Volt ohne Raum

Organic lettuce in Brandenburg

Here a quick rather handwavy calculation on different area needs for energy production.
This time energy production from humans is compared with photovoltaic electric energy production. There is a tl;dr at the end of the calculation.

Assume Germany would be in a Tropical climate. i.e. the temperature is at least room temperature, so no need for heating and assume thus that the main demands of a human were just food, i.e no car, no cell phone etc.
To make things easy, let’s take the data from this survey from Agree.aua.gr
There the utilized agricultural area for Germany is given in 2007 (p. 13 Table 4) as
$latex 1693*10^8m^2$, so if the agricultural land need for a person would be $latex 1693 m^2$ then 100 Million people could be fed.
Since 2007 the agricultural land in Germany declined and according to world bank there were in 2012 only about $latex 1400 m^2$ agricultural land per person available and Germany has currently roughly only 80 million inhabitants but it’s sort of the same order of magnitude, so let’s take the 2007 numbers. Let’s assume a human is superefficient, i.e. all of the consumed energy via food intake could be reused, just as electric power may be reused.
yes….this is a bit unrealistic but…
Let’s further assume a human needs about $latex 1500$ kcal which is $latex 1.743$ KWh per day, i.e in a year $latex 1.743 * 365$ kWh $latex = 636.195$ kWh. So 100 million people need $latex 63619$ million KWh. According to table 3 (p.12) the energy need (machines etc.) for agriculture itself is $latex 42* 10^{15}J$ which is about 11.6 million KWh. This is not much against the $latex 63619$ million KWh, but let’s add it to conclude that the energy need via food intake for 100 million people is roughly $latex 63630$ million Kwh. Or by our 100% efficiency assumption the (food production) land need for producing $latex 63630$ million Kwh human energy is $latex 1693*10^8m^2.$

Let’s compare this with photovoltaic energy. Also if we have assumed tropical temperatures lets assume that the sun still shines dimly as in Germany so let’s take as an average 1500 sunhours per year. A typical solar 120-130 W solar panel is around $latex 0.8 m^2.$ So in an hour 1kWh needs thus more than $latex 100/130*0.8 m^2\simeq 6m^2$. Let’s take $latex 7 m^2.$ So in $latex 1500$ sun hours $latex 7 m^2$ produce around $latex 1500 kWh$ energy.

Hence the land need for producing a solar energy of $latex 63630$ million Kwh is only $latex 63630 \; million\; KWh/1500 KWh *7 m^2 = 3*10^8m^2$.

Photovoltaic energy production has the big disadvantage that the possibilities for energy storage are still rather bad -but still- the different land need is roughly a factor 560.
Where it has to be said that photovoltaic electric energy production is considered already very area consuming.

tl;dr :
If 100 million humans would rather hyperefficiently convert all food energy in a year into “available energy” , i.e. roughly “produce” $latex 63630$ million Kwh then the land need for this is roughly $latex 1693*10^8m^2.$
The land need of typical photovoltaic solar cells for this energy in a year is roughly a factor 560 smaller, i.e. $latex 3*10^8m^2$.

This calculation is only a very rough estimation, no guarantee for calculation mistakes. I didn’t check thrice, as I would usually do e.g. for an article. So error correction welcome.

supplement 25.10.15: I was actually hesitating wether the energy for the agricultural production should be added, as it is not going to be converted, even not with 100% human conversion efficiency. In principle one would need to compare these agricultural
machine investments with a human labour equivalent (which then would need to be deduced from the converted available human energy – here the 100% efficiency assumption would though beat any machine :)). Similarily I left out any invested energy for food processing (cooking etc.)…it is clear that here it gets even more difficult to let the factor not become bigger, finally it is not so easy for humans to heat up to 100 degrees Celsius.

8 Responses to “Volt ohne Raum”

  1. SilliKant Walley Says:

    Sorry but the assumption of 100% efficiency for a human is quite a bullshit.
    As an example: a muscle has a conversion efficiency of 14-27% while an electric motor has up to 99% conversion efficiency!

