The idea of technological fixes for climate change (undoing global warming and its undesirable consequences) is as perennially popular as the hunger for diet pills and fat reduction skin creams without side effects, instead of the strictures of a change of diet and an increase of exercise. Like all weight-loss-without-effort pills and creams, proposed technological fixes for climate change, without any change in civilization’s energy diet and exertions for conservation, are (and will be) just as effective. It may well be that the consensus in favor of human stupidity is Nature’s way of saving the planet — from us.
Despite my present belief that commenting on the human comedy is pointless (at least for me), I could not resist saying a bit about some proposed technological fixes to climate change described in a recent article posted on a popular web site for social and political commentary. While I don’t “do physics” anymore, I still find it interesting, especially when it is about natural phenomena. Following is my recent note, which is a gloss on the cited article, by Robert Hunziker.
Hope in technology springs eternal. I enjoy Robert Hunziker’s articles on climate change, which appear in Counter Punch. His current article “Climate Change Meets High Tech,” http://www.counterpunch.org/2014/04/18/climate-change-meets-high-tech/, is really about energy technology research ideas proposed as solutions to the global warming problem, and I want to offer some words of caution about them.
My comments follow on three technologies: a new fuel cell that extracts CO2 from seawater, space-based solar energy beamed to Earth via microwaves, and controlled thermonuclear fusion energy on Earth.
The Naval Research Lab’s proof-of-concept experiment to extract CO2 (carbon dioxide) and H2 (hydrogen) from seawater, and combine these two gases into a liquid hydrocarbon fuel is aimed at a purely military objective and is not a “game changer” to solve our CO2-emissions global warming problem. The NRL research project (and advertisement for more funding) is described at http://www.nrl.navy.mil/media/news-releases/2014/scale-model-wwii-craft-takes-flight-with-fuel-from-the-sea-concept
The NRL apparatus is a new and innovative fuel cell. In general, fuel cells are vaguely like the heating of an old-fashioned liquid-cell battery by an electric hot plate or a natural gas burner. Fuel cells run “forward” to convert input energy/heat into chemical reactions that produce/extract new species from an existing fluid/media; or they run “backwards” beginning with chemical reactions between fed-in species of fluids, to extract energy that is then output in the form of electricity.
One example of a forward mode fuel cell (as I described it above) is a reverse osmosis desalination unit: electrical energy is supplied to extract salt from seawater, and to produce fresh water. Examples of fuel cells operating in the chemistry-to-electricity mode are units that use heat from oxidizing natural gas (oxidized within the specialized membranes of the fuel cells, not burned as open flames) to produce electric power (e.g., for propulsion motors in city buses) with exhaust gases of CO2 and H2O. When hydrogen gas (from a pressurized tank) is oxidized instead of natural gas then the exhaust is pure H2O (steam).
As always, the result (whether output electricity or a chemical change) is of less stored/delivered energy as compared with the energy supplied (whether as electricity, heat or chemical potential energy).
Thus, the NRL apparatus uses energy to extract CO2 and H2 from seawater, and then further combines them into a liquid hydrocarbon fuel, specifically aviation fuel. By the 2nd law of thermodynamics, the chemical potential energy of the aviation fuel produced will be less than the electrical energy supplied to produce the av-gas. Why do this? Because the Navy intends to use this technology on aircraft carriers for the production of aviation fuel directly from seawater, powering the process with the ships’ on-board nuclear reactors. The military objective is to eliminate the cumbersome fuel resupply chains from ports (Navy bases) to aircraft carriers at sea (on long and distant deployments).
There is less reason to use this technology on land. Perhaps, if one wished to produce liquid hydrocarbon fuels from seawater (at coastal installations) with electricity supplied entirely from solar technology, then this would be a less ‘global-warming harmful’ way of producing hydrocarbon fuels than via conventional fossil fuel technology, or the even dirtier synfuels processing of coal. In all cases the energy-return-on-energy-invested (EROEI) will be less than 100%.
Now, for a few words about space-based power generation. Yes, capturing solar energy in space is much more effective: no clouds, and no night with properly sited solar collectors (once lofted into position by rockets and perhaps assembled by astronauts). But, how to get the power back down to Earth? The usual proposal is to send it down as beamed microwave power. Power transmission as laser light is much less efficient (the conversion efficiency of electrical energy to laser light is quite low), and the atmosphere will scatter some of the laser energy. The frequency of microwave transmission can be selected for minimal (but never zero) atmospheric scattering (little interaction between atmospheric molecules and these electromagnetic waves).
To convey reasonable power, the microwave beams would have to be intense since they would be of modest diameter (perhaps meters to 1 km). Otherwise, a wide beam would have to be captured with a large ground antenna; and probably many beams would be needed to power our industrialized civilization. The difficulty with sustained and intense microwave beams from outer space would be that they could cook holes in the atmosphere, and prove harmful to any creatures and organisms, or ships and airplanes, that might inadvertently cross their paths. These problems with microwave-beamed space-based power have been known since the 1970s, when the space-based (microwave-transmitted) power schemes were first proposed. Basically, this scheme is like the operation of unshielded (i.e., open) megawatt to gigawatt microwave ovens aimed down on us. It’s almost like H. G. Wells’ heat ray from “The War Of The Worlds.”
Now, about fusion. I fell in love with controlled terrestrial fusion energy in my boyhood, and went into science and energy research to be a part of the fusion energy future. That future is still in the future, and I suspect it will always be. Actually, we already have civilization-powering fusion energy, it’s called the Sun. It is just that we have yet to fully accommodate ourselves to the efficient uses of it.
Any controlled terrestrial fusion reactor (likely based on hydrogen and/or deuterium, and producing helium) will necessarily generate fusion neutrons and gamma rays in its core. That is the fusion energy that must be captured and converted into usable electricity (and heat). The materials that interact with this hard radiation, both to absorb the energy (like molten/fluid lithium blankets coating the inner walls of the reactor) and to contain the radioactivity (like the layered walls of the reactor vessel and its surrounding containment vessels and shields) will unavoidably become activated, that is to say radioactive. The “first wall” in particular will degrade and need periodic replacement. Hence, there will be a steady production of radioactive waste at any fusion energy electrical generation facility.
The only fusion reactor we know of today that does not produce a radioactive waste disposal problem on Earth is the Sun. Not only does it produce copious amounts of energy by fusion, while keeping the radioactive wastes 93 million miles from us, but it beams its energy to all points on Earth with admirable reliability, magnanimous equity and benign transmission.
Solar power at 1% conversion efficiency on 2% of the land area of the United States of America would produce the total electrical energy use of the nation, 4 trillion kilowatt-hours per year (4T kWh/y).
We have what we need and only lack the vision to realize it.