Simulation and performance analysis of organic Rankine cycle combined heat and power system

To improve the overall thermal efficiency of the organic Rankine cycle（ ORC）, a simulation study was carried out for a combined heat and power（ CHP） system, using the Redlich-Kuang-Soave（ RKS） equation of state. In the system,R245 fa was selected as the working fluid. A scroll expander was modeled with empirical isentropic expansion efficiency.Plate heat exchangers were selected as the evaporator and the condenser, and detailed heat transfer models were programmed for both one-phase and two-phase regions. Simulations were carried out at seven different heat source temperatures（ 80,90, 100, 110, 120, 130, 140 ℃） in combination with eight different heat sink temperatures（ 20, 25, 30, 35, 40, 45, 50,55 ℃）. Results showthat in the ORC without an internal heat exchanger（ IHE）, the optimum cycle efficiencies are in the range of 7. 0% to 7. 3% when the temperature differences between the heat source and heat sink are in the range of 70 to90 ℃. Simulations on CHP reveal that domestic hot water can be produced when the heat sink inlet temperature is higher than40 ℃, and the corresponding exergy efficiency and overall thermal efficiency are 29% to 56% and 87% to 90% higher than those in the non-CHP ORC, respectively. It is found that the IHE has little effect on the improvement of work output and efficiencies for the CHP ORC.

Modelling and optimization of combined heat and power system in microgrid based on renewable energy

Due to the short distance between the sources of production and consumption,microgrids(MGs)have received considerable attention because these systems involve fewer losses and waste less energy.And another advantage of MGs is that renewable energy sources can be widely used because these resources are not fully available and can provide a part of the required power.The purpose of this research is to model the MG considering the production sources of microturbines,gas turbines and internal combustion engines.Renewable energies such as wind turbines(WTs)and photovoltaic(PV)cells have been used to provide part of the required power and,because of the lack of access to renewable energy sources at all times,energy reserves such as batteries and fuel cells(FCs)have been considered.The power of the microturbine,gas turbine,internal combustion engine,FC and battery in this system is 162,150,90,100 and 225 kW,respectively.After modelling the studied system,optimization was done using the imperialist competitive algorithm to minimize production costs and provide maximum thermal and electrical loads.The maximum production power for PVs is equal to 0.6860 MWh and at this time this value for WTs is equal to 0.3812 MWh,in which case the excess electricity produced will be sold to the grid.

Distributed Real-time State Estimation for Combined Heat and Power Systems

This paper proposes a distributed real-time state estimation(RTSE)method for the combined heat and power systems(CHPSs).First,a difference-based model for the heat system is established considering the dynamics of heat systems.This heat system model is further used along with the power system steady-state model for holistic CHPS state estimation.A cubature Kalman filter(CKF)-based RTSE is developed to deal with the system nonlinearity while integrating both the historical and present measurement information.Finally,a multi-timescale asynchronous distributed computation scheme is designed to enhance the scalability of the proposed method for largescale systems.This distributed implementation requires only a small amount of information exchange and thus protects the privacy of different energy systems.Simulations carried out on two CHPSs show that the proposed method can significantly improve the estimation efficiency of CHPS without loss of accuracy compared with other existing models and methods.

Decentralized State Estimation of Combined Heat and Power System Considering Communication Packet Loss

In order to obtain an accurate state estimation of the operation in the combined heat and power system,it is necessary to carry out state estimation.Due to the limited information sharing among various energy systems,it is practical to perform state estimation in a decentralized manner.However,the possible communication packet loss is seldomly considered among various energy systems.This paper bridges this gap by proposing a relaxed alternating direction method of multiplier algorithm.It can also improve the computation efficiency compared with the conventional alternating direction of the multiplier algorithm.Case studies of two test systems are carried out to show the validity and superiority of the proposed algorithm.

