Initiative Optimization Operation Strategy and Multi-objective Energy Management Method for Combined Cooling Heating and Power

This paper proposed an initiative optimization operation strategy and multi-objective energy management method for combined cooling heating and power(CCHP) with storage systems.Initially,the initiative optimization operation strategy of CCHP system in the cooling season,the heating season and the transition season was formulated.The energy management of CCHP system was optimized by the multi-objective optimization model with maximum daily energy efficiency,minimum daily carbon emissions and minimum daily operation cost based on the proposed initiative optimization operation strategy.Furthermore,the pareto optimal solution set was solved by using the niche particle swarm multi-objective optimization algorithm.Ultimately,the most satisfactory energy management scheme was obtained by using the technique for order preference by similarity to ideal solution(TOPSIS) method.A case study of CCHP system used in a hospital in the north of China validated the effectiveness of this method.The results showed that the satisfactory energy management scheme of CCHP system was obtained based on this initiative optimization operation strategy and multi-objective energy management method.The CCHP system has achieved better energy efficiency,environmental protection and economic benefits.

Water, Air Emissions, and Cost Impacts of Air-Cooled Microturbines for Combined Cooling, Heating, and Power Systems： A Case Study in the Atlanta Region

城市化进程的加快意味着城市和国际组织需要去寻找各种能够提高能源效率和减少空气中污染物排放的方法。冷热电联产(CCHP)系统可以同时供暖、制冷和发电,具有提高城市或城市区域能源发电效率的潜力。本研究的目的是在满足建筑热需求(供热和制冷)的各种运行条件下,对亚特兰大大都市区内的五种常见建筑类型在采用CCHP系统时的发电耗水、CO_2和NO_x排放,及其经济性进行评价。对于大多数采用或不采用净计量策略的建筑类型来说,以满足每小时热需求去运行CCHP系统均可减少CO_2的排放量。该系统能否对这些建筑类型产生经济效益,主要取决于天然气的价格、净计量策略的采用和假定的CCHP系统的成本结构。当建筑物采用净计量策略并且CCHP系统是以满足建筑物每年的最大热需求而运行时,CCHP系统的发电耗水量和NO_x的排放量均有最大限度的减少,尽管此时该运行情景会增加温室气体排放和发电成本。CCHP系统对中型办公楼、大型办公楼和多户型住宅建筑更经济、实用。

A Financial Approach to Evaluate an Optimized Combined Cooling, Heat and Power System

Iran’s removing subsidy from energy carrier in four years ago leads to spike electricity price dramatically. This abrupt change increases the interest on distributed generation (DG) because of its several benefits such as lower electricity generation price. In Iran among all type of DGs, because of wide natural gas network infrastructure and several incentives that government legislated to support combined cooling, heat and power (CCHP) investors, this type of technology is more prevalent in comparison with other technologies. Between existing CCHP technologies, certain economic choices are to be taken into account. For different buildings with different load curves, suitable size and operation of CCHP should be calculated to make the project more feasible. If CCHP does not well suited for a position, then the whole energy efficiency would be plunged significantly. In this paper, a model to find the optimal size and operation of CCHP and auxiliary boiler for any users is proposed by considering an integrated view of electricity and natural gas network using GAMS software. Then this method is applying for a hospital in Tehran as a real case study. Finally, by applying COMFAR III software, useful financial parameters and sensitivity analysis are calculated.

Multi-Objective Optimization Based on Life Cycle Assessment for Hybrid Solar and Biomass Combined Cooling,Heating and Power System

The complementary of biomass and solar energy in combined cooling,heating and power(CCHP)system provides an efficient solution to address the energy crisis and environmental pollutants.This work aims to propose a multi-objective optimization model based on the life cycle assessment(LCA)method for the optimal design of hybrid solar and biomass system.The life-cycle process of the poly-generation system is divided into six phases to analyze energy consumption and greenhouse gas emissions.The comprehensive performances of the hybrid system are optimized by incorporating the evaluation criteria,including environmental impact in the whole life cycle,renewable energy contribution and economic benefit.The non-dominated sorting genetic algorithmⅡ(NSGA-Ⅱ)with the technique for order preference by similarity to ideal solution(TOPSIS)method is employed to search the Pareto frontier result and thereby achieve optimal performance.The developed optimization methodology is used for a case study in an industrial park.The results indicate that the best performance from the optimized hybrid system is reached with the environmental impact load reduction rate(EILRR)of 46.03%,renewable energy contribution proportion(RECP)of 92.73%and annual total cost saving rate(ATCSR)of35.75%,respectively.By comparing pollutant-eq emissions of different stages,the operation phase emits the largest pollutant followed by the phase of raw material acquisition.Overall,this study reveals that the proposed multi-objective optimization model integrated with LCA method delivers an alternative path for the design and optimization of more sustainable CCHP system.

