If the civil aviation wants to meet very strict emission production standards in the future, it will have to focus on other methods of propulsion than those currently based on fossil fuels. Airbus is now working on a superconducting electric drive with a cryogenic system.
One of these alternatives to current fossil fuel propulsion is electric propulsion. The propeller or jet motor will be blown by the electric motor. The discussion revolves around how to obtain this energy, how to store it and how to efficiently brew it to the engine.
The problem so far is the high energy intensity of air traffic, because for the takeoff of a medium-sized airliner type Airbus 320, you need about 40 MW of energy, whether in the form of current liquid hydrocarbon fuel or stored electricity. Leaving aside the source of energy on board, we do not yet have a satisfactory effect on the transport of energy to power.
One of the biggest obstacles to the simultaneous use of high-performance electrical systems on aircraft is their unsatisfactory power / weight ratio. In other words, day systems do not allow the installation of the necessary power without too much weight, which is not necessary for the aircraft. If it were possible to overcome the pellets in the form of very strong, and therefore soft, water and thus the limit of 30 kW / kg of power of electronics, which currently prevents the development of electrical propulsion systems in aviation, it would open two new directions.
One such direction is the Airbus UpNext initiative. He strives for applied research in the field of superconductivity, for which the demonstrator is preparing his project ASCEND (Advanced Superconducting & Cryogenic Experimental PowertraiN Demonstrator).
Superconductivity as a physical phenomenon was discovered by the Dutch scientist Heike Kamerlingh Onnes in 1911 (in 1913 he received the Nobel Prize for it). The property of all conductive materials is electrical resistance, which reduces the efficiency of transmission (and thus generates low heat). Through this penetrating reduction of the temperature of a specific conductor to 20 K (-253 C), below the so-called critical temperature, in some materials the resistance disappears abruptly and thus to the practical exclusion of magnetic silos from the conductor (Meissnerv effect), and to a very thin layer below surface, the so-called London penetration depth.
The extremely low temperatures at which this phenomenon occurred were in practical use for another 75 years, but in 1986 two researchers, IBM Bednorz and Mller, discovered copper-based superconductors (originally made of solid mercury) that had a critical temperature of 35 K. At present, there are materials TBC-CO (thallium-barium-calcium) and HGBC-CO (mercury-barium-calcium) with a critical temperature of 125 K, respectively. 133 K (-140 C). A totally widely distributed liquid nitrogen, with a boiling point of 77 K, can be used as a refrigerant for such water, and although it is still a difficult technical implementation, such a project is not limited to the laboratory, but can be considered for practical application.
Today, superconductors with a shower are used in electrical power cables, in magnetic resonance imaging (MRI) and nuclear magnetic resonance (NMR) imaging devices, and in magnetic phase and excitation accelerators. However, the field of aviation to use this technology insole.
How cryogenic and superconducting technologies help increase the efficiency of electric propulsion
ASCEND is this program that can demonstrate at any time that an electric or hybrid-electric drive system, supplemented by cryogenic and superconducting technology, can be two to three times less conventional systems, thanks to light conductors and an increased power limit of over 30 kW / kg, without to negatively affect the 97% efficiency of the rake machine.
To achieve such a goal, ASCEND 500kW has a drive machine, which contains:
- superconducting distribution system, wind cable and protection
- cryogenically cooled motor control unit
- supravodiov motor
- kryogenn systm
The base of the bottom is a ndr containing a cryogenic / subcooled liquid, which is divided into two circuits. First of all, for the protection and safety distribution, ie the current limiter and the certainty where it can be cooled by the beer streams. This circuit continues, together with the DC line, to the motor unit, directly influencing the speed and torque, which itself communicates with the aircraft avionics.
The second circuit is connected to the AC line output from the dic unit and continues with the nm to the electric superconductor motor. The cryogenic system can maintain a temperature in both circuits at 30 K at the inlet and 120 K at the inlet.
The aim of this demonstrator is to show that, given the current technologies, it is possible to halve the weight of the entire system, keep the voltage below 500 V and reduce electrical losses by half. The measure is to demonstrate the viability of the superconducting drift machine and later issue a recommendation for the application of such systems in aircraft.
The ASCEND component, in addition to optimizing the weight of the distribution system, is drastically increasing the capacity of the entire propulsion system. This is a fairly important weight, because increasing the power of current aircraft electrical systems from several hundred kW to MW, necessary for a fully electric aircraft, is definitely not easy. Simply put, more power increases the weight and complexity of all installations and produces more heat.
