It’s well-done to publish this, especially the link to the spreadsheet and to the other related links on the site, …. and we can see by the dates on the links and the files that you’ve been publishing on this topic for some time.

It’s well-done by Megan Hartman for putting together the sheet and the calculations, and it’s an interesting part of your presentation that you are able to present to a small place some of their own data when you speak.

I saw your presentation in Patagonia and now see this further followup on this watergy topic, which of course is only one of several topics that you covered very well.

As soon as you taught me the word “watergy”, a light went on with me, and to some extent with my colleagues.

I thought of it and think of it going in at least two directions:

1. water used in generating energy.
2. energy used in preparing water for use.

For the most part, your calculations above and on the other watergy [I note that the spell-check on this browser field does not process the word watergy....:-)] links on your site seem to bear on #1, and for a little while I thought #2 was absent. However, if we look for it, we can see that you cite Bruce Plenk’s extremely helpful numbers:

http://www.harvestingrainwater.com/wp-content/uploads/2009/10/Water-Conservation-Climate-Overview-Data-for-Tucson-AZ.xls.pdf

[Bruce Plenk, City of Tucson Solar Energy Coordinator]

% of City’s annual electricity consumption used to move water: 50% 2007-8
% of City’s natural gas consumption used to move/treat water: 88% 2007-8
% of City’s total energy consumption used to move/treat water: 44% 2007-8

The 44% total energy number is also here on this May 10, 2010 blog, above.

Even though it’s not highlighted, I’m glad to see this second part of the watergy issue brought out. It really set me to thinking when you provided this estimate.

On the first point, which is more the focus here, I have a comment and a question. My comment is that, amongst other things, this research helps bring out the strong need that we have to identify and use alternatives to solar thermal high-water-use. Perhaps there are lower-water-use methods. One person in California told me that generally when they propose projects there (or was it here?) that they don’t at this point propose solar thermal unless there is some alternative (even if less efficient) used to conventional water.

My question is to define “use”. In other words, if water is “used up” in the process of generating electricity at a coal plant, then how far away is that particular water from being rehabilitated to the point where it can be re-used. Does it necessarily have to be vented and found again “some day” or can it be processed efficiently and used to water plants or re-used directly over and over again in the coal plant?

Likewise for the other uses… would they each not have some level of nuance of how much they are used up and how much energy and other resources it would take to rehabilitate that water… and to what level of usefulness?

Going back to point #2, I think it will be good if you can fill in that data with even more data points from other cities and utilities and others…. I wouldn’t go looking for data that is the same… perhaps it will be dramatically lower or higher in other areas, as to how much energy is needed to move and process water.

Lastly, a math comment to Megan, I’m not sure but I’d be curious to tie the two sides together. That is:

- you use x number of gallons to generate useable energy.
- you then use y number of megajoules (or BTU or KWH or whatever… megajoules are the SI Unit I think) of energy to move/treat water.

- you then go back and use x number of gallons to generate use-able energy, but in so doing, you can see how many Megajoules are already a component of that x number of gallons. So, it’s as though you’ve used energy even before you’ve generated.

I don’t think this calculation can be done in a meaningful way at present, or maybe ever. At present, I think there needs to be a bit better perspective on point #2 (how much energy goes into preparing water for different types of uses and at what point in the value chain). For example, in his presentation, Brad said that the Tucson numbers should be understood as being after the water hits Tucson…. that is, it’s not even counting what it takes to get some of it to Tucson. So, that’s just one thing that makes me think it would be hard to do any meaningful math here…. and I don’t know ultimately if you can. We can be aware though that each gallon of water has in it an “energy expended component” to prepare it, just as we can be more aware that each Megajoule of Energy has a “gallons of water used to generate it” component.

I like this page,

jl