Per Alvfors

Real life testing of a Hybrid PEM Fuel Cell Bus

Fuel cells produce low quantities of local emissions, if any, and are therefore one of the most promising alternatives to internal combustion engines as the main power source in future vehicles. It ...

Design of stationary PEFC system configurations to meet heat and power demands

This paper presents heat and power efficiencies of a modeled PEFC system and the methods used to create the system configuration. The paper also includes an example of a simulated fuel cell system supplying a building in Sweden with heat and power. The main method used to create an applicable fuel cell system configuration is pinch technology. This technology is used to evaluate and design a heat exchanger network for a PEFC system working under stationary conditions, in order to find a solution with high heat utilization. The heat exchanger network in the system connecting the reformer, the burner, gas cleaning, hot-water storage and the PEFC stack will affect the heat transferred to the hot-water storage and thereby the heating of the building. The fuel, natural gas, is reformed to a hydrogen-rich gas within a slightly pressurized system. The fuel processor investigated is steam reforming, followed by high- and low-temperature shift reactors and preferential oxidation. The system is connected to the electrical grid for backup and peak demands and to a hot-water storage to meet the varying heat demand for the building. The procedure for designing the fuel cell system installation as co-generation system is described, and the system is simulated for a specific building in Sweden during 1 year. The results show that the fuel cell system in combination with a burner and hot-water storage could supply the building with the required heat without exceeding any of the given limitations. The designed co-generation system will provide the building with most of its power requirements and would further generate income by sale of electricity to the power grid.

Modelling of the sulphation of calcined limestone and dolomite—a gas-solid reaction with structural changes in the presence of inert solids

The partially sintered spheres model is further developed to account for the influence of inert material present in the solid reactant. This model is applicable, for example, to the sulphation of C ...

Modelling of the simultaneous calcination, sintering and sulphation of limestone and dolomite

The partially sintered spheres model, describing the sulphation of a sorbent particle consisting of CaO and inert content, is incorporated in a model taking into account the calcination of the limestone or dolomite and the sintering of the nascent oxide resulting from the calcination. The model is applicable, for example, to the sulphation of limestone or dolomite when injected into the furnace of a pulverized coal-fired boiler. The simulations show a temperature optimum in the calcium conversion. Increased calcium conversion is found when inert material is present. Satisfactory experimental verifications of the model are shown.

Key Factors in Planning a Sustainable Energy Future Including Hydrogen and Fuel Cells

In this article, a number of future energy visions, especially those basing the energy systems on hydrogen, are discussed. Some often missing comparisons between alternatives, from a sustainability perspective, are identified and then performed for energy storage, energy transportation, and energy use in vehicles. It is shown that it is important to be aware of the losses implied by production, packaging, distribution, storage, and end-use of hydrogen when suggesting a “hydrogen economy.” It is also shown that for stationary electric energy storage, fuel cell electrolyzers could be feasible. Zero-tailpipeemission vehicles are compared. The battery electric vehicle has the highest electrical efficiency, but other requirements imply that plug-in hybrids or fuel cell hybrids might be a better option in some types of vehicles. Finally, a simplified example is applied to the overall results and used to discuss the needs and nature of an energy system based on intermittent energy sources.

The Effect of Drive Cycles on the Performance of a PEM Fuel Cell System for Automotive Applications