Thermodynamic Analysis of Solid Oxide Fuel Cell Based Combined Cooling,Heating,and Power System Integrated with Solar-Assisted Electrolytic Cell

Syngas fuel such as hydrogen and carbon monoxide generated by solar energy is a promising method to use solar energy and overcome its fluctuation effectively.This study proposes a combined cooling,heating,and power system using the reversible solid oxide fuel cell assisted by solar energy to produce solar fuel and then supply energy products for users during the period without solar radiation.The system runs a solar-assisted solid oxide electrolysis cell mode and a solid oxide fuel cell mode.The thermodynamic models are constructed,and the energetic and exergetic performances are analyzed.Under the design work conditions,the SOEC mode’s overall system energy and exergy efficiencies are 19.0%and 20.5%,respectively.The electrical,energy and exergy efficiencies in the SOFC mode are 51.4%,71.3%,and 45.2%,respectively.The solid oxide fuel cell accounts for 60.0%of total exergy destruction,caused by the electrochemical reactions’thermodynamic irreversibilities.The increase of operating temperature of solid oxide fuel cell from 800℃to 1050℃rises the exergy and energy efficiencies by 11.3%and 12.3%,respectively.Its pressure from 0.2 to 0.7 MPa improves electrical efficiency by 13.8%while decreasing energy and exergy efficiencies by 5.2%and 6.0%,respectively.

A Comprehensive Study of a Low-Grade Heat-Driven Cooling and Power System Based on Heat Current Method

Combined cooling and power(CCP)system driven by low-grade heat is promising for improving energy efficiency.This work proposes a CCP system that integrates a regenerative organic Rankine cycle(RORC)and an absorption chiller on both driving and cooling fluid sides.The system is modeled by using the heat current method to fully consider nonlinear heat transfer and heat-work conversion constraints and resolve its behavior accurately.The off-design system simulation is performed next,showing that the fluid inlet temperatures and flow rates of cooling water as well as RORC working fluid strongly affect system performance.The off-design operation even becomes infeasible when parameters deviate from nominal values largely due to limited heat transfer capability of components,highlighting the importance of considering heat transfer constraints via heat current method.Design optimization aiming to minimize the total thermal conductance is also conducted.RORC efficiency increases by 7.9%and decreases by 12.4%after optimization,with the hot fluid inlet temperature increase from 373.15 to 403.15 K and mass flow rate ranges from 10 to 30 kg/s,emphasizing the necessity of balancing system cost and performance.

Optimization of Operation Strategies for a Combined Cooling, Heating and Power System based on Adiabatic Compressed Air Energy Storage

The fluctuations of renewable energy and various energy demands are crucial issues for the optimal design and operation of combined cooling,heating and power(CCHP)system.In this paper,a novel CCHP system is simulated with advanced adiabatic compressed air energy storage(AA-CAES)technology as a join to connect with wind energy generation and an internal-combustion engine(ICE).The capital cost of utilities,energy cost,environmental protection cost and primary energy savings ratio(P E S R)are used as system performance indicators.To fulfill the cooling,heating and power requirements of a district and consider the thermal-electric coupling of ICE and AA-CAES in CCHP system,three operation strategies are established to schedule the dispatch of AA-CAES and ICE:ICE priority operation strategy,CAES priority operation strategy and simultaneous operation strategy.Each strategy leads the operation load of AA-CAES or ICE to improve the energy supply efficiency of the system.Moreover,to minimize comprehensive costs and maximize the P E S R,a novel optimization algorithm based on intelligent updating multi-objective differential evolution(MODE)is proposed to solve the optimization model.Considering the multi-interface characteristic and active management ability of the ICE and AA-CAES,the economic benefits and energy efficiency of the three operation strategies are compared by the simulation with the same system configuration.On a typical summer day,the simultaneous strategy is the best solution as the total cost is 3643 USD and the P E S R is 66.1%,while on a typical winter day,the ICE priority strategy is the best solution as the total cost is 4529 USD and the P E S R is 64.4%.The proposed methodology provides the CCHP based AA-CAES system with a better optimized operation.

