Global warming

Discussion in 'General Discussion' started by Frank, Oct 22, 2010.

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  1. Mariner

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    Don't forget that you often get blocking highs in both the summer and the winter. Very little wind for days or even weeks. The extremely cold snap late in 2010 saw the wind farms as a whole in the UK produce a tiny fraction of their usual output for a number of weeks - just when more electricity was required for some heating systems.

    How many days or weeks power storage do you need to cover times when such a blocking high is in effect?
     
  2. hoho

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    Not really as if you don't want to use fossil fuels for backup you will need to use something like pumping water uphill and that will take up far greater areas than the turbines themselves. Not to mention being simply infeasible in most parts of the world due to no suitable terrain.
    In those kinds of conditions pretty much none of the renewable energy sources works short of growing algae near equator and shipping it in. So still I'd say nuclear is by far the best solution. Wind, solar and other things could at best give us some 5-10% of total production and a tick in the "we tried!" column.
     
  3. Gubbi

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    If you store the energy chemically, you can store an almost arbitrary amount. The U.S. strategic oil stockpile holds 750 million barrels (25 million m^3).

    Again, I'm not looking for wind power to displace all other sources of enery overnight. You need to crawl before you can walk. When, not "if", we have the capability to store 24 hours worth of consumption we can expand wind power production to 50% of total usage in an economically viable way.

    Cheers
     
  4. KimB

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    I don't think you have any idea how expensive coal actually is. The costs I was comparing, by the way, were in comparison with just the cost of the power to the consumer. Here's one site that goes into some detail:
    http://solarcellcentral.com/cost_page.html

    But in reality, coal costs far, far more, because of the adverse health effects from mining the coal and from the air pollution that results from burning it. If we actually forced coal companies to pay for all the damage they do to peoples' health, then coal simply would not be able to compete with renewable energy. Allowing them to get away with pushing this cost onto the rest of us amounts to a massive subsidy for coal power.
     
  5. KimB

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    Wow. That's just plain stupid. There is no evidence whatsoever that the Sun will be anything but a minor contributor to climate change over the next couple hundred years. This is just some idiotic energy executive talking out of his ass.
     
  6. KimB

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    Because it is rare for both wind and solar power to be effective in the same area, and because no single renewable energy method is robust enough to replace all of our energy needs. We need to do basically everything, not myopically pursue a single alternative energy.
     
  7. Sxotty

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    That is a hand waving argument sorry.

    Coal power is cheap. Sure if we include X, Y, and Z it is more expensive. But guess what? That isn't included. I don't deal in hand waving arguments sorry. I am quite aware of the externalities associated with coal, but that doesn't mean I pretend it costs a lot to get coal powered electricity.

    The link you gave is based on a quite optimistic paper that itself says
    Then it goes on to say that we should not do classic economic evaluations b/c it undervalues the future energy flows if you discount them... Well guess what the same thing happens to nuclear which is how this started. Nuclear plants last a long time and the future power generated is discounted...
     
  8. Frank

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    Hi guys,

    I have the impression that I'm on "ignore" by all of you after my last session of replies. So, I'm curious:

    1. Do you have me on ignore?

    2. Do you think that there might be something in mine (and Burt Rutan's) view on AGW?

    3. Do you also think that having a very well researched view that nobody else supports is not a good career option?
     
  9. AlphaWolf

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    Oh there's plenty of money in AGW denial. Big oil has lots of money to throw at research projects that can provide data to support their bottom line.
     
  10. Frank

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    Thanks, AlphaWolf.

    But I cringe at the title of "denier". "Skeptic" is acceptable, but I would prefer "alternative scientific view". Like, Evolution versus Intelligent Design.

    :D
     
  11. Frank

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    Evolution vs ID

    Ok, I can't help it, I have to compare AGW and the Engineering View to Climate (EVC) to Intelligent Design and Evolution.

    AGW and ID share:
    1. Things happen because Humans exist.
    2. It is far too complex to have come into existence without intelligent interference.
    3. The planet is adapted to the living beings on it.

    EVC and ID share:
    ?

    AGW and Evolution share:
    ?

    EVC and Evolution share:
    1. Things happen regardless of human interference.
    2. Things evolve according to the environmental changes, and the adaptation of living beings to that.
    3. The living beings on the planet are adapted to it.

