The economics of a fuel cell cogeneration system using a by-product hydrogen stream

A site-specific fuel cell cogeneration study was conducted. A molten carbonate fuel cell (MCFC) system, sized at a nominal 25 MW (d.c.) to use an available by-product hydrogen stream, was compared with the alternative of purchased electricity and the use of natural gas to produce steam. The economic analysis objectives were to determine; the savings due to the reduced amount of purchased energy; the cost/benefit ratio; and the payback period for the MCFC cogeneration system. Another objective was to determine if the high capital cost of the first prototype MCFC plant would require a commercialization subsidy to make it attractive to an industrial owner. It was found that a commercialization subsidy would be required for the initial high cost prototype plant, but this technology promises an energy utilization of 84% of the input fuel heating value which represents a strong incentive for commercialization.     

Fuel consumption analysis of a residential cogeneration system using a solid oxide fuel cell with regulation of heat to power ratio

Solid oxide fuel cells are suitable for heat and power cogeneration systems for their high electric efficiency and heat to power output ratio. Although commercial solid oxide fuel cells use heat from the exhaust to obtain hydrogen through natural gas reformation, recent progress in hydrogen generation technologies allows us to use pure hydrogen instead of natural gas, and utilize the exhaust heat for other purposes. A residential cogeneration system using a solid oxide fuel cell is proposed in this study, where the heat to power output ratio is varied to match the electric and hot water demands of a residence in Japan. Seasonal fuel consumption of the system is calculated and compared against a similar system without hydrogen addition, and to the conventional system. The proposed system shows a considerable reduction in fuel consumption, while almost reaching complete independence from the power grid.     

Utilizing coke oven gases as a fuel for a cogeneration system based on high temperature proton exchange membrane fuel cell; energy,exergy and economic assessment

Based on a high temperature proton exchange membrane fuel cell (HT-PEMFC), a cogeneration system is proposed to produce heat and power. The system includes a coke oven gas steam reformer, a water gas shift reactor, and an afterburner. The system is analyzed in detail considering the energy, exergy and economic viewpoints. The analyses reveal the importance of HT-PEMFC in the system and according to the results, 9.03 kW power is generated with energy and exergy efficiencies of 88.2% and 26.2%, respectively and the total product unit cost is calculated as 91.8 $/GJ. Through a parametric study the effects on system performance are studied of such variables as the current density, fuel cell and reformer operating temperatures, and cathode stoichiometric ratio. It is found that an increase in the fuel cell temperature and/or a decrease in the reformer temperature enhance the exergy efficiency. The exergy efficiency is also maximized at the cathode stoichiometric ratio of 2.4. By performing a two-objective optimization using genetic algorithm, the best operating point is determined at which the exergy efficiency is (32.86%) and the total product unit cost is (78.68 $/GJ).     

Dynamic optimization of a cogeneration plant for an industrial application with two different hydrogen embedding solutions

Seasonal storage of hydrogen is a valuable option today increasingly considered in order to optimize cogeneration plants under continuous operation in an incentive framework where electricity sale to the national grids is becoming less economically profitable than in the past. The paper concerns the numerical study and optimization of a cogeneration plant installed in an industrial site having an availability of hydrogen over a continuous time scale, to meet the energy needs and mitigating the environmental impact of the plant operation by reducing the energy withdrawal from traditional sources. Two alternatives are analyzed into detail: the former regards energy production through an internal combustion engine, this last properly controlled to be fueled with blends of natural gas and increasing percentages of hydrogen, the latter concerning the addition of fuel cells to the proposed layout to further reduce the electricity integration by the grid. The dynamic response of the cogeneration system under examination is dynamically evaluated to efficiently fulfill the industrial loads to be fulfilled. First, optimization is performed by implementing a PID controller to better track the industrial demand of electric energy. The main results of this solution reveal a ?81% reduction of excess electricity, a ?7% reduction of natural gas consumed but a 47% raise of CO₂ emissions due to the increase in thermal integration. Then, an additional energy generation from fuel cells is assumed. An economic analysis is carried out for each of the implemented configurations. The adoption of fuel cells, despite requiring a greater initial investment, allows obtaining a SPB of 1,4 years (? 16%), 1,17 Mln € of avoided costs (? 18,5%) and 1320 t/year of CO₂ emissions avoided (? 95%) with respect to the initial layout.     

