Stabilization Wedges (Part 3)

I bet you thought I’d never get back to this! Sorry, I like to do lots of things.

Remember the idea: in 2004, Stephen Pacala and Robert Socolow wrote a now-famous paper on how we could hold atmospheric carbon dioxide below 500 parts per million. They said that to do this, it would be enough to find 7 ways to reduce carbon emissions, each one ramping up linearly to the point of reducing carbon emissions by 1 gigaton per year by 2054.

They called these stabilization wedges, for the obvious reason:



Their paper listed 15 of these wedges. The idea here is to go through them and critique them. In Part 1 of this series we talked about four wedges involving increased efficiency and conservation. In Part 2 we covered one about shifting from coal to natural gas, and three about carbon capture and storage.

Now let’s do nuclear power and renewable energy!

9. Nuclear power. As Pacala and Socolow already argued in wedge 5, replacing 700 gigawatts of efficient coal-fired power plants with some carbon-neutral form of power would save us a gigaton of carbon per year. This would require 700 gigawatts of nuclear power plants running at 90% capacity (just as assumed for the coal plants). The means doubling the world production of nuclear power. The global pace of nuclear power plant construction from 1975 to 1990 could do this! So, this is one of the few wedges that doesn’t seem to require heroic technical feats. But of course, there’s still a downside: we can only substantially boost the use of nuclear power if people become confident about all aspects of its safety.

10. Wind power. Wind power is intermittent: Pacala and Socolow estimate that the ‘peak’ capacity (the amount you get under ideal circumstances) is about 3 times the ‘baseload’ capacity (the amount you can count on). So, to save a gigaton of carbon per year by replacing 700 gigawatts of coal-fired power plants, we need roughly 2000 gigawatts of peak wind power. Wind power was growing at about 30% per year when they wrote their paper, and it had reached a world total of 40 gigawatts. So, getting to 2000 gigawatts would mean multiplying the world production of wind power by a factor of 50. The wind turbines would “occupy” about 30 million hectares, or about 30-45 square meters per person — some on land and some offshore. But because windmills are widely spaced, land with windmills can have multiple uses.

11. Photovoltaic solar power. This too is intermittent, so to save a gigaton of carbon per year we need 2000 gigawatts of peak photovoltaic solar power to replace coal. Like wind, photovoltaic solar was growing at 30% per year when Pacala and Socolow wrote their paper. However, only 3 gigawatts had been installed worldwide. So, getting to 2000 gigawatts would require multiplying the world production of photovoltaic solar power by a factor of 700. See what I mean about ‘heroic feats’? In terms of land, this would take about 2 million hectares, or 2-3 square meters per person.

12. Renewable hydrogen. You’ve probably heard about hydrogen-powered cars. Of course you’ve got to make the hydrogen. Renewable electricity can produce hydrogen for vehicle fuel. 4000 gigawatts of peak wind power, for example, used in high-efficiency fuel-cell cars, could keep us from burning a gigaton of carbon each year in the form of gasoline or diesel fuel. Unfortunately, this is twice as much wind power as we’d need in wedge 10, where we use wind to eliminate the need for burning some coal. Why? Gasoline and diesel have less carbon per unit of energy than coal does.

13. Biofuels. Fossil-carbon fuels can also be replaced by biofuels such as ethanol. To save a gigaton per year of carbon, we could make 5.4 gigaliters per day of ethanol as a replacement for gasoline — provided the process of making this ethanol didn’t burn fossil fuels! Doing this would require multiplying the world production of bioethanol by a factor of 50. It would require 250 million hectares committed to high-yield plantations, or 250-375 square meters per person. That’s an area equal to about one-sixth of the world’s cropland. An even larger area would be required to the extent that the biofuels require fossil-fuel inputs. Clearly this could cut into the land used for growing food.

There you go… let me hear your critique! Which of these measures seem best to you? Which seem worst? But more importantly: why?

Remember: it takes a total of 7 wedges to save the world, according to this paper by Pacala and Socolow.

Next time I’ll tell you about the final two stabilization wedges… and then I’ll give you an update on their idea.

73 Responses to Stabilization Wedges (Part 3)

  1. Frederik De Roo says:

    that the ‘peak’ capacity (the amount you get under ideal circumstances) is about 3 times the ‘baseload’ capacity (the amount you can count on)

    in addition to this you also have a problem with periods when there’s almost no wind, and that there can be large power fluctuations on the electric grid. So I believe that what they call baseload capacity for wind farms is practically not exactly the same as the baseload capacity of power plants working with a controllable energy source, but I should check.

  2. Tim van Beek says:

    Combining wedge 10 and 12 would mean we’d have to increase wind power output by a factor 150?

    The easiest wedge from a pure technological POV would of course be no. 9 (heck, we could have done that in the 1980ties), and it would be too easy to say that wedge 9 cannot be implemented due to political difficulties – but actually this is more a problem of science education resp. science illiteracy.

    I know people who invest a lot of time and energy to protest against CASTOR transports, because those transport nuclear waste. These protests are a recurring event in Germany. For more, see Culture War’ Over Nuclear Power, der Spiegel, in English.

    I spent hours trying to explain to them that sitting directly on a CASTOR, for the whole length of the transport, would lead to a much lower radiation contamination than a single transatlantic flight. To no avail. Somehow many people achieve a good high school grade without ever learning to think quantitatively.

    • John Baez says:

      Tim wrote:

      Combining wedge 10 and 12 would mean we’d have to increase wind power output by a factor 150?

      Yes, starting from its 2004 level.

      Let me say it with a bit less jargon: to use wind power to reduce our coal burning by 1 gigaton of carbon per year and also reduce vehicle carbon emissions by 1 gigaton of carbon per year, we would need to increase the amount of wind power produced worldwide by a factor of 150, starting from its 2004 level.

      This heroic feat would accomplish about 30% of the carbon reductions we need by 2054 to keep CO2 levels below 500 ppm.

      Now, Pacala and Socolow say that in 2004 total wind power was growing at 30% per year, and had been doing so for quite a while! If it continued to grow that fast from 2004 to 2054, total wind power would grow by a factor of 500,000!

      Of course, 30% growth per year for 50 years sounds very hard. To grow by a factor of 150 over 50 years, it would only need to grow at an annual rate of 10.5%. Is it possible to keep up that growth rate for half a century?

      I spent hours trying to explain to them that sitting directly on a CASTOR, for the whole length of the transport, would lead to a much lower radiation contamination than a single transatlantic flight. To no avail. Somehow many people achieve a good high school grade without ever learning to think quantitatively.

      I’m afraid these well-intentioned people may cause a lot of damage. When I get back to Riverside and continue teaching math, I’m going to work a lot harder to show the students that the world is heading for trouble unless they learn a bit about climate, energy, risk… and learn to think about these things quantitatively and calmly — without the conclusions coming before the reasoning.

      • Tim van Beek says:

        Maybe I should add that I highly respect people who take action and participate in peaceful protests, if they are convinced that this is the right thing to do. This is vital for democracy, and it is vital for our community. And that is the reason why I spend time to to dispute with them.

