Study of direct thermal energy storage technologies for effectiveness of concentrating solar power plants

In this paper, numerical comparisons are devised among different direct thermal energy storage (TES) technologies of concentrating solar power (CSP) plants with possible alternatives in design, plantwide control and global economic considerations and therefore, leading the process up to the sustainable power production through the day and night. The first design is based on the conventional direct double-tank thermal energy storage CSP plant, and afterwards, the modification on the design of this plant is proposed. The modification on the plantwide control is followed by recycling the heat transfer fluid (HTF) through the solar field and decreasing the degradation of temperature of the storage in discharge period. In addition, the analogues analysis is performed towards the solutions of the stable behavior on dynamic of the storage and power production. Owing to the fact that the single-tank storage technology eliminates using an extra storage volume in process design, consequently, it decreases the capital cost of the plant, the dynamic design of the single-tank storage technology is presented. Avoiding the greater degradations of the parameters is considered and improved through the heat exchanger trains as a challenging issue in storage technologies along with the plantwide control. In this work, considerations of process control to improve the quality of storage, operational issues, and flexibility related to the selected TES technologies are discussed due to making decisions for optimal control and covering the demanded energy generated by CSP plant

Optimal Control of Hybrid Systems and Renewable Energies

This book is a collection of papers covering various aspects of the optimal control of power and energy production from renewable resources (wind, PV, biomass, hydrogen, etc.). In particular, attention is focused both on the optimal control of new technologies and on their integration in buildings, microgrids, and energy markets. The examples presented in this book are among the most promising technologies for satisfying an increasing share of thermal and electrical demands with renewable sources: from solar cooling plants to offshore wind generation; hybrid plants, combining traditional and renewable sources, are also considered, as well as traditional and innovative storage systems. Innovative solutions for transportation systems are also explored for both railway infrastructures and advanced light rail vehicles. The optimization and control of new solutions for the power network are addressed in detail: specifically, special attention is paid to microgrids as new paradigms for distribution networks, but also in other applications (e.g., shipboards). Finally, optimization and simulation models within SCADA and energy management systems are considered. This book is intended for engineers, researchers, and practitioners that work in the field of energy, smart grid, renewable resources, and their optimization and control

Variational control approach to energy extraction from a fluid flow

Energy harvesting from the environment is an important aspect of many technologies. The scale of energy capturing and storage can involve the power range from mWatt up to MWatt, depending on the used devices and the considered environments (from ambient acoustic and vibration to ocean wave motion, or wind). In this paper, the wind turbine energy harvesting problem is approached as an optimal control problem, where the objective function is the absorption of an amount of energy in a given time interval by a fluid-flow environment, that should be maximized. The interest relies on outlining general control models of fluid-flow-based extraction plants and identifying an optimum strategy for the regulation of an electrical machine to obtain a maximum-efficiency process for the related energy storage. The mathematical tools are found in the light of optimal control theory, where solutions to the fundamental equations are in the frame of Variational Control (the basis of the Pontryagin optimal control theory). A special problem, named Optimally Controlled Betz’s Machine OCBM-optimal control steady wind turbine, is solved in closed form, and it is shown that, in the simpler steady case, it reproduces the maximum efficiency machine developed in Betz’s theory

Analysis and control co-design optimization of natural gas power plants with carbon capture and thermal energy storage

