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PostPosted: Mon Jul 12, 2010 4:19 pm 
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I am trying to estimate the energy used in various input sectors in the supply chain for a given sector (as defined by a 6-digit NAICS code).

When you look at the top-10 most energy intensive sectors in the supply chain, the first or second sector is usually "Power generation and supply (NAICS code 221100). Since I am not interested in the energy consumed in the power sector itself, I want to to allocate the energy consumed in the Power generation and supply sector to all other input sectors of the economy. To do this, I divide the energy consumed in the power sector proportionally to all other sectors of the economy.

An example might help over here. For the sector "Pump and pumping equipment manufacturing" NAICS Code (333911), the energy use for top-6 sectors for every $1million in production output looks like this:

Sectors Total Energy (TJ)
Total for all sectors 8.49

Power generation and supply 2.53
Iron and steel mills 1.42
Pump and pumping equipment manufacturing 0.708
Ferrous metal foundaries 0.393
Alumina refining and primary aluminum production 0.273
Truck transportation 0.268

Here I want to divide the 2.53TJ for power generation and supply among all input sectors of the economy. Here is the math for the iron and steel mills sector:

power generation and supply for iron and steel mills input sector =
Energy used by power generation and supply * Energy used by Iron and steel mills /(Total energy use by all sectors - energy used by power generation and supply)
= 2.53 * 1.42/(8.49 - 2.53) = 0.603 TJ
So, total energy used by iron and steel mills (including power generation and supply) = 1.42 + 0.603 = 2.02 TJ

Similarly, for pump and pumping equipment manufacturing,
power generation and supply portion of energy use =
2.53 * 0.708/(8.49 - 2.53) = 0.3 TJ
So, total energy used by pump and pumping equipment manufacturing (including power generation and supply) = 1.008 TJ

Thus, the new energy consumption table will look like this:

Sectors Total Energy (TJ)
Total for all sectors 8.49

Power generation and supply (included within other input sectors)
Iron and steel mills 2.02
Pump and pumping equipment manufacturing 1.008
Ferrous metal foundaries 0.1667
and so on....

Then, percentages of energy used in input sectors could be calculated as follows:
Iron and steel mills (2.02/8.49)*100%
Pump and pumping equipment manufacturing (1.008/8.49)*100%
Ferrous metal foundaries (0.1667/8.49)*100%

I have two questions regarding my estimates as described above:

1. Is is okay to assume that the energy consumed in the power generation and supply sector (2.53TJ) for every $1million of output of pumps, equivalent to the energy consumed by all input sectors of the economy from external energy sources (like electricity, natural gas, oil, coal, nuclear and other forms of energy included in the power generation and supply sector)? If this assumption is correct, then energy losses in the production and delivery of power is also included in the total energy consumed by all input sectors (2.53TJ), which is what I want.

2. If assumption 1 is correct, then is it okay to proportionally divide the power generation and supply energy use across all input sectors based upon the level of energy use in each input sector? I am looking for a ballpark figure and not something exact to the nth degree here. Is there a better, and simpler, method to estimate this? Is there a more complicated method to measure this and what is the difference in accuracy between the two methods?

3. How can I estimate the energy consumed within the power generation and supply sector to produce its output (i.e., generate and distribute 2.53 TJ of power to all input sectors). According to my understanding, this value would represent the energy losses in the production and distribution of energy to all input sectors.

Please feel free to also make any comments relevant to the above discussion which may or may not directly answer my questions. I am also curious to find out if others out there have also done a similar calculation.

Thanks!


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PostPosted: Mon Jul 12, 2010 6:19 pm 
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Thanks for your post.

To start with, I don't understand fundamentally WHY you are trying to do what you're doing. Understanding that would help reply.

THe whole point of an input-output based model is to get an estimate of all the impacts across the supply chain. So why don't you care about the power sector?

That said, if you look at the "Energy" category of effects shown on the website, each row of each sector of results already shows you how much electricity they use. All the "power generation" row shows is what went into making that electricity by that sector (this fact also helps with your question 3 - which you are trying to figure out efficiency of electricity production).

In your example below, I also don't follow your equations. In the first one, why are you taking the total energy across all sectors (column 1, in TJ) of 8.5 and subtracting off the power gen value only?

