采用氨水溶液的先进蓄能系统工作特性研究(1)——工作原理及过程动态模型

对采用氨水溶液的变质量能量转换及储存系统的工作原理、工作循环和流程进行介绍。由于蓄能系统的能量转换过程是一个与时间有关的动态过程,常规的稳态制冷/热泵循环热力计算方法已不再适用,需给出一种新的动态热力计算方法。通过数值模拟来了解先进蓄能系统的工作特性,为进一步研究、开发该蓄能系统奠定理论基础。     

采用氨水溶液的先进蓄能系统工作特性研究(2)——全量蓄能策略下工作过程模拟及分析

根据文献[1]所建立的先进蓄能系统过程动态模型,在以长江流域较为典型的办公建筑中夏季空调冬季供热条件下,蓄能系统按全量蓄能策略运行进行数值模拟,得到在不同工作条件下系统运行参数和工作特性、溶液充注及各设备工作特性参数随时间和外部条件的变化关系。数值模拟结果对了解和掌握先进蓄能系统能量转换规律及运行特性有很大帮助,也为系统及各设备的设计(或选型)以及技术经济评价等进一步研究提供基础数据。     

电热冷联产的新压缩空气蓄能系统

提出一个将压缩空气直接在空气透平中膨胀做功发电,并产出热量和冷量的新压缩空气蓄能方法。分析了该新压缩空气蓄能系统工作的不可逆循环,并建立了仅忽略所有换热器流动阻力损失的该蓄能系统之能量转换利用率（η）计算方程式。用该方程分析研究了空气透平膨胀机与压缩机等熵效率、压缩机排气热能度、空气透平排气冷量度、换热器传热温差和空气压缩比等参数对系统η值的影响,发现空气透平等熵效率提高对η值的贡献大于压缩机效率同样提高的功效;在其它参数确定时,存在最佳压比,可使系统的能量转换利用率在该条件下达极值。分析表明：电热冷联产新压缩空气蓄能系统的能量转换利用率可达0．8左右。     

千瓦级小型液压式波浪能装置能量转换系统研究

针对小型海洋观测仪器用电需求,研究高效、可靠的小型液压式波浪能装置能量转换系统。在实验室建立一套3 kW的液压式波浪能能量转换系统,进行不同电阻负载、不同蓄能体积以及不同控制策略的液压系统试验,获得PTO效率曲线及各发电过程的特性曲线,详细分析不同控制策略的能量转换特性,得到PTO效率随阻值的增大趋于平稳、蓄能体积基本不影响PTO转换效率的结论,验证有蓄能器无控制器型直冲式能量转换系统的可行性。     

100 kW组合型振荡浮子式波浪发电装置能量转换系统研究

组合型振荡浮子式波浪发电装置由能量俘获系统与能量转换系统构成,其中能量转换系统直接决定整个装置的能量转换效率和发电功率。基于前期10 k W波浪发电装置的海试结果,对装置中的直驱型液压式能量转换系统进行结构优化,设计一种应用于100 k W波浪发电装置的蓄能型液压式能量转换系统,并研制"液压自调整控制系统",实现能量转换系统蓄能与放能过程的解耦控制。通过现场试验,验证优化后的能量转换系统在提高能量转换效率和维持过程平稳性上的有效性。基于该能量转换系统的能量输出特性,提出发电机带纯阻性负载时的"最大功率点跟踪"匹配负载计算方法,以及后续并网电力变换系统的拓扑结构设计,并通过Simulink仿真,验证方案的可靠性。     

压缩空气储能系统的理论分析及性能研究

压缩空气储能技术和抽水蓄能技术是两种最具潜力的电能规模化储存技术。构建了四套压缩空气储能方案,结合热力学第一定律对高压储罐内压缩空气的温度与压力参数的变化规律以及不同储能方案性能进行了比较。研究结果表明,高压储罐在与环境换热较差时,高压储罐的充气过程会经历较为明显的温升现象。200 m3储罐以1.0 kg/s流速充气至10 MPa时,温升幅度为22.46 ℃,储气过程的温升现象降低了储罐的空气容纳能力。在压缩空气储能系统性能方面,四套储能系统的热耗位于4 100 kJ/kW·h至4 200 kJ/kW·h之间,系统效率位于52.30%与56.33%之间。在储能系统效率与对外输出电能总量指标上,高压储罐与环境之间换热性能较好的储能系统均要优于换热条件较差的储能系统。     