Carbon emission impact on the operation of virtual power plant with combined heat and power system

A virtual power plant （VPP） can realize the aggregation of distributed generation in a certain region, and represent distributed generation to participate in the power market of the main grid. With the expansion of VPPs and ever-growing heat demand of consumers, managing the effect of fluctuations in the amount of available renewable resources on the operation of VPPs and maintaining an economical supply of electric power and heat energy to users have been important issues. This paper proposes the allocation of an electric boiler to realize wind power directly converted for supplying heat, which can not only overcome the limitation of beat output from a combined heat and power （CHP） unit, but also reduce carbon emissions from a VPP. After the electric boiler is considered in the VPP operation model of the combined heat and power system, a multi-objective model is built, which includes the costs of carbon emissions, total operation of the VPP and the electricity traded between the VPP and the main grid. The model is solved by the CPLEX package using the fuzzy membership function in Matlab, and a case study is presented. The power output of each unit in the case study is analyzed under four scenarios. The results show that after carbon emission is taken into account, the output of low carbon units is significantly increased, and the allocation of an electric boiler can facilitate the maximum absorption of renewable energy, which also reduces carbon emissions from the VPP.

Thermo-economic Investigation of an Enhanced Geothermal System Organic Rankine Cycle and Combined Heating and Power System

As a potentially viable renewable energy, Enhanced Geothermal Systems(EGSs) extract heat from hot dry rock(HDR) reservoirs to produce electricity and heat, which promotes the progress towards carbon peaking and carbon neutralization. The main challenge for EGSs is to reduce the investment cost. In the present study, thermo-economic investigations of EGS projects are conducted. The effects of geofluid mass flow rate, wellhead temperature and loss rate on the thermo-economic performance of the EGS organic Rankine cycle(ORC) are studied. A performance comparison between EGS-ORC and the EGS combined heating and power system(CHP) is presented. Considering the CO_(2)emission reduction benefits, the influence of carbon emission trading price on the levelized cost of energy(LCOE) is also presented. It is indicated that the geofluid mass flow rate is a critical parameter in dictating the success of a project. Under the assumed typical working conditions, the LCOE of EGS-ORC and EGS-CHP systems are 24.72 and 16.1 cents/k Wh, respectively. Compared with the EGS-ORC system, the LCOE of the EGS-CHP system is reduced by 35%. EGS-CHP systems have the potential to be economically viable in the future. With carbon emission trading prices of 12.76 USD/ton, the LCOE can be reduced by approximately 8.5%.

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

The increasing pace of urbanization means that cities and global organizations are looking for ways to increase energy efficiency and reduce emissions. Combined cooling, heating, and power （CCHP） systems have the potential to improve the energy generation efficiency of a city or urban region by providing energy for heating, cooling, and electricity simultaneously. The purpose of this study is to estimate the water consumption for energy generation use, carbon dioxide （CO2） and NOx emissions, and economic impact of implementing CCHP systems for five generic building types within the Atlanta metropolitan region, under various operational scenarios following the building thermal （heating and cooling） demands. Operating the CCHP system to follow the hourly thermal demand reduces CO2 emissions for most building types both with and without net metering. The system can be economically beneficial for all building types depending on the price of natural gas, the implementation of net metering, and the cost structure assumed for the CCHP system. The greatest reduction in water consumption for energy production and NOx emissions occurs when there is net metering and when the system is operated to meet the maximum yearly thermal demand, although this scenario also results in an increase in greenhouse gas emissions and, in some cases, cost. CCHP systems are more economical for medium office, large office, and multifamilv residential buildings.

Solution of Combined Heat and Power Economic Dispatch Problem Using Direct Optimization Algorithm

This paper presents the solution to the combined heat and power economic dispatch problem using a direct solution algorithm for constrained optimization problems. With the potential of Combined Heat and Power (CHP) production to increase the efficiency of power and heat generation simultaneously having been researched and established, the increasing penetration of CHP systems, and determination of economic dispatch of power and heat assumes higher relevance. The Combined Heat and Power Economic Dispatch (CHPED) problem is a demanding optimization problem as both constraints and objective functions can be non-linear and non-convex. This paper presents an explicit formula developed for computing the system-wide incremental costs corresponding with optimal dispatch. The circumvention of the use of iterative search schemes for this crucial step is the innovation inherent in the proposed dispatch procedure. The feasible operating region of the CHP unit three is taken into account in the proposed CHPED problem model, whereas the optimal dispatch of power/heat outputs of CHP unit is determined using the direct Lagrange multiplier solution algorithm. The proposed algorithm is applied to a test system with four units and results are provided.

