Reader’s Forum, Take 1

I try to run a tight ship on comments, keeping discussion focused on the post topic, and in accordance with the discussion policy.  But I sympathize with those who want to go off-road, since the overall topic is vast and has many threads—and I have not discussed some major components of the story yet.  So as a holiday gift to Do the Math readers, I open here a discussion forum open to all topics involving growth, energy, fossil fuels, renewables, nuclear, demand and behaviors, societal hurdles, political facets, visions of the future, etc.  This is your chance to express the big-picture points that may not fit within the narrow confines of ordinary on-topic discussions.

I will reject only comments that I deem to be uncivil, too far from Do the Math concerns, or so lengthy that I don’t have time to screen them (and long screeds also discourage readers and are therefore less likely to be read). If you’re tempted to write a long essay, I highly recommend starting a blog of your own (it’s not really that hard).  Then you can summarize a thesis in a few sentences and point to the larger content elsewhere. So there you have it—now go nuts!

Hits: 5118

140 thoughts on “Reader’s Forum, Take 1

  1. I’ve suggested this before, so hopefully it’s on your list of upcoming posts, but I’d really like to hear your take on passive solar heating.

    For those who don’t know, passive solar heating has a few simple principles that can deliver huge energy savings during the winter months. Have a lot of equator-facing windows (i.e. south in the northern hemisphere and north in the southern hemisphere). Have few windows in the other directions. Use an appropriately-sized overhang to block sun in the warmer months, yet allow sun to shine inside in the cooler months. Have properly-sized thermal mass inside, such as a concrete slab, to absorb heat during the day and release it at night. Insulate well and provide ventilation to prevent air-quality issues. To get things right, it’s worth hiring someone who knows what they’re doing to look over your designs, but the guiding principles are simple.

    In the end, passive solar adds very little, if anything, to the cost of a new home, and payback times on the investment is very quick. I think it’s a shame that so many homes have been built facing the wrong direction for free solar heat.

    • My last townhouse had this by luck I believe. Most of my windows were on the back facing south (Chicago) and there was a deck above the living room windows. During the summer not much light heat go into the living room, but a lot did in winter.

    • A few years back, I even saw that someone had built a house like this in Maine. The house was constructed from Structural Insulated Panels (SIPs), which made the house extra-tight as far as insulating properties go. It was featured in Home Power magazine maybe in 2006 or 07, I think.

    • The key word here is *new*. It’s rarely cost effective (or resource effective) to retrofit an existing home with passive solar features, or to tear down an existing home and build a new one in its place. So passive solar heating might somewhat reduce the energy needs of added population, but that’s about all.

      My 1935 home actually has large south-facing windows with enough overhang to block the summer sun. On sunny winter afternoons, no matter how cold outside, I can stay in the front room with no need to run the furnace. But very little of the heat gets into the rest of the house. What I’d really love is an active solar heating system with rooftop collectors, but designing and installing such a system would be too big a project for me to take on in the foreseeable future.

      • “It’s rarely cost effective (or resource effective) to retrofit an existing home with passive solar features”

        Awnings. They’re called awnings.

      • Yes, I have to agree…… In a previous life I was an energy efficiency assessor for domestic buildings. Most houses are lemons. I initially thought that by using the energy assessing program as a design tool I would be able to establish where the problems are in a house, and work out how to fix them. Unfortunately, it doesn’t quite work like that. Yes you CAN improve a house from a total lemon to something better, but never ever would you be able to morph a lemon into anything as remotely good as our own house is
        Good passive design is a combination of many things being done right from the start – siting, glazing type/size, sealing, insulation, thermal mass, colour of envelope, roof and external wall materials, and eaves design. Get just one of those seriously wrong, and they affect the thermal performance of the entire house…….

  2. Could you do an article about the usefulness of Type IV Fast Integral or Thorium reactors. With all the scare of Fukushima and Germany getting out of nuclear, it would be nice to see some sound numbers.

    I know that it is not long term, but it could be a bridge energy to get us better built for the future. If we plan it to be limited, then that should help us to alleviate the energy trap, right?

    Also, please do NOT do any math against the Tesla S sedan. I cannot afford one yet, but do not want anyone crushing my dream. 🙂

    • Not long term? Compare to light-water reactors, which use about half a percent of the energy potential of uranium (about 80% of the 0.7% of uranium which is U235).

      By contrast, IFRs achieve high burnup on U238, and LFTRs use 99% of thorium because neutron-absorbing fission products are separated out from the liquid fuel. For an extra bonus, thorium is about four times as common as uranium.

      IFRs might be the most long-term solution though because at such high efficiency, it’s worthwhile to extract uranium from seawater, which has plenty (but doesn’t have thorium).

      But what about the energy trap? Let’s look at energy to construct the reactor. A light water reactor has water at 160 atmospheres so it needs high-pressure steel and a giant containment dome. LFTRs and IFRs operate at atmospheric pressure. Lots less metal, much smaller containment.

      And mining? The U.S. has enough thorium already to power the entire country for several decades. We’ve also got plenty of nuclear waste to serve as startup fuel. (The LFTR is better off than IFR in this case, since as a thermal reactor it needs about a tenth as much startup fuel.)

      Barring a fusion breakthrough or cheap solar, these look to me like the only viable long-term solutions to our energy problems.

      Lucky for us, in terms of safety, proliferation, and waste they’re much better than we have now too. (I’m guessing you’re aware of that.)

    • I think it’s clear that nuclear fission COULD be the solution for electricity production. After all, France is already 80% nuclear, and there’s no reason most other countries couldn’t do the same.

      But I just don’t see any advantages for using nuclear rather than a combination of wind and solar. Wind is already cheaper, and solar is getting cheaper all the time, while nuclear plants are actually getting more expensive as we discover new safety concerns that have to be addressed. Constructing the nuclear plants is also a very slow, very carbon-intensive process, while wind and solar can be deployed much more quickly. And if climate change causes more extreme flooding (which it almost certainly will), all coastal nuclear plants will be at risk of meltdown, while the worst that can go wrong with solar is that it simply stops working. Not to mention the risk of nuclear proliferation- do we really want every single nation in the world to have a large scale nuclear program?

      At any rate, the big immediate problem is not electricity, but liquid fuel and fertilizer. That’s what scares me the most, and I don’t see any good solutions there except to simply stop driving and switch entirely to organic farming.

      • “But I just don’t see any advantages for using nuclear rather than a combination of wind and solar”
        Simple point – night.
        Energy storage/distribution isn’t at the point where wind/solar can provide energy 24/7/365.
        Personally, I find that nuclear sounds like a good holding position until we can resolve the storage/distribution problems. (Especially if it is possible to run the baseload above normal requirements and use the “unused” to generate liquid fuel.)

      • GenIII+ designs like the AP-1000 and ESBWR are expected to be pretty inexpensive. They have simpler passive safety systems and are modular so they can be mostly built in factories. Consequently, construction time is down to three years for gigawatt plants, and less for smaller ones.

        Carbon intensity…from steel and concrete? Compare to the amount used for wind turbines and nuclear comes out pretty well. LFTRs would be even better, since they don’t need high-pressure steel or huge containment domes.

        LFTRs and several other advanced designs aren’t water-cooled, so they don’t have to be on the coast, unless you’re using the waste heat to desalinate seawater.

        The biggest carbon emitters are already nuclear powers, and China is already moving to advanced nuclear in a big way. It seems unproductive for the U.S., which has the most nuclear bombs and second-highest emissions, to avoid nuclear power on proliferation concerns.

        However, the best GenIV designs do take proliferation seriously. The IFR, DMSR, and LFTR are designed to be proliferation-resistant, meaning that even if you had those reactors, it’d be easier to make bombs by some other method. With LFTR, after startup you’re not even carting fissile fuels around.

        I think the most immediate problem is to stop burning coal, which is more carbon-intensive than oil. But the heat from nuclear reactors could be used to create fertilizer and synthetic fuel.

        • “… the AP-1000 and ESBWR are expected to be pretty inexpensive. They have simpler passive safety systems and are modular so they can be mostly built in factories. Consequently, construction time is down to three years for gigawatt plants, and less for smaller ones. …”

          While theoretically that could be true, perhaps in China, however it is not even close to reality in the US. For instance, the two AP1000 reactors proposed by Progress for Levy County Florida are now estimated at $22B including transmission, and first design work to first electricity generated may be 14 years (2021). Credit the hurdles thrown up by the US NRC it you like, or the design itself, but it is what it is.

          The containment structure for a GW sized pressure water reactor, including the AP1000, can not be built in a factory.

          • The first ones are always the slowest and most expensive. Modular factory-built design doesn’t help until you’re building a lot of them. (Of course you’re right about the containment.)

            If China succeeds in building the exact same reactors in three years, it’ll be clear that physical and economic limits aren’t the problem here.

