Fuel cell buses in the Stockholm CUTE project—First experiences from a climate perspective

This paper aims to share the first experiences and results from the operation of fuel cell buses in Stockholm within the Clean Urban Transport for Europe (CUTE) project. The project encompasses implementation and evaluation of both a hydrogen fuel infrastructure and fuel cell vehicles in nine participating European cities. In total, 27 fuel cell buses, 3 in each city, are in revenue service for a period of 2 years.The availability of the fuel cell buses has been better than expected, about 85% and initially high fuel consumption has been reduced to approximately 2.2 kg H₂/10 km corresponding to 7.5 l diesel equivalents/10 km. Although no major breakdowns have occurred so far, a few cold climate-related issues did arise during the winter months in Stockholm.     

Lessons learned from infrastructure operation in the CUTE project

The project CUTE (Clean Urban Transport for Europe) comprised the operation of 27 fuel cell buses and their hydrogen infrastructures for two years under everyday conditions.     

A first report on the attitude towards hydrogen fuel cell buses in Stockholm

Surveys of the attitude towards hydrogen fuel cell buses among passengers and bus drivers were performed in Stockholm during the autumn of 2004. Another field survey of the attitude of the fuel cell bus passengers is planned towards the end of the CUTE Stockholm project, i.e. during the autumn of 2005.     

A follow-up and conclusive report on the attitude towards hydrogen fuel cell buses in the CUTE project—From passengers in Stockholm to bus operators in Europe

This paper concerns the attitude towards the fuel cell bus and the hydrogen technology used in the CUTE project, represented by two passenger surveys performed in Stockholm, a survey performed among drivers in four cities and final statements as well as recommendations for future projects by project partners.     

The benefits of ethanol use for hydrogen production in urban transportation

The purpose of this paper is to describe the benefits of sugar cane ethanol in Brazil, appointing the productivity of this type of fuel based on hectares of plantation, its carbon dioxide cycle and the contribution to reduce the greenhouse effect. In the following step the uses of ethanol for hydrogen production by steam reforming is analyzed and some comparison with natural gas steam reforming is performed. The sugar cane industry in Brazil, in a near future, in the hydrogen era, could be modified according to our purpose, since besides the production of sugar, and ethylic and anhydric alcohol, Brazilian sugar cane industry will also be able to produce biohydrogen.Fuel cells appear like a promising technology for energy generation. Among several technologies in the present, the PEMFC (proton exchange membrane fuel cell) is the most appropriate for vehicles application, because it combines durability, high power density, high efficiency, good response and it works at relatively low temperatures. Besides that it is easy to turn it on and off and it is able to support present vibration in vehicles. A PEMFC's problem is the need of noble catalysts like platinum. Another problem is that CO needs to be in low concentration, requiring a more clean hydrogen to avoid fuel cell deterioration.One part of this paper was developed in Stockholm, where there are some buses within the CUTE (clean urban transport for Europe) project that has been in operation with FC since January 2004. Another part was developed in Guaratinguetá, Brazil. Brazil intends to start up a program of FC buses. As conclusion, this paper shows the economical analysis comparing buses moved by fuel cells using hydrogen by different kinds of production. Electrolyze with wind turbine, natural gas steam reforming and ethanol steam reforming.     

Performance analysis of proton-exchange membrane fuel cell stacks used in Beijing urban-route buses trial project

Fuel cell hybrid vehicles' sustained development and commercialization are contingent on the reliability and durability of the fuel cell engines. In August 2008, official trial of the three proton-exchange membrane (PEM) fuel cell hybrid city buses commenced in a commercial-operation urban-route in Beijing for one year. In this paper, data from the performance analysis of the automotive fuel cells used in those city buses are presented and analyzed. The durability and reliability of the fuel cell engines under realistic conditions were evaluated by analyzing the standard deviation of the single-cell fuel cell voltages and by estimating the voltage vs. current characteristics obtained using the recursive least squares fitting method. After studying the degradation status by analyzing fitted results from the measured data, it is concluded that the fuel cell engines' performance meets the standard imposed by the driving conditions of the Beijing urban-routes, but that their performance degradation necessitates maintenance in order to ensure normal operation.     

