Water limits on power plants 14

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1. 

   Matt G Posted 8:07 am
   05 Oct 2007

   The most efficient nuclear plant designWould reject heat not to the environment, but to houses and domestic water.  This would reduce water consumption (though to a lesser extent in summer conditions, you'd still be heating domestic water), and just as importantly remove fossil fuel based heating.
   Of course convincing people to install a nuclear plant in their neighborhood is not a simple task (though certainly possible).  

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2. 

   Pangolin Posted 8:45 am
   05 Oct 2007

   It's why "Carbon Capture" is a fraud.To capture the CO2 from power plant emissions you have to cool it down below ambient temperatures.  Since you just used the energy of burning to heat gases to above ambient temperatures to make steam.......
   Any carbon capture scheme I have ever read has a line that equates in physics to "and then you wave a magic wand and the problem goes away."  
   There is no free lunch in physics.
   
   Put the Carbon Back

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3. 

   Craig Allen Posted 11:25 am
   05 Oct 2007

   Not all powerplants use waterThe deep hot dry rock geothermal electricity industry in Australia is about to take off. Much of the resource is in desert areas where water is in short supply.
   So the market leader - Geodynamics - plans to use a Kalina Cycle plant to generate electricity. This uses a coupled pair of closed circulation loops whereby  water, having been circulated deep into the earth, then at the surface gives up a portion of it's heat to a second fluid which is then flashed to turn turbines. The cooler (but not cold) water is then re-injected  back down wells into the geothermal anomaly. The anomaly that they are currently drilling holds enough recoverable heat to meet all Australian electricity needs for hundreds of years!
   If it is possible to do this with geothermal heat, you have to wonder why it can't be done with other forms of thermal power station.
   Here in Melbourne last summer we had the price of water being bidded up by coal power stations competing in the water market with farmers. Now we are about to begin building desal plants to secure water for the city. So we appear to be fast approaching the obsurd situation where we have to generate more electricity to power desal plants to supply fresh water to urban populations because the water is needed for the power stations, so they can generate electricity to power the desal plants so that ...

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4. 

   Matt G Posted 1:20 pm
   05 Oct 2007

   PicoallenWhere does the heat go?  I can imagine using a refrigeration cycle to transfer a high amount of heat to air, which may be the purpose of the Kalina cycle but doesn't sound like it from your description.  In order to generate energy you need a heat source (nuclear material, geothermal, burning coal, etc.) and a heat sink (evaporating water, exchanging cold water with oceans, etc.).  You describe the heat source (difference in temperature of water from ground) but not the heat sink.

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5. 

   KenG Posted 10:34 pm
   05 Oct 2007

   A Real Problem?This issue resurfaces periodically but I don't understand why this is any real problem. Power plants do not "use" water in the sense that it becomes unavailable. The water is merely a mechanism to transfer heat to the environment. That total heat is insignificant in the big picture. If a lake, river, or ocean is used for cooling, the water if very slightly warmer. If a cooling tower is used, a certain amount of the water is evaporated faster than it ordinarily would be.
   If this is considered to be a real problem, dry condenser power plants are already in use. In these plants, a closed condenser (like the radiator in a car) is used to directly transfer the heat to the air. The cost is slightly higher and the efficiency slightly lower, but there is no technical challenge at all.

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6. 

   amazingdrx Posted 11:30 pm
   05 Oct 2007

   Wind and solarNo water use.  Another big advantage.
   Hydro electric storage for wind and solar can even help restore wetlands and aquifers by capturing flood waters.
   
   http://amazngdrx.blogharbor.com/blog

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7. 

   GRLCowan Posted 2:24 am
   06 Oct 2007

   Geodynamics must intend to air-coolTheir Kalina cycle page mentions a plant that takes 90 kilograms per second from a "geothermal brine flow" at 120°C and discharges it at 80°C, so removing heat from it at a 15.1-megawatt rate, and from that makes 1.8 MW of electricity; 13.3 MW is discharged as waste heat, and to do this in the desert, one needs a few hundred kg/s of air.
   As Matt G helpfully points out, air-cooling is unusual but not very unusual. I was first taught that in this thread.
   --- G. R. L. Cowan, former H2 energy fan
   
   Internal combustion power without exhaust --
   
   http://www.eagle.ca/~gcowan/boron_blast.html

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8. 