    • second that. While I’m opposed to the current version of fission power, I’m very curious about the various new designs out there, be they breeders, traveling wave, or whatnot, and it’s hard finding unbiased reviews of these things that actually use numbers instead of wild handwaving.
      Oh, and I want a Tesla as well, although I’d prefer the roadster, if I could afford it 🙂

  3. I’d really love to hear something about Space-based solar power. Most of the solar power issues that have so far been
    Need to account for power transmission from optimal locations,
    Storage for when “issues” arise
    Night time power
    Life cycle of a single panel
    Space requirements

    But I’d think all/most of these issues go away for a space based panel, so does anyone know why that wouldn’t be a feasible method to go with spaced based solar?

    • Getting the equipment up there. Keeping it functioning up there. Sending the energy back down here.

      Those are three pretty huge problems.

      I find it interesting that almost everybody starts thinking about proposed alternatives by ticking off the positives first, then often times refusing to even acknowledge the most obvious problems.

      • Indeed — and the problems with orbital solar are pretty spectacular.

        We’re well past the time when the EROI of terrestrial PV makes sense — today’s panels produce significantly more over their lifetime than they take to manufacture and install.

        But do you have any idea how much energy it takes to get something into orbit? I’d bet more than just a cup of coffee that, today, it would take more energy to manufacture and launch a PV system than it’ll generate in at least a decade, probably two. And asteroid mining and orbital manufacturing are more science fantasy than science fiction, at least until we solve today’s energy problems.

        Make no mistrake — if we can kick our dependency on fossil fuels, we will one day have a significant space-based solar energy collection system. But I can also guarantee you that we’ll never see such a system until after we’re getting more power from terrestrial solar than from petroleum — and you can imagine how long it’ll take that to happen.



        • You’d lose your cup of coffee Ben – at least according to the theory. The EROI of space solar is actually very good even with existing launch technology IF the rest of the technology worked as planned and lasted as long as planned and blah blah blah.

          Despite which, I’m with you on the near term feasibility. There was a pretty comprehensive report released in November that said it was likely to be technically possible within the next couple of decades:

          But economically competitive? A while. There good alternatives though 🙂

          • The EROEI is nowhere near positive considering the energy requirements to get anything in orbit. I need to see your figures on this as the physics to get anything in orbit is an absolute amount based upon mass and has been known for a long time. Economics is not the issue physics is and it trumps economics every time.

    • these people have a contract in place to deliver such power to PG&E by 2016:

      more accurately, they have a contract where PG&E has agreed to buy the power, IF Solaren can make it available by then.

      Solaren, the vendor of said system, claims the energy delivered by the system could range up to 4.8 Gigawatts.

      we’ll see. i’m skeptical-but-hopeful. should be interesting to follow this project going forward. if they make it work and can make it deliver 4.8GW … well, “space” is a pretty big place. can’t even imagine all the possible downsides from errant microwave transmissions, though …

    • Thanks to Space X’s introduction of egalitarian notions to the space business, we can see their lift costs on their web page. Space X LEO costs are as low as ~$1.5 million per metric ton with the heavy lift vehicle ($80 million / 53 MT) [1]. I assume SBSP needs GEO (?), which cost I can’t find for the Heavy, but for the Atlas payload is cut in half LEO to GEO, so perhaps Space X to GEO is $3 million per metric ton. In SBSP array designs making heavy use of lightweight reflective materials (and low EROEI) to concentrate on PV, I see estimates in the range of 3 kg/kw to 0.3 kg/kw [2]. This yields, say, a 4 GW (output at orbit) SBSP array at ~4000 metric tons and $12B in lift costs ($3/W). Lift off.

      [2] 2007 Report to the NSSO, page 31

      • and how many years to repay the energy investment of constructing and launching the system in the first place? this is “the energy trap” in a microcosm.

        • I assumed that the claimed 1 kg/KW claim made it obvious that the ERoEI was high. Quick look:

          If I naively (?) assume that the launch energy to GEO (~40k km) is just potential energy (m*g*h), then I have 400 million joules per kg or 110 kwh per kg, i.e the payback (for launch only) is a matter of weeks, not years.

          • 1) I’m willing to bet that being naive with the assumption of 100% efficiency in lifting is masking a massive issue. How much energy does it take to construct and launch the vehicle, let alone generate the fuel?

            2) How much energy does it take to construct the SPS itself?

            3) Is this taking into account solar panel degradation over the lifetime of the system?

            Honestly, I want to believe in space solar (really really badly!), but I’m not convinced that the solution, for large-scale civil power generation, is superior to the application of existing technologies.

          • I’ll just throw in a knee-jerk reaction to solar in space. What it buys you is a factor of 5 greater energy production and can eliminate intermittency. What it costs you is launching panels into space (if none of you have ever tried this, note that it’s hard), herding cats in space, collecting the power from lots of panels into a transmitter, a huge dish for microwave transmission, spectacular—never errant—aim, and then the collection/distribution system on the ground. My reaction is not so much that these things can’t be dealt with. But compared to buying five times more panels for the ground and working out a storage scheme to cope with intermittency, the space approach seems ludicrously complex and expensive for not that much gain.

    • I too am waiting for Tom’s take on Nuclear. I agree that only Nuclear and Solar/Wind can deal with our energy scale.

      My take on LFTR, IFR, New Designs, Etc. is that it does not change the fundamental issue of Nuclear power. The overwhelming numbers of possible failure modes. This is what causes the mushrooming numbers of safety systems, 4′ concrete domes, Generator backup after Generator backup, etc.

      If the claim is that LFTR is cheaper, what the promoters really claim is the vast majority of safety systems now in use can be abandoned. I don’t think this is true. Spilling radioactive salt on concrete floor and sending some one in to scoop it up with a shovel is not an acceptable failure mode. Almost certainly lead to abandonment of facility.

      That fluorine chemical plant operating on 1000 MW reactor at 700f-900f gives me some serious chills. The containment for that would have to be monstrous. Meaning Expensive. Doable, but not economically practical. Esp. in world of Sub 10 cents/kwh of PV electricity.

      • So don’t arrange things that way. It’s already got an emergency drain into a passive cooling tank. Let the floor drain into that same tank.

        We do a lot of large-scale fluorine chemistry already, and some people in that industry are getting very interested in LFTRs.

        • Yes certainly that is possible. But at the cost of contaminating concrete and turning that area into a long term hazard zone. How do you now get in there to fix what ever caused the leak in the first place.

          And see we are already adding another layer of backup safety. I’m sorry, I think all of this is doable, just not economically.

          WRT fluorine, I don’t think there are any/many? industrial processes that deal with it at 700f and with radioactive traces mixed in as well. We would be on the bleeding edge there.

          Again, probably doable, it is the economics that I question.

  4. I’d be interested in seeing people’s comments and ideas on electric cars, ala the thread Tom stopped in the post on hydro-electric.

    My view is that, if EVs get pushed in a context where overall transition and reconstruction aren’t being acknowledged and addressed, the EV will prove to be a disaster, a major factor in worsening the overall energy trap problem. If we squander a huge share of the planet’s lithium and also remodel the electrical grid to cater to EVs with existing sprawl, we will wind up being very sorry about it.

    Why is that wrong?

    • 1. EV’s use three to four less energy per distance traveled than do the combustion vehicles on the road today. 2. EV’s emit zero pollution at the point of use (at least), typically urban areas where it matters most. So regardless of what political policy one prefers for managing the number of automobiles or their size, the EV is a better choice from stand point of energy use and pollution.

      With regards to the grid, it is fairly easy to bound the transportation load converted to electric power. The US currently uses some 378 million gallons of gasoline per day. That’s 4.54*10^16 joules per day, or an energy use rate of 485 GW. But EV’s need a fourth of that or less to travel the same distance, so we end up with a load of ~121 GWe, maybe 140 GWe before charging losses, to completely replace US gasoline consumption. Total US average electric generation is about ~450 GWe, with a total capacity of over 1000 GWe. I have skipped diesel and kerosene consumption, and there won’t be an even distribution of over capacity everywhere causing some local bottlenecks. But generally speaking the US grid can handle a mostly electric US automobile fleet, as is, should it ever become practical enough for widespread adoption (i.e. solve range, cost, charge time, temperature sensitivity, etc).

      • I agree that as long as EVs are charged even marginally intelligently during off-peak hours, the grid of most civilized countries should be able to cope with it.
        That is of course only true with current generation capacity, where baseload is provided by nuclear and coal and available around the clock. I’m not so sure this holds true once the majority of generation capacity is wind and solar, because then we have squat at night. Using EVs then will require significant investments and change in infrastructure: e.g. charging stations in employer parking lots, including metering, standardized and compatible vehicle-to-grid or at least vehicle-to-home systems so we can use those big batteries to power the TV and fridge at night…

      • I don’t dispute that EVs use less energy per mile traveled, even including the losses involved in generation and transmission of the electricity. What I dispute is that better is anywhere close to good enough in this crucial area. How do you imagine 200 million electric cars not being a huge waste of precious resources, and a major mis-shaper of the electricity distribution system?

