Showing papers on "Base load power plant published in 2016"

Hourly Electricity Demand Response in the Stochastic Day-Ahead Scheduling of Coordinated Electricity and Natural Gas Networks

Abstract: This paper studies the role of hourly economic demand response in the optimization of the stochastic day-ahead scheduling of electric power systems with natural gas transmission constraints. The proposed coordinated stochastic model (referred to as EGTran) considers random outages of generating units and transmission lines, and random errors in forecasting the day-ahead hourly loads. The Monte Carlo simulation is applied to create multiple scenarios for representing the coordinated system uncertainties. The nonlinear natural gas network constraints are linearized and incorporated into the stochastic model. Numerical results demonstrate the benefits of applying the hourly economic demand response for enhancing the scheduling coordination of natural gas and electricity networks. It is demonstrated that electricity demand response would offer a less volatile hourly load profile and locational marginal prices, and less dependence on natural gas constraints for the optimal operation of electric power systems. The proposed model for EGTran could be applied by grid operators for the hourly commitment and dispatch of power system units.

Overall review of peak shaving for coal-fired power units in China

Abstract: With the development of new-power generation sources, the difference between maximum and minimum power requirements from a power grid is growing. However, the peaking power installed capacity, such as pumped-hydro energy storage and gas-fired power, is too small to meet the peaking regulation requirements. Chinese coal-based energy resources structure determines coal-fired power plants to be the main source of power. This means that coal-fired power units will need to undertake more peak shaving tasks for a long period of time. In this paper, we provide an overall review of China׳s coal-fired power units׳ peak regulation with a detailed presentation of the installed capacity, peak shaving operation modes and support policies. High energy-consumption problems, environmental pollutants and safety barriers when coal-fired power units run in low-load operation are noted from the power generation perspective. Some policy recommendations are given to solve the peak shaving problem to some extent and to ensure the sustainable development of the power energy system.

An Analysis of the Effects and Dependency of Wind Power Penetration on System Frequency Regulation

Abstract: The integration of renewable energy sources into power systems has gathered significant momentum globally because of its unlimited supply and environmental benefits. Within the portfolio of renewable energy, wind power is expected to have a soaring growth rate in the coming years. Despite its well known benefits, wind power poses several challenges in grid integration. The inherent intermittent and non-dispatchable features of wind power not only inject additional fluctuations to the already variable nature of frequency deviation, they also decrease frequency stability by reducing the inertia and the regulation capability. This paper closely examines these effects as well as the effect on tie-line flows and area control error, which causes a larger and longer frequency deviation in the integrated system. Further, the effect of wind power on frequency regulation capability at different penetration levels is also examined. The analytical and simulation results presented here provide some guidance on determining maximum wind power penetration level given a frequency deviation limit.

Prospects and problems of concentrating solar power technologies for power generation in the desert regions

Abstract: Concentrated solar power plants (CSPs) are gaining momentum due to their potential of power generation throughout the day for base load applications in the desert regions with extremely high direct normal irradiance (DNI). Among various types of the CSPs, solar tower power technologies are becoming the front runners especially in the United States and around the world with the possibility to compete with traditional power generation technologies in terms of efficiency and levelized cost of electricity (LCOE). A bibliometric analysis of the publications on the CSP systems and components since 1990 shows a total of 6400+ publications and reveals an exponential growth due to reasons that CSP systems promises a lot of potential as the future large scale power source for varied applications. This review consolidates the benefits and challenges of the CSP technologies particularly in the desert regions. Thorough literature analysis as well as the meteorological data projects the trend that the CSP systems would become a reality in the Middle East and North Africa (MENA), Australia, Southwestern region of the United States, Southwestern part of China and China/Mongolia border with high direct normal irradiance. However, enormous amount of support and capital investments are needed for making these CSP systems realistic as there is not much power grid network in existence. It is evident that there are multiple challenges specifically in water consumption, materials design and development for the optimum heat transfer fluid, thermal energy storage and receiver subsystems in addition to commercial viability and environmental impacts. Each of the challenges is discussed in detail and suggestions are made to address the challenges.

