NREL Establishes World Record for Solar Hydrogen Production

[OKIsItJustMe]

(Please note, material from U.S. Department of Energy's (DOE) National Renewable Energy Laboratory (NREL) — Copyright concerns are nil.)

http://www.nrel.gov/news/press/2017/41792

[font face=Serif][font size=5]NREL Establishes World Record for Solar Hydrogen Production[/font]

April 12, 2017

[font size=3]Scientists at the U.S. Department of Energy's (DOE) National Renewable Energy Laboratory (NREL) recaptured the record for highest efficiency in solar hydrogen production via a photoelectrochemical (PEC) water-splitting process.

The new solar-to-hydrogen (STH) efficiency record is 16.2 percent, topping a reported14 percent efficiency in 2015 by an international team made up of researchers from Helmholtz-Zentrum Berlin, TU Ilmenau, Fraunhofer ISE and the California Institute of Technology. A paper in Nature Energy titled Direct Solar-to-hydrogen Conversion via Inverted Metamorphic Multijunction Semiconductor Architectures outlines how NREL's new record was achieved. The authors are James Young, Myles Steiner, Ryan France, John Turner, and Todd Deutsch, all from NREL, and Henning Döscher of Philipps-Universität Marburg in Germany. Döscher has an affiliation with NREL.

The record-setting PEC cell represents a significant change from the concept device Turner developed at NREL in the 1990s.

Both the old and new PEC processes employ stacks of light-absorbing tandem semiconductors that are immersed in an acid/water solution (electrolyte) where the water-splitting reaction occurs to form hydrogen and oxygen gases. But unlike the original device made of gallium indium phosphide (GaInP₂ ) grown on top of gallium arsenide (GaAs), the new PEC cell is grown upside-down, from top to bottom, resulting in a so-called inverted metamorphic multijunction (IMM) device.

This IMM advancement allowed the NREL researchers to substitute indium gallium arsenide (InGaAs) for the conventional GaAs layers, improving the device efficiency considerably. A second key distinguishing feature of the new advancement was depositing a very thin aluminum indium phosphide (AlInP) "window layer" on top of the device, followed by a second thin layer of GaInP₂. These extra layers served both to eliminate defects at the surface that otherwise reduce efficiency and to partially protect the critical underlying layers from the corrosive electrolyte solution that degrades the semiconductor material and limits the lifespan of the PEC cell.

Turner's initial breakthrough created an interesting new way to efficiently split water using sunlight as the only energy input to make renewable hydrogen. Other methods that use sunlight entail additional loss-generating steps. For example: Electricity generated by commercial solar cells can be sent through power conversion systems to an electrolyzer to decompose water into hydrogen and oxygen at an approximate STH efficiency of 12 percent. Turner's direct method set a long-unmatched STH efficiency record of 12.4 percent, which has been surpassed by NREL's new PEC cell.

Before the PEC technology can be commercially viable, the cost of hydrogen production needs to come down to meet DOE's target of less than $2 per kilogram of hydrogen. Continued improvements in cell efficiency and lifetime are needed to meet this target. Further enhanced efficiency would increase the hydrogen production rate per unit area, which decreases hydrogen cost by reducing balance-of-system expenditures. In conjunction with efficiency improvements, durability of the current cell configuration needs to be significantly extended beyond its several hours of operational life to dramatically bring down costs. NREL researchers are actively pursuing methods of increasing the lifespan of the PEC device in addition to further efficiency gains.

While an alternative configuration where the device isn't submerged in acidic electrolyte and instead is wired to an external electrolyzer would solve the durability challenge, a techno-economic analysis commissioned by DOE has shown that submerged devices have the potential to produce hydrogen at a lower cost.

The latest research was funded by the Energy Department's Fuel Cell Technologies Office in the Office of Energy Efficiency and Renewable Energy.

NREL is the U.S. Department of Energy's primary national laboratory for renewable energy and energy efficiency research and development. NREL is operated for the Energy Department by The Alliance for Sustainable Energy, LLC.

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Visit NREL online at www.nrel.gov[/font][/font]

[longship]

1. That's a good gain.

There are better energy storage methods, though.

Probably the best is good old potential gravitational energy, pumping water uphill and letting it go through a turbine when it goes back downhill. Efficiency ~80%.

Hydrogen generation doesn't come close. But for uses that require a portable fuel (e.g., aircraft) hydrogen may be the fuel of choice in spite of its inefficiency.