        • John Baez says:

          I agree with you there.

          I want as many people as possible to think very carefully about the next 10, 20, 50, 100 years, because a lot of very big changes are going to happen, and these changes will probably not go the way any established ideologies and preconceived ideas would have us believe. We’ll probably have to do a lot of adapting, and that includes realizing that our ideas and beliefs were wrong.

          So, besides political action, protests and the like (a tradition in my family), I think we should all practice doubting our cherished beliefs.

      • streamfortyseven says:

        You can tell people that if they’re downwind of a coal-fired generating plant, that they’re guaranteed exposure to radioactive fallout from that plant – remember Carbon-14? half-life of 10,000 years? The ultrafine particulate matter which goes right through the scrubbers has Carbon-14 in it, and they breathe it and it gets in their bodies and stays there… whereas with a nuclear plant, the only time there’s the possibility of radioactive fallout is in the event of a Chernobyl or Three Mile Island – and Chernobyl was run with the Russian equivalent of Homer Simpson at the controls.

        • Frederik De Roo says:

          if they’re downwind of a coal-fired generating plant, that they’re guaranteed exposure to radioactive fallout from that plant

          what do you exactly mean? As far as I know coal-fired plants don’t induce nuclear changes in the carbon atoms, burning carbon it’s just a chemical recombination of atoms, so what you call “radioactive fallout” has just the same activity as ordinary carbon dioxide, I think. It’s very different in the case of nuclear plants: ordinary Iodium is not radioactive, Iodium from fissioned Uranium is. I agree that coal-fired plants may exhaust a lot of dirt, but radioactive carbon?

        • John Baez says:

          Frederik wrote:

          I agree that coal-fired plants may exhaust a lot of dirt, but radioactive carbon?

          Radioactive carbon is not a problem with coal, but some people worry about other radioactive isotopes. For a few viewpoints, see:

          • Mara Hvistendahl, Coal ash is more radioactive than nuclear waste.

          • US Geological Survey, Radioactive elements in coal and fly ash:
          abundance, forms, and environmental significance
          .

        • Frederik De Roo says:

          I didn’t know that, thanks! But to put everything in perspective, your second link ends with:

          Other risks like being hit by lightning,” he adds, “are three or four times greater than radiation-induced health effects from coal plants.” And McBride and his co-authors emphasize that other products of coal power, like emissions of acid rain–producing sulfur dioxide and smog-forming nitrous oxide, pose greater health risks than radiation.

          I suppose passive smoking is much worse.

        • John F says:

          Actually by far the main health issues with ultrafines, carbon or not, is their mechanical disturbance of aveoli and other airway structures. Anyway carbon ultrafine scrubber technologies exist, and have quietly become mandatory on diesels in many areas.

          http://en.wikipedia.org/wiki/Diesel_particulate_filter

          Although theoretically the diesel computer uses exhaust pressures to determine burnoff, in practice there is simply an on-off timer cycle.

      • streamfortyseven says:

        and as for wind power, the turbines and blades eventually wear out and have to be replaced, which takes a lot of energy – and it takes energy to make the wind turbines and towers in the first place – and if there’s a hailstorm, the blades can get all dented up and have to be replaced, and the blades are huge. People don’t consider the energy it costs to make and maintain the physical plant when they talk about wind power, it’s like the towers and turbines and blades just magically appear, and keep going for a century or so. Every mechanical device is degraded over time by friction, and the fine balance required to minimize friction in a wind power system can be easily lost due to friction/feedback effects on the driveshaft, cavitation effects on the blades, and so on.

        As for photovoltaic power, there are promising new technologies using thin films effectively printed onto a substrate, but again these are subject to mechanical wear and tear, and the substrate, being a polymeric plastic, is subject to UV degradation and weathering which causes a steady loss in quantum efficiency over the lifetime of the product, and eventual depolymerization and mechanical failure of the substrate.

  3. Peter Morgan says:

    Should we be concerned about the environmental consequences of a wedge’s worth of deployment of Photovoltaic semiconductors? What are the consequences for rare earth extraction? Presumably with such a large deployment the rare earth components of failed PV elements would be recycled. Is the energy cost of recycling failed PVs significant (and accounted for)?

    I suppose it’s not practicable to use a non-PV, non-Biomass catalyzed solar-chemical process to convert captured CO2 to something like methanol or ethanol, recycling Carbon? Biomass is not very well-tuned for human energy use because of the intermediate sugar step. The land use aspect of biomass seems almost certain to cause famine if exploitation comes significantly into play.

    Wave and sea current energy don’t make this list because they’re not an established technology, but they seem a viable large-scale technology for 15 years out if they were legislatively encouraged (in contrast to fusion, which seems to be perpetually 50 years out). All that oil-rig technology, and so much lobbying expertise, must be good for something! It seems that it was lobbying technology that really got wind energy off the ground. It seems a little weird only to be listing technologies that are currently viable on large scales when we’re talking about 50 years out.

    Sorry to put so many dilettante questions. I don’t have time or inclination in this decade of my life to go so far as to get into the literature that must answer all of them. Much kudos to you for taking the leap. Answer as many or as few as you find interesting.

    • John Baez says:

      Don’t apologize for asking so many questions! They all seem interesting. Unfortunately I’m just starting to learn about climate change, energy policy and other environmental issues, and there is a lot to learn, so I can’t answer all of them very well. Since it’s past my bedtime, I’ll just pick one for now, and try some more later — I hope other people join in and help out while I’m sleeping!

      Should we be concerned about the environmental consequences of a wedge’s worth of deployment of Photovoltaic semiconductors?

      Clearly we should be concerned about it, but here’s my gut reaction:

      Overall I think the big question is whether we can deploy a wedge’s worth of photovoltaics in 50 years, not so much whether it’ll be too dangerous. You see, the risk of any activity needs to be compared to the risk of the alternatives. Coal power is so deadly that it’s hard for me to imagine that semiconductor mining and processing could possibly be as bad, if carefully managed. I don’t know anything besides coal power that spews so much particulate matter, sulfur and nitrogen oxide, mercury and lead into the atmosphere. I usually use this argument on people who complain about the risks of nuclear power, but let me say it again:

      In the United States, it has been estimated that coal-fired power plants will cause over 13,000 premature deaths in 2010, as well as almost 10,000 hospitalizations and more than 20,000 heart attacks. Whatever the precise figures are, they are vastly worse in China, where coal power is much more widely used, with far lower safety standards, resulting in much worse air pollution. And the World Bank estimates that in 1995, worldwide, 500,000 deaths were caused by airborne particulates.

      So, more than the environmental problems caused by semiconductor production, I’m worried about whether we can produce enough to obtain a wedge worth of photovoltaics. I don’t know much about this. Here’s one thing I know:

      The efficiency of silicon crystal solar cells peaked out at 24% in 2000. Fancy “multijunctions” get up to 40% and are still improving. But they use fancy materials like gallium arsenide, gallium indium phosphate, and so on. The world currently uses 13 terawatts of power. The US uses 3. But building just 1 terawatt of these fancy photovoltaics would use up more rare substances than we can get our hands on:

      So, if we want solar power, we need to keep thinking about silicon and use as many tricks as possible to boost its efficiency.

