Problems of Hazardous Waste Storage Facilities in Coal-fired Power Plants and Countermeasures

The hazardous waste produced by coal-fired power plants are large in quantity and variety. It is important for ecological environment protection to properly store hazardous waste in coal-fired power plants. The environmental management of hazardous waste in coal-fired power plants started late, and there are many problems in the construction and management of their storage facilities. In this paper, taking eight typical coal-fired power plants as examples, the present problems of hazardous waste storage facilities in coal-fired power plants are analyzed, and corresponding countermeasures are put forward to solve the main common problems.

A power plant for integrated waste energy recovery from liquid air energy storage and liquefied natural gas

Liquefied natural gas(LNG)is regarded as one of the cleanest fossil fuel and has experienced significant developments in recent years.The liquefaction process of natural gas is energy-intensive,while the regasification of LNG gives out a huge amount of waste energy since plenty of high grade cold energy(-160℃)from LNG is released to sea water directly in most cases,and also sometimes LNG is burned for regasification.On the other hand,liquid air energy storage(LAES)is an emerging energy storage technology for applications such as peak load shifting of power grids,which generates 30%-40%of compression heat(-200℃).Such heat could lead to energy waste if not recovered and used.The recovery of the compression heat is technically feasible but requires additional capital investment,which may not always be economically attractive.Therefore,we propose a power plant for recovering the waste cryogenic energy from LNG regasification and compression heat from the LAES.The challenge for such a power plant is the wide working temperature range between the low-temperature exergy source(-160℃)and heat source(-200℃).Nitrogen and argon are proposed as the working fluids to address the challenge.Thermodynamic analyses are carried out and the results show that the power plant could achieve a thermal efficiency of 27%and 19%and an exergy efficiency of 40%and 28%for nitrogen and argon,respectively.Here,with the nitrogen as working fluid undergoes a complete Brayton Cycle,while the argon based power plant goes through a combined Brayton and Rankine Cycle.Besides,the economic analysis shows that the payback period of this proposed system is only 2.2 years,utilizing the excess heat from a 5 MW/40 MWh LAES system.The findings suggest that the waste energy based power plant could be co-located with the LNG terminal and LAES plant,providing additional power output and reducing energy waste.

Study on integrated development and hybrid operation mode of nuclear power plant and pumped-storage power station

The nuclear power plant is suitable for base-load operation, while the pumped-storage unit mainly gives play to capacity benefit in the electric power system;hence, the integrated development and hybrid operation mode of the two can better meet the needs of the electric power system. This article first presents an analysis of the necessity and superiority of such mode, then explains its meaning and analyzes the working routes. Finally, it proposes the business modes as follows: low price pumping water electricity plus nuclear power in the near term;nuclear power shifted to pumped storage power participating in market competition in the middle term;and, in the long term, nuclear power shifted to pumped storage power as primary and serving as an electric power system when needed.

A novel technology for control of variable speed pumped storage power plant

Variable speed pumped storage machines are used extensively in wind power plant and pumped storage power plant. This paper presents direct torque and flux control(DTFC) of a variable speed pumped storage power plant(VSPSP). By this method both torque and flux have been applied to control the VSPSP. The comparison between VSPSP's control strategies is studied. At the first, a wind turbine with the capacity 2.2 k W and DTFC control strategies simulated then a 250 MW VSPSP is simulated with all of its parts(including electrical, mechanical, hydraulic and its control system) by MATLAB software. In all of simulations, both converters including two-level voltage source converter(2LVSC) and three-level voltage source converter(3LVSC) are applied. The results of applying 2LVSC and 3LVSC are the rapid dynamic responses with better efficiency, reducing the total harmonic distortion(THD) and ripple of rotor torque and flux.

