基于正/逆布雷顿循环的热泵储电系统性能研究

热泵储电系统具有不受地理条件限制、成本低、储能密度高、系统效率高等优点,近年来受到广泛关注。对基于正/逆布雷顿循环的热泵储电系统进行了详细的热力学建模与分析,全面分析了循环工质、储/释能过程压比、压缩/膨胀过程的等熵效率和机械效率等参数对热泵储电系统性能的影响。结果表明,当压缩膨胀过程的等熵效率升高、机械效率升高、换热温差减小、阻力损失减小、保温效率升高时,系统的循环效率升高,但系统的热量、冷量利用率有可能降低。其中,压缩膨胀过程的等熵效率、机械效率和蓄热/蓄冷过程的保温效率对系统整体效率影响最大,换热温差与阻力损失的影响次之,当储/释能压比达到一定程度后的影响最小。对于热泵储电技术进一步的研究工作将着眼于热泵储电系统非稳态工况过程优化仿真和系统关键部件,如高效压缩机、膨胀机和蓄冷/蓄热换热器的研发。

新型热泵储电系统的设计方案及其性能分析

文章针对传统热泵储电系统储能密度低、工作温度高等问题,基于新型相变胶囊的换热特性,提出了一种新型热泵储电系统,并对该系统的热力学性能与做功过程进行分析。分析结果表明:新型热泵储电系统的储能密度为271.8 kW·h/m3,比传统热泵储电系统的储能密度增加了221.8 kW·h/m3;新型热泵储电系统在单次、循环充放电过程中的储热效率分别为55.1%,26.9%、在循环充放电过程中的往返效率为69.1%;与以非相变材料作为储能介质的热泵储电系统相比,新型热泵储电系统的充电时间延长了55%。文章所提出的新型热泵储电系统在储能领域具有一定的实用性。

基于相变储能介质热泵储电系统的模拟与分析

热泵储电技术具有成本较低、不受地理位置限制、储能密度较高的优点,是目前极具前景的一种新型大规模电能储存技术。传统的热泵储电系统大多以空气作为工作介质,以砂石作为储能介质,一般存在系统体积过大、储能密度较低、循环效率不高等缺点。为了提高这一技术的实用性,提出了一种以氩气为工作流体,利用相变材料作为储能介质替代原有的显热材料的热泵储电系统,建立了一个基于逆向布雷顿循环的10 MW/5 h的热泵储电系统的瞬态数值模型。模拟分析了压缩/膨胀比、孔隙率、等熵效率对系统往返效率、储能密度与功率密度的影响并对比了其与传统热泵的区别,同时评估了系统的经济性。结果表明:该储能系统储能密度可以达到182.5 kWh/m^(3),相对于显热材料提升了118.5%,往返效率可以达到63.1%,功率密度可以达到175.8 kW/m^(3)。系统单位储能费用大约为768 CNY/kWh,相比于传统的热泵储电系统降低了约12%的初始投资成本。本研究对基于布雷顿循环的热泵储电系统的热力学分析以及经济性分析具有指导价值。

一种弱海流叶轮发电储电系统研究

提出了一种基于弱海流的小型叶轮发电储电系统,通过整流电路将输入的交流电转换为稳定的直流电并储存在蓄电池中,并完成对电压、电流的监控。研究成果可作为多种海流能发电装置的后置电能储存处理模块,可以用于对海洋探测设备等进行有效续能。

储氢材料的储电功能研究

本文着重介绍了国外电解水－发电系统，储氢材料在化学电源中的应用以及燃料电池发电等方面的研究情况。

New reclosing scheme of distribution system for utilization of BESS using wavelet transform

This paper proposed the reclosing method in distribution system with battery energy storage system(BESS)using wavelet transform(WT).The proposed method performs the WT of load current and then calculates the absolute value of slope of detail coefficient.The mother wavelet used is db4of level6.The fault clearing is detected using the rapid increase of this value.After the detection of fault clearing,the reclosing is performed.To verify the proposed method,various simulations according to the fault clearing times,fault resistances,and fault lengths are performed using EMTP.The simulation results show that fault clearing can be detected using proposed absolute value of slope of detail coefficient and hence the reclosing can be performed successfully.

A novel coordinated control strategy considering power smoothing for a hybrid photovoltaic/battery energy storage system

This work presents a novel coordinated control strategy of a hybrid photovoltaic/battery energy storage(PV/BES) system. Different controller operation modes are simulated considering normal, high fluctuation and emergency conditions. When the system is grid-connected, BES regulates the fluctuated power output which ensures smooth net injected power from the PV/BES system. In islanded operation, BES system is transferred to single master operation during which the frequency and voltage of the islanded microgrid are regulated at the desired level. PSCAD/EMTDC simulation validates the proposed method and obtained favorable results on power set-point tracking strategies with very small deviations of net output power compared to the power set-point. The state-of-charge regulation scheme also very effective with SOC has been regulated between 32% and 79% range.

