In the US, it's cheaper to build and operate wind farms than buy fossil fuels

Re:In the US, it's cheaper to build and operate wind farms t... by adrianN on Sunday August 18, 2019 @06:18AM (#20729360)

Unless you want to cover really significant amounts of land in solar panels wind farms, you shouldn't use synfuels unless absolutely necessary. Not only do you use half of the energy just making the fuel, all applications where you burn it have terrible efficiency compared to electric alternatives. ICEs have an efficiency of maybe 30%, heat pumps easily produce two or three Joules of heat for every joule of electricity.

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Re:In the US, it's cheaper to build and operate wind farms t... by thinkcontext on Sunday August 18, 2019 @10:49AM (#20730444)

We already devote really significant amounts of land to energy in the form of corn for ethanol, ~10% of total US cropland. Corn only captures 1% of incoming light vs ~20% for PV solar, so it would be a huge gain in land efficiency to replace corn ethanol with an energy equivalent amount of PV.

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Re:In the US, it's cheaper to build and operate wind farms t... by jacobolus on Sunday August 18, 2019 @02:10PM (#20731815)

This is a result of corn subsidies, not a naturally economically efficient land use.

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Re:In the US, it's cheaper to build and operate wind farms t... by mapt on Monday August 19, 2019 @01:29PM (#20739762)

Specifically, corn subsidies and the Iowa Caucus.

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Re:In the US, it's cheaper to build and operate wind farms t... by adrianN on Sunday August 18, 2019 @01:42PM (#20731633)

That's a good point. The amount of resources we waste on bioethanol are huge.

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Re:In the US, it's cheaper to build and operate wind farms t... by sokoloff on Sunday August 18, 2019 @08:42AM (#20729842)

I think creating aviation fuels from renewables is the path towards carbon-neutral aviation as one example where this tech makes sense. Shipping might be another, but I’m less familiar there.

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Re:In the US, it's cheaper to build and operate wind farms t... by raverbashing on Sunday August 18, 2019 @07:20AM (#20729560)

You're completely right.

But it might (big might) be worthwhile for a transition period.

ICEs are my pet peeve, mechanical engineers keep coming up with all those ways of improving efficiency, and to be fair, in the last 30yrs they got it to be "good" but the actual % numbers are awful regardless.

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Re:In the US, it's cheaper to build and operate wind farms t... by rfrey on Sunday August 18, 2019 @09:20AM (#20729978)

Efficiencies might seem bad, but thermodynamics limits the efficiency of any heat engine (of which an ICE is one) according to the absolute temperature of the hot and cold side of an engine. This is called the "Carnot efficiency" and it's comparable to a no-friction mechanical system, or a no-resistance electrical circuit.

For an ICE, assuming combustion temperatures of 550K and assuming the radiator can cool the system to 50C, the Carnot efficiency is (1 - Tc/Th) = (1 - 333K/550K) = about 40%.

That's a hard theoretical limit that assumes all processes are reversible. Real engines have irreversible thermodynamic processes so the Carnot limit can never really be attained.

In other words, your complaint isn't with the engineers, it's with thermodynamics.

(note: ICE engines are modelled using the Otto cycle rather than the Carnot cycle, but that's a bit more complicated and leads to efficiencies that are even worse. The Carnot efficiency is an upper limit for all heat engines, including steam engines, Stirling engines, turbines, etc.)

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Re:In the US, it's cheaper to build and operate wind farms t... by Retric on Sunday August 18, 2019 @08:02PM (#20733769)

550k is a low combustion temperature. “Modern military jet engines, like the Snecma M88, can see turbine temperatures of 2,900 °F (1,590°C).” https://en.m.wikipedia.org/wiki/Turbine_blade

That’s like ~1850k assuming 2900F was rounded.

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Re:In the US, it's cheaper to build and operate wind farms t... by rfrey on Monday August 19, 2019 @09:18AM (#20737452)

Absolutely. But I read the comment as complaining about efficiencies of automobile engines, not modern military jet engines. The combustion temperature of gasoline is 553K.

https://hypertextbook.com/facts/2003/ShaniChristopher.shtml

https://www.quora.com/How-much-heat-does-it-take-for-gasolin...

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Re:In the US, it's cheaper to build and operate wind farms t... by Retric on Monday August 19, 2019 @11:27AM (#20738586)

Ignition temperature is just the point when something starts to burn, it has nothing to do with the temperature inside an engine after ignition.

https://www.quora.com/Which-engine-has-higher-temperatures-a...

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Re:In the US, it's cheaper to build and operate wind farms t... by raverbashing on Sunday August 18, 2019 @11:28AM (#20730751)

I am aware of the Carnot efficiency, my issue with the engineers is that they can't make big gains anymore, exactly because of the Carnot limit.

Best way of making a gasoline car (not the engine - the car) efficient is taking the throttle of the engine out and attaching a hybrid/regenerative generator/motor to it.

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Re:In the US, it's cheaper to build and operate wind farms t... by adrianN on Monday August 19, 2019 @04:50AM (#20736061)

The best way of making the car efficient is doing something about the fact that we use two tons of steel to move 100kg of human.

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Re:In the US, it's cheaper to build and operate wind farms t... by raverbashing on Monday August 19, 2019 @06:35AM (#20736570)

Yes, but that's a market problem ;)

Maybe the electric scooters/mopeds are the solution?

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Re:In the US, it's cheaper to build and operate wind farms t... by Retric on Sunday August 18, 2019 @12:12PM (#20731045)

Combined cycle thermal efficiency’s are breaking 60%. https://en.m.wikipedia.org/wiki/Combined_cycle_power_plant

But, for very long term storage efficiency is not that import. If you’re buying at an average of say 1c/kWh and selling at 20c/kWh in 6 months it’s mostly a question of what your storage costs per day as well as maximum output is.

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Re:In the US, it's cheaper to build and operate wind farms t... by Gibbon1 on Sunday August 18, 2019 @04:27PM (#20732596)

I first worked that out in response to a claim that solar thermal plants were better than PV because they can store energy as molten salt and produce power at night. What sinks that claim is solar is cheap enough that you could heat your salt with electricity from solar panels and be ahead.

At the point there is no need to use salt. You can use a referable electrically driven gas turbine and get about 70-80% round trip efficiency.

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Re:In the US, it's cheaper to build and operate wind farms t... by taneq on Sunday August 18, 2019 @08:26AM (#20729779)

Sure, but fuels are useful and if the power is effectively free, why not make them?

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