        Noticed you also don’t mention the question of Peak Lithium.

    • While I think EVs as such are awesome, and I would love to drive one (the Tesla roadster is ridiculously fun to drive, and getting back into a gas guzzler afterwards feels sooo last millenium),
      I also believe the EV is merely the lesser of two evils, both economically and ecologically speaking. While an EV is better for commuting than a regular car, it is simply insane to lug around two tons of metal and batteries when you really just want to move a <100kg bag of water. For short distances without luggage and for just one passenger almost any means of transportation is better than a full-size car: Bicycle, motorbike, public transport, segway, walking, ultra-compact one- or two-passenger vehicles. Power any of those any way you like, you still come out ahead financially and environmentally compared with a full-size car, even if it runs on batteries.
      And for long distance travel with luggage and multiple passengers there is no feasible replacement for internal combustion engines with liquid fuels on the horizon.
      In short: Full-size EVs are nice, but objectively speaking their niche is rather small. Most of their potential use scenarios would be better filled with bikes, electric scooters and public transport. Still beats commuting in a Hummer though.

      • Or Renault Twizy equivalents – cheap, weather protected, airbags, fully electric, 1.5 seater and able to do around 120kph. Going on sale next year 🙂

        For long distance – electric trains are pretty good. I’m interested to see if they’re combined with electric cars at some point in a roll-on-roll-off way.

        • There is also another tandem-seating car, the Volkswagen 1L or 1-liter. It’s also a lightweight car with only two seats, one in front of the other. It gets 230mpg, because of reduced frontal area, reduced drag, and reduced weight.

          • Yup – anotherof my favourites; but last I saw VW were shifting away from the truly niche vehicle and startingto go for highway range and speed, side-by-side seating… And still no clear production date. Also not cheap. But a brillian vehicle and I’m sure it’ll come eventually. Nissan land-glider. GM en-v. Audi recentlyshoweda similar ultra compac electric.These are the vehicles of the future city and I can’t wait! Cheap, efficient, clean, and hopefully self driving before too long…

          • Don’t even get me started about Volkwagen: The discontinued Lupo 3L, that 1L car, they also had a really nice EV study that worked exactly like the Volt, long before the Volt…
            They all share one flaw: You can’t actually buy them. Now they have been beaten to market by GM/Opel and Citroen/Nissan.
            Don’t put your hopes in VW, they are definitely not leaders in sustainable transportation. Sad sad story for German engineering, really.

        • I wrote “long distance with luggage and multiple passengers”, and with luggage I mean things which don’t fit on a train and which you want to get to places where trains don’t go. Think windsurfing stuff for example. Or going to remote places in general. I see no alternative to ICE and liquid fuels there.
          That problem may of course solve itself by these activities simply becoming unaffordable due to their wasteful nature in the first place.

  5. Given that Tom’s math points out again and again something that’s been obvious to anyone who’s run the numbers since King Hubbert’s day – that the energy density of oil provided the environment within which modern ‘developed’ civilization evolved and that, given the finite nature of the planet, this energy density environment will at some point decline in available BTU / kWh / Joules to the point everything we expect and take for granted as an energy baseline is ‘wrong,’ and given that technological progress is only possible through the use of energy and therefore doesn’t really create it, what do you personally plan to do to actually survive the oil decline and depletion era the majority of the data indicate has arrived, or will arrive in your lifetime?

    • Three things, really.

      1. Try to personally live within a reasonable 2030 global average when it comes to not only energy but also water, land use, etc.

      2. Work on solutions that will allow us to maintain at least the 2kw/person consumption globally in a very low impact manner – as I do believe this is possible in terms of basic energy density (solar pv would easily support such a level of consumption)

      3. Try to improve my knowledge and understanding of other cultures and areas, and a global sense of community, so that when the inevitable problems come (as they already are) we are more inclined to work as a team to prevail, rather than descending into resource conflict/war and societal collapse.

      4. Enjoy life while I’ve got it, within the sustainable living envelope above 🙂 Details on my blog (click my name if interested).

      Fingers crossed eh?

  6. There is always a lot of talk about global inequality. We tend to talk about it in terms of dollars. I can easily look up global GDP per capita for 2010 via google and find that it is $9,200/person (£5,700). So, if I were to receive only my “fair” share, I can easily see that I’m in for some lifestyle change since the rent on my flat would consume most of that “income”. When you put a money amount on the issue, you can get a picture of life on your fair share because we are all used to the idea of price. However, I suspect that this doesn’t tell the whole story, since energy used is probably a very minor component in the rental price of my small flat.

    If you look up per capita energy use I find a figure for 2008 of 1839 kg oil equivilent, but it is meaningless to me. What does my fair share energy budget buy me? Can I run a car, moped, bicycle or do I have to walk, etc?

    Would very interested on your take on global energy inequality, leaving aside the issues of peak oil, etc.

    Got the data from here:

    • What’s the payoff on the invention of modern medicine and the tripling of lifetimes? The invention of modern engineering, the cell phone and satellite communications?

    • Tali – this is a perfect question to be asking yourself to make sure the changes you might make to your lifestyle will actually have an impact.

      I find (and quite a few others agree) that calculating things in terms of continuous power delivery is the best way to get a feel for this. A kg of oil is an incredibly messy (both literally and analytically!) unit – on the other hand a ‘watt’, once you get used to it, is easy to compare between wind, oil, solar, coal, etc.

      In terms of the sort of life we can buy for ourselves with our fair share of energy, Saul Giffith did a great presentation at ‘longnow’ called ‘climate change recalculated, which details his search for the answer in his life. It’s quite long though. For a shorter overview, check out my blog post on the topic here: which also includes a link to the wattzon website where you can calculate the numbers for your own life.

      Put simply, your 2030 ‘fair share’ by current forecasts is around 2kw. Today, I can have food, living, and land transport for around 1.5 kW. I totally blow the budget when flying is included though. Then there is government consumption on my behalf to consider. But it definitely doesn’t require living like a hermit in a hut made from sticks and handspun moss 🙂

    • The degree of waste in modern capitalism is staggering. The chief form is cars-and-suburbs, but the problem is also huge in food distribution, packaging, etc. I’m not worried about living well in a sane world. I’m worried about cracking the power structure enough to get sanity onto the agenda.

  7. Energy 2050: The Future of Energy is on Discovery Channel right now.

    • Hi George,

      I took a quick look at this. It is not so different conceptually from solar updraft towers. A number of these have been built, see:

      Some of the assumptions in Alan’s idea are flawed – his proposal is not a closed system and the theoretical maximum thermal efficiency will be limited by the high and low temperature thermal reservoirs (the high temp one is the temp of the solar absorber, and the low temp is the ambient environment (ground, air, whatever) that the circulating warm air transfers heat to in order to become cooler air and sink.

      With the proposed layout the air is unlikely to get warmer than 100deg C, nor cooler than 25deg C. This alone would limit the maximum theoretical efficiency to around 20%… So already no better than solar pv. The practical efficiency would suffer from numerous other losses and inefficiencies (turbulence, mixing, the turbine, etc).

      So, simply put, the math suggests that it’s not a remotely competitive solution when put up against, e.g. Solar pv. Certainly it will not give a high efficiency with any if the proposed architectures (my 20% above is probably extremely generous)

    • While those may all work to some degree, the basic premise that they are not carnot-limited is simply wrong. They are all still heat engines, even if no gas exchange with the outside takes place, just as e.g. in a stirling engine. The gas needs to cool on the way down, this will happen by exchanging heat with the outside, thus you are operating between the heat bath of the hot absorber and the ambient temperature outside.
      Those proposals are all conceptually similar to the solar updraft tower:
      The only difference is the completely closed volume, which will make efficiency much worse instead of better, since heat exchange at the cold end becomes harder.

  8. From the poorly written description it looks more like a thermal updraft chimney than anything else. They get about 2-3% efficiency.

  9. When we consider a future with very limited FF availability we tend to forget that because present energy is so cheap there is a wide range in types of energy use.
    To illustrate, take electricity consumption. The electricity used to power a refrigerator, or lighting or to re-charge a mobile phone is very valuable and most people would be prepared to pay much higher prices to ensure that have this available. On the other hand using electricity to keep all the rooms in a house at <20C or to run a cloths dryer are low value uses. if electricity was X10 more expensive few would consider these applications.
    Similarly oil based fuels are so cheap we presently use them to holiday around the world or to drive monster SUVs that have very high fuel demands. Reducing gasoline consumption by 50-75% is no more difficult that replacing 50mpg vehicles or now that PHEVs are available driving a vehicle that uses almost no gasoline. This is without considering car pooling or reducing the number of non-essential trips or using mass-transit.
    I think it should be clear that a combination of solar, wind and hydro at todays costs is more than adequate to provide most of the high value energy needs of the worlds population. If this means that gasoline is going to be X4 or even X10 more expensive than it is today, and only 25% of todays consumption is possible is that really going to be a big adjustment.?