      • G.R.L. Cowan says:

        John Baez writes,

        they use fancy materials like gallium arsenide, gallium indium phosphate, and so on

        That would be gallium indium phosphide, most likely, since it and arsenic are homologues. As are Ga and In.

        As I understand the role of rare elements in photovoltaic power, they are not likely to be a limiting factor, because they are used as dopants: very thin leavenings in ultrapure silicon, which would be even more ultrapure if it were not doped with, IIRC, parts per million of things like P and B. And anyway, if so much money becomes available for gigawatt-year-per-year PV installations that their demand for whichever dopant is most scarce drives up its price, it becomes worthwhile to look for more, and in the case of chemical elements that are stable over geological time, this search has never been known to fail.

        The limiting factor is money. Only government will provide it, and — I believe — only to the extent that photovoltaics are not so much developed that they cut into governments’ fossil fuel incomes. That is, they are token fossil fuel revenue reducers and as such live on a token disbursement of the very money that, to be genuine, they would have to annihilate.

        How fire can be domesticated

        • Peter Morgan says:

          Which seems to suggest that government should be encouraged to lay out a road map for taxation of alternative energy production?

          There are currently grants, negative taxation, for alternative energy, but it might cut into the lobbying power of fossil fuel producers if there were a clear direction towards a similar landscape for alternative energy. With the right design, a taxation road map might increase the incentive for getting into alternative energy now, instead of waiting for the technology to mature. There could, for example, be tax credits after 2020 for fossil fuel producers who make significant investments in alternatives now. Much of the battle must surely be to capture the imagination of industry.

          It seems that because legislation has become so crucial, industry has become used to gaming the rules, often very creatively. Lobbying effectively for obvious things like earmarks seems to me to be only the crudest approach. The process has to be gamed as creatively from an environmental perspective, but it seems that it may be most effective if we can find a way to proceed that seems positive from an industrial perspective.

        • John Baez says:

          GRL Cowan wrote:

          That would be gallium indium phosphide, most likely, since it and arsenic are homologues.

          Sorry, thanks for catching that. I’ve fixed week293, where I originally made that mistake. I’ve credited you for catching it. (See, I want people to catch my mistakes!) But I think the bigger mistake I made is this:

          I got my information from a talk by Harry Atwater, who really knows his stuff. So when he says building building 1 terawatt of fancy photovoltaics would use up more rare substances than we can get our hands on, he must be approximately right. Of course, we could switch to other materials, or do more mining, but still, I think he must be on to something — there must be some real issue of concern here. And I think my mistake was focusing on gallium arsenide and gallium indium phosphide. Althought indium is rare, it seems that rare earths are what have people really nervous. Here are two references:

          • Gordon B. Haxel, James B. Hedrick, and Greta J. Orris, Rare earth elements – critical resources for high technology, US Geological Survey Fact Sheet 087-02, available at http://pubs.usgs.gov/fs/2002/fs087-02/.

          • R. L. Jaffe, Critical elements for new energy technologies, Progress report from an APS-POPA/MRS study.

          The second one, some slides that Jaffe prepared on 3 December 2010, promises a more formal report in early January. It focuses a lot on tellurium but also mentions other substances.

          It also mentions recycling! So, people here talking about that might be interested in these comments:

          The role of recycling

          Recognize special nature of rare elements. Viz. gold, silver,platinum.

          Recycling serves many purposes: Displaces virgin production, generates independent supply stream, reduces environmental disruption.

          Create consumer awareness of the preciousness of these materials.

          But recycling cannot play a primary role in an
          exponentially expanding market.

          The last point is pretty simple and robust.

      • Peter Morgan says:

        So, there have been health problems because of electronics waste, but they’re more like the insidious health problems caused by coal, so they’ll likely result in a smaller response than we see to the possibility of catastrophic nuclear problems.

        As to “if carefully managed”, how careful must we make the legislation and enforcement of careful management, or will the relatively high cost and rarity of rare earths be enough motivation on its own to keep the backyard clean? Still, even though this might result in 1950s/60s Silent Spring kinds of problems, you’re right that this is just a small feedback loop compared with the carbon dioxide/climate feedback loop we’re struggling to adjust.

        One recent change that strikes me as very instructive is the recent introduction of single-stream recycling. Why did it take so many decades to realize/discover that the increased recycling compliance of this model would more than pay for the increased costs? [Or perhaps it's just that the cost of disposing of trash increased to the point that single-stream recycling became cost-effective?]

        • DavidTweed says:

          As it would be helpful for the wiki, what’s the source for showing that single-stream recycling, or indeed any recycling, is cost effective? (My very limited understanding is that an awful lot of recycling isn’t cost effective, but that’s due to s a combination of cheap energy, lack of “buyers” for separated recyclables and ignored external costs. And there’s the point that money isn’t the only consideration.)

        • Peter Morgan says:

          Wikipedia has a page on single stream recycling, which cites a “recycling today” news article that is more definitive than I can otherwise give. It’s clear from that that increased separation of recyclables from trash by householders makes it more profitable than insisting on multiple stream recycling.

        • DavidTweed says:

          In a very careful reading of the wikipedia and linked article, I can’t see anything that actually mentions cost-effectiveness or profitability of the processas a whole. It discusses trade-offs in participation rates vs contamination, and increasing participation is desirable generally.

          The reason that I asked is that it would be great if we could put that recycling is monetarily profitable. But all I can find are articles that suggest that recycling companies are only profitable compared to new production because of subsidies and charges to the municpal authority. (That may very well be because new production has many unpaid externalities.)

        • Peter Morgan says:

          Hi David,
          My condo has a direct contract for both recycling and trash pickup with a trash company (the city does not service condos that have more than 6 units). The trash company recently went to single stream and allowed a wider range of recycling categories.

          (1) maybe trash companies like higher compliance for recycling because land-fill rates are so high and the rates for recycling streams are lower (my “obvious” explanation).
          (2) maybe customers have been migrating to trash pickup companies that allow single-stream, in which case trash companies, to be profitable, have to provide the service. Any increased costs will have to be rolled back into the customers’ contracts.

          Given my condo’s contract, the municipality does not figure directly. It’s possible, though, that as large customers municipalities establish a requirement for single-stream recycling for their trash contracts, for purely altruistic reasons, at some additional cost. In that case my condo is merely piggybacking on the municipality’s decision. Write to “Recycling Today”, perhaps?

        • Peter Morgan says:

          Research, … For New Haven, CT, the Office of Sustainability says “It costs the City $87.50 to dispose of a ton of garbage versus $36.80 per ton of recycling. This amounts to a net savings of $50.70 per ton diverted to recycling.” This doesn’t speak to single-stream recycling, but it goes all the way for why municipalities are keen on recycling.

          http://www.cityofnewhaven.com/Sustainability/Recycling/RecyclingFAQ.asp

        • DavidTweed says:

          Thanks, I’ll look into that. For what it’s worth, I’m in the UK where almost all domestic and some business waste is taken either by companies subcontracted by local councils or direct council subdivision and ultimately paid for by various local taxes.

