Unprecedented Efficiency in Photoelectrochemical Production of Hydrogen from Water: 42%

[greenman3610]

This is the holy grail. Not fission, not fusion -
photo-lytic production of hydrogen from sunlight and water.
---------------------------


Michael Grätzel and his colleagues have developed a device that sets a new benchmark for efficiency in splitting water into hydrogen and oxygen using ordinary sunlight. The research will be published in the 13 December issue of the Journal of the American Chemical Society.

Previously, the best water photooxidation technology had an external quantum efficiency of about 37%. The new technology’s efficiency is 42%, which the researchers term “unprecedented.” The efficiency is due to an improved positive electrode and other innovations in the water-splitting device.


http://www.greencarcongress.com/2006/12/researchers_ach.html#more

[wtmusic]

1. Hmm

Photoelectric cells are still more efficient at turning sunlight into usable energy, no? :shrug:

[Nederland]

4. The best solar cells are ~25% efficient

Of course, in that case the end product is electricity, not hydrogen. Given that electricity is probably what you really want anyway, you might have a point there. However, I think the real problem with solar cells is that power to weight / power to area ratios. You need to cover a pretty big area with solar cells to get a decent amount of power...

[Uncle Joe]

7. Just speculating here, but what if you combined aspects of a telescope/microscope with solar panels,

with mirrors focusing the light to a narrow point such as a *laser, would this alleviate the problem of requiring a broader area of solar panels?

*Although it would not have the intensity of a true laser, the light may be more intensely narrowed to a smaller area.

I am not an expert in any of these fields, but this sounds logical to me.

[tridim]

11. That's exactly how parabolic reflectors work

[Uncle Joe]

12. Thanks for the reply tridim,

I am glad someone is working on it from this aspect.:)

[liberaldemocrat7]

28. I can name a fuel you don't have to drill for that you can use for cars.

In fact millions of people produce this potential fuel every day.

How about designing a car that runs on human waste?

ROFL.

[wtmusic]

17. It would help power/weight, but power to area would be unchanged

Whether you're collecting the available light energy with a mirror or solar panels doesn't really matter.

[TheWraith]

23. No, it wouldn't.

You would still need the same amount of area to drain sunlight from--an area about the size of Nevada to power all of the US.

While this development is interesting in principle, the wide distribution of light energy makes it incredibly difficult for any photovoltaic or photoelectrochemical process to yield enough energy to be worth while.

[rman]

29. you'd still need a broad area of mirrors, as is being done:

www.power-technology.com

[conscious evolution]

13. About 60 watts per square meter of collector

60 watts ain't much.
Put the collector in outer space and wattage goes up to 1000 or so per square meter.

[TheWraith]

24. True, but that has its own problems.

For instance, how to transmit that energy back to the Earth without massive loss. Not to mention the fact that we would have to build and launch a photovoltaic/mirror array at least twelve square miles in size to replace the energy output of a single fission plant.

[conscious evolution]

25. It could probably be sent back via microwave

But can you imagine the problems that would pose?Like what would happen if a peice of space junk or something hit the array causing the beam to wobble off target? A person could be driving along and SIZZLE!!!
Though some fundie might think its rapture time!
Without a doubt space based solar is not the answer at this time.

[w4rma]

22. Except for cost, which will come down as manufacturing is innovated, there is no reason

why we shouldn't use every form available of renewable energy creation for every application (including multiple sources for single applications - such as a hydrogen powered hybrid car with solar panels on it's top and trunk and a recharging plug, for when there are no hydrogen gas stations nearby.

[ChairmanAgnostic]

27. but you can STORE hydrogen for nighttime use.

and that means that solar power is a 40% efficient battery - not at all a bad number to work with.

[leveymg]

2. Wow - I remember in '83 when this process was discovered - 2% efficiency

That seemed to present an insurmountable stumbling block, but I insisted that efficiency would improve. Has it ever.

Why are we still drilling for oil?

[WannaJumpMyScooter]

3. Same reason marijuana is illegal...

they don't see a way to make money on it.

[Demeter]

5. The Point Is Producing Hydrogen for Storage of Energy

as fuel for fuel cells. 42% efficiency is still low--but it's better than not having any way to fuel transportation....

Say you take a photocell and stick in the best possible position on the sunniest possible day.

25% of the sunlight is converted to electricity. The electricity is used to split water into hydrogen and oxygen at 42% efficiency.

End result: congratulations! You have successfully stored .42*.25 of the available energy of the sun, or a whopping 10.3% of the total available solar energy.

Doesn't look too good, does it? You'd need a lot of real estate to collect enough energy to fuel one tractor trailor. And I forget what the efficiency of fuel cells is, and I'm too lazy to look it up, but guarranteed it's not 100%.

Even if you can capture all the lost energy as heat for low-energy applications, it would still take a lot of land to convert solar to fuel. Ethanol might be a better bet.

[tridim]

6. What's the efficiency of crude oil -> refining -> combustion -> exhaust?

I bet it's not very high.

