Thread by @thatsamoray

Before Christmas @crisortunity and I published a paper at @a_free_ride about the greenhouse gas mitigation potential of electric aviation in the UK. You can read it in full here: afreeride.org/wonkery.

But for those who don't have time to read it here is a thread:

There is *a lot* of excitement building around electric aviation. It's touted as a pathway to ⬇️ CO2 emissions, ⬇️ local noise and air quality impacts and ⬇️ operating costs for airlines.

Some are even talking about electric planes leading the industry away from hub & spoke to a new, distributed model of operation (at least for short haul flights). But the industry faces some really big challenges.

In common with all electric vehicles, an electric aircraft's range will be key to market development so the first question this analysis sought to answer was: what sort of performance would be needed to cut the UK's aviation emissions by a useful amount?

To answer this question we took data on the number of passengers (pax) flying to, from and within the UK and calculated the distance between airports.

Distance x pax = total passenger-km (pkm) flown

pkm x emission factors = CO2 emissions generated on each route.

Now we have a data set that allows us to see what the distribution of CO2 emissions is for different distances flown and it looks like this chart:

[Note: this CO2 saving is a maximum technical potential from electrification i.e. if we have no aircraft burning 🦖🛢🦖 + a zero carbon electricity supply. Hybrid aircraft burning fossil fuels or a non-zero carbon electricity supply would reduce that potential]

We can see that domestic and short haul routes could see quite rapidly growing mitigation potential with increasing aircraft range. 1,500km (considerably more than anyone is currently proposing for electric only range) could cover all of domestic + ~1/3 of short haul emissions.

Unsurprisingly it will be a struggle to electrify long haul routes, with ~90% of long haul emissions being on flights >4,000km (2,500 miles).

Electrifying a slice of domestic and short haul flights is well worth pursuing, but what is the extent of domestic and short haul aviation's contribution to UK emissions? The overall impact on emissions of the different hauls is best seen in this stacked chart:

Domestic aviation accounts for ~4% of total UK aviation emissions and short haul accounts for ~24% so even if we electrified all of domestic and short haul there'd still be ~72% of emissions from long haul operations.

In order to electrify 30% (say) of UK aviation’s emissions we will need aircraft with a real world operating range of 3,000km and it would take transatlantic ranges of double that to electrify 50% of UK aviation’s emissions.

[As an aside, an interesting feature of these charts is the flat section followed by a sudden ramp up which starts at about 5,500km. This is the distance at which both the east coast US and Middle East airports come into range.]

We can also see how easily (or not) the major airports of the UK could electrify. The impact of Heathrow's (LHR) enormous size coupled with its long haul route structure is clearly seen on the total:

We also took a look at the designs out there. It's early days & many designs are little more than renderings at this stage, but all are falling into one of three camps:

1) electric vertical take-off and landing (eVTOL),
2) commuter
3) regional jets/turboprops.

The eVTOL space is most active with a dazzling array of concepts targeting a ~100km range & carrying up to ~6 pax (the 240km Bell Nexus, which is all over Twitter today, is a 4 seat hybrid).

Check out @ElectricVTOL's directory for a comprehensive list: evtol.news/aircraft/

Commuter aircraft carrying 10 to 20 people 1,500km are best represented by the hybrid electric (and Boeing-backed) @zunumaero and the beautiful battery electric @EviationAero Alice:

There are only a few electric regional jet concepts announced to date. Best known is the 150-seat battery electric @weflywright which has garnered a lot of press attention in the UK thanks to their links with Easyjet.

Airbus, as part of a consortium, is exploring hybrid regional jets in the E-Fan X powerplant demonstration project but has not announced a timeline for either a hybrid or battery electric aircraft. Nor has Boeing.

The eVTOL market is effectively be brand new (bar some existing helicopter operations) and the commuter market in the UK is very limited, so there is little scope for reducing CO2 emissions from UK aviation in these markets.

We don't know exactly what the regional jet & turboprop market's contribution to emissions is, but based on the % of seat-km flown by these types of aircraft I estimate it to be somewhat less than 2% of UK aviation emissions, so electrification here can only have a small impact.

There currently appears to be no serious proposals for electric aircraft that would compete with the 16,000 narrowbody and nearly 6,000 widebody aircraft currently in service globally.

That's probably enough of a thread for today but I'll continue tomorrow to try and answer two more questions which cropped up during the research:

What engineering options are available to aircraft designers to make useful electric aircraft a reality?

and

What electric flight range is theoretically possible?

If you're too excited to wait until tomorrow then you can read the report at afreeride.org/wonkery/

Pt 2 continues here:

https://twitter.com/thatsamoray/status/1083758254235312128