    It may sound cruel, but thats how it is: a robotic lawn mower powered by solar is much cleaner that a human. It’s also cheaper by the way.

  2. Rafik Srivanatyam Says:

    It may sound cruel, but thats how it is: a robotic lawn mower powered by solar is much cleaner that a human.

    I agree -humans are probably the greatest danger for the environment.

    I hope they take birth rates into account at the 2015 United Nations Climate Change Conference.

  3. emergy consultant Says:

    Since you seem to be exploring toy economies in conjucntion with systems theory concepts like emergy – could you please comment on the project Solar Share?

    The artistic research project Solar Share envisions the radical consequences of an economic model reconnected to the elementary sources of energy coming from the Sun, the Earth and the cosmos.

    The project is part of the POST GROWTH. Ideas and toolkit for a world in crisis and We-make-money-not-art provided a concise wrap-up.

    How is your “toy economy” project going? Yes I know you wrote that: “It is also still not clear wether this project will ever be finished and if in which form.” – but is there any progress?

  4. jubilee line Says:

    This idea by Baruch Gottlieb is brilliant – people need to get more feedback of what it means to burn fossil fuels. Especially the young seem to have completely lost any understanding of economical costs – and here I mean not only of the costs of burning fossils, but apparently also e.g. the costs of Corona if one watches those 600 guys attending Fetisch party in Berlin (video of party closure in german). Can you believe it ? 600 young people jammed into a considerably small space, back-to-back watching naked dances on stage, chanting and yelling loudly and that briefly before next Lockdown!

    The works of Howard Odum and this solar share coin are the right way to go. We have to keep rational in these not so easy times.

  5. nad Says:

    could you please comment on the project Solar Share?

    The solar share project is an art project at IMAL, which is “an art center for digital cultures and technology”. Art doesn’t need to connect too much to realities or constrain itself to realizations. So I think this “solar share project” was rather thought as an invitation to mentally engage people by pointing out challenging problems than as a real proposal for a new currency. And thus the question “How might our understanding of economics change if the instruments we used for money had an equivalent value to the solar energy required to materially produce them?” can be simply “answered” or “experienced” by putting a “price tag” on not so easily degrading things (like a table) which displays the result of a computation of the “solar energy required to materially produce them” and use those things as a currency. And it’s clear why I wrote “not so easily degrading” because of course you don’t want to enter trade negotiations with a squishy banana. :)

    The last remark however makes it already suggestive that the whole lifecycle of a product has to be taken into account – not only production, but also maintenance and disposal. And this makes it also clear that accounting itself is difficult and pricey. Which -like the computation here in this post- displays in a lucid way that it furthermore seems not enough to discern our nowadays currencies with respect to physical realities like energy and life expectancies but also with respect to the “brain work” which enters them. Where “brain work” should probably be discerned w.r.t. into “rational” and “psychological” intelligence, i.e. a more or less pure computational/physical part and a part which is connecting to human thinking.

    Overall it has though to be stated that “value regulation” via trade with currencies seems to be limited in problem solving efficiency – this can already be seen at the regulatory interference of central banks.
    In contrast to that a too rigid regulation may be problematic too. And this need not necessarily mean regulation via a centrally planned economy but even “smaller projects” like bigger industrial and infrastructure projects may have huge (economic) consequences for the respective regions. So I am not sure whether e.g. the problem of energy distribution and generation can so easily be solved by a “totally spelled out regulation” as it seems to be proposed within the framework of a project by architect Bjarke Ingels. I mean there were some problems with Desertec – but then he probably knows about them.

    How is your “toy economy” project going?…is there any progress?

    I have thought quite a bit about the “discernation of currencies” into useful categories, as indicated above, but I am still distilling and I haven’t written up anything sofar. My recent interest in bio chemistry is a bit founded in the investigation of regulatory mechanisms of the human body and in particular signalling pathways. A not too small function of a currency is signalling.

