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Comment by Doches | Hacker News Reader

One piece of this really jumped out at me: the projection of overall energy demand to shrink from 2900 TWh to 900 TWh over the next 27 years. The article waives that away by pointing to efficiency gains from electrification and decarbonisation — but that’s just a stupendous change in consumption over a quite short period of time.

I would honestly like a deeper explanation of how electrification will produce such a wild decrease! That’s shrinking energy use by more than 2/3, and presumably after taking into account population/industry growth…? Or are the authors just wildly pessimistic (not…unmerited) about Britain’s trajectory over the next quarter-century? What am I missing here?

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From what I understand, these TWhs refer to total energy usage, not electricity usage.

If you replace a ICE by an BEV powered by solar cells, you actually reduce the total TWhs because of efficiecy:

- ICE: 6L of gasoline per 100km, that equals to about 60 KWh

- BEV: 17KWh for the same distance.

The same applies to heat-pumps and some industrial processes.

Correct, a lot of Mackay's estimates fail to account for the difference in delivered efficiency between electric solutions and their gas counterparts. For instance in his car section[1], he estimate you'd need to produce 40kwh to drive 50km. That may be close to the true energetic content of the gas burned, but you could drive that far on just 10kwh in a modern EV, meaning electrification dropped your gross energy needs by 75%.

[1] https://www.withouthotair.com/c3/page_29.shtml

He was aware of the benefits of EVs though, from a later chapter

> OK, the race is over, and I’ve announced two winners – public transport, and electric vehicles.

He was also very positive about heat pumps.

https://www.withouthotair.com/c20/page_131.shtml

> You’ve shown that electric cars are more energy-efficient than fossil cars. But are they better if our objective is to reduce CO2 emissions, and the electricity is still generated by fossil power- stations?

> This is quite an easy calculation to do. Assume the electric vehicle’s energy cost is 20 kWh(e) per 100 km. (I think 15 kWh(e) per 100 km is perfectly possible, but let’s play sceptical in this calculation.) If grid electricity has a carbon footprint of 500 g per kWh(e) then the effective emissions of this vehicle are 100 g CO2 per km, which is as good as the best fossil cars (figure 20.9). So I conclude that switching to electric cars is already a good idea, even before we green our electricity supply.

And that misses the petrol station thing. Stocking the station tanks (and that supply chain), staffing, etc, that doesn’t cost zero.

Refining oil is a power-intensive process, requiring 5 kWH of energy per gallon of gas. This is why talks about EVs requiring so much more electrical power generation are vastly overblown - they don't account for the power consumed to pump, refine, transport, and distribute the petro products needed for ICE vehicles.

True, but neither does maintaining the grid

But we’re already maintaining the grid. Growing it to handle the new workload would require a fraction greater maintenance workload which would be tiny in comparison to maintaining the entire parallel infrastructure needed to get oil from a Saudi Arabia desert to a car filling up at a gas station in the middle of Wichita.

Marginally and variable costs it does though. A 100% capacity charging station has few variable costs compared to gasoline delivery; the grid interconnect and charging cables are equivalent to filler and tank safety inspection, not daily or weekly deliveries of fuel by pipeline + truck.

I'm sure he was. It's easy for us to see 15 years later that the combination of EVs + solar/wind has a huge efficiency gain because you can get to avoid internal combustion altogether, but EVs were nascent enough in 2008 for that to not be as clear, so those assumptions didn't make it into his calculations.

This is a bit of an apples-to-oranges comparison. If you consider the energetic content of the gas burned in a car, then you need to measure the same thing for the EV - large power plants are a bit more efficient than car engines, but unavoidably far from 100%; in order to get 10kwh of electricity to an EV the current grid would burn gas or coal with an energetic content of probably 25kwh or so.

So electrification alone can't bring so large reductions in total energy consumption - it is simply one of the prerequisites for that, and it also needs to be accompanied with large scale build-up of non-fossil electricity, of renewables or nuclear.