    If I wanted to sell the idea, I know which one I would choose.
     
  12. itsmydamnation

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    there are solutions to the storage problem. the "best" one is hydro. it cost 1.4 times the energy to pump the water up there but it can go from 0 production to a couple hundred megawatts is 15minutes.

    pretty much no other energy source can scale power that quickly.
    I dont know who around the world does it, but i know we do it in Australia. i know that companies that use fossil fuel sources to do this, purely for the capability to be able to quickly meet peak demand.
     
  13. Vadi

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    Potential energy storage has been proposed in different ways too, like a giant granite cylinder. http://www.agenda21-treffpunkt.de/daten/sign.php?sg=Hubspeicherung-Felszylinder


    OT:

    ID is not scientific, I don't know of any experiment which would suggest the opposite.
     
  14. hoho

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    How would it work exactly? Creating hydrogen or somehow making synthetic hydrocarbons? What's the efficiency like?

    Though I'd say if you want to use wind energy and have half-decent way to make it produce chemical fuels then that's the only thing you should do with it, not produce electricity. It's far easier to transport those fuels and there is almost no problem with "lag" with them. Making the wind turbines produce fuels and burning them again for electricity is just horribly inefficient.


    http://www.nationmaster.com/graph/ene_oil_con-energy-oil-consumption
    And US uses aroudn 19 million barrels a day so that 750M lasts for around 40 days. For a sense of how big amount it is then 25 million m^3 is a cube of 290m at each side.
    That obviously goes for every kind of energy source.
    24h is way too little if you still want to use it for electricity. Half a week is almost enough when half of all energy is produced by wind.
    You do realize that ID is not a scientific view by any measure, right? Though I guess then it does make a pretty good analogy for your views on AGW :)



    Yeah but that kind of pumping requires so humongous investment in building dams that it's just mind boggling. Linking again to my favourite analysis on the subject: http://physics.ucsd.edu/do-the-math/2011/11/pump-up-the-storage/

    There he assumes 2TW of usage for US and one week of storage. Currently US has 78GW of installed hydroelectric power or around 4% of what's needed. Also he assumes around 90% of efficiency at converting the pumped water back to electricity. Rather generous but won't really matter much in the end considering the scale of things.

    .
    How it would look like:
    [​IMG]

    Dropping the dam height from half a kilometer to "only" 250 meters (Hoover dam is around 200m) would mean we need 16 times more of those or around 2500.

    What about building the dams?
    So around 47 billion m^3 of concrete for the dams or a little less than 50km^3, a cube at little more than 3.6km at each side. You can build ~19000 great pyramids with that concrete :)

    And land usage:
    So yeah, energy storage is MASSIVE problem with any kind of renewable energy. Even if we drop the wind production to "only" 50% and require "only" 24h of storage we still can only make the numbers ~14x smaller. Doesn't help really, still pretty much as unfeasible as before.


    For other storage methods (flywheels, compressed air, regular batteries, lifting rocks etc) see this: http://physics.ucsd.edu/do-the-math/2011/09/got-storage-how-hard-can-it-be/. Hint: they are far worse than pumped water in terms of efficiency.
     
    #1394 hoho, Feb 10, 2012
    Last edited by a moderator: Feb 10, 2012
  15. Gubbi

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    If you can get 40-50% efficiency for end-to-end energy conversion, wind power will be economically viable in 15 years. Wind power has halved cost per produced kWh every 15 years for the past three decades.

    The cube root of 25 million is 292.

    For a comparison here in Denmark work is under way to expand one of two natural gas storage facilities from 6.3 million m^3 today to 11 million m^3. Gas is stored in salt domes 1.5 km below ground at 200 bar. The total heat equivalent energy capacity of the expanded facility is 24TWh.

    Denmark has 1/60th the population of the U.S.

    I linked to market data earlier in this thread for the Nord Pool exchange, which covers Scandinavia and Northern Germany. These had production data in them, including wind power. It is pretty clear from those that full wind production only occurs in short intervals, normally shorter than 36 hours. Being able to buffer 24 hours worth of consumption would allow for a much higher fraction of wind power.

