Thursday, January 21, 2010

Energy Calculations:

Putting Energy Claims in Perspective

I approach this topic with a bit of trepidation, as I didn't do enough checking on some statements I reported a few weeks ago and discovered I had reported some misinformation. Nevertheless, I discovered an article the other day that was so interesting, I wanted to share it.

The article, entitled "Biofuels Aren't Really Green," comes from the IEEE Spectrum, a respected publication from a large and highly respected professional society, so I hope the information is reliable. The article takes a hard look at the resource requirements, especially for land and water, for various energy sources, and contrary to the current hype about biofuels, they don't look like good actors. A switch to 100% use of switchgrass for all our energy needs, electricity, transportation, and heating fuel, would require almost twice the landmass of the earth and a volume of water over 1-1/2 times the annual rainfall (assuming that the entire world in 2030 uses energy at today's US per capita energy assumption).

Now, we all know that these assumptions are pretty extreme. Still, it is instructive to me to look at some of the real limits of different energy sources. What makes the article really interesting is that it also provides land and water requirements--and carbon emissions--for some other mixes of energy resources. My only criticism is that it shows only those three parameters, and shows the calculations for only four scenarios (all switchgrass, all photovoltaics, a "balanced portfolio," and business as usual). Thus, other impacts, such as total cost, are not considered, nor is it possible to determine such things as whether they have factored in the storage and/or "smart grid" requirements for a scenario of 100% photovoltaics.

In a similar vein, an article called "Bioelectricity Promises More "Miles Per Acre" than Ethanol," published in the Carnegie Institution of Sciences newsletter, calculates the miles per acre for an electric vehicle deriving its electricity from a power plant using biomass versus the miles per acre for a vehicle running on ethanol. Bioelectricity beats ethanol by nearly a factor of two (15,000 miles per acre versus 8,000 miles per acre). This article doesn't address the land and water use for bioelectricity versus nuclear power or other electric power sources.

Despite the lack of completeness in each case, overall, I think these articles are a good start and an interesting way to look at things. I was particularly excited to see that the IEEE Spectrum article provides a "calculator" that allow readers to enter their own sets of assumptions and see what happens. Unfortunately, I have not yet been able to get the calculator to work. I would be interested to hear from readers if they are able to get the calculator working, and if so, what their experiences are in using it. In particular, I'd be interested to know how the results of their calculations stack up with other available projections of the impacts of different energy technologies and different mixes of technologies. If the projections are reasonably accurate, I think the tool can be a powerful way to help educate the general public that there is no such thing as a free lunch. Technologies that seem to be natural and benign may have inordinate land or water requirements, while others that at first blush seem less natural and benign may actually have a smaller environmental footprint.

It will be interesting to see more of this type of analysis emerge.


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