What is the relationship between price and invested energy in products?

[Ivan Seeking]

This has come up a number of times and seems like the sort of things that engineers might study, hence the choice in forums.

Consider the total energy invested in any system or device; call it a product. Be it a dam, a nuclear power plant, a car, or a birthday cake, there is necessarily a relationship betweeen energy invested and the final price of that product. For example, if we consider the user level price and the energy invested in an aluminum can, knowing that aluminum requires a great deal of energy to produce, it seems reasonable to assume that most of the production price represents the energy invested in the can, and then we allow for some multiple of that as a point of sale vs production price, rate of profit. But even labor intensive products represent an energy investment. That is to say that a person has some measure of energy efficiency, and normally we need things like light, heat, [coffee], we have to drive to work in a car that has a finite lifespan and that requried energy to produce, and that requires fuel, tires, oil, etc. So it starts to appear that a standard relationship might exist. So, is there a known or typical relationship between price and invested energy, in any product, in joules per dollar?

 

[Pengwuino]

I have actually seen just that! I remember seeing something god knows where where they showed a few products and their average energy consumption/unit created. They had gone from mineral mine to packaging. I don't remember what it was but surely someone has done it before.

 

[FredGarvin]

Interesting concept. I can't say I have ever seen any analysis on the basis of energy. I am used to seeing the average time studies. You have me wondering just how this would be done. It really would give a different outlook on, for the lack of a better phrase, the efficiency of a thing's existence by doing so. For example, say one of our engines would provide a total amount of energy over it's rated life. Then divide that by the amount of energy required to build and maintain it for that life. I think that would be an interesting argument for someone's reason for doing something.

I'm going to ask around to see if anyone here has heard of this.

 

[PerennialII]

... sometime during undergrad times took some materials classes where materials selection criteria involving also energy-cost aspect swere touched, say like in here:

http://www-materials.eng.cam.ac.uk/mpsite/interactive_charts/energy-cost/NS6Chart.html

... considering products, sounds a bit like 'life cycle analysis', LCA (or life cycle management perhaps)?

http://www.agrifood-forum.net/practices/lca.asp
http://www.gdrc.org/uem/lca/life-cycle.html

 

[russ_watters]

Interesting concept. I can't say I have ever seen any analysis on the basis of energy.

Me neither (*caveat), but I can see why it would be a useful concept. My boss isn't big on hybrid cars because he believes (on what basis, I'm not sure) that the extra cost of the car translates directly into more energy being required to build it.

*Caveat - isn't that what "well-to-wheels" efficiency is? For fuel it is an important concept (how much fuel you have to use to produce the fuel to use), but for other products it could be useful as well.

 

[Ivan Seeking]

Yes, a biology professor first suggested this idea and he even claimed that one can compare alternative energy sources to petro, nuclear, coal, ect, directly in this way. If, for example, solar panels are expected to fail right about the time that they pay back the financial investment, which is typical, then most likely you ultimately heated your house with the energy used to build the solar panels, with a net zero gain. And I think this is just an extension of the well-to-wheels idea; maybe crossed with life cycle analysis, and financial analysis.

 

[Ivan Seeking]

We've often heard the myth that "it takes more electricity to manufacture a solar panel than it will ever put out." This is simply not true...this myth may have started during the Ronald Reagan era. This is of course a very difficult statistic to calculate, but according to the National Renewable Energy Laboratory in Golden, CO, a study has been done to answer the question. The study found that single-crystal panels reach the energy payback point in 5-10 years, polycrystalline panels in 3-5 years, and amorphous silicon panels in 0.5-2 years. Be advised that because the question is so vague, there is a large margin of error for these figures! We just discovered a recent, very detailed study about solar panel energy payback time in the January 2001 issue of Home Power magazine. This study, by Karl Knapp, PhD, and Teresa Jester, finds payback time for a standard module to be about 3.3 years, and 1.8 years on a thin-film panel. The study factors in energy costs for ALL parts of the panel and manufacturing process.

http://www.otherpower.com/otherpower_solar_new.html

I wonder how comprensive this study really was. Of course it could be that it was true [well, that there was no net energy gain] but is no longer.

 

[Pengwuino]

http://www.otherpower.com/otherpower_solar_new.html

I wonder how comprensive this study really was. Of course it could be that it was true [well, that there was no net energy gain] but is no longer.

Yah, mid-80's technolgoy vs. now sounds like it could have been a tremendous change in efficiency. I vaguely remember someone saying solar power was something like .1% in the 70's. What are PV panels doing now? 20%? I hear a pretty big range when talkinga bout current PV technology: from 15%-22% depending on who i talked to.

 

[Pengwuino]

Yes, a biology professor first suggested this idea and he even claimed that one can compare alternative energy sources to petro, nuclear, coal, ect, directly in this way. If, for example, solar panels are expected to fail right about the time that they pay back the financial investment, which is typical, then most likely you ultimately heated your house with the energy used to build the solar panels, with a net zero gain. And I think this is just an extension of the well-to-wheels idea; maybe crossed with life cycle analysis, and financial analysis.

I think the professor missed the point though. The only real reason we are switching to alternative energies is because of the pollutants which is the real comparison that needs to be done. I mean if gasoline didn't produce any pollutants! Geez!

 

[brewnog]

I think the professor missed the point though. The only real reason we are switching to alternative energies is because of the pollutants which is the real comparison that needs to be done. I mean if gasoline didn't produce any pollutants! Geez!

That and the fact that we're running out of fossil fuels rather rapidly...