含蜡原油固态储存及加热技术

我国盛产含蜡原油,其高凝点的特性给储存带来诸多困难。常规液态储存方式采用间歇供热,该方式能量消耗巨大,还会产生一些安全问题。介绍一种含蜡原油储罐顶部加热技术,解决常规加热技术中存在的安全和能量浪费问题,利用与之相适应的储罐固态储存含蜡原油,只需要在收发油时向储罐中供热,就能快速恢复作业,实现节能与安全储存。     

天管150t电弧炉炼钢的供能技术集成及生产实践

介绍了天津钢管集团股份有限公司150t电弧炉炼钢过程中三项重要的供能单元技术,即热装铁水技术、2500m^3／h集束射流供氧技术和100MVA超高功率变压器供电技术,以及技术集成。经过十余年的技术改造和生产实践,电弧炉炼钢取得了较好的生产效果：冶炼周期平均为54．6min;氧气消耗约为42．9m^3／t;冶炼电耗降至325kWh／t左右;变压器利用系数超过了11000t／（MVA·a）。     

太阳能热发电站熔盐储罐首次充盐策略研究

通过计算流体动力学(CFD)模拟计算分析某实际工程设计阶段的充盐策略参数,对储罐内熔盐温度和储罐壁面温度的影响,通过分析模拟结果后确定在项目具体实施阶段采用预热系统及电加热器系统配合的充盐策略.通过将此充盐策略用于实际商业项目第1次充盐过程,效果良好,储罐整体温度较为均匀,同时也发现在第1次充盐过程中储罐基础存在较为明...     

关于太阳能热利用系统的用能分析

将太阳能热利用系统准稳态下的能量流动过程分为3个阶段进行用能分析,采用能量分析法和分析法对每个阶段从能量的数量和质量上进行建模,以确定系统能量及的转换、传递、利用和损失情况。第一阶段的用能分析结合了太阳辐射光谱的精确建模,并利用建立的模型对一个实际的太阳能热利用系统进行相应的计算和分析。所建立的模型可明确各种太阳能热利用系统中能量及等参数的变化过程,从而为系统的优化指明方向。     

Potential impacts assessment of plug-in electric vehicles on the Portuguese energy market

Electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs), which obtain their fuel from the grid by charging a battery, are set to be introduced into the mass market and expected to contribute to oil consumption reduction. In this research, scenarios for 2020 EVs penetration and charging profiles are studied integrated with different hypotheses for electricity production mix. The impacts in load profiles, spot electricity prices and emissions are obtained for the Portuguese case study. Simulations for year 2020, in a scenario of low hydro production and high prices, resulted in energy costs for EVs recharge of 20 cents/kWh, with 2 million EVs charging mainly at evening peak hours. On the other hand, in an off-peak recharge, a high hydro production and low wholesale prices' scenario, recharge costs could be reduced to 5.6 cents/kWh. In these extreme cases, EV's energy prices were between 0.9€ to 3.2€ per 100 km. Reductions in primary energy consumption, fossil fuels use and CO₂ emissions of up to 3%, 14% and 10%, respectively, were verified (for a 2 million EVs' penetration and a dry year's off-peak recharge scenario) from the transportation and electricity sectors together when compared with a BAU scenario without EVs.     

Analysis of the problem of optimal placement and capacity of the hydrogen energy storage system in the power system

Nowadays the trend of increasing the generation units based on renewable energy sources in the electric power system can be observed. Obviously, this is due to the intensifying level of consumer load and demand for electricity. However, renewable generation is characterized by intermittent energy production, which can cause and potential imbalance between generation and demand, especially during off-peak periods. Therefore, in order to ensure a reliable power supply to consumers, it is necessary to use a maneuverable reserve of capacity, such as energy storage systems, in conjunction with the renewable energy source unit. Over the past 10 years, the energy storage market has grown by almost 50%: the installed capacity of energy storage system in the world is about 5 GW. Analysis of the literature on the subject determines the need to study the impact of these devices on the parameters of electric power systems and one of the primary tasks is to determine the optimal location and capacity of energy storage system in the power system. This paper presents the result of solving the task of determining the optimal parameters of a hydrogen energy storage system using the particle swarm optimization method for example a test scheme radial distribution system – 33 bus IEEE. The choice of the type of energy storage is based on such advantages of a hydrogen energy storage system as environmental friendliness, high energy capacity and the ability to store electricity for a long period of time. In addition, compared to lithium-ion batteries, hydrogen energy storage systems have a long life time of about 25 years, during this period of time there is no degradation and significant deterioration of its properties. All these advantages of hydrogen as an energy carrier allow to take into account not only the criterion of total value of active power losses and its maximum reduction respectively, but the possibility and economic efficiency of partial use of the stored hydrogen for other needs when determining the optimal scenario of their operation in the process of discharge.     

