Charlie Hall's views are intense...long-term, worth checking out.

 Charlie's EnergySweatShop   was a curious thing... seemed silly, yet I could see his points.                       

                                                                                                   => Back to INDEX

What is EROEI?

Energy returned on energy invested (EROEI or EROI) is a concept that mirrors the financial metric, return on investment (ROI). In order to make an energy gain or “profit”, energy or work must be consumed or exerted (Cleveland, C.J., 2001, p.11). The energy gain or profit often referred to as “net energy”. EROEI is usually expressed as a ratio, or occasionally as a percentage. EROEI can also be represented diagrammatically in simplified form (Fig. 1).

Figure 1: EROEI

(Charles Hall, Pradeep Tharakan, John Hallock, Wei Wu and Jae-Young Ko, Advances in Energy Studies Conference, Porto Venere, Italy, September 2002)2

The energy referred to in EROEI can be energy to run technology, such as liquid fuels for transport or electricity for lighting. It can however refer to energy in a form that can be taken in directly by living organisms: food. 

http://europe.theoildrum.com/node/4428

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PK: Problem w/ EROI is, SCALING...

+ it takes into account energy for reinvestment, which is essential.

- However, does not integrate the wider scale of entire social energy picture, including tradeoffs.

There may be beneficial non-energy aspects of an energy source,

      worth the extra energy expenditures.

For example, making efficient electric vehicle batteries is useful for avoiding smog, related to health reasons.

The electric car may not have good EROI, but better overall result than burning a fuel, especially for areas like Mexico City.

EROI would be useful to determine if you are way out on a limb in manufacturing batteries,

might yield good price indications.

You would also want a real clear idea of limiting material factors, 

   such as any rare metals needed in operating a technology, 

   or even usually common materials like water, which may go into short supply.

  For example, if the EROI for a given electric generation technology looks good on paper, 

   yet consumes more water than is readily available,

   that plant will eventually run into problems.

EROI works in shorthand, as most of thhe energy we have in the large quantities we use

is OIL...x %.

The dream of nuclear energy "too cheap to meter" depends on enough liquid fuel to construct the plant, transport 

the nuclear fission materials, and thereupon maintain the whole mess, including disposal.

Note one objection to EROI here, might be the technical problem in getting liquid fuel from Nukes.

...theoretically solvable on a 

small scale by electric vehicles, and

large scale by a Hydrogen Economy.

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LiqFuelSolutions are a potential achilles heel 

    for many a techno-future energy dream.

EROI is a good starting point,

  as it points to the real need for total energy accounting,

real tough question, as we cant see the many intersecting energy intputs

from one industry to another.

  Our society is so blindly dependant on cheap fossil inputs, 

we dont even realize it, are surprised or outraged when cut off.

Blackouts