Liquid Air Energy Storage for Decentralized Micro Energy Networks with Combined Cooling,Heating,Hot Water and Power Supply

Liquid air energy storage(LAES)has been regarded as a large-scale electrical storage technology.In this paper,we first investigate the performance of the current LAES(termed as a baseline LAES)over a far wider range of charging pressure(1 to 21 MPa).Our analyses show that the baseline LAES could achieve an electrical round trip efficiency(e RTE)above 60%at a high charging pressure of 19 MPa.The baseline LAES,however,produces a large amount of excess heat particularly at low charging pressures with the maximum occurred at~1 MPa.Hence,the performance of the baseline LAES,especially at low charging pressures,is underestimated by only considering electrical energy in all the previous research.The performance of the baseline LAES with excess heat is then evaluated which gives a high e RTE even at lower charging pressures;the local maximum of 62%is achieved at~4 MPa.As a result of the above,a hybrid LAES system is proposed to provide cooling,heating,hot water and power.To evaluate the performance of the hybrid LAES system,three performance indicators are considered:nominal-electrical round trip efficiency(ne RTE),primary energy savings and avoided carbon dioxide emissions.Our results show that the hybrid LAES can achieve a high ne RTE between 52%and 76%,with the maximum at~5 MPa.For a given size of hybrid LAES(1 MW×8 h),the primary energy savings and avoided carbon dioxide emissions are up to 12.1 MWh and 2.3 ton,respectively.These new findings suggest,for the first time,that small-scale LAES systems could be best operated at lower charging pressures and the technologies have a great potential for applications in local decentralized micro energy networks.

Feasibility Analysis of the Operation Strategies for Combined Cooling, Heating and Power Systems (CCHP) based on the Energy-Matching Regime

Although numerous studies have considered the two traditional operation strategies:following the electric load(FEL)and following the thermal load(FTL),for combined cooling,heating,and power(CCHP)systems in different case studies,there are limited theoretical studies on the quantification methods to assess the feasibility of these two strategies in different load demands scenarios.Therefore,instead of a case study,we have undertaken a theoretical analysis of the suitable application scenarios for FEL and FTL strategies based on the energy-matching performance between systems'provision and users'demands.To compare the calculation models of energy saving rate(ESR)for FEL and FTL strategies in the left and right sub-regions of the energy-supply curve,a comprehensive parameter(^)that combines three inherently influential factors(off-design operation parameter,energy-matching parameter,and install capacity coefficient)is defined to determine the optimal installed capacity and feasibility of FEL or FTL strategies quantitatively.The results indicate that greater value of x contribute to a better energy saving performance,and FEL strategy shows better performance than FTL in most load demands scenarios,and the optimal installed capacity occurs when the load demand points were located in different regions of the energy-supply curve.Finally,taking a hotel in Beijing as an example,the value of the optimal install capacity coefficient is 0.845 and the FEL strategy is also suggested,and compared to the maximum install capacity,the average values of the ESR on a typical summer day,transition season,and winter can be enhanced by 3.9%,8.8%,and 1.89%,respectively.

Energetic, economic, and environmental analysis of solid oxide fuel cell-based combined cooling, heating, and power system for cancer care hospital

In this study,energetic,economic,and environmental analysis of solid oxide fuel cell-based combined cooling,heating,and power(SOFC-CCHP)system is proposed for a cancer care hospital building.The energy required for the hospital power,cooling,and heating demands was obtained based on real and detailed field data,which could serve as a reference for future works in the field.These data with a 3D model for the hospital building are constructed and created in eQUEST software to precisely calculate the energy demands of the existing system(baseline case).Then,energetic,economic,and environmental models were developed to compare and assess the performance of the proposed SOFC-CCHP system.The results show that the proposed system can cover about 49% to 77% of the power demand of the hospital with an overall efficiency of 78.3%.Also,the results show that the levelized cost of electricity of the system and its payback period at the designed capacity of the SOFC is 0.087S/kWh and 10 years,respectively.Furthermore,compared to the baseline system of the hospital,the SOFC-CCHP reduces the CO_(2) emission by 89% over the year.The sensitivity analysis showed that a maximum SOFC efficiency of 52%and overall efficiency of 80%are achieved at cell operating temperature of 1027℃ and fuel utilization factor of 0.85.