    Anyways at this point I simply can’t afford to invest much more into that “project” -especially not in terms of time sitting in front of a computer.

  6. emergy consultant Says:

    My recent interest in bio chemistry is a bit founded in the investigation of regulatory mechanisms of the human body and in particular signalling pathways….

    At this place you should have cited the Gaia Hypothesis, i.e. the hypothesis that the earth is a self-regulating living organism.

  7. Joe Says:

    Which -like the computation here in this post- displays in a lucid way that it furthermore seems not enough to discern our nowadays currencies with respect to physical realities like energy and life expectancies but also with respect to the “brain work” which enters them.

    Haha so you want lets say a magenta coin for the “physical realities” and a blue coin for the “brain work” that enters a table? What about the fact that currencies can be exchanged and so macroeconomically the differences average out anyways?

  8. nad Says:


    I currently don’t want to propose anything. I just said that I find it instructive to imagine such scenarios – last but not least for getting a better understanding. Of course currencies were introduced because their “fuzziness” with respect to the respective values made exchange of goods easier. And as said already above- the work of “accounting” is certainly not negligeable and it gets rather leass easy with more currencies. In fact I think that social constructs like marriage were introduced at least in part in order to get rid of the “accounting work”.

    But in view of the worlds environmental and societal problems one should think about whether there is maybe too much fuzziness and reconsider the role of trading in setting values. I should may be mention that I have been thinking about this for quite a while. Like in this preprint I asked in how far scientists should interfere in setting values and here I proposed to simulate newer economic schemes – like different value setting schemes – in multiplayer online games, but I think about this only on and off. In recent times I had actually learned a bit more about currently existing lifecycle and some other economic simulations, but as I said here – I am not sure how much I’ll further contribute to this last but not least because I think a real new scheme requires a rather profound digression into other areas.

    But you are right – a crucial point about currencies is of course how well interchangeable the respective currencies are. And yes- if currencies are easily interchangeable then a difference in currencies seems not so important, like before the Euro was established you could usually pay with Deuschmarks and Schilling in Cafés in Austria and southern Germany – if I remember correctly the deutschmark were multiplied by 7 to get the amount of Schilling.

    As far as I understood a value with respect to a currency is called a “price”. Things and in particular the relation price-value change considerably if a currency is not so easy interchangeable.

    Coming back to the “discernation of currencies” with respect e.g. to brainwork – there exist already currencies for brainwork, like for scientific brainwork, namely e.g. citations. That is scientists “pay” other scientists with citing them in their work, if the respective “brainwork” in the other scientists article was relevant enough for their own work. And this “currency” is somewhat interchangeable into “real money”. That is if your “citation index” is high then you get usually better paid or paid at all. Where it is to note here that trading citations (“I cite you 3 times if you cite me 3 times) is not good because it is a sort of “price-rigging”.

    There seem though to exist no currency where people issue some kind of points if they maybe not used the scientific work directly for their own work, but “consumed” it nonetheless. On the other hand there exist some kind of “point systems” for certain types of behaviour, like for companies for “family-friendliness” or schemes like the Economy for the Common Good (where I haven’t yet understood well enough how the accounting works) or on the individual level, like for being an honoured activist
    (“The medal was awarded in a single class for outstanding improvements in production, in technology or in occupational safety.”) These “brain-and-other-labour-and-behaviour-currencies” are partially interchangeable into real money. In the case of orders the interchange scheme is often rather well-defined.

    In Music you have copyright laws and sometimes you are even not allowed to use someones work if you do not cite and in particular if you do not pay. I guess you lnow that story of the song “memory” and that is sounded “like a million dollars”.

    Concluding: Using a physical quantity as an accounting scheme (as in the art work of Baruch Gottlieb) is of course possible but the interchangeability seems not so easy – last but not least because of scientific laws.

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