Performance analysis of a micro CHP system based on high temperature PEM fuel cells subjected to degradation

Micro Combined Heat and Power (microCHP) systems based on High Temperature Polymer Electrolyte Membrane (HTPEM) fuel cells is a promising technology allowing to produce electricity and heat with very high efficiency and low emissions also for small power systems. Polybenzimidazole (PBI) based HTPEM fuel cells, thanks to their high CO tolerance, allow the use of fuels other than pure hydrogen by means of a simplified fuel processing unit. However, their relatively low performance and performance degradation rate are still issues to be overcome in order to allow commercialization. In this work, an energy simulation model developed by the authors in a previous research work, has been improved taking into account the degradation of the fuel cell stack in order to assess the performance of the system over long period of operation. The fuel cells performance degradation over time has been implemented on the basis of experimental data obtained by the authors and on data found in literature. The performance of the system has been studied in different configurations that include the introduction of a lithium battery storage in addition to the fuel cell stack. System parameters, such as electrical and thermal energy production, import/export of electricity and primary energy savings have been calculated and compared for different system configurations. Results show that battery integration can improve system performance and that the effect of fuel cell degradation reduces the electricity production. The effect on overall efficiency can be mitigated if heat is recovered

Estimation of a Noise Level Using Coarse-Grained Entropy of Experimental Time Series of Internal Pressure in a Combustion Engine

We report our results on non-periodic experimental time series of pressure in a single cylinder spark ignition engine. The experiments were performed for different levels of loading. We estimate the noise level in internal pressure calculating the coarse-grained entropy from variations of maximal pressures in successive cycles. The results show that the dynamics of the combustion is a nonlinear multidimensional process mediated by noise. Our results show that so defined level of noise in internal pressure is not monotonous function of loading.Comment: 12 pages, 6 figure

High energy density storage of gaseous marine fuels: An innovative concept and its application to a hydrogen powered ferry

The upcoming stricter limitations on both pollutant and greenhouse gases emissions represent a challenge for the shipping sector. The entire ship design process requires an approach to innovation, with a particular focus on both the fuel choice and the power generation system. Among the possible alternatives, natural gas and hydrogen based propulsion systems seem to be promising in the medium and long term. Nonetheless, natural gas and hydrogen storage still represents a problem in terms of cargo volume reduction. This paper focuses on the storage issue, considering compressed gases, and presents an innovative solution, which has been developed in the European project GASVESSEL\uae that allows to store gaseous fuels with an energy density higher than conventional intermediate pressure containment systems. After a general overview of natural gas and hydrogen as fuels for shipping, a case study of a small Roll-on/Roll-off passenger ferry retrofit is proposed. The study analyses the technical feasibility of the installation of a hybrid power system with batteries and polymer electrolyte membrane fuel cells, fuelled by hydrogen. In particular, a process simulation model has been implemented to assess the quantity of hydrogen that can be stored on board, taking into account boundary conditions such as filling time, on shore storage capacity and cylinder wall temperature. The simulation results show that, if the fuel cells system is run continuously at steady state, to cover the energy need for one day of operation 140 kg of hydrogen are required. Using the innovative pressure cylinder at a storage pressure of 300 bar the volume required by the storage system, assessed on the basis of the containment system outer dimensions, is resulted to be 15.2 m3 with a weight of 2.5 ton. Even if the innovative type of pressure cylinder allows to reach an energy density higher than conventional intermediate pressure cylinders, the volume necessary to store a quantity of energy typical for the shipping sector is many times higher than that required by conventional fuels today used. The analysis points out, as expected, that the filling process is critical to maximize the stored hydrogen mass and that it is critical to measure the temperature of the cylinder walls in order not to exceed the material limits. Nevertheless, for specific application such as the one considered in the paper, the introduction of gaseous hydrogen as fuel, can be considered for implementing zero local emission propulsion system in the medium term