Battery Energy Storage System and Demand Response Based Optimal Virtual Power Plant Operation

With certain controllability of various distribution energy resources (DERs) such as battery energy storage system (BESS), demand response (DR) and distributed generations (DGs), virtual power plant (VPP) can suitably regulate the powers access to the distribution network. In this paper, an optimal VPP operating problem is used to optimize the charging/discharging schedule of each BESS and the DR scheme with the objective to maximize the benefit by regulating the supplied powers over daily 24 hours. The proposed solution method is composed of an iterative dynamic programming optimal BESS schedule approach and a particle swarm optimization based (PSO-based) DR scheme approach. The two approaches are executed alternatively until the minimum elec-tricity cost of the whole day is obtained. The validity of the proposed method was confirmed with the obviously decreased supplied powers in the peak-load hours and the largely reduced electricity cost.

Test Facility for Low Potential Pumped Storage Power Plants and Hydrokinetic Turbines

The electric energy which is generated by wind power plants depends on the wind speed and exceeds with strong permissible wind speed the electric energy requirements of the country. In order not to reduce this electrical energy, it must be stored. The sensible energy storage is currently the pumped storage power plants. As the mountain ranges for conventional pumped storage power plants with drop heights of H 〉 600 m are strictly limited, the development of low potential pumped storage power plants has begun. Increasing the capacity of pumped storage power plants with regard to the wind power plants is urgently needed. In this paper, it is shown using the example of an unneeded port facility, how a port facility can be used after low conversion as a test facility for low potential pumped storage power plants and at the same time for the testing of hydro-kinetic turbines. This type of pump storage power plants does not save the energy due to large drop heights, but primarily due to the large volume flow of water.

Low-Carbon Dispatching for Virtual Power Plant with Aggregated Distributed Energy Storage Considering Spatiotemporal Distribution of Cleanness Value

The scale of distributed energy resources is increasing,but imperfect business models and value transmission mechanisms lead to low utilization ratio and poor responsiveness.To address this issue,the concept of cleanness value of distributed energy storage(DES)is proposed,and the spatiotemporal distribution mechanism is discussed from the perspectives of electrical energy and cleanness.Based on this,an evaluation system for the environmental benefits of DES is constructed to balance the interests between the aggregator and the power system operator.Then,an optimal low-carbon dispatching for a virtual power plant(VPP)with aggregated DES is constructed,where-in energy value and cleanness value are both considered.To achieve the goal,a green attribute labeling method is used to establish a correlation constraint between the nodal carbon potential of the distribution network(DN)and DES behavior,but as a cost,it brings multiple nonlinear relationships.Subsequently,a solution method based on the convex envelope(CE)linear re-construction method is proposed for the multivariate nonlinear programming problem,thereby improving solution efficiency and feasibility.Finally,the simulation verification based on the IEEE 33-bus DN is conducted.The simulation results show that the multidimensional value recognition of DES motivates the willingness of resource users to respond.Meanwhile,resolving the impact of DES on the nodal carbon potential can effectively alleviate overcompensation of the cleanness value.

Environmental life cycle assessment of Indian coal-fired power plants

Coal is the backbone of the Indian power sector. The coal-fired power plants remain the largest emitters of carbon dioxide, sulfur dioxide and substantial amounts of nitrogen oxides, which are associated with climate and health impacts. Various CO2 mitigation technologies （carbon capture and storage--CCS） and SO2/NOx mitigation technologies （flue gas desulfurization and selective catalytic reduction） have been employed to reduce the environmental impacts of the coal-fired power plants. Therefore, it is imperative to understand the feasibility of various mitigation technologies employed. This paper attempts to perform environmental life cycle assessment （LCA） of Indian coal-fired power plant with and without CO2, SO2 and NOx mitigation controls. The study develops new normalization factors for India in various damage categories, using the Indian emissions and energy consumption data, coupled with the emissions and particulate emission to come up with a final environmental impact of coal-fired electricity. The results show a large degree of dependence on the perspective of assessment used. The impact of sensitivities of individual substances and the effect of plant efficiency on the final LCA results is also studied.

