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.

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.

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 U+0028 CCHP U+0029 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 U+0028 TOPSIS U+0029 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. © 2014 Chinese Association of Automation.

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.

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.

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.

Biomass Combined Heat and Power Generation for Anticosti Island: A Case Study

Combined heat and power (CHP) plants (co-generation plants) using biomass as fuel, can be an interesting alternative to the predominant electrical heating in Canada. The biomass-fueled boiler provides heat for the steam cycle which in turn generates electricity from the generator connected to the steam turbine. In addition, heat from the process is supplied to a district heating system. The heat can be extracted from the system in a number of ways, by using a back-pressure steam turbine, an extraction steam turbine or by extracting heat directly from the boiler. The objective of the paper is the design, modeling and simulation of such CHP plant. The plant should be sized for providing electric-ity and heat for the Anticosti Island community in Quebec.

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.

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.

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.

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.

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.

Low-carbon Operation of Combined Heat and Power Integrated Plants Based on Solar-assisted Carbon Capture

Accelerating the development of renewable energy and reducing CO_(2)emissions have become a general consensus and concerted action of all countries in the world. The electric power industry, especially thermal power industry, is the main source for fossil energy consumption and CO_(2)emissions. Since solvent-based post-combustion carbon capture technology would bring massive extra energy consumption, the application of solar-assisted carbon capture technology has attracted extensive attention. Due to the important role of coal-fired combined heat and power plants for serving residential and industrial heating districts, in this paper, the low-carbon operation benefits of combined heat and power integrated plants based on solar-assisted carbon capture(CHPIP-SACC) are fully evaluated in heat and power integrated energy system with a high proportion of wind power. Based on the selected integration scheme, a linear operation model of CHPIP-SACC is developed considering energy flow characteristics and thermal coupling interaction of its internal modules. From the perspective of system-level operation optimization, the day-ahead economic dispatch problem based on a mix-integer linear programming model is presented to evaluate the low-carbon benefits of CHPIP-SACC during annual operation simulation. The numerical simulations on a modified IEEE 39-bus system demonstrate the effectiveness of CHPIP-SACC for reducing CO_(2)emissions as well as increasing the downward flexibility. The impact of different solar field areas and unit prices of coal on the low-carbon operation benefits of CHPIP-SACC is studied in the section of sensitivity analysis.

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.

Combined heat and power economic dispatch problem using firefly algorithm

Cogeneration units, which produce both heat and electric power, are found in many process industries. These industries also consume heat directly in addition to electricity. The cogeneration units operate only within a feasible zone. Each point within the feasible zone consists of a specific value of heat and electric power. These units are used along with other units, which produce either heat or power exclusively. Hence, the economic dispatch problem for these plants to optimize the fuel cost is quite complex and several classical and meta-heuristic algo- rithms have been proposed earlier. This paper applies the firefly algorithm, which is inspired by the behavior of fireflies which attract each other based on their luminosity. The results obtained have been compared with those obtained by other methods earlier and showed a marked improvement over the earlier methods.

Distributed energy management for interconnected operation of combined heat and power-based microgrids with demand response

From the perspective of transactive energy, the energy trading among interconnected microgrids(MGs) is promising to improve the economy and reliability of system operations. In this paper, a distributed energy management method for interconnected operations of combined heat and power(CHP)-based MGs with demand response(DR) is proposed. First, the system model of operational cost including CHP, DR, renewable distributed sources, and diesel generation is introduced, where the DR is modeled as a virtual generation unit. Second, the optimal scheduling model is decentralized as several distributed scheduling models in accordance with the number of associated MGs. Moreover, a distributed iterative algorithm based on subgradient with dynamic search direction is proposed. During the iterative process, the information exchange between neighboring MGs is limited to Lagrange multipliers and expected purchasing energy. Finally,numerical results are given for an interconnected MGs system consisting of three MGs, and the effectiveness of the proposed method is verified.

Combined heat and power economic dispatch problem using the invasive weed optimization algorithm

Cogeneration units which produce both heat and electric power are found in many process industries. These industries also consume heat directly in addition to electricity. The cogeneration units operate only within a feasible zone. Each point within the feasible zone consists of a specific value of heat and electric power. These units are used along with other units which produce either heat or power exclusively. Hence the economic dispatch problem for these plants optimizing the fuel cost is quite complex and several classical and meta-heuristic algo- rithms have been proposed earlier. This paper applies the invasive weed optimization algorithm which is inspired by the ecological process of weed colonization and distribu- tion. The results obtained have been compared with those obtained by other methods earlier and showed a marked improvement over earlier ones.

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.

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.