Analysis of an intermediate-temperature proton-conducting SOFC hybrid system

The performance of an intermediate-temperature proton-conducting solid oxide fuel cell (pSOFC) hybrid system is investigated in this work. The hybrid system consists of a 20-kW pSOFC, a micro gas turbine (MGT), and heat exchangers. Heat exchangers are used to recover waste heat from pSOFC and MGT. The performance of the system is analyzed by using Matlab/Simulink/Thermolib. Flow rates of air and hydrogen are controlled by assigning different stoichiometric ratio (St). St considered in this study is between 2 and 3.5 for air, and between 1.25 and 1.45 for hydrogen. Results show that the combined heat and power (CHP) efficiency increases as the fuel St decreases or air St increases. This is because lowering fuel St means fewer fuel will be wasted from the fuel cell stack, so the CHP efficiency increases. On the other hand, as air St increases, the amount of recovered waste heat increases, so does the CHP efficiency.     

Indicators for sustainable energy development: Brazil's case study

This article summarizes the results of the project on indicators for sustainable energy development (ISED) in Brazil. The project's aim was to present energy related economic, social and environmental data to policy makers in a coherent and consistent form, showing interlinkages, time‐series and cross‐sectoral analyses and assess energy policy. Two priority areas assessed by these indicators, regarding the country's energy supply and demand, helped in the identification of a number of energy policy options that focused on specific aspects of the country's energy sector. On the supply side, these options include the development and stimulation of renewable energy, such as small‐scale hydroelectric, wind, solar photovoltaic power and bagasse cogeneration; stimulation of programmes for ethanol use as automotive fuel and sugarcane bagasse cogeneration; and implementation of natural gas‐fired, combined heat and power (CHP) plants. On the demand side, policy options include: the full implementation of the law on efficiency standards for appliances; expansion of utility investment in end‐use energy efficiency; adoption of targets and protocols to reduce energy intensity in the industrial sector; improvement of passenger transport efficiency; and the creation of a fund to improve energy affordability for the poor.     

Simulation Study of a PEM Fuel Cell System with Steam Reforming

Abstract

This article summarizes the results of a study for a 100 kWe DC electrical power PEM fuel cell system. The system consists of a pre-steam reformer, a steam reformer, high and low temperature shift reactors, a preferential oxidation reactor, a PEM fuel cell, a combustor, and an expander. Acceptable net electrical efficiency levels can be achieved via intensive heat integration within the PEM fuel cell system. The calculations take into account the auxiliary equipment such as pumps, com pressors, heaters, coolers, heat exchangers and pipes. The process simulation package “Aspen-HYSYS 3.1’’ has been used. The operation parameters of the reactors have been determined considering all the technical limitations involved. A gasoline type hydrocarbon fuel has been studied as hydrogen rich gas source. Thermal efficiencies have been calculated for all of the major system components for selected operation conditions. The fuel cell stack efficiency has been calculated as a function of cell numbers (500, 750, 1000, and 1250 cells). Efficiencies of all of the major system components along with auxiliary unit efficiencies determine the net electrical efficiency of the PEM fuel cell system. The obtained net electrical efficiency levels are between 34 (500 cells) to 41% (1250 cells).     

Biogas upgrading and utilization from ICEs towards stationary molten carbonate fuel cell systems

Biogas production from anaerobic digestion has increased rapidly in the last years, in many parts of the world, mainly due to its local scale disposition and to its potential on greenhouse gases (GHG) emissions mitigation. Biogas can be used as fuel for combined heat and power systems (CHP), in particular for internal combustion engines (ICEs). In recent investigations, fuel cells have been considered as alternative CHP systems. In the present article, two different energy conversion systems are compared: a 1.4 MW class MCFC system, running on pipeline natural gas, and an in situ ICE, running on biogas. In the first case, biogas is considered as a source fuel to obtain upgraded gas to be injected in the natural gas grid. In such scenario, the location of the fuel cell power plant is no longer strictly connected to the anaerobic digester site. Several energy balances are evaluated, considering different upgrading techniques and different biogas methane/carbon dioxide ratios.     

