Battery Aircraft Addendum (part 2)
The previous post was getting on a bit so I left it there however there are a few other things I think are worth saying and in addition a few more examples of the potential range of electric planes would also be useful.
This looks weird but its due to the earth not being flat (sorry flat earthers), in globe view you can see its the most direct route.
If we take a minor detour via the southern tip of Greenland we can make the journey with only an extra 179 miles or about 5% extra distance.
There are other factors to consider which I will gloss over here, such as the trade winds and radar coverage, mostly because if you follow a route that tracks land more closely such as the one above you have more places to stop for battery swaps if needed and better radar coverage.
Switching to a US viewpoint, given one layover stop for a battery swap, you can go from almost anywhere to almost anywhere else in the USA or Canada, unless you want to go from the furthest tip of Alaska to Florida in which case you will need two stops.
Switching back to Swindon, what other destinations could I fly to?
Most planes are not currently refuelled mid-flight as its risky and dangerous to do, however with an electric plane this becomes possible. There are number of ways to do this, even if they are not able to extend the range indefinitely they could add to the usable range and may find niche markets even if not installed on commonly operated vehicles.
On range
I think the examples given in the last post were a bit rubbish. I chose the Cessna as there is a working prototype out there in the real world, but its not a great example for what could be possible in the near to medium future.
So lets use a vehicle (class) that's currently one of the most popular for air travel, the Boeing 737. The current latest and greatest version, the 737 Max has a stated range of between 3700 and 4430 miles. Using the 'convert it' approach and current gen batteries, and the previously calculated 12 times multiplier, we might expect a converted-to-electric 737 to have a range of between 308 and 370 miles. This actually is close to the in development Wright Electric commerical jet that will have a similar payload capacity to the 737 (this vehicle seems like a mostly traditional design, with a few efficiency improvements. I expect to see much more radically different designs over time in future vehicles).
In the last article I stated battery density might improve by 4 times in the next 20 years without giving sources. So lets fix that.
Tesla (Maxwell) believe that a 500 wh/kg battery is highly likely in the coming years. I cant find the link on the Maxwell site but their technology has been widely discussed and the following image from Maxwell shared across the media so I feel safe to share this here.
This is only talking about a single improvement to the cell, using a dry electrode and is already nearly double the current generation. With some additional improvements to the chemistry and cell design, I believe a doubling in the next 5 years is not only possible but highly likely.
The minute physics video that partially inspired this series says the maximum theoretical limit for current generation batteries would be 600 wh/kg and an improved Lithium Sulphur could be 3 times lighter, which would give a theoretical maximum density of 1800 wh/kg and a hypothetical Lithium Oxygen battery (the maximum he believes a practical battery could be) would be 4 times lighter than the Lithium Sulphur which would give them a density of 7200 wh/kg. (He also talks of a hypothetical Lithium Florine battery that could have up to 7920 wh/kg but would likely be to impossible to produce. Actually his numbers are hard to follow as he doesn't give wh/kg for each chemistry. One interpretation of his numbers gives the Lithium Florine battery a density of 12000 wh/kg!)
These are theoretical limits and probably talking about at the cell level, nevertheless, if achieved those theoretical limits would give batteries double the current usable density of jet fuel which as previously discussed is actually around 3600 wh/kg and a 24 times improvement on current batteries.
Therefore I don't believe it is highly speculative to assume that in the next 20 years we will see two doublings, (or a 4 times improvement) from the current 300 to 1200 wh/kg and possibly much more. This would give the 'converted' Boeing 737 Max an electric range of between 1232 and 1480 miles. If we assume that a purpose built electric plane can eek out another 50% more range due to improved efficiencies (see part 3 to see why I don't think that number is unreasonable) that gives that new plane a range of around 2000 miles. Lets see where we can fly on that.
Flights possible.
As previously stated, if you don't mind stopping for a quick battery swap, the usable service range of an electric plane is much extended, but will be limited by large bodies of water or other areas where placing a battery swap station would be difficult. However with a range of just 2000 miles we can probably go anywhere or at least most places, lets have a look:
From my house in Swindon, with 2000 miles I could go direct without stopping to:
- Anywhere in the UK or Ireland.
- Iceland or the southern parts of Greenland
- Anywhere in Europe including parts of Turkey
- Large parts of northern Africa including all of Morocco.
But what about trans-Atlantic flights, how about to New York? Manhattan is about 3400 miles by the most direct route however notice where that route is.
This looks weird but its due to the earth not being flat (sorry flat earthers), in globe view you can see its the most direct route.
If we take a minor detour via the southern tip of Greenland we can make the journey with only an extra 179 miles or about 5% extra distance.There are other factors to consider which I will gloss over here, such as the trade winds and radar coverage, mostly because if you follow a route that tracks land more closely such as the one above you have more places to stop for battery swaps if needed and better radar coverage.
Switching to a US viewpoint, given one layover stop for a battery swap, you can go from almost anywhere to almost anywhere else in the USA or Canada, unless you want to go from the furthest tip of Alaska to Florida in which case you will need two stops.Switching back to Swindon, what other destinations could I fly to?
- Large parts of India with only 1 stop
- Thailand, China, Russia and Japan with 2 stops
- From almost anywhere to almost anywhere in the world with 5 stops
Remember, flights by electric are going to be about 30 times cheaper than flying by conventional plane. Google is telling me a typical flight to New York will cost about £350, India for £400, and Australia £1200. If the costs are reduced by 30 times that would then be: New York for £11, India for £13 and Australia for £40. If you gave me the choice, even if it were a little longer, I know which I would choose. Given that (long range) electric planes will probably be supersonic they will almost certainly be quicker, even with the extra stop overs.
The above numbers look too crazy to be true, it costs me more than that to get a bus to the airport, however I believe these numbers could be correct which I will delve into in another post at another time. Even if the prices just halved most people would choose the electric even at a slower journey.
Far future crazy speculation
This section contains speculation from me and may never happen however it seems to me at least a bit likely that some of these will happen in some form or other.
Solar
Current solar panels are highly inefficient. Whilst this isn't great for putting onto a weight and size constrained vehicle, it is good in that it means there is still a lot of improvement to potentially come. According to this article typical solar panels you can buy today have efficiencies around 20% and have an energy output of about 200 w/m2.
Using information from Wikipedia it looks like the 737 has a fuselage of around 3.7m wide and 42m long. The wing surface looks to be at least a similar size. Assuming you cover half of the top of the fuselage and all of the wings with panels you could generate 22 kw of continuous power using standard panels. This wouldn't really extend the range enough to justify the weight. However, as mentioned, this tech has a lot of room to grow.
There are companies working on panels with an active collection material that could theoretically be as thin as 1 atom thick. Also if we can get efficiencies closer to 100 % than 20 % we could see energy output closer to 112 kw that's also thin and light enough to be incorporated into the paintwork.
According to Stanford University current jets need 7200 kw to maintain cruising flight. Assuming our new vehicle is 50 % more efficient that might be reduced to around 4800 kw. The 112 kw theoretical output is still only 2.5% of that so its going to be at best small range increase.
Space based power
It is possible that the above output could be improved by using lasers or masers beaming power from space. Whilst this idea has serious engineering issues, aeroplanes at least have the benefit that they operate above most of the weather that can block the sun or space based power.
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