Process to Produce Hydrogen from Water Using Sunlight Reaches 16.2% Efficiency, on Its Way to Meeting DOE Target

til you understand what they are doing. They didn't take a solar cell and connect it to a glass of water.

Why didn't they just connect a solar cell to a glass of water? What's so revolutionary about inserting a solar cell into water? Someone else here was talking about the difficulty of using solar cells, batteries, convertin g it to AC, then using it to separate hydrogen and oxygen from water. What batteries? What AC conversion? You just use the DC solar array outpu t. And I don't see the big deal with doing it that way, as opposed to sticking a solar cell into a tank of water. In fact, it sounds more durable and mor e practical to use a regular solar cell array, instead of submerged ones. The problems with either are the efficiencies and economics and then it wou ld be limited to stationary applications, unless we can solve the other proble ms of storing hydrogen in vehicles, etc.

Good grief. His point is that with black asphalt, it gets hot because it's absorbing the heat of the sun. With a white surface, it doesn't get as hot because less heat is absorbed, more is reflected back. If a white similar object isn't as hot. A white roof doesn't get as hot as a black one for the same reason. Where does that energy from the sun go, if not reflected back into the atmosphere and ultimately, some of it going back out to space? Even the global warming folks are lamenting what will happen as white ice is replaced by dirt or water.

On Tuesday, February 26, 2019 at 2:34:06 PM UTC-6, snipped-for-privacy@optonline.net wro te:

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Wow! That's a lot of opinion based on a very little information. What do you really know about what they did?

Electrolysis is not 100% efficient, in fact that is one of the problems wit h using electrolysis to generate hydrogen. The inefficiency cascades with the other inefficiencies in the system resulting in a system efficiency bel ow the 16% claimed. So I'm thinking 16% efficiency from sunlight to hydrog en is a pretty good number.

Rick C.

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Actually, it's not as simple as you describe for the reason pointed out by Larkin. While visible light is absorbed and radiated according to the colo r that we see, the infrared is not visible to us and is the wavelength emit ted by thermal energy. So the total absorption and radiation of energy is rather more complex than - black hot, white cool, especially when the night time impact of radiation is considered.

I don't expect Larkin to actually give any critical thought to this. He is really only good at things he has done many, many times before. When he i s given a problem that involves new paths of thought, in particular when th ere is a political impact to the result, he fails to analyze any further th an needed to get the result he wants.

Are you doing the same thing?

Rick C.

Quite amazing that anyone would argue this simple physics that we all experience. A black object placed in the sun gets hotter than a similar black object. White roofs are recognized as absorbing less heat than a black shingle roof. I've even seen the global warming folks talking about how melting ice, which changes areas from white to dirt or water will result in more heat being absorbed.

If you plot the sun's intensity versus frequency it peaks around

OK, I didn't want to start your Stevenson box thing... but we agree no one paints them with black paint... Well maybe vandal 'Greenies'.

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You're the one claiming it's some big breakthrough, not me. What do you really know?

ith using electrolysis to generate hydrogen. The inefficiency cascades wit h the other inefficiencies in the system resulting in a system efficiency b elow the 16% claimed. So I'm thinking 16% efficiency from sunlight to hydr ogen is a pretty good number.

I know electrolysis of water is about 75% efficient, how about that? Take a solar cell that's 25% efficient and you have ~16% overall efficiency . So, what's so great about that thing again? Besides the cute bubbles from a cell under water?

On Tuesday, February 26, 2019 at 3:01:10 PM UTC-6, snipped-for-privacy@optonline.net wro te:

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I don't get it. You acknowledge you know nothing about what they are doing and yet you are here making a lot of noise. I can't take you seriously.

with using electrolysis to generate hydrogen. The inefficiency cascades w ith the other inefficiencies in the system resulting in a system efficiency below the 16% claimed. So I'm thinking 16% efficiency from sunlight to hy drogen is a pretty good number.

cy.

Except that 25% efficient solar cells are very expensive. Also, there are other losses in the system. Even though both the solar cells and the elect rolysis are DC they aren't the same voltage, so a DC-DC converter will be n eeded with some losses.

You seem to be operating under the idea that this is a product ready to sel l. It is a new idea that is being explored. Even if the efficiency is mer ely as good as can be obtained by other means, this process is in early sta ges and may end up being a much better method.

No one is talking about a "big breakthrough" other than you. It is a repor t of interesting research that is already as efficient as other methods.