Mackay's book, and this discussion, are in the context of a hypothetical future where Britain is powered predominantly by solar and wind. It's not even that hypothetical anymore, because as you can see from this dashboard(https://www.energydashboard.co.uk/live) the UK is currently getting 75% of its electricity from renewable and low carbon sources. So even today, driving 50km there only requires 15kwh of gross energy.

But when you're using solar to generate the energy, what's the equivalent of burning? I'd argue that it's just "whatever the panel produces". So, if you have some panels producing 1 KWh, and you need that KWh for your car, the relevant efficiency here is transport efficiency.

> equivalent of burning

Probably storing.

Give it 50 years and we're going to be facing some other unexpected global disaster from unchecked battery proliferation.

Hopefully it's less dire than climate change though.

Since we currently aren't covering the existing demand for electricity with reneweables, the "marginal kwh" of electrifying some car comes from fossil fuels, not solar.

Those are two separate things - electrifying some transportation need gets us X benefit, and converting some electric generation from fossil fuels to solar gets Y benefit, but the former doesn't automagically create the latter.

1) There is no reason to attribute all of the carbon intensity to the last use to be added. It is far more accurate to estimate the carbon intensity of something by the blended production mix at its time of use. Fossil fuel plants are often kept online for factors beyond the need for additional capacity at a certain time.

2) You are assuming there is no curtailment or rejection of wind, solar, and nuclear, which is categorically false. This is why there are time-of-day rates that vary so drastically. There are large amounts of renewable/low-carbon energy that would otherwise be wasted in pretty much every geography.

You could apply that to everything.

If I turn on (or keep on) my light when usage isn't completely covered by renewables, should that be calculated as using all fossil fuels?

The logical extension is that everyone should calculate the carbon intensity as a binary choice which is obviously wrong.

The only reasonable way to go is to look at the actual carbon intensity average.

  > If you consider the energetic content of the gas burned in a car, then you need to measure the same thing for the EV

True, but the resulting numerical "hit" for EVs is a lot smaller than for ICE vehicles.

This is largely because

1.) big stationary heat engines are much more efficient than small weight-optimized mobile ones, and

2.) the electricity grid also has some renewable energy mixed in, so a growing fraction of the electricity supply doesn't even need an (energetically imperfect) heat engine.

If you want to include production of electricity you also need to include refining and distribution of gas. So many exclude that and make calculations as if the gas get to the gas station by magic

That’s not true, because the point of comparison is already the _output_ of the electricity generation in TWh. Once the energy is available in the grid you can put it in your EV at almost 1:1.

Additionally, the parent overlooks that while a lower number is estimated, they compare against a hypothetical 2000+ TWh number instead of the tightest 900 TWh estimate.

Probably more significantly: about 30-40% of UK energy use is gas central heating which is 90-95% efficient. Electric heat pumps (beginning to be installed in numbers the U.K.) are 300-400% efficient.

That’s nearly half the saving

Industrial heating is also a big factor. That too is dependent on gas right now. A lot of that could shift to electrical in the next few decades. And the rest might transition to hydrogen.

But that doesn't reduce consumption of electricity. Your gasoline cars don't consume any, and your EVs consume a lot.

Presently running my EV just about 100% on rooftop solar energy, which is possible about 3/5ths of year in my situation. Melbourne, AUS, admittedly, but still.

Fuel delivery still requires a crap load of energy, some of it in the form of electricity - even just running the pumps 24x7 - but there's so many elements in that value chain it could fill volumes. There's far fewer even in the dirtiest of EV charging scenarios.

Again, the numbers _do not refer to consumption of electricity_, they refer to consumption of energy.

Increasing electricity consumption while lowering overall energy consumption is the point.

There is no such projection, it seems you misread something.

