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Tangential to the main article point but… The energy density scatter plot is physically correct but misleading and everyone makes this mistake. From an engine
by api 2mo ago
Tangential to the main article point but…
The energy density scatter plot is physically correct but misleading and everyone makes this mistake.
From an engineering point of view you have to use work delivered at the end of the drive train not fuel raw energy content.
When you do that lithium ion batteries compare more favorably to liquid fuels. That’s because the conversion path is more than 90% efficient. For ICE engines you’re starting with only 20-40% Carnot efficiency (depending on how good and in good shape the engine is) and then losing in the transmission and then losing more because ICE cars have more other gears and moving parts. Power to wheel is pretty terrible. Most of the energy from gasoline heats the air around the car.
This is also why you get outrageous sounding but accurate things like: an EV charged on 100% coal fired electricity emits less carbon than a typical gasoline car. The fact that coal is literal pure carbon fuel is made up for by the high thermal efficiency of a giant supercritical steam turbine vs a small piston engine. Coal burns real hot too (steeper thermal gradient). So more of the energy from coal ends up doing actual work vs heating the air. (Well directly heating the air I mean.)
- thelastgallon 2mo agoYes, electricity should be the only abstraction layer to deliver energy to end user. We can extract a lot more energy from fossil fuels in large scale plants and also continuously switch out dirtier fuels with clean energy. For example, no need to build natural gas infrastructure to every home. Use induction stoves (or electric coil -- already 67% of homes). Heat pump water heater instead of gas. And heat pump for HVAC. If all energy bills are consolidated as electricity (instead of gas, natural gas and electricity), most people would install solar on their rooftops, buy EVs, and save ~$1000/month on energy bills.
- mb7733 2mo ago> We can extract a lot more energy from fossil fuels in large scale plants This isn't true at all for natural gas. Burning it for heat in the home is much more efficient than burning it in a plant, converting it to electricity, transferring that electricity, then turning that electricity into heat.
- idontwantthis 2mo agoThat is false. Heat pumps are more efficient than burning gas in a home even when the electricity came from burning gas.
- mb7733 2mo agoIt does not follow that "We can extract a lot more energy from fossil fuels in large scale plants"
- maxwwwt 2mo agoThe theoretical efficiency maximum for burning gas in a home is 100%. Most systems won't hit that because they need to vent waste gases, which carry some heat away. Heat pumps are significantly more efficient than 100%. They can get to 500% efficiency. So no, it's definitely not more efficient to burn gas in a home. (To say nothing of the safety of running gas lines to every house.)
- mb7733 2mo agoCompletely separate conversation. I was responding to the statement "We can extract a lot more energy from fossil fuels in large scale plants".
- floatrock 2mo agoYou might be missing the point of heat pumps, and your statement was really about end-heat in homes. You said > Burning it for heat in the home is much more efficient than burning it in a plant, converting it to electricity, transferring that electricity, then turning that electricity into heat. Burning it for heat in the home may be something like: 99% transport efficiency (gas distribution systems lose maybe 1%) * 80% combustion efficiency (a lot of heat energy still goes out your chimney as exhaust). Call it 79%. If you spent more for a high-efficiency burner with extra heat-recovery stages, you could get into the 90's. Compare to: burning it in a plant (power plants can run efficient combined-cycle infrastructure, which is about 60% efficient turning it into electricity), transferring that electricity (plant-to-home transmission & distribution losses are 8-15%, so call it 85%), then turning that electricity into heat (and here is where heat pumps shine... heat pumps don't burn electricity, they use it to move heat, so they can have efficiencies above 100%). So compare that 79%-90% "burn for heat in the home" efficiency to 60% * 85% * 300-500% = 150-255% efficiency for "burn it in a plant, convert to electricity, transfer that electricity, then turn that electricity into heat".