An off-peak energy storage concept for electric utilities: Part I—Electric utility requirements

The water battery, a reversible water electrolyser device being developed in a long-term research effort at Battelle's Columbus Laboratories, was evaluated in an analytical and conceptual design study as a load-levelling system for an electric utility. During periods when off-peak electrical power was available, the water battery would produce hydrogen and oxygen by electrolysis of water; during peak demand periods the water battery would be operated in the reverse mode, functioning as a fuel cell by producing electrical power through the recombination of the oxygen and hydrogen held in its storage vessels.The analysis involved characterisation of the PSE&G system demand requirements now and in the future, its current off-peak energy availability, the typical sizing and placement of energy storage units and the approximate break even economics and potential advantages to the utility of a water battery energy storage system. In the economic analysis, the water battery was compared with the gas turbine and the fuel cell for cost effectiveness in meeting peak and intermediate power demands, respectively.Compared with a ‘reformer-type’ fuel cell (costed at $300/kW for intermediate duty) the break even capital cost of a 50% efficient water battery would be $100/kW plus about $200/kW for each increase of $1/10⁶ Btu above the reference cost of $1/10⁶ Btu for fossil fuel. The available margin would increase about $50/kW for each decrease of 1 mill/kWh in off-peak energy cost below the reference cost of 8 mills/kWh. In a similar comparison with the gas turbine (costed at $135/kW) for peaking duty, the break even cost of a 50% efficient water battery would be $100/kW. The break even cost could rise about $100/kW for each increase in fossil fuel cost of $1/10⁶ Btu and about $20/kW for each decrease in off-peak energy cost of 1 mill/kWh.     

Mass and energy storage analysis of an absorption heat pump with simulated time dependent generator heat input

This communication presents an assessment of the feasibility of energy storage via refrigerant mass storage within an absorption cycle heat pump with simulated time dependent generator heat input. The system consists of storage volumes with the condenser and absorber of the conventional absorption cycle heat pump to store liquid refrigerant, weak and strong solutions during the generation period, which are required for the heat pump operation during the generation off period. A time dependent mass and energy storage analysis based on mass and energy balance equations for various components of the heat pump system has been carried out to evaluate energy storage concentration and storage efficiency for combined and separate storage schemes for the weak and strong solutions. Two possible performance modes, viz constant pumping ratio or the constant flow of the strong solution from the absorber to the generator have been analysed: the latter is preferable over the former from a practical point of view. Numerical computer simulation has been made for a typical winter day in Melbourne (Australia) with the desired heating load specified. It is found that the concept of refrigerant storage within the absorption cycle heat pump is technically feasible for efficient space heating. The energy storage concentration in the condenser store is slighly higher while that in absorber store is slightly lower for the separate storage mode as compared to the combined storage. However, the combined storage has an advantage of less storage volume and hence is more cost effective than separate storage and the disadvantage of limited system operation due to the decrease of solution concentrations.     

Dimensioning of the solar heating system in the zero energy house in Denmark

The paper describes the project for a Zero Energy House constructed at the Technical University of Denmark. The house is designed and constructed in such a way that it can be heated all winter without any “artificial” energy supply, the main source being solar energy. With energy conservation arrangements, such as high-insulated constructions (30–40 cm mineral wool insulation), movable insulation of the windows and heat recovery in the ventilating system, the total heat requirement for space heating is calculated to 2300 kWh per year. For a typical, well insulated, one-storied, one-family house built in Denmark, the corresponding heat requirement is 20,000 kWh. The solar heating system is dimensioned to cover the heat requirements and the hot water supply for the Zero Energy House during the whole year on the basis of the weather data in the “Reference Year”. The solar heating system consists of a 42 m² flat-plate solar collector, a 30 m³ water storage tank (insulated with 60 cm of mineral wool), and a heat distribution system. A total heat balance is set up for the system and solved for each day of the “Reference Year”. Collected and accumulated solar energy in the system is about 7300 kWh per yr; 30 per cent of the collected energy is used for space heating, 30 per cent for hot water supply, and 40 per cent is heat loss from the accumulator tank. For the operation of the solar heating system, the pumps and valves need a conventional electric energy supply of 230 kWh per year (corresponding to 5 per cent of the useful solar energy).     

