Analysis of the performance of a passive hybrid powerplant to power a lightweight unmanned aerial vehicle for a high altitude mission

Abstract

The objective of this research is to analyze the performance of a passive hybrid powerplant control system to be implemented in a lightweight unmanned aerial vehicle capable to ascend up to the high troposphere (10,000 m). The powerplant is based on a high-temperature PEM fuel cell connected in parallel to a set of lithium-polymer batteries and regulated by two power diodes. Test performed in steady state demonstrates that the use of the hybrid system increases the efficiency of the stack by more than 7% because the voltage at the main DC bus is limited by the batteries. The robustness of the passive control system is proved in a longterm test in which random perturbations of ±15% are applied to the average power that would be demanded during the ascent flight. The hybridization of the stack with the batteries eliminates sudden peaks in the current generated by the stack, which are responsible for prompt degradation phenomena that drastically reduce its useful lifetime. The study demonstrates that with the passive hybrid powerplant it is possible to reach the target height with the gas storage system considered in the application, contrary to what happens with the simple power plant.

Hybrid Propulsion Systems for Remotely Piloted Aircraft Systems

“…Hybrid systems may in fact hold the key in larger drone scales. [88] Increase the endurance by 300% - [89] Increase the efficiency by 3% - [67] Increased in stack efficiency of a fuel cell by 7% PV hybrid - [34] Up to 20% of the daily input can be fed through PV - [26] Fuel cell-PV (470 to 890 min for baseline conditions) i.e., is up to 90%…”

“…This allows the fuel-cell system to help achieve better fuel economy and performance while part of the load is powered from the batteries or super capacitors [66]. Such combination systems have shown improvement; for example, a Li-Po battery combination with a fuel cell shows an improvement in battery stack by over 7% relative to the fuel-cell-only system [67]. Other research shows a flying time increase from 470 to 970 min [26].…”

“…This hybrid system is mostly used by integrating a battery into the stack system to improve endurance. An example of this has shown an increase in stack efficiency of the hybrid by 7% [67]. Another example [69] has shown that a passive hybrid system could improve the efficiency of the fuel-cell system over 50%.…”

Renewable Energy for Robots and Robots for Renewable Energy – A Review

“…225 The solution is to combine different power sources that can be connected either in serial, parallel, or serial-parallel in a hybrid configuration. 220 The main benefits of hybrid power systems with fuel cells compared with pure battery power systems are achieving a higher specific energy and energy density, providing redundancy in power supply, reducing the possibility of failure, improving energy efficiency, 226 and achieving higher endurance. 221 Hybrid power systems are classified as: (1) active, with control elements and (2) passive, with a direct coupling among the system components.…”

“…A test performed to study the dynamic behavior of the p-HPP demonstrated that the presence of LiPo batteries in this configuration smooths out the sharp peaks of the current curve of the HT-PEMFC, reducing the degradation phenomena that they can induce. 220 In ref. [221], a series of tests were performed on the AeroStack hybrid, fuel-cell-based power train.…”