“Be kind, for everyone you meet is fighting a hard battle” - Often attributed to Plato but likely from Ian McLaren (pseudonym of Reverend John Watson)

Friday, September 23, 2011

A tonne of coal

It's been a hot few weeks in Southern California and, unfortunately, I like it chilly. Thus, my air conditioning system has been quite busy lately. I received my utility bill yesterday and, though I knew it would be high, it exceeded my expectations. Anaheim Public Utilities bills on a bi-monthly basis and my current bill represents 62 days of consumption. The total electrical usage was an eye-popping 4,473 kilowatt hours. This is an average rate of a bit over 3 kilowatts continuously. Ouch!

Along with our bill, we receive a "power content label" that tells us the energy resources used to supply our electricity and the percentage (estimated for 2010 and I used these estimates for the information to follow) of electricity supplied by each.

Let's take a look at coal: I entered the query "how much coal is burned to produce a kilowatt hour of electricity?" into Google and followed a link to this site. It could be that I should look at a variety of sources but, for my purpose in this post, this is close enough. There I found that a ton (a short ton) of coal, burned in a modern generating facility, will yield 2,460 kilowatt hours of electricity. I will assume that its transmission to my house is 80% efficient, so that ton will yield 1,968 kilowatt hours at my service entrance (where the meter is). This converts to 2.169 kilowatt hours/kilogram of coal burned.

Looking at the Power Content Label, 65% of my 4473 kilowatt hours, or 2,907 kilowatt hours were supplied by burning coal. Yes, I understand that, for these particular 62 days that might not be the right percentage, but it's the best number I can find. In any event, these 2,907 kilowatt hours required the burning of 1,340 kilograms, or 1.34 metric tons ("tonnes" - note that this is 1.48 "short tons" or 2,954 pounds) of coal. This is 21.6 kilograms/day of coal being burned to keep me cool, pump my pool water, light my house, entertain me, etc. Looking here, I see that a reasonable approximation (not knowing the nature of the coal being burned) of the density of the coal is 1000 kg/m^3 so, during the 62 days, about 1.3 m^3 of coal was burned to supply me with 65% of my electricity needs.

Frankly, I was surprised by the high percentage of coal estimated to be used by Anaheim Public Utilities to supply electricity. We have two large nuclear generating facilities in Southern California as well as a huge plant west of Phoenix, AZ. Further, Hoover Dam is about 300 miles away.

Before I purchased the Lexus CT 200h, I'd contemplated, among other vehicles, the Nissan Leaf. While that vehicle would definitely have reduced my driving costs per mile, I'm now suspecting that it wouldn't have reduced my vehicular carbon footprint. That estimate will be the subject of my next post.

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