watt hours and gallons

[Mark Gilkey]

BruceK questioned some statistics on energy savings that the water group cited during their presentation.

 

I found an SCVWD document that talks about how much energy can be saved by conserving water: http://www.valleywater.org/conservation/media/Documents/WUE%20Water%20Energy%20Report.pdf

 

The SCVWD says that over the last 13 years they saved about 370,000 AF (acre feet) of water through conservation and recycling, and that this saved 1.42 billion KWH of electricity.  If I didn't goof, that works out to about 17 watt hours per gallon.

 

1.42 billion KWH

--------------------------------------------------- = approx 17 watt hours per gallon. 

370,000 AF * (320,000 gallons/AF)

 

That's what I've come up with so far.  If you've got another set of data or calculations that you'd like me to look at, please let me know.

 

--mgilkey

[Marn-Yee Lee]

Here's the spreadsheet that we used.  We forgot to multiple the average daily usage in gallons with 365 days to match the annual electricity numbers from the Palo Alto and Mt View processing plants.   The revised number comes out to 1.94 watt-hour/gallon.  This does not factor in conveyance from the Sierras.

I think we should probably quote the number you found too.

Thanks for the tip,
Marn Yee

--
Marn-Yee Lee
beingsustainable.blogspot.com
busythinking.blogspot.com.

[steve bishop]

I get about 12watts.  I'm wondering if I'm doing this wrong.

Steve

[Mark Gilkey]

I'm getting about 12, too.  I think when I did the calculation the first time I got "0.0119" and misread that as "0.019" (i.e. my eye, brain, or fingers skipped a "1". 

 

I apologize.

 

--mgilkey

[Mark Gilkey]

I mean "0.0117" and misread that as "0.017".

 

The reason for the difference between "0.0117" and "0.0119" is easy t explain -- I initially used 320,000 gallons per acre foot (from memory) and later used a more precise figure of 325,851 gallons per acre foot.    The difference between 0.0117 and 0.0119 is insignificant, but the difference between 17 and 19 is more significant.

 

Anyway, the main point is that we're getting about 12 watt hours per gallon, not 700 watt hours per gallon.  I still haven't figured out where the 700 watt hours per gallon came from.

 

--mgilkey

[steve bishop]

Cool.  Many thanks for checking our number on this.  The 710 figure came from a previous calculation error.  We'll need to fix that since our document is showing up in google search results.

Steve