A Strategy for Sizing and Optimizing the Energy System on Long-Range AUVs

Ariel Chiche,Carina Lagergren,Ivan Stenius,Goran Lindbergh

doi:10.1109/joe.2021.3062047

Abstract

Autonomous underwater vehicles (AUVs) are utilized in a variety of unmanned missions, such as environmental surveys or guarding coastal waters. Currently, the most commonly used energy storage is a secondary battery pack. A potential solution for increasing the range even further on larger AUVs is to utilize hybrid fuel cell/battery systems. Fuel cell systems can have a significantly increased specific energy compared to batteries and are now starting to become well-developed technologies. However, in an underwater environment, both hydrogen and oxygen need to be stored for the fuel cell. This study considers the sizing of a hybrid fuel cell/battery system with respect to operational power profiles, i.e., how to select the best combination of fuel cell stack, battery pack, and reactant storage, and compares its volume and weight with conventional battery systems. This article presents a sizing strategy developed for this purpose, where the optimum combination of fuel cell output power and battery size is analyzed. The strategy is implemented on power profiles from real AUV missions. The sizing strategy will outline the techniques to reach the optimum hybrid configuration capable of meeting the power demand at any time of the mission. Results show that for longer missions, the volume of the hybrid system becomes significantly lower than for the battery system, meaning that the endurance can be increased thanks to the use of fuel cells.

Highlights

A UTONOMOUS underwater vehicles (AUVs) are typically used for missions, such as ocean monitoring and sampling of water or oceanographic data collection
This study presents an analysis to select the best combination of fuel cell (FC), battery, and reactants storage with regard to volume and weight for use in AUVs
The results show that the hybrid system is more volume efficient than the secondary battery one, the final volume is highly dependent on the method used to store hydrogen

Summary

Introduction

A UTONOMOUS underwater vehicles (AUVs) are typically used for missions, such as ocean monitoring and sampling of water or oceanographic data collection. Well-developed sensors, sonars, and underwater communication systems make these AUVs very efficient and capable of ambitious missions. All the onboard equipment requires power, and that is achieved at the expense of endurance of the AUV. The power required for increasing range and endurance is a key performance parameter when evaluating an AUV. Manuscript received December 13, 2019; revised November 13, 2020 and February 12, 2021; accepted February 17, 2021. This work was presented in part at the IEEE OES-AUV 2018 Symposium, Porto, Portugal, Nov. 6–9, 2018. This work was presented in part at the IEEE OES-AUV 2018 Symposium, Porto, Portugal, Nov. 6–9, 2018. (Corresponding author: Ariel Chiche.)

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