Flow Past an Accumulator Unit of an Underwater Energy Storage System： Three Touching Balloons in a Floral Configuration

An LES simulation of flow over an accumulator unit of an underwater compressed air energy storage facility was conducted. The accumulator unit consists of three touching underwater balloons arranged in a floral configuration. The structure of the flow was examined via three dimensional iso surfaces of the Q criterion. Vortical cores were observed on the leeward surface of the balloons. The swirling tube flows generated by these vortical cores were depicted through three dimensional path lines. The flow dynamics were visualized via time series snapshots of two dimensional vorticity contours perpendicular to the flow direction; revealing the turbulent swinging motions of the aforementioned shedding-swirling tube flows. The time history of the hydrodynamic loading was presented in terms of lift and drag coefficients. Drag coefficient of each individual balloon in the floral configuration was smaller than that of a single balloon. It was found that the total drag coefficient of the floral unit of three touching balloons, i.e. summation of the drag coefficients of the balloons, is not too much larger than that of a single balloon whereas it provides three times the storage capacity. In addition to its practical significance in designing appropriate foundation and supports, the instantaneous hydrodynamic loading was used to determine the frequency of the turbulent swirling-swinging motions of the shedding vortex tubes; the Strouhal number was found to be larger than that of a single sphere at the same Reynolds number.

基于太阳能真空集热和有机朗肯循环技术的被动传热式太阳房设计

为提高能源利用效率和减少环境污染,基于太阳能真空集热和有机朗肯循环技术设计被动传热式太阳房。被动传热式太阳房由被动太阳房系统、有机朗肯循环发电系统、储电及调压放电系统组成。太阳能经过3个子系统将能量转化为电能,最后由储电调压系统存储电能并供给到用电器,能源利用效率达到了85%。相较于传统的农村住房,新型被动传热式太阳房保温性更好且可实现部分电力的自给自足,提升了能源利用效率,采暖耗能浪费的问题也可被有效解决。

Multi-objective optimization scheduling for new energy power system considering energy storage participation

For the low utilization rate of photovoltaic power generation,taking a new energy power system constisting of concentrating solar power(CSP),photovoltaic power(PP)and battery energy storage system as an example,a multi-objective optimization scheduling strategy considering energy storage participation is proposed.Firstly,the new energy power system model is established,and the PP scenario generation and reduction frame based on the autoregressive moving average model and Kantorovich-distance is proposed.Then,based on the optimization goal of the system operation cost minimization and the PP output power consumption maximization,the multi-objective optimization scheduling model is established.Finally,the simulation results show that introducing energy storage into the system can effectively reduce the system operation cost and improve the utilization efficiency of PP.

Energy Storage System with Ultracapacitors for Thermal Underwater Glider

A power system with proton exchange membrane fuel cells (PEMFC) was designed for thermal underwater glider.Heat generated by PEMFC is used as the propulsion power of the glider,and the electricity is used in the control and sensor system.An electric energy storage system (ESS) is required which possesses high power density with good cycle life.Ultracapacitors which exhibit high power density and cycle life are considered as energy storage devices.Simulations based on a specific voyage condition indicate that ESS with ultracapacitors has positive effects on reducing the output power demand of PEMFC and lightening the power system.Experimental results show that the state of charge (SOC) is related to the capacitance and resistance in ultracapacitor ESS.

A general analytical approach to reach maximum grid support by PMSG-based wind turbines under various grid faults

A novel fault ride-through strategy for wind turbines,based on permanent magnet synchronous generator,has been proposed.The proposed strategy analytically formulates the reference current signals,disregarding grid fault type and utilizes the whole system capacity to inject the reactive current required by grid codes and deliver maximum possible active power to support grid frequency and avoid generation loss.All this has been reached by taking the grid-side converter’s phase current limit into account.The strategy is compatible with different countries’grid codes and prevents pulsating active power injection,in an unbalanced grid condition.Model predictive current controller is applied to handling rapid transients.During faults,the energy storage system maintains DC-link voltage,which causes voltage fluctuations to be eliminated,significantly.A fault ride-through strategy was proposed for PMSG-based wind turbines,neglecting fault characteristics,second,reaching maximum possible grid support in faulty grid conditions,while avoiding over-current and third,considerable reduction in energy storage system size and power rating.Inspiring simulations have been carried out through MATLAB/SIMULINK to validate the feasibility and competency of the proposed fault ride-through method and efficiency of the entire control system.

Modeling and Controlling of an Active Power Filter Using Photovoltaic System with Reduced Energy Storage Capacitor

A novel three-phase active power filter （APF） circuit with photovoltaic （PV） system to improve the quality of service and to reduce the capacity of energy storage capacitor is presented. The energy balance concept and sampling technique were used to simplify the calculation algorithm for the required utility source current and to control the voltage of the energy storage capacitor. The feasibility was verified by using the Pspice simulations and experiments. When the APF mode was used during non-operational period, not only the utilization rate, power factor and power quality could be improved, but also the capacity of energy storage capacitor could sparing. As the results, the advantages of the APF circuit are simplicity of control circuits, low cost, and good transient response.