If a cooling source with a temperature of 20 K (-253.15 C), ie liquid vodka, was available on board, it could be used to cool electrical systems. This would be related to the efficiency of the aircraft system, due to the less weight and thus less space required for each unit.
E-Aircraft Systems House is Europe’s largest research facility dedicated to the capabilities and limitations of future propulsion technologies. Here, Airbus is testing new electrification initiatives not only for its own companies, but also for other entities. In short, it’s about power, weight reduction and price reduction.
Electrification and hybridization, combined with your autonomy and digitization, will require new ways of interacting and driving propulsion systems. These systems are, and will be, simulated and tested first here, and the inputs will be used not only in aviation, but also in other fields dealing with electricity used for transport systems, such as the hyperloop of the European Zeleros start-up.
E-Aircraft Systems House
When and where new concepts of aircraft of movable walls or waves of electricity will emerge, depending on many factors, including the price of raw materials (oil / electricity), availability of technology, new rules in the form of constructions and releases issued by individual states, and thus increasing pressure on the sustainability of development, ie the protection of the environment. And one of the very interesting technologies is a new way of storing electricity in the form of solid batteries, ie without the liquid electrolyte present even in today’s best Li-ion batteries.
Lithium-ion batteries are all around us, from cell phones and electric cars. Over the last ten years, prices have fallen, due to the volume of production and thus the development, the line in packs for cars by 90 percent to the current about 120 USD / kWh. But at the same time, in addition to the lack of capacity, the batteries have a very safe safety feature for the air force. The electrolyte levels are flammable. According to the charge is slow and innovation in the form of increasing according to nickel to the cost of expensive cobalt, although it reduces the price and improves performance, increases the volatility of the battery.
On the other hand, fixed batteries (solid-state batteries without liquid) are safe, cheaper, and can be used for long periods of time without degradation, so they have fewer demands on the consumption of precious and expensive raw materials. They can be built on top of each other, like bricks, and they can be used to fill differently shaped spaces. They are easy, they reach full capacity in about ten minutes and mainly have a higher energy density, they can provide e.g. double the range of the car. Graphite and cobalt can be completely omitted during production, so the process of recycling batteries is simple and safe.
The electrolyte, separating the negative and positive electrodes of the battery, is designed to increase the stability of both electrodes. The main ingredient in terms of volume, the electrolyte of current Li-ion batteries is carbonethylene, which is flammable and poses not only the risk of hoen but also toxic gases. For obvious reasons, this is unsuitable for aircraft.
Battery energy density
Solid-state batteries, which are currently in development, use solid materials for the electrolyte, which are non-flammable or at least resistant to self-ignition. These are ceramic materials (oxides, sulphates, phosphes), glass or solid polymers. They can have energy density several times. Non-combustible properties reduce the risk of thermal runaway, which makes storage more difficult, and thus better characteristics of density volumes.
Fixed batteries have been known for a very long time, with a hurry to use e.g. in pacemakers. But they have always been extremely expensive, which is justifiable when it comes to miniature low-power, especially when it contributes to health or even the saving of life. With the industrial birth of electric cars, however, the research got the horse available to the necessary financial land, without which it is not possible to achieve a qualitatively new level.
The main problem with using a battery in an airplane, unlike a car, is temperature. In general, batteries have a maximum capacity above 10 C, up to 5 C have good properties, but as the temperature decreases, the power decreases rapidly. However, aircraft normally move in temperatures of -56 C, which is the standard atmospheric temperature at eleven kilometers. Even turboprop machines for regional transport fly at levels of 25,000 feet, where it is -35 C. Recent research suggests that solid batteries can be resistant to the effects of low temperatures and up to -20 C, which in flight is about a kilometer. The longer the flight, the flight level, in the geography (in the north, but so in the south) and even in the middle of the year, the faster the whole structure of the aircraft cools down. At dnench, it is not uncommon for the fuel temperature in the kilns to drop to -40 C, which is, by the way, the alert temperature for Jet A fuel, below which kerosene could freeze in the ndrch.
If batteries as an energy source for aircraft propulsion units actually occur, they will need to be thermally insulated or stored in a heated area so that such cooling does not occur. Or, given the huge current investment in electromobility, new materials will be discovered in the near future to withstand such temperatures. The future is now.