In this thesis, direct hydrogen Proton Exchange Membrane (PEM) fuel cell systems in vehicles are investigated through modelling, field tests and public acceptance surveys. A computer model of a 50 kW PEM fuel cell system was developed. The fuel cell system efficiency is approximately 50% between 10 and 45% of the rated power. The fuel cell auxiliary system, e.g. compressor and pumps, was shown to clearly affect the overall fuel cell system electrical efficiency. Two hydrogen on-board storage options, compressed and cryogenic hydrogen, were modelled for the above-mentioned system. Results show that the release of compressed gaseous hydrogen needs approximately 1 kW of heat, which can be managed internally with heat from the fuel cell stack. In the case of cryogenic hydrogen, the estimated heat demand of 13 kW requires an extra heat source. A phase change based (PCM) thermal management solution to keep a 50 kW PEM fuel cell stack warm during dormancy in a cold climate (-20 °C) was investigated through simulation and experiments. It was shown that a combination of PCM (salt hydrate or paraffin wax) and vacuum insulation materials was able to keep a fuel cell stack from freezing for about three days. This is a simple and potentially inexpensive solution, although development on issues such as weight, volume and encapsulation materials is needed Two different vehicle platforms, fuel cell vehicles and fuel cell hybrid vehicles, were used to study the fuel consumption and the air, water and heat management of the fuel cell system under varying operating conditions, e.g. duty cycles and ambient conditions. For a compact vehicle, with a 50 kW fuel cell system, the fuel consumption was significantly reduced, ~ 50 %, compared to a gasoline-fuelled vehicle of similar size. A bus with 200 kW fuel cell system was studied and compared to a diesel bus of comparable size. The fuel consumption of the fuel cell bus displayed a reduction of 33-37 %. The performance of a fuel cell hybrid vehicle, i.e. a 50 kW fuel cell system and a 12 Ah power-assist battery pack in series configuration, was studied. The simulation results show that the vehicle fuel consumption increases with 10-19 % when the altitude increases from 0 to 3000 m. As expected, the air compressor with its load-following strategy was found to be the main parasitic power (~ 40 % of the fuel cell system net power output at the altitude of 3000 m). Ambient air temperature and relative humidity affect mostly the fuel cell system heat management but also its water balance. In designing the system, factors such as control strategy, duty cycles and ambient conditions need to taken into account. An evaluation of the performance and maintenance of three fuel cell buses in operation in Stockholm in the demonstration project Clean Urban Transport for Europe (CUTE) was performed. The availability of the buses was high, over 85 % during the summer months and even higher availability during the fall of 2004. Cold climate-caused failures, totalling 9 % of all fuel cell propulsion system failures, did not involve the fuel cell stacks but the auxiliary system. The fuel consumption was however rather high at 7.5 L diesel equivalents/10km (per July 2004). This is thought to be, to some extent, due to the robust but not energy-optimized powertrain of the buses. Hybridization in future design may have beneficial effects on the fuel consumption. Surveys towards hydrogen and fuel cell technology of more than 500 fuel cell bus passengers on route 66 and 23 fuel cell bus drivers in Stockholm were performed. The passengers were in general positive towards fuel cell buses and felt safe with the technology. Newspapers and bus stops were the main sources of information on the fuel cell bus project, but more information was wanted. Safety, punctuality and frequency were rated as the most important factors in the choice of public transportation means. The environment was also rated as an important factor. More than half of the bus passengers were nevertheless unwilling to pay a higher fee for introducing more fuel cell buses in Stockholm’s public transportation. The drivers were positive to the fuel cell bus project, stating that the fuel cell buses were better than diesel buses with respect to pollutant emissions from the exhausts, smell and general passenger comfort. Also, driving experience, acceleration and general comfort for the driver were reported to be better than or similar to those of a conventional bus.

Obstacle 1 : Capturing the experiences of Swedish electric vehicle users

The Swedish National Procurement of Electric Vehicles and Plug-in Hybrids scheme is a technology procurement project aimed at facilitating a market introduction and market expansion in Sweden. The paper describes the development of the data collection method over the course of the project, with the aim of contributing to more efficient evaluations of demonstration fleets of electric vehicles. Combining multiple sources of data may enable a socio-technical understanding of electric vehicle operations. The methods used for data collection in the project are vehicle logbooks, GPS equipment, questionnaires and interviews. Focus groups have been carried out to validate the socio-technical findings. The paper will describe the method development process and the lessons learned are divided into three categories: avoiding misunderstandings, time-saving measures and increasing engagement.