Exergy and economic analysis of organic Rankine cycle hybrid system utilizing biogas and solar energy in rural area of China

Due to the existing huge biogas resource in the rural area of China, biogas is widely used for production and living. Cogeneration system provides an opportunity to realize the balanced utilization of the renewable energy such as biogas and solar energy. This article presented a numerical investigation of a hybrid energy-driven organic Rankine cycle (ORC) cogeneration system, involving a solar ORC and a biogas boiler. The biogas boiler with a module of solar parabolic trough collectors (PTCs) is employed to provide heat source to the ORC via two distinct intermediate pressurized circuits. The cogeneration supplied the power to the air-condition in summer condition and hot water, which is heated in the condenser, in winter condition. The system performance under the subcritical pressures has been assessed according to the energy–exergy and economic analysis with the organic working fluid R123. The effects of various parameters such as the evaporation and condensation temperatures on system performance were investigated. The net power generation efficiency of the cogeneration system is 11.17%, which is 25.8% higher than that of the base system at an evaporation temperature 110°C. The exergy efficiency of ORC system increases from 35.2% to 38.2%. Moreover, an economic analysis of the system is carried out. The results demonstrate that the profits generated from the reduction of biogas fuel and electricity consumption can lead to a significant saving, resulting in an approximate annual saving from $1,700 to $3,000. Finally, a case study based on the consideration of typical rural residence was performed, which needs a payback period of 7.8 years under the best case.     

Cogeneration potential in Indian sugar mills: a case study

The Indian sugar industry has massive potential for the cogeneration of electrical power. The sugar manufacturing process generates bagasse as a byproduct from cane-crushing. This bagasse can be used as a fuel for the boilers employed in steam raising for the process use and cogeneration. In this study, the potential for power cogeneration in a typical plant under the existing boiler-turbine configuration has been estimated. An alternative configuration requiring capital investment in machinery has also been studied. The cost of cogenerating power, including the cost of fuel, operations and capital services wherever necessary, has been calculated for both these cases, using a linear optimisation method. The exercise allows for the use of multiple fuels, namely bagasse and coal, for cogeneration throughout the year including the cane-crushing season and the off-season. The per unit supply price of cogenerated power thus computed has been compared with the utility's own cost with a view to selling the surplus cogenerated power to the grid.     

Evaluation of different CHP options for refinery integration in the context of a low carbon future

This study presents a comparison of different concepts for delivering combined heat and power (CHP) to a refinery in Norway. A reference case of producing high pressure steam from natural gas in boilers and electricity in a combined cycle power plant, is compared to a: (1) natural gas fueled CHP without any CO₂ capture; (2) hydrogen fueled CHP with hydrogen produced from steam methane reforming (SMR); (3) hydrogen fueled CHP with hydrogen produced from autothermal reforming (ATR); and finally (4) natural gas fueled CHP with postcombustion CO₂ removal. The options are compared on the basis of first law efficiency, emissions of CO₂ and a simplified cash flow evaluation. Results show that in terms of efficiency the standard natural gas fueled CHP performs better than the reference case as well as the options with carbon capture. The low carbon options in turn offer lower emissions of greenhouse gases while maintaining the same efficiency as the reference case. The cash flow analysis shows that for any option, a certain mix of prices is required to produce a positive cash flow. As expected, the relationship between natural gas price and electricity price affects all options. Also the value of heat and CO₂ emissions plays an important role.     

Investigation of sustainable energy alternatives for powering remote communities in northern Ontario

ABSTRACT

Remote communities in the North of Ontario survive in isolation as their proximity to the southern industrial sector of the province limits their accessibility to the major grid. The lack of grid connection has led to antiquated methods of power generation which pollute the environment and deplete the planet of its natural resources. Aside from the primary means of electricity generation being by diesel generators, generation infrastructure is deteriorating due to age and the stagnation of the power supply has led to communities facing load restrictions. These challenges may be resolved by introducing clean energy alternatives and providing a fuel blend option. The primary energy sources investigated in this research are solar, wind, and hydrogen. To assess the viability of these energy production methods in Northern communities, an exergy analysis is employed as it utilizes both the first and second law of thermodynamics to determine systems’ efficiency and performance in the surroundings. Local weather patterns were used to determine the viability of using wind turbines, solar panels and/or hydrogen fuel cells in a remote community. Through analysis of the resources available at the community, it was determined that the hydrogen fuel cell was best suited to provide clean energy to the community. Wind resulted in low efficiency in the range of 2–3% while solar efficiencies resulted in ranges of 18 – 19%, as the seasonal variations between the three years is not very great. Due to the higher operating efficiencies observed of the PV panels it would also be an attractive alternative to diesel generators however, the lack of consistent operation above 30% efficiency throughout the year, resulted in hydrogen fuel cells being a better alternative.     

