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The clear winner for "Power Generation Technologies" when discussing water usage is Hydroelectric Power (Reference the last chart in the article); and this method of energy generation should be promoted.

Additional benefits from hydro generation are as follows:
1. Zero emissions
2. A truly renewable energy source. It rains, water runs downhill thru a turbine and generates electricity, the water exits the plant unaffected by the energy production process, evaporation occurs, it rains, etc. etc.
3. Most efficient renewable energy source as the total energy conversion from the flow of water to electrical energy is greater than 85%. This compares to fossil fuel plant efficiencies in the range of 40 to 50% due to the fact that they must first convert the chemical energy in the fossil fuel to steam energy, then to electrical energy. In addition, fossil fuel plants have fuel costs, transportation costs, emission problems, and utilize 12 to 15% of their generated power to run their auxiliary power systems.

And, as a parting thought: Canada presently produces 60% of its total electrical requirements with hydroelectric power plants, and is installing new plants to produce 65% by the year 2012. The U.S.produces only 10% of its power by hydro plants. We're both located on the same North American continent. Why can't the U.S. produce more electrical energy with hydropower?

The water "consumed" by the various energy sources/processes needs to be categorized as to the nature of its "consumption", in that all water eventually is recycled, just not in its pre-"consumption" state. I would expect that the large water consumption tabulated for nuclear plants is used for cooling and is returned to its source untainted except for a modest increase in temperature, and so is less consumed, in a sense, than water used to produce energy through irrigation of biodeisel and ethanol crops. The former, with the increase in temperature carefully mimimized by plant design and siting at locations with ample water supplies, is essentially immediately available for other purposes, including irrigation; the latter is not.

This is a critically important distinction, in that quoting the raw data without clarification as to the post-usage availability of the water provides yet more grist for the anti-nuclear mill.

A little curious - "IEEE Spectrum converted their findings to L/1000 kWh, or the amount of energy required to power 1000 homes in the United States for one day." My house uses about 40 to 50 kwhr/day - the average apartment in our area uses 22 kwhr/day - 1000 kwhr would likely power about 30 to 35 houses for one day. Am I missing something?

From ozogg,
IEEE member (for 35 years!)

Am I too, too arrogant (again).
So much fuss about paucity of world potable water, but so, so, easy to solve (so I say).

There is plenty of water world-wide - it's called ocean. But how to desalinate CHEAPLY, and ABUNDANTLY ???

Only two facts needed:
1. Water evaporates ever more readily when its surface is under a lowered atmospheric pressure.
No need to actually boil it - just increase the evaporation rate.

2. The sun offers an average energy density of 1KWatt per meter squared, world-wide.

_____
Now some word pictures, since actual pictures not possible in this comment forum.

Make a cone, point upwards, made of translucent plastic, glass, whatever. Height and base diameter yet to be determined.

Around the lower edge, attach float chambers - but make the bottom of the cone air tight, by ensuring it dips in the water.

On the inside, construct a "gutter" attached all the way around the cone, like an 'inside-band'.

Somewhere ABOVE the inner water level, attach a very small pneumatic pump - like the car tyre pumps that plug into a 12volt ciggy socket. Power this pump with a photovoltaic array.

The inward side of the pump is connected to the bottom of the gutter, at one or more points.

The outward side of this pump delivers to a substantial and ruggedised flexible bag floating around the base of the cone, but not captive of the cone - like horse-shoe.

As the inner air space is reduced in presssure, the sun can evaporate the salt water ever more readily. The evaporating salt-water vapour rises, hits the cooler inside surface of the cone, and condenses into pure water, runs down the inside of the cone, into the gutter.

The pump can force out both air and pure water from this gutter to the surrounding bag, but hopefully pumps mostly condensed water.

The pure water bag can be repeatedly towed to shore, or the water can be pumped from the bag to shore, or to a collecting ship.

Make millions of these desalination islands around the world, and share the water world-wide.

Establish sever penalties for damage to these islands. Police heavily.

Anyone want to set up a focus / forum group, or join a "Centre for Research" ?? Contact me.

I would hope that IEEE would bring its world stature and expertise to bear on this proposed solution.

ozogg@netconnect.com.au

In paragraph 3 the author states that "IEEE Spectrum converted their findings to L/1000 kwh, or the amount of energy required to power 1000 homes in the United States for one day." If I am reading this correctly he is saying that a typical household uses 1 kwh per day. That number is very low. The typical kw demand may be 1 kw, but the energy use is much higher. A clarification is needed.

Why no mention of wind energy?

I’ve heard one wind expert claim that wind energy uses less water than any other source. It’s a shame that the article didn’t help confirm or deny this.

I'm surprised the article omitted wind power. In water terms it is only in manufacturing turbines and contructing the wind farm that water is consumed. Given that a wind farm will repay it's embedded energy debt in under a year, I would anticipate it wins hand down also with water.

I agree with the comments that all water will be recycled, it has no choice. The report seems not to clarify the difference between the bottom table on efficiences of electric generations types and sources of fuel on the top table. Why is the fossil fuel rated so high on one, and so much lower on the other?

Also, the water used to grow the biofuel crops is deemed a consumptive use, even though that water would inevitably be used to grow something, whether it is grass, crops, or trees. Only irrigated crops would consume water with other non-crop potential uses. So a distinction between irrigated and non-irrigated crops would have to be made. With cellulosic ethanol, the water use could potentially be attributed to grain production, while the water attributed to the straw would be much lower.

Broad generalizations are only that, and large differences exist in various situations.

David M. Clemen,

Do you have a reference for the last point you made (re. "Canada presently produces 60% of its total electrical requirements with hydroelectric power plants, and is installing new plants to produce 65% by the year 2012")?

Thanks!

Amy Keuhl

My reference source was Hydro Review magazine (March 2008, P 78) which quoted from "Canada's Energy Future: An Energy Market Assessment" produced by the National Energy Board. It stated "Under a baseline projection, hydropower would continue to be Candada's major source of electricity to 2015, increasing its share of electicity generation to 65% from about 60%."
Sorry about the mix up in years where I stated 2012.