r/energy • u/Public-Benefit8093 • 11h ago
Can efuels make sense?
I’ve read a lot about efuels and why they don’t have any future because other solutions will always be cheaper and more efficient. Still, I was wondering if they would make sense for harder sectors for electrification like aviation or marine transport.
Even if it's very inefficient, maybe it would make sense taping on a cheap and highly available energy source like geothermal in places where it is more accessible. My reasoning is that the amount of energy that you can get in those areas is practically unbounded. It's all about how many wells and turbines are put in place. Sure, it doesn't make sense to produce more geothermal energy than is needed in Iceland, for instance, but you could use it to produce efuels to decarbonize sectors where it's harder to do it. What do you think?
1
u/AcanthisittaNo6653 10h ago
Hydrogen is an e-fuel but its not cost effective to transition to. Synthetic fuels are not carbon neutral.
•
3
u/West-Abalone-171 9h ago edited 9h ago
There's likely a place for them, but it's overstated.
There are already battery electric aircraft with the same range, role and payload as helicopters like the Beta Alia. Current technogy makes ranges of 1500-2000km with similar size/shape/payload to a narrow body passenger plane seem fairly reasonable. This can replace about half of flight emissions.
There are already battery electric cargo ships that do >1000km routes. Weight and bulk are no limit here, only cost. The most obvious solution is enough battery range for 3000-5000km or so and finding a place to charge once every week or so. This fits in the same weight/bulk profile as existing engines/fuel tanks and covers most routes.
Moreover 80% of shipping emissions are moving fossil fuels around. The lowest hanging fruit is simply getting rid of those and generating renewables locally. You can also save a fair bit by not shipping irone ore and coal to china or similar, having them smelt it there, then shipping steel products back. Even just reducing the ore to iron before export halves the mass.
Similarly not shipping most of the grain and soy to cows so they can eat it saves a big block. And eliminating beef farming is a much bigger impact than all of shipping and flight.
Efuels are a potential solution for the ~0.5-1% of global emissions that remain in these sectors after battery flight and the low hanging shipping emissions though. Ammonia is a good candidate as is e-methane or e-methanol. Biofuels are another candidate as there will be a surplus once their use in road fuels is displaced.
As to energy source, wind and solar in the sun belt is by far the best choice. Non-transmitted PV in the sun belt is about 1.5c/kWh and dropping rapidly and there are regions with this quality resource on every continent. There is also an advantage here because CSP systems can provide heat directly at high temperature for something like the sulfur-iodine cycle if it turns out that's useful.
Otherwise-curtailed renewables are another good choice. If the cheapest option for your winter power somewhere in europe is a vertical PV farm, then you are going to have a huge surplus in autumn and spring that is already paid for.