      • Robert Smart says:

        Killing the coal industry is the core of any successful plan. In Australia the mining unions are very powerful, the coal industry is very powerful. Early steps to increase use of “renewables” have already added significantly to voter power bills. Meanwhile a committee reported to the Prime Minister that the best way to meet our carbon goals was to increase power prices enough to reduce consumption of electricity by 15%. This is total political fantasy. Not only that, but the government plans to make these energy taxes revenue neutral, returning the money to the poor people who’ll be worst affected. Presumably they think people will cleverly find some way to spend the money that doesn’t use any energy. This is what you get from having no model of the economy to plug plans into. Let’s prepare ourselves for a decade of failure in combatting the coal industry. The hope of the world is that there is much more scope for technological progress in the Nuclear power industry than in the coal industry. People hoping to harness good will (or fear) to replace the coal industry with more expensive power sources are surely going to be disappointed. We need something cheaper.

        Meanwhile the debate between Dave Rutledge and Deve Summers (and others) on whether coal is running out continues [link]. They respectfully address each others positions!

        • John Baez says:

          Robert wrote:

          Meanwhile a committee reported to the Prime Minister that the best way to meet our carbon goals was to increase power prices enough to reduce consumption of electricity by 15%. This is total political fantasy.

          It may be; it depends on whether the populace can look ahead to see how their short-term interests conflict with their descendant’s long-term interests. At least where I come from, we’ve shown little capacity for that. So, I expect that dramatic changes will only occur after things get much worse.

          As George Mobus recently wrote:

          Our political leaders depend on votes to gain power. We vote for whoever promises us the most material prosperity; in other words, whoever promises us growth of the economy. They then need to find any way necessary to keep the GDP numbers growing.

          [...]

          This is perhaps the most difficult conundrum for the general public to get their heads around. They will deny it. They will ask why now? They will, in general, relegate the notion to the doom-and-gloom crowd (in the derogatory sense). They will not accept that this generation of human beings will be the first to experience the beginning of restrictions on freedoms.

          Of course, my own view is that if things get really bad in a worst-case scenario they will be more willing to accept an authoritarian solution. History has shown that this is a common response to clear crises.

          Robert wrote:

          Let’s prepare ourselves for a decade of failure in combatting the coal industry.

          Don’t worry, I’m prepared for that.

          People hoping to harness good will (or fear) to replace the coal industry with more expensive power sources are surely going to be disappointed. We need something cheaper.

          There may not be anything cheaper — at least in the sense you seem to be talking about. Let’s face it, digging up flammable rocks, burning them, and letting the resulting CO2, SO2, NOx, particulates and poisonous heavy metals pour into the atmosphere is hard to beat on cost — if we are willing to neglect all the costs in disease, death and global warming that this creates!

          And of course the coal business generates enough money to fund lots of lobbyists whose job is to make damn sure we continue to neglect those ‘externalities’.

    • Phil Henshaw says:

      Well… the most fundamental impact of “a wedge” worth of Photovoltaics is the need to permanently set aside 3.5 sf (~1/3 sq meter) of land for every $1 of GDP the energy will be used to generate. So photovoltaic energy delivering a 10% wedge of GDP would be ~60 trillion times that today. I think that equals 2 billion sq kilometers of solar farm. You’d then need to double every 40 years or so to maintain the 10% share of economic energy required at the historic rates of energy and GDP growth.

      John checked my figures on that, and seemed to conclude they were OK for ballpark estimates.
      http://www.synapse9.com/design/dollarshadow.htm

      • Florifulgurator says:

        1) The “land” needed for PV is mostly roofs.

        Here in Germany there are enough roofs suitable for PV to produce all private energy demand. Roofs make up 0.65% of German land area. To produce all electricity, 1.8% of land would be needed. Settlement and transportation use 13%. (Source: http://de.wikipedia.org/wiki/Photovoltaik )

        2) It looks those historic rates of energy and GDP growth are indeed history.

        • Phil Henshaw says:

          How many roofs does your house have? Anecdotal arguments are great for generating questions, though. Do the math… For the area of energy collection needed to produce the income of the building occupants…

        • Florifulgurator says:

          To make things look better, here’s just the electricity math. (Typo in my post above: delete first “energy”, set “electricity”.)

          The occupants of my average German house would need 1.8% / 0.65% = 2.77 roofs to generate their share of total German electricity consumption.

      • John Baez says:

        Philip wrote:

        So photovoltaic energy delivering a 10% wedge of GDP would be ~60 trillion times that today. I think that equals 2 billion sq kilometers of solar farm.

        But we’re not trying to accomplish this goal!

        Your estimates of how energy usage correlates to GDP are fascinating and — to me, at least — quite mysterious. I never would have believed, until I did the calculation myself, that world energy usage divided by world GDP was approximately 7.3 million joules per dollar. I don’t know why the figure is so high… or what it even means. It’s worth studying. But it’s not what I’m talking about here!

        Pacala and Socolow are not trying to replace 10% of world GDP with some sort of photovoltaic solar energy equivalent (whatever that means). They’re talking about switching some fossil fuels over to — for example — solar energy.

        And for that, Pacala and Socolow estimate:

        Eliminating 1 gigaton/year of carbon burning by replacing coal with photovoltaic solar power would take 2 million hectares of solar power plant, or 20,000 square kilometers, or 2-3 square meters per person.

        Or if you prefer: 1/7 the area of England, or 1/14 the area of Arizona.

        Of course, it’ll be distributed over the whole world, not packed into a few patches as shown here:

        Note: this picture shows the area required to supply the world’s entire demand for energy using 18 terawatts of photovoltaic solar power — not the measly 2 terawatts we need to save 1 gigaton of carbon per year.

        So, in terms of sheer area, I don’t consider it outrageous to generate 2 terawatts of solar power by 2054. To my mind, the hard part is getting people to build all those solar panels!

        • Austin Shapiro says:

          John Baez wrote:

          I never would have believed, until I did the calculation myself, that world energy usage divided by world GDP was approximately 7.3 million joules per dollar. I don’t know why the figure is so high… or what it even means.

          I’d be interested in hearing more about this. It seems worth noting that while 7.3 million joules sounds like a big number, it’s actually the energy content of about 0.2 liter of gasoline (or two sticks of butter).

        • John Baez says:

          Austin wrote:

          I’d be interested in hearing more about this. It seems worth noting that while 7.3 million joules sounds like a big number, it’s actually the energy content of about 0.2 liter of gasoline (or two sticks of butter).

          Hey, good point! To some extent I was probably just shocked by the big-sounding number. Let me check your work here. Here someone estimates the energy density of gasoline at about 35 megajoules/liter, so yes, 0.2 liters is about 7 megajoules.

