Why water supply affects your computer

Between now and 2020, the greatest increases in population growth in the United States are projected to happen in the places that have the biggest problems with fresh water availability. This isn't just a drinking water problem, or even an agriculture problem. It's an energy issue, too. Most of our electricity is made by finding various ways to boil water, producing steam that turns a turbine in an electric generator. In 2000, we used as much fresh water to produce electricity as we used for irrigation—each sector represented 39% of our total water use. (From a poster at Lawrence Berkeley National Laboratory.)


    1. Depends on the plant, there are a lot of different systems.  Most  use cold water in one form or another for cooling the steam down and returning it to liquid form after it goes through the turbines though.  

      That means you’ve got to have ready access to a water source like a river to dump all that extra heat into, or you have to have cooling towers.  But those result in a constant loss of some of the coolant to evaporation.  

      Either way, you need a ton of water to run these things.

      1. But is the loss to evaporation really loss? Doesn’t it eventually come back down. I mean, sure it is loss locally, but on a larger scale, is the water lost?
        Not arguing, I genuinely don’t know the answer.

  1. At some point, climate change has to reach a level where folks start to realize that maybe living in Phoenix and similar cities isn’t a great idea.  Right?  Or are we assuming the population projections won’t change as things become (even more) hellish in those areas?

    1. You ever seen what certain rivers look like by the time they run through the southwest?  You can’t use them for cooling if they’re no longer even running.

  2. The boiler/turbine/condenser circuit is a closed loop, but external water must be used to cool the condenser.  This means either dumping heat into river water (bad for river life), or evaporating water in cooling towers.  Either way, water is needed.

    1. Still don’t see why we can’t evaporate it for cooling and then harvest that as condensation. Or make purifying water a byproduct of power generation (at some marginal increase in cost, I’m sure): co-locate sewage treatment and power generation and use the waste stream as the water source. 

      But yes, at some point people may realize (through increased costs) that living in the air-conditioned desert is unsustainable. 

      1. Condensing it requires a source of energy or temperature difference (for example water colder than the dew point). It’s a losing proposition.

        1. But power plants generate energy so they have/are a source. Using the lower temperatures found just below ground might offer a temperature differential that could be used.
          Let’s be clear: a lot of the design and implementation decisions assumed cheap energy/plentiful water, etc. now that we know there are constraints, would we do things the same way? I expect not.

          1. I think you are getting yourself into a loop. The theoretical maximum work one can get out of a system is dependant on the heat difference between input and output.

            That being  said, Eskom in South Africa did a lot of development with cooling towers which vastly reduced the amount of water used, but never eliminated it.

    2. These systems are still closed systems as is required by law. Yes even the evaporating water in cooling towers.  These work like just like the radiator in you car. Simply they work as follows Water / steam is allowed to expand absorbing heat then circulates through pipes where looses heat and condenses again. This water no more leaves the system then the refrigerant in your AC unit.

      Also a poster is not a reviewed work. Take any info you see on them with a gain of salt.

      1. Cooling water is completely recycled in only a small fraction of power plants using closed circuit dry cooling towers (like a car radiator system). Far more often plants use evaporation of large quantities of water, because they are more efficient. The water is recycled to the atmosphere, but not to the power plant.

        Plants with large reservoirs of available cold water, many of them coastal, use direct (or once-through) cooling, dumping waste heat directly back into the water source without significant evaporation.


        “According to a 2006 Department of Energy (DOE) report discussed in the Appendix, in the USA 43% of thermal electric generating capacity uses once-through cooling, 42% wet recirculating cooling, 14% cooling ponds and 1% dry cooling (this being gas combined cycle only). The spreads for coal and for nuclear are similar. For 104 US nuclear plants: 60 use once-through cooling, 35 use wet cooling towers, and 9 use dual systems, switching according to environmental conditions. This distribution is probably similar for continental Europe and Russia, though UK nuclear power plants use only once-through cooling by seawater, as do all Swedish, Finnish, Canadian (Great Lakes water), South African, Japanese, Korean and Chinese plants. “

  3. Under riparian law, I must return the water “substantially unchanged” to the watercourse after it’s driven my millstones.  Water law’s a bit fossilized on the Right Coast, but at least it’s not a winner-take-all game like the desert states.

  4. Use != consumption. In both cases, you need to distinguish between water lost to evaporation (and transpiration for crops) and water which is “used” but then returns to be available downstream. So, power generation “uses” a lot of water, but consumes very little of that. 

  5. Like some other commenters, I’m kinda skeptical about this .  Use != consumption is  a good point.

  6. Given that turning water into steam is a good way to purify it, seems like more of these places should be combined with water purification/desalinization efforts.

  7. According to Wikipedia, there’s a desalination plant that takes 6.8 kWh to produce a cubic meter of water, in other words, water can be produced at a rate of 147,000 liters per kWh. According to IEEE, the only energy sources that require more water than that are fuel ethanol and biodiesel.

    In other words, if we keep our heads on and don’t use ridiculous energy sources, there need be no water shortage limiting the power supply.

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