Present status of pumped hydro storage operations to mitigate renewable energy fluctuations in Japan

This paper focuses on pumped hydro energy storage(PHES)plants’current operations after electricity system reforms and variable renewable energy(VRE)installations in Japan.PHES plants have historically been developed to create electricity demand at night in order to operate base load power plants,such as nuclear power plants,in stable conditions.Therefore,many PHES plants are located midway between nuclear power plants and large demand areas.However,all nuclear power plants had to–at least temporarily–shut down after the Great East Japan Earthquake followed by a nuclear accident at Fukushima Daiichi in 2011,and renewable energy power plants have been deployed rapidly after the introduction of a feed-in-tariff(FIT)scheme.Therefore,PHES plants are being used to mitigate fluctuations of VRE,especially in areas where renewable energy has been significantly installed.The daily highest capacity ratio of PHES plants in Kyushu area has recorded three times higher than it in the other areas where the past operating mode is still conducted.But those operations on PHES plants are simply followed as a dispatch rule of the Organization for Crossregional Coordination of Transmission Operators(OCCTO),market-based operations have not been conducted enough yet.The market design shall be changed to harmonize VRE installation and PHES plants’operations are necessary to make the transition from the past operating mode of PHES plants across Japan.

Increasing Coal-Fired Power Plant Operational Flexibility by Integrating Solar Thermal Energy and Compressed Air Energy Storage System

This paper proposed a novel integrated system with solar energy,thermal energy storage(TES),coal-fired power plant(CFPP),and compressed air energy storage(CAES)system to improve the operational flexibility of the CFPP.A portion of the solar energy is adopted for preheating the boiler’s feedwater,and another portion is stored in the TES for the CAES discharging process.Condensate water from the CFPP condenser is used for cooling compressed air during the CAES charging process.The thermodynamic performance of the integrated system under different load conditions is studied.The system operations in a typical day are simulated with EBSILON software.The system enables daily coal saving of 9.88 t and reduces CO_(2)emission by 27.95 t compared with the original CFPP at 100%load.Under partial load conditions,the system enables maximum coal saving of 10.29 t and maximum CO_(2)emission reduction of 29.11 t at 75%load.The system has maximum peak shaving depth of 9.42%under 40%load condition.The potential of the system participating ancillary service is also discussed.It is found that the integration of solar thermal system and CAES system can bring significant ancillary service revenue to a conventional CFPP.

Optimal allocation method of energy storage for integrated renewable generation plants based on power market simulation

This study designs and proposes a method for evaluating the configuration of energy storage for integrated re-newable generation plants in the power spot market,which adopts a two-level optimization model of“system simulation+plant optimization”.The first step is“system simulation”which is using the power market simu-lation model to obtain the initial nodal marginal price and curtailment of the integrated renewable generation plant.The second step is“plant optimization”which is using the operation optimization model of the integrated renewable generation plant to optimize the charge-discharge operation of energy storage.In the third step,“sys-tem simulation”is conducted again,and the combined power of renewable and energy storage inside the plant is brought into the system model and simulated again for 8,760 h of power market year-round to quantify and compare the power generation and revenue of the integrated renewable generation plant after applying energy storage.In the case analysis of the provincial power spot market,an empirical analysis of a 1 GW wind-solar-storage integrated generation plant was conducted.The results show that the economic benefit of energy storage is approximately proportional to its capacity and that there is a slowdown in the growth of economic benefits when the capacity is too large.In the case that the investment benefit of energy storage only considers the in-come of electric energy-related incomes and does not consider the income of capacity mechanism and auxiliary services,the income of energy storage cannot fulfill the economic requirements of energy storage investment.

Stability Enhancement of Small-Scale Power Grid with Renewable Power Sources by Variable Speed Diesel Power Plant

This paper proposes a power control method to improve a stability of a small-scale power grid with renewable energy sources. In an isolated small- scale power grid such as an island, diesel power plant is main power source which has an environmental burden and expensive running cost due to high priced fossil fuel. Thus, expanding installation of the renewable energy sources such as a wind power is strongly desirable. Such fluctuating energy sources, however, harm power quality of the small-scale power grid, and in addition, conventional power plant in the small-scale power grid cannot, in general, stabilize the grid system with such fluctuating power sources. In this study, Variable Speed Doubly-Fed Induction Generator (VS-DFIG) is proposed to be in-stalled at a diesel power plant instead of a conventional Fixed Speed Synchronous Generator (FS-SG), because quick control of a power balance in the small-scale power grid can be achieved by using the inertial energy of VS-DFIG. In addition, utilization of a Battery Energy Storage System (BESS) is also considered to assist cooperatively the VS-DFIG control. As a result of the simulation analysis by using the proposed method, it is verified that frequency fluctuations due to renewable energy source can be effectively reduced by quick power control of the VS-DFIG compared to the conventional FS-SG, and further control ability can be obtained by utilizing BESS. Moreover, the transient stability of a small-scale power grid during a grid fault can also be enhanced.

