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Power Science

New Heating Technology Uses Seawater and Carbon Dioxide (csmonitor.com) 155

Kenneth Stephen writes: While some enterprises have used sea-water for cooling, others are starting to use this for heating. and thereby cut back greatly on the carbon footprint of large facilities. What makes this technique even more fascinating is that a key component of this technology is carbon dioxide — the greenhouse gas that has climate watchers so worried. An Alaska aquarium recently announced "the first installation of CO2 refrigerant heat pumps to replace oil or electrical boilers in a conventional heating system in the United States" after 7 years of development, and predicts they'll now save up to $15,000 each month on their heating bill.
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New Heating Technology Uses Seawater and Carbon Dioxide

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  • Well, that's good news.

  • Dangerous (Score:1, Funny)

    by Anonymous Coward

    Carbon dioxide is a trace gas in the atmosphere. If too much of this is done, we'll run out of carbon dioxide. That will kill plants and make the Earth a very cold place. This seems like a bad idea to me.

    • Re: Dangerous (Score:5, Informative)

      by rkcth ( 262028 ) on Sunday April 24, 2016 @11:46PM (#51980705) Homepage

      CO2 is just the refrigerant. It is not consumed by the heating cycle. CO2 has been used for cooling in many places, this is the first I've heart of using it in a heat pump for heating though.

      • A heat pump and a refrigerator are the same thing? Or am I missing something? So this uses C02 instead, but the concept is still the same.
        • by jfengel ( 409917 )

          You can think of a heat pump as a reversible refrigerator. In cooling mode, it works just like a refrigerator: the compressor compresses gas, lets it radiate heat of compression outside, then pumps it inside to evaporate.

          The remarkable thing is that you can turn the process around to heat the inside instead of the outside. You compress the gas outside to make it hot, then pump it inside to release that heat. A carefully-designed valve causes it to go from liquid to gas, or reverse, depending on where you wa

    • Carbon dioxide is a trace gas in the atmosphere. If too much of this is done, we'll run out of carbon dioxide. That will kill plants and make the Earth a very cold place. This seems like a bad idea to me.

      We could take out 100 ppm of CO2 and return back to pre-industrial levels. That's 780 gigaton of CO2 (even more when you consider that the oceans will release some too). As a comparison, we only have about 200 gigaton of proven oil reserves left. So, tell me, what should we be more careful of ? But you needn't worry at all, because the required CO2 isn't going to be removed from the atmosphere. They'll just make some new.

      • Maybe if we could complete the cycle, convert CO2 back to long chain hydrocarbons, we'd be good indefinitely.

  • by Anonymous Coward on Sunday April 24, 2016 @11:54PM (#51980721)

    Especially this bit about compressing the CO2 to over 2,000 psi to heat it. I assume this process is powered by fairy dust, unicorn farts, politicians speaking honestly, or some other such magical limitless power source? This is Slashdot - give me the physics, not the fluff piece.

    • by mspohr ( 589790 ) on Monday April 25, 2016 @12:01AM (#51980741)

      Article is dumb.
      The real news is buried. Google "transcritical CO2" to get the real story.

    • by redback ( 15527 )

      Its exactly how a fridge works.

      when the compressor in your fridge compresses the coolant it gets warm, and then goes to the radiator on the back to cool down. Then when it is allowed to expand again inside the fridge it gets cold.

      Nothing new about this technology at all. Same science that is behind fridges and airconditioners the world over.

      • Except the part where CO2 needs 2000psi to achieve the phase transitions, would be a bitch if you lost pressure and the pipes filled with sublimated CO2.

        I suppose if you can afford the high pressure pumps, pipes and fittings, then the thermal efficiency of the cycle starts to pay off.

        • by Anonymous Coward

          Eh, the pressure isn't that big a deal, and the German automakers are getting into it too, after they decided to pass on using R-1234yf.

          That it is non-flammable and non-toxic adds to the benefits, especially in car accidents.

        • by Smidge204 ( 605297 ) on Monday April 25, 2016 @06:08AM (#51981359) Journal

          The pressure really isn't that big of a deal. 2000PSIG sounds high, but industrially speaking that's not terribly impressive. To put it into perspective, CO2 storage cylinders are often 1800 PSIG.

          Compressed natural gas as a vehicle fuel is 4000PSIG Max. Compressed hydrogen storage is 5000-10000PSIG.

          More importantly, it's not the max pressure that's the important metric but the differential pressure. You wouldn't be compressing it from atmospheric pressure - the MINIMUM pressure in the system is going to be somewhere around 400PSIG.

          Of course, this prompts an important question: Where the hell did "2000 PSI" come from? Existing commercial trans-critical CO2 refrigeration operates at ~1300PSIG, so either the designers of this system have determined there's a good reason to go all the way up to 2000 or there's some journalist math/sensationalism going on here... 2000 PSIG is typically the relief valve setting, so maybe that's the confusion.

