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 Author: KRoth [ Fri Jun 01, 2007 1:40 pm ] Post subject: Embodied Energy Calculation for Electricity I am using the EIO-LCA tool and am also reading through the book associated with it ("Environmental Life Cycle Assessment of Goods and Services"). I have found apparent inconsistencies in the book when calculating the embodied energy in a kWh of electricity and want to make sure that I am using the correct value for MJ/kWh. Specifically, in one example, the electricity consumed is added back into the final energy used tally (chapter 14) but it is not in another example chapter 5) Which approach is correct - should one add in the electric energy or not when calculating the total impact of a kWh of electricity conumption? Details of the two examples: In Chapter 5 of the Book (p.53-54), e.g., for the first washer: kWh/year=2*8*52= 832kWh/year*10 yr = 8,320kWh/life. Using a value of \$0.08/kWh, yields \$666 of lifetime expenses and, using the value in the model at that point in time of ~100 TJ/\$MM, yields the total energy from use only = 0.067TJ=67,000MJ (Table 5-4). ->~8.1MJ/kWh. In Chapter 14 (p. 142-143): Using a value for \$/kWh (\$0.069; that is probably a typo - \$0.08 would yield the revenues shown) and residential consumption of 1,100,000 MWh, it estimates revenues of \$89 billion. Based on the model alone, it multiplied the revenues by ~100 TJ/\$MM (the conversion factor in the model back then) to obtain ~9*10^6 TJ. Subsequently - and this is the key difference from the example in Chapter 5 - it [b]added[/b] the electricity consumed in residences, i.e., 1,076,000MkWh (actual EIA value)*3.6MJ/kWh = ~3.9*10^6TJ to the energy calculated by the model to get a total value of ~ 13*10^6 TJ. -> ~12MJ/kWh. (note: I realize that the conversion for Power Generation & Distribution has changed to ~121TJ/\$MM) In addition, I am attempting to use a solid value for the embodied energy of natural gas. The Ch. 14 example also indicates that the energy value of the natural gas equals distribution + the NG energy itself. It does not appear to, however, include the energy consumed to extract and clean up the natural gas - is that neglected because it is generally much smaller than the other factors? The extraction energy would appear to be part of the embodied energy. I appreciate any clarification people can offer.

 Author: marriott [ Mon Jun 04, 2007 2:36 pm ] Post subject: Kurt - We are in the process of working on the different points in your question. We haven't settled on a full response, but here is some preliminary findings. So, there are some errors in the book, pg. 142. 1) \$89 B implies a value of .081 \$/kWh. The correct value should be \$75.9 B at .069 \$/kWh. 2) When ONLY accounting for the electricity used in the supply chain, the statement made in paragraph 2 of "Use Phase" section is correct - you must add 1.1 BkWh to the 16,300 MkWh* used producing that electricity. 3) The book says 1.1 MkWh in the last line of the 2nd paragraph. It should be "BkWh", but the statement is generally correct. However, if what you're trying to arrive at is a value for Total Energy, that value is already included in the 10.8M TJ (embodied in the values for coal & natural gas pre-combustion)* and adding the energy embodied in the delivered electricity IS double counting for energy. * I ran EIO-LCA with \$89B in the 1997 PG&S sector Some of the confusion comes from the fact that Luis' table was not meant to be an accounting table...the numbers aren't necessarily additive. 2nd question: Natural gas extraction is included in the life-cycle energy for natural gas distribution. Summary and bottom line: There are enough errors in this section that we are double checking the values, but it appears that the approaches in chaps. 5 and 14 are the same, but poorly worded enough to make that non-obvious. More to come... -Joe

 Author: KRoth [ Wed Jun 13, 2007 11:17 am ] Post subject: Joe - Thank you for your reply - I appreciate it! One clarification: how do you define "Total Energy"? Does it mean "total energy consumed throughout the supply chain"? Assuming that this is the case, and using following values: *\$90.7B residential electricity revenues in 1997 (from EIA; http://www.eia.doe.gov/cneaf/electricit ... at7p3.html) *1,076,880,098 MWh of residential kWh sold in 1997 (from EIA; http://www.eia.doe.gov/cneaf/electricit ... at7p2.html) *121 TJ / \$1MM for the most recent Power Generation & Distribution EIO-LCA value this should yield an embodied energy (i.e., delivered energy + energy for extraction, production and distribution) value per kWh of: =(90,700 [\$MM] *121 [TJ/\$MM] * 10^6 [MJ/TJ])/1,076,880,098 [MWh]/10^3 [kWh/MWh] + 3.6 [MJ/kWh] = 13.8 MJ/kWh Is that correct? --Kurt