The role of hydrogen as enabler of industrial port area decarbonization

To meet environmental goals while maintaining economic competitiveness, worldwide ports have increased the amount of renewable energy production and have focused in optimizing performances and energy efficiency. However, carbon-neutral operation of industrial port areas (IPA) is challenging and requires the decarbonization of industrial processes and heavy transport systems. This study proposes a comprehensive review of decarbonization strategies for IPA, with a particular focus on the role that green hydrogen could play when used as renewable energy carrier. Much information on existing and future technologies was also derived from the analysis of 74 projects (existing and planned) in 36 IPAs, 80 % of which are in Europe, concerning hydrogen-based decarbonization strategies. The overall review shows that engine operation of ships at berth are responsible of more than 70 % of emissions in ports. Therefore, onshore power supply (OPS) seems to be one of the main strategies to reduce port pollution. Nevertheless, OPS powered by hydrogen is not today easily achievable. By overcoming the current cost-related and regulation barriers, hydrogen can also be used for the import/export of green energy and the decarbonization of hard-to-abate sectors. The technical and economic data regarding hydrogen-based technologies and strategies highlighted in this paper are useful for further research in the field of definition and development of decarbonization strategies in the IPA

Thermodynamic analysis of a Carbon Carrier Cycle (CCC) for low temperature heat recovery

The aim of the paper is to study the thermodynamic behavior of a non-conventional power cycle, named Carbon Carrier Cycle (CCC), which is expected to obtain interesting performance with low temperature heat source. The CCC may be regarded as derived from an absorption machine, where an expander replaces the condenser, the throttling valve and the evaporator. The working fluid is a mixture of CO2 and a proper absorber. In the paper, the thermodynamic model of this kind of cycles is described, and the results obtained considering Acetone as the absorber are discussed. A first performance comparison is then conducted with a more conventional Organic Rankine Cycle (ORC)

Effects of control strategies on the performance of a PEM fuel cell module

A FC stack performance depends on the behavior of each single cell. Non uniformity in the voltage of the cells can be caused by components/manufacturing problems or operating problems such as a non adequate reactants distribution, water flooding or dehydration. To analyze the effect of different control strategies on cell voltage non uniformity at the Mechanical Engineering Department of the University of Trieste a test rig has been developed. The stack currently analyzed is a 47 PEM cell stack manufactured by Ballard. The uniformity analysis has been performed at different loads investigating the effect of different control strategies regarding anode purge and cathode air flow rate

Utilization of Biodiesel in modern Diesel engines: effects on performance and emissions

Biodiesel is receiving growing attention as an alternative fuel for diesel engines. Although its use is already widespread some aspects of its influence on engine performance and emissions are not yet exhaustively analyzed especially in the case of modern diesel engines. The paper presents the results of a research activity carried out on a IVECO Cursor 8 EURO 3 heavy duty engine and a FIAT 1.3 \u2113Multijet. The Cursor 8 was mounted in an IVECO City Class bus in service in Pordenone \u2013 Italy. In this case the tests have been aimed at studying in particular the influence of Biodiesel on the NOx and on the particulate matter emissions and experiments were carried out both in on road and free acceleration conditions. The FIAT Multijet was analyzed on the Department test facility and the experiments examine various steady state load and speed conditions. The resultsshow that in all cases the opacity with Biodiesel is reduced while the trends in the NOx emissions strictly depend on the load condition and the type of the engine. The particulate distribution analysis shows that Biodiesel contributes to the reduction of the total number of particles emitted

Simulink-Femlab integrated dynamic simulation model for a PEM fuel cell system

The present work proposes a model which integrates the finite element method in a dynamic simulation, in order to achieve a higher accuracy and the possibility to investigate the influence of various parameters on the fuel cell system dynamics. The model takes also in consideration the system auxiliaries representing a flexible platform with the capability to predict the PEMFC system dynamics and to provide important information for the design of control strategies