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New Solar Cell Harvests Hydrogen From Water
Engadgets is reporting that researchers at Penn State have built a new kind of solar cell that can harvest hydrogen directly from water. "The folks at Penn State have now developed a process that more closely mimics the photosynthesis process in plants, and while we won't pretend to understand all the nitty gritty of dye usage and other such nonsense, we do know that such a system could eventually attain 15% or so efficiency, providing a nice and clean way to gather power for that fuel cell car of the future."
The summary = the article.
The original article was on Science Daily a few days back.
ad logicam Claiming a proposition is false because it was presented as the conclusion of a fallacious argument.
i think thats 40% towards creating electricity, this is 15% towards creating pure Hydrogen
Step 4 is "put it outside in sunlight" I think the point is that they have bypassed using electrolysis, instead using the sunlight to stimlate a dye and catylist that splits the water directly. If so, it would be much more efficient than using a solar cell and electrolysis.
GE/CS/IT d- s: a- C++++$ UL+++ P-- L++++ E W+++$ N+ o? K- w---() !O M- V- PS+ PE(++) Y+ PGP+++(+) t+++ !5 X++> R- t
Sigs are too short to say anything truly profound so read the above post instead.
Isn't "could eventually" one of those warning phrases that tells you something is dubious, like "up to twice as long" or "she has a great personality" or "you're violating our patents but we don't want to tell you which ones"?
I'm an American. I love this country and the freedoms that we used to have.
Yep. And 40% is a bad number; the cells that have that efficiency rating are a long way from production. 15% is pretty similar to what most solar cells on the market get today.
ad logicam Claiming a proposition is false because it was presented as the conclusion of a fallacious argument.
15% efficiency would actually be pretty good considering by some calculations photosynthesis efficiency is around 5 to 20%.
:( )
Here is one calculation showing ~6.6% photosynthesis efficiency
It takes into account things like canopy shading, which wouldn't necessarily apply to this, but here's the link:
http://www.upei.ca/~physics/p261/Content/Sources_Conversion/Photo-_synthesis/photo-_synthesis.htm
I tried to find a peer reviewed one, but can't find one right now(I'm at work, break almost over...
Accentuate the positive, don't waste your mod points on the negative.
The real interesting point about this though is that it skips the extra electrical load to free the hydrogen from the water. Assuming there are no gotchas with the production of the dyes and such that make up this system, it could be the most ecologically sustainable system yet. The big problem with most of our fuel sources is that they either A) are non-renewable (oil), B) create greenhouse gases (oil, coal, ethanol), C) are non-portable (solar, wind, geothermal, nuclear [for anything but heating]), D) create radioactive (or hazardous in general) waste (nuclear), or E) Have higher energy input than output (hydrogen, and some say ethanol). Assuming this system works using just the dyes, water, and sunlight, that eliminates the high energy need to produce the hydrogen, thereby giving us a ultimately solar based energy system that's also portable. Of course we also need to get engines that run on hydrogen that are also safe and efficient, but this is a step at any rate.
Now, what concerns me about this system is that usually the dyes used in these things are rather short lived and tend to break down after hardly any time at all. Maybe this should be one of the first real uses of biotech, we should engineer some microbes that produce this dye and live off O2 and water (and various proteins naturally), then we just harvest the excess hydrogen.
Curiosity was framed, Ignorance killed the cat.
Not necessarily. If this new technology could eventually reach 15% efficiency, then it's still nothing particularly wonderful when you take into account the fact that some firms like Boeing Spectrolabs boast solar cells with efficiencies as high as 40% (they do use "solar concentrators", so it's possible that their panels may take up several square meters of surface area for every square meter of panel surface. Not having seen their designs, I wouldn't know).
Take a 40%-efficient solar cell and use it to feed power to a 50%-efficient electrolyzer, and you get a net total efficiency of 20%, which is better than the maximum estimated efficiency of this dye-based approach.
If they dye approach proves to be cheaper or can also be enhanced by solar concentrators or what have you, then it may have some value from an economic perspective, but I don't see anything 15% efficient providing dense solar power solutions compared to other technologies already available.
