31–40 of 55 posts
Non-paywall link: https://www.google.nl/url?sa=t&rct=j&q=&esrc=s&source=web&cd...
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There might not be a need to equal the energy density of jet fuel in a battery. If the efficiency of the engine and propulsion improve significantly compared to fuel jets, an electrical system might not need that much energy after all. See the hybrid car: the efficiency of a regular engine (VW Diesel not taken into account ;-) is relatively low. If an electrical engine can be twice as efficient, you only need half th…
Wait, what? A good electric motor is already ~90% efficient. How are you going to double that?
Earlier quoted context omitted.
Wait, what? A good electric motor is already ~90% efficient. How are you going to double that?
The electric motor is around 90% efficient, but the thermal efficiency of a jet engine is (if I recall correctly) only around 30%. So the batteries only need to contain 1/3 of the energy of the jet fuel. Batteries are still a long way off from this, but that factor of 3x makes it somewhat nearer than it would otherwise be.
Earlier quoted context omitted.
Wait, what? A good electric motor is already ~90% efficient. How are you going to double that?
The electric motor is around 90% efficient, but the thermal efficiency of a jet engine is (if I recall correctly) only around 30%. So the batteries only need to contain 1/3 of the energy of the jet fuel. Batteries are still a long way off from this, but that factor of 3x makes it somewhat nearer than it would otherwise be.
Beamed-energy flight systems are being developed for space launch[1], but I don't know of anybody yet doing this for plain old aviation. It's a gap waiting to be filled.
Earlier quoted context omitted.
Wait, what? A good electric motor is already ~90% efficient. How are you going to double that?
By reducing wasted energy by half, thereby increasing efficiency to ~95%.
The real breakthrough in electric aviation will come when it is combined with beamed energy. Rather than storing power onboard the vehicle, you have ground-based stations which power the vehicles with tracking microwave tightbeams. That way, you only need enough onboard battery power to take off, land, and bypass one broken ground station -- maybe 15-20 minutes of total flight time. This would allow electric aircraft…
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How about solar-powered planes? I would assume not having to carry an energy source (except for emergency use) is a huge efficiency win. And it's always sunny in the stratosphere (well, not at night).
There's a very strict limitation on solar planes that depends on the panel efficiency and other material science avances as well as the shape and, especially, its height. The bigger you make the jet, the more of its surface you have to cover with solar panels. However, while the mass grows geometrically with the size because of volume, the surface area of the panels only grows exponentially (x^3 vs x^2). Just like wi…
Earlier quoted context omitted.
Wait, what? A good electric motor is already ~90% efficient. How are you going to double that?
The electric motor is around 90% efficient, but the thermal efficiency of a jet engine is (if I recall correctly) only around 30%. So the batteries only need to contain 1/3 of the energy of the jet fuel. Batteries are still a long way off from this, but that factor of 3x makes it somewhat nearer than it would otherwise be.
Li ion batteries still have a LONG way to go in energy density compared to Jet A kerosene. Jet A, about 43 MJ/kg. Lithium ion, <1 MJ/kg.
Yeah, battery technology really needs to improve. In fact, there needs to be some revolutionary discovery in order for electric planes (and a lot of other awesome things) to be feasible...