          And as for butter, well, I see a figure of 1628 kilocalories per cup, which makes me wish I’d found a European website, since the Europeans list food energy in joules — but anyway, they also say that a cup of butter is 227 grams, so butter has 7.2 kilocalories per gram, or 30 kilojoules per gram. So 7 megajoules of butter is about 230 grams of the stuff. And over here, you’ll see a bewildered Australian being informed that there are 113 grams of butter in an official American ‘stick’. So yeah: 2 sticks of butter, like you said!

          Anyway: if you want to read more about this ‘7.3 megajoules per dollar GDP’ idea, you can look at Philip Henshaw’s webpage and then my own little calculation.

          I now consider this result a lot less bizarre — thanks! But I’m still not sure of its implications. It is sort of depressing to think that we need 1/3 meter2 of solar cells collecting energy for a year to get this amount of energy… but I’m not sure how ‘bad’ that really is.

          Luckily, I don’t think my confusion affects anything I said in this blog entry!

        • Phil Henshaw says:

          Yes, my point is that the problem looks remarkably different depending on the question you ask. The basic fact I’m pointing to is that switching from fossil fuel energy sources to renewable energy involves switching from taking your energy from relatively small holes in the ground to relatively large areas of land. Solar energy is delivered by the square meter, not barrel.

          We’re not accounting for the land cost, or lots of other things, when falling for the tempting idea of the resource problem being “only a matter of finding another source of energy”. I think that is definitely not our resource problem.

          I think our resource problem is that our plan calls for being ever more productive with ever less productive resources. It’s hard to define the questions someone else wants to ask, but I think it’s fairly demonstrable that culturally we’ve been asking a variety of the wrong ones.

        • Phil Henshaw says:

          John & Peter,
          A couple clarifications, the area figure is not of PV panels, but my approximation for the area of land needed, which I estimated as x2 the area of PV panels.

          My radiation data comes from average monthly radiation, that for the yearly total I use x12 and for the daily /30. The labeling of the chart seems a little confusing.

        • Ezequiel says:

          7.3 million joules per dollar

          Does that count off-the-grid energy use? For example, tumble drying in the US vs. hanging your clothes in the sun. Solar energy use, right there, but never comes up in any excel sheet. And it sure is hard work.

        • Florifulgurator says:

          There we are: A fundamental economic magnitude expressed in three different fundamental biophysical quantities: Petrol resp. Butter (i.e. past resp. current products of the biosystem) and PV area/day (production outside biosphere – grams Uranium would also fit in this category).

          A triality? Perhaps a Mad Economist could make a theory out of it, going with the octonions alongside the Standard Model of elementary particles to the continuum limit of Classical Economics… :)

        • “world energy usage divided by world GDP was approximately 7.3 million joules per dollar.”

          Hold on a second, 64T$/year means 64e12/(3600*24*365.4) = 2e6 = 2 M$/second

          During that second we use 14TJ (the world consumes 14TW) to produce those 2 M$, which makes exactly for 7MJ used to produce that dollar of “value”).

          Perhaps less accurate but easier to remember :)

          I don’t eat butter but i bet those 2 sticks of butter cost more than a dollar (at least in the US), it would be interesting to really understand why, and what happens to the difference.

        • Well i am mixing things up. The “value” of something, the energy used to produce it, and the energy you get out of it when you burn it are different and independent things, not even directly related.

          Although a case can be made that they must be indirectly related.

        • John Baez says:

          Giampero wrote:

          The “value” of something, the energy used to produce it, and the energy you get out of it when you burn it are different and independent things, not even directly related.

          Right.

          Although a case can be made that they must be indirectly related.

          There’s a field called thermoeconomics where they try to understand these questions. I would like to learn more about it. If you find out more, Giampero, please let us know! Somehow I think you’d like it.

          See also embodied energy.

        • Phil Henshaw says:

          maybe some high faluting term like “thermoeconomics” is what you’d call my rather well constructed argument that:

          $ = energy

          It’s not mystical at all, but that if you count the highly diverse spending that people do as probably having about “average” energy intensity, well, since people is the main cost of business it makes most everything about “average” intensity, 8000btu/$.

          So,… I think we actually have had an energy currency all along, given some adjustment for inflation and such. Lots needs to be studied, but the provable part is that counting up only the energy uses you can trace, takes a great deal of effort and produces a highly misleading answer.

        • J/unit currency is known as energy intensity of an economy. Sometimes I have seen the reverse unit currency/J when you have long time series with fix money rate.

        • Phil Henshaw says:

          Regarding $/energy or energy/$, the only reason the ratio seems to have a useful meaning is that it, GDP and energy use are all changing in constant proportion to each other. It displays an emergent property of the world economic system, and quite important for understanding things.

      • Peter Morgan says:

        Can you tell us how you get your starting figure for “average daily radiation” of 7500 Wh/sqm.mo? From Wikipedia, http://en.wikipedia.org/wiki/Solar_radiation, I get average radiation flux at earth orbit of 1350 W/m2, which gives

        1350W/m2*24hour/day*30day/month = 972000Wh/m2/month.

        Divide by 4, ballpark, for night and for being not orthogonal to the flux, I get 243000Wh/sqm.mo, 30-ish times your number. Is the Wikipedia number wrong, or is your number already corrected for visible light range or for something else? Or, my mistake?

        • John Baez says:

          Peter writes:

          Can you tell us how you get your starting figure for “average daily radiation” of 7500 Wh/sqm.mo?

          I’m not 100% sure who ‘you’ is: it’s better to use names in these multiparty conversations. You’re replying to a post of mine but I’ll bet it’s Philip Henshaw, since personally I avoid mixed units like ‘watt-hours per square meter per month’. Joules per second times hours divided by months divided by square meters? Metric was invented to avoid this.

          You can get some information on solar radiation here. In a nutshell: the Earth’s surface gets 156 watts/meter2 (counting all wavelengths) as a global average, since the atmosphere absorbs a lot.

          On the other hand, 7500 watt-hours per square meter per month is just 10 watts/meter2! What’s up?

        • Phil Henshaw says:

          The link I used for the DollarShadow page is reference (a) there. What I did was look at the maps of average recorded radiation at the ground and picked a band that looked “average”. Actual performance might vary from average by factor of 2, but not 10.

          a) Historical average solar radiation at the ground: http://www.oksolar.com/images/daily_solar_radiation4.gif (picking an average mid latitude location)

        • John Baez says:

          Hmm — interesting, Phil. I’m not sure what’s up. We should sort this out.

        • Graham says:

          This graph linked to by Phil is titled per MONTH but the table shows figures per DAY.

          a) Historical average solar radiation at the ground: http://www.oksolar.com/images/daily_solar_radiation4.gif

        • Peter Morgan says:

          Though it’s niggling, the average 156W/m2 looks slightly wrong as what ought to be available at the surface of a PV panel, because it includes a component for reflection from the earth’s surface. The diagram at

          http://www.cgd.ucar.edu/cas/abstracts/files/kevin1997_1.html

          suggests that 198=168+30 W/m2 is available at the surface. The PV efficiency of 19% presumably includes an allowance for reflection, which would be double counting that component of the loss.

