> Turbines have gone from 1-2MW to 10-16MW

Okay, but GP's point was that these bigger turbines need to be spaced further apart instead, so we can place fewer of them. That we could build bigger turbines was not in question I think. Do you happen to know whether the MW per km² increased more than the 30% expected amount that GP cited?

And regarding doing things between the turbines, I wasn't "awake" yet in 2006 so I don't remember how it was then, but were they ever placed so close together that you couldn't have farmland in between turbines? The problem seems to be that people don't want to live near them and find nature filled with wind turbines ugly, not so much that you can't do anything else in between.

(Just to note, I don't find them that ugly (even if, of course, nature would be prettier without them... but that's not an option) and I also didn't find them to be very loud when I visited some nearby wind turbines. Perhaps it's different at night when it's all quiet, but personally I don't think I'd mind living next to one. The blades are a bit scary though, I can't help but imagine the consequences if one of them lets loose... but that's like being afraid of air travel I guess.)

> Okay, but GP's point was that these bigger turbines need to be spaced further apart instead, so we can place fewer of them.

What will be a problem if our energy consumption increases by an order of magnitude or two, and we take all of it from the wind. Currently, the entire question is about financial ROI.

> but were they ever placed so close together that you couldn't have farmland in between turbines?

Not since the modern turbines were invented. The first ones were placed in somewhat compact lines, with enough spacing between the turbine lines that you could raise a few lines of any crop. (The lines can't be too close anyway, as that would reduce the turbine efficiency and harm financial ROI.)

But why is it important to optimise MW per km2? Seems like premature optimization of something that is not the bottleneck.

The goal of the book is not to find quick wins in reducing CO2 output, the goal is to give a complete overview over what is necessary to achieve carbon neutrality. And MW/km2 might be a bottleneck if we're to replace all oil & gas with electric power. If you read the book you can actually see what percentage of the seas around the UK would have to be fully covered, to achieve carbon neutrality. If that number really is outdated by an order of magnitude, perhaps MW/km2 is not a bottleneck.

Thinking about land required is more familiar to the public. But it does lead to these broad statements about feasibility that don't necessarily match up with reality. Real schemes are just going to be more complex and will look at lots of different factors. There is always a limited funds and you have to pick the best opportunities. That is true of very long running projects like nuclear also. Different sites will have different grid connections, environmental factors, ground conditions, access routes, labour force etc.

Because we have trouble finding spots where people don't already live and file complaints to prevent them being built near them? At least on-shore; off-shore is more expensive. If we can get more MW per km² then we can have more power with less trouble.

off shore is more expensive, but it generally has better wind which can balance that out a bit.

And did the general conclusion change that wind wouldn't be able to provide more than even half the energy we need for transport?

Yes. The conclusion has changed!

Electric cars are ridiculously efficient. A 100kwh tesla drives approx 500km. So 50km/day/car needs just 10kwh. The UK also has 2 persons per car (plus additional cats and dogs..)

So just the on-shore book projection is already enough AND only requires a tenth of the turbines.

Lets keep nuclear as well. Invest in efficiency. Lots of hard work ahead.

But we are probably closer to "problem solved" than to "civilization collapse". Cheers.

Just to flag that MacKay already estimated (in 2008) a Tesla at 15kwh per 100km (actually better than you have here). See Fig 20.22 on https://climate.lifeitself.us/without-hot-air/chap20/

I am less concerned about the consumption, but the issue how much available wind energy we can harness in a best case scenario. Only half of transportation seems so low.

> 50km/day/car

For what it's worth "In 2019, the average car in the UK drove 7,400 miles"[0] which works out to 33 km/day/car. It's probably much less now due to working from home (and fuel shortages, and the collapse of the supply chain...)

[0] https://www.nimblefins.co.uk/cheap-car-insurance/average-car...

Yes, very good point. Renewable enegry generation really isn’t the struggle these days, it is transmission from areas with high solar and wind potential to areas with less viable solar and wind production.