So what exactly is your problem?

Rick C.

Eh? How do I re-paint the roofs of a town?

As for the 'black things get hotter' point, that's the third time you've made the same mistake I pointed out: white objects don't radiate away heat (which is the dominant effect on the dark side of the planet). Every time is NOT daytime. The effect you keep trying to ignore is equal to, and opposite, the one you acknowledge. Not only is this error in the last decimal point, it's in the first binary point.

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ng and yet you are here making a lot of noise. I can't take you seriously.

I know I can get about the same efficiency with a solar cell and two electr odes in water. Maybe you should ask the OP, who claimed this news was a big deal to explain why it's a big deal?

ms with using electrolysis to generate hydrogen. The inefficiency cascades with the other inefficiencies in the system resulting in a system efficien cy below the 16% claimed. So I'm thinking 16% efficiency from sunlight to hydrogen is a pretty good number.

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e other losses in the system. Even though both the solar cells and the ele ctrolysis are DC they aren't the same voltage, so a DC-DC converter will be needed with some losses.

Yawn... How expensive will this be? And how about this. I can get an electrolysis unit, 250KW, the size of a couple refrigerators. I can connect that to a solar array that collects the energy. How big is a 250KW solar array? Big, it's about 425 sq meters. Now imagine something that size full of water and plumbing too, collecting the gas. Doesn't sound very practical or cost effective compared to the existing approach. So, you tell us why the new way is such a breakthrough.

ell. It is a new idea that is being explored. Even if the efficiency is m erely as good as can be obtained by other means, this process is in early s tages and may end up being a much better method.

I'm under no such illusion. I'm just waiting for someone to explain what is so wonderful, what the advantage is, to filling a huge solar array with water and doing it this way, as opposed to what works today.

I suggest you read the original post. It starts off with "this is major".

It is a report of interesting research that is already as efficient as othe r methods.

No problems here, maybe you have one with facts?

Not so. On a planet with nearly-steady temperature, radiant heating from the sun (about 1/100 radian wide, so (pi/4) * 1E-4 steradians, at solar temperature), is balanced by (equal to) radiant cooling by the Earth's surface into cold space ( so, 4 * pi steradians, at terrestrial ambient 'temperate climate' temperatures).

Changing the albedo multiplies BOTH these contributions by the same number, so it doesn't chage the balance. The greenhouse effect requires more than a change in albedo, you have to do it in a spectrally-separate way, or have a color-change due to variable atmospheric penetration.

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Actually it is a simple as I described. I was replying to the incorrect physics, where the other poster claimed that a black surface doesn't get hotter from the sun than a similar white surface. A parking lot was the example. A black surface will absorb more heat, while a white one will reflect some of it and not be as hot. And I correctly cited that global warming folks are lamenting the loss of ice, for that very reason. White snow and ice reflect sunlight, dirt and water absorb it.

While visible light is absorbed and radiated according to the color that w e see, the infrared is not visible to us and is the wavelength emitted by t hermal energy. So the total absorption and radiation of energy is rather m ore complex than - black hot, white cool, especially when the night time im pact of radiation is considered.

is really only good at things he has done many, many times before. When he is given a problem that involves new paths of thought, in particular when there is a political impact to the result, he fails to analyze any further than needed to get the result he wants.

No, I'm just telling you the way it is. Larkin is right about black parkin g lots. You disagree? Take it up with NASA and similar:

-sunlight

NASA satellite instruments have observed a marked increase in the amount of solar radiation absorbed by the Arctic since the year 2000, a trend that a ligns with the steady decrease in Arctic sea ice during the same period.

While sea ice is mostly white and reflects sunlight, ocean water is darker and absorbs more of the Sun?s energy. A decline in Arctic albedo (r eflectivity) has been a key concern among scientists since summer Arctic se a ice cover began shrinking in recent decades. As more solar energy is abso rbed by the ocean, air, and icy land masses, it enhances the ongoing warmin g in the region, which is more pronounced than anywhere else on the planet.

Why is Arctic sea ice important?

Arctic sea ice keeps the polar regions cool and helps moderate global clima te. Sea ice has a bright surface; 80 percent of the sunlight that strikes i t is reflected back into space. As sea ice melts in the summer, it exposes the dark ocean surface. Instead of reflecting 80 percent of the sunlight, t he ocean absorbs 90 percent of the sunlight. The oceans heat up, and Arctic temperatures rise further.

Maybe the problem is with you and not Larkin.