Flexible Robust Optimization Dispatch for Hybrid Wind/Photovoltaic/Hydro/Thermal Power System

Abstract: With sustained growth of intermittent power supplies connected to grid, the randomness and volatility of intermittent power supplies will bring new challenges to power system optimization dispatch. For dealing with the uncertainty of large-scale intermittent power supply, this paper introduces robust optimization theory into optimization dispatch for hybrid wind/photovoltaic/hydro/thermal power systems. Meanwhile in order to make an ideal compromise between reliability and economy of system dispatch, this paper also introduces concept of uncertainty to cover shortcoming of conventional robust optimization which is conservative. A flexible robust optimization with adjustable uncertainty budget dispatch model is built for hybrid power system to achieve coordination between reliability and economy, and then the uncertainty budget decision methods are studied to reduce blindness of uncertainty budget decisions. Moreover, a new compound differential evolution (CDE) algorithm is designed in this paper. The diversity of individuals and convergence speed are taken into account in process of differential evolution (DE) calculation by introducing a series of operations into DE algorithm, such as individual ranking, population dividing, CDE, and population restructuring. Finally, a sample application is carried out to verify the validity and practicability of the model and the method.

Solar powered cellular base stations: current scenario, issues and proposed solutions

Abstract: The increasing deployment of cellular networks across the globe has brought two issues to the forefront: the energy cost of running these networks and the associated environmental impact. Also, most of the recent growth in cellular networks has been in developing countries, where the unavailability of reliable electricity grids forces operators to use sources like diesel generators for power, which not only increases operating costs but also contributes to pollution. Cellular base stations powered by renewable energy sources such as solar power have emerged as one of the promising solutions to these issues. This article presents an overview of the stateof- the-art in the design and deployment of solar powered cellular base stations. The article also discusses current challenges in the deployment and operation of such base stations and some of the proposed solutions.

Risk-Constrained Offering Strategy for Aggregated Hybrid Power Plant Including Wind Power Producer and Demand Response Provider

Abstract: The unpredictable and volatile nature of wind power is the main obstacle of this generation source in short-term trading. Owing to the ability of demand side to cover wind power imbalances, aggregated loads have been presented in the literature as a good complementary resource for the wind generation. To this end, this paper proposes a technique to obtain the best offering strategy for a hybrid power plant consisting of a wind power producer and a demand response provider in the power market. In addition, conditional value-at-risk is used to limit the risk on profit variability. Finally, a detailed analysis of a realistic case study based on a wind farm in Spain has illustrated that joint operation of wind power producers and demand response providers can increase the expected profit and reduce the potential risks.

Frequency Regulation of Source-Grid-Load Systems: A Compound Control Strategy

Abstract: A compound control strategy is proposed for frequency regulation of source-grid-load systems in which power sources, power grids, and loads are all participating in the process. Here, power sources are conventional thermal generators, including new energy power generations, and loads are composed of energy storage units (ESUs) and grid-friendly appliances (GFAs). The proposed control scheme includes two levels of operations, with the upper level to be a model predictive control (MPC) for generators and the lower level to be a distributed leader-following consensus control strategy for multiple ESUs. For new energy power generations, the power outputs are restricted on a constant value during a sampling period based on a predicted generating curve. GFAs respond to the system frequency by regulating their active power consumption. Simulations on a single power system and three interconnected area power systems are provided to verify the effectiveness of the proposed compound control strategy.

Distributed Stochastic Market Clearing With High-Penetration Wind Power

Abstract: Integrating renewable energy into the modern power grid requires risk-cognizant dispatch of resources to account for the stochastic availability of renewables. Toward this goal, day-ahead stochastic market clearing with high-penetration wind energy is pursued in this paper based on the DC optimal power flow (OPF). The objective is to minimize the social cost which consists of conventional generation costs, end-user disutility, as well as a risk measure of the system re-dispatching cost. Capitalizing on the conditional value-at-risk (CVaR), the novel model is able to mitigate the potentially high risk of the recourse actions to compensate wind forecast errors. The resulting convex optimization task is tackled via a distribution-free sample average based approximation to bypass the prohibitively complex high-dimensional integration. Furthermore, to cope with possibly large-scale dispatchable loads, a fast distributed solver is developed with guaranteed convergence using the alternating direction method of multipliers (ADMM). Numerical results tested on a modified benchmark system are reported to corroborate the merits of the novel framework and proposed approaches.