The O’Callaghan et al. paper (in the Blog post here the related figure is fig 1) says that current (2023) demand is 1500TWh and current supply is 2885 TWh. There are different projections for total demand in 2050 (note all of them project a reduction of demand, due to efficiency gains), one of these is the national grid FES which projects 900 TWh. Importantly the O'Callaghan paper opts to be conservative and choose to use the current demand as the demand for 2050. This is conservative, because it is higher than all projections which all assume that we get demand reduction from efficiency gains.

Take a look at the amount of rejected energy we waste by using for example heat engines today. Electrical engines and heat pumps vastly reduce those losses.

https://flowcharts.llnl.gov/

IT looks like the 900 number is discussed in chapter 3 of this document [1].

As far as I can tell the current usage of 1200 TWh include electricity and combustible chimerical energy of gas. Electricity use is ~300 Twh, and Gas usage is ~800 Twh.

The proposal is that gas heating would be entirely replaced with heat pumps and most gas generation would be replaced with modular nuclear reactors and offshore wind.

The numbers are a little misleading because of the way gas and electricity are summed to get the top level numbers. A TWh of gas consumption is not the same as a TWh of electricity consumption. In thier model, 50 TWh of electricity can replace 400 TWh of gas. The challenge with this approach is that it is not show what is going on with user consumption. Are they getting more, less, or the same thermodynamic work done?

https://www.nationalgrid.com/document/138976/download#:~:tex....

Burning fuel to generate electricity creates waste heat that siphons off most of the energy. By the time electricity reaches your outlet, around two-thirds of the original energy has been lost in the process: https://yaleclimateconnections.org/2022/10/energy-loss-is-si...

With Solar and Wind, there isn't any wasted heat.

I want to add that Britain's energy demand has already fallen by one quarter in the last 15 years even without the efficiency gains from large scale electrification, so a 2/3 reduction (which to stress again is not what the paper assumes) is not so outrageous.

Some of that is due to efficiency gains (good). But some is also due to deindustrialization and increased imports of energy intensive products (bad). We have to look at full lifecycle global CO2 emissions in order to perform a valid analysis of any changes.

Depends what you care about. MacKay's claim was specifically that the UK couldn't be powered this way (which appears to be falsified); if the manufacturing all ends up in China, which has the Gobi desert and is closer to the equator, and has the Three Gorges Dam and the will to build it, I don't even have to run the numbers to know they can be completely green.

China isn't even remotely "green". Most of the official statistics coming out of there are highly manipulated. In particular they haven't built even a fraction of the storage capacity that would be needed to keep their factories running when the sun isn't shining, nor are they likely to do so in the next few decades.

China is building multiple 1000km+ HVAC transmission lines which gives climatic diversity (and power source diversity: wind, solar and three gorges).

That removes the need for storage (and is what every other country should be doing as well).

"is/is not" != "can/cannot be".

MacKay's work (and the update under discussion) about the UK, and also my claim about China, is about the latter.

Lots of things could happen in the sense that they don't violate the laws of physics. But your claim about China isn't grounded in any sort of economic or political reality. The demographic issues alone make a total green energy transformation impossible.

Why on earth would demographics make the slightest difference in either direction?

Because that level of industrial transformation requires huge labor and capital resources that China simply doesn't have. The CCP cadres have been reporting exaggerated numbers up the chain for years in order to keep their jobs so any metrics coming out of the central government are basically junk.

https://youtu.be/kBMSZ7v3KxQ?si=ZxlQlOHc6r6tj7n7

We know they've got the capacity for the required level of transformation just by looking at the things they export to us, along with satellite pictures[0] of their growing power sources (and indeed all other infrastructure) of all types.

[0] Well, remote sensing in general. You can argue if a map at specific spectral lines to detect industrial byproducts is a picture or a graph.

This is the crux of it. Yes, we've reduced demand from electrical appliances, an made more efficient cars. But we've also closed all of our steel mills, aluminium smelters and other heavy industry. We still use those products, but the energy intensive processes are done elsewhere.

