20th December 2004. This is a draft (daft?) research idea, not yet intended for wide circulation.

Biolectric research

Is this a naff name? A radical idea needs a distinctive and well-chosen name...

Motivation

  1. Energy consumption in the `developed world' is not sustainable. Fossil fuels will soon run out, and there will be an energy crisis. It is essential that
    1. sustainable sources of energy be developed; and
    2. energy consumption be reduced.
    This research proposal concerns sustainable energy sources.
  2. Sustainable power can come from only three sources: from the sun; from tides; or from geothermal sources. Of these sources, the sun is the most promising.
  3. We can tap solar energy either at the primary source, or in secondary or tertiary forms (wind, hydroelectricity, waves, biomass). Because the production of the secondary forms of solar energy is inefficient, it's hard to imagine that human energy needs can be met by wind, hydroelectricity, biomass, and waves alone. (Here are my back-of-envelope calculations.) We must therefore develop solar energy.
  4. How efficient are electron systems in plants and bacteria?
    (Purple bacteria tutorial).
    Efficiency: Standard redox potential of a typical photosystem spans about 800mV. One photon with wavelength 500nm has energy E = hc/l = 3.9 × 10-19 Joules = 2.4eV. So the efficiency of the primary receptor is about 50% per photon.
  5. The most impressive solar electric convertors are the chloroplasts of plants and bacteria. Photon energy is caught in excited electrons, which are transferred efficiently along a chain and used to charge recyclable batteries (also known as NADPH) or to charge capacitors (by transferring protons across a membrane).
  6. Maybe a good way to make efficient solar convertors would be to steal from the best: take working photosynthetic systems and use natural selection to evolve them in the direction we require.

Biolectric research proposal

Create an evolutionary environment in which bacteria are rewarded for interfacing to external electrical hardware. For example, put the bacteria in a pot that contains interdigitating electrodes; provide biochemical building blocks, but deprive the bacteria of energy; thus the bacteria that reproduce will be the ones that cooperate with each other to suck electrical energy from the electrodes.

Add evolutionary pressure to retain photosynthetic ability in the bacteria.

Now if we switch off the electrical power, and keep putting in light, perhaps a little bit of electricity will ooze out. (Hopefully the bacteria will solve the problem of guzzling electricity from our electrodes in a way that uses their existing electron transfer chains.)

Now put in a new feedback loop: measure the feeble electricity output, and direct the biochemical building blocks preferentially to the parts of the pot that are producing the most. (Perhaps use miniature pumps driven by the electricity?)

Survival of the fittest will ensue.

After a few thousand or million generations, we will have bacteria that directly generate DC electricity. Hurrah!

The bad news: This situation will be unstable: bacterium that mutate so as to stop feeding the meter will outgrow their obedient siblings. A solar installation based on these principles will therefore have to remain plugged in to a feedback loop like the one above.


Initial circulation list: Graeme Mitchison, Mike Cates, Robert MacKay, Erik Winfree, Sanjoy Mahajan, Seb Wills.
Credits: Robert suggested the idea of tapping bacteria directly, instead of faffing around with biomass.

How Erik might be involved

Idea: Make self-assembling structures that create the interdigitating electrodes, and the feedback loop machinery -- measuring the electricity output and channeling resources there.