          156W/m2 = 3744Wh/m2/day is somewhat smaller than the 4-10kWh/m2/day listed at

          198W/m2 = 4752Wh/m2/day gets somewhat closer. Another possibility is that the factor of 4 would be replaced by a factor of 2 if we were to assume that PVs track the sun, instead of being static, which seems to make up the whole difference. If there were almost no reflection from clouds or from aerosol, almost ideal conditions, 500W/m2 = 12kWh/m2/day seems about right as the outright maximum achievable average flux usable by tracking PVs.

          As John notes, however, “On the other hand, 7500 watt-hours per square meter per month is just 10 watts/meter2!” remains to me a small mystery.

        • Crazy Bill says:

          Rather than trying to work out “from theory”, perhaps better to see what panels actually achieve in practice. Here’s a relevant wikipedia page:

          Photovoltaic array: Performance, Wikipedia.

          “Typical” performance apparently about 150W per sq m, and daily totals ranging from 1kWh/day in sunnier parts of US/Europe to 8kWh/day in Sahara-like places.

          I think I’d believe these numbers more than the earlier smaller numbers.

        • John Baez says:

          Crazy Bill wrote:

          Rather than trying to work out “from theory”, perhaps better to see what panels actually achieve in practice.

          Very good! Personally, I want to understand all sorts of stuff like how much solar radiation hits the Earth, what’s the efficiency of solar cells, and so on… so I enjoy the exercise of working things out “from theory”.

          But to get the right answer, you’re right: it’s better to just look and see. And knowing the right answer, and comparing it to the answer worked out “from theory”, is a great way to test whether we understand what’s going on!

          So thanks!

    • John Baez says:

      Peter wrote:

      It seems a little weird only to be listing technologies that are currently viable on large scales when we’re talking about 50 years out.

      That’s an interesting point.

      First — and I’d forgotten to mention this! — the point of Pacala and Socolow’s paper is to prove that we can do it with existing technologies. Their paper is called “Stabilization wedges: solving the climate problem for the next 50 years with current technologies.” And the first paragraph reads:

      The debate in the current literature about stabilizing atmospheric CO2 at less than a doubling of the preindustrial concentration has led to needless confusion about current options for mitigation. On one side, the Intergovernmental Panel on Climate Change (IPCC) has claimed that “technologies that exist in operation or pilot stage today” are sufficient to follow a less-than-doubling
      trajectory “over the next hundred years or more”. On the other side, a recent review in Science asserts that the IPCC claim demonstrates “misperceptions of technological
      readiness” and calls for “revolutionary
      changes” in mitigation technology, such as fusion, space-based solar electricity, and artificial photosynthesis. We agree that fundamental research is vital to develop the revolutionary mitigation strategies needed in the second half of this century and beyond. But it is important not to become beguiled by the possibility of revolutionary technology. Humanity can solve the carbon and climate problem in the first half of this century simply by scaling up what we already know how to do.

      Second, I’ve heard it said that the time it takes to scale up energy technologies is too slow, and climate change is happening too quick, for us wait for a technological ‘silver bullet’. According to this view, while we may need to develop new technologies to save ourselves, we also need to proceed full-speed with the technologies at hand.

      Given the uncertainties involved, one could also argue that whether or not it turns out to be necessary, it’s simply prudent to proceed full-speed with the technologies at hand.

  4. Phil Henshaw says:

    Well, I think most people leave out the fact that the sun doesn’t shine at night.. and things like that.

    If one guesses 7500Wh/m2/month would be like having peak intensity for 4hr/day that’d be 62.5Wh/hour intensity to compare with 1369 Wh/hour entering the atmosphere from the sun. It implies that only 5% gets through, which does seem quite low. I would have guessed maybe 20% gets through. But my source for the 7500 is picked as on the high side of the annual average incident radiation for the US, as measured by the National Renewable Energy Laboratory resource assessment program.

    So maybe only 5% gets through… *on average* and most people doing estimates are talking about “peak” values instead. I spent a good bit of time searching the web for anyone reporting their power output from a working PV farm, and really couldn’t find anyone reporting the total, only peak. With that data one could check the measured radiation and power output figures to see if they correspond:

    http://www.nrel.gov/gis/solar.html

    • John Baez says:

      Phil writes:

      Well, I think most people leave out the fact that the sun doesn’t shine at night.. and things like that.

      I’d hope most people studying solar power would take into account the existence of night.

      Certainly the figure that I cited, 156 watts/meter2, takes into account the fact that the sun doesn’t shine at night, the Earth is round rather than a flat disc, and the atmosphere and clouds absorb and reflect a lot of radiation. But as Peter Morgan points out, this figure also includes reflection by the Earth’s surface, which is stupid for the present purpose! That figure was useful for climate science, not for people studying solar power. My fault: the Azimuth Project page made it clear.

      So, I’ll add Peter Morgan’s figure of 198 watts/meter2 to that Azimuth Project page after checking it out a bit.

      I still need to get to the bottom of this.

      • John Baez says:

        Okay — as Graham pointed out, this chart really lists figures of average solar power in kilowatt-hours per square meter per day, not per month. Also, it seems this is per square meter of solar panel optimally designed to track the sun, not per square meter of ground.

        The chart gives a figure of about 7.5 kilowatt hours per square meter per day, for sunny parts of the USA like Utah and Nevada.

        So, I think Philip’s figure of 7.5 kilowatt hours per square meter per month is pessimistic by a factor of about 30. If so, I hope he fixes that.

        Let’s see what 7.5 kilowatt hours per square meter per day equals in reasonable units like watts/meter2. Since 7500 / 24 = 312.5, it equals about 310 watts/meter2.

        This seems perfectly consistent with Peter Morgan’s figure of 198 watts/meter2, since the latter figure is presumably a world average, not just for sunny parts of the USA, and it’s presumably per square meter of ground, not per square meter of sun-tracking solar cells.

      • Phil Henshaw says:

        Peter, you give a BP source for 4.74E20 Joules/year world energy use. The IEA gives 512 quadBtu’s, or 5.4*10^20 jules in 2008 so BP is not too far off.

        What are you trying to calculate, though, the best available energy resources on the cheapest land? That would be good strategy for a business investor, possibly, but it doesn’t typify the environment our economy needs to find some way to live in. What I was doing was drawing an average PV availability as a “reality check”.

        Of course, the high quality solar resources will be used first, and then less and less valuable ones until all that’s worth investing in is exhausted, just as is occurring for oil. That’s just what economies are designed to do, as fast as possible to maximize present profits. It doesn’t maximize sustainable profits though. It uses up potential earnings.

        For some reason there don’t seem to be oceans of PV in the Sahara, so maybe there are hidden costs and the real EROI is actually closer to 1:1 than anyone could afford to invest in. There’s an important discovery I made regarding a deep conceptual error in estimating EROI’s, for the traditional LCA energy assessment methods.

