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Friday, June 5, 2009

Solar energy conversion… can it hurt the Earth?

Note: before anyone accuses me of being anti-green, let me explain my general motivation and then the specific intent of this post. I don't think there is a more potent problem facing humanity (and all life) than the current man-caused spike in global temperature. If we do not act appropriately and quickly and at unprecedented scale, biology faces near-total destruction. The scale of this problem demands that our solutions be equally large. Large solutions of any kind will have both intended and unintended consequences. We must strip emotion and sentimentality from our assessment and design process. We must dump our pre-conceptions and deal with the physical dynamics as they are (not as we would like them to be).

Global heat delta as solar/wind is converted?
Almost every time solar energy is harnessed by human-built converters (to electricity or work), this energy is transmuted down the thermodynamic ladder faster and more localized than would "naturally" occur.

And its digression towards heat is localized (thermodynamic oxymoron I am aware). At the very least, the global atmospheric energy distribution budget is disturbed. Energy that used to go towards other dynamic dissipative systems (ocean and air currents, the fresh water cycle, etc.) is now siphoned off and downgraded to heat at a faster rate. This is especially true of systems like solar to electricity cells which convert some sunlight that would otherwise have bounced out into space.

Even wind and water current converters (turbines) pull kinetic energy from a large system, and localize (time and location) the thermodynamic degradation in non-natural ways.

In both cases, heat that would have dissipated down stream over a long period of time is removed instantly (much of which is immediately lost to heat in the conversion process) and sent to highly localized dissipative devices (lights, heaters, stoves, computers, washing machines, TVs, and industrial equipment). The placement of these end of the line dissipative devices is determined by human desire and not the simple thermodynamic least-energy topology represented in natural systems.

As we get better and better at exploiting solar energy to our own energy needs, more and more of the solar energy that drives large scale atmospheric phenomena will be removed from the standard atmospheric causality chain. What impact will this have on weather patterns? On ocean currents? On global temperature and temperature distribution? On annual seasons? On precipitation patterns?

Our planet's heat budget is to some extent regulated by the off-planet radiation of heat through infrared (and other) radiated wavelengths. How do our current human uses of electricity effect this radiated/mechanical heat fraction?

As compared to hydro-carbon oxidation?
To be sure, the oxidation of hydro-carbons (burning oil and gas) has a more radical effect on heat balance. But this has more to do with the fact that undisturbed oil and gas are only "potential" energy until we bring them to the surface and burn them. Solar energy conversion is not typically considered in light of thermodynamic process because it is assumed that this is energy that is used naturally anyway. But natural uses of solar energy drive planet wide dissipative engines upon which all life is distributed and timed.

To what extent will drastic increases in solar energy conversion effect these essential processes? Especially as humans continue to use more and more energy?

Is this a tipping point effected system?
I know that current solar conversion is probably such a small slice of the total earth-solar energy budget that these questions must seem daft. However, as we have seen in many natural systems, small changes can catalyze huge and unexpected out-fall effects. Disregarding "tipping point" sensitivity, how will ever increasing capture of solar energy for human use effect Earth-scale dissipative systems that support biology as it is currently represented?

Engineering done well
Here is what I suspect. We put solar conversion panels up where solar real-estate is cheap... on roofs or in deserts where other (agricultural) uses of that energy is not reasonable. These locations are locations where there is reason to have highly reflective surfaces. A well designed solar converter reflects as little energy as possible. Either way, I suspect that solar panels have different reflective behavior than other surfaces. Plants appear green because they absorb red (longer wavelength) light. Plants differentially reflect green and blue light. Solar panels are usually placed where plants aren't. But even if they replaced plants, their reflection/absorption properties would be different than plants. A plant converts solar to chemical energy in a respiratory process that absorbs carbon from carbon dioxide in the air and strips the carbon releasing pure oxygen.

Photovoltaic panels are not respiratory systems. This fact alone changes the environmental atmospheric equation.

But let us instead concentrate on panels that replace only other non-biological surfaces of various reflective and heat storage indices. The whole point of a well designed solar panel is to convert solar photonic energy to heat or electricity (or hydrogen) which can be transported or transmitted to other locations for immediate use (conversion back to heat through a chemical or mechanical process that results in work). This process differs from natural processes in important ways. It is usually faster degradation to heat. It is often localized differently than natural dissipative processes. And (if well designed and engineered) it is more absorptive than natural surfaces. 


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