Call a contractor.

White things reflect away the visible light, which is the wavelength where sunlight peaks.

Visible light is "heat" too.

Go feel some cars in the sun.

"White roofs help curb climate change....replacing non-reflective, dark roofing materials with white ones ... (every 1000 square feet) would result in an equivalent CO2 offset of 10 metric tons (about $250) annually"

How many equivalent tons of CO2 does 1000 sqft of solar panel save in a year?

The relative cost must be at least 100:1.

Look at a satellite image. White things *do* send a lot of solar energy back into space. Concrete, ice, clouds all look white from space.

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we see, the infrared is not visible to us and is the wavelength emitted by thermal energy. So the total absorption and radiation of energy is rather more complex than - black hot, white cool, especially when the night time impact of radiation is considered.

e is really only good at things he has done many, many times before. When he is given a problem that involves new paths of thought, in particular whe n there is a political impact to the result, he fails to analyze any furthe r than needed to get the result he wants.

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of solar radiation absorbed by the Arctic since the year 2000, a trend that aligns with the steady decrease in Arctic sea ice during the same period.

r and absorbs more of the Sun?s energy. A decline in Arctic albedo (reflectivity) has been a key concern among scientists since summer Arctic sea ice cover began shrinking in recent decades. As more solar energy is ab sorbed by the ocean, air, and icy land masses, it enhances the ongoing warm ing in the region, which is more pronounced than anywhere else on the plane t.

mate. Sea ice has a bright surface; 80 percent of the sunlight that strikes it is reflected back into space. As sea ice melts in the summer, it expose s the dark ocean surface. Instead of reflecting 80 percent of the sunlight, the ocean absorbs 90 percent of the sunlight. The oceans heat up, and Arct ic temperatures rise further.

You didn't actually address the issues I mention. Please go back to what I wrote. If you want to only discuss the visible light spectrum, then you a re in a different conversation as is Larkin. What others were discussing i s the net effect on temperature, not the instantaneous impact on some theor etical piece of asphalt. You need to consider all effects, not just the on es that Larkin likes.

Yes, there are impacts on climate change when large amounts of ice melt cha nging the albedo. That says nothing about your and Larkin's arguments.

Rick C.

It is good that you finally are concerned about climate change.

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He is really only good at things he has done many, many times before. Whe n he is given a problem that involves new paths of thought, in particular w hen there is a political impact to the result, he fails to analyze any furt her than needed to get the result he wants.

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t of solar radiation absorbed by the Arctic since the year 2000, a trend th at aligns with the steady decrease in Arctic sea ice during the same period .

ker and absorbs more of the Sun?s energy. A decline in Arctic albed o (reflectivity) has been a key concern among scientists since summer Arcti c sea ice cover began shrinking in recent decades. As more solar energy is absorbed by the ocean, air, and icy land masses, it enhances the ongoing wa rming in the region, which is more pronounced than anywhere else on the pla net.

limate. Sea ice has a bright surface; 80 percent of the sunlight that strik es it is reflected back into space. As sea ice melts in the summer, it expo ses the dark ocean surface. Instead of reflecting 80 percent of the sunligh t, the ocean absorbs 90 percent of the sunlight. The oceans heat up, and Ar ctic temperatures rise further.

I have no issue to address everything. Again, I simply pointed out that Larkin is correct, that black surfaces absorb more heat from the sun than white ones do. That a black parking lot is hotter on your feet than a simi lar white surface and it's not because of thermal conduction to your feet from the surface, as the other poster also claimed.

Please go back to what I wrote. If you want to only discuss the visible l ight spectrum, then you are in a different conversation as is Larkin. What others were discussing is the net effect on temperature, not the instantan eous impact on some theoretical piece of asphalt. You need to consider all effects, not just the ones that Larkin likes.

So, you are disputing that a black surface gets hotter in the sun than a white one? Wow.

hanging the albedo. That says nothing about your and Larkin's arguments.

It sure does have impact. Climate folks agree that white snow and ice reflects more sunlight than darker surfaces like dirt and water and that ice lost causes areas with ice to warm more because of it. Exactly what Larkin said, exactly what I said. You disagree, take it up with the climate scientists. I gave you some cites, including NASA.

This PEC cell is more complicated than that. If I read it right, the solar has to be concentrated on the cell with a lens, and the cell is submerged i n water held at 300 psi.

I'd rather paint my roof white. Or actually, spread white gravel.