102 research outputs found
Fuel cells for airborne usage: Energy storage comparison
No full textThe global drone market is growing every year. The number of applications is increasing: from search and rescue, security, surveillance to science and research and unmanned cargo systems.
A limiting factor for drone exploitation is that for the energy storage, normally, a battery is used and this solution affects flight time. A possible solution could be the utilization of fuel cells. This paper focuses on the utilization of fuel cells power as an alternative solution for drone propulsion.
The aim of the study is to determine when it is more appropriate, in terms of mass, to use a battery or a hybrid (fuel cell þ battery) system to power drones. To compare the different systems, a numerical simulation model has been developed in order to choose the best power system once the drone operation profile has been defined.
The model allows comparing different type of fuels and battery systems. The data to tune the model have been taken from commercial products, today already available. The simulation model considers a light-weight open-air cathode PEM (Polymer Exchange Membrane) fuel cell. The stack power output is chosen according to the mission profile and rages from 200 W to 1000 W.
The presented results show that, for the considered drone segment, multi-rotor drones with weight of 7 kg at take-off, lithium batteries are still the best choice for time flight shorter than about 1 h. A hybrid system, appears to be interesting for longer flights. For example, it has been calculated that a hybrid quadcopter drone with a mass of 7 kg, considering a flight profile that requires 1089 Wh can be powered with a 4.4 kg hybrid system composed by a 500 W and 1.4 kg PEM fuel cell system, 1.9 kg hydrogen composite pressure vessel and a 0.8 kg lithium battery. The same amount of energy can be stored in a lithium battery with a weight of about 6.6 kg. These means a weight saving of more than 30%. The hybrid system, in term of weight, is even more convenient for flight profiles that require more energy
Effect of accelerated ageing tests on PBI HTPEM fuel cells performance degradation
No full textThe study presented in this paper aims to evaluate the performance degradation of Polybenzimidazole (PBI) based High Temperature PEM (HTPEM) fuel cells subjected to different ageing tests, according to a methodology already used by the authors. Three HTPEM Membrane Electrode Assemblies (MEAs) were characterized before and after different aging tests and performance compared. The three MEAs have been named MEA C, MEA D and MEA E. MEA C was subjected to 100,000 triangular sweep cycles between Open Circuit Voltage (OCV) and 0.5 A/cm2 with 2 s of permanence at OCV at each cycle. MEA D and MEA E were subjected to 440 h of operation at constant load of 0.22 A/cm2. In order to assess the cell performance, polarization curves, Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV) were recorded during the ageing tests. Degradation rates have been obtained for MEA C (44 μV/h), for MEA D (30 μV/h) and for MEA E (29 μV/h). ECSA (Electrochemical Surface Area) has been calculated for the three MEAs showing a reduction of approximately 50% for MEA C and of approximately 30% for MEA D and MEA E. Polarization curves during aging tests confirm that load cycling is more detrimental. A comparison with data obtained by the authors in a previous research seems to confirm the repeatability of the test protocol used
Comparison of different plant layouts and fuel storage solutions for fuel cells utilization on a small ferry
No full textIn the path towards the decarbonization of the maritime sector, Low Temperature Polymer Electrolyte Membrane Fuel Cells (LT-PEMFC) fed by hydrogen are gaining attention as they could guarantee zero local emissions propulsion. In this study, a process simulation model is implemented to analyze the influence of peak shaving in a hybrid LT-PEMFC/lithium-ion battery power plant for the propulsion of a small size RoRo car and passenger ferry in different operative conditions. Results show that battery peak shaving could allow a reduction of FC installed power of up to 72%. As for compressed H2 storage, the results show that for sailing time in the range of 5–10 min, Type I cylinders at 250 bar are a viable option. For longer routes, Type III cylinders at 350 bar or Type IV cylinders at 700 bar should be considered in order to avoid excessive reduction in the pay-load
Multi-objective optimization of hybrid PEMFC/Li-ion battery propulsion systems for small and medium size ferries
No full textHybrid Polymer Electrolyte Membrane Fuel Cells/Lithium-ion battery powertrains are a promising solution for zero-local-emissions marine propulsion. The present study aims to optimize the design and operation of such hybrid powertrain for small-size passenger ferries, taking into account the performance degradation of both fuel cells and batteries. A Mixed-Integer Linear-Programming approach and a hierarchical method are adopted to concurrently minimize the fuel cells degradation, the capital expenditure and the operating expenditure, while constraints are included in the model to limit the battery degradation. The results show that the proposed multi-objective optimization can lead to a reduction of fuel cells degradation by up to 65% compared to a cost-minimization only. However, this can imply an increase in the battery capacity by up to 136%. The proposed method has general validity, and it is a useful tool for both preliminary design and choice of the optimal energy management strategy for ships energy systems
Application of biomass fed ORC power systems in the furniture manufacturing industrial district of Pordenone: Part II° - development of thermodynamic cycle simulation model
No full textSimulink-Femlab Integrated Dynamic Simulation Model for a PEM Fuel Cell System