Limiting Use of Potential Energy Storage Compared to Batteries for a Lebanese Hybrid Wind/PV System

In l,ebanon, hybrid wind/PV systems are used to provide electricity when the public electricity is cut off This paper treats the storage problems of electrical energy generated by the used renewable sources. A theoretical study on two types of electrical energy storage systems is given. These systems are the electrochemical energy storage devices （batteries） and the potential （or hydraulic） energy storage system. In order to find the limiting case of use between these two energy storage systems, economical study and comparison between them are discussed and analyzed.

Analysis of the Comprehensive Physical Field for a New Flywheel Energy Storage Motor/Generator on Ships

A novel flywheel energy storage （FES） motor/generator （M/G） was proposed for marine systems. The purpose was to improve the power quality of a marine power system （MPS） and strengthen the energy recycle. Two structures including the magnetic or non-magnetic inner-rotor were contrasted in the magnetostatic field by using finite element analysis （FEA）. By optimally designing the size parameters, the average speed of FEA results of was 17 200 r/m, and the current was controlled between 62 and 68 A in the transient field. The electrical machine electromagnetism design was further optimized by the FEA in the temperature field, to find the local overheating point under the normal operation condition and provide guidance for the cooling system. Finally, it can be concluded from the comprehensive physical field analysis that the novel redundant structure M/G can improve the efficiency of the M/G and maintain the stability of the MPS.

H2 Production from Wind Power in a Wind Farm in Spain

A hydrogen production and conversion plant from wind power was installed in the Sotavento wind farm by Gas Natural and the Galician Government. This facility is the highest electrolysis power installed at the European level. It consists of an electrolyser of 300 kW, a piston compressor, a 1,725 Nm3 H2 storage system and an engine of 55 kW. This pilot plant is being operated by Natural Gas in order to extrapolate its behavior to that of an industrial facility capable of managing all the production of Sotavento wind farm following different strategies： balancing, peak-shaving and repowering. In this paper, preliminary results at the facility are presented. The aim of these first tests has been to describe the operation of equipment under operating conditions required in the management of wind power production, in order to understand the behavior of the different equipment and try to make them suitable for this type of applications. This paper shows the difficulty of operating these systems under the wind power requirements.

Assessment of Solar-Coal Hybrid Electricity Power Generating Systems

Botswana currently depends on electricity generated from coal-based power plant or electricity supplied from the border in South Africa. The country has good reserves of coal and the solar radiation is sufficiently high to make solar thermal attractive for generating electricity. The paper presents two conceptual coal-fired power station designs in which a solar sub-system augments heat to the feed heaters or to the boiler. The thermal and economic analyses showed enhanced system performance which indicates that solar power could be embedded into existing fossil fuel plants or new power stations. Integrating solar energy with existing or new fossil fuel based power plants could reduce the cost of stand-alone solar thermal power stations, reduce CO2 emissions and produce experience necessary to operate a full scale solar thermal electricity generation facility.

Investigating Two Configurations of a Heat Exchanger in an Indirect Heating Integrated Collector Storage Solar Water Heating System

Due to the environmental impact of energy usage and increased price of fusel fuel, consumers need to be encouraged to use renewable energy sources. The IHICSSWHS （indirect heating integrated collector storage solar water heater system） is one of the most economical systems. It incorporates the collection of a solar energy component and a hot water storage component in one unit. The objective of this study was to investigate ways to enhance the thermal performance of the system. Two configurations of the system were studied： system with double row HX （heat exchanger） and tube length of 16.2 m, and system with single row HX and tube length of 8.1 m and 10.8 m. The service water tube inside diameter was also varied to 10.7 mm and 17.1 mm The steady state continuity, momentum and energy equations were numerically solved, using FLUENT software. A standard k-w turbulent model and surface-to-surface radiation model were used. The result showed that the system of 10.8 m tube length and single row HX provided higher outlet temperature than the system of 16.2 m and double row HX. Therefore, a significant reduction in cost and power usage can be achieved by using a single row HX.

Stand-Alone Wind Power System Operating with Different Storage Structures

This paper deals with control method related to a wind system operating in stand-alone applications. The stand-alone wind system is composed of three energy transfer subsystems： wind generator subsystem （wind turbine and electrical generator）, energy storage subsystem, respectively, specific local network subsystem （controlled loads）. This wind power system performs in the same time the maximization of wind energy conversion and the power balance between produced and required power. Three structures of the energy storage subsystem, based on buffer battery operation and/or capacitor voltage control, are discussed. The simulation results show that the proposed stand-alone wind power system ensures a good management of the local energy request. The design of the structures is analyzed in Matlab/Simulink environment, using PowerSim toolbox.

Electromechanical Aspects of an Experimental Hybrid Vehicle

The design and construction of an experimental solar hybrid vehicle based on the combination of photovoltaic solar energy as the main source of electricity and electric power supplied by a generator activated by the driver＇s pedaling is introduced. The vehicle has a battery to store the energy provided by both systems. The development was motivated by a Latin American solar car race through the Atacama Desert in Chile and the initiative to promote the use of clean energy for transport. A general description of the vehicle, its energetic aspects and experimental results are presented.