple bus and phase placement locations. Here, the aim was to maximize the benefit for the whole network. The third case considers selfish prosumer battery management, where the storage owner uses the batteries only for their own benefit. The optimal design of the genetic algorithm and of the solution encoding allows for a comparative study of the results, highlighting the important strengths and weaknesses of each scenario. A case study is performed in a real distribution system.

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Large-scale compressed air energy storage in porous media in a 100% renewable energy supply future

10.5194/egusphere-egu21-5148 ◽

2021 ◽

Author(s):

Firdovsi Gasanzade ◽

Fahim Sadat ◽

Ilja Tuschy ◽

Sebastian Bauer

Keyword(s):

Renewable Energy ◽

Energy Storage ◽

Power Plant ◽

Energy Supply ◽

Renewable Energy Sources ◽

Energy System ◽

Compressed Air ◽

Compressed Air Energy Storage ◽

Operation Conditions ◽

The Future

Compressed air energy storage (CAES) in porous formations is one option to compensate the expected fluctuations in energy supply in future energy systems with a 100% share of renewable energy sources. Mechanical energy is stored as pressurized air in a subsurface porous formation using off-peak power, and released during peak demand using a turbine for power generation. Depending on share and type of renewable energy sources in the future, different storage capacities and storage power rates will have to be satisfied to compensate fluctuating nature of the renewable power supply. Therefore, this study investigates scenarios for subsurface compressed air energy storage using four potential future energy system development pathways. Because for CAES subsurface processes and power generation are strongly linked via reservoir pressure and flow rates, coupled power plant and geostorage model has to be developed and employed to evaluate potential operation conditions for such a storage technique.In this study, a diabatic CAES is designed, with a three-stage compression and a two-stage expansion with heat recuperator in the power plant and a porous formation as a storage formation with 20 m thickness in an anticline trap structure at a depth between 700 and 1500 m. A withdrawal rate of 115 MW and a total stored energy of up to 348 GWh per year are derived from the future energy system scenarios. Scenario simulations are carried out by coupling the open-source thermal engineering TESPy code and the multiphase-multicomponent ECLIPSE flow simulator using highly fluctuating load profiles with a time resolution of one hour. In addition to the diabatic CAES, two adiabatic concepts are considered for the same geostorage configuration.Results show that nine vertical storage wells are sufficient to deliver the target air mass flow rates required by the power plant during 98% of the year. Flow rate limitation occurs due to bottom hole pressure limits either during the injection or the withdrawal phases, depending on the specific load profile of the future energy systems, as well as the prior operation conditions. Thus, our scenario simulation shows that one porous media CAES site can cover all expected load profiles and balance the expected offsets between energy demand and energy supply up to the GWh scale. Balancing of the energy system at the national level can be achieved by up-scaling of the results obtained in this study.

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