    • Sadly, you’re overlooking what a quadrupling of petroleum prices would do to food prices, or what an order-of-magnitude increase would do to food production. If something like that happens at a pace faster than we can transition to non-petroleum-based agriculture, there will be mass starvation and accompanying global chaos.

      Sure, I already drive so little that I could afford to pay ten times as much for gasoline, though I’m so far off the left side of that bell curve it’s meaningless. But even I would be mighty uncomfortable if I had to pay four times as much for food. And, at those prices, I’d have to pay for my (retired, living on Social Security) parents’s food (since there’s no way they’d be able to afford to eat otherwise)…and that would leave me with damned little (if any) discretionary income.

      Now, consider that I’m quite well off, thankyouverymuch. The one thing I know for certain is that that’s not something I’ll have to worry about, because the food riots will wipe out civilization as we know it long before it gets that bad.

      I’d like to think that we’ll avoid that fate, though I’m under no illusion that the transition to a post-petroleum society will be an easy one. My hope is that we’ve got enough remaining petroleum to get us there and that reduced demand (through increasing use of alternates as well as global recession caused by rising energy prices if nothing else) will work to soften the transition. But, if I’m worng, running your clothes dryer will be the least of your worries.



      • Ben,
        The increase in oil prices will have an uneven influence on food prices. Most oil is used to transport food to processors and then to transport those products to supermarkets. The biggest energy inputs are storing food in refrigerators and cooking as well as driving to supermarkets in a 2 tonne vehicle to pick up 50lbs of food.
        Actually growing food in US uses about 1% of oil consumption, with considerable natural gas used for fertilizer production. Reduced till agriculture uses a lot less fuel than in the past when oil was one tenth todays price. Providing NG remains available agriculture could easily transition away from oil, replacing diesel with CNG, but this would not make sense while we have 200million oil consuming private vehicles..

      • Ben,

        “Sadly, you’re overlooking what a quadrupling of petroleum prices would do to food prices…But even I would be mighty uncomfortable if I had to pay four times as much for food.”

        A quadrupling of petroleum prices wouldn’t cause a quadrupling of food prices, unless 100% of the retail cost of food were devoted to buying petroleum. In fact, only a small fraction of the cost of food goes to pay for petroleum, so food prices would increase only modestly even with drastic increases in petroleum prices.

        Bear in mind that the economy will sacrifice the least important uses of petroleum first as supplies of petroleum decline. We won’t sacrifice food production until supplies of petroleum have already declined by more than 80%.

        “…though I’m under no illusion that the transition to a post-petroleum society will be an easy one”

        The transition to a post-petroleum society will be an extremely gradual one. Petroleum output over large geographic regions changes extremely gradually. For example, North American oil production has been on a plateau for 3 decades, with new sources coming online as old ones are depleted; and the same is true for every large oil producing region in the world.

        We’ll still have 60% of today’s petroleum output in 2100. That’s long enough to adjust; in fact it’s much longer than most of suburbia has existed.

        • You’re making concrete predictions about our future path, without crucial qualifiers of “I think,” “perhaps,” “likely,” etc. This always sets off the alarm bells for me. Certainty in the face of a transition unlike any that humans have experienced is, in my mind, misplaced. The notion that we will smoothly and gradually adapt to a new phase of fossil fuel decline seems to overlook reactions rooted in human psychology: hoarding, resource wars, panic, willful denial, ideologically-driven (irrational) reactions, etc. We can’t know how these things will play out, so a statement about what will be happening in 2100 is nearly worthless. For me, only by acknowledging that we’re about to hit an unprecedented challenge—with the possibility of collapse—are we an any position to take actions and make statements about our ability to avoid such a fate.

          • I am definitely not intending to make concrete predictions about our future. Perhaps I should’ve added more qualifiers.

            I don’t know what is going to happen in the future. For all I know, gasoline prices could rise to $4.50/gallon in the US, causing voters to rebel and elect some aggressive republican president, who invades the Middle East, which touches off a war that ultimately ruins everything. In fact, this scenario could conceivably happen even if oil supplies don’t decline and prices remain low. For example, oil prices were quite low in the US when the necons rose to power and decided to invade Iraq. Also we invaded Afghanistan because 12 guys with box cutters crashed several airplanes. There is no way to predict such outcomes which I know about. I’m not even sure that higher oil prices would make such outcomes likelier.

            What I am saying, however, is that there is no current model or trend which implies an inevitable energy descent or collapse of civilization. The models which imply that are, in my opinion, all totally wrong.

            If trends continue as they are, and oil declines at the expected 1-2% per year, and the economy adjusts at the same rate that it always adjusts, then we do not face collapse because of declining energy supplies. Of course there could always be a “black swan” event which changes everything, but there is no inevitable trend to collapse which we know about.

          • Economists have become complacent with extrapolation into the future, which I will admit has worked very well in the past. I worry about a phase transition that invalidates BAU thinking and incrementalism. I therefore place little faith in trends. When energy gets hard, everything gets hard. Even when energy is just 5–10% of the GDP, the other 90% relies so heavily on energy to remain at 5–10% that we may not appreciate how big a game-changer we may be looking at. The more someone tells me not to worry—that trends are fine and there is no rationale for imagining collapse, the more scared I become. Normally I’m not like this, but in this case I see quantifiable, physical evidence for impending hardship—while not witnessing enough acknowledgment of the possibility to assure me that we’re taking this thing seriously enough. Instead, the message is to sit back and watch it all work itself out by the usual market means. My scientific skepticism does not allow me to make that leap of faith in the face of the obvious scarcity to come.

            Since we’ve had a bit of back and forth on this, I can imagine we are capable of playing tennis for quite some time. But I’m unlikely to have time to play, so am inclined to leave it here.

          • tmurphy,

            “Certainty in the face of a transition unlike any that humans have experienced is, in my mind, misplaced.”

            Why is this transition unlike any that humans have experienced? In 120 years, we have transitioned from coal-fired reciprocating steam engines, to coal-fired steam turbines (which are quite different), to internal combustion reciprocating engines powered by oil derived from mule-type wells, to offshore oil drilling, to combined-cycle turbines powered by natural gas (which was a waste product 50 years ago), to fracking. We transitioned from town gas (a coal byproduct; almost all “gas” delivered to homes before WW2 was town gas) to natural gas during the 1960s. My own state (California) gets no power from coal anymore, for any purpose. Some countries transitioned from coal to nuclear, which took them about 25 years. Along the way, almost everyone added a lot of hydropower.

            Why is this transition, from coal to (say) solar thermal, so terribly different? Because there is no fossil fuel?

            But a solar thermal plant is identical in many respects to a coal-powered plant, even using the same model of steam turbine on many occasions. The big difference is that solar thermal plants use sunlight and mirrors to boil the water instead of coal. In many ways, this is less of a transition than any we’ve undergone.

            In fact, many modern solar thermal plants will accept almost any heat source to boil the water. If the sun is not shining then you can put a natural gas furnace beneath the molten salt reservoir, or an oil-burning furnace, or something else. The source of heat isn’t that important, as long as it’s concentrated enough to increase the temperature of molten salt to a certain degree. In that case we could transition quite rapidly, based upon changing prices.

            Perhaps you are referring only to transitioning off liquid fuels for transportation? I admit that that transition is more difficult. However, the transition TO gasoline and diesel was almost entirely a post-WWII phenomenon. Most of it happened within 40 years. None of this is that old. The highway system was Eisenhower’s idea.

            By the way, I really appreciate your informative blog and this interesting discussion.

          • The transitions you note were due to improvements that made old ways obsolete, rather than a forced transition due to resource shortages. We aren’t itching to go to wind, solar, etc. because they are obviously superior. They come with drawbacks in economic and practical terms. Transitions to something vastly better (gasoline powered ICE) catch like wildfire. I think we’re staring at a new class. And I see loads of ways to produce electricity—I’m not too worried about this, modulo the storage question. It’s our transportation I worry about, and the degree to which so much of what we’ve built assumes cheap and rapid transportation will be available. To say that a downside transition is little different than an upside transition (ascending energy availability) does not resonate with me.

          • And the problem is not only the transition, but the dependence of our socio-economic elites on easy energy. If they begin to tolerate serious discussion of this dependence, their powers and privileges are in dire danger. Hence, they and their institutions are working, and will continue to work, against such a discussion, not least by peddling a series of false alternatives when the topic forces its way to attention.

            As Fred Douglass said, power concedes nothing without a demand.

  10. WRT pumped storage the Army Core of Engineers did a comprehensive study of all possible sites and published it in their report ‘An assessment of Hydroelectric Pumped storage’, Dames and Moore, 1982.

    From the report it appears COE looked at ‘feasible’ sites between valleys with a minimum head of 700′ and production of at least 1000 MW for 16 hours (uncertain). They thought this would be the most economical. Results kinda back you up.