Plug-in hybrid fuel cell vehicles market penetration scenarios

The main objective of this research is to analyze the impact of the market share increase of hydrogen based road vehicles in terms of energy consumption and CO₂, on today's Portuguese light-duty fleet. Actual yearly values of energy consumption and emissions were estimated using COPERT software: 167112 TJ of fossil fuel energy, 12213 kton of CO₂ emission and 141 kton of CO, 20 kton of HC, 46 kton of NO_x and 3 kton of PM. These values represent 20–40% of countries total emissions. Additionally to base fleet, three scenarios of introduction of 10–30% fuel cell vehicles including plug-in hybrids configurations were analysed. Considering the scenarios of increasing hydrogen based vehicles penetration, up to 10% life cycle energy consumption reduction can be obtained if hydrogen from centralized natural gas reforming is considered. Full life cycle CO₂ emissions can also be reduced up to 20% in these scenarios, while local pollutants reach up to 85% reductions. For the purpose of estimating road vehicle technologies energy consumption and CO₂ emissions in a full life cycle perspective, fuel cell, conventional full hybrids and hybrid plug-in technologies were considered with diesel, gasoline, hydrogen and biofuel blends. Energy consumption values were estimated in a real road driving cycle and with ADVISOR software. Materials cradle-to-grave life cycle was estimated using GREET database adapted to Europe electric mix. The main conclusions on CO₂ full life cycle analysis is that light-duty vehicles using fuel cell propulsion technology are highly dependent on hydrogen production pathway. The worst scenario for the current Portuguese and European electric mix is hydrogen produced from on-site electrolysis (in the refuelling stations). In this case full life cycle CO₂ is 270 g/km against 190 g/km for conventional Diesel vehicle, for a typical 150,000 km useful life.     

Optimal vehicle control strategy of a fuel cell/battery hybrid city bus

In this article, an optimal vehicle control strategy based on a time-triggered controller area network (TTCAN) system for a polymer electrolyte membrane (PEM) fuel cell/nickel-metal hydride (Ni-MH) battery powered city bus is presented. Aiming at improving the fuel economy of the city bus, the control strategy comprises an equivalent consumption minimization strategy (ECMS) and a braking energy regeneration strategy (BERS). On the basis of the introduction of a battery equivalent hydrogen consumption model incorporating a charge-sustaining coefficient, an analytical solution to the equivalent consumption minimization problem is given. The proposed strategy has been applied in several city buses for the Beijing Olympic Games of 2008. Results of the “China city bus typical cycle” testing show that, the ECMS and the BERS lowered hydrogen consumption by 2.5% and 15.3% respectively, compared with a rule-based strategy. The BERS contributes much more than the ECMS to the fuel economy, because the fuel cell system does not leave much room for the optimal algorithm in improving the efficiency.     

Analysis of reformer furnace tubes for hydrogen production using radiative zonal model

Reformer tubes are commonly used in furnaces to produce hydrogen and synthesis gas in the refining, petrochemical and fertilizer industries. An optimum arrangement and dimensions of the reformer tubes could be obtained from a mathematical modeling. In the present study, a comparison of different tube sizes is presented based on the well-established radiation zonal analysis in the furnace beside mass, momentum, and energy balance in the reactor tubes. For the practical case studies, three Cr–Ni alloy stainless steel tubes were selected to analyze different tube dimensions including diameter, thickness and tube spacing with the same inlet process feed, fuel consumption and catalyst weight. It is shown that for three industrial tube materials a 20% increase in the tube diameter causes a 20% increase in the tube thickness, 10–20% decrease in furnace length (according to the design procedure) and 3–6% decrease in methane conversion. The results of another analysis show that a 5–9% decrease in the fuel consumption is followed by a 20% decrease in the tube diameter for the same amount of hydrogen production for three cases. Moreover, the three tube materials were compared in accordance to the fuel consumption. In all cases minimum tube thickness is desirable.     

