Skip to main content

View Diary: What Greens on Kos Need to Know about Energy (52 comments)

Comment Preferences

  •  A few errors, strawmen, and omissions (7+ / 0-)

    As to strawmen, who is advocating that all energy needs be met via biomass? I'm not aware of anyone who advocates biomass to the exclusion of any other form of energy generation. I think most people here recognize that, for example, ethanol is not a very good candidate for solving most energy problems.

    As to errors, wind turbines don't require 'rare metals' (as in elements low in abundance). They're more efficient if they use rare earth elements, like neodymium, for example. Rare earth elements only become rare when a major producer (like China) restricts their availability. Rare earth elements are fairly abundant in the earth's crust and in known, economically feasible to mine reserves. There can be environmental downsides to rare earth element mining - there don't have to be.

    As to omissions, not all forms of energy utilization are equal either. Electric motors are considerably more efficient than internal combustion engines (diesel or gasoline). Fewer kilowatt-hours of electricity are needed to go X miles than kilowatt-hours of gasoline, probably by a factor of around 2:1. Efficiencies like that, as well as conservation measures, can reduce the amount of energy required with little negative effect (and sometimes net positive effect) on lifestyles.

    Lastly, there is room for hydro expansion. Some dams have room for more generators that hasn't been utilized (Coulee Dam does, IIRC). Generators can also be upgraded to be more efficient. For example, using the same rare earth elements used in wind turbines in hydro generators, you can generate more electricity for the same flow. There is also the possibility of generating energy from rivers that don't have a lot of 'head', like the Missouri or Mississippi - their flow rate represents a significant amount of energy.

    Nothing will be the single solution to the problems of energy and climate change, and in fact that will probably require all of the methodologies and technologies we have or can create.

    Modern revolutions have succeeded because of solidarity, not force.

    by badger on Thu Mar 07, 2013 at 01:45:14 PM PST

    •  You miss the point (2+ / 0-)
      Recommended by:
      Yoshimi, R rugosa alba

      Let me state this another way:

      All renewable energy is essentially solar energy as wind and flowing water are ultimately driven by the sun's heat.  If plants, which cover nearly the entire surface of our country, are only able to harvest 80 quads of the sun's energy.  Do you really think that we, through our machines, can beat them?  Surely, we would have to cover a vast portion of our landscape with machines.  And the best of our machines do require Neodymium and Cadmium and similarly rare materials  Sure we could try to make machines that do not.  But they would be inferior.  Thus an even higher portion of our landscape would need to be covered with them.  

      I think it's foolish to try to beat the plants.  It's foolish to think we can sustainably consume 100 quads of energy.  This is why "Green Jobs" are not the solution.  A major reinvention of our society and civilization is necessary.

      •  Do I think we can beat plants? (6+ / 0-)

        Yep, because, a) we already are according to your graph, and b) photosynthesis is less efficient than a Humvee by a large margin. Photo-voltaic cells have been more energy efficient than plants since they were invented. Plants don't use wind energy or falling water, so those sources aren't in your 80 quads for plants. And things like nuclear energy or geothermal, while not renewable, still represent a lot of energy potential.

        Plants are, IIRC, about 9% efficient. Solar cells, even the most primitive, can reach 18% efficiency - double what plants produce. That's already 160 quads - more than what we consume. That's not counting all the other energy sources that plants don't use.

        And once again, neodymium and especially cadmium (they use it to plate cheap nuts and bolts, fer chrissake) are not rare. Neodymium is one of the unfortunately misnamed "rare earth elements", basically the lanthanum series on the periodic table. They are abundant, not rare. If you want rare, look at gallium or indium that are needed for most LED designs. And yet LEDs are still fairly cheap.

        I still favor reduction in energy consumption as the most effective approach - both improved efficiency and reduced consumption. I also aspire to be more than a vegetable.

        Modern revolutions have succeeded because of solidarity, not force.

        by badger on Thu Mar 07, 2013 at 03:28:58 PM PST

        [ Parent ]

        •  Okay... (1+ / 0-)
          Recommended by:
          R rugosa alba

          We already beat plants by burning a whole lot of dead ones in the form of fossil fuels.  My question is can we beat plants without cheating.  I.e. without tapping geologic reserves of energy.

          By your own calculation the answer is probably no.  If our solar cells are only twice as efficient we'd need to cover more than half the country with solar cells.  This, needless to say, would be vastly costly and, yes, probably exhaust our Neodymium and Cadmium supplies (As Cadmium is only 1 part /10 million of the earth's crust).  Sure we might have wind and hydro, but I wouldn't hold my breath.

          I'm not trying to argue against renewables.  They are a sensible investment and are the only source of energy that will ultimately last.  But I am against the idea that investments in renewables alone will solve the ecological crisis.

          •  I don't know if investments in renewables (0+ / 0-)

            alone either will be sufficient or economically feasible to replace energy derived from greenhouse gas emitting sources. It's an engineering problem, the answer is quantitative (needs numbers), and it isn't a simple answer to arrive at in the real world.