The UK "industrial" energy consumption today is 30% of what it was in 1970.

https://assets.publishing.service.gov.uk/media/62334e14d3bf7...

In the future post-fossil fuel, solar powered age, that was going to happen anyway.

This is a long term problem Europe faces: with solar projected to dominate world energy supply (if historical experience rates continue), Europe will be an energy ghetto. Energy intensive industry will move elsewhere. Going nuclear cannot save them, since their nuclear will be competing against world best case solar in sunnier places.

> the projection of overall energy demand to shrink from 2900 TWh to 900 TWh over the next 27 years

To be clear, today's demand isn't 2900 TWh. It's 1599 TWh. And none of the people claiming Britain can be powered via renewable power are using the 900 TWh figure.

Just noting for people who haven't read the article because this comment wasn't clear to me:

  Today's demand: 1599 TWh
  UK’s Department for Industrial Strategy forecast demand for 2050: 1250 TWh
  UK National Grid FES forecast demand for 2050: 900 TWh
  MacKay’s forecast demand for 2050: 2900 TWh (I think this is what this comment is referring to)
  MacKay’s 2008 forecast renewable production for 2050: 1500 TWh
  O’Callaghan (new, 2023 report) forecast demand for 2050: 1500 TWh
  O’Callaghan (new, 2023 report) forecast renewable production for 2050:  2895 TWh

The difference is mostly about pricing of renewables radically dropping since 2008, and the likelihood of floating offshore wind producing large amounts of supply.

[1] https://www.statista.com/statistics/322874/electricity-consu...

I would bet that electricity demand goes up, not down. When a good becomes cheaper/more efficient, demand increases.

1. They're talking about all energy (cars, heat, and electricity), not just electricity.

2. Demand is up in this scenario, not supply, because of all the things being electrified.

If prices go down this makes a lot of sense.

But there isn't any real reason to think this is implied under a "high renewable" scenario.

In-fact, some of efficiency gains are probably driven by increased costs.

But the change is not a 1:1 linear ratio. Demand increases, but only if there is pain that more could use. Once a room is bright enough you won't add more light.

Sure, but you may not be as diligent turning off the lights.

Exactly, but the improved efficiency is more than the loss from leaving it on.

> Exactly, but the improved efficiency is more than the loss from leaving it on.

The improved efficiency needs to be more than the drop in marginal cost which is what governs demand, nothing to do with how much more electricity you use today. And even then, that relationship isn't linear because a 30% reduction in cost can drive a 60% increase in demand because that reduction puts it in a new price bracket where a lot more people can afford it (since wealth is non-linear). This stuff is super non trivial and has all sorts of higher order effects.

Sometimes others there is no change. HVAC systems won't change demand at all when upgraded to more efficiency .

It usually isn't. Jevons Paradox.

The better question is why do they think more efficiency will lead to lower use rather than higher consumption? I know, if the price stays the same per unit of energy and i stop spendjng so much because of efficiency gains, i have a ton of other stuff i would love to do that consumes energy so my decrease in usage would be tiny. What will decrease my usage is price increases, which can only go so far as taxes to capture proposed externalities before i revolt and elect someone who will axe the tax (as is about to happen in canada).

Energy use per capita has already been falling for two decades in the US: https://www.npr.org/sections/money/2013/04/10/176801719/two-...

You are making the assumption there won’t be some new technology that gobbles up significant energy. At one point an American’s electrical consumption might have been home lighting and a radio. Then it jumped by an order of magnitude with the refrigerator and air conditioner.

Energy costs are so high in the modern age relative to how dirt cheap it was pre-OPEC crisis, that any sort of significant energy consumption would be a barrier to significant adoption. Your average Joe cannot afford to mine Bitcoin, for example.

If anything we have mostly seen massive improvements in energy efficiency in the last two decades, with appliances, the switch to LED lighting from incandescent, heat pumps vs other heating/air technology, etc. What new technologies have shown up get quickly innovated in the name of energy efficiency.