2022 Summer.Includes bibliographical references.In this work, an optimization model was constructed to help address important design and operation questions for a novel system combining natural gas power plants (NGCC) with carbon capture (CC) and hot and cold thermal energy storage (TES) units. The conceptualization of this system is motivated by the expected evolution of the electricity markets towards a carbon-neutral electricity grid heavily penetrated by renewable energy sources, resulting in highly variable electricity prices and demand. In this context, there will be an opportunity for clean, flexible, and cheap fossil fuel-based generators, such as NGCC plants with CC, to complement renewable generation. However, while recent work has demonstrated that high CO2 rates are achievable, challenges due to high capital costs, flexibility limitations, and the parasitic load imposed by CC systems onto NGCC power plants have so far prevented its commercialization. Coupling TES units with CC and NGCC would allow to store thermal energy into the TES units when the electricity prices are low, either by subtracting it from the NGCC or by extracting it from the grid, and to discharge thermal power at peak prices, from the hot storage (HS) to offset the parasitic load of the CC system and from the cold storage (CS) for chilling the inlet of the NGCC combustion turbine and increase the output of the cycle beyond nominal value. For the early-stage engineering studies investigating the feasibility of this novel system, a control co-design (CCD) approach is taken where key plant sizing decisions (including storage capacities and energy transfer rates) and operational control (e.g., when to store and use thermal energy and operate the power plant) are considered in an integrated manner using a simultaneous CCD strategy. The optimal design, as well as the operation of the system, are determined for an entire year (either all-at-once or through a moving prediction horizons strategy) in a large, sparse linear optimization problem. The results demonstrate both the need for optimal operation to enable a fair economic assessment of the proposed system as well as optimal sizing decisions due to sensitivity to a variety of scenarios, including different market conditions, site locations, and technology options. After detailed analysis, the technology shows remarkable promise in that it outperforms NGCC power plants with state-of-the-art CC systems in many of the scenarios evaluated. The best overall TES technology solution relies on cheap excess grid electricity from renewable sources to charge the TES units -- the HS via resistive heating and the CS through an ammonia-based vapor compression cycle. Future enhancements to the optimization model are also discussed, which include additional degrees of freedom to the CC system, adapting the model to evaluate other energy sources and storage technologies, and considering uncertainty in the market signals directly in the optimization model

Selection of optimal mode parameters for the cogeneration units of steam turbines of a condensing-heating type

В статті розглядаються енергозберігаючі технології виробництва електричної та теплової енергії електростанціями з турбінами конденсаційно-теплофікаційного типу, шляхом відпуску теплоти від нерегульованих відборів турбіни тепловому споживачеві. Розглянуті схемні рішення для здійснення способу регулювання режиму роботи електростанції, засоби забезпечення оптимальних параметрів системи централізованого теплопостачання з акумулюванням теплоти мережної води в транзитних трубопроводах.This scientific paper gives consideration to the problems of energy saving technologies used for the production of electric and thermal energy by power plants equipped with turbines of a condensing-heating (CH) type through the delivery of heat transferred by uncontrolled turbine bleeds to the heat consumer. To improve the qualitative characteristics of steam turbine units of a CH type that participate in the power control of energy system consideration was given to the circuit design used for the implementation of the control mode of operating conditions of heat and power plants, in particular the closed-type heat supply system with storage loops, the displacement circuit for regeneration system steam bleedings, the emission circuit of stored heat of the main condensate. The tools were developed that provide optimal mode and design parameters for the centralized heat supply system with the heat storage of network water in the transit lines of heat main during the operation of the basic heat source both according to the electric and thermal schedules of power system

A novel modeling of molten-salt heat storage systems in thermal solar power plants

Many thermal solar power plants use thermal oil as heat transfer fluid, and molten salts as thermal energy storage. Oil absorbs energy from sun light, and transfers it to a water-steam cycle across heat exchangers, to be converted into electric energy by means of a turbogenerator, or to be stored in a thermal energy storage system so that it can be later transferred to the water-steam cycle. The complexity of these thermal solar plants is rather high, as they combine traditional engineering used in power stations (water-steam cycle) or petrochemical (oil piping), with the new solar (parabolic trough collector) and heat storage (molten salts) technologies. With the engineering of these plants being relatively new, regulation of the thermal energy storage system is currently achieved in manual or semiautomatic ways, controlling its variables with proportional-integral-derivative (PID) regulators. This makes the overall performance of these plants non optimal. This work focuses on energy storage systems based on molten salt, and defines a complete model of the process. By defining such a model, the ground for future research into optimal control methods will be established. The accuracy of the model will be determined by comparing the results it provides and those measured in the molten-salt heat storage system of an actual power plant