If you are going to do something like you propose, it should be using fractional shares of the electricity use column, I would think, not the total energy in TJ column..

Again, if I understood why you were trying to do this, it might help with an answer. It seems though you are making this way too complicated - I think the data you need/want is already being shown and you aren't using it!

-scott


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PostPosted: Tue Jul 13, 2010 9:21 am 
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Scott, thanks for your reply.

If I understand correctly, the energy consumed in the power generation and supply sector is the energy used to produce and distribute the total energy required to produce the $1 million of output. If this is correct, then the average efficiency of the power generation and supply sector = useful energy produced / total energy used
= (8.49 - 2.53) / 8.49 = 0.7 or 70%

Interestingly, for a selection of 10 unqiue output sectors (e.g. air and gas manufacturing, aircraft manufacturing, etc.), the average efficiency of power generation and supply sector comes to 0.697 (range is 0.63 to 0.74). So, on average, power generation and supply is about 70% efficient across the U.S. economy. I am not sure if this is a reasonable value, but would welcome any comments on this.


The other part of my analysis is to sort input sectors by energy consumed accounting for losses in the power generation and supply of energy which is why I was doing the calcuations in my original post. In energy lingo, this value is sometimes referred to as "source energy consumption" (as compared to site energy consumption which does not account for energy losses in the generation and supply of power). I am only looking at manufacturing sectors and want to calculate the "source energy consumption" for each input sector. It seems there are two ways of calculating this value:

(1) Divide the energy consumed in the power supply and generation sector propotionally across all input sectors

(2) Add 30% to the value of energy consumed by each input sector (based upon average efficiency of power generation and supply sector of 70%, as described above).

Are both of the above methods correct? I would think method (1) would provide a more accurate value source energy consumption than method (2) above.

Thanks again!


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PostPosted: Tue Jul 13, 2010 9:28 am 
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I think you ARENT understanding, so I will try again.

first though - have you used the tutorial? It tries to explain this. We are updating the format of it but its still linked at:

www.eiolca.net/tutorial-j/tut_1.html

Each row of the results only show what that sector's contribution is to the total impacts across the supply chain. Thus the power gen sector only shows how it uses energy to make electricity. The pumps sector shows the energy needed to make pumps.

I note part of my problem following your comment is that you are using the words energy and electricity almost interchangeably (eg you said:

Quote:
"the energy consumed in the power generation and supply sector is the energy used to produce and distribute the total energy required to produce the $1 million of output".


In this specific context, its potentially a communication problem. That might be the root of the problem here?


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PostPosted: Tue Jul 13, 2010 10:30 am 
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Thanks for clarifying the difference between energy and electricity use. And yes, the quote should really be:

"the energy consumed in the power generation and supply sector is the energy used to produce and distribute the total ELECTRICTY required by all input sectors to produce $1 million of output".

(One subtle detail is that some power plants with combined heat and power generation units provide both electricity and heat as outputs, but we can ignore this detail for now)

I have gone through the EIO-LCA tutorial and have read some of the background information regarding this methodology. The only thing that was confusing to me was how to interpret the energy consumed within the power generation and supply sector. If you have a document or background paper describing how the economic numbers (dollars) are converted into energy numbers, together with a description of the data source it uses, please provide a link to it if possible. I couldn't find one on the website.


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PostPosted: Thu Jul 22, 2010 9:44 pm 
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Even with that definition, your numbers dont work out. You are looking at both the total energy used in the supply chain, as well as that of just the electricity sector.

so When you subtract the 8.49 - 2.53 TJ, I dont understand why. The power generation row tells you the energy needed to make electricity. Each of the other rows tells you how much energy needed to make that product. So your efficiency calculation makes no sense because you're looking at some random metric of energy usage across production in all sectors.

Anyway, the documentation is posted at:

http://www.eiolca.net/forum/phpBB2/viewtopic.php?t=216


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PostPosted: Sun Sep 19, 2010 10:10 pm 
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It really useful for me, thanks for the info that you guys have been discussing.

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PostPosted: Sun Sep 19, 2010 10:11 pm 
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It really useful for me, thanks for the info that you guys have been discussing.

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