Modelling and simulation of a distributed power generation system with energy storage to meet dynamic household electricity demand

Electrical consumption in a household is not stable but changeable in one day throughout a whole year. The consumption depends on weather, seasons and users. This characteristic of demand makes it difficult to design and build a distributed power generation system to meet the demand for a household. For this reason, a stand-alone distributed power generation system (DPGS) needs to be carefully designed not only to meet the dynamic household electricity demand, but also to be economical. Hence, for a DPGS, it is essential to utilise electrical energy storage (EES) unit to store the excessive energy while power generation is running at off-peak time; and then the EES may supply the stored energy during the peak demand period. This study investigates a distributed power generation system with an electric energy storage unit to meet the dynamic electricity demand in a household. The system composes of one diesel-engine-generator (DG) running with biofuel; a fuel cell; integrated with an energy storage unit including a supercapacitor and a group of batteries. Models have been set up in Dymola software and two different system configurations are proposed and simulated. The characteristics of the integrated DPGS–EES system are presented and discussed. The results show that both configurations are working properly to meet the demand.     

Energy and exergy analyses of an ice-on-coil thermal energy storage system

In this study, energy and exergy analyses are carried out for the charging period of an ice-on-coil thermal energy storage system. The present model is developed using a thermal resistance network technique. First, the time-dependent variations of the predicted total stored energy, mass of ice, and outlet temperature of the heat transfer fluid from a storage tank are compared with the experimental data. Afterward, performance of an ice-on-coil type latent heat thermal energy storage system is investigated for several working and design parameters. The results of a comparative study are presented in terms of the variations of the heat transfer rate, total stored energy, dimensionless energetic/exergetic effectiveness and energy/exergy efficiency. The results indicate that working and design parameters of the ice-on-coil thermal storage tank should be determined by considering both energetic and exergetic behavior of the system. For the current parameters, storage capacity and energy efficiency of the system increases with decreasing the inlet temperature of the heat transfer fluid and increasing the length of the tube. Besides, the exergy efficiency increases with increasing the inlet temperature of the heat transfer fluid and increasing the length of the tube.     

A new integrated system with cooling storage in soil and ground-coupled heat pump

For the purpose of decreasing the peak electricity, balancing the on and off-peak electric load and utilizing the renewable geothermal energy, a new integrated system with cooling storage in soil and a ground-coupled heat pump is presented. In the integrated system, the moist soil acts as the material for cooling storage, and pipes serve as the cooling storage devices and geothermal heat exchangers simultaneously. In the cooling season, the cooling energy is stored in soil during the off-peak period and is extracted for space cooling during the on-peak period. While in other seasons, the system works as a ground-coupled heat pump for heating or cooling. A mathematical model which describes the charging and discharging processes of the integrated system has been developed and validated, and a computer code has been implemented to simulate the operational performance of cooling charging and discharging in soil. A parametric study indicates that the charging inlet temperature, tube diameter, moisture content of soil and pipe distance are important factors in determining the cyclic performance of the integrated system.     

Thermodynamic analysis of a novel energy storage system based on compressed CO2 fluid

Because of rapidly growing renewable power capacity, energy storage system is in urgent need to cope with the reliability and stability challenges. CO₂ has already been selected as the working fluid, including thermo‐electrical energy storage or electrothermal energy storage systems and compressed CO₂ energy storage (CCES) systems. In this paper, a CCES system based on Brayton cycle with hot water as the heat storage medium is proposed and analyzed. Thermodynamic model of the system is established for energy and exergy analysis. Sensitivity analysis is then conducted to reveal effects of different parameters on system performances and pursue optimization potential. At a typical transcritical operation condition, round trip efficiency is 60% with energy density of 2.6 kWh/m³. And for the typical supercritical operation condition, the round trip efficiency can reach 71% with energy density of 23 kWh/m³. High round trip efficiency and energy density, which is comparable with those of compressed air energy storage systems, thermo‐electrical energy storage (electrothermal energy storage) systems, and other CCES systems, lead to promising prospect of the proposed system. Copyright © 2017 John Wiley & Sons, Ltd.     

Investigation of thermal performance of a ground coupled heat pump system with a cylindrical energy storage tank

An analytical and computational model for a solar assisted heat pump heating system with an underground seasonal cylindrical storage tank is developed. The heating system consists of flat plate solar collectors, an underground cylindrical storage tank, a heat pump and a house to be heated during winter season. Analytical solution of transient field problem outside the storage tank is obtained by the application of complex finite Fourier transform and finite integral transform techniques. Three expressions for the heat pump, space heat requirement during the winter season and available solar energy are coupled with the solution of the transient temperature field problem. The analytical solution presented can be utilized to determine the annual variation of water temperature in the cylindrical store, transient earth temperature field surrounding the store and annual periodic performance of the heating system. A computer simulation program is developed to evaluate the annual periodic water and earth temperatures and system performance parameters based on the analytical solution. Copyright © 2003 John Wiley & Sons, Ltd.