Feeder flow control and operation in large scale photovoltaic power plants and microgrids : Part I Feeder ow control in large scale photovoltaic power plants : Part II Multi-microgrids and optimal feeder ow operation of microgrids

This thesis deals with the integration of photovoltaic energy into the electrical grid. For this purpose, two main approaches can be identified: the interconnection of large scale photovoltaic power plants with the transmission network, and the interconnection of small and medium-scale photovoltaic installations with the distribution network. The first part of the thesis is focussed on the interconnection of large scale photovoltaic power plants. Large scale photovoltaic power plants are required to provide different ancillary services to the electrical networks. For this purpose, it is necessary to control the active and reactive power injected by photovoltaic power plants at the point of interconnection, i.e. to control the power flow through the main feeder. In this direction, it is developed a central controller capable of coordinating the different devices of the photovoltaic power plants as photovoltaic inverters, FACTS, capacitor banks and storage. The second part is focused on the distributed generation, consisting on small and medium-scale generation facilities connected to the distribution system. In this context, distribution grids, traditionally operated as passive systems, become active operated systems. In this part, the microgrid concept is analysed, which is one of the most promising solutions to manage, in a coordinated manner, the different distributed energy resources. Taking into account the possible transformation of the current distribution system to a multi-microgrid based system, the different architectures enabling microgrids interconnections are analysed. For the multi-microgrid operation, it could result interesting that a portion of their networks operate so that the power exchange is maintained constant, i.e. controlling the power flow at the main feeder. In this thesis, an optimal power flow problem formulation for managing the distributed generation of these feeder flow controlled microgrids is proposed

Optimal Design Of Stand Alone Hybrid PV / WTGS / Battery for Health Center Electricity System in Timor Leste

Abstract—The use of renewable energy sources as a power plant has become an alternative option to provide electrical energy sources in a health center in Timor Leste. In this study a standalone hybrid generator system design consisting of Photovoltaic (PV), Wind turbine generation system (WTGS) and battery as energy storage will be made. The PSO algorithm is used to design optimal generator and battery capacity to obtain economic value. Optimal results are obtained by taking into account the potential of wind and solar energy and loads. The application of hybrid generating systems with renewable energy sources has several problems that must be resolved. The energy generated by renewable energy power plants is intermittent. Then this system requires energy storage to achieve power balance. The simulation results in this study show how to get the optimal value by using PSO algoritm, to reach power balance with the optimal and economical design of generator and battery capacity. Keywords—Hybrid; PV; WTGS; Battery; Control, Optimal Sizing, PS

Multi-mode damping control approach for the optimal resilience of renewable-rich power systems

The integration of power-electronics-based power plants is developing significantly due to the proliferation of renewable energy sources. Although this type of power plant could positively affect society in terms of clean and sustainable energy, it also brings adverse effects, especially with the stability of the power system. The lack of inertia and different dynamic characteristics are the main issues associated with power-electronics-based power plants that could affect the oscillatory behaviour of the power system. Hence, it is important to design a comprehensive damping controller to damp oscillations due to the integration of a power-electronics-based power plant. This paper proposes a damping method for enhancing the oscillatory stability performance of power systems with high penetration of renewable energy systems. A resilient wide-area multimodal controller is proposed and used in conjunction with a battery energy storage system (BESS) to enhance the damping of critical modes. The proposed control also addresses resiliency issues associated with control signals and controllers. The optimal tuning of the control parameters for this proposed controller is challenging. Hence, the firefly algorithm was considered to be the optimisation method to design the wide-area multimodal controllers for BESS, wind, and photovoltaic (PV) systems. The performance of the proposed approach was assessed using a modified version of the Java Indonesian power system under various operating conditions. Both eigenvalue analysis and time-domain simulations are considered in the analysis. A comparison with other well-known metaheuristic methods was also carried out to show the proposed method’s efficacy. Obtained results confirmed the superior performance of the proposed approach in enhancing the small-signal stability of renewable-rich power systems. They also revealed that the proposed multimodal controller could enhance the penetration of renewable energy sources in the Javan power system by up to 50%. © 2022 by the authors. Licensee MDPI, Basel, Switzerland