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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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Fundamentals: Visual intrusion of Windturbines

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      CommentAuthorSteamyTea
    • CommentTimeSep 28th 2013 edited
     
    The trouble with EROEI it is not very good for comparing technologies. OK within a groups, say oil wells in different locations or solar panels on different roofs, but useless for comparing bottled gas with a hydroelectric scheme.
    Just because there is an algorithm does not make it transferable. Rubbish in, Rubbish out.

    May as well compare peoples height to their energy use and then claim that tall people are better.
    •  
      CommentAuthorfostertom
    • CommentTimeSep 28th 2013 edited
     
    Posted By: SteamyTeauseless for comparing bottled gas with a hydroelectric scheme
    I'd have thought EROEI wd be supremely applicable to just that - why not?

    Of course requires wide and honest 'cradle to grave' accounting for all upstream and downstream energy consequences.

    And definition of criteria - how to compare EROEI of nuclear power with EROEI of hunter-gatherer society?
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 28th 2013
     
    You have answered it yourself:
    Posted By: fostertomOf course requires wide and honest 'cradle to grave' accounting for all upstream and downstream energy consequences.
    .
    •  
      CommentAuthorted
    • CommentTimeSep 28th 2013
     
    Looking at EROEI here is just a small part of the whole picture, e.g. what are the different carrying capacities for a nuclear vs h-g societies?
    •  
      CommentAuthorfostertom
    • CommentTimeSep 28th 2013
     
    I like the killer punchline
    Posted By: SteamyTea.
    So as you see it, the unlikeliness of
    Posted By: fostertomwide and honest 'cradle to grave' accounting
    disqualifies EROEI? How convenient.

    Posted By: tedwhat are the different carrying capacities for a nuclear vs h-g societies?
    Expand on that, ted?
    •  
      CommentAuthorted
    • CommentTimeSep 28th 2013
     
    In a h-g society x% of the population are involved in the h and g and so are not available to perform any other functions. This, together with the amount of food supply that can be obtained from just h-g, creates a limit on the total population that an area of land can support.

    In some locations x will approach 100%, due to scarcity of food, meaning that the society carries out no other activities at all, although some of the involvement may be seen as 'cultural' (e.g. youths become men through gaining hunting experience).
    •  
      CommentAuthorfostertom
    • CommentTimeSep 28th 2013
     
    I've been trying to guess what EROEI of a hunter gatherer society might mean. If it's 8, as has been suggested, and if food and wood-fuel are the sources and measure of energy we're talking about here, then it cd mean that 1/8 of the total energy (food and wood) collected is necessary to sustain the collection process, and 7/8 of it is available to sustain leisure and cultural purposes. Not bad! Esp as hunter gatherer societies were (are) very egalitarian, with no leisured aristocracy and no labouring classes.

    Whereas in medieval feudal society, very inefficient at EROEI 4, all the 'spare' was grabbed by the aristocracy while the serfs laboured night and day.
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 28th 2013
     
    One way to look at the energy investment of a hunter-gatherer tribe may be to work out the yearly energy expenditure to survive. So at 2 kWh a day that would be about 700 kWh/(year.person).
    Then work out the amount of land needed to grow enough food stuff.
    Taking the SW (only because I live here and know a bit about it) which has 1200 kWh/m^2 of solar energy every year and say a 0.1% crop conversion (not sure if it make any difference if it passes though a rabbit first or not, probably does as a rabbit is warm, so not an efficiency conversion).
    So about 600m^2 of land is needed.
    As most of the crops are only harvested for 4 months of a year there will be some waste, so let us triple the land needed, so about 1800m^2.
    Not a great deal, but this is only for food.
    Add in some wood fires for heat and cooking, say 4 kWh/day or 1500 kWh/year or another 1200 m^2.

    So it seems as if 1 H-G needs 3000m^2 just to survive. Or 3,600,000 kWh/year of solar energy.

    So energy in is 3,600,000 kWh and energy out is 700 kWh, giving a EROEI of 1.94^-4
    That is 0.000194:1 or in percentages 0.0194%

    It must have been a hard life.

    (if you take migrating animals into account it gets worse as the land area is increased)
    •  
      CommentAuthorfostertom
    • CommentTimeSep 30th 2013
     
    You can't say that all of the incident 3,600,000 kWh/yr is devoted solely to supporting one hunter-gatherer, on his 3000m2. He only 'uses' a tiny part of that, to claim his/her 700kWh/yr - the total incident solar supports a miriad other lifeforms and non-life purposes as well.

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