        Estimates for business energy costs of every sort seem to incorporate a nominal factor of 5 methodological error methodology… System Energy Assessment (SEA) The standard method only counts the energy uses that are traceable from business records, and that’s only ~20% of them for a business like a wind farm…!

        So, looking at “averages” can help you ask the right questions, especially if your “totals” are consistently way below average.

      • streamfortyseven says:

        I’m pretty sure that no one has yet addressed the question of quantum efficiency of photovoltaic solar power, which is a really big limitation on the use of PV. Solar cells only convert a small fraction of the incident solar radiation into electricity – see http://en.wikipedia.org/wiki/Quantum_efficiency and http://en.wikipedia.org/wiki/Quantum_efficiency_of_a_solar_cell
        “STC specifies a temperature of 25°C and an irradiance of 1000 W/m² with an air mass 1.5 (AM1.5) spectrum. These correspond to the irradiance and spectrum of sunlight incident on a clear day upon a sun-facing 37°-tilted surface with the sun at an angle of 41.81° above the horizon.[1][2] This condition approximately represents solar noon near the spring and autumn equinoxes in the continental United States with surface of the cell aimed directly at the sun. Thus, under these conditions a solar cell of 12% efficiency with a 100 cm2 (0.01 m2) surface area can be expected to produce approximately 1.2 watts of power. On June 16,2010, Sanyo Corporation announced the world’s most efficient solar module, with a claimed energy conversion efficiency of 20.7%.”

        • John F says:

          s47, quantum efficiency is of course only one part of overall efficiency, which has been addressed here in every PV discussion. Potentially inexpensive solutions to the efficiency problem made with abundant resources (i.e. silicon) do not exist for the purposes of power generation.

          Even with quantum dot rare earths etc., one part of the PV cell efficiency problem is having to use solids. The charge carriers are not just knocked locally from one energy to another – they actually go from one piece of solid to a different piece. Cell anode-cathode geometry is one limiting factor (e.g. if pieces are close enough then some block out).

          It seems to me fairly obvious that much higher efficiencies are only possible at the molecular level, i.e. photochemistry in solution rather than photovoltaics. Unfortunately in the context of power generation most photochemical investigations have focused on funky catalysts for photoelectrolysis.

          http://en.wikipedia.org/wiki/Photoelectrolysis

  5. Sailric says:

    Hope I’m not too off topic, as you may intend to cover it in a later post, but what about solar thermal or CSP plants? I don’t believe solar thermal was covered in the original Pacala and Socolow work. Joseph Romm, at Climate Progress, likes solar thermal enough to give it potentially two wedges in his “Introduction to Core Climate Solutions” articles, that are based on the Pacala and Socolow work. Solar thermal is not nearly as intermittent as PV solar or wind, assuming it’s placed in highly sunny areas, and especially if equipped with molten salt or other form of heat storage.

    In fact, its ablility to generate large amounts of dispatchable power (with heat storage) should make it easier to blend intermittent sources like PV solar and wind power into the grid. Here’s an article on that:

    http://www.altenergystocks.com/archives/2009/04/why_csp_should_not_try_to_be_coal.html

    I think CSP is our most promising renewable, because of its versatility, and its ability to generate power on a scale like nuclear or coal plants do. It can be combined hot water and power, or it can be combined power and desalination, or it can be used just for the heat, like for agricultural food processing or industrial use, or other uses.

    • John Baez says:

      Sailric wrote:

      Hope I’m not too off topic, as you may intend to cover it in a later post, but what about solar thermal or CSP plants?

      I certainly want to talk about these more at some point — but for now, you might peek at my blog entry on Archimede, a big concentrated solar power plant in Italy. Also, we’re starting to accumulate information about CSP here:

      Concentrated solar power, Azimuth Project.

      Alas, there’s not much here yet except links to pages on Archimede and Desertec — so if you want to contribute more information, that would be great! Just hit ‘edit’.

      I don’t believe solar thermal was covered in the original Pacala and Socolow work.

      No, it wasn’t. That’s why I’m not talking about it yet. I have an insanely ambitious plan to figure out how humanity can save the planet, but I’m not very well-informed about the necessary subjects yet. So, I want us to systematically go through various plans listed here, and maybe others too if you know some:

      Plans of action, Azimuth Project.

      I’ll summarize them; you folks can critique them and provide extra information… and that information will get polished up and go into the Azimuth Project, so it’s easy to find. Frederik de Roo has been helping me on this for Pacala and Socolow’s paper, summarizing your comments here:

      Stabilization wedges, Azimuth Project.

      So, it’ll get a bit confusing if I jump the gun and start talking a lot about CSP right now.

      However, as you mention, Joseph Romm does include CSP in his modified version of Pacala and Socolow’s plan — and Romm’s plan is on our list. So, concentrated solar power will have its day in the sun!

      In fact, I may talk about their plan right after I finish up with Pacala and Socolow’s plan, and also Stephen Pacala’s “update” on his plan — a talk he gave at Stanford.

      In fact, its ability to generate large amounts of dispatchable power (with heat storage) should make it easier to blend intermittent sources like PV solar and wind power into the grid. Here’s an article on that:

      http://www.altenergystocks.com/archives/2009/04/why_csp_should_not_try_to_be_coal.html

      Thanks! I’ll add that to the wiki now! And I’ll also add the information you provided below…

  6. Sailrick says:

    Another interesting way to use solar, is what Zenith Solar of Israel, and Cogenra are doing. – Concentrated PV Solar that also produces hot water (from the cooling of solar cells)

    Cogenra’s ‘Hybrid’ Solar System Captures 80% of the Sun’s Energy to Generates Electricity and Hot Water

    http://www.treehugger.com/files/2010/11/cogenra-hybrid-solar-system-80-percent-efficient-electricity-hot-water.php

    http://www.cogenra.com/

    Zenith Solar

    http://www.zenithsolar.com/index.html

    Zenith claims they get 75% overall efficiency

    • Peter Morgan says:

      For the Zenith Z20, 22m^2 of mirror reportedly generates 4kW peak power as electricity plus 11kW peak power as hot water (http://www.zenithsolar.com/products.html). To follow Crazy Bill’s lead, that’s total 180+500=680 peak W/m^2(of mirror). It would be interesting to know how the two components of this power scale with variations of cloud cover.

      • Crazy Bill says:

        Now we’re talking… as long as there is someone nearby who can use that hot water. The website talks about heating needs, so these systems are going to be best placed near populated areas (with enough water to run through the system).

        Probably not the Sahara…

        If the thermodynamics can be made to work however these do look like a very nice design – the reflectors can be cheaply mass produced as they’re basically plastic extrusions, and the small (11cm diameter) PV cells could potentially be upgraded with little work if technology advances enough to make that worthwhile. Now, where can I buy a couple of units myself?

  7. John F says:

    Apropos of getting rid of waste in general, occasionally people imagine compacting it into tiny black holes. And yes, you could generate some usable energy depending. However, some sizes of black holes may be harder to make than maybe thought.

    http://www.physorg.com/news/2010-12-large-hadron-collider-signatures-microscopic.html

    • John Baez says:

      No physicists in their right minds really thought the Large Hadron Collider would make microscopic black holes. However, not all physicists are in their right minds!

