# Invested energy vs price

1. Feb 1, 2006

### Ivan Seeking

Staff Emeritus
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?

Last edited: Feb 1, 2006
2. Feb 1, 2006

### 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.

3. Feb 2, 2006

### 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.

4. Feb 2, 2006

### PerennialII

Last edited by a moderator: May 2, 2017
5. Feb 2, 2006

### Staff: Mentor

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.

6. Feb 2, 2006

### Ivan Seeking

Staff Emeritus
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.

Last edited: Feb 2, 2006
7. Feb 10, 2006

### Ivan Seeking

Staff Emeritus
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.

8. Feb 10, 2006

### Pengwuino

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.

9. Feb 10, 2006

### Pengwuino

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!

10. Feb 11, 2006

### brewnog

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