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You haven't heard the number before? Combustion engines are physically limited to a maximum of 40% efficiency. But that is at their peak performance point. That
by _ph_ 4y ago
You haven't heard the number before? Combustion engines are physically limited to a maximum of 40% efficiency. But that is at their peak performance point. That is basically the efficiency a thermal power plant runs on. But with cars, you are often far off the optimal operations point, so the real life efficiency is much lower, real-world efficiencies are below 20%. That is also the reason, hybrid engines save some fuel, as they aim to raise the average efficiency a bit.
Electric engines have efficiencies of about 95%. There are some charging losses and network transmission, but the 60% efficiency needed to be 3x efficient as ICE cars are easy to hit.
Or to calculate the other way around: a Tesla Model 3 uses less than 20kWh/100km. That roughly equivalents to 2l of fuel per 100km. Most cars use 6 to 8l for comparable performance, so the 3x factor checks out well.
- _hcuq 4y agoThe life cycle emissions of an EV are about half those of an ICE. So maybe a 2x factor is better. EV manufacture has a higher environmental cost than ICE. https://www.ucsusa.org/resources/cleaner-cars-cradle-grave https://www.ucsusa.org/resources/cleaner-cars-cradle-grave
- _ph_ 4y agoThat might be true, but we were talking about the energy consumption we have to replace, and that is the comparision of the fuel vs. elecricity used.
- sidewndr46 4y agoYou're just changing the point you measure the conversion losses at. Yes, electric motors are commonly 90%+ or 95%+. Even really bad ones hit that number. When an EV is being charged by a natural gas turbine hooked into the electric grid, the efficiency is about the same. Basically imagine if instead of having an transmission in my regular truck I just coupled my engine to an enormous alternator. Then used the electrical energy to run electric motors driving the wheels. It is in no way more efficient.
- _ph_ 4y agoNo, if we are talking about decarbonization, we are not using a natural gas turbine to charge the electric car but solar, wind, water.
- MagnumOpus 4y agoEven if you generate energy using oil or natural gas, it helps that the combustion happens in a 55-60% efficient combined cycle power plant rather than a 20-30% efficient car engine. And of course it enables power generation that is not bound to inefficient combustion - be it hydro, solar PV, wind etc.
- sidewndr46 4y agoAbsolutely, it is a step in the right direction. But the small jump in efficiency from say 40% to 55% doesn't really do anything. You've still got a carbon footprint that is non-zero. Unless you convince society to build zero-carbon electrical generation it's the equivalent of the British calling the American Revolutionary War a victory on their part. The difference is purely political, societal, and cultural. None of which can change the laws of physics. My observation is United States society simply doesn't want or care about zero carbon electrical generation. Nuclear fission was figured out a long time ago & we basically never built any significant capacity in that regard. Fossil fuels are cheap, which means cheap energy.
- ZeroGravitas 4y agoYou can explore this question in depth here: https://evtool.ucsusa.org/ https://evtool.ucsusa.org/ Basically, even if you assume that the grid will not decarbonise, the least efficient EV beats the most efficient ICE everywhere in the US. The average is 4x better. With today's grid. Once you accept the reality that the grid is getting greener, it's no contest.
- _hcuq 4y agoNo contest, yes. But can the world afford EVs even with the improved efficiency?