An investigation of a household size trigeneration running with hydrogen

This study examined the performance and emission characteristics of a household size trigeneration based on a diesel engine generator fuelled with hydrogen comparing to that of single generation, cogeneration using ECLIPSE simulation software. In single generation simulation, the engine genset is used to produce electricity only and the heat from the engine is rejected to the atmosphere. In cogeneration and trigeneration, in addition to the electricity generated from the genset, the waste heat rejected from the hot exhaust gases and engine cooling system, is captured for domestic hot water supply using heat exchangers and hot water tank; and a part of the waste heat is used to drive absorption cooling in trigeneration. Comparisons have been made for the simulated results of these three modes of operation for hydrogen and diesel. The results prove that hydrogen is a potential energy vector in the future which is a key to meeting upcoming stringent greenhouse gases emissions. The study show that hydrogen has very good prospects to achieve a better or equal performance to conventional diesel fuel in terms of energetic performance, and a near zero carbon emission, depending on the life cycle analysis of the way the hydrogen is produced. The results also show enormous potential fuel savings and massive reductions in greenhouse gas emissions per unit of useful energy outputs with cogeneration and trigeneration compared with that of single generation.     

Study of a fuel cell network with water electrolysis for improving partial load efficiency of a residential cogeneration system

A fuel cell energy network which connects hydrogen and oxygen gas pipes, electric power lines and exhaust heat output lines of the fuel cell cogeneration for individual houses, respectively, is analysed. As an analysis case, the energy demand patterns of individual houses in Tokyo are used, and the analysis method for minimization of the operational cost using a genetic algorithm is described. The fuel cell network system of an analysis example assumed connecting the fuel cell cogeneration of five houses. If energy is supplied to the five houses using the fuel cell energy network proposed in this paper, 9% of city gas consumption will be reduced by the maximum from the results of analysis. Two per cent included with 9% is an effect of introducing water electrolysis operation of the fuel cells, corresponding to partial load operation of fuel cell cogeneration. Copyright © 2005 John Wiley & Sons, Ltd.     

Using next generation nuclear power reactors for development of a techno‐economic model for hydrogen production

Nuclear and hydrogen are considered to be the most promising alternatives energy sources in terms of meeting future demand and providing a CO?‐free environment, and interest in the development of more cost‐effective hydrogen production plants is increasing—and nuclear‐powered hydrogen generation plants may be a viable alternative. This paper is a report on investigating the application of new generation nuclear power plants to hydrogen production and development of an associated techno‐economic model. In this paper, theoretical and computational assessments of generations II, III+, and IV nuclear power plants for hydrogen generation scenarios have been reported. Technical analyses were conducted on each reactor type—in terms of the design standard, fuel specification, overnight capital cost, and hydrogen generation. In addition, a theoretical model was developed for calculating various hydrogen generation parameters, and it was then extended to include an economic assessment of nuclear power plant‐based hydrogen generation. The Hydrogen Economic Evaluation Program originally developed by the International Atomic Energy Agency was used for calculating various parameters, including hydrogen production and storage costs, as well as equity, operation and maintenance (O&M), and capital costs. The results from each nuclear reactor type were compared against reactor parameters, and the ideal candidate reactor was identified. The simulation results also verified theoretically proven results. The main objective of the research was to conduct a prequalification assessment for a cogeneration plant, by developing a model that could be used for technical and economic analysis of nuclear hydrogen plant options. It was assessed that high‐temperature gas‐cooled reactors (HTGR‐PM and PBR200) represented the most economical and viable plant options for hydrogen production. This research has helped identify the way forward for the development of a commercially viable, nuclear power‐driven, hydrogen generation plant.     

Impact of Australian natural gas and coal bed methane composition on PEM fuel cell performance

Several PEM fuel cell systems are currently being marketed or developed as natural gas fuelled stationary power generation or cogeneration systems. Whilst each of these may perform adequately when fuelled with methane, the composition of natural gas varies widely around the world, according to the source and even the season. This study investigated the variation in composition of fuel gas supplied in pipeline systems around Australia and how its chemical composition may affect the performance of PEM fuel cell systems than employ steam reforming, shift and selective preferential oxidation to convert the fuel gas to hydrogen. The study showed that the performance of the fuel cell system is affected by the chemical composition and that ammonia formed from gases with high nitrogen concentrations could limit the applicability of PEM fuel cells, and should be taken into account when manufacturers specify the allowable fuel gas compositions for their systems.     

