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There seem to be two broad approaches to the climate crisis.

One centres around technological progress, where efficiencies, a gradual switch to renewables, and CCS enable a broadly similar model of economic growth and consumption to continue while keeping below some threshold (it's not going to be 1.5°C!) of warming.

The other counsels radical cultural and lifestyle changes towards greatly decreased consumption, implying a similarly radical shift away from perpetual-growth economics, and probably radical changes to politics and much else besides.

In reality of course we may need large parts of both; and we seem unlikely to get much of either.

My worry about the first approach is that all these things require energy from somewhere. Yes, we might be able to move to electric cars, but can we do this and cover the increased electricity demand by renewables? My question is, how feasible is this model in terms of total energy demand? Assume:

  • aviation, land transport, manufacturing and other industries, space and water heating are electrified or moved to hydrogen or synthetic fuels using best available renewable technology
  • electricity generation is moved entirely to renewables
  • CCS is used to offset "unavoidable" CO2 emissions (e.g. from livestock and cement production). I do not consider tree planting (highly desirable though it is) to be a sufficiently rapid or reliable method of sequestering carbon.

I'm particularly interested in the UK, but any country or region (or indeed a global answer) would be great. An answer might look like (rough order of magnitude) "total renewable energy potential in the UK is X PWh/yr; current total energy consumption is Y; CCS might use Z kWh per kg CO2 so storage of enough carbon to offset cement production and agriculture would be A TWh/yr; so there is/isn't enough energy production capacity to do this". Or a frame challenge!

  • you can check this paper (Jacobson et al. 2019) on transition and grid stability: cell.com/one-earth/pdf/S2590-3322(19)30225-8.pdf – Silmathoron Feb 4 at 13:02
  • I think the problem is that solar, wind, and hydro power require land area and there is a limited amount of land area that each region will give-up to power production. Fossil-fuel powerplants and nuclear energy use a relatively small amount of land area. Now carbon-capture at fossil-fuel powerplants can be used to make plastic for use in long-term building materials. But such a system would be a master-plan and require legislation. – S Spring Feb 4 at 13:20
  • @SSpring yes, I assume land area is likely to be the limiting factor. That may be the question - how much land area is required to power all of the UK's transport, heating, manufacturing etc? – aucuparia Feb 4 at 13:43
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tldr: yes, with sufficient political will, an incremental approach is sufficient - we could decarbonise our energy consumption in 20 years.

There are still a lot of unknowns (like just what we do about long-haul aviation, intercontinental shipping, cement production). However, some things we can be sure about, and one of them is that there's way more than enough space to provide more energy than we could possibly need for the forseeable future.

I've posted on my own blog about the space requirements for 100% renewables.

But let's do a quick back-of-envelope calculation for the UK, right here.

As you can find in DUKES 2019 - the UK Digest of Energy Statistics - UK final energy demand (all energy, not just electricity) is around 180 GW.

UK land is about 240,000 km², and UK seas are about 760,000 km².

Wind tends to yield around 2.5 MW/km² average energy - figures are my own calculation, presented as part of my calculation of UK offshore wind capacity factors. And that's in line with what others have calculated.

So, even without any energy efficiency at all, 10% of UK seas (and no land use for the turbines!) would provide equivalent average energy to UK current final energy demand (10% x 760,000 km² x 2.5 MW/km² = 190,000 GW = 190 GW). Now, that's not a scenario I'm proposing - it would be silly to do without hydro, solar or biomass; and lots of additional measures would be needed to ensure demand meets supply in real time; - it's just to establish that there's no space constraint on renewable energy supply.

But when we electrify car transport, we improve efficiency radically, because battery EVs are about 4 times as efficient as the infernal combustion engine. So car energy demand goes from about 35 GW to about 9 GW. And if we electrify heating with heat pumps, with an average COP of 2.5, then domestic heating demand goes from about 40 GW to about 16 GW, very roughly speaking. So there's lots of quite big energy savings to be made.

Now, how long might it take to build all this? Well, if we were talking about 200 GW of offshore wind capacity, that would need a build rate of about 10 GW of new capacity per year. Currently build rate is about 1-2 GW per year, and so although it's too little at the moment, it's really not a huge stretch to get to where we need to - it's less than an order of magnitude increase.

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  • Each coastal area is going to have limits about taking away of navigation routes: en.wikipedia.org/wiki/Wind_power_in_the_United_Kingdom#/media/… . Orsted predicts wind power reaching 50% of UK electricity usage but the UK is a specific case with no continental interior. en.wikipedia.org/wiki/Wind_power_in_the_United_Kingdom – S Spring Feb 11 at 20:32
  • @SSpring while that's true, it doesn't change anything - shipping lanes are tiny compared to the available seas. – 410 gone Feb 12 at 7:55
  • Routes have long approaches and maneuvering area is required. Also, there are issues of coastal access. Allowed locations of offshore wind farms are going to be very thoughtful designs. – S Spring Feb 12 at 15:25
  • @SSpring I recommend a look at the German Bight on the map at 4coffshore.com/offshorewind for an idea of how little space the shipping needs, relative to the space available – 410 gone Feb 13 at 14:18
  • There's also near-shore fishing and boating coastal access. But I'm just saying that positioning of offshore wind farms is thoughtful design. – S Spring Feb 13 at 20:05
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This Zero Carbon Britain report gives a detailed answer to your question. Their plan sees emissions being reduced to 8% of the current levels, and the rest being balanced by carbon capture. This requires, they suggest, setting aside around one third of Britain's land area for carbon capture and one sixth for fuel (bio-fuels ... land area for solar isn't in their summary). They plan for a significant reduction in meat consumption to make this change in land use possible.

They are also planning for a reduction in energy use through switching to public transport and improving the quality of housing.

In short: zero carbon Britain is possible, but requires some significant life-style changes.

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