In physics, energy economics and ecological energetics, EROI is energy returned on energy invested (EROEI or ERoEI); or energy return on investment (EROI).
“It is the ratio of the amount of usable energy acquired from a particular energy resource to the amount of energy expended to obtain that energy resource. When the EROEI (Energy Returned on Energy Invested) of a resource is less than or equal to one, that energy source becomes an “energy sink”, and can no longer be used as a primary source of energy.” (Wikipedia)
It’s possible to measure the EROI over time for each form of energy from various fossil fuels to hydro electricity and get a grasp on the real cost of that energy resource. If the ER or Energy return over time narrows to the EI or Energy Invested over time it may eventually get to the point where capital investment doesn’t have a high enough return to make it worthwhile. An example might be that during the early days of oil exploration when all anyone had to do was just about put a pipe into the ground and clean crude bubbled or gushed out EI was very little while the ER was huge (say 100 to 1) Lots of oil for a low cost. Recently, we find that with the BP oil explorations in the Gulf of Mexico or the tar sands oil from shale in Alberta, the EI is quite high for the amount of oil that results (ER) (it has narrowed so that the rate of return especially for the shale oil might be 10 to 1).
If you like this kind of analysis and would like to apply it to big hydro, here’s a link to an interesting open source article published in Sustainability we would like to share with you. It’s a bit over our head so we’re counting on some of you to take a look and let us know what you think. Warning = statistical analysis required.
Wikipedia continues on EROI in “that a related recent concern is energy cannibalism where energy technologies can have a limited growth rate if climate neutrality is demanded. Many energy technologies are capable of replacing significant volumes of fossil fuels and concomitant green house gas emissions. Unfortunately, neither the enormous scale of the current fossil fuel energy system nor the necessary growth rate of these technologies is well understood within the limits imposed by the net energy produced for a growing industry. This technical limitation is known as energy cannibalism and refers to an effect where rapid growth of an entire energy producing or energy efficiency industry creates a need for energy that uses (or cannibalizes) the energy of existing power plants or production plants. (Info: In our words what does this mean in terms of big hydro and its sustainability which we believe is not the case and is it just the new flavor of the month taking from fossil fuels but not really adding anything of significance. What energy does big hydro cannibalize if indeed it does? See the previous posting of Christophe Courchersne’s (from the Conservation Law Foundation) interview with Brian Tilton that goes over the multitude of external impacts and expenses of Hydro Quebec.