Study on capacity optimization of PEM fuel cell and hydrogen mixing gas-engine compound generator

Development of a small-scale power source not dependent on commercial power may result in various effects. For example, it may eliminate the need for long distance power-transmission lines, and mean that the amount of green energy development is not restricted to the dynamic characteristics of a commercial power grid. Moreover, the distribution of the independent energy source can be optimized with regionality in mind. This paper examines the independent power supply system relating to hydrogen energy. Generally speaking, the power demand of a house tends to fluctuate considerably over the course of a day. Therefore, when introducing fuel cell cogeneration into an apartment house, etc., low-efficiency operations in a low-load region occur frequently in accordance with load fluctuation. Consequently, the hybrid cogeneration system (HCGS) that uses a solid polymer membrane-type fuel cell (PEM-FC) and a hydrogen mixture gas engine (NEG) together to improve power generation efficiency during partial load of fuel cell cogeneration is proposed. However, since facility costs increase, if the HCGS energy cost is not low compared with the conventional method, it is disadvantageous. Therefore, in this paper, HCGS is introduced into 10 household apartments in Tokyo, and the power generation efficiency, carbon dioxide emissions and optimal capacity of a boiler and heat storage tank are investigated through analysis. Moreover, the system characteristics change significantly based on the capacity of PEM-FC and NEG that compose HCGS. Therefore, in this study, the capacity of PEM-FC and that of NEG are investigated, as well as the power generation efficiency, carbon dioxide emissions and the optimal capacity of a boiler and heat storage tank. Analysis revealed that the annual average power generation efficiency when the capacity of PEM-FC and NEG is 5 kW was 27.3%. Meanwhile, the annual average power generation efficiency of HCGS is 1.37 times that of the PEM-FC independent system, and 1.28 times that of the NEG independent system, respectively.     

Performance assessment of a direct steam solar power plant with hydrogen energy storage: An exergoeconomic study

Power generation and its storage using solar energy and hydrogen energy systems is a promising approach to overcome serious challenges associated with fossil fuel-based power plants. In this study, an exergoeconomic model is developed to analyze a direct steam solar tower-hydrogen gas turbine power plant under different operating conditions. An on-grid solar power plant integrated with a hydrogen storage system composed of an electrolyser, hydrogen gas turbine and fuel cell is considered. When solar energy is not available, electrical power is generated by the gas turbine and the fuel cell utilizing the hydrogen produced by the electrolyser. The effects of different working parameters on the cycle performance during charging and discharging processes are investigated using thermodynamic analysis. The results indicate that increasing the solar irradiation by 36%, leads to 13% increase in the exergy efficiency of the cycle. Moreover, the mass flow rate of the heat transfer fluid in solar system has a considerable effect on the exergy cost of output power. Solar tower has the highest exergy destruction and capital investment cost. The highest exergoeconomic factor for the integrated cycle is 60.94%. The steam turbine and PEM electrolyser have the highest share of exergoeconomic factor i.e., 80.4% and 50%, respectively.     

Exergetic and thermoeconomic analyses of diesel engine powered cogeneration: Part 1 – Formulations

This paper is part 1 of the study on the energy, exergy, and exergoeconomic analysis of diesel engine powered cogeneration (DEPC). Part 1 presents the formulation developed for such a comprehensive analysis while part 2 is an application of the developed formulation that considers an actual cogeneration power plant. Compression ignition engine powered cogeneration application is among the most efficient simple cycle power generation plants where the efficiencies are around 50%. The DEPC is mostly preferred in regions where natural gas is not available or not preferable because of high unit prices. In this paper, a DEPC plant is considered with all associated components. Mass, energy, and exergy balances are applied to each system component and subsystem. Exergy balance formulations are aimed to yield exergy destructions. Various efficiencies based on both energy and exergy methods and the performance assessment parameters are defined for both the system components and the entire cogeneration plant. The formulations for the cost of products, and cost formation and allocation within the system are developed based on both energy and exergy (i.e., exergoeconomic analysis). The cost analyses formulated here have significant importance to obtain the optimum marketing price of the product of thermal systems to maximize the benefit and/or minimize the cost.     

Numerical modeling of an automotive derivative polymer electrolyte membrane fuel cell cogeneration system with selective membranes

