Solar Maximum

Discussion in 'Boat Design' started by JonathanCole, Feb 23, 2010.

  1. Scot McPherson
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    Scot McPherson Senior Member

    I don't think solar is going to be a player on the sea, not for propulsion anyway. It's not capable.
     
  2. Skyak
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    Skyak Senior Member

    "not capable" -this is way too vague.

    Lets look at this another way. Solar is the current global low cost source of electric power in a large part of the globe. Nuke could beat it with tech and legal improvement -but that won't reach commercial shipping. Oil cost and taxation is only going up from here. Solar cost is still going down, electric storage cost is still going down. So the only thing limiting solar is energy density, and the driving force is cost. From what I see, it's not a question of if, it is a question of how much, when and where.

    The current slump in oil prices could be prolonged by terrestrial solar expansion, but eventually exploration and high cost extraction will be needed and price will go back to $80+. Taxation is also likely in the next decade. Crews are also likely to be eliminated in the next decade, so the primary cost of shipping will be fuel and speed will be more of a variable. In these conditions solar covering the top of ships would account for the entire margin and ships without significant solar will be obsolete. Clipper ships of the past can still carry cargo, they just couldn't match the economics of the steam ships. Solar can only provide 20 to 30% of a ships power? That's enough to price the competition out of business.
     
  3. hoytedow
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    hoytedow Wood Butcher

    Fuel for boats sure is. I pay a dollar more per gallon for ethanol free gas than I would if I bought fuel adulterated with ethanol.
     
  4. daiquiri
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    daiquiri Engineering and Design

    Solar panels covering ships is the most common picture we have of solar-powered propulsion. But it is probably also the most limited way of using solar energy.

    Try to imagine solar panels (not necessarily just photovoltaic ones) not on the ship but on the shore, covering vast (and maybe otherwise unused) areas and connected to a processing plant which converts it to a chemical fuel. It could produce hydrogen, ethanol or any other form of fuel we already know how to burn or how to directly convert into the electric current.

    Or the land-based solar-power plants could one day be used to continuously recharge huge high-density battery banks. A ship then arrives to the dock and while the payload is being transfered to/from the quay, the modular empty battery bank also gets substituted by the fully charged one. The ship then departs for the next voyage and the battery bank is sent to the solar power plant for recharging.

    Assuming that battery and fuel cell technologies, or chemical fuel synthesis, will keep improving in the next years and decades (and they will), these two scenarios might make the solar power a sensible option in the shipping industry too.
     
  5. hoytedow
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    hoytedow Wood Butcher

    When you blanket an area with solar panels, you may as well have paved it over because it destroys the ecology of that area. Wildlife needs space too. Oil wells by comparison leave a very small footprint.
     
  6. Stumble
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    Stumble Senior Member

    When I say solar is not capable of providing propulsion for a cargo ship I mean that it is physically impossible to instal enough solar panels on cargo ships to provide them with enough energy to provide propulsion. There simply isn't enough power available in sun light to move a ship.

    Or to put it another way, with 100% efficient solar panels, and 100% of a cargo ship covered in those 100% efficient solar panels, they still wouldn't generate enough power to move a ship. You can tax fuel until the world economy collapses because people can't afford to move goods around, but solar ships will never happen. It is more likely to see wood fired boilers powering ships than solar panels.

    Now converting shore generated solar power into fuel for ships is technically possible but the round trip efficiencies are terrible (about 1% right now).
     
  7. daiquiri
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    daiquiri Engineering and Design

    Could you please share a source of that efficiency figure?
     
  8. Stumble
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    Stumble Senior Member

    Ya, sorry I should have included it. https://www.chemistryworld.com/news/solar-jet-fuel-made-out-of-thin-air/7325.article

    So 1.7% efficiency converting solar to fuel, and about 50% efficiency converting fuel back to power. So technically possible, but pretty poor.

    I am also reminded of the USN's technology that converts nuclear power to jet fuel but I don't remember their efficiency numbers. I remember the press saying it would cost about $3-$6/gallon at the time but I don't remember anything else about it's efficiency.

    No question these technologies are coming, and will get better, but we are a long way from commercial operation. For the overall carbon usage on the planet a far better option is interconnecting electrical grids so that excess renewable energy can be fully utilized elsewhere rather than converting it to liquid fuels.
     
  9. Scot McPherson
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    Scot McPherson Senior Member

    I am bemused by the statements that power storage and generation technology is improving all the time. Really? I mean sure incrementally, but what real improvements have occurred that allow you to predict that continued improvement will have _enough_ of an impact to make solar feasible for ship propulsion?

    The flooded lead acid battery is still the most powerful rechargeable large storage device we have, it is mostly unchanged for 150 years. Alkaline Batteries ala Duracell are still the most powerful portable non-rechargeable batteries. Except for 2 kinds of Lithium batteries that are way too expensive to manufacture for a non-rechargeable application.

    Lithium/Graphite is fine for small device light weight batteries, but it has a tendency to explode, and banking cells of lithium ion batteries together is asking for catastrophic disaster. Lithium's only benefit is the weight benefit which is why it's desirable for watches and phone, but it can't hold electricity in the same densities as lead acid and alkalines.

    Fuel cells are another item that's mistaken as new technology...Christ the first fuel cell was invented in the mid 1800s. No kidding...look it up, it has a patent.

