The Evtol Battery Balancing Act Umlaut Whitepaper
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umlaut — White — päper. Certification and Time-to-Market: The eVTOL Battery Balancing Act umlaut Whitepaper Content Urban Air Mobility — an Overview 04 Urban Air Mobility Requirements for Batteries 06 Development 08 Market Trends 14 Design 16 Further Consideration 24 eVTOL Vehicle Companies 26 Future of eVTOL 28 References 30 3 umlaut Whitepaper umlaut Whitepaper Urban Air Mobility — an Overview Urban Air Mobility is the aerial passenger or cargo Last mile services will typically include delivery Apart from regular transport services, special appli- transport over short- to-medium distances. In of smaller packages currently transported by the cations are also planned. The German ADAC, which addition to numerous companies building smaller delivery companies (FedEx, UPS, etc.) to end cus- is similar to the AAA in the US, has announced plans unmanned air systems, more than one hundred tomers. Both Air Metro as well as Air Taxi services to work with Volocopter, a German eVTOL startup, companies are focused on the development and will transport passengers. Air Metro is doing that to evaluate eVTOLs for their medical transport mis- production of larger eVTOL (electrical vertical take- on a fixed and regular route e.g., from John F. sions currently conducted through a combination of off and landing) vehicles. Kennedy International Airport in New York City to helicopter and ground-based ambulance vehicles.1 lower Manhattan for example -- Air Taxi services There are three main use cases envisioned for the are intended to operate on demand like a taxi or near future: ridesharing operator today, although restricted to • Last mile delivery of goods take-off and landing infrastructure. • Air Metro • Air Taxis 4 5 umlaut Whitepaper umlaut Whitepaper Urban Air Mobility Requirements for Batteries The three mentioned use cases have specific de- and aerospace certification. As of today2, no vehicle 3. Different flight phases (vertical take-off, hori- using multiple energy storage systems or battery mands on the energy storage setup, which is a has entered the commercial application phase. zontal flight) require high peak, but comparably cell types each optimized for a specific flight pha- central component for fully electric vehicles, espe- There are three high-level business requirements low average power. Even though peak power is se – which might help to keep weight down but cially with highly weight-sensitive aircrafts. The use driving the development of eVTOL energy storage : not used for most of the flight, this requirement increases system complexity. case in which the specific vehicle will be used has again increases energy storage weight a significant impact on the definition of the energy 1. eVTOL operations benefit from long flight All of these engineering requirements need to be storage system. The biggest differentiators are the times, which in turn necessitates low weight and As typical in engineering, there is no easy answer considered simultaneously along with the critical mission profile, e.g. regarding flight altitude and high energy densities to implement all of these requirements at the same time to market implementations. Due to com- turnaround times, and the ground infrastructure time. Final system design usually is the result of petition, market pressure and the comparatively present at the landing spots. 2. Safety, specifically fire safety, is paramount as careful optimization and is a balancing act. For long certification timelines, an early specification an in-air fire is one of the worst-case scenarios example, the different flight phase requirements freeze needs to be achieved, which hinders the full To win the urban air mobility race, eVTOL companies in commercial aviation; however, additional safety could be fulfilled by increasing the peak power potential of modern battery technology. have to strike a balance between time to market, measures typically increases system weight ability of the primary energy storage system which technological advancements like battery technology increases weight. It might also be implemented by 6 7 umlaut Whitepaper umlaut Whitepaper Development V-Cycle development Fig. 01 Development Cycle Concept / Design Production D e fi n i t i o n / D e t a i led D e s i g n Qualification & Integration Aircraft development in general usually follows validation (two critical steps in which umlaut has the classical V-model, due to the structure of the extensive expertise). Specifications will be adjusted Start of „certification lock-in“ time management process and therefore good basis for iteratively if necessary. This approach would result in certification (see Figure 1). the optimal cell for the application and an optimized Vehicle specifications in alignment energy storage system. However, an optimal system with battery system Development, material, overhead, Total Cost of This starts on the vehicle level with defining business might need to be customized and not be able to be Derived from “mission” and power- Vehicle Vehicle train requirements, e.g. redundant Ownership and regulatory requirements. Business require- purchased “from the shelf” and hence might incur systems, swap vs. fast charging ments could be expressed in terms of a mission higher costs. Additionally, due to the constraints in profile including range, speed, load capacities etc. development time, it might be necessary to stop Specifications for each system Interdependencies and Iterations Iterations Development, material, component to fulfil “mission” e.g. Requirements for the powertrain, energy storage, the optimization cycle at a certain point. System System purchasing, quality, Make or weights, volume, cell configuration, and typically battery systems are derived from buy, Strategic Sourcing cooling system, material restrictions these business requirements. In the next level to cell However, it will be extremely valuable for further specifications and potentially even the electrode vehicle generations to document any optimizations Specifications for Cell(s) e.g. voltage, Cost for process time, Cell/ Cell/ level are created from system-level requirements. that could not be included to provide technological internal resistance, homogeneity and Validation depreciation of machines, raw An eVTOL company could definitely take this de- superiority in the next generation. Even if certifi- other components e.g. BMS, Cooling Component Component material, CAPEX and OPEX, tailed approach as this is one of the most critical cation requirements lead to a design freeze with a System quality costs, development components. suboptimal design, subsequent modifications of the Specifications for Electrode, e.g. certified design are much easier to achieve than Cost for raw material, process Thickness of active material, copper Electrode / Part time, depreciation of machines, Following those thoughts, looking at the right side the initial certification. and aluminum Parts of BMS et al., e.g. waste in cutting, recycling of the V-Model, the next steps are testing and reliability of chips/capacitors etc. 8 9 umlaut Whitepaper umlaut Whitepaper High-level overview of early stages Fig. 03 Development of certification process Aviation Industry Start of „certification lock-in“ Concept / Design Design Organization D e fi n i t i o n / Detailed Design Qualification & Integration Responsibility Certification Basis Prep. Finalize Certification Basis Compliance Demonstration Production Development Timeline Organization Responsibility Prep Production To satisfy aerospace regulators both the Design However, no higher risk commercial applications like This is how the authorities have operated until be compliant. Traditionally, those have been the Organization and the Production Organization have in-city transport may be offered with aircraft flown recently, which is not necessarily what benefits the CS23, 25 and 27 for (small) aircraft and helicopters, to be certified by the authorities, e.g. the FAA in under those rules. rapid developments made in the eVTOL space. respectively. Through the SC more targeted certi- the USA or EASA for Europe, respectively. Nevertheless, both the authorities and the eV- fication specifications will be gradually introduced. This early involvement of the authorities, the certi- TOL companies are working on changing this, e.g. After the design and the certification basis has Only a certified design organization according fication basis preparation in the conceptual design through the release of the SC (special condition) been finalized, the production organization takes to EASA / FAA Part 21.J may design an aircraft. phase, leads to some aspects of the design being VTOL by the EASA accompanying close and active over and produces what has been designed. There, The need is to begin the certification process in determined equally early on. Those aspects cannot communication between the EASA and European of course, further certification aspects come into communication with the certification body early in be easily changed later, which leads to a certifica- eVTOL startups3. play which will not be detailed here. the design phase; the process is finished along- tion lock-in phenomenon that requires the use of side with the finalization of the design. As always, fully understood systems. These might not be fully During the certification basis preparation, the de- there are exceptions like eVTOL flown under FAA optimized for performance. sign organization has to determine and claim with “experimental” class rules which are more flexible.