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The layout of the hybrid system  (Source: Nico Hotz)
New system utilizes a water/methanol combination along with catalytic nanoparticles flowing through copper tubes to create hydrogen, which produces electricity through a fuel cell

A Duke University researcher has created a new hybrid system for converting sunlight into electricity, which can be placed in residential rooftops as a form of alternative energy.

Nico Hotz, study leader and assistant professor of mechanical engineering and materials science at Duke University's Pratt School of Engineering, has developed a hybrid system based on traditional solar panels, but instead utilizes sunlight to heat water and methanol in copper tubes on a house/building's rooftop.

This hybrid system consists of a maze of copper tubes coated with aluminum and aluminum oxide, and these tubes are partially filled with catalytic nanoparticles. A combination of water and methanol, which is sealed in a vacuum, flow through the tubes while sunlight is collected.

"This set-up allows 95 percent of the sunlight to be absorbed with very little being lost as heat to the surroundings," said Hotz. "This is crucial because it permits us to achieve temperatures of well over 200 degrees Celsius within the tubes. By comparison, a standard solar collector can only heat water between 60 and 70 degrees Celsius."

The evaporated combination reaches these high temperatures, and small amounts of the catalyst are added to produce hydrogen. This hydrogen is then guided to a fuel cell to create electricity for the building, or to be stored in a tank for later on.

Hotz compared the system to three separate technologies according to their exergetic performance, which is a way of describing the amount of a given quantity of energy that can be converted to "useful work." The three different technologies were the standard photovoltaic cell, which converts sunlight into electricity to split water electrolytically into oxygen and hydrogen; a system where photovoltaic cells turn sunlight into electricity, which is then stored in batteries such as lithium ion, and a photocatalytic system that creates hydrogen much like Hotz's system, but is not quite "mature" yet. Hotz made sure to conduct these comparisons in February and July in order to observe system performance in winter and summer.

"The hybrid system achieved exergetic efficiencies of 28.5 percent in the summer and 18.5 percent in the winter, compared to 5 to 15 percent for the conventional systems in the summer and 2.5 to 5 percent in winter," said Hotz.

Hotz also performed a cost analysis and discovered that his hybrid solution is the least expensive compared to traditional systems, with the hybrid's installation costs totaling $7,900 for summer requirements. He did admit that a fossil fuel-fed generator would be the only cheaper option.

"The installation costs per year including the fuel costs and the price per amount of electricity produced, however, showed that the (hybrid) solar scenarios can compete with the fossil fuel-based system to some degree," said Hotz. "In summer, the first and third scenarios, as well as the hybrid system, are cheaper than a propane or diesel-combusting generator."

Other benefits associated with the hybrid system include the efficient production of hydrogen without "significant" impurities, and the option to shut down portions of the rooftop structure or even sell excess energy back to the grid if the system produces more energy than needed in the summer. A hybrid rooftop system would need to be large enough to produce electricity needed in the winter, and if it can accomplish this, then that would mean it would produce excess electricity in the summer, according to Science Daily. Those located in rural areas could especially benefit from such a system, since traditional forms of energy can be too expensive or difficult to receive.

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By sleepeeg3 on 8/11/2011 1:40:20 AM , Rating: 3
How much of a a risk is there of blowing off the roof of your house from highly flammable hydrogen and methanol?

Also, what about the repair costs of such a system? Were they factored in?

RE: Boom!
By sleepeeg3 on 8/11/2011 1:57:36 AM , Rating: 2
Edit: It looks like the "traditional" and "conventional" designs they are talking about refer to existing solar power technologies so this only applies to off-grid users.

RE: Boom!
By AnnihilatorX on 8/11/2011 8:09:29 AM , Rating: 2
The roof from that diagram only consist of copper pipes with methanol and H2O mixture, which does not really combust well.
The storage tanks for H2 inside the house needs secure storage however.

RE: Boom!
By irjsiq on 8/13/2011 1:56:25 PM , Rating: 2
Containing Hydrogen is more difficult than attempting to 'Corral' a room full of Kindergartners!
I have long advocated that H2+O be generated on-site, or aboard H2+O vehicles, and reconverted to H2O as quickly as possible, perhaps storing the energy in batteries, UltraCapacitors, etc ... The 'nano-world' is changing Physics, and it's 19th Century Laws almost daily!
So storage of energy in forms other than H2 is expanding very rapidly.
Regarding 'Storage of H2' One recent article, also 'nano', combined Clay Particles with Polymers, thus yielding spaces which 'taxed' the escape of H2; and that was before the word(s) 'Graphene-Graphane' were popularized, so tomorrow???

