EROWI - energy return of water invested

EROEI remains one of the most useful parameters that can be used for evaluating an energy technology, but it is not the only one. Another element is the need of water. Water is needed for irrigation of plants to be used as fuel and all large plants using thermal engines need water cooling. We can speak, then, of Energy return of Water Invested (EROWI). It is a concept much more recent than that of EROEI, but which is rapidly gaining attention and may be not less important.

Recently, Robert F. Service reported the comparative table that you can see reproduced at the beginning of this post. The data are taken from an article by Dominguez-faus et al. published in "Environmental Science and Technology" in 2009. Service's paper, as most of the studies published so far in this field, is dedicated to showing how water thirsty biofuels are. It is another drawback for a technology which has also a low EROEI, needs large areas, and competes for land with food production.

But the problem is more general and doesn't just involve biofuels. Nuclear plants, for instance, seem to be especially vulnerable to water scarcity. During the past few years, several plants had to be shut or slowed down, or allowed to drain water into rivers at higher temperatures than considered safe. A set of references on the troubles of nuclear plants during heat waves can be found here .

The problem may affect all thermal plants which are large and inefficient enough; coal plants for instance. According to Service's data, the problem can be eased moving from "once through" to "closed loop" cooling. But, if it were easy, there would be no "once through" plants. Evidently, closed loop cooling is more expensive and, in practice, the result of increasing EROWI may be to reduce EROEI.

Water is, of course, a renewable resource but a lot of the water used today is "fossil" water. It comes from deep aquifers which can be drained empty as it has happened, for instance in Saudi Arabia . In addition, climate change may further reduce the water supply in many areas of the world. How much these factors will affect energy generation worldwide in the near future is difficult to say at present, but surely the problem shouldn't be underestimated. The EROWI problem, in the end, is just an indication that we are hitting yet another limit of our finite environment.

http://europe.theoildrum.com/node/5923

http://www.sciencemag.org/cgi/content/full/326/5952/516

Wind? PV? Concentrated Solar Power?

My theory is the blind spot toward external costs on the manufacturing side, but that's just a wild guess.

Example?

"According to Service's data, the problem can be eased moving from "once through" to "closed loop" cooling. But, if it were easy, there would be no "once through" plants."

I don't think they were trying to claim it was "easy." I'm sure once-through is significantly easier and cheaper to engineer. If water use becomes more expensive, and/or regulations begin to require closed-loop, that equation could change.

Half of our water use goes toward energy production. It's a problem we badly need to solve.

But I don't think that article captures them at all. It reads more like a hit piece on thermal generation (something I really don't mind too much) instead of an attempt at objective evaluation. The example I used was obviously an unsupported conclusion and I believe it is representative of the entire piece.

If this topic is one you like reading on, you might enjoy this PowerPoint from NREL:
http://www.iea.org/textbase/work/2009/rewp_water/Young.pdf

Current Status of Interaction between Water Issues and Energy Efficiency & Renewable Energy:
New Technology Development & Potential Application in the Western U.S (4.3Mb)

The water consumption data (slide 18) actually appears higher than the table in the OP (multiplying by 4 to get liters/MWH). The "coal with carbon capture" projection was interesting. significantly higher water consumption.

"Withdrawal" as opposed to "consumption" is a topic that begs for unpacking. Just because it's "put back" doesn't mean it hasn't been altered, or made less potable, etc. For example, thermal pollution. Also, they mentioned "withdrawing from various sources and depositing on surface." That's a loaded little sentence.

relating to energy capture.

For example, I read a few years ago over on the Oil Drum, that Chinese steel manufacturing plants of that vintage used 46 times more water in making a ton of steel than plants here in the U.S.

Since water shortages are a problem in northern and western China, such an analysis might lead the Chinese to place water gobbling plants in the south, where more water is to be had, replace old plants with new more efficient plants or if water becomes expensive, move the plants here and concentrate on manufactures that use less water. After all, dry nations and regions effectively import water by importing food from wetter areas right now. As climate change and other factors reduce available, sufficiently clean water, one would think that drier countries and regions would be looking for opportunities.

FYI, large areas of U.S. corn and soybean production receive little or no irrigation in normal years.