Managing the Peak Fossil Fuel Transition: EROI and EIRR  

Posted by Big Gav in , , ,

The Oil Drum has a post from Tom Konrad looking at the concepts of EROI and EIRR and how they impact the transition to a post-oil world - Managing the Peak Fossil Fuel Transition: EROI and EIRR.

Energy keeps our economy running. Energy is also what we use to obtain more energy. The more energy we use to obtain more energy, the less we have for the rest of the economy.

The concept of Energy Return on Investment (EROI), alternatively called Energy Return on Energy Invested (EROEI) has been widely used to quantify this concept. The following chart, from a SciAm paper, shows the EROI of various sources of energy, with the tan section of the bar representing the range of EROIs depending on the source and the technology used. I've seen many other estimates of EROI, and this one seems to be on the optimistic (high EROI) end for most renewable energy sources.

The general trend is clear: the energy of the future will have lower EROI than the energy of the past. Low carbon fuels such as natural gas, nuclear, photovoltaics, wind, and biofuels have low EROI compared to high-carbon fuels such as coal and (formerly) oil.

The graph also clearly shows the decline in the EROI over time for oil. Other fossil fuels, such as coal and natural gas, also will have declining EROI over time. This happens because we always exploit the easiest resources first. The biggest coal deposits that are nearest to the surface and nearest to customers will be the first ones we mine. When those are depleted, we move on to the less easy to exploit deposits. The decline will not be linear, and new technology can also bring temporary improvements in EROI, but new technology cannot change the fact that we've already exploited all the easiest to get deposits, and new sources and technologies for extracting fossil fuels often fail to live up to the hype.

While there is room for improvement in renewable energy technologies, the fact remains that fossil fuels allow us to exploit the energy of millions of years of stored sunlight at once. All renewable energy (solar, wind, biomass, geothermal) involves extracting a current energy flux (sunlight, wind, plant growth, or heat from the earth) as it arrives. In essence, fossil fuels are all biofuels, but biofuels from plants that grew and harvested sunlight over millions of years. I don't think that technological improvements can make up for the inherent EROI advantage of the many-millions-to-one time compression conveys to fossil fuels.

Hence, going forward, we are going to have to power our society with a combination of renewable energy and fossil fuels that have EROI no better than the approximately 30:1 potentially available from firewood and wind. Since neither of these two fuels can come close to powering our entire society (firewood because of limited supply, and wind because of its inherent variability.) Also, storable fuels such as natural gas, oil, and biofuels all have either declining EROI below 20 or extremely low EROI to begin with (biofuels). Energy storage is needed to match electricity supply with variable demand, and to power transportation.


Bob Wallace   says 12:51 PM

Why does a coal plant have a 50 year lifetime and a wind farm only 20?

Both involve spinning magnetic fields, just use different energy sources. Do not bearings wear out in coal plants and need to be replaced? Do steam turbines not need to be rebuilt from time to time? Do boilers and fuel feed mechanisms run for 50 years without needing replacement and rebuilds?

The concrete footing and steel tower of a wind turbine will last just as long as the concrete and steel of a coal plant. The parts that wear and fatigue can be swapped out.

True, it might make more sense, 20 years down the road, to swap out the wind turbine with some new, more efficient design, but the same can happen in a coal plant as technology advances. More than one coal plant has received turbine swaps in order to increase efficiency.

And solar fields. Sure over time the efficiency of the panel drops. And at some point there might be enough residual value in the footings, rack, and transmission lines to justify replacing the panels. Especially a decade or two from now when solar panels should be a small fraction of today's cost.

But is that a "lifetime" or a maintenance/upgrade event?

Bob Wallace   says 1:23 PM

There is one very "round trip" efficient storage method that is rarely discussed, hydroelectric uprating.

This is nothing more than adding additional turbines to an existing hydroelectric dam and using the power, not on a 24/365 basis but as backup dispatchable power for solar, wind, etc.

The idea is, if you experience a need for large amounts of power 1/3rd of the time you take a dam whose storage/flow will support one turbine on an always on basis and add a couple more. Build enough wind/solar to make up for the single turbine which will be shut down when the wind is blowing, sun shining.

Then when supply from other sources are low you fire up all three turbines.

This system is 100% efficient as the dam is refilled from normal stream flow. There is no need to pump up.

It's all in the timing....

(Neural Energy is a great reference site. Lots of info, very well written.)

Anonymous   says 3:26 PM

Did you see the latest Scientific American plan (click to page 3) to wean the world off fossil fuels in 20 years? It made the GREAT point that with economic growth the 12TW we use today would become over 16TW (in all energy forms), but by converting the oil based transport system to electricity we'd cut the ACTUAL energy required from 16TW to 11TW.

This is a point I used to try to make with some of the doomers on SPO and ROEOZ.

Oil based transport fuels only get 10% of all that "high EROEI" energy to the wheels, so what's the big deal? I'm wondering if all the fuss over oil's high EROEI is wildly exaggerated.

Sure if you burn it you get a lot of heat, and to get solar PV (or other renewable you want to pick on) to produce that kind of heat, well, that's gonna take a whole lot of Solar PV isn't it?

But what if we don't want heat, we want forward motion? What if 'heat' energy is irrelevant because we're using electrons directly in a new Train,Tram, or Trolley bus or even Electric Vehicle transport system?

So I guess what I'm asking is do these ERoEI systems accurately account for new, ultra-efficient ELECTRIC transport systems in a post-oil world? Or do they just assume, like so many other doomers do, that today's transport system is all there is and all there could possibly be, and just WILL BE the way we mine ore, transport goods and get around in a post-oil world?

It seems a simplistic and dishonest assumption designed to reach a predetermined conclusion: that nothing can be as good as fossil fuels.

Hi Dave - yes - I've seen the SciAm article - its excellent.

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