Browse Topic: Fuel cells
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This SAE Information Report contains definitions for hydrogen fuel cell powered vehicle terminology. It is intended that this document be a resource for those writing other hydrogen fuel cell vehicle documents, specifically, Standards or Recommended Practices.
The purpose of the NATO Next Generation Rotorcraft Capability (NGRC) Support Partnership funded Novel Powerplant concept study was to identify, analyze, and compare novel powerplant concepts that could fulfill the NGRC need in a solution-agnostic approach. The outcome of the study provided NSPA and the NGRC participating nations with increased knowledge and understanding of the powerplant domain to inform assessment of future NGRC platforms. This study modeled four aircraft configurations to derive propulsion sizing requirements and compared propulsion configurations for each. The propulsion system configurations considered included three levels of conventional gas turbine technology (In-service GT, 2025 GT, and 2035 GT), hybrid electric (battery), hybrid hydrogen fuel cell, and hydrogen combustion. The results of the study considered both quantitative and qualitative evaluations. The quantitative analysis determined aircraft and propulsion system sizing to align with the expected NGRC need at different max cruise speeds, and compared performance along with recurring, non-recurring, and operational costs for each. The qualitative analysis investigated the impacts of wider technical, capability, and supportability considerations for each propulsion concept. Assuming a notional NGRC entry into service target date of 2035, this study shows that, when considering both quantitative analysis and a qualitative review, a modern gas turbine is the most reasonable solution space to deliver the performance and multi-mission capability expected.
A hydrogen economy is an increasingly popular solution to lower global carbon dioxide emissions. Previous research has been focused on the economic conditions necessary for hydrogen to be cost competitive, which tends to neglect the effectiveness of greenhouse gas mitigation for the very solutions proposed. The holistic carbon footprint assessment of hydrogen production, distribution, and utilization methods, otherwise known as “well-to-wheels” carbon intensity, is critical to ensure the new hydrogen strategies proposed are effective in reducing global carbon emissions. When looking at these total carbon intensities, however, there is no single clear consensus regarding the pathway forward. When comparing the two fundamental technologies of steam methane reforming and electrolysis, there are different scenarios where either technology has a “greener” outcome. Despite misconceptions, steam methane reforming produces fewer total carbon emissions than current on-grid electrolysis due to the carbon emissions released by power plants. Similarly, for storing and deploying hydrogen, the optimal solution set will depend upon use case and geographic location. For example, truck transportation of gaseous hydrogen becomes less carbon efficient than liquification for distances greater than 614 miles. This paper explores the nuances of the factors of production that affect the total carbon footprint of a given technology, and how other emerging complimentary technologies, such as carbon capture storage and utilization, may change this carbon footprint calculation. As new technologies are evaluated, there are technological, political, and economic factors that will shape the landscape of how and where, hydrogen is produced, and the global infrastructure by which it is distributed.
This paper analyses the possibility of using hydrogen fuel cells as main energy provider for small to medium-sized eVTOL UAVs. A simplified model for eVTOL UAVs, which covers all relevant areas of aircraft design, including aerodynamics, structural mechanics, propulsion and systems modelling, is presented. Sensitivity studies with various design parameters, including aspect ratio and design cruise speed are performed to show their influence on the configurations’ performance. A comparison between pure battery electric and fuel cell hybrid UAVs is taken. The result of this paper is, that a hydrogen fuel cell hybrid configuration can have a better performance than a battery electric and it can be worth the effort to implement the fuel cell. To achieve this, the mission should require a long endurance and have hover and transition times reduced as far as possible, which both enable the high energy density of the hydrogen system to unfold its full potential. Also, the aircraft needs to be as aerodynamic efficient as possible in order to reduce the fixed weight of the hydrogen fuel cell. Respecting these requirements and accepting a reduced versatility of the aircraft, a fuel cell hybrid eVTOL UAV can easily outperform one with a pure battery electric power supply.
This standard specifies the communications hardware and software requirements for fueling hydrogen surface vehicles (HSV), such as fuel cell vehicles, but may also be used where appropriate, with heavy-duty vehicles (e.g., busses) and industrial trucks (e.g., forklifts) with compressed hydrogen storage. It contains a description of the communications hardware and communications protocol that may be used to refuel the HSV. The intent of this standard is to enable harmonized development and implementation of the hydrogen fueling interfaces. This standard is intended to be used in conjunction with the hydrogen fueling protocols in SAE J2601 and nozzles and receptacles conforming with SAE J2600.
In order to maximize range, a substantial portion of the interior volume of aircraft is allocated for fuel containment. To ensure the safety of aircrew and passengers, these systems must contain fuel and retain critical structural integrity in the event of a crash, self-seal and retain structural capability in the event of penetration, and suppress fire in the event of proximate ignition. Traditionally, light weight aircraft such as rotorcraft have accomplished these functions with heavy self-sealing bladder offset and isolated from primary structure. Boeing and the US Army Combat Capabilities Development Command Aviation & Missile Center's Aviation Development Directorate (ADD), together with the Joint Aircraft Survivability Program Office, have developed and demonstrated a structurally integrated fuel containment system that efficiently tolerates crash, self-seals, and suppresses fire at a lower weight and volume than traditional systems, thus maximizing space and weight capacity for fuel and payload.
The objective of this paper is to study the impact of combining hydrogen fuel cells with lithium-ion batteries through an ideal power sharing architecture to mitigate the poor range and endurance of battery powered electric vertical take- off and landing (eVTOL) aircraft. The benefits of combining the two sources is first demonstrated by a conceptual sizing of an electric tiltrotor for an urban air taxi mission of 75 mi cruise and 5 min hover. It is shown that an aircraft of 5000-6000 lb gross weight can carry a practical payload of 500 lb (2-3 seat) with present levels of battery specific energy (150 Wh/kg) if only a battery-fuel cell hybrid powerplant is used, combined in an ideal power sharing manner, as long as high burst C-rate batteries are available (4-10 C) for a limited duration (2.5 min). A powerplant using batteries alone can carry less than half the payload; fuel cells alone can not lift off the ground. The operation of such a parallel system is explained using systematic hardware testing and modeling and simulation. The concepts of un- regulated and regulated power sharing architectures are described. A regulated architecture that can implement ideal power sharing is built-up in a step-by-step manner. It is found only two switches and three DC-to-DC converters are necessary, and if placed appropriately, are sufficient to achieve the desired power flow. The power system model is validated with test data and used to gain fundamental understanding of the power sharing architecture.
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