基于全生命周期评价的冷热电联供系统优化研究

天然气与太阳能互补是提高能源利用率和实现节能减排的有效方法,该文构建一种光-气-储互补的冷热电联供(CCHP)系统。基于全生命周期理论,以一次能源节约率、总污染物减排率为目标函数,建立冷热电联供系统优化模型,应用遗传算法对系统变工况运行下的容量配置进行优化;将物质回收阶段纳入全生命周期评价,并在运输阶段考虑燃料运输。结果表明:经优化后,CCHP系统电跟随(FEL)策略可实现较好的节能减排效益。分供(SP)系统在物质回收阶段对环境的影响微乎其微,CCHP系统燃料运输能耗量远低于SP系统。

Comprehensive power-supply planning for active distribution system considering cooling,heating and power load balance

An active distribution system power-supply planning model considering cooling,heating and power load balance is proposed in this paper.A regional energy service company is assumed to be in charge of the investment and operation for the system in the model.The expansion of substations,building up distributed combined cooling,heating and power(CCHP),gas heating boiler(GHB)and air conditioner(AC)are included as investment planning options.In terms of operation,the load scenarios are divided into heating,cooling and transition periods.Also,the extreme load scene is included to assure the power supply reliability of the system.Numerical results demonstrate the effectiveness of the proposed model and illustrate the economic benefits of applying distributed CCHP in regional power supply on investment and operation.

A multi agent-based optimal control method for combined cooling and power systems with thermal energy storage

Combined cooling,heating and power(CCHP)systems have been considered as a potential energy saving technology for buildings due to their high energy efficiency and low carbon emission.Thermal energy storage(TES)can improve the energy efficiency of CCHP systems,since they reduce the mismatch between the energy supply and demand.However,it also increases the complexity of operation optimization of CCHP systems.In this study,a multi-agent system(MAS)-based optimal control method is proposed to minimize the operation cost of CCHP systems combined with TES.Four types of agents,i.e.,coordinator agents,building agents,energy management agents and optimization agents,are implemented in the MAS to cooperate with each other.The operation optimization problem is solved by the genetic algorithm.A simulated system is utilized to validate the performance of the proposed method.Results show that the operation cost reductions of 10.0%on a typical summer day and 7.7%on a typical spring day are achieved compared with a rule-based control method.A sensitivity analysis is further performed and results show that the optimal operation cost does not change obviously when the rated capacity of TES exceeds a threshold.

含分层储能的冷热电联供系统运行优化

为提高冷热电联供型微电网对可再生能源的消纳能力,解决源-荷的不确定性使得系统运行稳定性降低的问题,提出含分层储能的三级混合时间尺度滚动优化方法。日前优化目标为日运行成本最低;日内上层以燃料成本和蓄热罐功率变化惩罚成本最低为目标对冷热能进行优化,下层以电网交互成本和蓄电池功率变化惩罚成本最低为优化目标对电能进行优化;实时电系统反馈以电系统削峰填谷作用量和功率波动量最低为优化目标;得出最优的系统中各设备的出力计划。结果表明:该优化方法和分层储能能够有效达到削峰填谷的作用,各设备功率波动率均处于较低水平;冬季典型日的日运行成本比日前成本有所降低。

火电厂源侧综合能源系统集成及性能评估研究

本文建立了以火电厂为核心,消纳可再生能源并提供冷热电汽综合能源服务的一套能源系统,通过对整体系统及关键子系统热力性能分析,验证了提出模型和方法的有效性。并研究了一些关键运行参数对系统综合性能的影响,验证了提出模型和方法的有效性和优越性。结果表明:通过改变火电厂的源侧参数,可以提高综合能源系统荷侧的输出量;且生物质转化气对汽轮机发电功率的影响最大。热泵系统的负荷随着进入系统中的给水流量的增大而增大,利用汽轮机中的部分抽汽来驱动热泵系统,虽然发电功率下降了10.88%,但是却为用户提供了16.8MW的热负荷和16.2MW的冷负荷以及27.78t/h的蒸汽量。

基于天然气、地热能和太阳能的多能源耦合系统优化研究

该文基于冷热电三联供系统、地源热泵、光伏和光热耦合的多能源耦合系统,构建了多能源耦合系统全工况优化模型,以能源、经济、环境的综合指标为优化目标,以燃气轮机的额定容量、决定是否运行燃气轮机的关键值、地源热泵供能与建筑负荷的比率、光伏面积和光热面积为优化变量,基于优先满足建筑总热需求的运行策略,以系统冷热电平衡和设备容量为约束,以粒子群算法对优化模型进行优化.提出的优化模型应用于北京的一栋宾馆建筑,得到了优化后系统的最优设备容量与运行策略,为多能源耦合系统的优化提供了参考.

