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To start with, you're talking about electricity generation, where he is talking about total energy requirements. So your 15% figure doesn't include the energy c

To start with, you're talking about electricity generation, where he is talking about total energy requirements. So your 15% figure doesn't include the energy consumption of cars, aeroplanes, many types of heating etc. I believe he also includes the embodied energy of imports (this was in his book), where if goods are manufactured overseas and imported, it may make sense to count the energy used to manufacture them, depending on what you're measuring exactly. For example, there's little difference between importing aluminium, or importing energy and bauxite and smelting it yourself. Also, area use will not increase linearly with the addition of many renewables, because in many cases the best sites are taken first. Hydro can generate a lot of energy around the clock, but you quickly run out of the best locations. Wind strength varies across the country. In a small country like the UK, solar isn't going to vary much by latitude, and you can probably build it out all over the country. But time shifting of demand isn't always possible, so even if the panels were free, using them to push from (say) 50% of energy from renewables to 100% is going to involve some kind of storage system, which is either going to be very expensive (probably exceeding GDP) and unproven (eg hydrogen fuel cells, lithium ion batteries), or require a ton of space and specific terrain, like pumped water. So that's going to cost a lot of space. Lastly, electricity isn't always the desired final form. If you're powering jet planes, you're going to need some type of biofuel, which is very inefficient per unit area. If and when hydrogen planes are developed, this will stop being an issue (electric cars have already proven their viability). I highly recommend his book. It's a brilliant read, he nicely boils down the issues, and is thoroughly committed to stopping global warming - it's not some doom and gloom oil industry sponsored thing. But he doesn't have his head in the sand about how hard a switch to renewables is going to be, unlike (unfortunately) a ton of the green movement seems to.

Retric 12y ago
If your talking total energy then you need to include food and farms already take a lot of land. So, while close it's vary misleading as going 100% renewable would take less new land than he is suggesting. Add to that you can mix wind farms and regular farms at the cost of less than 1% of the farm land. Not to mention off shore wind farms. Which further reduces the land requirements well below his calculations. Also, Hydro is vary efficient built in storage using it 24/7 is vary wasteful. Wind is 24/7, and solar aligns with peak demand fairly well. Anyway, rather than storage your better off with extra wind capacity that's often wasted, with solar to meet your daily peak and hydro to fill in the gaps. PS: Adding a few peaking power plants is still a good idea, going 80% renewable is a much more reasonable goal until most of the world is at that point. It's silly to chase a few extra % when china is using so much coal power.
phaemon 12y ago
Ok, if we're talking total energy, then 5% rather than 15%. The point still stands. I've no idea why he would include imports. Does he exclude exports? It seems a bit mad. There's a huge difference between me buying some aluminium and having to generate the electricity at my home to smelt it myself as a kind of cottage industry! (A case of he who smelted, dealt it?) The point about area use not increasing linearly is a good one. However, Prof Mackay doesn't do this. He consistently states that - even giving renewables every advantage and pretending they'll always work at peak efficiency - you'd still have to blanket the country with them to make them effective. I've read his book and it's where I first started to think there was something a bit off in what he was saying. Yes, he's very full of the idea that he's the hard-nosed realist and anyone who disagree must have their heads in the sand. I've heard that tactic before.
- reitzensteinm 12y ago
  If your goal is sustainability, there is no difference. Pushing your energy consumption out to another country is just shifting the problem. Though yes, you would want to exclude exports in this model. Picture a hypothetical country that solely consists of stay at home programmers making large sums of money, powered entirely by solar, but importing vast amounts of physical goods manufactured in environmentally unfriendly ways. The country would by traditional measures be a perfect model of sustainability, but it is simply paying others to do unsustainable actions on its behalf. The book isn't really "saying" much, for the most part. The vast bulk of it is simple, back of the envelope calculations for energy consumption which shows working. I realize you might not want to take a half hour to find specific faults in it, but it is not helpful say there is "something a bit off" with a work like that, when the source code is published for all to see. For instance, that he counts embodied energy of imports, and you do not wish to, makes a big difference to the bottom line. Just skimming the chapter headings is enough to point out a concrete disagreement. Fair point about the hard nosed realist tactic often being used to discredit dissenting views. That wasn't my intention, I was more trying to say that the conclusions presented should not be used to infer some political position of the author. There are a ton of studies paid for by the oil industry that paint all kinds of pictures, I just meant it's not a book like that. If I realized you'd already read it, I wouldn't have included that part.

Retric 12y ago

If your talking total energy then you need to include food and farms already take a lot of land. So, while close it's vary misleading as going 100% renewable would take less new land than he is suggesting. Add to that you can mix wind farms and regular farms at the cost of less than 1% of the farm land. Not to mention off shore wind farms. Which further reduces the land requirements well below his calculations. Also, Hydro is vary efficient built in storage using it 24/7 is vary wasteful. Wind is 24/7, and solar aligns with peak demand fairly well. Anyway, rather than storage your better off with extra wind capacity that's often wasted, with solar to meet your daily peak and hydro to fill in the gaps. PS: Adding a few peaking power plants is still a good idea, going 80% renewable is a much more reasonable goal until most of the world is at that point. It's silly to chase a few extra % when china is using so much coal power.

phaemon 12y ago

Ok, if we're talking total energy, then 5% rather than 15%. The point still stands. I've no idea why he would include imports. Does he exclude exports? It seems a bit mad. There's a huge difference between me buying some aluminium and having to generate the electricity at my home to smelt it myself as a kind of cottage industry! (A case of he who smelted, dealt it?) The point about area use not increasing linearly is a good one. However, Prof Mackay doesn't do this. He consistently states that - even giving renewables every advantage and pretending they'll always work at peak efficiency - you'd still have to blanket the country with them to make them effective. I've read his book and it's where I first started to think there was something a bit off in what he was saying. Yes, he's very full of the idea that he's the hard-nosed realist and anyone who disagree must have their heads in the sand. I've heard that tactic before.

reitzensteinm 12y ago
If your goal is sustainability, there is no difference. Pushing your energy consumption out to another country is just shifting the problem. Though yes, you would want to exclude exports in this model. Picture a hypothetical country that solely consists of stay at home programmers making large sums of money, powered entirely by solar, but importing vast amounts of physical goods manufactured in environmentally unfriendly ways. The country would by traditional measures be a perfect model of sustainability, but it is simply paying others to do unsustainable actions on its behalf. The book isn't really "saying" much, for the most part. The vast bulk of it is simple, back of the envelope calculations for energy consumption which shows working. I realize you might not want to take a half hour to find specific faults in it, but it is not helpful say there is "something a bit off" with a work like that, when the source code is published for all to see. For instance, that he counts embodied energy of imports, and you do not wish to, makes a big difference to the bottom line. Just skimming the chapter headings is enough to point out a concrete disagreement. Fair point about the hard nosed realist tactic often being used to discredit dissenting views. That wasn't my intention, I was more trying to say that the conclusions presented should not be used to infer some political position of the author. There are a ton of studies paid for by the oil industry that paint all kinds of pictures, I just meant it's not a book like that. If I realized you'd already read it, I wouldn't have included that part.