Collision Between Water and Energy Is Underway, and Worsening 189
An anonymous reader writes "This article is an eye opening perspective on another side effect of power generation — water usage: 'More than 40 percent of fresh water used in the United States is withdrawn to cool power plants. Renewable energy generally uses far less water, but there are glaring exceptions, such as geothermal and concentrating solar.' The article also mentions that power plants have to shut down if the incoming water is too warm to cool the plant. 'Also, even though some newer plants might use far less water, they could find that there’s far less water available as water temperatures go up and water flows go down. Another study found that nearly half of 423 U.S. plants were at risk of lower power output during droughts because their intake pipes for water were less than 3 meters below the surface.'"
LFTR (Score:1, Informative)
Such a simple solution.
Liquid Fluoride Thorium Reactor
Has passive safeties, does not use water to cool, heats up gas to generate power.
https://en.wikipedia.org/wiki/LFTR [wikipedia.org]
http://energyfromthorium.com/ [energyfromthorium.com]
Re:wait (Score:4, Informative)
There are closed loop systems [wikipedia.org], but you still need to cool and condense the steam back to water just to pipe it around, and re-heat it. Pushing spent (low pressure) steam back into your heating plant is no where near as efficient as sending water in. Condensing to water and pumping that is actually more efficient.
Most electrical generation plants have two or three stages of generation, where the steam exiting the high pressure turbines is re-heated with with flue gases and
sent through the medium and low pressure turbines. At the end of the line they have extracted just about all the heat they can from it.
The problem is we have no really good use for the remaining heat of spent steam. And no way to extract the remaining heat into a useful form, or
recycle it back into the plant or any other economical use.
So we essentially heat the atmosphere, by venting it into cooling towers.
But the water? It all gets returned to the cooling pond, except that bit that you see rising as vapor (its not steam) above the cooling towers.
.
Re:This is more sensationalism than any real threa (Score:5, Informative)
The study is more about the risks that power plants may not have enough water available, not that they are using it up. The plants are competing for the water with those that do consume it, such as agriculture and residential, exacerbated by long term drought cycles in some areas, and climate change.
Re:This is more sensationalism than any real threa (Score:4, Informative)
Most power plants built the lake in the first place. And they don't discharge into the lake; they discharge at or downstream of the dam -- so they aren't pulling in their own hot water. Next to none (read: NONE) of the intake water is used in the turbine steam loops -- those are 100% closed loops, if you're losing water you have a problem. (a serious problem for nuke plants.) [note: steam loops use distilled water -- ZERO minerals, RO reduces the mineral/particle volume, but it's not zero.]
That said, there are still numerous plants that use evaporative cooling towers. And they do, indeed, require a significant volume of water that is "consumed" -- it goes up as vapor. While it isn't "drinking water", it's water that's not available to the filter plant that feeds your taps. In a drought, you have a choice... cool the power plant, or have water to drink.
Regardless of who built it, a lake is a closed body of water, period. And yes, they DO discharge into the lake, typically; if you take water out of a lake and release it into a river, you drain the lake. I'm not guessing at this; I work for the very large civil engineering company that is mentioned in the article; not only do we do a huge amount of work in the power gen world (we're building the second-largest power plant in the world in South Africa right now), but 30% of the world's drinking water comes from water purification or desalinization plants that we built. I've been doing NERC CIP compliance work since before the auditing deadlines for the first 18 requirements (NERC CIP was implemented in stages at first), so I've spent about 6 years in the power industry by now, at about two dozen utilities in total.
And you're right, next to no water is used in the steam loops, but some is...as I said. Enough is important that the demin plant is considered a critical asset if the plant itself is considered critical, and there's a large storage tank of demineralized water to give some cushion in case there's a problem with the RO filters. And you are right about the zero minerals, but every plant I've ever seen...CT or ST...used RO filters. They use a lot of them, in series.
But to get back on point...if you take water from a river and put it back in a river...or from a lake to a river downstream...you're still not using up that water. You're just moving it from one point to another. Again, neither is potable water, and it's not causing a net loss.
Evaporative cooling towers...also called passive cooling towers...are extremely rare outside of nuclear installations. They're very expensive to build in comparison. Even among energy engineers, they're something of a curiosity for the fossil generation world. So that won't add up to the 40% cited.