• Energy Research

Abstract Among the possible electric powerplants currently driving low-payload UAVs (up to around 10 kg of payload), batteries offer certain clear benefits, but for medium-payload operation such as aerotaxis and heavy-cargo transportation UAVs, battery capacity requirements restrict their usage due to high weight and volume. In light of this situation, fuel cell (FC) systems (FCS) offer clear benefits over batteries for the medium-payload UAV segment (> 50 kg). Nevertheless, studies regarding the application of FCS powerplants to this UAV segment are limited and the in-flight performance has not been clearly analysed. In order to address this knowledge gap, a feasibility analysis of these particular applications powered by FCS is performed in this study. A validated FC stack model (40 kW of maximum power) was integrated into a balance of plant to conform an FCS. As a novelty, the management of the FCS was optimized to maximize the FCS efficiency at different altitudes up to 12500 ft, so that the operation always implies the lowest H2 consumption regardless of the altitude. In parallel, an UAV numerical model was developed based on the ATLANTE vehicle and characterized by calculating the aerodynamic coefficients through CFD simulations. Then, both models were integrated into a 0D-1D modelling platform together with an energy management strategy optimizer algorithm and a suitable propeller model. With the preliminary results obtained from the FCS and UAV models, it was possible to ascertain the range and endurance of the vehicle. As a result, it was concluded that the combination of both technologies could offer a range over 600 km and an endurance over 5 h. Finally, with the integrated UAV-FCS model, a flight profile describing a medium altitude, medium endurance mission was designed and used to analyse the viability of FC-powered UAV. The results showed how UAVs powered by FCS are viable for the considered aircraft segment, providing competitive values of specific range and endurance.

[EN] With the rise of cleaner technologies for transport and the emergence of H-2 as a fuel, most of the emissions in the well-to-wheel process are shifting towards the energy carrier production (fuel or electricity). The objective of this study is to perform a simplified cradle-to-grave Life Cycle Assessment (LCA) that compares the greenhouse gases (GHG) and NOX emissions of H-2, electric and conventional technologies for the automotive sector in Europe and to devise the optimum strategy of vehicle fleet renewal to reduce the emissions. In this study the effect of water as GHG was considered and, unless other studies, the current European energy mix and that meeting the objectives for 2050 were considered (while technology level was kept constant) since H-2 from electrolysis and electric vehicles' well-to-wheel emissions are sensitive to the energy mix. To estimate the emissions, the fuel, vehicle production and operation cycles were considered independently for each technology and then put together. For H-2, the best production and distribution strategy was steam methane reforming (SMR) with CO2 sequestration for GHG-100 gases and without capturing CO2 for NOX, both with central plant production and tube trailer transport. Fuel cell vehicles (FCV) with optimum H-2 production always produce the lowest GHG-100 emissions and slightly higher NOX than battery electric vehicles (BEV) in the EU 2050 scenario. In contrast, HICEV would need to reach a fuel consumption of around 30 kWh/100 km to be competitive in emissions against BEV, for that, direct injection (DI) combined with a range extender (REx) hybrid architecture is the recommended powerplant concept. Finally, the optimum strategy to reduce emissions that Europe could follow is presented for the short, mid and long term. This research has been partially funded by FEDER and the Spanish Government through project RTI2018-102025-B-I00 (CLEAN-FUEL).

