Can Lasers Help Decrease Our Dependence on Fossil Fuels?

[Laser Zone]

Interesting !! http://images.google.com/imgres?imgu...3D640%26um%3D1

[tocket]

Cool idea, although the efficiency if you look at the system as a whole can't be very good. The solar irradiation is about 1 kW/m² and they could only get 24 W out from 1.3 m². That's an efficiency of 1.9%; hardly impressive compared to what normal solar cells do.

There are of course more losses on the way to hydrogen... In particular the chemical reaction to form hydrogen, in which more than 50% of the chemical energy is lost to heat. I suspect the magnesium regeneration won't be very efficient either. They also have to separate the argon and oxygen somehow, which costs energy, reducing overall efficiency.

The system reported in the article probably has a sunlight to hydrogen efficiency of less than 0.1%.

In my opinion it would be far more interesting to generate hydrogen directly from sunlight. Theoretically a single photon with a wavelength of 500 nm contains enough energy to split a water molecule into hydrogen and oxygen. So why use a thousand?

My research group is active in the field of solar hydrogen production and we're making some real progress. Our system doesn't use lasers though...

[The_Doctor]

The single best way lasers will reduce energy consumption is if near UV (405 nm) or actual UV lasers can drive phosphors to make broadband light sources. CFLs (compact fluorescents) will look like bloated poisonous stupid clunky engineering in comparison, and a fire hazard to boot. Standard Cree and Luxeon LEDs have the right idea but their sources aren't resonators. if they were, the efficiencies could start at 25% and keep rising, maybe to exceed 70%. High power IR lasers already exceed 80% according to Sam (Goldwasser) but I'm loosely accounting for losses in phosphors and the fact that near UV lasers aren't that efficient yet. People come up with schemes like HID lamps and others but a resonator is second to none for energy conversion so a laser will be at the core of whatever light source wins. Unless someone invents another kind of resonator.


EDIT:
Regarding sunlight as a source, I learned recently that an old technology normally considered a dirty relic of the industrial revolution is far likelier to be a winner for renewable energy than any 'clean' new wheeze in catching solar energy.

The original idea is something called "water gas". It's a mix of carbon monoxide (which is flammable, and horribly toxic) and hydrogen (which is very obviously flammable but clean). it's made by passing steam over white-hot coke (half burnt coal residue, specifically, near-pure carbon). The output of this is water gas. This is passed over red hot iron which catalyses the CO and remaining steam to form carbon dioxide (non-toxic) and more hydrogen. So far this is the old way, an open cycle that vents to the environment and requires fossil fuels as a carbon source. This can be changed. Algae need CO2, so that can be piped to algae. The algae will yield complex hydrocarbons, so directly or (indirectly via other useful products) carbon is separated from oxygen by photosynthesis, so the CO2 gets used instead of being vented to air, and a renewable source of carbon is maintained by using the natural carbon cycle to do it. Sunlight is the source of heat needed to drive it, at three points, the heating of the carbon and steam, the heating of the iron catalyst, and the photosynthesis in algae. And perhaps plants too. This isn't the stuff of dreams, this is a direct extension of the heavy engineering we're used to, with the exception of algae development to accelerate the carbon cycle. It's not the stuff of small bright lights, this is the stuff that can drive trains and ships and factories and shops and save us from having to agonise over fission and fusion if we really want to avoid that. You don't need to study thermodynamics to know that as the sun is purely used for heating, it is going to be very efficient. And the best way to mitigate entropy is to harness life.

More edit:
Tocket, I think I asked once, but I forgot how you were using solar energy.. Not as I just described, so far as I remember though. What was it? And have you compared it to possible yeilds and efficiencies of a closed carbon cycle solar heated hydrogen-via-water-gas generator?