February 04, 2005
Power Plant Waste Heat Could Produce Fresh Water

University of Florida Department of Mechanical and Aerospace Engineering professors James Klausner and Renwei Mei have developed a method to use power plant waste heat to lower the cost of water desalination.

Since power plants need water for cooling purposes and desalination plants need heat, why not combine the needs of both? The professors - James Klausner and Renwei Mei - calculate that their process would shave a sixth of the cost from today's most efficient technology.

If we either develop cheaper energy sources or more of the world becomes industrialized then there will be no world scale shortage of drinkable water. If people can afford to pay for water it can always be produced by desalination. Alarmist talk in some circles about future water shortages assumes a high rate of poverty. Waters shortages will become a bigger problem in the future only where severe poverty will continue to be a problem.

Employing a major modification to distillation, Klausner's technology relies on a physical process known as mass diffusion, rather than heat, to evaporate salt water.

In a nutshell, pumps move salt water through a heater and spray it into the top of a diffusion tower a column packed with a polyethylene matrix that creates a large surface area for the water to flow across as it falls. Other pumps at the bottom of the tower blow warm, dry air up the column in the opposite direction of the flowing water. As the trickling salt water meets the warm dry air, evaporation occurs. Blowers push the now-saturated air into a condenser, the first stage in a process that forces the moisture to condense as fresh water.

Klausner said the key feature of his system is that it can tap warmed water plants have used to cool their machines to heat the salt water intended for desalination, turning a waste product into a useful one.

He has successfully tested a small experimental prototype in his lab, producing about 500 gallons of fresh water daily. His calculations show that a larger version, tapping the waste coolant water from a typically sized 100-megawatt power plant, has the potential to produce 1.5 million gallons daily. The cost is projected at $2.50 per 1,000 gallons, compared with $10 per thousand gallons for conventional distillation and $3 per thousand gallons for reverse osmosis.

Because the equipment would have to extract as much heat as possible from the coolant water, it would need to be installed when a plant is built, he said. Another potential caveat is that a full-scale version of the mechanism would require a football field-sized plot on land, likely to be expensive in coastal areas where power plants are located, Klausner said. Presumably a utility would sell the fresh water it produces, recouping and then profiting from its investment, he said.

Limited quantities of energy and intelligence are the two biggest factors holding down the rate of economic development. Every technology that increases the efficiency of utilization of energy or lowers the cost of energy spurs economic growth. Anything that raises human intelligence levels will do the same. Also, computer technologies effectively increase the efficiency of the use of human intelligence by unburdening many tasks from human minds. So computers are brain utilization efficiency increasers.

Share |      Randall Parker, 2005 February 04 01:13 AM  Energy Tech

Michael Vassar said at February 4, 2005 9:39 AM:

When you said
"Limited quantities of energy and intelligence are the two biggest factors holding down the rate of economic development."
was that supposed to be an established fact, or an axiom. As I recall, the USSR had essentially unlimited fossile fuels and lots of smart people. China and India aren't becoming massively smarter. Neither are energy and intelligence rich Iceland and Norway the exemplars of wealth that the US is and that Singapore is becoming. It seems to me that economic freedom is the biggest factor holding down economic growth. Intelligence is probably also important, but causality in that relationship is difficult to determine because it is a positive feeback loop, as economic growth increases intelligence through nutrition, reduced infection, etc. Obviously energy is a major industry, and price shocks can impair economic growth in the short term, but I have never heard a convincing argument that greatly reduced prices for energy would do much to accelerate economic growth. The idea would seem absurd to me if it wasn't accepted by so many intelligent people.
If you can give a link to such an argument, I would like to see it.
In the absence of further data, my best guess is that a country like the US could probably boost its economic growth rate by between 1% and 2% over the next century by increasing economic freedom, while even free energy would probably not provide more than a decade or two of similarly accelerated economic growth. Boosting intelligence of course has practically limitless potential, and we could probably accomplish a great deal today by providing better maternal education, care, nutritional supplements, and incentives to gestating mothers, promoting breast-feeding, etc. We are probably doing quite a bit just by waiting lead contamination falls. Still, I doubt that even an optimal intelligence enhancement program using today's science could more for our economic well-being than improving free-trade, reducing regulatory burdens, etc.

Randall Parker said at February 4, 2005 10:01 AM:


I'm assuming decent government. Yes, political systems can always be devised that prevent people from reaching their economic potential.

Increasing economic freedom: Well, my own forecast is decreased economic freedom in America due to higher taxes to pay for retirement of an aging population.

My point is that limits in the supply of fish, gold, trees, iron ore, and countless other natural resources are not limits to human progress. With brains and energy you can always manipulate matter to produce what you need.

Jon Swenson said at February 6, 2005 9:12 AM:

I submit that it is the limited resources themselves which spur progress, if there is a political and economic environment in which individuals can profit from thier innovations.
I agree with your point that human ingenuity will alway provide alternatives to limited resources, given the opportunity.

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