    Only 3 regions have significant potential though an exhaustive survey had not been done in many areas.

    N.East – 49,400 MW
    N.Central – 8,589 MW
    P. NorthWest – 650,000 MW
    P. Southwest – 341,100 MW

    All other regions are under 5000 MW in potential.

    Of course if you went lower head and capacity the number of sites mushrooms astronomically. They estimated roughly 200,000 sites with more than a 1 MW for 16 hour (uncertain) capacity spread much more evenly across the country. Again the survey was not exhaustive and many regions only have a lower limit number.

    • And from what I can tell from perusing the report, the Core did not consider coastline power installation possibilities, perhaps because of the “Coastal Zone Management Act of 72,76” referenced therein. Plenty of coastal cliffs in Maine for instance that would provide ample head. I don’t want to see any Maine cliffs torn up, but the plant’s reservoir could be stood off quite a distance from shore, never touching shorelines such as Bar Harbor aside from underwater intakes.

  11. Here’s to hoping Tom does the next article on Nuclear. There is a lot of talk about Thorium and IFR reactors, and many of the claims appear “too good to be true”. So I’m very curious to get his take on the math.

  12. I’d really like to see some calculations for the scalability of concentrating solar power (CSP) projects such as Desertec.

  13. Couple of comments about the ‘energy trap’ post.

    Several assumptions are questionable:

    First, we already invest in energy replacement all the time (oil exploration for instance, plus building renewables & new power plants) so assuming a sudden 8% investment will be needed seems excessive.
    Second, the EROEI of replacements may be much higher than 10:1. Solar thin film may already be up to 40:1 and with new technology that could easily increase. This will make the ‘trap’ much less.
    Third, the calculations don’t seem to take into account that as the declining infrastructure is replaced, the replacements won’t be declining. For example, at 2% replacement per year, after 25 years half of your energy supply has been replaced with stuff that is not declining. So your effective decline rate overall is down to 1%. After 50 years, it is zero. Or am I reading it wrong?

    • Sadly Solar panels do have a life. Even if it is very long. But after 25 years large sections would need replacing. After 40 years probably all of them must be replaced.

        • It’s not the silicon, it’s the packaging (which is mostly oil-based laminates and adhesives) that keep the water out over 40 years of -4- to +90 wet high UV environment exposure …

        • That is only true after you you factor in the first year drop of 2%-5%. After that the silicon itself is rarely a problem. It is all the other bits that cause issues. yellowing, laminate problems, corrosion, solder bond weakening, etc make maintenance too expensive for large plants. Many plan and budget a regular schedule of removing large sections as preemptive maintenance. Solaire for instance plans full replacement after 15 years so its plants don’t start deteriorating in output. It also does it to rotate in new technology into high value space.

          Only a few long term 20 years + panel systems exist. The Swiss have published several excellent reports on their TISO installation (1982) which showed that panel damage was accelerating after 20 years even if performance was only marginally being degraded at ~ -3.0%.

      • As an interesting aside, the lifetime of mirrors and other equipment for concentrating solar power has been subject to an experiment. During the Carter administration, the DOE devoted money to building a CSP plant (called SEGS) in the Mojave desert. After Reagan took office, funding for the plant was terminated, and management decided that they would spend no money on upkeep or on replacing mirrors unless they could fund it with the sale of electricity. Since CSP is not price-competitive, they basically decided that they would allow the plant to decay, and replace the turbines etc only. Now, 30 years later, it’s a mess, with broken mirrors here and there. Still, it continues to run.

        • By the way, mirrors for CSP do have a limited lifetime because sandstorms are gradually abrading them.

          • I’m curious as to the expected lifetime of solar PV and mirror concentration in *space*. No dust or water or temperature changes, but UV and other radiation loads must take their toll.

          • Not to mention micrometeorites, space junk, solar wind, solar flares, attitude/altitude correction fuel, etc.

  14. My apologies that I’ve been too busy to participate in the forum. And I may not get much chance for moderation today, so don’t worry if your comment isn’t showing up promptly…

  15. More on biofuels and hard-to-extract fossil fuels; especially EROI and the minimum level that a complex society can survive on without collapsing (it’s somewhere between 3:1 and 8:1 but it’s not clear)? I.e. the work of Prof. Charlie Hall at Syracuse and others and its relation to the work of Prof Tainter (The Collapse of Complex Societies).

    • I don’t think there’s any straightforward mathematical calculation which will tell us whether civilization will collapse or not. That would require complicated analyses of all possible energy alternatives, plus analyses of the rates at which capital equipment can be used to produce new capital equipment (which limits the rate of adjustment). There is no straightforward calculation of physics which would yield an answer. It would require a complicated model.

      The economy is a non-linear system which does not progress according to any continuous mathematical function. Beware of any analysis (like Limits to Growth or others) which shows smooth mathematical curves for “the economy” or “complexity” or “civilization” or “industrial production,” alongside curves of oil supplies or some other physical resource. Such graphs mislead and confuse, much more than they illuminate. The economy is not a variable, and does not equal oil supplies or anything else. Furthermore, industrial production is not a single thing and does not equal oil supplies or any other single resource, even if it has tracked oil supplies (or some other resource) closely thus far.

      It would be better to think of the economy as a computer algorithm which is ALWAYS searching, re-balancing and re-adjusting. It will collapse from energy descent only when there are NO POSSIBLE remaining means of acquiring enough net energy to sustain itself, and when ALL the inessential uses of energy have already been sacrificed.

      I should admit outright, that I’m a student of economics. I’m aware that many people around here think that everything I say will be 100% bullshit (not that I mind). I just thought I should let you know where I’m coming from.

      • “It would be better to think of the economy as a computer algorithm which is ALWAYS searching, re-balancing and re-adjusting. It will collapse from energy descent only when there are NO POSSIBLE remaining means of acquiring enough net energy to sustain itself, and when ALL the inessential uses of energy have already been sacrificed….”

        I agree this is likely the case with a modern market economy. My concern lies with the constant call to do away with the market and replace it with a centrally planned, forced economy under the guise of a “nudge” or similar platitudes, causing the loss of that constant re-balancing and searching. In the case of the fallback to a centrally planned (attempt at an) economy then collapse really does become inevitable, if history is any guide (Mayans, Soviets, N. Korea ).

        • Jared Diamonds book ‘Collapse’ is a really interesting discussion and historical review of this topic. Basically the point ends up being that the conditions leading to, and non-linearities around, collapse are extremely hard to predict and can strike very quickly… with the qualifier that almost all historical collapse has been the result of over depletion of some environmental service/resource. So basically the current fossil fuel /climate thing does not bode well.

        • Well I certainly am neither in favour of a market economy nor a centrally planned one… I believe we will go back to a totally decentralised and relocalised economy where everything is made and traded within walking/cycling distance! Might take 10 or 20 years, but it’s coming because there is little choice post fossil fuels.

      • If this site had a like button I’d be clicking it for your comment here Tom. Economics and social dynamics are going to have at least as big an impact as physics in determining the path we follow.

        The nice thing about the physics is that if you can get enough people to believe in the technicall viable solution then they might align with it which makes it economically and socially viable by virtue of acceptance… Basically changing the gains on the market appetite in your model.

      • “I don’t think there’s any straightforward mathematical calculation which will tell us whether civilization will collapse or not.”
        Agree absolutely, but the subject is surely so important that attempts to calculate upper and lower bounds should be attempted – to help identify futile efforts such as corn ethanol or shale oil?

        “Limits to Growth”, after all, despite its shortcomings has been quite correct in highlighting resource shortages, which neoclassical economists always denied. If that pioneering work had been taken on board a bit more and developed further over the years, maybe we would be in a better position?

  16. Is there a sustainable energy forum that isn’t run by a business and isn’t populated with free energy kooks and conmen? My brain craves a “Do the Math” forum modeled after this blog.

    • Sustainable energy realities and discussion forums which honestly reflect them seem so weak -when compared with the way things are now for most people with an Internet connection – that only hucksters and kooks have the personal energy to moderate and the cash to pay for them. Sites like Tom’s are rare.

      Here’s the Occam’s Razor of our future: “If you weren’t living and thriving there in 1850, you won’t be living and thriving there in 2050.” Oh, and you’d better be knowledgeable in the skills of 1850’s agriCULTURE, and other cultures, delivering more work than you consume, in a tight knit, resource and energy sufficient community.

      The future will be fine. The transition to it over the next 50 years, from a world where there are 10 kCal of oil and gas energy in each kCal of nutritive energy, to pre-oil ag and energy reality for the bottom 99% of a much smaller population base, is going to be difficult. Read “Two Years Before the Mast” by Richard Henry Dana … a great book about maritime work and life in 1830 — when written; a work of social activism then and today, a really good glimpse backwards into a wind and solar powered world.

    • That’s changing – the forecast is for 35y life by 2020, meaning the panels will still be generating 80% of nominal after that time. Even today several manufacturers are offering 25y warranties (for what they’re worth).

