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Development and demonstration of a long-endurance sea surveying autonomous unmanned vehicle with gliding capability powered by hydrogen fuel cell

Periodic Reporting for period 2 - ENDURUNS (Development and demonstration of a long-endurance sea surveying autonomous unmanned vehicle with gliding capability powered by hydrogen fuel cell)

Reporting period: 2020-05-01 to 2021-10-31

The ENDURUNS project aims to demonstrate a hybrid Autonomous Underwater Vehicle (AUV) with gliding capability and increased operational endurance lasting up to several months. The hybrid AUV vehicle is capable of communicating directly with the shore-based Remote Monitoring and Control Center (RMCC), providing updates on mission status and collected data with the help of a lightweight and low cost autonomous Unmanned Surface Vehicle (USV). The use of the USV permits the reception and transmission of data to the hybrid AUV associated with mission updates or changes in mission parameters. The hybrid system once completed will overcome the limitations of current AUVs and gliders by using advanced power packs based on hydrogen fuel cells rather than low energy density state-of-the-art Lithium-ion batteries, efficient control systems and optimised data handling and communication processes.
In the first 36 months, the consortium progress and executed all duties according to the technical annex. Regarding dissemination, the initial dissemination and exploitation plan has been further updated. The majority of anticipated deliverables up to M36 have been submitted either in-time or with an acceptable level of delay. Despite the consortium showing extreme levels of resilience across the board in the face of COVID-19 pandemic, matters outside our control remain including governmental restrictions across the spectrum of activities which are also associated with the execution of the project’s envisaged tasks. This resilience has allowed the majority of the key tasks to be completed satisfactorily although some deliverables have been delayed. Up to M36 the key components of the Autonomous Underwater Vehicle (AUV) have been designed and constructed with the integration on-going. The Unmanned Surface Vehicle (USV) hull tests are pending and as soon as these are completed the installation of the necessary equipment will be carried out. The development of the novel alkaline fuel cell has progressed relatively satisfactorily, however, the consortium has opted to also procure a Proton-exchange membrane fuel cells (PEM) off the shelf for risk mitigation purposes. The PEM fuel cell for the USV is currently undergoing tests. Hydrodynamic trials have been performed for both the AUV and USV with satisfactory results. The hydrogen storage options considered for both the AUV and USV have been analysed and evaluated up to required depths of operation. The data bubble has been designed and the prototype has been constructed. The remote control centre has been developed and initial trials have been carried out. The sensing modules have been assessed together with signal processing and storage requirements. Dissemination has progressed strongly by the consortium with a significant number of journal and conference papers as well as invited talks in Europe, Korea and Brazil.
Ocean exploration remains a sector where evolution has been slow. This is largely due to the technical challenges arising from operating at high depths for prolonged periods of time as well as the cost involved in such activities. State-of-the-art systems used in ocean exploration are based either on Remotely Operated Vehicles (ROVs) that are operated from a manned mothership, or Autonomous Underwater Vehicles (AUVs) which are launched and retrieved by a mothership in the areas of interest. AUVs due to the depths that they operate are powered using li-ion batteries. Unfortunately, such batteries have limited energy storage capacity and therefore, the endurance of AUVs is inadequate for long-term operations. Gliders on the other hand which can operate for longer periods of time are dedicated to simple measurements that require low power and move in a hacksaw tooth motion to avoid using a significant amount of energy for propulsion. However, they are not capable of carrying out more complex activities such as seabed mapping or inspections of offshore facilities.

At the same time however, it is necessary to solve the problem associated with the deployment of the AUV gliders. Currently ROVs and AUVs are deployed using expensive motherships. In our case this requirement is removed through the development of a novel Unmanned Surface Vehicle (USV) with an advanced docking system and submersion capability in case of an emergency arising from extremely adverse weather conditions. The USV can deploy and retrieve the AUV glider as well as exchange information between the AUV glider and the ENDURUNS Remote Monitoring and Control Center (RMCC) that the consortium has also developed. When operating underwater communication between the USV and the AUV glider is achieved via acoustic modem. The USV through the acoustic communication can provide positioning information to the AUV glider without the need for resurfacing. When docked the AUV glider can exchange data with the USV using a Maelstrom advanced wireless communication system which also permits recharging of the batteries onboard the AUV. Hence, even when the hydrogen has been used, the mission can be further extended if required by recharging the battery when the AUV glider docks with the USV. The USV itself is completely autonomous employing advanced radio and satellite communication systems that allow it to maintain constant contact with the ENDURUNS RMCC. The power of the USV is generated from a combination of advanced marinised solar panels spread in the free areas on the top side of the vessel, a PEM FC supplied by hydrogen stored onboard in gas cylinders or liquid hydrogen storage tank and Li-ion batteries. The USV is thus fully electric with the battery being recharged by the solar panels onboard with the fuel cell contributing any additional amounts of energy used but not recovered through the solar panels when necessary. Since the AUV operation requires it to move relatively slowly, this means that the USV does not need to use a lot of energy for propulsion. The majority of the energy will be consumed by telecommunications systems when the USV has reached the location of the mission.

The AUV glider features an advanced data management system incorporating special data bubbles that can be ejected in an emergency or if it is required by the mission. The data bubbles have their own power supply and can communicate wirelessly when near the USV. The ejection of a bubble requires the re-balancing of the weight of the AUV glider through the release of additional weight from the bottom so nominal buoyancy parameters can be maintained during the rest of the operation.

The AUV glider is designed to be modular in nature so the sensor kits can be adapted as required by the mission profile. Moreover, the size of the AUV glider can be changed in order to store more hydrogen or more sensors, especially when longer missions are envisaged. The USV can also be upscaled so it can manage more than one AUV gliders at the same time operating however, within the same vicinity to enable transmission of positioning data. However, it is still possible to move to another area and allow an AUV glider to operate independently if appropriate or necessary. In this case the AUV glider will have to resurface occasionally in order to obtain positioning information.