Fuel consumption rates of passenger cars in China: Labels versus real-world

Recently, China has implemented many policy measures to control the oil demand of on-road vehicles. In 2010, China started to report the fuel consumption rates of light-duty vehicles tested in laboratory and to require new vehicles to show the rates on window labels. In this study, we examined the differences between the test and real-world fuel consumption of Chinese passenger cars by using the data reported by real-world drivers on the internet voluntarily. The sales-weighted average fuel consumption of new cars in China in 2009 was 7.80 L/100 km in laboratory and 9.02 L/100 km in real-world, representing a difference of 15.5%. For the 153 individual car models examined, the real-world fuel consumption rates were −8 to 60% different from the test values. The simulation results of the International Vehicle Emission model show that the real-world driving cycles in 22 selected Chinese cities could result in −8 to 34% of changes in fuel consumption compared to the laboratory driving cycle. Further government effort on fuel consumption estimates adjustment, local driving cycle development, and real-world data accumulation through communication with the public is needed to improve the accuracy of the labeling policy.     

Fuel consumption from vehicles of China until 2030 in energy scenarios

Estimation of fuel (gasoline and diesel) consumption for vehicles in China under different long-term energy policy scenarios is presented here. The fuel economy of different vehicle types is subject to variation of government regulations; hence the fuel consumption of passenger cars (PCs), light trucks (Lts), heavy trucks (Hts), buses and motor cycles (MCs) are calculated with respect to (i) the number of vehicles, (ii) distance traveled, and (iii) fuel economy. On the other hand, the consumption rate of alternative energy sources (i.e. ethanol, methanol, biomass-diesel and CNG) is not evaluated here. The number of vehicles is evaluated using the economic elastic coefficient method, relating to per capita gross domestic product (GDP) from 1997 to 2007. The Long-range Energy Alternatives Planning (LEAP) system software is employed to develop a simple model to project fuel consumption in China until 2030 under these scenarios. Three energy consumption decrease scenarios are designed to estimate the reduction of fuel consumption: (i) ‘business as usual’ (BAU); (ii) ‘advanced fuel economy’ (AFE); and (iii) ‘alternative energy replacement’ (AER). It is shown that fuel consumption is predicted to reach 992.28 Mtoe (million tons oil equivalent) with the BAU scenario by 2030. In the AFE and AER scenarios, fuel consumption is predicted to be 734.68 and 600.36 Mtoe, respectively, by 2030. In the AER scenario, fuel consumption in 2030 will be reduced by 391.92 (39.50%) and 134.29 (18.28%) Mtoe in comparison to the BAU and AFE scenarios, respectively. In conclusion, our models indicate that the energy conservation policies introduced by governmental institutions are potentially viable, as long as they are effectively implemented.     

Experimental investigation of gasoline fumigation in a single cylinder direct injection (DI) diesel engine

In the presented study, the effects of gasoline fumigation have been investigated experimentally in a single cylinder direct injection (DI) diesel engine. Gasoline has been introduced into the inlet air flow using an elementary carburetor and no other modification on the engine has been done. The effects of 2%, 4%, 6%, 8% and 10% (by vol.) gasoline fumigation have been investigated experimentally at the speeds of (900–1600) (rpm) and at the selected compression ratios of (18–23). From the experimental results it is determined that by application of gasoline fumigation effective power output increases at the levels of 4–9%, effective efficiency increases by approximately 1.5–4% and specific fuel consumption decreases by approximately 1.5–4%. It is also determined that 4–6% fumigation ratio range is the most favorable percentage interval of gasoline at the selected compression ratios for this engine. Because cost of gasoline is higher than diesel fuel in Turkey as well as in many of the other countries and the decrease ratio of specific fuel consumption is low, gasoline fumigation is not economic for this engine. In the presented study, heat balance tests have also been performed for 18 and 21 compression ratios. The heat balance has been investigated experimentally in respect of effective power, heat rejected to the cooling water, heat lost through exhaust, and other losses (unaccounted-for losses). Heat lost through exhaust decreases until 4–6% gasoline fumigation ratios and after these fumigation ratios it starts to increase because of increasing exhaust gas temperature. Heat rejected to the cooling water decreases at low fumigation ratios, but at high fumigation ratios it increases. Other losses generally exhibit an increasing tendency at low fumigation ratios.     

