Batteries are the determining factor in the success of the global electric transport ecosystem.
Although removing fuel may appear beneficial, if it is replaced with a consumable battery – the environmental costs are simply transferred to 3rd parties; battery manufacturers and power stations.
The importance of high power density
Consistent power is something we are used to with combustion engines, however batteries consistently reduce their power output every time the are used. This is a huge problem as it results in reduced range and performance.
In the context of electric aircraft, any reduction in battery performance is extremely dangerous. It results in reduced thrust, payload capacity, range and flight envelope. Compounded by the fact that the performance reduction is unpredictable, pilots and operators essentially must anticipate this performance reduction and plan accordingly.
In contrast to internal combustion, where thrust:mass ratios increase as you fly (due to gradual fuel burn) batteries become weaker and weaker as they near zero charge, while staying at the same mass. In practice, this results in the opposite paradigm to ICE, one of constantly reducing performance throughout the flight – making loitering and landing after a long flight a very dangerous proposition.
Removing explosive and flammable battery ingredients
As the performance reduction occurs, the fire and explosive risk of Lithium based batteries increases exponentially due to hydrogen production within the cell.
Further, Lithium batteries have water based electrolytes, forming lithium hydroxide and hydrogen gas when they come into contact with each other.
Throughout their use, lithium batteries heat up. Hydrogen gas builds up within the cell like a small explosive balloon – this is the source of the initial explosion sometimes seen in battery fires. The endlessly burning fire that follows is the lithium reacting with the electrolyte – which is only made worse by adding more water.
Lithium based batteries are highly reactive and dangerous and should never have been considered for any consumer application.
What about generators?
Internal combustion generators potentially offer high energy density of fuels, however as of 2022 there are no ICE generators capable of the high burst power output levels required by EVTOL aircraft.
The power density to mass ratio of generators is so low that they are effectively equivalent to high capacity batteries when applied to a high power system. In order to come close to battery Power Density, a ultralight turbo rotary/wankel style engine running constantly at max rpm is still not enough.
In effect, this means generators still need to be combined with a battery like Powercell to meet the power output or ‘burst’ requirements of a high energy vehicle.
By meeting the requirements of this program, Aura is directly mitigating these issues, making electric transport environmentally and economically viable on a global scale.