Optimal Scheduling Method of Cogeneration System with Heat Storage Device Based on Memetic Algorithm

Electric-heat coupling characteristics of a cogeneration system and the operating mode of fixing electricity with heat are the main reasons for wind abandonment during the heating season in the Three North area.To improve the wind-power absorption capacity and operating economy of the system,the structure of the system is improved by adding a heat storage device and an electric boiler.First,aiming at the minimum operating cost of the system,the optimal scheduling model of the cogeneration system,including a heat storage device and electric boiler,is constructed.Second,according to the characteristics of the problem,a cultural gene algorithm program is compiled to simulate the calculation example.Finally,through the system improvement,the comparison between the conditions before and after and the simulation solutions of similar algorithms prove the effectiveness of the proposed scheme.The simulation results show that adding the heat storage device and electric boiler to the scheduling optimization process not only improves the wind power consumption capacity of the cogeneration system but also reduces the operating cost of the system by significantly reducing the coal consumption of the unit and improving the economy of the system operation.The cultural gene algorithm framework has both the global evolution process of the population and the local search for the characteristics of the problem,which has a better optimization effect on the solution.

Robust optimal dispatch strategy of integrated energy system considering CHP-P2G-CCS

Integrated energy systems(IESs)can improve energy efficiency and reduce carbon emissions,essential for achieving peak carbon emissions and carbon neutrality.This study investigated the characteristics of the CHP model considering P2G and carbon capture systems,and a two-stage robust optimization model of the electricity-heat-gascold integrated energy system was developed.First,a CHP model considering the P2G and carbon capture system was established,and the electric-thermal coupling characteristics and P2G capacity constraints of the model were derived,which proved that the model could weaken the electric-thermal coupling characteristics,increase the electric power regulation range,and reduce carbon emissions.Subsequently,a two-stage robust optimal scheduling model of an IES was constructed,in which the objective function in the day-ahead scheduling stage was to minimize the start-up and shutdown costs.The objective function in the real-time scheduling stage was to minimize the equipment operating costs,carbon emission costs,wind curtailment,and solar curtailment costs,considering multiple uncertainties.Finally,after the objective function is linearized with a ψ-piecewise method,the model is solved based on the C&CG algorithm.Simulation results show that the proposed model can effectively absorb renewable energy and reduce the total cost of the system.

Combined Electric and Heat System Testbeds for Power Flow Analysis and Economic Dispatch

In combined electric and heat systems,selecting a suitable testbed for power flow analysis or economic dispatch is not easy:a large number of existing testbeds are not opensource,while others are difficult to be reused by other researchers due to the particularity of system scale,topology,and data.In this paper,we present three open-source testbeds with different scales based on practical combined electric and heat systems.To satisfy researchers"specific demands on the system topology and data,we also discuss how to modify testbeds based on existing topologies and data.Researchers can use the testbeds presented in this paper to test their innovative methods for power flow analysis and economic dispatch,and can also design their own testbeds based on the methodology in this paper,using published topologies and data.

Stochastic Accelerated Alternating Direction Method of Multipliers for Hedging Communication Noise in Combined Heat and Power Dispatch

Combined heat and power dispatch(CHPD)opens a new window for increasing operational flexibility and reducing wind power curtailment.Electric power and district heating systems are independently controlled by different system operators;therefore,a decentralized solution paradigm is necessary for CHPD,in which only minor boundary information is required to be exchanged via a communication network.However,a nonideal communication environment with noise could lead to divergence or incorrect solutions of decentralized algorithms.To bridge this gap,this paper proposes a stochastic accelerated alternating direction method of multipliers(SA-ADMM)for hedging communication noise in CHPD.This algorithm provides a general framework to address more types of constraint sets and separable objective functions than the existing stochastic ADMM.Different from the single noise sources considered in the existing stochastic approximation methods,communication noise from multiple sources is addressed in both the local calculation and the variable update stages.Case studies of two test systems validate the effectiveness and robustness of the proposed SAADMM.