[EN] As the world intensifies its efforts to reduce the adverse effects of global warming, the shift towards a fully developed hydrogen-based economy is emerging as a core strategy. This transition involves the strategic blending of hydrogen with conventional fossil fuels such as natural gas (HCNG), allowing for adaptation to hydrogen availability. Nevertheless, the environmental impact of HCNG vehicles in realistic scenarios with variable hydrogen content remains unexplored. This study focuses on evaluating the global warming impact of the transition of light-duty passenger cars from CNG to H2 vehicles using HCNG blends from 2020 to 2050 and different realistic scenarios. The results in the present study were obtained through a combination of an experimental testing campaign that allowed obtaining how the performance and emissions of HCNG vehicles change with the H2 content and a life cycle assessment methodology. Based on the findings, the scenario in which hydrogen was mostly produced from SMR-dominant, was found to have the potential to reach and outperform the zero-emission concept due to the utilization of biogas. From the results of this study, the recommended H2 content in HCNG blends that offers low environmental impact while avoiding the overdemand of hydrogen in the short term for the 2020-2030 decade is 25% H2 content, increasing to 50% by 2030, and to 75%-100% during the 2040-2050 decade, thus reaching the transition towards pure-H2 technology that minimizes environmental impact. This research has been partially funded by FEDER and the Spanish Government through project RTI2018-102025-B-I00 (CLEAN-FUEL) . M. Olcina-Girona is partly supported by the grant CIACIF/2021/437 of the "Subvenciones para la contratacion de personal investigador pre-doctoral (ACIF) "of the Conselleria d'Innovacio, Universitats, Ciencia i Societat Digital de la Generalitat Valenciana, Spain.

[EN] The current trend towards a zero-emission transport sector has increased the interest of the scientific community and the industry in fuel cell (FC) technologies in the past few years. Previous studies have focused on passenger car analyses to differentiate them from the current battery electric vehicle (BEV) alternative. However, deploying these technologies may be even more critical for the transportation-produced global emissions if they are used in different applications, such as heavy-duty commercial vehicles. This study uses a differential control strategy to find the best fuel-cell performance for a heavy-duty vehicle application. In addition, and as a differentiation point from other studies in the literature, this article exploits the modularity of the heavy-duty truck sector to implement a design with optimal fuel cell system (FCS) sizing and control dynamics distribution in terms of durability and H2 consumption. Low dynamics could increase 471% in durability just for a 3.8% increase in H2 consumption. When using a multi-FCS with non-equal power FCS, a high dynamics behavior of the small FCS significantly improves the durability for a small consumption penalty (less than 0.7%). The obtained data has proven that the combination of these two design strategies shows an improved vehicle performance that could lead to environmental impact and cost reduction, which is significant in the current development stage of fuel cell vehicle (FCV) technologies. This research has been partially funded by the Spanish Ministry of Science, Innovation, and University through the University Faculty Training (FPU) program (FPU19/00550) and by the Generalitat Valenciana (Conselleria d'Innovacio, Universitats, Ciencia i Societat Digital) as a part of the DEFIANCE research project (CIPROM/2021/039) through the PROMETEO funding program.

[EN] Aiming to reduce global warming and emissions in general, cleaner technologies are the spotlight of research and industry development. Among them, fuel cell vehicles (FCV) are gaining interest to decarbonize the transport sector. Plug-in FCV or FCV in range-extender configuration (FCREx) is an interesting option to reduce the total cost of ownership (TCO) and the energy usage per km. The aim of this study was to generate design spaces of FCREx by varying the FC stack maximum power output, the battery capacity, and the H-2 tank capacity to understand the implications of this architecture in range, consumption, and cost (estimated with a WLTP driving cycle). Unlike other studies, the approach was focused on a novel architecture for passenger vehicles and was focused on the development of the validated FC system model and the energy management strategy (EMS) optimization for each design, based on the Pontryagin Minimum Principle (PMP). Consumption was found to decrease with increasing battery capacity and FC maximum power due to the higher efficiency of the systems. The design spaces showed how with 5 kg of H-2 and >= 50 kWh of battery capacity the maximum range of FCREx could be over 700 km. The results of this study showed how FCREx architecture could provide overall energy consumption saving up to 6.8% and H-2 consumption saving ranging from 16.8% to 25%, compared to current commercial FCVs. The optimum FCREx design, not only based on performance, should have similar to 30 kWh of battery capacity and >= 80 kW of FC maximum power to minimize manufacturing costs while maximizing efficiency. This research has been partially funded by FEDER, Spain and the Spanish Government through project RTI2018-102025-B-I00 (CLEANFUEL) and through the University Faculty Training (FPU) program