  17. On Nuclear:

    The hardest part of ‘doing the math’ here is not the total economic production potential (which, with advanced reactors I.e. breeder etc, is very high).

    The hard part is accurately assessing risk. I used to be a huge gen-IV nuclear fan as the only realistic solution. I mean you see numbers like ‘one in 500mil years’ as cooling system failure rates and are inclined to think ‘absolutely safe’.

    The real world significance of those numbers is minimal though. Firstly, they’re just guesses really. Secondly, they assume perfect maintenance. No terrorist attacks, no societal decay. Fukushima was KNOWN to be unsafe and wasn’t improved! If you look through the list of actual reported accidents in nuclear plants over the last half century they chill your blood.

    This is what puts me most strongly in favour of solar – I think it’s possible, and the worst case scenario is pretty benign. Nuclear is also possible, but the worst case scenario is terrible and it’s extremely difficult to tell what the probability of occurrence is.

  18. I would also like to see Tom’s take on thorium. So often it seems people hear something like “thorium nuclear reactor” and immediately throw it in with conventional reactors and dismiss it out of hand. The designs for a LFTR are much cheaper because they do not need a thick containment dome, or multiple backups, or various other safety features associated with a pressurized light water reactor. Though people tend to think that this means a LFTR is just as potentially dangerous as a PWR when in fact by the very nature of having a dense liquid fuel operating at atmospheric pressure it is inherently safer. Not to mention being much more fuel efficient with relatively abundant fuel, not nearly as much waste is produced, and having virtually no risk for proliferation of fissile materials.

    For anyone interested in learning more here are a few sites about thorium and its potential:

    • I’ve posted before on this. But there Zero chance of a LFTR being built without a containment dome and safety systems for every possible failure mode. This is the assumption LFTR supporter make that has very dubious probability of happening. Spilling radioactive salt on concrete will never be an acceptable failure mode. Safety systems will have to be designed to prevent this from ever happening.

      That ‘Hot’ fluorine gas plant is another potential monster needing containment and safety system over safety system.

      Energy wise doable, but economically the costs will continue to spiral as it does for nuclear now.

      • And rightly so. A lot of this ‘inherently safe’ stuff is really a bit disingenuous. I mean calling something inherently safe just because it doesn’t need active cooling? That’s just safer – not inherently safe. Freeze plugs can still block. So can vents (for example – with tsunami debris… Chance in a billion though right?).

        In the current circumstances I’d prefer nukes to coal. But to solar?

        Should be a no brainer in a decade or two anyway…

      • The problem with containment in solid fuel pressure water reactors is not the containment itself but it’s size. The use of high pressure, high temperature water means the expansion to steam in the event of a leak will use several orders of magnitude more than original volume. This economically precludes, among other things, building PWRs underground. Containment for a molten salt reactor on the other hand can be just larger than the reactor vessel and opens up the possibility of underground MSRs.

        • Point well taken. The conventional Reactor Vessel itself might be relatively small.

          But the size of modern containment domes is also due to the need to keep the coolant loops under containment and to to keep things like the Fluorine gas ‘processing plant’ under containment as well. Fluorine gas explosions are quite common in the chemical industry and have an intensity scale all their own. That dome will have to be quite substantial. I don’t see a substantial cost savings here. In construction going a 40 meter dome to a 30 meter dome may produce less savings than you think.

          Due to the nature of the beast additional safety measures will have to be taken WRT LFTR that are not necessary with present reactors. For instance certain configurations of the Graphite core produce a positive reactor coefficient. A whole slew of safety systems will be necessary to deal with this. Or for that matter hot fluoride salts are corrosive even to Hastelloy. Some projections have the piping being inspected and replaced every 5-10 years.

          • “Due to the nature of the beast additional safety measures will have to be taken WRT LFTR that are not necessary with present reactors. For instance certain configurations of the Graphite core produce a positive reactor coefficient. A whole slew of safety systems will be necessary to deal with this.”

            There may be a way to build positive reactivity coefficient LFTR, but there certainly is a way to build one with a strongly negative coefficient. Nobody is going chose the former anymore than they’d chose to hit themselves in the head with hammer.

            With regards to replacing reactor plumbing every ten years, I don’t know that this is the case but, assuming it is, so what? The expensive thing about the PWR is the ‘P’ part, 300 ATM of pressure, requiring 15,000 ton castings with 250 mm walls. A molten salt reactor runs at little more than its head pressure from the depth of the salt pool.

          • Makes it very expensive. Hastelloy is not cheap. Why would you even get yourself into such a situation where you don’t even know how long the piping will hold out.

            There are large economic advantages with going the graphite route with positive coefficient.

            Again, for the sake of safety a more expensive and safety system laden route will be chosen.

            I don’t see this being cheaper than conventional pressurized U-235 once thru.

    • Dmunger,

      First I should mention that I’m an amateur when it comes to nuclear engineering. I love reading about all things nuclear but I’m not a professional.

      With that said, I don’t believe that thorium reactors are meltdown-proof or could forego the complicated and expensive safety equipment of modern nuclear reactors. Bear in mind that most nuclear accidents are not runaway fission reactions. The biggest dangers of nuclear reactors are decay heat problems.

      I don’t believe that liquid fuel reactors avoid any decay heat problems. Granted, liquid fuel allows you to immediately disperse the fuel and thereby prevent any further fissioning; but there is still the problem of short-lived isotopes decaying very rapidly and generating enormous energy, heat, and pressure. This happens whether the fuel was solid or liquid.

      For example, all three fukushima reactors shut down successfully and stopped fissioning immediately during the earthquake. It was not a runaway reaction. The problem was the enormous decay energy during the week after the reactors had shut down. The same problem would also afflict liquid fuel reactors.

      Granted, thorium reactors would not be using water as a coolant so presumably they wouldn’t have had hydrogen explosions. However they wouldn’t just be “meltdown-proof” or able to forego the expensive containment.

      Liquid fuel reactors may work at atmospheric pressures, but only so long as their cooling systems continue to function. If cooling stops, and the fuel heats up tremendously, then things wouldn’t be at atmospheric pressure any more.

      Liquid fuel thorium reactors do have the big advantages of far fewer transuranic wastes, and far more abundant nuclear fuel.

      • Liquid fuel can also be rapidly dispersed enough to deal with decay heat. To take it to absurdity, drain into a tank a mile wide with a flat, level floor. Obviously that’s excessive, but clearly it’s possible for passive cooling to deal with decay heat. How expensive it would be, I don’t know yet.

        • I think the question comes, if for what ever reason, the salt can not be drained and power is lost. Meaning no more pumping. While the main fission is stopped the residual fission is then more than enough to vaporize the salt, pressurizing a vessel not designed for pressure. A good pair of running shoes would be in order at that point.

          There are numerous other issues that come up with a molten salt reactor that are not present with conventional reactors. For instance the question of water. Water can not be used for fire fighting or as a radiation shield. This would enormously complicate any human based approach towards the reactor vessel. Just getting eyes on a problem would be a serious challege.

          • “While the main fission is stopped the residual fission…”

            The nature of criticality is that the mass and geometry required for neutron gain is there or it is not. There will be plenty of residual decay heat, but no ‘residual fission’ absent the moderator and fuel density.

          • “While the main fission is stopped the residual fission is then more than enough to vaporize the salt, pressurizing a vessel not designed for pressure. ”

            Did you mean “residual heat”? There is no residual fission when a reactor is shut down. The liquid reactors will employ a plug in the bottom that will melt if too high of a temperature is reached (i.e. loss of cooling) which will drain the fuel into tanks that prevent fission.

          • Oops. I meant no controllable fission after shut down but chose my words very poorly. The decay heat is quite significant for quite some time. That was the cause of the Fukushima meltdowns after all.

          • Residual heat is from residual fission of daughter nucleotides. It is only the reaction of the main sequence that is turned off i.e. the critical sequence, as I made clear. Just saying residual heat is misleading. Fission is continuing and producing tremendous heat, just not the main critical sequence. There is no way to ‘prevent’ this, just cool things as the heat output declines.

  19. I’m intrigued by the potential for airborne wind energy.

    I was reading about a recent paper suggesting that jetstream wind energy is limited but I reckon it would be quite challenging to harness anyway so I’m not particularly fussed by that.

    The bit I am interested in is below that, say up to a few km. Given the higher capacity factors and the inherently lower embodied energy of the generator compared with surface wind technologies, it seems like a sector that deserves an R&D jump start.

    There are some positive looking companies conducting R&D in this area and NASA have started looking at it, but does it have the kind of potential we need?

    • Jamie – I actually work on AWE 🙂 The jet stream stuff is a bit of a waste of time for now, but low altitude very interesting, especially for potential of relatively cheap offshore installations.