Diesel generator exhaust heat recovery fully-coupled with intake air heating for off-grid mining operations:An experimental,numerical,and analytical evaluation

The customarily discarded exhaust from the fossil fuel-based power plants of the off-grid mines holds the thermal potential to fulfill the heating requirement of the underground operation.This present research fills in an important research gap by investigating the coupling effect between a diesel exhaust heat recovery and an intake air heating system employed in a remote mine.An integrative approach comprising analytical,numerical,and experimental assessment has been adapted.The novel analytical model developed here establishes the reliability of the proposed mine heating system by providing comparative analysis between a coupled and a decoupled system.The effect of working fluid variation has been examined by the numerical analysis and the possible improvement has been identified.Experimental investigations present a demonstration of the successful lab-scale implementation of the concept and validate the numerical and analytical models developed.Successful deployment of the fully coupled mine heating system proposed here will assist the mining industry on its journey towards energy-efficient,and sustainable mining practices through nearly 70%reduction in fossil fuel consumption for heating intentions.

The ecosystem of Lake Kenon:past and present(Transbaikal Territory,Russia)

Present-day conditions of the Lake Kenon ecosystem are determined by a combination of natural and anthropogenic factors. We have estimated the effects of a complex of factors on the condition of the abiotic environment and on specific biological components in the lake ecosystem. Change in biogenic load has caused an increase in the role of phytoplankton in the general balance of organic matter during the high-water period. Charophytes are the main dominants of bottom vegetation. Anthropogenic load has caused a decrease in both fish species and fish capacity. The lake application as a water reservoir-cooler has influenced the average annual water mineralization （from 420 mg/L to 530.0 mg/L with a maximum 654 mg/L in 1993） and fluctuations in its hydrochemical composition. The present composition of the lake is sulfate-hydrocarbonate-chloride calcium-sodic-magnesium in character. S（Y44 content is twice as much as the maximum permissible concentration in fishery waters. Water drainage from an ash disposal area to the lake has caused an increase in chemical-element concentrations including the heavy metals. Hg concentration in Perca fluviatilis muscles is 0.5 9g/g dry wt. Thus, understanding directions in the ecosystem of the water reservoir-cooler under changing hydrological conditions will let us forecast the consequences of new combined heat and power plant operation.

Prediction of the Behavior of a Power System Using Root Cause Failure Analysis

The thermo-economic performance of a gas turbine is simulated using a fish bone technique to characterize the major equipment failure causes.Moreover a fault tree analysis and a Pareto technique are implemented to identify the related failure modes,and the percentage and frequency of failures,respectively.A pump 101 and drier 301 belonging to the Tabriz Petrochemical Company are considered for such analysis,which is complemented with a regression method to determine a behavioral model of this equipment over a twenty-year period.Research findings indicate that 81%of major failure factors in production equipment are related to the executive procedures(24%),human error(22%),poor quality of materials and parts(20%),and lack of personnel training(15%).

Operation Strategy Analysis and Configuration Optimization of Solar CCHP System

This paper proposed a new type of combined cooling heating and power(CCHP)system,including the parabolic trough solar thermal(PTST)power generation and gas turbine power generation.The thermal energy storage subsystem in the PTST unit provides both thermal energy and electrical energy.Based on the life cycle method,the configuration optimization under eight operation strategies is studied with the economy,energy,and environment indicators.The eight operation strategies include FEL,FEL-EC,FEL-TES,FEL-TES&EC,FTL,FTL-EC,FTL-TES,and FTL-TES&EC.The feasibility of each strategy is verified by taking a residential building cluster as an example.The indicators under the optimal configuration of each strategy are compared with that of the separate production(SP)system.The results showed that the PTST-CCHP system improves the environment and energy performance by changing the ratio of thermal energy and electric energy.The environment and energy indicators of FEL-TES&EC are superior to those of FTL-TES&EC in summer,and the results are just the opposite in winter.The initial annual investment of the PTST-CCHP system is higher than that of the SP system,but its economic performance is better than that of the SP system with the increase of life-cycle.