Most of the examples I can think of with that would not be localized.

For example, if we need massively more computing for an AI breakthrough, there's nothing requiring that to be localized. Similarly for production of any commodity that can be shipped.

Thats not really what that chart looks like to me, or at least the effect is very moderate. The big drops correspond to economic shocks. Even if i ignore that the chart is topping at roughly 350 in 1975 and bottoming around 310 in what i assume is 2023, which makes it what? A 0.22% annual decrease?

> I know, if the price stays the same per unit of energy and i stop spendjng so much because of efficiency gains, i have a ton of other stuff i would love to do that consumes energy so my decrease in usage would be tiny.

Do you, though? What? I'm not sure how typical this is. Like, if you replace your creaky old gas central heating with proper insulation and a ground to air heat pump, you're going to be saving a _lot_ of energy if it's a big house. What would you use this extra energy 'budget' on?

As an aside re: Canadian politics. New Governments don't get elected, old ones are voted out of office. The shelf life is generally 10-15 years and this government has gotten stale. It just so happens the party in position to replace them plans to remove the carbon tax (which hasn't been implemented in any meaningful way) as part of their platform

Thats true but a misinterpretation of the data in my opinion. Old ones are voted out because their policies mismatch the current pain points, which is definitely happening here. Libs were elected on a luxury beliefs platform that isn't compatible with the current state of the economy/interest rate regime/inflation. Enough people have finally realized this to grow disillusioned and change voting patterns.that the libs appear to be a bunch of kleptos and/or incompetent and/or corrupt is speeding up that realization.

If the libs had kept the klepto stuff to a less obvious level and adapted the binding parts of their luxury beliefs platform they probably would still be polling a majority and could have kept this going for quite a while longer.

I think youve misread it. 1600TWh is the demand today. The 2900 figure is potential supply of wind and solar.

Could you cite where you found those numbers? I can't find either of them:

The submission (blog post) doesn't mention the number 900 at all; the paper which the submission is about only mentions 900 in a footnote saying "Total European [energy] supply was 22,900 TWh (IEA, 2022)."; the summary pdf of said paper never mentions 900 or 600.

Figures in the paper ending in 600 occur in a few spots, but nowhere 1600. There is 21'600 TWh/year (total European energy supply, page 8), 16'600 TWh/year (idem), 10'600 TWh/year (prior studies' estimates of UK wind resources), and 2'600 km² (land occupied by buildings).

But maybe I shouldn't be drawing conclusions based on trying to search character sequences in a semi-picture format...

> They estimate that it could produce 2,895 TWh of electricity each year from solar and wind. That’s almost double its estimate for final energy demand in 2050. See the chart below. [...] We can see this when we look at other estimates of energy demand from the literature. The National Grid FES projects that Britain will need just 900 TWh in 2050. [...] Total final energy demand today is 1599 TWh.

It's right under the first main heading. Just above and below the first picture. Searching for 900 in the post took me right to it. I have no idea how you missed it.

She explains it here in this post https://www.sustainabilitybynumbers.com/p/electrification-en....

Many comments try to allude to it. It is important what we are talking about- Primary energy, Secondary energy, Final energy or the Useful energy.

The embedded links go in further details.

Electricity demand has fallen by ~10% over the past decade while we've been introducing EVs and heat pumps and stuff.

These things are all more efficient than the hydrocarbon equivalents, further depending on the measure, if you count the gas input energy in to a gas plant, a renewable generator is much more efficient too.

So I think it's possible, although the figure ends up somewhat misleading without a lot of context.

In the past, customers were encouraged to be very inefficient with their electricity usage. Rather than fit efficient insulation, high consumption was tolerated for years to come.

And thanks to the "Base Load" myth of coal based generators, people were encouraged to use heat banks and storage HWS which loaded the system during the night.

But this could only be done by offering cheap "night rate" electricity.

