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Archive for the category “eroi”

Should Storage be Included in EROI Considerations?

Article discusses the question whether storage should be part of EROI considerations and calculations. Take-away points:

1. A shift from an electrical system based mostly on energy stocks (with built-in energy storage function) to one based mostly on natural flows (with the construction of storage devices required to ensure large-scale availability) will probably be constrained by the energetic demands of the VRE-storage subsystem. Or in other words, high penetration of VRE will require the large-scale deployment of storage solutions, but there might be biophysical limits to how much storage can be deployed if the energy system is to remain viable.

2. Lithium-ion batteries, which are the fastest growing form of electrical storage today and are increasingly being touted as capable of supporting the energy transition to renewables, could probably only usefully contribute a short-term role to buffering VRE. The energetic productivity/EROI of an energy system reliant on lithium-ion batteries (and other similar electro-chemical storage devices) would indeed rapidly fall below the minimum useful EROI for society. The energetic requirements of pumped hydro storage, on the other hand, are sufficiently low to enable a greater displacement of conventional generation capacity and penetration of VRE, but wide scale deployment is dependent upon regional topography and water availability.

3. Storage technologies that would enable a full displacement of conventional generation capacity and 100% penetration of VRE at the current system reliability level are, as of today, unavailable. New storage solutions may emerge as a result of current and future research activities, but in order to assess their potential it will be necessary evaluate their energetic performances within the VRE-storage subsystem, all along the energy transition pathway. Only if these performances are markedly superior to existing technologies will storage potentially constitute the ‘holy grail’ of the energy transition that many expect.

VRE = Variable Renewable Energy.
EROI/EROEI = Energy Return On (Energy) Investment

[] – Storage is the ‘Holy Grail’ of the Energy Transition – or is it?

EROEI Of Photovoltaics

Upbeat news regarding EROEI values for photovoltaics. From the conclusions:

Improvements in PV technologies over the last decade have brought about notable increases in their EROI. When calculated in terms of the electricity output per unit of primary energy invested (Eq. (2)), The EROIel of PV ranges from 6 to 12, which makes it directly comparable to that of conventional thermal electricity without CCS (4–24).

When instead calculated according to the often employed formula EROIPE-eq=T/EPBT (Eq. (4)), i.e. expressing the energy ‘returned’ by PV in terms of its ‘Primary Energy equivalent’, the EROI of PV is up to 19–38, which puts it squarely in the same range of EROI as conventional fossil fuels (oil in the range 10–30; coal in the range 40–80).

These new results prove that PV is already a viable energy option that may effectively contribute to supporting our societal metabolism, while significantly reducing the depletion of the remaining stocks of non-renewable (fossil) primary energy, and mitigating the concurrent environmental impacts in terms of global warming and polluting emissions.

However, even these remarkable results should not allow one to forget that PV, like all other renewable technologies, must still be supported by an initial investment of primary energy, which is, as of today, of fossil origin. We therefore argue that available monetary and energy resources should be funnelled in the right direction without delay, lest not enough high-EROI fossil fuels are left to support demand during times of gradual shift to renewable resources.

[] – The energy return on energy investment (EROI) of photovoltaics: Methodology and comparisons with fossil fuel life cycles. June, 2012.

EROEI of Methane Hydrates

In the wake of the recent posts about methane hydrates, the overarching question is, as with any new energy source, what is the energy return on energy invested (EROEI) for these hydrates? In fact early indications are quite promissing: values of more than 30 initially, gradually deteriorating to 7 after 30 years of well exploitation:


[ – pdf]
[mirror – revised nov 2012]

Net Energy Wind Turbines

Every now and then you hear the argument made that wind energy should be rejected on the grounds that wind turbines have a negative net energy, meaning that it would cost more to build a turbine than it will ever return in energy terms. Additionally the claim is heard that fossil fuels are needed to build and maintain a wind turbine.

Here is a US government (DoE) document specifying a standard 5 MW offshore wind turbine (“NREL offshore 5-MW baseline wind turbine”).


In page 2, table 1.1 we find:
Rotor mass – 110,000 kg
Nacelle mass – 240,000 kg
Tower mass – 347,460 kg
Total steel mass – 700 ton

We are going to assume that the windturbine of the future is going to be produced with renewable electricity, where the steel will be made in an electric arc furnace:

That wikipedia article claims that the energy cost for one metric ton of steel is 440 kwh. Applying this to the data of the standard wind turbine mentioned above, we arrive at 440 * 700 kWh = 300 MWh. This is the equivalent to the power production of the same 5 MW standard wind turbine of 12 days full power.