Energy Management and Power Control of a Hybrid Active Wind Generator for Distributed Power Generation and Grid Integration

Abstract: Classical wind energy conversion systems are usually passive generators. The generated power does not depend on the grid requirement but entirely on the fluctuant wind condition. A dc-coupled wind/hydrogen/super capacitor hybrid power system is studied in this paper. The purpose of the control system is to coordinate these different sources, particularly their power exchange, in order to make controllable the generated power. As a result, an active wind generator can be built to provide some ancillary services to the grid. The control system should be adapted to integrate the power management strategies. Two power management strategies are presented and compared experimentally. We found that the “source-following” strategy has better performances on the grid power regulation than the “grid-following” strategy.

Adaptive Robust Tie-Line Scheduling Considering Wind Power Uncertainty for Interconnected Power Systems

Abstract: Large-scale wind farms are typically geographically separated from load centers and distributed in different control areas. Therefore, interregional energy dispatch is important for wind power generation via sharing spinning reserve capacity among interconnected systems. However, existing tie-line scheduling methods in China do not provide satisfactory performance in accommodating the recent large-scale integration of wind power. In this paper, we describe a coordination framework for tie-line scheduling and power dispatch to operate multi-area systems. Tie-line flows are updated hourly to hedge uncertainty in the near future, preserving the operational independence of areas. The coordinated tie-line scheduling problem is formulated using two-stage adaptive robust optimization to account for uncertainties in the available wind power and is solved using a column-and-constraint generation method in a coordinate-and-decentralize manner. Comparative simulations show that the method is effective in enabling further wind power penetration and can improve economic efficiency in multi-area systems. A case study using a large-scale power system demonstrates the benefits and scalability of the method in practice.

Quantifying the increasing sensitivity of power systems to climate variability

Abstract: Large quantities of weather-dependent renewable energy generation are expected in power systems under climate change mitigation policies, yet little attention has been given to the impact of long term climate variability. By combining state-ofthe-art multi-decadal meteorological records with a parsimonious representation of a power system, this study characterises the impact of year-to-year climate variability on multiple aspects of the power system of Great Britain (including coal, gas and nuclear generation), demonstrating why multi-decadal approaches are necessary. All aspects of the example system are impacted by inter-annual climate variability, with the impacts being most pronounced for baseload generation. The impacts of inter-annual climate variability increase in a 2025 wind-power scenario, with a 4-fold increase in the inter-annual range of operating hours for baseload such as nuclear. The impacts on peak load and peaking-plant are comparably small. Less than 10 years of power supply and demand data are shown to be insuffcient for providing robust power system planning guidance. This suggests renewable integration studies - widely used in policy, investment and system design - should adopt a more robust approach to climate characterisation.

Coordinated Frequency Control Using MT-HVDC Grids With Wind Power Plants

Abstract: In the last years, wind power has continuously increased the participation in the power generation share. For transmitting the power generated from wind power plants (WPPs)to AC grids, multiterminal high-voltage direct current (HVDC)systems are envisaged as the future backbone of a European SuperGrid interconnecting wind power generation with various AC grids and countries. This paper presents a coordinated control scheme in order that offshore WPPs connected through multiterminal HVDC systems are able to contribute to the primary frequency control of the land AC grids. The proposed control scheme is capable of achieving a suitable frequency regulation even under low wind power conditions by allowing also the power share among AC areas. The control scheme is evaluated by dynamic simulations in an adapted version of the Cigr DC grid benchmark with a five-terminal HVDC grid including two wind farms and three AC networks.