    Photovoltaics haven't changed much. They were also invented in the 1800s, they are not new. We've changed how they can be used, but we haven't changed their efficiency in any appreciable sense for several decades. They are still only 18 or less % efficient.

    Incremental improvements are not going to make solar feasible for ship propulsion, no matter how big those increments are. There are too many limiting factors. The only way solar would suddenly become feasible would require a paradigm shift. A discovery that is so new and so different that it changes our view of electricity, how to produce it and store it. The last paradigm shift was in the early 1900s. We've incrementally improved our knowledge of the paradigm as it stands, but there is only so much improvement left before it's maxed out as is.

    I just don't see how anyone could see "leaps and bounds" in our knowledge of solar and energy storage when it's been mostly and fundamentally unchanged for 150+ years.
     
  10. daiquiri
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    daiquiri Engineering and Design

    We shall arrive there. Let me just remind you that the first photovoltaic cell had an efficiency of 1%. Today, commercial models are running along the 30% figure and 46% efficiency was reached in lab conditions.
    If there will be a political and educational commitment in that direction, technical progress will be able to reach the desired goals.

    No, that is wrong. The physical principles are the same as 150 yrs ago (of course), but the efficiency, pollution-containment and environmental awareness have been increasing all along the way.
     
  11. daiquiri
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    daiquiri Engineering and Design

    By the way, I have always been baffled by the people who seem to be convinced that the world will run forever on the existing technologies...
    Where has your creative immagination gone?
     
  12. Scot McPherson
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    Scot McPherson Senior Member

    See this is kinda what I mean....a cell's output efficiency increasing to 46% is an incremental improvement. It may be close to 3x what is commercially available today, but that efficiency ends right at the individual cell's terminals. After taking all the system losses into account, you haven't gained very much. Even if we managed to get 100% solar capture and conversation (thermodynamics kinda limits 100% conversion from ever happening, though we can get close). It's still not going to be enough. That's why I and others keep saying we need a magnitudes jump in output.
     
  13. Scot McPherson
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    Scot McPherson Senior Member

    Just for the record I never said this, however as you enter the arena of complexification, everything get's more costly. I don't necessarily mean dollars....Think resource depletion, and outputs of manufacturing and operation. We were never in danger of running out of fuel until everyone started burning it like it was an infinite resource.

    Well guess what, there are infinite resource in renewable fuels, renewable fuels do not remove or add anything from the biosphere. Burning trees does not add carbon to the biosphere. It's already there, and a new tree will replace the one burned, and reabsorb the carbon and other byproducts that were expelled when the tree was burned. That's balance....that's the kind of thinking we need, how to use what will recover itself in balance so long as we manage it....(i.e. don't cut down the trees faster than they can grow using the above example).

    Better extraction of energy from combustion, harvesting waste heat, etc etc....these are solutions we need.

    Sail is almost a free energy harvester. Someone, I can't remember who figured out that the cost of a working set of sails that will last several years of constant use costs about the same as the same boat/ships cost in fuel to circumnavigate the globe one time. That's efficiency.
     
  14. Stumble
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    Stumble Senior Member

    I dont know how to make it more clear. With 100% efficient solar collectors a ship like the Emma Maersk could generate 8% of its daily power usage. That's it, so short of doing something to increase the solar output of the sun (which would kill all life on earth) solar won't work.

    I guess long term it might be possible for some sort of force field lensing technology to be created that would effectively increase a ships surface area by drawing power from a much larger radious, but that is literly Star Trek level technology.

    And you won't find a person less resistant to new technology than
    myself. I love new tech, I spent years selling high tech materials, and had one of the first paperless law offices I know.

    But new tech has to be technically possible (not possible right now) to form the basis for a proposal. Arguing in favor of solar powered ships is literly no different than arguing that if ships just used anti-gravity drives we could reduce fossil fuel consumption.

    I am all in favor of pushing solar efficiency as far as we can find a way to go. And reducing ships energy demands as far as we can go. But saying we will resolve the shipping industries fuel problems by just using teleporters is just silly. Well, unless you have a working teleported, or at least an idea of how one could be made.
     

  15. Skyak
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    Skyak Senior Member

    There is significant research into "flow batteries" driven by the looming problem of solar saturation, but from all I have seen the energy density is still well below FF and the mass is constant instead of declining.

    I have a relative that had a method to crack water using solar directly (plasma). His business plan showed a cost advantage over current industrial gas generation (no claim of transport market viability). The efficiency of fuel cells and electric motors is excellent but storage is still a big problem.

    Since storage is a major problem and none of the advantage I prefer the chances for a moving power plant. Imagine a dense PV field that provides power and propulsion, and exchanges cargo barges at either end of an equatorial route. The barges provide buoyancy, z axis only, so the large, roughly square solar deck could be reasonably light. Like Polynesian's lashed their multihulls to make them seaworthy but with modern foils and computer control. When it reaches it's destination outside the port the deck crawls off the arriving barges and on to the departing barges, so the majority of your ship investment does not waste time unused during loading and unloading. The investment would carry less risk because in the event of a shipping recession it could operate as an electric utility. The way I see it, routes and speeds are variables -economics and risk are for optimization. What do you think? Seems worth some feasibility checks.
     
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