      For my money, Makani and Skysails are two of the most advanced companies in this space. $/kwh has potential to really get down low, but technical challenges remain. And it’s still no solar…

  20. Hello and Merry Christmas!
    Thank you all for your contributions to this open topic. You have re-energized my thinking and idea-mongering!
    First: we need a fundamental re-think of what technology offers in an era of scarcity. Scarcity of what? Not all components will either fade away or become too expensive over time.
    Second: rewrite the building code; any structure that cannot meet its own basic energy needs (heat, light, cooling) will not be built. If it can collect more energy than it needs, the excess will be used initially to offset older buildings’ requirements, etc.
    Thirdly: revamp the transportation fleet by encouraging/subsidizing alternate forms of transportation. Greater efficiencies are the goal, but if not achieved, more drastic measures may be required. We associate freedom of movement with other basic freedoms until other priorities come into force.
    Fourthly: lifestyle – too often associated with a political/institutional dynamic, i.e. the justification thereof. As we are seeing with the “faster than the speed of light” ( concept, our expectations of modernity are too rigid, too inflexible. As an example of alternative thinking, try also “biomimicry”.
    Thanks for the Wikipedia link to solar towers; here’s one example of flexible thinking:
    “…A smog filtering system designed for a city that will generate electric power. A solar chimney assembly including a chimney (3) is build using a mountain (9) as support..”

  21. Wanted to call attention to this somewhat wild essay, A Brief History of the Corporation: 1600 to 2100 ( and how the author creates a formula for economic growth that factors in ideas, energy, and time. Note how he simply drops energy from his equation–voila, by magic 🙂

    “Ideas fueled by energy can free up time which can then partly be used to create more ideas to free up more time. It is a positive feedback cycle, but with a limit. The fundamental scarce resource is time.”

    • It’s definitely got some holes, as you say, but that was worth reading. I think the graph about “free agents” speaks volumes. It shows the problem of socio-political power we face: The corporation remains the core source of elite wealth, yet, thanks to relentless productivity growth, it is leaving a larger and larger share of people adrift. Like peak resource issues, that fact, in a world of corporate media, is never going to get acknowledged, unless the underlings force it onto the agenda. Alas, we seem to be transfixed by the very distractions the corporations are peddling.

  22. There are many challenges out there. Climate, energy, countries losing gimbal lock and financial instability of the world economy are some of the more interesting ones.

    What can you do with the last one? It seems a binary choice: governments everywhere default or governments everywhere inflate their way out of debt. Can you map out a 3rd solution or frame the issue in a way that makes default or inflation certainties?

    • Tax the rich, hire the unemployed to rebuild ecosystems (including human ones), build solar and wind on a massive scale, redistribution money and energy to halt the poverty-population growth cycle. Essentially, do with the economy what we did to conduct WWII, but this time use the power to pursue ecological sustainability.

      It’s quite obvious, and would work. Alas, it’s not a “serious” proposal, because it threatens the rich.

  23. I have not seen Tom examine the possibility of energy saving by rebuilding our cities as single unified structures (Soleri type arcologies) rather than randomly scattered structures. If we lived in a unified designed structure transportation distances would be miniscule compared to what we have now and heating/cooling needs would also be far less. As well as new power production we need to also look at the very way that we live and examine other possibilities. Though we have advanced technology our homes and cities are only bigger versions of the way people lived a thousand years ago. We have to get smarter than this.

    • Thoughts along these lines have been bouncing around in my head the last few days with a lot of different angles, but basically driven by a sense that we take up too much space on the ground. I wonder what might be possible extending upwards rather than sprawling. I’m not sure how you would make such vertical living attractive though – certainly giant sky scrapers of current design are a bit lifeless. But perhaps something more in line with a giant artificial (or actual! Biotech guys?) tree. Still need energy to support the whole system but if we are looking midterm I don’t see this as a problem. The issue will be getting through the interim fossil->renewable crunch. Here mega arcologies don’t help you as there is no remotely conceivable way to build them out and relocate the worlds population into them before having to deal with the other issues.

      But mid term, I can very much see mankind recreating sheltered ecosystems to replace the ones we broke. We already do, in fact, with pest control and endangered species reintroduction.

  24. Hi, 1 question and 1 remark

    *The Question*
    I work on optimization problems, mainly shape and engineering design optimization. I wish I could contribute to provide solutions. I wonder what kind of optimization problems would be useful to look at
    – Do we know the optimal layouts for solar panels (shape of the panels + their layouts) ? Is there room for significant improvements ?
    – Same for wind turbines
    – I wish to here about suggestions 🙂

    *The Remark*
    I can’t help thinking that a part of the energy problem is simply how much sissies we are ^^ An individual motorized transportation ? Heating the house when it’s above 0c outside ? Or bellow 35c ? Common, you who is under 60, with the best medicine the human civilization ever had, you can’t take that ? Is that you, Homo Sapiens ?

  25. We must not let the disaster of an improperly located reactor in Japan deter our efforts to increase use of nuclear energy.
    The atmospheric changes as a result of hydrocarbon combustion are causing weather instabilities that are having serious adverse effects on millions of people world wide.
    The switch to nuclear power is an absolute must.
    The ongoing environmental degradation from the Fukushima failure should make clear the importance of the site selection of any nuclear facility. This is especially true of any site that holds fission waste products.
    We can avoid the danger of these major nuclear contamination events, such as Chernobyl and Fukushima by focusing our efforts on FUSION reactors that do not involve radioactive fuel or waste. Research should concentrate on the FUSION reactor that is currently in operation. Hereafter we shall refer to this reactor by it’s common name, the Sun. The Sun has excellent siteing characteristics. At over ninety million miles from Earth we have something of a solution to the “not in my back yard” resistance movement. The Sun is tsunami proof and has a record of reliability going back over four billion years. With minor possible exceptions, FUSION energy from the Sun has powered all life on Earth and is the source of energy in all fossil fuels.
    Write your congressman and demand more nuclear energy from our currently operating FUSION reactor.
    Tell him that sunshine is the only income we’ve got.

    • Nice write up. Solar does have an issue with its intermittent nature which is its #1 problem. Solar has the scale and now powerful market forces bearing down on it that will make capacity addition a non issue soon.

      If you write to your congressman, tell him we need help with the intermittent power problem. Pumped storage is coming on as fast as it can, about 31,000 MW of capacity have received preliminary approvals and are on the way. They will need political support as construction nears.

  26. Often you consider the problem of scaling a particular technology up to the point to meet the world’s needs. This is as enormous problem, particularly if you assume that India, China, and Africa (roughly half of the world’s population) are all going to have some sort of access to modern tech and lifestyle. Would it be useful to consider the same question for specific smaller regions?

    For example, on the electricity side, consider the Western Interconnect for US/Canada. Compared to the Eastern Interconnect, the per-capita power consumed is smaller, much more of current power generation is from conventional hydro; there are good wind, solar, and geothermal (if such pans out) resources relatively close to the population centers. Sites suitable for substantial pumped hydro storage to reduce the intermittency problems of renewable are much more common. Regional solutions might be quite feasible.

  27. We have talked a lot about the potential safety issues with modern nuclear, but if the new designs hold weight on the math….I think the take home message is that we can solve the world’s energy problem right now with the design. We have the technology and designs right now to provide safety for the plant, so the main issue now is the economic cost….and if energy becomes scarce suddenly that is no longer as big an issue.

    Solar’s issue now is itermitency, which can be solved either with a storage solution or a grid based solution.

    My issue with the grid is how large does it have to be? Will countries across the ocean trust each other with their energy future? In other words, are we okay with a China that could shut off power to our entire grid….with the mutual assurance that we would do the same to them the next night?

    Would a country be willing to go to war for a single morning, using solar energy at their disposal, knowing that the opposing country is in darkness and doesn’t have the energy to wage a counterattack?

    So assuming that would not be a viable solution, then there is the storage solution. As Tom pointed out before, we don’t have a storage solution yet. We don’t have anything that can scale to the level we need to make large scale solar a reality.

    So to me Solar is in the definite maybe camp right now. It could be the answer, but there are a lot of technical hurdles to overcome. Where Thorium type reactors are in the definite box, the issue there is primarily an economic one

    • Risk assessment is part of everyday life response. An individual’s existence depends on a certain degree of successful risk assessment. In the case of certain risks involving scientific technology, I would look to the advice of those with greater knowledge of the issue. In the case of nuclear power I know bunkty. So I look to the experts in risk assessment. That is the insurance industry. They have several hundred years of practice at risk assessment and they put their money where their mouth is. When the government assumes the risk for nuclear power liability you can be sure that the insurance industry has passed on that risk. If the insurance industry considered nuclear power plants to be an acceptable risk they would be all up in arms about “socialized insurance”. Their job is to take acceptable risks at a rate that makes them a profit. There is only one location suitable for a fission power plant and that is lower Manhattan, NYC. See how that goes over.
      The problem with the diffuse nature of solar energy is not a problem of utilization. It is a problem of control. Decades ago, R. Nader said something to the effect that solar energy will be feasible when Standard Oil figures out a way to put a meter on the Sun. Life on Earth will return to living on current solar income whether humans are here or not. Murphy’s math shows that we can not continue our current energy use policy. Tom did the math. Hello.
      Electricity is about to get real expensive after the sun goes down. But then,
      Sunshine is the only income we’ve got.