The best energy policy includes all of the above.

R&K

[OKIsItJustMe]

2. Pumped hydro storage

There are several problems with pumped hydro. Perhaps the most obvious is that it requires a lot of water, oh, and suitable geography.

Let’s put things into perspective here.

Here’s the world’s largest facility:
https://thinkprogress.org/the-inside-story-of-the-worlds-biggest-battery-and-the-future-of-renewable-energy-8984e81283c

[font face=Serif][font size=3]…

The whole system is laid out over two reservoirs. The upper reservoir is smaller, fed by Little Back Creek and a 4 square mile watershed. This reservoir is an artificial lake created out of a valley, filled in by a dam made of an impervious core of 18 million cubic yards of clay and stone.

Over 1,000 feet downhill from this reservoir is a larger lake, fed by Back Creek and a larger 75 square mile watershed. The water flows out of this system into the Jackson River, then the James River, and then out to the mouth of the Chesapeake.

…

The facility has 3,030 megawatts of capacity (3.03 gigawatts), meaning that when the upper reservoir is full and all 6 turbines are spinning, it can produce that much power to the grid. The average generation is 2,772 megawatts — as water exits the Upper Reservoir, the pressure of water (the head, or weight of water) turning the turbines decreases, meaning that the facility starts to produce less power when there is less water.

…

Fridley explained that “We have the capability of storing 24,000 megawatt-hours up on the mountain on any given day. And if we have drought conditions that eat into that, we’re just reduced on power output. It’s as simple as that, it’s simple physics. The plan is to just let it dig into the power. Because there’s really nothing else you can do. If there’s no water, you can’t make electricity… We have not got to that point yet, but we’ve had some close calls.”

…[/font][/font]

This is not a long-term energy storage solution. It’s used to shift power generation to meet demand. It takes several square miles, and is vulnerable to drought.

[Alex4Martinez]

3. How about advanced rail energy storage?

Better than hydro, I'm thinking.

http://www.aresnorthamerica.com/

[longship]

6. I am for all of the above.

But hydrogen is one of the least efficient. It would be good for uses in which one needs to burn fuel. Hydrogen powered aircraft anybody? (admittedly speculative)

I'll click through your link as I've not heard of advanced rail storage.

On edit: interesting. Has some of the same drawbacks as pumped hydro, though. Mainly, dependent on topology.

Thanks!

[longship]

5. Yup! There are those issues.

I was addressing just the efficiency.

And generating hydrogen is notoriously inefficient.

[OKIsItJustMe]

7. We need a way to store energy long term

Nature does it rather well using chemistry. Well, to be more specific, in the case of plants, first, she splits water, then, she combines the hydrogen with other elements to produce things like sugars…

She’s been quite successful at this for a long time…

[Alex4Martinez]

4. Skeptical of hydrogen but happy for any and all research.

Hydrogen as a commodity is the kind of thing that the industry LOVES.

I prefer electricity for my vehicles, I can charge at home or work and know that my efficiency from source to wheels is higher than any hydrogen technology to date.

[NNadir]

8. It's, um, bullshit of the usual kind. Solar thermal plants on an industrial scale are...

Last edited Thu Apr 20, 2017, 04:55 AM - Edit history (2)

...grotesque failures.

This kind of efficiency hype announced as a "record" will do exactly what the entire failed expensive and useless solar industry always does, generate more complacency than energy.

The solar industry after 50 years of mindless and frankly destructive cheering can't even produce 1% of the world's primary energy.

Now you're going to make hydrogen from it, and you're screaming for joy at 16.2% efficiency?

In order to produce in the form of hydrogen the world's energy supply, which is 570 exajoules per year, the solar thermal industry would need to produce 3518 exajoules as primary energy.

The piece of garbage solar thermal plant trashing the Mohave desert right now, the Ivanpah tragedy covers 3,500 acres and doesn't produce as much energy as a small garbage incinerator.

It produced just 0.0639 exajoules of energy in three years, or 0.0213 exajoules per year.

It's in a desert.

In order to produce 3500 exajoules, we would need about 1.6 million similar plants, all of them in deserts, and all of them paradoxically near water to split. They would need to occupy 23 million km², which is very close to the entire surface area of North America.

How ridiculously stupid!

These reports, which amount to nothing more than big lies, are useless. They present failure as a victory.