Roy J Stewart,
Phoenix AZ

RE: Boom!
By Paj on 8/11/2011 8:16:44 AM , Rating: 2
Probably about the same amnount of risk as a gas main exploding?

RE: Boom!
By howsolarpanels on 8/11/2011 9:35:44 AM , Rating: 2
You are right, I haven't thought about the dangers of hydrogen. It is very true that this experiment will neve come to life, as seen on
Too many good innovations by MIT scientists has been rejected by governments.

RE: Boom!
By Samus on 8/11/2011 1:42:31 PM , Rating: 3
Something tells me you can't legally have this configuration in a populated residential area. With all the equipment he has his neighbors probably think he's making crystal meth.

By KillerNoodle on 8/11/2011 10:19:16 AM , Rating: 2
Seems like a great deal of this article is copy, pasted, and poorly altered from Science Daily. Why mention this more than the one butchered line at the end?

RE: :-(
By kattanna on 8/11/2011 10:27:55 AM , Rating: 2
sadly, they do that a LOT. many of "their" science articles originate from science daily

RE: :-(
By rhuarch on 8/24/2011 12:13:07 PM , Rating: 2
Many of Science Daily's articles are just Copy/Pasted from Physorg is like the Reuters of science news. Most stories get reported there first, and then propagate through the rest of the internet.

Long term storage
By Conficio on 8/11/2011 3:18:46 PM , Rating: 2
Why not store the hydrogen for longer term, so that the summer/winter differences can be bridged.

Also why not using the hydrogen for other uses such as heating, cooling, air conditioning, powering your car or lawn mower.

Would it be feasible to cook and grill directly with the hydrogen?

RE: Long term storage
By irjsiq on 8/13/2011 2:18:32 PM , Rating: 2
Hydrogen is very difficult to contain. The 'Atoms' are so small that they simply 'flow through' the microscopic 'pore' opening between, and maybe even through the Atoms, hence; Materials, composing the walls of the Containment Vessel.
Various Hydrides are under evaluation ... if the Labs could/would join forces there may already be an Hydride-Storage solution!
Use of H2 for Barbeque okay; however, as H2 burns with an 'invisible' flame, Never put your hand over the Grill!
Placing 'Wood Chips' on the burner Stones first would create sufficient smoke for one to see where the heat is!

Roy J Stewart,
Phoenix AZ

stored excess
By rakewell2 on 8/10/2011 9:10:39 PM , Rating: 3
I'm thinking that the stored hydrogen excess could be used to run your car. This is very promising.

sounds good
By kleinma on 8/10/2011 8:42:23 PM , Rating: 2
Keep up the good work. Sounds like something I would want at my house.

Where is the hydrogen coming from?
By Solandri on 8/11/2011 3:10:15 PM , Rating: 2
If it's coming from the water, then great!

If it's coming from the methanol, then this is just a roundabout way of burning methanol as fuel.

By irjsiq on 8/13/2011 1:43:41 PM , Rating: 2
"Exergonic", closest to 'exergetic', which was not found in online dictionary!

from article: "Hotz compared the system to three separate technologies according to their exergetic performance, which is a way of describing the amount of a given quantity of energy that can be converted to "useful work."

As a former Firefighter, I was often criticized for using 'Vocabulary'*, my reply: "Were it not for words, we should All be 'Grunting' to one another . . . new words are new friends, the more you have the luckier you are!

Question regarding the 'bio-methanol':
How much is consumed, and where does the 'expended methanol' go?
and, The Water? 'Tap' or 'Purified-Distilled', and how much water is lost to the atmosphere, etc.?

This article explained the 'Capturing and function of this system better than any other articles covering the same ?Invention? !
Roy J Stewart,
Phoenix AZ
*Vocabulary and criticism thereof?
A popular mountain wilderness area between Phoenix and Payson is spelled 'Mazatzal'(ma Zat zl), but as no one takes the time to learn how to pronounce the word correctly; everyone says: 'Matazels'!

"Nowadays, security guys break the Mac every single day. Every single day, they come out with a total exploit, your machine can be taken over totally. I dare anybody to do that once a month on the Windows machine." -- Bill Gates

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