6 ms·
30-50% of electricity is going to renewables, and how. Above that, intermittency and storage is significantly challenging. Don't forget jets. Jets are mega-emi
by acidburnNSA 8y ago
30-50% of electricity is going to renewables, and how. Above that, intermittency and storage is significantly challenging.
Don't forget jets. Jets are mega-emitters and have very few electrification options because lithium-ion has about a 50th the energy per mass as jet fuel.
For heating, cheap, fracked natural gas is dominating in the US, with a battle cry of "better than coal"! Unfortunately it's still extremely high carbon. They do amazing PR though.
China is building a few supercheap swimming pool TRIGA nuclear reactors specifically for district heating in northern regions for winter, where coal is the only alternative. This is wild, but makes sense. They aren't usually used commercially because the temperatures are too low for conversion to electricity. But for straight heat it makes plenty of sense.
Also heat pumps can help but won't get you there alone.
- maxxxxx 8y agoOther than being super explosive would liquid hydrogen work for an airplane?
- nradov 8y agoEven if the safety issues could be resolved, the cooling requirements and high volume make liquid hydrogen impractical for commercial aviation. The most likely carbon neutral solutions for aviation fuel are either algae produced bio fuels, or synthetic hydrocarbons manufactured using renewable energy.
- acidburnNSA 8y ago*Manufacturer using low-carbon energy. At the moment, biofuels are renewable but high-carbon and nuclear is low-carbon but not (considered) renewable.
- carbocation 8y agoI know nothing about the topic, but there seems to be a nice Wikipedia article that your question prompted me to find: https://en.wikipedia.org/wiki/Hydrogen-powered_aircraft https://en.wikipedia.org/wiki/Hydrogen-powered_aircraft
- alan 8y agoI'm suddenly imagining a hydrogen balloon-plane at take off that uses up the hydrogen in the balloon as it flies, until the balloon has been fully reeled back into the plane and it lands on a runway like a normal plane, with reserve hydrogen in its wing-tanks.
- Scoundreller 8y agoIf you time it right, it just slowly drifts to the ground and lands vertically with a slight jolt.
- robin_reala 8y agoDepends on your definition of aeroplane: https://en.wikipedia.org/wiki/Skylon_%28spacecraft%29#SABRE_engines https://en.wikipedia.org/wiki/Skylon_%28spacecraft%29#SABRE_...
- the_duke 8y agoRegarding aviation: worldwide and in the EU, transportation accounts for about 25% of energy consumption [1]. Aviation accounts for 10-13% of transportation [2]. (global data looks similar, although I don't have a link at hand) So while 2.5% is not nothing, it is only a small fraction of energy consumption and could remain Kerosene based in the medium term. Also, a lot of flights could theoretically be shifted to high speed rail. [1] https://en.wikipedia.org/wiki/World_energy_consumption#By_sector https://en.wikipedia.org/wiki/World_energy_consumption#By_se... [2] (2016) https://www.eea.europa.eu/data-and-maps/indicators/transport-final-energy-consumption-by-mode/assessment-9 https://www.eea.europa.eu/data-and-maps/indicators/transport...
- wlesieutre 8y agoIf we can use electricity to turn atmospheric CO2 back into jet fuel it could still be net zero emissions. At that point the planes are just using hydrocarbons as a means of dense energy storage.
- HillRat 8y agoTechnologically-speaking, been done; the economics aren’t quite there yet, but there are some promising noncarbonization paths that potentially could scale to price-parity, depending on global fuel costs.
- dv_dt 8y agoGoing into the future, I think the assumption that one needs to hit exact parity with existing fossil fuels at their current price point will be re-examined. The economic comparison should be conventional extraction fossil fuels + externality costs vs cost of a scaled carbon neutral jet fuel production. One could already see maybe small scale operations capturing niches - maybe if a corporation that operates a private jet wants to further a reduction in their carbon footprint.
- HillRat 8y agoCompletely agree that the best and most market-friendly path is to take socialized CO2 costs and apply them to point-of-emission prices — though I doubt entrenched interests of the iron triangle variety will allow that to happen. Nonetheless, if we assume Johnson and Hope (2012)’s range of $55-$266 social cost per ton of CO2, even current capture-and-sequester methods look price-competitive, which is encouraging!
- tachyonbeam 8y agoCould we power airplanes with ethanol? I've heard that we couldn't realistically grown enough corn/canes to produce ethanol for all cars, but if cars are electric, could we potentially produce enough ethanol for airplanes? If we can't make enough ethanol for all air travel, I'm still optimistic. It's likely that battery densities will become good enough for us to have electrically powered regional jets within the next decade. Then only long flights would need liquid fuels. As a last option, we could also switch to high-speed trains for continental travel.
- i_am_proteus 8y agoPiston-engined aircraft, which are basically just light general aviation aircraft, can and have used ethanol. Most commercial aircraft use jet engines. Other biofuels that are chemically closer to kerosene can be used in most existing jet engines in blends; use of 100% biofuels for hasn't been extensively tested-- but it has been tested![0] This is also the highest-hanging fruit and I wouldn't worry about it in 2019. [0]https://www.navy.mil/submit/display.asp?story_id=96702 https://www.navy.mil/submit/display.asp?story_id=96702
- ams6110 8y agoTurbine engines in theory can run on almost any flammable liquid. However in practice they would need substantial re-engineering. Also ethanol is less energy-dense than kerosene/jet fuel.
- sokoloff 8y agoHave high-power turbocharged piston engines been run on ethanol in service? I’m not aware of any. GA piston fleet has the common property where 20% of the fleet burns 70+% of the fuel as they are working airplanes. (Think CapeAir and similar in passenger service.) Those highly stressed turbocharged engines have lower detonation margins, currently requiring tetraethyl lead additive to meet worst case detonation margins.
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- danans 8y agoA lot of companies are working on electric planes for short haul flights: https://techcrunch.com/2018/07/08/the-electric-aircraft-is-taking-off/ https://techcrunch.com/2018/07/08/the-electric-aircraft-is-t...
- acidburnNSA 8y agoAnd what fraction of aviation emissions are short haul? My hunch is not much. Factor of 50x in energy density really matters in the air.
- Retric 8y agoIt’s closer to 19x when you consider engine efficiency. Heat is not that useful on it’s own. Considering jets already do 9,500 mile flights a 500 mile range seems viable. But, if you start talking significant amounts of electric aircraft, very short landings for battery swapping are also possible. That's not going to get you to Hawaii, but it's still faster than taking a high speed train. PS: You can also push these numbers as electricity is much cheaper than jet fuel. Electric engines also weigh less than batters which allows for a higher mass fraction for fuel. Shorter flights also have lower penalties for going slower. So, an optimized electric aircraft could probably make 800 miles with similar costs to current jets without any major breakthroughs.
- danans 8y agoYes, and it could be viable for short flights with mountains between, where it's hard to build high speed rail, like flights LA<->Las Vegas.
- Retric 8y agoOps: Electric engines also weigh less than jet engines which allows for a higher mass fraction for batteries.
- jabl 8y agoReally? I thought turbines were really excellent in terms of power to weight?