In the future, our consumption must be focused on day-time peaks, as well as much better insulation, and the use of heat-pumps. And of course a steep increase in electricity tariffs will greatly encourage this.

In the future, companies which operate 24 Hrs without thought to electrical cost, will focus much more on efficiency, and even begin to shut down operations at night.

In many countries (eg Australia) there has already been a huge increase in domestic solar and battery installations.

This change will be driven by unavoidable price rises, and the recognition of our profligate wastage in the past..

Electrification doesn't cause such a decrease. Fixing your projection so it's not anymore a "we can't do anything, we must keep investing in BP" piece into a realistic one is what reduces it.

Honestly, anybody claiming in 2008 that PVs are too expensive so we should not invest on them is safe to ignore.

That's close to the time frame when I realized solar was going to win just based on pure business accounting.

Thing to consider the ultimate price of a manufactured good tends to track production volume, device complexity, and energy required to produce including raw material.

Solar panels require complex machines to produce but are themselves simple, the volume is high at scale, and energy requirements are low. That points to something where the price is close to the energy and material costs.

> energy requirements are low

They can surely become low, but currently they are not. The EROEI of PV panels is barely on the region where it stops being one of the largest factors in its cost.

But yeah, PV has space to improve a by a few orders of magnitude more.

> claiming in 2008 that PVs are too expensive

You're misrepresenting the analysis.

In the 15 years since, public support for PV flipped from con to pro, and we've learned that much less land must be allocated to just PV.

As noted in the OC, Mackay's contribution was methodological. It easily accommodates different assumptions and updated numbers. O'Callaghan et al did just that. Yielding a new conclusion.

ICE vehicles turn less than 35% of their energy consumption into productive work. The rest is waste heat. That's the main reason transitioning to pure EVs must happen.

That's an inherent limitation of heat engines - if you burn the same thing in a power plant, then you could get 45% instead of 35%, but you can't possibly convert, say, 80% of burned fossil fuel into productive work.

> if you burn the same thing in a power plant, then you could get 45% instead of 35%, but you can't possibly convert, say, 80% of burned fossil fuel into productive work.

Not 80%, but combined cycle gas turbines regularly achieve up to 60% steady state efficiency.

There is research into ammonia fueled turbines that supposedly achieve even higher efficiency.

And Combined Heat and Power plants get up to 75% by using some of the heat.

I really don’t see the point of that calculation. It’s like saying that the wind turbine only captures 5% (number made up) of the energy of the wind going through it.

Then you didn't read the article. The whole point is can the UK meet all of its energy needs with solar and wind. That includes transportation energy. The comment I was responding to was wondering how to reduce the energy needs. A big part of it is by drastically increasing the efficiency of transportation by moving from ICE to BEV.

If you had to pay for the wind you might be very interested in that ratio.

Not if there is nothing I can do about this ratio. It's a theoretical unaccessible energy that doesn't mean anything.

It seems sort of nonsensical to project electric usage decline as we move from ICE to EV and from oil/gas heat to heat pump.

This is final energy demand and thus presumably includes energy used for heating and transportation that's currently provided via fossil fuels. In fact, that's the point: electrical motors and heat pumps are more efficient, and the final energy demand is reduced. In other words, demand for electricity goes up, total energy demand goes down.

That makes more sense if we are talking total energy demand.

Yeah - the original point was about a reduction in total energy demand, not electricity demand.

The ballpark number for EVs is that they are 4x more efficient than ICE cars AIUI.

Harder to ball park heat pumps because it depends on the climate, but 4x is probably a reasonable guesstimate. At worse it's equal to burning things for heating (when it's too cold outside to use heat pumps, not sure that really happens in Britain), at best it's... some ridiculous factor better (when it's practically the same temperature outside and inside).

It's a decline in overall energy, presumably not in electricity.

I could believe some reduction if there were massive efficiency increases (e.g. replacing resistive heating with heat pumps) but that seems impossible on that scale unless they’re also forecasting entire industries leaving the country.

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