[binoct]

Primary energy sources are what they are, both your comment and the linked article seem to imply discussing them should lead to a deserved punch in the face. Can you help me understand why?

As far as I can tell, your link argues that if we overcome all the practical challenges (politics, resources, financing, technical innovation) and go all-electric for global energy, we only need ~1/3 as much input energy potential as we use today for the same useful work. That’s useful, but the hard part lies in those practical challenges. And the primary sources of global human energy use are a long way away from that goal.

So should we strive to get there? Sure. Should we be tactical about how? Yes. And the link seems to argue that as well. But is it reasonable to hit our 2050 goals based on the current global fossil fuel usage? Not really. So I’m really missing how this refutes Smil’s article, and why “primary energy” is such a stupid thing.

[_aavaa_]

The problem with it is that it makes it easy to make bad faith arguments for why we can’t or shouldn’t transition (kinda like is being done here).

Take for example paragraphs like:

> Primary electricity (hydro, nuclear, wind, solar, and a small contribution by geothermal plants) accounted for no more than about 18% of the world’s primary energy consumption, which means that fossil fuels still provided about 82% of the world’s primary energy supply in 2022.

Are used as justification for why green green energy is a scam, it can’t be done, or it’s too expensive, etc., etc. after all 82% of primary energy is still from fossil fuels.

Except we don’t have to replace 82%, since 2/3rds of that is wasted. Of 100 kWh we’re already done 12 kWh and only need to add 27 (NOT 82) more kWh of electricity to replace all the fossil fuel usage. And that’s before talking about any efficiency gains (e.g heat pumps with COP >4).

[binoct]

Ah, seems like I was missing some context where the fossil fuel and anti-renewable folks have been using the term in arguments against trying to change.

I’m not sure of Smil’s politics but to be fair, there’s nothing in that quote that is inherently misleading. I can see through how others could spin it, and I’ll be more careful knowing the term has some politics behind it now. To me his argument in the article is that it’s not practical to expect a transition in a 25-year timescale, not that it’s impossible or not worth working on.

Heat pumps are a good example where the practice has been a lot harder than we might hope. Sure COP > 4 for heating is great, but the units are very expensive today, and in most of the US and Europe with sub-zero winter temps operate with much worse efficiencies, making them significantly more expensive to operate. I’m sure with effort those issues will improve, and major policy shifts can help mitigate some of the costs. But especially without a strong will today those changes are practically too far off for the 2050 target.

[_aavaa_]

> there’s nothing in that quote that is inherently misleading

The discussion of the issue in terms of primary energy is the very thing that's inherently misleading. To move away from fossil fuels we do not have to replace the primary energy, we have to replace the useful energy that comes out the other side. From the Sankey diagram in the article I linked [0], 67.5 units of energy are not useful energy.

To put it to an extreme, instead of 67.5 units beings wastes, it could be 100 billion units for 32.5 units of useful energy produces. Focusing on the 100 billion is inherently misleading since they are irrelevant when the replacement technology basically creates the useful energy with over 100% efficiency at times.

Heat pumps. Yes their COP is lower during cold winters, but that brings in 2 discussions.

1) any COP value above 1 means that we'll need less primary energy than when buying something, and even in cold weather they manage a COP above that [1].

2) Lower COPs will cost you more, depending on what your natural gas prices are like due to any crazed lunatics invading their neighbours. Which conincidentally is only what pushes electricity prices up in many places that use natural gas for electricity (even just peak demand).

The capital cost difference also depends drastically on situation. Many climates need both heating and cooling, so the price of heat pump versus furnace + AC unit is much smaller than heat pump versus furnace.

> But especially without a strong will today those changes are practically too far off for the 2050 target.

I agree, and even replacing the 1/3rd of the primary energy will be a tough challenge. But Vaclav continual framing in terms of primary energy is actively used to push inaction. His critics have been vocal about this point (and others) for a while, he should know better by now.

[0]: https://spitfireresearch.com/wp-content/uploads/2024/06/LLNL...

[1]: https://www.sciencedirect.com/science/article/pii/S254243512...

[binoct]

Thanks, you have helped at least me think a bit differently about this. I still believe primary energy is a valid way to look at the problem, but see more clearly how easily it can lead an uninformed audience to a bad conclusion.

And on heat pumps - it’s sad to reflect that even if we replaced all heating, it’s still only a couple % of the total rejected heat. There are few easy wins in this game, just many different ways we need to chip away at it.

[_aavaa_]

I'm glad it was helpful.

> it’s sad to reflect that even if we replaced all heating, it’s still only a couple % of the total rejected heat.

It's actually not as bad as it looks.

Even if the home heating is not the biggest contributor from that chart, it is still a worthwhile target. Though EVs are likely a more impactful choice.

One thing not captured by that chart are the 2nd order effects of either heat pump or EV switching. Part of what makes switching economically unattractive (aside from allowing the fossil fuel options to pollute for free) are the economies of scale present for fossil fuels. However, those same economies of scale can easily flip to diseconmics of scale as customers switch away. Every ICE car replaced by an EV makes gasoline and diesel more expensive, the same thing for heat pumps and natural gas andheating oil.

So for natural gas, removing the stream going to residential, significantly impacts the economic calculation for commercial and industrial uses.

For gasoline and diesel, the impact as even more serious. Out of every barrel of crude oil 70% gets turned into gasoline/diesel [0]. The unit economics there are going to be even worse as gasoline demand continues to drop.

[0]: https://www.eia.gov/tools/faqs/faq.php?id=327&t=9

[measurablefunc]

> the replacement technology basically creates the useful energy with over 100% efficiency

I think you're confused. There is no way to avoid the laws of thermodynamics so where are you getting more than 100% efficiency?

[_aavaa_]

Efficiency is not the correct word here.

A gas furnace converts 1 J of chemical potential energy (higher heating value for natural gas) into essentially 1 J of internal energy in the air (raising it’s temperature).

A heat pump can take 1 J of electricity and move (realistically) up to 5 J of internal energy from A to B.

A layman description (if not actually accurate) is that while a gas furnace (or electric resistive heating) can be 100% efficient, a heat pump can be 500% efficient.

[measurablefunc]

Can you point me to the actual literature on the mechanics of heat pumps b/c I don't think you're explaining properly what's going on. If you can get 5J out of 1J then you have a perpetual motion machine & those are physically & logically impossible (assuming physically relevant axioms).