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>We can reduce losses from primary to secondary energy by transitioning away from fossil fuels because the losses for these sources are particularly high. This

>We can reduce losses from primary to secondary energy by transitioning away from fossil fuels because the losses for these sources are particularly high. This reduces the amount of heat lost from converting these raw fuels into a usable form, such as electricity. This is false, fossil fuel power plants have efficiencies between 30% and 60%, solar 15% to 25% (or much less if you consider the time that it's dark), wind 20% to 40% (or much less if you consider the time it's not windy). I suppose you can ignore these things because the sun and wind are free resources, but the basic fact is that transforming heat into electricity is considerably more efficient than photovoltaics or wind turbines.

pfdietz 4y ago
This comparison is absurd, for the reason you note and apparently dismiss. Efficiency comparisons are really only relevant when you're looking at the same input.
sbierwagen 4y ago
If you really wanted to do pointless stuff with numbers, you could say that fission has an abysmally low "efficiency" because not all of the mass of the atom is converted into energy, with the majority of it ending up as stable fission fragments or neutrinos that zip through the reactor walls. You start with a U-235 atom that has a rest mass of 218,871.5 MeV and only get 202.5 MeV of heat out of it? Pathetic!
dredmorbius 4y ago
Energy efficiency refers to how much useful output is delivered based on input. For thermal energy generation, net efficiencies tend to range from 20% to highs of about 40--50% via combined-cycle generation, perhaps with cogeneration of generation+thermal heating applications, the latter typically being district heating or industrial heating. There's also the concept of nameplate capacity vs. capacity factor. The former relates to the maximum possible output of a facility, the latter to the attainment of the nameplate capacity over a year. It's not clear to me which of these you're referring to. Moreover, the conversion efficiency of flows such as solar and wind is not directly comparable to the efficiency losses of termal generation for other reasons, namely that the environmental availablity of the uncaptured portion is still generally available for other environmental service. Burning a ton of coal and only extracting 30% of the total energy potential still means you've incurred an opportunity cost of 70% of that fuel stock's energy potential. I will note that there are a lot of shenanigans which are played with nameplate and capacity factors, by both boosters and opponents of renewable / carbon-neutral energy. That said, there's no need to add to the confusion. Confounding conversion efficiency, capacity factor, and deadweight opportunity costs and losses is a slippery business at best.
jyounker 4y ago
The ongoing cost of mining sunlight is nearly zero.

pfdietz 4y ago

This comparison is absurd, for the reason you note and apparently dismiss. Efficiency comparisons are really only relevant when you're looking at the same input.

sbierwagen 4y ago

If you really wanted to do pointless stuff with numbers, you could say that fission has an abysmally low "efficiency" because not all of the mass of the atom is converted into energy, with the majority of it ending up as stable fission fragments or neutrinos that zip through the reactor walls. You start with a U-235 atom that has a rest mass of 218,871.5 MeV and only get 202.5 MeV of heat out of it? Pathetic!

dredmorbius 4y ago

Energy efficiency refers to how much useful output is delivered based on input. For thermal energy generation, net efficiencies tend to range from 20% to highs of about 40--50% via combined-cycle generation, perhaps with cogeneration of generation+thermal heating applications, the latter typically being district heating or industrial heating. There's also the concept of nameplate capacity vs. capacity factor. The former relates to the maximum possible output of a facility, the latter to the attainment of the nameplate capacity over a year. It's not clear to me which of these you're referring to. Moreover, the conversion efficiency of flows such as solar and wind is not directly comparable to the efficiency losses of termal generation for other reasons, namely that the environmental availablity of the uncaptured portion is still generally available for other environmental service. Burning a ton of coal and only extracting 30% of the total energy potential still means you've incurred an opportunity cost of 70% of that fuel stock's energy potential. I will note that there are a lot of shenanigans which are played with nameplate and capacity factors, by both boosters and opponents of renewable / carbon-neutral energy. That said, there's no need to add to the confusion. Confounding conversion efficiency, capacity factor, and deadweight opportunity costs and losses is a slippery business at best.

jyounker 4y ago

The ongoing cost of mining sunlight is nearly zero.