Assume the requirement of 1000 ton of reinforced concrete for the foundation (obviously for onshore situation). From this source we learn that the energy cost 1 ton of reinforced concrete is 2.5 GJ. This comes down to ca. 6 days of windturbine operation at maximum power. That makes 18 days in total. Assume a more realistic load factor of 33%, we arrive at ca. 60 days of normal operation for the wind turbine to earn back the invested energy, after which the net energy harvesting starts. The tower will last centuries, blades and gearbox maybe 30 years. And again, the steel can be produced efficiently with electricity, no fossil fuel necessary. This calculation does not include gearbox and generator. Without these items, for a 30 years = 10,000 days, we arrive at an EROEI of 10k/60 = 160. Again, energy cost of gearbox and turbine are not included, as is road construction, transport and assembly. On the other hand the steel tower, representing half of the total steel mass of the turbine, is certainly not written off after 30 years (Eiffel tower was built in 1889 and is around already for 123 years, with no end in sight). It seems that the EROEI value of 20, mentioned in the 2006 theoildrum article (see below), maybe applies to smaller windturbines, but probably is too pessimistic for large offshore windturbines.

Wind energy: go for it.

[wikipedia] – Energy returned on energy invested
[] – Energy from Wind: A Discussion of the EROI Research (2006)



Relationship between EROEI and Civilization

According to Charles Hall the following relationsship exists between the cost of energy (EROEI at the wellhead) and the level of your civilization:

1.1 – pump the oil out of the ground and look at it.
1.2 – you could also refine and look at it.
1.3 – also distribute it to where you want and look at it.
3.0 – build and maintain the truck and the roads and bridges required to use it
5.0 – grow grain and put it in the truck and deliver it.
8.0 – to support farmers and truck drivers and their families.
9.0 – if your want to give your children an education
12.0 – if you want health care
14.0 – if you want arts in your life
No moonlanding included so far.


Related material:
Lots of EROEI studies here.

EROEI Estimates For Shale Oil

Results of a quick search on the web:

Wikipedia – Oil Shale – Study from 1984 indicates EROEI values between 3-10.

Executive summary refers to study by Adam Brandt, giving EROEI values like 2.5 for shale oil.

– European Commission quotes study that rejects oil from shale as not viable, based on low values of EROI. [source]

– APPENDIX D TAR SANDS/OIL SANDS – M.C. Herweyer, A. Gupta [source]
“Reported EROIs (energy return on investments) are generally in the range of 1.5-4, with a few extreme values between 7-13.”

Shale Considerations

We are no friends of shale gas/oil as it has the potential to poison the lands exploitation is practised on. But that does not garantee it is not going to happen. Here is why. But first we consider what a barrel of oil factually represents. Imagine you have a hometrainer with metal grips and a display as shown in the picture. You click your iPad in a holder so you can watch a number of youtube videos you have collected during the past few days and off you go. You have configured the apparatus such that the effort is high, but not that high that you can’t concentrate on the videos. The room where the hometrainer is located is not heated, which means that the temperature in the winter is ca. 10 degrees Celcius. After five minutes the display says pulse = 100 and generated power = 100 Watt. By that time you pull off your shirt as you have generated enough internal heat to no longer feel discomfort from the 10 degrees Celcius room temperature. After an hour you are finished, a little tired, but not exhausted. You produced 100 Watt * 1 hour = 0.1 kWh. Market value in the US: 1 dollar cent (double that in Europe). In order to produce 1 kWh it would require you to sit on the thing for 10 hours, that’s much more labour than any western trade union would allow to happen. Market value of the electricity fruits of your labour: 10 dollar cent for a hard days work. How many kWh are contained in a barrel of oil? Answer: 1628.2 kWh. A year has 240 workdays. We just figured out that a man can produce slightly less than a kWh per day. This means that one barrel of oil contains the amount of energy the equivalent of which would require you to be glued to your hometrainer for a whopping eight years. Market price one barrel of oil ca. 100$.