全国碳市场启动后北京热电行业低碳运行管理方式研究

随着四大热电中心的建成投产,北京市完成了由燃机替代煤机的转变,实现了更加智能化的清洁能源发电供热。2013年北京市碳市场启动运行,给刚起步的燃气供热机组运行赋予了更广阔和更深远的意义;2017年12月19日,以发电行业为突破口,全国碳排放交易体系正式启动,北京市热电行业低碳运行管理意义重大而深远。本文以燃气热电联产机组运行数据为基础,通过计算分析,提出燃气热电联产机组清洁、高效、低碳运行方式,为全国碳市场启动后,北京乃至全国热电行业低碳运行管理提供经验借鉴。     

Performance assessment of integrated energy systems for HVAC applications

In this article, energy and exergy analyses are conducted for two integrated systems which can be used in HVAC applications. These two systems are analyzed for the cases of single generation, cogeneration and trigeneration, and their performances are evaluated through energy and exergy efficiencies. The parametric studies are performed to investigate the effects of using cogeneration and extended to trigeneration on the system performance. To perform the comparisons between the systems for multiple options, the same amounts of outputs (in terms of electricity, heating, cooling) are produced for all systems. The energy analyses of systems 1 and 2 show a great benefit for moving from single generation to trigeneration, with the trigeneration efficiencies of 83.5% and 87.2%, respectively, and single generation efficiencies of 47% for both systems. However, the exergy analyses show that trigeneration may not always become more efficient than single generation, particularly for system 1, due to the fact that the trigeneration exergy efficiency is 38.7% and the corresponding single generation efficiency is 44.3%. For system 2, the trigeneration exergy efficiency is 52.7% while the single generation efficiency becomes 44.3%. Depending on the type of cogeneration or cogeneration design, the system can be more efficient.     

Strategies for emission reduction from thermal power plants

Major polluters of man's environment are thermal power stations (TPS) and power plants, which discharge into the atmosphere the basic product of carbon fuel combustion, CO2, which results in a build-up of the greenhouse effect and global warm-up of our planet's climate. This paper is intended to show that the way to attain environmental safety of the TPS and to abide by the decisions of the Kyoto Protocol lies in raising the efficiency of the heat power stations and reducing their fuel consumption by using nonconventional thermal cycles. Certain equations have been derived to define the quantitative interrelationship between the growth of efficiency of the TPS, decrease in fuel consumption and reduction of discharge of dust, fuel combustion gases, and heat into the environment. New ideas and new technological approaches that result in raising the efficiency of the TPS are briefly covered: magneto-hydrodynamic resonance, the Kalina cycle, and utilizing the ambient heat by using, as the working medium, low-boiling substances.     

燃料电池发电系统安全与标准化

燃料电池因具有高效、节能、环保等优点,在电动汽车、分布式电站、便携式备用电源等方面具有广泛的应用前景,而燃料电池的安全标准是燃料电池产品市场准入的重要保证。燃料电池发电系统的安全涉及机械危险、电气危险、热危险、化学危害、物理危险、设备故障危险、因不适当的人机工程学原理而导致的危险及人机界面危险、合理预见的误用、环境条件危险、污染等方面。本文介绍了国内外燃料电池发电系统安全技术以及标准化的现状。     

Development of a fuel cell propulsion system for the existing Mercedes B-Class 160 of petrol driven car

This paper presents a theoretical comparison between fuel cell (FC) power train and conventional petrol driven propulsion system. FC has potential to reduce the CO₂-emissions from road. However, FC power trains require energy storing device, to meet the peak power during extreme drive situations and also able to recover the kinetic energy of the vehicle during break operation. The proposed system includes a polymer electrolyte membrane fuel cell (PEMFC) based drive train and a super capacitor connected in parallel. The system is designed and dimensioned for a conventional petrol driven propulsion system of the Mercedes B-Class160. The feasibility study also includes comparison between the existing conventional systems. It is shown that although FC power train is heavier compared to existing system, urban performance is better and produces no CO₂ and other harmful emissions.     

Sizing and performance analysis of standalone hybrid photovoltaic/battery/hydrogen storage technology power generation systems based on the energy hub concept

In this study, the optimal sizing and performance analysis of a standalone integrated solar power system equipped with different storage scenarios to supply the power demand of a household is presented. One of the main purposes when applying solar energy resource is to face the increasing environmental pollutions resulting from fossil fuel based electricity sector. To this end, and to compare and examine two energy storage technologies (battery and hydrogen storage technology), three storage scenarios including battery only, hydrogen storage technology only and hybrid storage options are evaluated. An optimization framework based on Energy Hub concept is used to determine the optimum sizes of equipment for the lowest net present cost (NPC) while maintaining the system reliability. It was determined that the most cost effective and reliable case is the system with hybrid storage technology. Also, the effects of solar radiation intensity, the abatement potential of CO₂ emissions and converting excess power to hydrogen on the system’s performance and economics, were investigated and a few noticeable findings were obtained.     