Analysis and integration of fuel cell combined cycles for development of low-carbon energy technologies

Integrated and combined cycles (ICC, CC) traditionally involve gas and steam turbines only. The paper analyses the further integration of high-temperature fuel cells (FC) having high electrical efficiency reaching up to 60% compared with 30–35% for most gas turbines. The previous research on FC hybrids indicates achieving high efficiencies and economic viability is possible. The ICC of various FC types—their performance and the potential for utilisation of renewables—are analysed considering also power generation capacity and site heat integration context. Further research and development with industrial relevance are outlined focusing on CO₂ emissions reduction.     

A prototype of a fuel cell PEM emulator based on a buck converter

After a brief introduction about fuel cell systems, and their modelling, this paper proposes a possible solution to emulate a proton exchange membrane fuel cell (PEM-FC) system by using a DC–DC buck converter. The fuel cell system, including all its auxiliaries and related control systems, is emulated by a buck converter realized experimentally and controlled in the DSPACE environment. The realization of the buck converter allows the behaviour of any fuel cells to be easily emulated since only the modification of the control law of the switch is necessary. The proposed emulator can be applied easily to other fuel cell systems if the polarization curve has the same current rate and maximum power. In this way it is possible to utilize the converter and perform the necessary tests to optimize a fuel cell system by avoiding the waste of hydrogen and the purchase of cells as well as any cell damage. With regard to current other types of emulators, the one presented here has the following characteristics: (1) all the auxiliaries of the system have been considered, each including its own control system, as in a real FCS, (2) the converter is a classical buck converter with a free-wheeling diode and is designed to have a high bandwidth and to be practically always in conduction mode (discontinuous mode appears only at very low currents) (3) the voltage control is made by a space-state controller, able to fix properly the closed loop poles of the system, thus guaranteeing the desired bandwidth of the control system and (4) it can be used in laboratory as a stand-alone low-cost system for design and experimental purposes.     

Adaptive supervisory control strategy of a fuel cell/battery-powered city bus

This paper presents an adaptive supervisory control strategy for a fuel cell/battery-powered city bus to fulfill the complex road conditions in Beijing bus routes. An equivalent consumption minimization strategy (ECMS) is firstly proposed to optimize the fuel economy. The adaptive supervisory control strategy is exploited based on this, incorporating an estimating algorithm for the vehicle accessorial power, an algorithm for the battery charge-sustaining and a Recursive Least Squares (RLS) algorithm for fuel cell performance identification. Finally, an adaptive supervisory controller (ASC) considering the fuel consumption minimization, the battery charge-sustaining and the fuel cell durability has been implemented within the hybrid city buses. Results in the “China city bus typical cycle” testing and the demonstrational program of Beijing bus routes are presented, demonstrating that this approach provides an improvement of fuel economy along with robustness and ease of implementation. However, the fuel cell system does not leave much room for the optimal strategy to promote the fuel economy. Benefits may also result in a prolongation of the fuel cell working life, which needs to be verified in future.     

Is the public willing to pay for hydrogen buses? A comparative study of preferences in four cities

This paper presents results from the international AcceptH2 study (http://www.accepth2.com) of acceptability and preferences for hydrogen fuel cell (FC) buses. Using the contingent valuation method, this paper compares public willingness to pay (WTP) for the air pollution reductions associated with a scenario of large-scale introduction of hydrogen (H₂) FC buses in four cities: Berlin, London, Luxembourg and Perth. Results indicate that bus users in all cities have a positive WTP for H₂ buses, and that values (adjusted to the cost of living in each city) are very similar across geographical locations (ranging from WTP an extra €0.29 to €0.35 per single bus fare). Non-bus users were also interviewed in London and Perth, in order to capture values for the whole populations in these cities. Combined results for bus users and non-bus users confirm that overall residents in these cities are willing to pay extra (in taxes) to support the large-scale introduction of H₂-buses.     