[OxQQme]

9. Not to mention

how much land would have to be set aside for the crops. And the water for those crops.
And the fuel for the tractors and trucks needed for planting, tending, and harvesting.
That's a lot of resources to convert solar energy into a fuel to continue on our present
course of consumption.
A search will find many individuals and small companies devoted to electrolizing hydrogen
from water. Electricity is an absolute in the process but it is a very small amount if
you're hydrolizing for personal needs.

http://oupower.com/index.php?dir=_My_Projects/_Over_Unity_Related_Projects/Electrolysis/Electrolysis%20Basics

<snip>
OK so you want to do electrolysis ...no problem! -What's that? Oh ...You want to dive in "Head First" and from the common materials that you just happen to have lying around the house, start producing massive amounts of free hydrogen with which to power your vehicle, house and shop ...hmmm ok. I know of several good doctors in your area that can help with such delusions. -If that is truly your goal in coming here, then you're going to be sorely disappointed. You should probably make better use of your computer time by playing solitaire or something else equally as mind-numbing.

If however, you're here to actually learn something and to understand how you can participate in a wonderful and exciting field of research that has the potential to help the world; then you've come to the right place. Do I believe that Over Unity exists and that we will someday have free energy with which to power our civilization


Or a more little more commercial: http://hytechapps.com/

Amongst many hydrogen links available on the internets....

[Leopolds Ghost]

14. Do these people realize that electrolysis is an energy-consuming process?

[rman]

21. crops?

this is not about biofuel.

[Demeter]

10. I Prefer Wind and Water, Myself

Hydroelectric and windpower are better sources of massive electricity for hydrogen generation or transportation. Solar is more suited for local immediate applications of electricity.

[berni_mccoy]

8. Using Hydrogen as a capacitor... interesting.

Even though it's only 10% efficient, that's 10% of the SUN's radiation energy that reaches earth used to create hydrogen. It's a renewable resource, so efficency only effects production rate of Hydrogen. To go faster, you build a bigger solar array (and the maximum efficiency achievable for any photovaltaic cell is going to be 50% by the way, so we're halfway there at this point: see http://www.lbl.gov/Science-Articles/Archive/MSD-full-spectrum-solar-cell.html).

[Leopolds Ghost]

15. In other words, people are obsessed with finding a way to keep their cars running

Even though the energy from photovoltaic cells could be converted directly into electricity to power cities with,

instead of wasting half of it in order to manufacture fuel for automobiles in order to power a lifestyle that spends 2x as much time in our cars and paves 4x as much of the planet as we did 50 years ago.

[Demeter]

16. The Trick Is to Use Appropriate Technology

Taking the lowest yielding sources for the small loads: solar cells for individual buildings, and use large solar arrays in desert areas unsuitable for agriculture or homes and high yielding hydro and wind towers for industry, including creating fuel for storage and use in transportation.

The electric car is a dream, not a feasible plan for commuting or load hauling. But trams and trains are very doable (ask Europe). High yielding electricity generation can permit efficient hydrogen fuel production.

Use solar heating and good insulation practices instead of oil, natural gas and electricity for space and water heating and free up more high-yield fuels for high energy demand. Add corn- or pellet stoves for backup and atmosphere.

The biggest problem with such changes: utilities will have no customers except the commercial ones who need large amounts of electricity. Just as Single Payer Health Care would remake the face of the insurance industry (mostly by wiping it out), so too would sensible and appropriate energy allocation and generation change the face of the energy and extraction industries. The transportation-related industries would also undergo major transformations.

It isn't a small thing, all this change. But the results would be sustainable, economical, clean, and enable the common people to have increased security in their domestic lives. Profits, especially excessively large ones, would be a lot harder to find, but the cost of living would shrink dramatically.

[Canuckistanian]

18. Yours is about the most sensible plan I've ever heard

I was going to use the word "solution", but realized that the status quo must change in terms of energy spent per task. We are a hopelessy inefficient society as far as energy consumption goes.

But you're right, the future will be a mixed energy scenario.

And a VERY different world from what we live in now.

But that's a good thing.

[Demeter]

26. Thanks for your kind words.

[wtmusic]

30. "The electric car is a dream"?

Have you seen "Who Killed the Electric Car"? The electric car is a dream because the petrochemical industry has relegated it to that.

Electric cars are only feasible for the drivers who drive less than 80 miles/day.

About 90% of them.

[greenman3610]

19. Imagine every Mall parking lot and roof

covered with solar cells.
Floating solar mats at sea, large desert based collectors,
every glass skyscraper with photoelectric glass facade,
millions of sunbelt homes with collectors,
and an electic grid nimble enough to wheel
power from where it is surplus to where it is
needed.

Add this to biofuels production from every
waste and sewage facility in the country, including
municipal waste and cattle feedlots.
Large algae farms fed by waste producing
liquid fuel at dozens or hundreds of times
current efficiencies.

Meanwhile, technologies like LED lighting
allow the maintainance of current levels of
electrical services with vastly reduced amounts of
power.


that's what I'm thinkin.

[rman]

20. this is "Photoelectrochemical" - no need for photocells

from the article:
"Under illumination in 1 M NaOH, water is oxidized...incident photon to current efficiencies = 42% at 370 nm..."

so it's solar > hydrogen
not solar > electric > hydrogen

Although 42% isn't that much higher than 37%, it's still an interesting technology.

[AntiFascist]

31. I believe it has already been demonstrated that....

electrolysis of ocean water using electricity generated by turbines in ocean currents are an infinite source of hydrogen, provided the turbine is maintained and that there will always be ocean currents. I suppose the oil industry doesn't like the competition posed by unending sources of hydrogen.

[buddysmellgood]

32. Why would't we just use the electricity? Would these plants be remote and the Hydrogen

floated in?

[AntiFascist]

33. Much of it could via cables....

but future vehicles are likely to run on some form of hydrogen. Hydrogen also provides a means of storing the energy.