Calcium looping with inherent energy storage for decarbonisation of coal-fired power plant

Abstract: Implementation of carbon capture and storage, nuclear power stations and wide utilisation of renewable energy sources have been identified as capable of reducing around 42% of the energy sector’s cumulative CO2 emissions between 2009 and 2050. In scenarios assuming high shares of renewable energy sources in the energy portfolio, energy storage technologies and the remaining power generating assets would be required to flexibly balance energy supply and demand. With nuclear power plants operating at base load, this task would be handled by flexible fossil fuel power plants with CO2 capture. However, mature CO2 capture systems were shown to impose high efficiency penalties (8–12.5% points) and are better suited for base-load operation. An emerging calcium looping process, which has also been considered for energy storage, has been found to offer lower efficiency penalties (5–8% points). This study presents a concept of the calcium looping process with inherent energy storage for decarbonisation of the coal-fired power plant. Analysis has revealed that the possible routes for energy storage in this process include CaO/CaCO3 solids storage, CaO/Ca(OH)2 solids storage and cryogenic O2 storage systems. Comparison of the CaO/CaCO3 storage and cryogenic O2 storage systems revealed that implementation of the latter would result in higher turndown of the entire system and would offer higher energy density. Also, the hydration reaction was found to improve the energy density of the CaO/CaCO3 energy storage system by 57.4%, from 307.2 kWth h m−3 to 483.6 kWth h m−3. Economic evaluation of the proposed concepts revealed that application of the cryogenic O2 storage system in the calcium looping CO2 capture process has the potential to increase the profitability of the integrated system, even over the reference coal-fired power plant without CO2 capture.

Is There Still Merit in the Merit Order Stack? The Impact of Dynamic Constraints on Optimal Plant Mix

Abstract: The merit order stack is used to tackle a wide variety of problems involving electricity dispatch. The simplification it relies on is to neglect dynamic issues such as the cost of starting stations. This leads the merit order stack to give a poor representation of the hourly pattern of prices and under-estimate the optimal level of investment in both peaking and inflexible baseload generators, and thus their run-times by up to 30%. We describe a simple method for incorporating start-up costs using a single equation derived from the load curve and station costs. The technique is demonstrated on the British electricity system in 2010 to test its performance against actual outturn, and in a 2020 scenario with increased wind capacity where it is compared to a dynamic unit-commitment scheduler. Our modification yields a better representation of electricity prices and reduces the errors in capacity investment by a factor of two.

A Method for Sizing Energy Storage System to Increase Wind Penetration as Limited by Grid Frequency Deviations

Abstract: Frequency deviation of power systems caused by grid-connected wind power fluctuations is one of the key factors limiting the level of wind penetration. Applying an energy storage system (ESS) to overcome the constraint of frequency deviation can increase the level of permitted wind penetration. This paper proposes a method to evaluate the wind penetration as limited by grid frequency deviation and to size the ESS to increase the permitted wind penetration to an expected level. The proposed method treats wind power fluctuations as a stochastic process rather than deterministic signal and takes the frequency response characteristics of power grid into full consideration. Application of the proposed method is based on theoretical derivations and does not require conducting dynamic simulation. It can catch the stochastic characteristic of wind power fluctuations.

Ocean Thermal Energy Conversion

Abstract: Baseload The minimum amount of power that a utility must make available to its customers. Baseload plant An energy plant devoted to the production of baseload supply. Baseload plants typically run at all times through the year (24/7) except in the case of repairs or scheduled maintenance. CWP Cold water pipe, the pipe used to transport deep ocean water to the OTEC condenser. Draught (Draft) The depth of a ship’s keel below the water surface. Euphotic zone The upper layer of the ocean in which there is sufficient light for photosynthesis. Externalities The costs generated by the production of electricity that are not included in the price charged to consumers. These costs manifest themselves through changes in the environment and other societal costs. Gross power The electrical power generated by the turbine-generator. Net power The electrical power available for export from the OTEC plant. The difference between gross power and in-plant power consumption needed to run all sweater and working fluid pumps. Ocean thermal resource Defined by DT, the ocean temperature differences between water depths of 20 m (surface water) and 1,000 m. OTEC Ocean Thermal Energy Conversion, the process of converting the ocean thermal energy into electricity. OTEC transfer function The relationship between the thermal resource and the electricity generated. Plantship A ship designed to house an OTEC power plant. Re-entrainment The mixing of the water already used in the OTEC plant into the incoming warm (surface) water stream. WOA05 World Ocean Atlas 2005 version.