No full textThe necessity for reliable simulation models, able to support the fuel cell systems development activity, has increased continuously during the last years. The present work proposes a model which integrates the finite element method in a dynamic simulation, in order to achieve higher accuracy and the possibility to investigate the influence of various parameters on the fuel cell dynamics. The model is implemented using Matlab/Simulink and consists of two interacting main subsystems that calculates the fuel cell power response and the stack thermal behavior. The first simulates the mass transport and electrochemical phenomena using a model implemented in Femlab, and considers as input parameters the stack geometry, reactants pressure, flow rate and composition and the stack average temperature. The last parameter is also evaluated by the second model, implemented also in Femlab, which considers the stack geometry, cooling air flow rate and ambient temperature. Both models were validated using the experimental data acquired on a Ballard Nexa 1.5 kWe PEM system. The results prove that integrated model simulates with accuracy the dynamics of the PEMFC system and the interaction between the stack and the auxiliaries. The proposed model was used as a predictive tool for two situations. In the first simulation, with a relative fast dynamic, the model demonstrates that the cooling fan control strategy is essential for transient conditions characterized by a significant load decreasing. In the second, the model estimates the variation of the PEMFC main parameters on a 24 hour cycle, confirming its reliability
Utility-based exergetic cost algorithms for managing cogeneration powered systems
No full textCosting of products based on exergy rather than energy is adjudged rational because it is a commodity of value and provides for accurate prices of products. In this paper, using an absorption chiller system as an example, a set of algorithms is presented that determines specific unit costs of internal flows and products at each component. The absorption chiller has different components that are broadly classified as productive and dissipative types. The methodology of second law of thermodynamics is used to define the productive components as well as for measuring their performance and the formulation of objective function for the determination of unit cost of the desired products. A utility-based exergetic evaluation technique is preferred because it offers the possibility of identifying and quantifying irreversibility as well as assigning available useful exergy among the productive components. Results from the study indicate that total purchase costs of productive components are as follows: €209.1/kW; €4.617/kW; €0.1619/kW; and €3.542/kW for generator, solution heat exchanger, pump and evaporator assembly, respectively. With these parameters, the various unit costs were calculated. It is hoped that information obtained here would be helpful in managing Independent Power Production plants through effective product pricing
A review of emissions reduction technologies for low and medium speed marine Diesel engines and their potential for waste heat recovery
No full textReducing emissions from internal combustion engines is becoming one of the most important tasks for engine manufactures and transport regulatory organizations. In particular, the marine transportation sector is one of the most polluting, due to the intense maritime activity and the use of low-quality fuels, burned in Heavy Duty Diesel Engines, for ship propulsion and auxiliary power generation. In order to reduce the global shipping environmental impact, the IMO (International Maritime Organization) is restricting NOx and SOx ships’ emissions through the introduction of the IMO Tier III legislation, which requires to consider a wide spectrum of emissions reduction technologies and strategies, which are going to have an impact on the engine performance and fuel consumption. In this work, the main solutions being currently developed or adopted for low and medium speed Diesel engines have been reviewed from a qualitative, and sometimes quantitative, point of view, but, in comparison to previous literature, focusing more on their potential with respect to possible waste heat recovery systems utilization, such as, in particular, steam Rankine cycles and Organic Rankine Cycles (ORC). Indeed, even though many of the considered emissions mitigation technologies lead to a certain amount of penalty in fuel economy, the use of waste heat recovery systems to recover wasted engines energy could become interesting in order to develop more efficient but, at the same time, cleaner engines
Uncertainty analysis of the optimal health-conscious operation of a hybrid PEMFC coastal ferry
No full textHydrogen fueled Polymer Electrolyte Membrane Fuel Cells/Lithium-Ion Battery powertrains could be a promising solution for zero-local-emission shipping. The power allocation between PEMFC and LIB and their respective performance degradation play a crucial role in reducing the powertrain operating and maintenance costs. While several research works proposed energy management strategies to face these issues, a long-term operation optimization including the uncertainty in the input parameters of the model has not been extensively addressed. To this purpose, this study couples an operation optimization model of a PEMFC/LIB ferry propulsion system with a Monte-Carlo analysis to investigate the influence of PEMFC, LIB and hydrogen costs on the optimal operation of a hydrogen-powered ferry in the long-term. Hydrogen cost results to be the most influent parameter, in particular toward the end of the plant lifetime, when hydrogen consumption increases by up to 30%. Nevertheless, the variability of optimal ferry operation gradually decreases with the progressive PEMFC/LIB degradation
Multiple Expansion ORC for Small Scale – Low Temperature Heat Recovery
No full textORCs are widely recognized as one of the most suitable solution for energy recovery, if the temperature of the heat source is of about 200°C, or lower. In case of heat sources of about 100 kW or smaller, the more common solutions prescribe a simple cycle and a single stage expander, in order to reduce complexity and costs. Scroll expanders, derived from scroll compressors, are expected to be available at very low unit costs. The drawbacks of this kind of solutions, originally designed for automotive, or HVAC applications, are mainly two: the low fixed volumetric expansion ratio and the small volumetric flow rate, that are not always well-suited for the requirements of power production. In this paper, different ORCs with multiple expansions are evaluated with the aim of achieving a better exploitation of small scale-low temperature waste heat sources. The comparison takes in consideration different possible solutions for the multiple expansions, with internally recuperated and not-recuperated cycles, whilst the data describing the actual behaviour of compressors derived scroll expanders have been previously obtained by a test rig, set up at the University of Trieste, using R245fa as working fluid
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