耦合储能电池的冷热电联供系统全工况性能分析

冷热电联供系统具有能源利用效率高、运行调节灵活的优点。设计了耦合储能电池的冷热电联供一体化系统,建立了关键部件的精细化数学模型,研究了压气机和透平的效率、环境温度对联供系统性能的影响。针对典型制冷和供热工况,研究了耦合电池储能的冷热电联供系统全工况热力性能、储能电池的充放电特性。结果表明:环境温度对冷热电联供系统性能具有较大的影响,其最大供热量随着环境温度的降低而下降,最大供冷量随着环境温度的升高而下降。制冷模式下,冷负荷、电负荷全天波动较大,全天平均冷、电负荷仅为额定功率的39.9%左右,全天平均能源利用系数为0.712。供热模式下,典型日全天燃机循环的发电效率、供热系数以及能源利用系数波动很小,且均高于制冷模式下相应的指标。

考虑多能耦合共享储能的微网多智能体混合博弈协调优化

冷热电耦合的共享储能可以更显著地提高微网多种能源的利用效率与消纳水平。然而,多能耦合的共享储能进一步增加了多微网之间协调运行的难度,故而提出了一种考虑多能耦合共享储能的微网多智能体混合博弈协调优化模型。首先,围绕多能耦合共享储能进行建模,从冷、热、电3个维度构建元件的运行模型。其次,提出了一种计及多能耦合共享储能协作的微网混合博弈双层协调调度模型。上层部分为基于主从博弈的微网运营商日内电价优化模型,以微网运营商的日内收益最大化为目标,综合考虑电价上下限约束和购售电价平均值约束,为下层协作运行提供响应电价;下层部分为基于合作博弈的微网间协作运行策略模型,以产消者和共享储能电站的合作成本为目标,综合考虑机组出力上下限约束和功率平衡约束,为上层反馈合作成本用于指导电价优化调整。然后,在混合博弈模型求解时,以电价变动率为收敛判据,同时采用二分法处理电价约束以加速模型求解。最后,采用多智能体协调优化的微网系统验证了所提方法的有效性。

基于压缩空气储能与增强型地热的三联产系统热力学分析

为提升压缩空气储能技术的能量利用率与供能灵活性,基于能量梯级利用原理,提出了一种耦合压缩空气储能与增强型地热技术的冷热电联产系统。通过建立系统的热力学模型,研究了关键运行参数对系统热力学性能的影响规律,并以系统(火用)效率和单位能量成本为目标函数,获得了系统的多目标优化解集。结果表明,膨胀机与换热器是系统高效运行的关键设备,提升这2个设备的运行效率对于系统热力学性能以及输出功量的提升作用显著,采用多目标优化方法得到系统的最优(火用)效率为55.73%,最优单位能量成本为6378.94元/kW,能量效率和相对节能率较设计工况分别提升了6.1%和10.68%。研究结果从热力学和经济学角度为系统的工程应用提供了理论依据。

计及风光储的冷热电联产综合能源系统低碳经济优化

为解决能源危机,中国大力发展综合能源系统,以期进行多能协同互济,实现节能降碳。主要研究计及风光储的冷热电联供系统多目标优化调度问题。首先,从经济和碳排放2个不同的角度出发,建立经济目标函数和环境目标函数,构造考虑风光储的冷热电联供系统多目标优化配置模型以及相应的约束条件;然后,提出增强的非支配排序遗传算法Ⅱ(non-dominated sorting genetic algorithmⅡ,NSGA-Ⅱ),通过引入支配强度和方差因子,提高算法求解效率和求解精度;最后,以辽西某地正在运行的冷热电联供系统为例进行仿真分析,验证本文所提模型和方法的有效性。