            Cadmium is about 100 times more abundant than platinum and there is a small amount of platinum in every modern car - tens of millions of them - in the catalytic converter. Cadmium is used in low quality photocells (CdS) and the 'cad' in NiCad rechargeable batteries is cadmium. If you open up any cheap piece of electronics that's more than 10 years old, the steel mechanical parts (chassis, etc) will have an iridescent appearance - that's cadmium plating. It's a toxic heavy metal, so its use is being eliminated, but it's cheap and common. It's a waste product (or would be if not reclaimed) of several types of mining.

            As to a calculation for beating plants, it's not that hard to do. 100 Quads = 100 Exajoules more or less is the amount of energy you want (actually more than what we want, because we both want increased efficiency and conservation).

            100 Exajoules = 2.8 E15 watt-hours (E15 is 10 to the 15th power)

            Solar flux is around 1300 W/m^2, but let's use 1000W for simplicity and to be conservative. 2.8E15/1E3 = 2.8E12 m^2-hr. The units are odd, but it's an intermediate step - we have square meters-hours. We can get the area of the array we need by making an assumption about hours.

            Let's say we get 5 hours of sunlight every day (average - some days a lot more, some days a lot less, but even cloudy days provide some energy, and we've already discounted solar flux 30%).  That's more than 1800 hours, but rounding to 1800, we then  need about 1.5E9 square meters of solar arrays.

            My goodness, that's a big number! It's a square 38,729 meters on a side - about 120,000 feet. There are 5280 feet in a mile, so we need an array 23 miles on a side to capture all of the energy the US uses in a year.

            But we haven't looked at efficiency! 23 miles assumes 100% efficiency. At 20% efficiency (pretty much achievable with solar cells, esp in the sloppy context of this calculation) we'd need 5X the area, or a square a little over 51 miles on a side (2650 sq miles - about 1/4 the area of MA).

            One-quarter of MA for all of the US energy needs without resorting to fossil fuels or any non-renewable source.

            Whether or not it's practical is another question (there are all kinds of problems producing this many cells and distributing the energy, depending on how centralized the generation is, for example) .

            But compared to the scale of plants, extracting 100 quads of energy from sun, wind and water alone is not a daunting problem because of scale. In fact, ONLY in terms of scale, it's pretty trivial. Scale isn't the problem. No matter how much you want to change my assumptions, you'll have to be unrealistic to get to even a TX sized array - about 100X the calculated area - and TX is less than 7% of the area of the US, meaning the array is only .07% of the US area.

            Oh and --- an exajoule is about 5% bigger than a quad, so the calculation is extremely conservative - I've overestimated the area needed by at least 5%, and probably a lot more. And we passed 1 exajoule in wind generation (actual output, not nameplate) a few years ago. The solar energy falling on the entire US (incl AK and HI) is probably somewhat more than 10,000 exajoules annually.

            Modern revolutions have succeeded because of solidarity, not force.

            by badger on Thu Mar 07, 2013 at 09:06:32 PM PST

            [ Parent ]

          •  Burning those dead plants . . . (0+ / 0-)

            This is the key point. Oil and coal have been very effective  (and uncomplaining) substitutes for slavery and serfdom. They have enabled ordinarly people in the developed world to live much better than royalty did in past centuries.

            For many applications in industry and transportation there is no substitute for fossil fuels, and it's a serious problem that so many people think we'll just be able to substitute solar, biomass, or wind and continue business as usual indefinitely.

        •  Efficiency is arguable... (4+ / 0-)
          Recommended by:
          Ahianne, badger, pgm 01, splashy

          Good old Wikipedia, to which I give almost no weight, argues it at 5.4%.

          Unfortunately, good old Wikipedia is pretty much correct in this case.  :-)

          Plants throw away pretty much everything except red and blue light.  It's a left-over from algal evolution when it was forced to deal with the remaining energies the cyanobacteria weren't using.  Most of the light energy reaching the planet is in the orange, yellow, and green part of the spectrum.

          There's no percentage in a plant using too much of the available energy.  Other resources, like water and nitrogen availability in the soil, become the limiters.  Too much energy absorption raises the plant temperature which raises the plant's metabolism, and ends up costing it in terms of energy production.

          That having been said, there are a few black plants where that temperature rise is an advantage.  They tend to be winter-growing or cold-zone plants.  In some cases, alternate parts of the spectrum are used for energy production.  In others, that energy is simply absorbed and re-radiated as heat to warm the plant's local environment.

          You're correct in saying that plants exploit exactly one energy resource--light energy.  They do nothing with wind, tidal, geothermal, nuclear, or other sources.  Unless you could dispersal of seeds, but that really isn't using the energy to grow, just to propagate--and very little of that energy is really "used."

          (-6.25, -6.77) Moderate left, moderate libertarian

          by Lonely Liberal in PA on Thu Mar 07, 2013 at 07:25:44 PM PST

          [ Parent ]

        •  What do you mean by plant efficiency? (0+ / 0-)

          Plants have many functions - the main one is, I suppose, to stay alive.

          A lot of them are 100% efficient at doing that - considerably besting your cited figure.

          So do you really mean something like capturing sunlight?  Turning that sunlight into hydrocarbons?  A combination of those factors (and others?)?

Subscribe or Donate to support Daily Kos.

Click here for the mobile view of the site