Back to shale. If a team of say 20 drillers is able to produce 500 barrel a day, then they convert 20 man days of physical labour into 4000 man year of physical labour equivalent, that is a (redefined) EROEI of zillion. Take into consideration additional labour to produce the drilling equipment, the drivers of trucks carrying all that water and fracking fluids and allow for a factor of three (we are guessing here) and we still have a (newly defined) EROEI of zillion. In the end all costs are labour costs as mother nature does not charge for resources, at least not in dollars. That is the proper way of looking at it and not the volatile financial side of it, which to a large extent consists of high labour costs. If you consider that an average Ukrainian makes 500 dollar a month and an American oil worker maybe 5000$ a month… and both survive… and that Americans are not ten times as good/productive/efficient as Ukrainians, then it is not difficult to guess that after a great default American oil workers could also make 500$ a month (in present day value) and that from that moment on the price of shale oil could come down considerably with collapsing wages. Moral: the question whether shale oil will be exploited or not is determined by EROEI in terms of human physical labour equivalent and not volatile finance. The only hope that remains for fracking not to be applied on a grand scale is that the cost of solar and wind will be lower than that of fracking, otherwise we are ummm… fracked.

P.S. these considerations only apply if one can ‘harvest’ more energy than it takes to produce the harvest. In fact the energy costs for the production of shale oil are relatively high. Wikipedia cites a study from 1984 estimating EROEI values for shale oil 3-10. A more recent study by Adam Brandt even gives a figure of 2.5. We don’t know where the EROEI tipping point is, below which nobody will bother to extract the shale oil from the ground… 2? 3? 5? But considering the enormous energy content of a single barrel of oil, that EROEI value will not be very high. By that time you will certainly not be driving 50 miles to a house party. The scarce amounts of oil will be used for more pressing tasks like ploughing and harvesting.

EROI Threshold / Net Energy Cliff

Article that discusses the EROI (EROEI) threshold idea. According to Charles Hall our current society would probably not be able to function if the EROI for the entire society slipped below five. The graph is produced as follows: A society needs to invest energy in order to ‘harvest’ energy:
Net Energy = Eout – Ein
Definition of EROI: EROI = Eout/Ein
Substitution leads to: Net Energy = Eout*((EROI-1)/EROI) (see graph).
The net energy cliff figure relates the percent of energy delivered as net energy (y-axis, green) and the percentage of energy used to produce energy (y-axis, brown) as a function of EROI (x-axis). EROI is a confusing concept. There is hardly a difference between EROI 100 (oil from Saudi-Arabia in the sixties) and EROI 10 (solar panel). Here some examples:

EROI 100 means that if you put 1 potato in the ground you can harvest 100 next season. EROI 10 means that you must put 10 potatoes in the ground to harvest 100 next season.

To put it differently: if your starting capital is 100 potatoes and EROI is 10, then you need to plant 10 potatoes and you can eat 90 in order to harvest 100 again and the cycle can start all over again in a sustainable way. In case of EROI 100 you only have to plant 1 potato and you can eat 99 to have 100 potatoes again in the next season. Comparing EROI 10 and 100 means incomes resp. of 90 and 99 potatoes, a difference of only 10% and not a factor of 10! EROI applied to energy same story. In case of EROI ratio 15:5 the income difference is 14:12 or ca. 16%. Not that spectacular either.


Meet Mr EROI, Charles A.S. Hall

Youtube text: Professor Charles A. S. Hall speaks of his concept “Energy Return on Investment” (EROI) at a seminar arranged by think tank Global Challenge in Stockholm. Posted November 2012.

[] – Charles A. S. Hall & Kent A. Klitgaard, Energy and the Wealth of Nations: Understanding the Biophysical Economy (Oct 2011, $79.88)

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A child will understand that if you have a garden with potatoes planted in it and if you harvest these potatoes at the end of the season, that there are two applications possible for the potatoes: consumption and seed for the next harvest. With energy it is much the same. Before you have a windturbine installed, able to produce electricity for decades to come (consumption potatoes), you first have to invest a lot of energy to get the machine installed in the first place (the seed potatoes). And a child will also understand that it would not make sense to install the windturbine if it takes more energy to install it than it will ever generate during its productive lifetime. Fortunately it doesn’t. Some estimates state that a windturbine can generate 18 times the amount of energy necessary to produce the windturbine. That number is called EROEI (or EROI), Energy Return On Energy Invested. The graph shows the EROEI values for all sorts of energy sources. For a table with the same values, see below.


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EROI for U.S. Oil and Gas Discovery and Production

In October 2011, researchers from State University of New York and Boston University issued a report: “A New Long Term Assessment of Energy Return on Investment (EROI) for U.S. Oil and Gas Discovery and Production”. From the abstract:

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