Cogeneration power plants based on fuel cells are a promising technology to produce electric and thermal energy with reduced costs and environmental impact. The most mature fuel cell technology for this kind of applications are polymer electrolyte membrane fuel cells, which require high-purity hydrogen.The most common and least expensive way to produce hydrogen within today's energy infrastructure is steam reforming of natural gas. Such a process produces a syngas rich in hydrogen that has to be purified to be properly used in low temperature fuel cells. However, the hydrogen production and purification processes strongly affect the performance, the cost, and the complexity of the energy system.Purification is usually performed through pressure swing adsorption, which is a semi-batch process that increases the plant complexity and incorporates a substantial efficiency penalty. A promising alternative option for hydrogen purification is the use of selective metal membranes that can be integrated in the reactors of the fuel processing plant. Such a membrane separation may improve the thermo-chemical performance of the energy system, while reducing the power plant complexity, and potentially its cost. Herein, we perform a technical analysis, through thermo-chemical models, to evaluate the integration of Pd-based H₂-selective membranes in different sections of the fuel processing plant: (i) steam reforming reactor, (ii) water gas shift reactor, (iii) at the outlet of the fuel processor as a separator device. The results show that a drastic fuel processing plant simplification is achievable by integrating the Pd-membranes in the water gas shift and reforming reactors. Moreover, the natural gas reforming membrane reactor yields significant efficiency improvements.     

Thermoeconomic assessment of an absorption refrigeration and hydrogen-fueled diesel power generator cogeneration system

The thermoeconomic assessment of a cogeneration application that uses a reciprocating diesel engine and an ammonia–water absorption refrigeration system for electrical power and cold production from hydrogen as fuel is presented. The purpose of the assessment is to get both exergetic and exergoeconomic costs of the cogeneration plant products at different load conditions and concentrations of hydrogen–diesel oil blends. The exhaust gas of the reciprocating diesel engine is used as an energy source for an ammonia–water absorption refrigeration system. The reciprocating diesel engine was simulated using the Gate Cycle™ software, and the ammonia–water absorption refrigeration system simulation and the thermoeconomic assessment were carried out using the Engineering Equation Solver software (EES). The results show that engine combustion is the process of higher exergy destruction in the cogeneration system. Increased hydrogen concentration in the fuel increases the system exergetic efficiency for all load conditions. Exergy destruction in the components of the ammonia–water absorption refrigeration system is increased with increasing load due to the rise of heat transfer. At intermediate and high loads energy efficiency is increased in the power system, and low values of unit exergetic cost and competitive specific exergoeconomic costs are noticed. The cogeneration system operation at intermediate and high engine loads was proven to be feasible.     

Cogeneration in a solid-wastes power-station: a case-study

Nowadays, natural gas is viewed as the solution to the problem of energy supply for Latin America, Europe and North America for the next few decades; Brazil is increasingly becoming dependent upon the Bolivian natural-gas supply — many industries and some entrepreneurs are deciding to construct industrial cogeneration systems and new thermal power-stations burning natural gas because of its low environmental impact and attractive price. However, natural gas is a finite resource: this will cause, in the future, an increase of its unit price. This paper details questions involved in the energy generation and presents solid-waste burning as a possible alternative fuel for the future, especially in the context of cogeneration practice in which the thermal and electric energy are used primarily for the industries located in an industrial district. Two cogeneration schemes are proposed for the burning of municipal solid wastes, associated or not with natural gas, and their technical and economic feasibilities are examined.     

High-performance gas–electricity cogeneration using a direct carbon solid oxide fuel cell fueled by biochar derived from camellia oleifera shells

Direct carbon solid oxide fuel cells (DC-SOFCs) are promising for generating electricity cleanly and efficiently from solid carbon fuel. Biochar from Camellia oleifera shells is used in a tubular electrolyte-supported 2-cell DC-SOFC stack with a yttrium-stabilized zirconia (YSZ) electrolyte and silver–gadolinium-doped ceria (Ag-GDC) as symmetrical electrodes. The DC-SOFC exhibits comparable electrical performance to the same cell operated on hydrogen fuel and can cogenerate CO and electricity when fueled by biochar. The gas–electricity cogeneration performance of the DC-SOFC is tested under constant-current discharge in terms of electrical power output, CO output rate and purity, electrical conversion efficiency, and gas–electrical cogeneration conversion efficiency. The purity of the output CO can reach more than 80%. Considering the chemical energy of CO a part of the output power, the energy conversion efficiency of >70% is attained. Furthermore, the gas–electricity cogeneration performance is relatively stable before the biochar fuel is exhausted.     

