Escuela Superior de Enseñanzas Técnicas

When fuel cells are used to power mobile applications, such a vehicles, hybridization with batteries is normally required. Depending on the electronic coupling between the energy sources the power plants can have passive or active configurations. Hybrid fuel cell-battery power plants with active power control flow have some advantages. For example, they can decrease the total energy losses, while improving the fuel cell performance, extending its lifetime. Power plants with DC/DC converters show low specific energy ratios, but with a superior energy management. In the present research, the hybrid power plant for an unmanned aquatic surface vehicle (USV) based on a PEM fuel cell and a Li-ion battery is developed. Active (with DC–DC converters) or passive architectures are analyzed by numerical simulations and experimental tests. Good results are obtained for the active power plant, where the peak power demands are managed by the battery pack while the fuel cell power remains constant thanks to the DC-converter control. The study shows that a simple control algorithm (no optimal) can help to extend the USV autonomy above 12 h in calm waters with a specific energy of 85.6 W h kg-1.

Leading edge protection (LEP) coating systems are applied to protect turbine blade edges from rain erosion. The performance of a LEP system is assessed in an accelerated rain erosion test (RET) as a metric for industrial application, but these tests are expensive. Modelling methods are available to predict erosion, based on fundamental material properties, but there is a lack of validation. The Springer model (1976) is analysed in this work to assess it as a tool for using material fundamental properties to predict the time to failure in a rain erosion test. It has been applied, referenced and industry validated with important partial considerations. The method has been applied successfully for erosion damage by wear performance prediction when combined with prior material data from rain erosion test (RET), instead of obtaining it directly from fundamental properties measured separately as Springer proposed. The method also offers accurate predictions when coupled with modified numerical parameters obtained from experimental RET testing data. This research aims to understand the differences between the experimental data used by Springer and the current industry approach to rain erosion testing, and to determine how it may introduce inaccuracies into lifetime predictions of current LEP systems, since they are very different to those tested in the historic modelling validation. In this work, a review of the modelling is presented, allowing for the understanding of key issues of its computational implementation and the required experimental material characterisation. Modelling results are discussed for different original application issues and industry-related LEP configuration cases, offering the reader to interpret the limits of the performance prediction when considering the variation in material fundamental properties involved.

Achieving European climate neutrality by 2050 requires further efforts not only from the industry and society, but also from policymakers. The use of high-efficiency cogeneration facilities will help to reduce both primary energy consumption and CO2 emissions because of the increase in overall efficiency. Fuel cell-based cogeneration technologies are relevant solutions to these points for small- and microscale units. In this research, an innovative and new fuel cell-based cogeneration plant is studied, and its performance is compared with other cogeneration technologies to evaluate the potential reduction degree in energy consumption and CO2 emissions. Four energy consumption profile datasets have been generated from real consumption data of different dwellings located in the Mediterranean coast of Spain to perform numerical simulations in different energy scenarios according to the fuel used in the cogeneration. Results show that the fuel cell-based cogeneration systems reduce primary energy consumption and CO2 emissions in buildings, to a degree that depends on the heat-to-power ratio of the consumer. Primary energy consumption varies from 40% to 90% of the original primary energy consumption, when hydrogen is produced from natural gas reforming process, and from 5% to 40% of the original primary energy consumption if the cogeneration is fueled with hydrogen obtained from renewable energy sources. Similar reduction degrees are achieved in CO2 emissions.

Top coating are usually moulded, painted or sprayed onto the wind blade Leading-Edge surface to prevent rain erosion due to transverse repeated droplet impacts. Wear fatigue failure analysis based on Springer model has been widely referenced and validated to quantitatively predict damage initiation. The model requires liquid, coating and substrate speed of sound measurements as constant input parameters to define analytically the shockwave progression due to their relative vibro-acoustic properties. The modelling assumes a pure elastic material behavior during the impact event. Recent coating technologies applied to prevent erosion are based on viscoelastic materials and develop high-rate transient pressure build-up and a subsequent relaxation in a range of strain rates. In order to analyze the erosion performance by using Springer model, appropriate impedance characterization for such viscoelastic materials is then required and represents the main objective of this work to avoid lack of accuracy. In the first part of this research, it is proposed a modelling methodology that allows one to evaluate the frequency dependent strain-stress behavior of the multilayer coating system under single droplet impingement. The computational tool ponders the operational conditions (impact velocity, droplet size, layer thickness, etc.) with the appropriate variable working frequency range for the speed of sound measurements. The second part of this research defines in a complementary paper, the ultrasonic testing characterization of di erent viscoelastic coatings and the methodology validation. The modelling framework is then used to identify suitable coating and substrate combinations due to their acoustic matching optimization and to analyze the anti-erosion performance of the coating protection system.