Simulation and analysis of a peak regulation gas power plant with advanced energy storage and cryogenic CO_(2) capture

Flexible gas power plants are subject to energy storage,peak regulations,and greenhouse gas emissions.This study proposes an integrated power generation system that combines liquid air energy storage(LAES),liquefied natural gas(LNG)cold energy utilization,gas power systems,and CO_(2) capture and storage(CCS)technologies,named the LAES-LNG-CCS system.The off-peak electricity can be stored in liquid air.During the peak period,air and gas turbines generate supplementary electricity.Both LNG chemical energy and cold energy were considered:the former was used for gas power plants,and the latter was used for LAES regasification and CCS processes.Based on the thermodynamic analysis,we evaluated the effects of the recovery pressure,CCS pressure,and combustion temperature on the system power consumption and efficiency.The results demonstrated that the system recovery pressure,CCS pressure,and combustion temperature had the greatest effects on system power generation.Round-trip efficiency(RTE)was significantly affected by combustion temperature.The largest exergy loss occurred in the gas power plant.The optimal system operating ranges of the system recovery pressure,CCS pressure,and combustion temperature were 6−10 MPa,0.53−0.8 MPa,and 1,503−1,773 K,where the RTEs and𝜂Ex,RS reached 55%−58.98%and 74.6%−76%,respectively.The proposed system can simultaneously achieve the synergistic functions of large-scale energy storage,multilevel energy utilization,peak regulation,and carbon emission reduction.It can also be widely used in advanced distributed energy storage applications in the future.

Development of Sensible Heat Storage Materials Using Sand, Clay and Coal Bottom Ash

In this paper, the mechanical and thermal properties of a sand-clay ceramic with additives coal bottom ash (CBA) waste from incinerator coal power plant are investigated to develop an alternative material for thermal energy storage (TES). Ceramic balls are developed at 1000°C and 1060°C using sintering or firing method. The obtained ceramics were compressed with a compression machine and thermally analyse using Decagon devise KD2 Pro thermal analyser. A muffle furnace was also used for thermal cycling at 610°C. It was found that the CBA increased the porosity, which resulted in the increase of the axial tensile strength reaching 3.5 MPa for sand-clay and ash ceramic. The ceramic balls with the required tensile strength for TES were selected. Their volumetric heat capacity, and thermal conductivity range respectively from 2.4075 MJ·m-3·°C-1 to 3.426 MJ·m-3·°C-1 and their thermal conductivity from 0.331 Wm-1·K-1, to 1.014 Wm-1·K-1 depending on sand origin, size and firing temperature. The selected formulas have good thermal stability because the most fragile specimens after 60 thermal cycles did not present any cracks. These properties allow envisioning the use of the ceramic balls developed as filler material for thermocline thermal energy storage (structured beds) in Concentrating Solar Power plants. And for other applications like solar cooker and solar dryer.

含整体煤气化燃料电池-碳捕集电厂的风火储系统分布鲁棒调度方法

整体煤气化燃料电池(integrated gasification fuel cell,IGFC)是与碳捕集技术高度适配的清洁、高效、稳定的绿色煤电技术,有望克服传统碳捕集技术在低浓度CO_(2)环境下产生的高成本、高能耗问题。该文构建含IGFC碳捕集电厂的风火储发电系统。研究IGFC碳捕集电厂的运行机理,对IGFC内部各环节建立数学模型,提出工况匹配时燃烧利用率和阴极空气利用率需要满足的运行条件,并针对该型碳捕集电厂的电碳特性进行分析。为计及风电出力的不确定性,构建风火储系统的两阶段分布鲁棒经济调度模型,引入k阶适应性理论,提出基于正交支撑子集策略的求解方法来获得鲁棒对等式。最后,在改进IEEE-30节点系统中进行算例分析,结果表明,该型碳捕集电厂可利用阳极碳富集的优势,实现系统低碳经济调度的目标,并验证所提优化方法能为可行解提供可解释性。