Dynamic Simulation and Performance Analysis on Multi-Energy Coupled CCHP System

Although the Combined Cooing,Heating and Power System(hereinafter referred to as“CCHP”)improves the capacity utilization rate and energy utilization efficiency,single use of CCHP system cannot realize dynamic matching between supply and demand loads due to the unbalance features of the user’s cooling and heating loads.On the basis of user convenience and wide applicability of clean air energy,this paper tries to put forward a coupled CCHP system with combustion gas turbine and ASHP ordered power by heat,analyze trends of such parameters as gas consumption and power consumption of heat pump in line with adjustment of heating load proportion of combustion gas turbine,and optimize the system ratio in the method of annual costs and energy environmental benefit assessment.Based on the analysis of the hourly simulation and matching characteristics of the cold and hot load of the 100 thousand square meter building,it is found that the annual cost of the air source heat pump is low,but the energy and environmental benefits are poor.It will lead to 6.35%shortage of cooling load in summer.Combined with the evaluation method of primary energy consumption and zero carbon dioxide emission,the coupling system of CHHP and air source heat pump with 41%gas turbine load ratio is the best configuration.This system structure and optimization method can provide some reference for the development of CCHP coupling system.

Optimal Scheduling for Combined District Heating and Power Systems Using Subsidy Strategies

The ongoing development of cogeneration technology has promoted public awareness on the integration of different types of energy systems.Integration of power and heating systems is the most common approach for energy transmission.The heat and power coupling of combined heat and power(CHP)units constrains the improvement of flexibility to accommodate more wind power,especially in winter.To address this problem,electrical boilers(EBs)are utilized as independent heat sources in one heat station to enhance their flexibility.This paper proposes a subsidy based bi-level optimal model.The objective of the upper problem is to minimize the operating cost,while the lower problem is to maximize the benefits of CHP and EBs based on the subsidy signals sent by the power system operator(PSO).The bi-level model is reformulated as a single-level linear problem by Karush Kuhn Turck(KKT)conditions and recast to a mix integer quadratic program using strong duality theory.Numerical results performed on an IEEE six-bus system with a eight-node district heating system validate the proposed model.The results demonstrate that the subsidy strategies can make the EB and CHP units operate according to the system operators’preferences to accommodate more wind power.

CO_(2)Plume Geothermal(CPG)Systems for Combined Heat and Power Production:an Evaluation of Various Plant Configurations

CO_(2) Plume Geothermal(CPG)systems are a promising concept for utilising petrothermal resources in the context of a future carbon capture utilisation and sequestration economy.Petrothermal geothermal energy has a tremendous worldwide potential for decarbonising both the power and heating sectors.This paper investigates three potential CPG configurations for combined heating and power generation(CHP).The present work examines scenarios with reservoir depths of 4 km and 5 km,as well as required district heating system(DHS)supply temperatures of 70℃ and 90℃.The results reveal that a two-staged serial CHP concept eventuates in the highest achievable net power output.For a thermosiphon system,the relative net power reduction by the CHP option compared with a sole power generation system is significantly lower than for a pumped system.The net power reduction for pumped systems lies between 62.6%and 22.9%.For a thermosiphon system with a depth of 5 km and a required DHS supply temperature of 70℃,the achievable net power by the most beneficial CHP option is even 9.2%higher than for sole power generation systems.The second law efficiency for the sole power generation concepts are in a range between 33.0%and 43.0%.The second law efficiency can increase up to 63.0%in the case of a CHP application.Thus,the combined heat and power generation can significantly increase the overall second law efficiency of a CPG system.The evaluation of the achievable revenues demonstrates that a CHP application might improve the economic performance of both thermosiphon and pumped CPG systems.However,the minimum heat revenue required for compensating the power reduction increases with higher electricity revenues.In summary,the results of this work provide valuable insights for the potential development of CPG systems for CHP applications and their economic feasibility.

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.