      My friend Louis Crane has proposed artificial black holes as the ultimate power source. In principle it should work. But as he concedes, “This proposal is extremely difficult technically.”

      I expect it could take a few centuries if technological progress proceeds at about the current rate. (That’s a big “if”.) It seems extremely unlikely that we’ll be able to do it in time to stop global warming.

      • John F says:

        I can’t tell if I’m living inside a black hole or not. Sorry, off topic, but one of my family’s (and then friends’) favorite memes is “I can’t tell if I’m ___ or not”. Almost anything put in the blank is funny and sometimes thought provoking.

        It was inspired by my young son years ago fighting with a boy, and the other boy said “I can’t tell if I’m bleeding or not” while trying to find physical evidence on himself to justify crying. I was approaching to punish them for fighting, but wound up rolling on the ground laughing too hard.

        I think artificial black holes may not be as feasible as ultimate power sources as (stationary) Alcubierre type warp drives

        http://en.wikipedia.org/wiki/Alcubierre_drive

        Exotic matter is not actually needed if conformal gravity is demanded, and of course those conformal terms yield dark energy effects etc. Maybe only a tithe of the Earth’s resources and population, for maybe only a millenium, and we could see some real progress on the warp drive.

        Usually I think nothing meaningful will be done about *stopping* climate change, so resources would be better spent on responding to it happening. Realistic technological solutions all must involve gigantic geoengineering (or climate engineering) projects, but as a species we can’t even get our act together to spray a little ocean water to obviate local droughts (partly via the Twomey effect).

        • John Baez says:

          John F wrote:

          I think artificial black holes may not be as feasible as ultimate power sources as (stationary) Alcubierre type warp drives…

          None of this is terribly relevant to the main thrust of this blog, but I can’t resist saying a few words of clarification for the non-physicists reading this:

          The big advantage of artificial black holes is that they can be created according to physics we all believe in, using technology that we can already begin to imagine. The big disadvantage of the Alcubierre warp drive is that it can only work if some physical theory that we don’t have any evidence for turns out to be true! And that shouldn’t be too surprising, given that the Alcubierre warp drive manages to effectively go faster than light (while cleverly not actually doing so, since it bends spacetime as it goes along).

          Here’s what Louis Crane and Shawn Westmoreland wrote about artificial black holes:

          In a previous paper by the first author, it was proposed that a SBH [subatomic black hole] could be artificially created by firing a huge number of gamma rays from a spherically converging laser. The idea is to pack so much energy into such a small space that a BH will form. An advantage of using photons is that, since they are bosons, there is no Pauli exclusion principle to worry about. Although a laser-powered black hole generator presents huge engineering challenges, the concept appears to be physically sound according to classical general relativity. The Vaidya-Papapetrou metric shows that an imploding spherically symmetric shell of “null dust” can form a black hole (see, e.g., [3], p. 187, or Joshi [10] for further details).

          Since photons have null stress energy just like null dust, a black hole should form if a large aggregate of photons interacts classically with the gravitational field. As long as we are discussing regions of spacetime that are many orders of magnitude larger than the Planck length, we should be outside of the regime of quantum gravity and classical theory should be appropriate. However, the assumption of spherical symmetry is rather special, and an investigation into the sensitivity of the process to imperfections in symmetry is an interesting problem for classical general relativity. If a high degree of spherical symmetry is required, then this could pose serious engineering challenges.

          Since a nuclear laser can convert on the order of 10−3 of its rest mass to radiation, we would need a lasing mass of order 109 tonnes to produce the pulse. This should correspond to a mass of order 1010 tonnes for the whole structure (the size of a small asteroid). Such a structure would be assembled in space near the sun by an army of robots and built out of space-based materials. It is not larger than some structures human beings have already built. The precision required to focus the collapsing electromagnetic wave would be of an order already possible using interferometric methods, but on a truly massive scale.

          This is clearly extremely ambitious, but we do not see it as impossible.

          Exercise: work out the details.

          Of course, all this is a huge distraction from more pressing problems…

  8. Phil Henshaw says:

    Well, maybe we could harnesses the power of perpetual real growth to create limitless real shrinkage too. Anyone thought of that? (-;

  9. I think it is important to look back to Ricardo and find local optimal places for each alternative and then create a global market add mechanisms to existing env trading and also ensure that they connect to the energy grid. The second prerequisite is to agree on an equitable climate solution like the one Pacala presented recently. Then I would choose the best:

    10- wind power as they already are price competitive with fossil fuel, and the same as price as nuclear. 11- PV (GaAs) and the multijunction cells and peek at safe nano films. Plus integrated design building solutions. The economy is a problem right now but its not that far from mass production so ill think it will happen without gov incentives. but gov has to fund storage research in a big way as this is sorely neglected and it can be reused in other energy transforms plus that it achieves utilization gains.

    9 Nuclear fission somewhere in between, because at least where I live they are falling to pieces if nothing is done and David MacKay says if we create U23x non-depletion commitments (eg consumtion rate to last 1000 years globally) at least its a stop gap solution to do seriously needed “maintenance” or tech. upgrade. then we can potentially get a 4 fold increase in stations, iff we can harvest ocean and rivers for U23x. But I would waste problem solved before promoting nuclear further. All storage today is temporary and no one has worked out a satisfying permanent solution (well maybe the italian maffia who allegedly have dumped nuclear waste in the Mediterranean)

    13 – big no-no as long as there is no until we have artifical photosynthesis that ensures that the existing biomass is untouched.

  10. Sailrick says:

    Sorry, but a little off topic again.

    Regarding biofuels from dedicated crops:

    I wonder if it would be a better use of the land to grow plants for bioplastics. (or at least some of the land)
    We use something like 5% of oil to make plastics, which create huge pollution problems like the Pacific gyre garbage patch.

    The most interesting bioplastics technology I’ve heard about is that used by Metabolix. Most bioplastics are PLA or polylactic -acetate. These require several steps of fermentation,distilation, filtering etc. Most of them require pre heating to about 140 F before they are truly compostable.
    Metabolix makes PHA or Polyhydroxyalkanoates. These are created using genetically modified bacteria, that turn the sugars into plastic. Far less steps in this process. The result is completely compostable plastics, even in the ocean.
    Metabolix says they can replace about half the plastics now used.

    http://www.metabolix.com/knowledge/default.aspx?ID=584

    They have built a factory in Iowa, in a joint venture with Archer Daniels Midland, that makes bioplastics from corn. In the future they plan to use non food crops like switchgrass.

    Here’s where is really gets interesting. Metabolix can grow switchgrass with plastic already in the stems and leaves. The plants have not been genetically modified, just the same bacteria which is inserted at some point, I guess in the germinal stage.
    They have done this under a research grant from the federal govt.

  11. [...] covered one about shifting from coal to natural gas, and three about carbon capture and storage. In Part 3 we discussed five involving nuclear power and renewable energy. The last two wedges involve forests [...]

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