Parametric analysis of a solar energy based multigeneration plant with SOFC for hydrogen generation

Renewable energy-based hydrogen production plants can offer potential solutions to both ensuring sustainability in energy generation systems and designing environmentally friendly systems. In this combined work, a novel solar energy supported plant is proposed that can generate hydrogen, electricity, heating, cooling and hot water. With the suggested integrated plant, the potential of solar energy usage is increased for energy generation systems. The modeled integrated system generally consists of the solar power cycle, solid oxide fuel cell plant, gas turbine process, supercritical power plant, organic Rankine cycle, cooling cycle, hydrogen production and liquefaction plant, and hot water production sub-system. To conduct a comprehensive thermodynamic performance analysis of the suggested plant, the combined plant is modeled according to thermodynamic equilibrium equations. A performance assessment is also conducted to evaluate the impact of several plant indicators on performance characteristics of integrated system and its sub-parts. Hydrogen production rate in the suggested plant according to the performance analysis performed is realized as 0.0642 kg/s. While maximum exergy destruction rate is seen in the solar power plant with 8279 kW, the cooling plant has the lowest exergy destruction rate as 1098 kW. Also, the highest power generation is obtained from gas turbine cycle with 7053 kW. In addition, energetic and exergetic efficiencies of solar power based combined cycle are found as 56.48% and 54.06%, respectively.     

Development and modelling of a novel electricity-hydrogen energy system based on reversible solid oxide cells and power to gas technology

Compared to the conventional thermal units and electrolytic devices, reversible fuel cells have very high efficiencies on both fuel cell mode of generating electricity and electrolysis mode of producing hydrogen or CH_x. However, previous studies about fuel cells and its benefits of power to gas are not fully investigated in the electricity-gas energy system. Moreover, state-of-art studies indicate that hydrogen could be directly injected to the existing natural gas (NG) pipeline within an amount of 5%–20%, which are considered to make a slight influence on the natural gas technologies. This work proposes a novel electricity-hydrogen energy system based on reversible solid oxide cells (RSOCs) to demonstrate the future vision of multi-energy systems on integrating multiple energy carriers such as electricity, pure hydrogen, synthetic natural gas (SNG) and mixed gas of H₂-natural gas. The P2G processes of RSOC are sub-divided modelled by power to H₂ (P2H) and power to SNG (P2SNG). The co-electrolysis/generation processes and time-dependent start-up costs are considered within a unit commitment model of RSOC. The proposed electricity-hydrogen energy system optimization model is formulated as mixed-integer linear programming (MILP), where the H₂-blended mixed gas flow is linearized by an incremental linearize relaxation technic. The aim of the optimization is to reduce the energy cost and enhance the system's ability to integrate sufficient renewables through NG networks. Besides quantified the benefits of renewable level and H₂ injection limit on the P2G process, the numerical results show that RSOC combined with H₂/SNG injection results in productive economic and environmental benefits through the energy system.     

Effects of gas recycle on performance of solid oxide fuel cell power systems

An energy analysis of solid oxide fuel cell (SOFC) power systems with gas recycles fed by natural gas is carried out. Simple SOFC system, SOFC power systems with anode and cathode gas recycle respectively and SOFC power system with both anode and cathode gas recycle are compared. Influences of reforming rate, air ratio and recycle ratio of electrode exhaust gas on performance of SOFC power systems are investigated. Net system electric efficiency and cogeneration efficiency of these power systems are given by a calculation model. Results show that internal reforming SOFC power system can achieve an electrical efficiency of more than 44% and a system cogeneration efficiency including waste heat recovery of 68%. For SOFC power system with anode gas recycle, an electrical efficiency is above 46% and a cogeneration efficiency of 88% is obtained. In the case of cathode gas recycle, an electrical efficiency and a cogeneration efficiency is more than 51% and 78% respectively. Although SOFC system with both anode and cathode gas is more complicated, the electrical efficiency of it is close to 52%.     

用资源的观点评价能源利用项目

在评价能源动力工程项目时应该采用综合的评价方法，考虑技术、经济和环境等因素。叙述了一种基于总资源系统的综合评价方法，将生产中消耗的(包括污染掉的)空气、水和燃料等都折算成资源，并从社会平均边际削减成本的角度计算了利用资源对社会造成的外部成本。指出，计算资源的价值时必须包括其外部成本，并计入最终的总成本。文中还陈述了综合评价方法的原理，并以某燃天然气的燃气轮机联合循环热电联产系统为例子，与燃煤热电联产系统进行了比较。     

以燃气轮机为核心的多功能能源系统基本形式与构成

以燃气轮机为核心的多功能能源动力系统有不同功能和不同能源的两大类型.本文概述了不同功能的总能系统类型的基本形式,如纯产功的、热工领域的多联产、多领域的多功能以及无公害能源系统等多功能系统,并阐述它们的主要特点与过程构成.概述了不同能源的总能系统类别的基本形式,如燃用气体燃料和液体燃料、煤炭、核能、可再生能源、氢能以及多能源互补等多功能能源系统,并阐述它们的主要特点与过程构成.