   Sean Casten Posted 5:30 am
   06 Oct 2007

   Air coolingAll:  You can always air-cool a steam cycle (e.g., all coal plants, nuke plants and combined cycle gas plants), but remember that your air temps are going to be higher than your water temps, especially in the summer time when you can have a spread of 30+ degrees.  This means that you have to raise the exhaust pressure from the steam to maintain a sufficient temperature differential to condense, and therefore drop the efficiency of the power plant.  For economic reasons, this drives most to water-cooled plants.  For environmental reasons, we ought not advocate solutions that drive down operating efficiency.  
   The beauty of a cogen plant is that you "square this circle" by using a local building/factory/etc as your condenser, thereby eliminating this penalty.  (Or at least substantially reducing.)  
   And yes, you don't have to worry about this at all with wind & solar - or, for that matter, simple cycle gas turbines, stirling engines and a host of other techs.

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9. 

   HighPlainsDrifter Posted 5:39 am
   06 Oct 2007

   multistage flash distillationBoth carbon intensive and nuclear fuel costal power plants can recapture much of that lost energy and produce fresh water at the same time by cogenerating with multistage flash distillation plants. Aquatic heating is minimized and increased salinity is only a minimal local issue.
   L.A. should loose some of its water rights to other people's water and they could do it.

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10. 

    sunflower Posted 6:24 am
    06 Oct 2007

    Existing negative cost heat sinks.Potable city water offers a free heat sink.  Who needs cold water except those few who still drink from the tap?  Warm water for showers, clothes washing, etc. would reduce domestic water heating bills.  City water supply is transported through uninsulated ground coupled buried pipes.  An enormous amount of heat dumped into city water supply and water towers would become a free geothermal heat sink while, at the same time, heat up domestic water a few degrees.  As Sean wrote, industrial process heat is also a negative cost heat sink.  This makes solar power from cogeneration cheaper than dedicated solar power plants isolated in the desert with large and expensive dry heat rejectors.

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11. 

    Delay And Deny Posted 7:00 am
    06 Oct 2007

    Will open source housing change Canada?Will open source change Canada? Democratizing sustainable housing in Canada (part 2)
    
    http://www.redhatmagazine.com/2007/10/05/will-open-source ...
    Canadians may want to spend more time saving the environment given their current ecological footprint, which would require four planet Earths to sustain if everyone on the planet lived like them. It takes 7.6 global hectares of resources to support each Canadian according to the latest World Wildlife Fund's Living Planet Report (see figure 3). An open source platform for sustainable housing could pull groups from all over Canada and provide them with vibrant connections and resources through which they can share ideas, best practices and make a living through creating near zero energy homes. The Now House team thinks that small changes can equal big results. Small changes and collaboration on a national scale through an open source platform is one way to do just that.
    
    John Bailo
    
    
    Sutext:

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12. 

    Delay And Deny Posted 9:28 am
    06 Oct 2007

    Could Nuclear Power Save the Planet
    
    Great vid on Fora.tv
    http://www.fora.tv/2007/09/14/Could_Nuclear_Power_Save_th ...
    Interesting coal vs. nuke comparisons
    Example: a person who lives his life entirely on nuclear power generates a Coke Can sized amount of total pollution.  On Fossil fuels each person generates several freight trains full ( 67 tons ).
    
    John Bailo
    
    
    Sutext:

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13. 

    Sam Wells Posted 11:22 am
    06 Oct 2007

    Closed loop cooling systemsI think the idea here is we need closed loop cooling systems instead of using raw water and discharging it.  Some studies seem to hint that thermal pollution of the Hudson River and Long Island Sound could be as much 0.5 degrees per year, although taken together with global warming and other confounders.  Seemed like the average power plant used at least 300,000 gallons of water a day.  Refineries can use more, since water is also used to distill product in distillation columns and pump product in pipelines (and becomes contaminated).  Thermal pollution is wave of the future, mon, and we need to do something about it quick.  /sam
    
    Onward through the fog

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14. 

    jpowers Posted 9:57 am
    07 Oct 2007

    cogenerationCogeneration will help save money from heat produced by electrical production. Electrical generators can use this more efficiently for both home and business use.

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