          • Some people are pretty comfortable throwing around 3000psi SCUBA tanks, too - but their "high pressure" hoses run closer to 150psi, IIRC - the regulator is right on top of the tank. It's all very do-able, but a pretty steep departure from freon based stuff and the pressures it needs.

          • Hell, aren't scuba tanks 3000 psi?

        • ...and amazingly none of the metric pushers has tried to trash this part of the thread yet.
        • by jbengt ( 874751 )

          Except the part where CO2 needs 2000psi to achieve the phase transitions

          At 2,000 psi, there are no phase transitions between liquid and gas.

    • Looking through it, It's basically a new variation on a heat pump that's capable of higher efficiency at a higher temperature differential.

    • Nah, they'll just use solar! That works in Alaska, right?
    • This is a pond-loop geothermal system with CO2 as the coolant. Compared to resistance heating the water it's going to be much more efficient, and - in Alaska especially - it's going to be more efficient than an air-based system as you won't be working against sub 20F temps for a good portion of the year. But the power to run the system is all electric, which means it's coming from traditional sources (and by traditional I mean both fossil based and renewable sources).

      The article, however is clearly powered

  • by Slick_W1lly ( 778565 ) on Monday April 25, 2016 @12:51AM (#51980825)

    Feel free to point out if I'm wrong.. But, isn't this just like a huge mini split? Using CO2 instead of um.. Freon, or whatever they put in them these days?

    Stick a huge finned thing out in the ocean, cycle some refrigerant around it, transfer heat from one side to the other? Requires electricity and it's not like.. you're *consuming* CO2 and removing it magically?

    The article seemed to describe exactly what the mini-split in my living room does, only on a much higher scale, and with C02 as the transport medium instead of some other rare gas?

  • My first thought was "CO2 as a refrigerant - its kind of toxic isn't it? I wouldn't want to be around if a pipe broke."

    Then I thought "Ammonia is also used as a commercial refrigerant, and that is also toxic. Which is worse?"

    I haven't found any good answer online. Nobody seems to want to talk about toxic concentrations of ammonia in air, just in blood. Then there are all sorts of other complications - what quantities and pressures would be used for comparable CO2 and NH3 refrigeration plants? Does the lower

    • Interestingly this last link refers to CO2's 'low toxicity'.

      Well, CO2 isn't really that toxic. You'll die if you breath in pure CO2 anyway though. But that's because you'll suffocate since it is heavier than air and therefore remain in your lungs and prevents any new oxygen-rich air from entering.

      It will also fill up closed spaces like basements and you'll basically drown in it.

    • Re:Toxicity? (Score:4, Informative)

      by Firethorn ( 177587 ) on Monday April 25, 2016 @05:14AM (#51981253) Homepage Journal

      CO2 levels [inspectapedia.com] need to be above/around 50k ppm, or 5%, before it starts becoming a real danger. You'll know something is up long before that, around 1-2%.
      Ammonia, [wikipedia.org] on the other hand, is considered lethal at 500 ppm, or 0.05%

      I'm going to go with 'CO2 is at least 1/100th as toxic as Ammonia'. The CO2 displacing the O2 is a bigger concern, but still 'solvable' by getting out of the room.

    • by necro81 ( 917438 )

      Does the lower density of NH3 mean it will disperse faster? Are you a whole lot worse off after being nearly killed by NH3 than after being nearly killed by CO2

      With death by CO2, it'll probably be fairly unpleasant, because your body's breathing regulation is governed largely by the concentration of CO2 in the blood. If there is too much CO2 in the ambient air, the CO2 in your blood can't be expelled through the lungs, and eventually you'll become acidotic and die. If you are lucky, you'll lose consciou

      • The one saving grace is that ammonia smells quite distinctively, and at levels well below serious risk, so you'll at least know that there's a problem. CO2 is odorless, so you may not know that you are having a problem until your vision starts to cloud and your chest gets tight.

        You'll probably notice your breathing pick up and feeling like you're not getting enough air. The body doesn't track O2 levels, it tracks CO2. Increased CO2 concentrations trips the body's responses to increase respiration. It doubles, for example, at 1% CO2.

        Stick some sensors around the system that set off the fire alarms if CO2 goes high. Done.

    • The Anhydrous Ammonia SDS [airgas.com] just says "Get medical attention immediately" over and over, then "Causes serious eye damage. Liquid can cause burns similar to frostbite." over and over a few times, then throws in a few "Causes severe burns. "; so I guess it's pretty toxic. I didn't see a CA prop 25 warning so I guess it just fucking kills before it causes reproductive harm or cancer, but I didn't look real good.

  • I'm predicting that somebody will complain that using seawater is going to change the "natural" temperature of said seawater and will therefore affect the flora and fauna in the water and therefore humans are evil usurpers of the planet.

The greatest productive force is human selfishness. -- Robert Heinlein