The Application of Fuel-Cell and Battery Technologies in Unmanned Aerial Vehicles (UAVs): A Dynamic Study

The harmful impacts of fossil-fuel-based engines on the environment have resulted in the development of other alternatives for different types of vehicles. Currently, batteries and fuel cells are being used in the automotive industry, while promising progress in the maritime and aerospace sectors is foreseen. As a case study in the aerospace sector, an unmanned aerial vehicle (UAV) was considered. The goal and the novelty of this study are in its analysis of the possibility of providing 960 W of power for a UAV with a weight of 14 kg using a hybrid system of a lithium-ion (Li-ion) battery and proton-exchange membrane fuel cell (PEMFC). The dynamic performance of the system was analyzed considering three different load profiles over time in an optimized condition. PEMFC was the main supplier of power, while the battery intervened when the power load was high for the PEMFC and the system demanded an immediate response to the changes in power load. Additionally, the impacts of the operating temperature and the C-rate of the battery were characterized by the state of the charge of the battery to better indicate the overall performance of the system.

Optimization and dynamic responses of an integrated fuel cell and battery system for an 800 kW ferry: A case study

Martin Daniel Gay, Hossein Pourrahmani, Jan Van Herle

The recent targets by different countries to stop the sales or registrations of internal combustion engines (ICE) have led to the further development of battery and fuel cell technologies to provide power for different applications. The main aim of this study is to evaluate the possibility of using an integrated Lithium-Ion battery and proton exchange membrane fuel cell (PEMFC) as the prime mover for a case study of a 800 kW ferry with a total length of 50.8 m to transport 780 passengers for a distance of 24 km in 70 min. Accounting for five types of Lithium-Ion batteries and different numbers of PEMFCs, twenty-five scenarios are suggested based on a quasi-static model. To perform the optimization, the Performance Criterion of the Fuel cell-Battery integrated systems (PCFB) is introduced to include the effects of the sizes, weights, costs, hydrogen consumption, efficiency, and power in addition to the number of fuel cells and the battery capacity. Results indicate that the maximum PCFB value of 10.755 (1/kg(2)m(3)

) can be obtained once the overall size, weight, efficiency, hydrogen consumption, and cost of the system are 18 m(3), 11160 kg, 49.25%, 33.6 kg, and 119.58 k

ELSEVIER2022

Aqueous electrolytes for high-voltage batteries and supercapacitors

David Reber

Lithium-ion batteries are widely implemented as energy storage devices due to their high energy density and low cost. They enabled modern portable electronics and electric ve-hicles, and are key to manage the integration of intermittent renewable electricity sources, such as solar and wind, into the power grid and decentralized microgrids. The use of flam-mable organic electrolytes however raises safety concerns, particularly for large-scale sta-tionary batteries. Furthermore, supply chain risks and the use of critical raw materials are a major challenge for the ongoing battery revolution. Aqueous electrolytes offer promising properties, as they are inherently non-flammable and potentially more cost effective. Combined with electrode materials based on abundant raw materials, aqueous batteries are among the most promising candidates to replace cur-rent battery chemistries relying on critical cobalt and flammable organic electrolytes. How-ever, due to the narrow electrochemical stability window of water (practically ca. 1.5 V), aqueous batteries have not yet met the energy density to be serious competitors to current lithium-ion battery technology. The goal of this thesis was to develop aqueous electrolytes with enhanced electrochem-ical stability, thus enabling new high-voltage cell chemistries. Exploring aqueous electrolytes with high salt concentrations, so-called water-in-salt electrolytes, we significantly increased the electrochemical stability and developed highly stable 2 V class aqueous sodium-ion bat-teries. Operating near the solubility limit of the electrolyte salt, crystallization turned out to be a major challenge for water-in-salt electrolytes. In this thesis, we demonstrated that add-ing highly asymmetric anions into the solution can effectively suppress crystallization, allow-ing stable operation of saturated electrolytes at temperatures as low as -10 °C. We further examined the impact of anion asymmetry on the local solution structure and dynamics using molecular dynamics simulations, relating the enhanced supercooling to sustained rotational motion of the asymmetric anion. Further, we demonstrate that the anion has a crucial impact on solution structure and cell performance. We establish that high salt concentration alone does not guarantee high-voltage stability and that due to the limited solubility of most sodium salts new approaches are needed. We provide guidelines for future work and the evaluation of experimental data in order to spur progress in the field of aqueous batteries.

EPFL2020