    Cheers
     
  16. hoho

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    By end-to-end you mean from turbine to end user or creating hydrocarbons with the turbine energy?
    Can you name a few things that have had the biggest impact in bringing the price down? I would guess improving the turbine's efficiency wasn't really a big thing.
    My bad, I only took square root. 25M m^3 = 25km^3. Cube root of 25 is ~2.9 so it's "only" 2.9x2.9x2.9km block. Same for the concrete (3.6km at side). I'll go fix the numbers, thanks :)
    Yeah but you can't really compare that with pumping water. You can't compress water and using compressed gas (air?) for energy storage doesn't really seem that viable.
    Is that 11M m^3 the total volume of the "container" or does it mean it can fit that much gas in there after it's compressed to ~200 times the density? So in other words is it 11M m^3 or really just ~55k m^3?
    How much is that "heat equivalent" when converted to electricity? Also majority of the energy comes from the gas itself. I can't really see how it can be related to storing energy produced by wind turbines.
     
  17. Xmas

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    Yes, but: "The main problem with gravitational storage is that it is incredibly weak compared to chemical, compressed air, or flywheel techniques"

    Efficiency is not the only issue. Other storage solutions provide far higher density and can be more economical overall. Additionally, efficiency losses are mostly in the form of heat, which isn't necessarily lost.

    25e6 m^3 = 0.025 km^3
    1 km^3 = 1e9 m^3
     
  18. Gubbi

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    By end-to-end, I mean from wind produced electricity to synthetic gas and back to electricity.

    If you look at electrolysis, the most effective low temperature alkaline water electrolysis process achieves an efficiency of around 65%. Increase the temperature to 150 degree centigrade and pressure to 30 bar and 80% is achievable today.

    Burn the gas in a combined cycle gas turbine and you get 60% of the energy in the gas back. End-to-end efficiency is thus 65-80% x 60 % = 39-48%. With co-generation of power and heat you can get higher utilization.

    Scaling up is generally good because you have a lot of fixed costs per unit from production to installation. For example Vestas' next 7MW turbine will be 40% cheaper per MWh produced than their current 3MW V112-3.

    Removing expensive and fault prone components. Many turbine manufacturers have moved to a gearless design. There is problems in scaling this up, since the physical dimensions of the generator increase with power.

    Increasing turbine efficiency. The trend in the past decade has been to evolve the turbine itself (ie. the propeller) to produce in a larger wind envelope. Typically maximum power production is reached at 8-9m/s.

    The there is economies of scale. Wind turbines are moving from being a boutique product to a mass produced one. This means production can be made much more streamlined.

    And the cube root of a million is one hundred. The cubed root of 25,000,000 m^3 is still 292m.

    The 11,000,000 m^3 is the actual volume. The total gas capacity is 2,230,000,000 m^3.

    General Electric offers a 480MW combined cycle gas turbine that delivers 60% electric efficiency. So 24TWh heat equivalent can be converted to 14.5TWh electricity.

    Cheers
     
  19. hoho

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    Yeah but the less efficient storage you have the bigger windmill installation you'll need. Going from 50% effective to 25% will mean you need to double the amount of windmills.
    Perhaps but actually extracting that heat won't be easy.
    Gah, now I see my problem. Thanks again!

    Weird that I didn't notice how little the difference between that and the required concrete came out to be when using my wrong calculations for the oil reserve.
    Interesting. Can you share some links for me to read? I'd be especially interested to know what kind of raw materials they use for making it.
    Yes, definitely but there is a limit on that as well and at some point just the sheer amount of required resources will be a problem that simply doesn't exist on small-scale production.
    Do you have any guesses on how much can be squeezed out from improving both of those?


    Now that sounds much more interesting. I guess someone should give a hint to the do-the-math author to do some calculations on it :)
     
  20. KimB

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    Huh? Of course it costs a lot to get coal-powered electricity! Just because you end up seeing a huge fraction of that cost in your medical insurance payments and taxes instead of your power bill doesn't mean that those costs aren't there. Those costs are there, they're simply hidden.

    You're not making any sense here. All that this means is that we should be subsidizing solar (and wind) heavily because nearly all of the cost is an up-front cost. The cost being up-front means that the market just won't build them nearly as fast as the most efficient rate, and subsidies are a good way to make up the difference (the subsidies could also be paid for via an extra tax on electricity, evening out the cost over time).

    Nuclear has this too, but like I said, nuclear plants take a long time to build, and the more sustainable nuclear reactors are still a few decades away, while solar and wind power are here right now.
     
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