Typical power stations (whether fueld by renewables or not) have efficiencies considerably less than 50% (the examples in this article give 40% efficiency for coal, 48% for nuclear, and 33% for geothermal).
Photovoltaics (not being Carnot-cycle heat engines) aren't subject to these specific limitations, but they have their own problems. Typical efficiencies for current mass-production models are around 20%, while "lab curiosity"-level cells still haven't broken 50%.
Note that this is just the generating side. There are also similar waste heat losses on the consumption side (for example, charging and discharging batteries is anything but 100% efficient, as anyone who's actually tried to use a modern laptop on his lap can attest).
The difference is, that 80% doesn't show up on anyone's "books." For coal, you actually need to go dig that 60% out of the ground and burn it, and it still emits a bunch of CO2.
For a fuller articulation of the point HN user thelastgallon is making, see this link:
> The difference is, that 80% doesn't show up on anyone's "books."
Well, no. You still have to pay the amortized cost of the installation and real estate, the salaries of the employees, and many other things, all of which would be less if the efficiency were higher than 20%. For example, if the photovoltaics were 40% efficient (the same as coal), you'd need only half the real estate, half the semiconductor-grade silicon, and likely half the cost of many maintenance activities, none of which are free.
I didn't say they were free, I said that the energy doesn't show up on anyone's (energy) books. You know which books I mean: they're the ones where companies & countries report their energy reserves, the amount mined/burned/imported/exported, new discoveries this year, etc etc.
The reason this matters is because there's a lazy temptation to run the Electrification Calculation merely by looking up the amount of primary fossil energy burned annually, then assuming 100% of this must be replaced by solar/wind/whatever. However this simplistic calculation will over-estimate the amount of renewable energy needed by a factor of roughly 3x.
>This site doesn't even mention solar or the efficiency thereof.
I fear you only want to 'win the debate' (vs reading for comprehension), but...
The entire thesis of the article is how mass renewable electrification enjoys large system efficiency gains over fossil fuels. It's pretty evident how solar is a critical enabler of mass renewable electrification.
My reading comprehension is just fine. You were arguing that coal had to be "dug out of the ground", unlike photovoltaic cells which are apparently dropped off on your doorstep for free by the Silicon Fairy or something.
There's the reading comprehension. Again, nobody is saying solar panels are free, and I'm not sure where you got the idea.
I'm saying that when states and corporations do their energy reporting, there's no need to report the non-absorbed ('waste') energy from PV. Sunlight striking the ground (and whether it's utilized in a way we appreciate, versus 'just' powering the weather and the water cycle) is not something we include in those numbers.
Heck, maybe we should make a home for your PV 'waste' energy, a new energy statistic that does account for all sunlight striking the Earth. So if you cut down vegetation to make a parking lot, it makes your country's energy numbers get worse. Neat! Maybe that would be useful as an additional metric, but it's far from what we're trying to measure with our existing energy reporting policies. Our existing policies emphasize the (much larger) problems of greenhouse gas emissions and local pollution impacts.
Anyway I think the point has been adequately made, cheers.
Renewables are still subject to the laws of thermodynamics and other laws of physics.
https://en.wikipedia.org/wiki/Heat_engine#Efficiency
Typical power stations (whether fueld by renewables or not) have efficiencies considerably less than 50% (the examples in this article give 40% efficiency for coal, 48% for nuclear, and 33% for geothermal).
Photovoltaics (not being Carnot-cycle heat engines) aren't subject to these specific limitations, but they have their own problems. Typical efficiencies for current mass-production models are around 20%, while "lab curiosity"-level cells still haven't broken 50%.
Note that this is just the generating side. There are also similar waste heat losses on the consumption side (for example, charging and discharging batteries is anything but 100% efficient, as anyone who's actually tried to use a modern laptop on his lap can attest).