    • I think you’re on the money suggesting that countries won’t want to entirely forego their energy independence, but do you really think its going to come down to a ‘hey, it’s dark, we can attack with impunity’ situation?

      Come on.

      Missiles, aircraft carriers, jets, tanks, nukes, guns etc aren’t going to run directly on solar power any time soon. There will be an energy carrier of some sort, and it’ll be storable. If nothing else becomes available then it’ll just be synthetic hydrocarbons of some sort.

      The new nuclear designs are cool, but also inherently suspect. To put solar in the same box as thorium in terms of technical barriers is way off base. Around 25GW of solar were installed this year. What’s the total for Thorium?

      Yes, storage and intermittency create complications but not insurmountable ones. I realise such a statement requires something to back it up – hopefully it doesn’t take too long for me to get that post finished. Meantime though, don’t give solar too much of a hard time. The technologies are there, and are on the cusp of commercial viability.

    • I think what Tom is really saying is that our long term energy future is doubtful. There are real physical barriers to continuing along our present path. That’s what the math is about.

      WRT to Solar, vast majority of projections point to solar being our cheapest source of power in fairly short order. I’m reading an internal report from a leading solar supplier that projects panels being manufactured at 43-52 Cents a watt. In less than 5 years. The long term 20 year projection is to use manufacturing scale to drive it lower at 3%-7% for decades to come. Sub $1 per watt panels will be the new norm.

      These are real world numbers. The war in the trenches if you will. Solar is not the same as pie in the sky (at present) Thorium, though I do agree, only nuclear and solar/wind have the scale to help us in future.

      WRT intermittent Sun, Tom is right that we will have trouble fully transitioning to solar not the least due to the pumped storage problem. Instead what is more likely to happen is that gradually Solar will increase to 20%-40%-60% and we will start using fossil plants, esp. natural gas from shale as our storage solution. This will stretch out the time we can use fossil fuels from about 200 years for coal to about 1000 years plus. About 100 years for gas to about 500 years plus. We wbuy more time.

      At the liquid fuels problem, I throw up my hands. Toms, numbers are dismaying.

      • “At the liquid fuels problem, I throw up my hands. Toms, numbers are dismaying.”

        I don’t see it. If there is an energy bind coming I suspect it happens overall, not just with liquid fuels as there are too many paths forward. Coal and gas and biomass can be made into liquid fuels. Transportation might be made electric (and thus 4-5X more efficient). Biofuels. All these fall down if there’s an overall energy bind, but not one in just liquid fuels.

  28. I’d like to see the math on synthesizing hydrocarbon or other liquid fuel from atmospheric CO2 and H2O given a power source. Or alternately, from using biomass as carbon source, and adding hydrogen synthetically.

  29. When doing the math for backing up intermittent power like solar, refer again to the NREL numbers in Tom’s solar post ( As pointed out there, the tough problem is backing up seasonal minimums (fixed tilted plate):
    Dagget, CA 5.2—6.6—7.4
    St. Louis, MO 3.1—4.8—5.9
    Quillayute, WA 1.5—3.4—4.8

    The first number is the *average* worst month. Turn’s out the worst, worst month Quillayute saw over the decades of observation was 0.9 W/M^2/day. Dagget’s worst was 4 W/M^2/day ( Storage post assumed national battery or the like with 7 days of storage. Here we have a *month* or more of received power as low as 0.9 W/M^2/day in Washington state. The entire country looks like it barely reaches 3 W/M^2/day collectively in its worst Decembers, though not at the same time.

    BTW, note that yes, as posted above space based solar is indeed only 5X better at (~32 W/M^2/day) than southern Ca’s *average*, but it is 8X better than southern Ca’s seasonal worst, and 35X better than Washington’s seasonal worst.

    • You make a good point about space based solar providing, if not a dramatically increased rate, at least a nice stable one.

      As several readers have mentioned, I think a review of solar energy conversion to liquid fuels is a good area to cover. The question becomes can we create enough overenergy with solar to allow us to convert the spare energy into enough liquid fuel to hold us over when solar’s output decreases.

      And that extra energy is going to have to be really extra. We have talked about people’s concerns about nuclear safety. But image the outcry when the “cloudiest year on record” puts our entire energy grid in jeopardy.

      In solar becomes the standard form of power, we will have to back it up with something very stable and reliable….even if that is liquid fuels stored from excess solar power.

    • Oops, those solar collection figures should all be kWh/M^2/day.

  30. Am I the only one here who’s actually looking forward to the end of cheap oil with no substitute? I think it could improve society a lot.

    No more sprawling suburban mazes! We’ll have to live in real cities again, where walking and biking is much easier. And we can rip up all the ugly streets and get some green space.

    No more industrial farms swimming in fertilizer. We’ll have to go back to real farms and real food.

    No more cheap plastic JUNK. We can make quality stuff that lasts, instead of pitching it all into the trash every day.

  31. I am also very much in the thorium camp. From all the (armchair) reading I have done, it is the only solution I see that scales to modern demand requirements.

    One of the biggest factors that really grabbed me by the shirt collar is the amount of energy necessary to produce fuel for a reactor as compared to Uranium. It is a HUGE difference. Thorium is usable as fuel after mining and milling. Uranium has to be enriched because only a small subset of Uranium is what is desired. The enrichment process is a HUGE energy input into making the fuel.

    I also understand that since the fuel is a fluid, a lot of other crap can added to/burned in the process. This means that thorium has much less waste compared to modern nukes. Further, existing piles of waste could be slowly used up in thorium based fuels.

    As pointed out above, any emergency can be solved by draining all the fuel into special underground tanks to absorb decay heat, making the system inherently safer than modern designs.

    In fact, the whole process between uranium and thorium is about as common as the shared idea “nuclear” because the similarities seem to end there.

    The best resource I have found on MSRs was an almost 100 page PPT that was published as a slide deck for a presentation at some green energy conference at NASA in 2007 IIRC. I still have my local copy, but the online copy has since been pulled. I even looked in the WayBackMachine and its not there either.

    Google either of these for good search results to read: filetype:pdf filetype:ppt



    • While Thorium has the scale for our power needs there is no point in being overly optimistic about it. I too support Thorium energy but also look at it with a dispassionate eye.

      There are some real problems with it too.

      BTW there are many inaccuracies with your statements on boosting Thorium. Once corrected your case for Thorium becomes very weak.

      My main question is one of cost. I just don’t see a Thorium reactor, even if liquid fueled, costing less than a conventional Uranium reactor. If anything, it might end up costing more.

  32. P.S. on pumped storage:
    Someone just pointed out to me that while mentioning lake Erie in the pumped storage post, Tom did not explore the possibility of using lake Erie/Ontario as pumped storage. I just juggled the numbers a bit, and that project alone could provide the current ~5TWh(500GW) base/peak load difference with just 1m of water level change per cycle. Granted, it would still be a daunting project, 500 of the biggest turbines we can build, and insane flow rates, but much less daunting than finding places in the mountains to provide comparable capacity.
    Any thoughts?

    • Recall Tom’s target in the Pump Up the Storage article was 336 billion kWh (336 TWh): 2TW for 7 days, though here are several caveats that would move that figure either down or up.

    • I covered the basic idea/math in the pumped storage article: see the section titled “Drain the Great Lakes.” Slightly different assumptions (I went bigger than just using Erie), but still inadequate and requiring mind-blowing flow as you point out.

      • oops, somehow I missed that section on a quick glance. I kinda assumed my “someone” had read the whole article.

        Aside from that I strongly disagree with the 2TW*7days number, especially after you convinced me that solar is the way forward – the sun comes up every day fairly reliably. It seems likely that overprovisioning on the panels will be cheaper than storage, so we mostly need storage to get us through the night. But you explained your reasoning behind that number several times, so no point in arguing.

        • “… I strongly disagree with the 2TW*7days number, especially after you convinced me that solar is the way forward – the sun comes up every day fairly reliably….”

          There’s data supporting an argument that the backup period should be even longer. Look at the St. Louis, MO solar collection which was referenced in the Solar Wind Triangle article as the ‘most typical’ for US at 4.8 kWh/M^2/day. It happens that the worst December collection on record for St. Louis is 2.3 kWh/M^2/day, i.e 30 days (or more) at half power, which is equivalent to 15 days at no power [1]. One can address the seasonal minimum periods can by doubling either the amount of storage from 7 to 15 days or the number of PV panels, pick your poison.

          With respect to load, I think when replacing the current US *primary* energy consumption rate of 3 TW with electricity from solar, a replacement figure of 1 TW is more appropriate given a replacement of only fossil fuels and Carnot losses, certainly for purposes of calculating solar backup.


Comments are closed.