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Storage energy UNit for Smart and Efficient operation on Tarmac

Periodic Reporting for period 3 - SUNSET (Storage energy UNit for Smart and Efficient operation on Tarmac)

Période du rapport: 2020-09-01 au 2021-11-30

The European project SUNSET is part of the aeronautical research program Clean Sky II, which supports projects whose objective is to develop advanced technologies to increase the environmental performance of air transport in order to reduce CO2 emissions, particulate emissions, noise, and improve technical performance.
SUNSET follows the SOG PEERS project (Clean Sky I) in which Centum Adeneo was involved for all the power electronics and energy storage without any performance objective of power density and stored energy density per kilogram. The objective of this project was first and foremost to demonstrate the feasibility of powering the landing gears of short/medium haul aircraft of European aircraft manufacturers. Following the results obtained at the end of 2015, research on electric taxiing to move the aircraft on the ground using the energy supplied by the auxiliary power unit (APU) has been relaunched as part of the CleanSky II program.
SUNSET is the electrical system that allows fast and bi-directional exchanges on the high voltage DC bus (+/- 540 VDC) during the aircraft's taxiing phases.
All but one of the project's technological objectives have been met: power converter, solid state circuit breaker, battery management system, power controller, battery organization and energy storage density and all associated software; only the storage technology we intended to use to achieve the target weight is not available for the aeronautical market due to the attractiveness of the automotive markets. The battery technologies for the aeronautical market available at the time of SUNSET's choices led us to have 3.5 times the energy required for our application, which implies an extra weight for the storage module. However, the rapid evolution of battery technologies should make it possible to reach the mass and volume objectives within a few years and make it possible to integrate this equipment into aircraft.
The first phase of the project was dedicated to write the technical specification which takes into account the use cases of the final application.
Several technical trade-offs were made to choose the power semiconductor technology, the power conversion topology and to select the energy storage cells.
Power semiconductor technology uses a new current SiC MOSFET device that allows high voltage and high frequency operation with reduced electrical losses.
Selected electrical energy storage cell offers one of the best kWh/kg and kWh/L energy densities.
The results of these trade-offs were used to investigate an initial architecture with a preliminary design of the SUNSET equipment.
After a detailed design stage, the second period of the SUNSET project was devoted to the development, fabrication and validation of the TRL4 demonstrator.
At the end of the second period, the main sub-assemblies were manufactured and tested, and the integration of the demonstrator was began in Sept. 2020.
The third period of the project was divided into two main phases:
First, we completed the assembly of the TRL4 demonstrator by integrating the energy storage module. This demonstrator is composed with only one power string (the three strings are identical). After laboratory tests at Centum Adeneo, this demonstrator was integrated into the overall GATS system at INDRA's facilities, consisting of the wheel actuator developed by SAFRAN LANDING SYSTEMS and the engine control module developed by INDRA as part of the European E-TSIN project. This first integration of the demonstrator into the GATS system allowed us to validate its functional modes on complete operating cycles with connection to the system, data exchange, charging and discharging at reduced power.
After this first system integration, we were able to finalize the development of the key technological bricks for TRL5/6 demonstrator.
This development phase was carried out in order to achieve the power and energy objectives. A TRL5/6 demonstrator has been manufactured with three energy branches.
Laboratory tests at Centum Adeneo validated the performance of the demonstrator in full charge and discharge at 35kW.
Technology dissemination activities have been conducted throughout the project mainly through publications in peer-reviewed journals and participation in conferences.
This dissemination is complemented by technical presentations to our major industrial customers on the different technological components developed within the SUNSET project.
Three different forms of exploitation of the SUNSET results are planned. The first is for the application of green taxiing, at the equipment level, notably with Safran Landing System as a customer. Then, still at the equipment level, with other applications requiring a high-performance energy buffer, such as the use of a fuel cell solution for an aircraft auxiliary power unit or any other hybridization application.
Finally, functional exploitations with the high-performance functions developed in the framework of the SUNSET project could be very useful for the electrification of aircraft, for example-: high voltage battery management system, energy pack, solid state circuit breaker, power converter, etc...
The SUNSET project is part of the e-Taxiing system within the new greener aircraft program. The overall objectives are to reduce energy consumption, emissions and operating costs and thus enable the European aerospace industry to become the world leader in low-emission aircraft. The use of the APU with an electrical energy storage module instead of engine power for taxiing will both reduce carbon dioxide emissions and fuel consumption, and eliminate the need for tractors for the taxiing phases at airport gates.
To achieve these goals, we worked with Ampere Lab. to design a dedicated architecture, using state-of-the-art switching technology with an innovative topology; then we did a huge amount of cell integration work, managing the high voltage of the storage module with a dedicated BMS (Battery Management System) and a solid-state safety circuit breaker. We also managed the cooling of the storage module and the inverter in a small volume to obtain a very compact equipment.
We have all but one of the project objectives: power converter, solid state circuit breaker, battery management system, power controller and all associated software, battery pack organization; but unfortunately, the storage technology we intended to use to achieve this weight is not accessible for the aerospace market due to the volume attractiveness of the automotive market. The battery technology currently available leads us to have 3.5 times the energy needed, which leads to an excess of weight and volume, despite the fact that we have largely exceeded the quantitative density objectives: 30Wh/kg for the storage and 2kW/kg for the power converter and 45Wh/kg and 3kW/kg obtained.
What is important at the end of the project is that we - together with Safran and Clean-Sky/Clean-Aviation - have a clear vision of what needs to be done to be able to integrate such a technology into an aircraft tomorrow. As the cost of energy has recently risen sharply, it is very interesting to go further for this type of equipment and to use all the existing bricks, to follow the compromise of battery technology and to follow the new existing cells that are evolving every day, and to make the prototype evolve to achieve the weight reduction necessary to integrate the technology.
SUNSET operating principle