Heat dissipation characteristic in the intake grille and radiator of a fuel cell vehicle

ABSTRACT

In this study, a three-dimension (3D) computational model was proposed to investigate the flow and heat transfer characteristics of the intake grilles of two different fuel cell vehicles. The models of the intake grilles were constructed according to the actual sizes of two vehicles, namely, Roewe 950 and Toyota Mirai, considering the heat dissipation unit to simplify the heat transfer model of the vehicle. The results showed that relative to Roewe 950, Mirai intake air flow rate was approximately 10% higher, the heat transfer capacity was approximately 7% higher, and the intake grille area was larger. The coolant outlet temperature of Mirai was lower than that of Roewe 950, which was beneficial for the long term and stable operation of a fuel cell. This comparative study provided guidance for the intake grille and radiator design of fuel cell vehicles. The only difference between fuel cell vehicles on the market and conventional vehicles was that in the former, the internal combustion engine was replaced with a fuel cell stack, which had insufficient heat transfer capacity because of the reducing temperature difference. Increasing the intake grille area and the heat exchange capacity of the radiator were the key issues for the development of fuel cell vehicles. In this study, an optimal window opening angle of the radiator fin of 23° provided a maximal heat transfer coefficient.     

Toward a CO2 zero emissions energy system in the Middle East region

Climate change and energy security are global challenges requiring concerted attention and action by all of the world’s countries. Under these conditions, energy supplier and exporter countries in the Middle East region are experiencing further challenges, such as increasing domestic energy demand while energy exports have to concurrently be kept at high levels. Middle East countries process the largest proven oil and gas reserves in the world and contribute a large fraction of the world’s CO₂ emissions from the use of these as fuels both domestically and internationally. This paper addresses different policies that could dramatically change the future course of the Middle East region toward a zero CO₂ emission energy system. To this aim, an integrated energy supply–demand model has been developed to analyze required commitments including renewable energy and energy efficiency targets and the potential of nuclear power, all of which should need to be considered in order to reduce CO₂ emissions by 2100. The results indicate that nearly 43% of the global energy of the Middle East region can be supplied from non-fossil fuel resources in 2100.     

Energy and exergy analysis of a solid-oxide fuel cell power generation system for an aerial vehicle (ISSA- 2015–139)

This paper presents the performance of the solid-oxide fuel cell/gas turbine hybrid power generation system with heat recovery waste unit based on the energy and exergy analyses. The effect of air inlet temperature and air/fuel ratio on exergy destruction and network output is determined. For the numerical calculations, air inlet temperature and air fuel ratio are increased from 273 to 373 K and from 40 to 60, respectively. The results of the numerical calculations bring out that total exergy destruction quantity increases with the increase of air inlet temperature and air/fuel ratio. Furthermore, the maximum system overall first and second law efficiencies are obtained in the cases of air inlet temperature and air/fuel ratio equal to 273 K and 60, respectively, and these values are 62.09% and 54.91%.     

Experimental investigation into performance of integrated hotbox in 1-kW solid oxide fuel cell system

An experimental investigation is performed to evaluate the performance of an integrated hotbox in a 1-kW solid oxide fuel cell (SOFC) system fed by natural gas. The integrated hotbox comprises all the main balance of plant components of an SOFC system, i.e. afterburner, reformer, and heat exchanger, and it not only reduces the physical size of the system but also yields improved system efficiency. The experimental results show that under optimal operating conditions, the combined H₂ and CO content of the reformate gas is approximately 70%, while both anode and cathode in-gas temperatures are around approximately 750°C.     

CO2 capture from combined cycles integrated with Molten Carbonate Fuel Cells

In this paper Molten Carbonate Fuel Cells (MCFCs) are considered for their potential application in carbon dioxide separation when integrated into natural gas fired combined cycles. The MCFC performs on the anode side an electrochemical oxidation of natural gas by means of CO₃^2? ions which, as far as carbon capture is concerned, results in a twofold advantage: the cell removes CO₂ fed at the cathode to promote carbonate ion transport across the electrolyte and any dilution of the oxidized products is avoided.The MCFC can be “retrofitted” into a combined cycle, giving the opportunity to remove most of the CO₂ contained in the gas turbine exhaust gases before they enter the heat recovery steam generator (HRSG), and allowing to exploit the heat recovery steam cycle in an efficient “hybrid” fuel cell + steam turbine configuration. The carbon dioxide can be easily recovered from the cell anode exhaust after combustion with pure oxygen (supplied by an air separation unit) of the residual fuel, cooling of the combustion products in the HRSG and water separation. The resulting power cycle has the potential to keep the overall cycle electrical efficiency approximately unchanged with respect to the original combined cycle, while separating 80% of the CO₂ otherwise vented and limiting the size of the fuel cell, which contributes to about 17% of the total power output so that most of the power capacity relies on conventional low cost turbo-machinery. The calculated specific energy for CO₂ avoided is about 4 times lower than average values for conventional post-combustion capture technology. A sensitivity analysis shows that positive results hold also changing significantly a number of MCFC and plant design parameters.