Long-term trends of electric efficiencies in electricity generation in developing countries

This analysis provides time-series data on electric efficiencies for 138 countries and regions, covering all fossil fuels for the period 1971–2005, with an emphasis on non-Organization for Economic Cooperation and Development (OECD) countries. Fossil fuel consumption for electricity generation in non-OECD countries now exceeds that in the OECD. The historical performance of the top five non-OECD consumers of each fossil fuel for which reliable data are available is presented and discussed. For each fuel, the countries that lead the world in efficiency are used for benchmarks; bringing the rest of the world up to these standards would result in energy savings of 26 EJ (equivalent to 5% of global energy consumption) and CO₂ emissions reduction of 2.1 Pg (equivalent to 8% of global CO₂ emissions). Coal showed the largest potential margin of improvement for both energy and CO₂, with possible savings equivalent to 3% of current global energy consumption and 5% of global CO₂ emissions. The gap in electric efficiency between OECD and non-OECD countries over the past 35 years has widened for coal-fired generation, stayed relatively constant for natural gas, but has shrunk for petroleum. The results show the very gradual nature of overall efficiency improvements and the significant differences among regions and countries.     

Importance of integrated strategies and innovations for commercial breakthrough of fuel cells

Fuel cell based energy systems are a potential large-scale future energy option. The key challenge for fuel cells is to reach a market breakthrough which in turn requires a major cost reduction from the present level. Using a combined learning and diffusion model we have investigated effective integrated strategies that combine optimally R&D and market measures to decrease the expenditure and time needed to reach the breakeven point. The results indicate that major efforts in R&D for enhancing fuel cell innovations such as the European fuel cell and hydrogen joint technology effort would be economically well justified. Such efforts could save several billion dollars in the market deployment efforts otherwise required. Through a balanced and integrated technology push and market pull effort the time to breakthrough could similarly be reduced by 60–70%.     

Effect of ignition timing and compression ratio on the performance of a hydrogen–ethanol fuelled engine

This paper presents the results obtained of a compression ignition engine (modified to run on spark ignition mode) fuelled with hydrogen–ethanol dual fuel combination with different percentage substitutions of hydrogen (0–80% by volume with an increment of 20%) under variable compression ratio conditions (i.e. 7:1, 9:1 and 11:1) by varying the spark ignition timing at a constant speed of 1500 rpm. The various engine performance parameters studied were brake specific fuel consumption, brake mean effective pressure and brake thermal efficiency. It was found from the present study that for specific ignition timing the brake mean effective pressure and the brake thermal efficiency increases with the increase of hydrogen fraction in ethanol and all hydrogen substitutions showed the maximum increase in brake thermal efficiency and reduction in brake specific fuel consumption value at around 25^° CA advanced ignition timing. The best operating conditions were obtained at a compression ratio of 11:1 and the optimum fuel combination was found to be 60–80% hydrogen substitution to ethanol.     

Hydrogen refueling stations and fuel cell buses four year operational analysis under real-world conditions

Worldwide about 550 hydrogen refueling stations (HRS) were in operation in 2021, of which 38% were in Europe. With their number expected to grow even further, the collection and investigation of real-world station operative data are fundamental to tracking their activity in terms of safety issues, performances, maintenance, reliability, and energy use. This paper analyses the parameters that characterize the refueling of 350 bar fuel cell buses (FCB) in five HRS within the 3Emotion project. The HRS are characterized by different refueling capacities, hydrogen supply schemes, storage volumes and pressures, and operational strategies. The FCB operate over various duty cycles circulating on urban and extra-urban routes. From data logs provided by the operators, a dataset of four years of operation has been created. The results show a similar hydrogen amount per fill distribution but quite different refueling times among the stations. The average daily mass per bus and refueling time are around 14.62 kg and 10.28 min. About 50% of the total amount of hydrogen is dispensed overnight, and the refueling events per bus are typically every 24 h. On average, the buses' time spent in service is 10 h per day. The hydrogen consumption is approximately 7 kg/100 km, a rather effective result reached by the technology. The station utilization is below 30% for all sites, the buses availability hardly exceeds 80%.