电动汽车接入主动配电网协同储能研究应用综述

电动汽车的快速发展和普及已经呈现规模化效应,随着配电网中清洁能源逐渐呈现高比例趋势,规模化电动汽车接入主动配电网作为储能配置参与协同调度成为研究热点。然而在实际应用中,电动汽车参与储能的形式面临诸多不确定性与挑战。为此,分析了协同储能调度的目的及影响因素,从计及需求响应、考虑供需双方、结合多方利益、参与虚拟电厂储能四个方面综述协同储能调度的研究现状,结合国内外应用案例分析探讨其未来发展方向。

混合式抽水蓄能电站对下泄水温影响的数值模拟研究

【目的】混合式抽水蓄能电站运行特性与常规电站相比存在差异,本文旨在掌握抽水蓄能电站水温的变化规律,为水库管理调度提供参考。【方法】以紧水滩水库为研究对象,采用MIKE3水温模型模拟不同进/出水口高程以及不同抽水流量工况的下泄水温,据此探讨混合式抽水蓄能电站对下泄水温的影响。【结果】抽蓄水流会对下泄水温产生影响,相对于现状无抽水工况的下泄水温,抽蓄工况下的下泄水温基本表现为5—9月略有下降,其余月份略有升高,下泄水温的最大降幅不超过0.7℃,最大升幅不超过0.8℃。【结论】进/出水口高程对于下泄水温影响较大,且高程越低,下泄水温差异越大。然而抽水流量对于下泄水温差异影响并不显著,但整体上也呈现出随着抽水流量增加,水温差异增大的趋势。

多能互补发电系统故障识别与测距方法

随着大量新能源的接入,使得多端柔性直流系统(modular multilevel converter based multi-terminal direct current, MMC-MTDC)故障特征愈加复杂,快速准确的故障识别与测距是亟需解决的关键难题之一。为此,提出了一种风-光-储-蓄互补发电站经柔性直流输电外送系统故障识别与测距方法。首先,搭建风-光-储-蓄互补发电站经柔直外送系统,在此基础上,提出了一种Teager能量算子能量熵的新方法,利用测量点正负极Teager能量算子能量熵的比值构建故障选极及区段识别判据。接着,针对已识别的故障线路,提出变分模态分解(variational mode decomposition, VMD)与Teager能量算子(teager energy operator, TEO)相结合的故障测距方法。最后,利用PSCAD/EMTDC进行仿真,结果表明所提识别方法可以准确判断故障所在线路,所提测距方法能在故障发生2 ms时间窗内实现故障测距,误差率不超过2.55%,并具有较高的耐过渡电阻能力。

计及源-荷多类型备用的虚拟电厂双层优化运行

需求响应行为和共享储能的运行均会对虚拟电厂能量流动产生影响,在此背景下,为提高虚拟电厂对可再生能源的消纳能力,提出一种计及源-荷多类型备用的虚拟电厂双层优化调度方法。文中对风电的不确定性、需求响应参与能量和备用调度以及共享储能运行模式进行建模;建立双层调度模型,上层为考虑风电不确定性的日前能量和备用计划调度模型,下层为考虑风电波动性的日内修正模型。最后通过算例讨论了共享储能和需求响应对虚拟电厂能量和备用调度的影响,验证了模型的正确性和经济性。

多组合虚拟电厂中氢储能低碳经济配置与优化

提出蓄电池-氢混合储能虚拟电厂优化运行方案,首先分析各运行单元的特性并建立协同运行优化模型,然后在虚拟电厂应用蓄电池的基础上,增加由电解槽、储氢罐和燃料电池组成的氢能系统,以实现蓄电池与氢能系统混合储能。考虑电价型需求响应和阶梯型碳交易理论,较分析5种不同方案的虚拟电厂的优化运行成本及收益,实例证明蓄电池-氢混合储能的风光虚拟电厂方案具有更好的经济性和低碳性。