EROI of different energy sources

[swbluto]

So, in this thread, I want to discuss EROI or Energy Return on Investment. In classical financial investment, there's this concept called ROI. Basically, how much money do you make from investing a certain amount of money? A ROI of 100% is good because you just invested some amount of money and just doubled it. If you kept doing that over and over again, you'd be rich in no time!

The same thing can be done with oil. "In the beginning", conventional oil had an EROI of 20 to 1. That is, you invested 1 unit of energy and you got back 20 units of energy from oil. Essentially, FREE ENERGY! But, as conventional sources are exhausted and unconventional sources are tapped, the EROI is going down. I've heard it speculated that the EROI of the tar sands and such is 4 to 1, which is good, but nowhere near the return on investment from the bonanza of the "hay days". What you don't want is to get more energy than you put in, that is a ratio less than 1 to 1, because then you're losing energy and it's essentially not worth it unless you *need* oil for something other than energy.

So, what are the ROI of other technologies? If you took a certain amount of energy to create a solar cell, extracted energy from the sunlight using it, and over its lifetime you got back so much energy, how many more solar cells could be created from that energy? Is it 2 to 1? 20 to 1? Estimates? It'd be encouraging if it were positive thus energy growth could be sustained from solar cells, despite that it might take a long time to reach the current energy extraction rates of oil at present. It might not, however, depending if its EROI is high enough. What's the EROI of wind-mills and other technologies?

 

[dogman dan]

I don't know the exact numbers, but I have read arguments that PV solar has a pretty poor ratio. But such calculations may not be taking in all the benefits of cleaner energy or renewable energy into the calculation. Wind is said to be a bit better on the ratio I think, but both calculations depend on where the stuff gets located too.

What is it worth to lock in your energy costs for 20 years or more with the paper running articles about the latest rate increase? What is it worth to have your immediate locality have less coal or whatever being burned? What is it worth to not be dependent on a foreign country for your energy needs to heat and light your house? Some of these factors may make an even worse ratio worth the cost.

But the dream of making some solar panels, then taking the energy from them and making more solar panels is pretty much a dream. The ratio is said to be poor enough to make that not work well. Essentially, you have enough energy to make more panels, but not enough to divert any to light your house.

But converting oil into solar cells or wind farms may still be a good investment of the oil, since once built, a war in the wrong place can't cut your local supply of that energy, and you buy 20 years or so to keep working on fusion power or whatever.

 

[TylerDurden]

IIRC, from a practical standpoint, ROI for large-scale wind is about 10yrs, then you are making 'profit'... PV might be closer to 15yrs.

Like the Dog says, it depends somewhat how you base your analysis: current comparative costs or projected.

 

[dak664]

http://www.mdpi.com/1996-1073/2/1/25/pdf has a nice graphic on page 12.
Wind power at 20:1 EROI is comparable to current oil and gas production.
PV at 10:1 is comparable to nuclear power plants.

The article suggests that a minimum EROI of 3:1 is needed to sustain automobile-based transportation, when the energy inputs for making the vehicles, distributing fuel, maintaining the road, etc. are included.