The other thing to keep in mind is that the output from this dye is hydrogen, not electricity. If you need electricity from one of these dye-based hydrogen generators, you'll need to marry it with a fuel cell or something long those lines which will further degrade efficiency. In terms of raw electrical output-per-square meter of deployed solar collectors, you'd be better off with conventional solar cells in the 15-20% efficiency range.
Efficiency is not so important in this application because of the useage of your typical car. A car typically sits around for 75% of the day doing nothing. This whole time this process could be converting water into hydrogen.
The only time it would not work is during long highway trips. During these times some kind of accelerated process or hydrogen filling station would be needed.
I am TheRaven on Soylent News
Well, personally I don't care how we get H2. It's all pointless anyways. H2 will never be a common fuel for motor vehicles.
Here's why:
In regards to using liquid H2 in vehicles:
- It's too dangerous. You're driving a bomb. Every car using liquid H2 is a has-mat vehicle by legal definition. Imagine the terrorists glee where they don't have to rent a car and then build a bomb because the rental car IS a bomb.
- it must be trucked in liquid form - can't be pipelined, and therefore we'll have to deal with massive supply issues, thouands more has-mat trucks on the roads, and reduculous logistics.
- fuleing requires extensive safety measures and extremely specialized and expensive equipment
- you either have MASSIVE pressurized tanks (taking a very large portion of your vehicle space and weight) or you have to have the H2 actively cooled to extremely cold termurateres, requiring the car to be powered 100% of the time.
For metal infused H2 gas vehicles:
- well, it's much safer... but:
- maximum range uning even theoretical technologies is about 220 miles per fill up, assuming you leave enough seating room in a large SUV for 5 people and no luggage.
- the tank is huge, and weighs hundreds of pounds, eating at vehicle efficiency and space (too big for those small commuter cars in Europe)
- IT TAKES UP TO 8 HOURS TO FILL UP, and requires active cooling to prevent explosions while doing it.
H2 in general:
- it's dangerous to use a vapor gas as a fuel. Imagine auto shops all over the country having to worry about gas being spilled during repairs? Spill hydrocarbon, just avoid dropping a spark in the liquid until you soak it up with sawdust. Cause an H2 leak and you have to evacuate the building, no different than a natural gas or propane leak. Also, if liquid H2 leaks, you not only have to worry about combustion, but vapor expansion and extreme freeze issues.
- It costs 3-5 times more energy to make it that it would to simply run the car on electricity
- It's expensive. best estimates, you go the same distance on H2 for 2-4 times the cost of gasoline, and that's with all the current government funding lowering the costs.
- Where do you plan to store all the H2? Large scale containers are very difficult to make assuming you're storing it in liuquid form. We simply don't have enough room to store it in gaseous form.
- Fuel cells don't get repaired, they get replaced. The repair costs will be immense, collision insurance even worse (not to mention the danger issues insuring rolling bombs).
- burning H2 directly in ICEs is barely more efficient than burning ethanol.
- minimum car price. You can forget about those $7,000 cars. Minimum price for a fuel cell vehicle will be in the 20K range once the government subsidies stop becoming affodable.
no, we can't power every vehicle on earth on ethanol
yes, we will run out of oil, sooner than you like to admit
yes, we havre to do something, but what?
What is the answer? Super conducting electrical grids (which we can make today with existing technology at reasonable costs), fed by renewable energy in target locations around the world (wind farms where it's windy, water where there's natural falls, solar in the deserts, etc). We use all that to recharge plug-in cars using batteries from Toshiba and others companies that have already been developed which have as quick as 90 second recharge times. For those of you who say we can't do it, that we can't run recharge units all around towns for people to plug into on the run, well look at how Alaska has done it, and many other countries in the fridgid north of Europe, where cars that don't have engines running need to be plugged so their heaters can prevent fuel lines from freezing. Every parking meeter in some coutries have power cables attached. We CAN do it. It's been done before. We'll still use ethanol as a backup to the battery using ethanol in ICEs until small turbines (like BMW uses in their motercycle) become more cost effective through mass production.
There is no contest in life for which the unprepared have the advantage.
I'm not sure I understand why my car needs to have a power plant in it. Why can't it just have a large capacitor or bank of batteries, which I can swap out at the filling station? Obviously I am not going to wait for charging at filling time, but why not just swap out the uncharged capacity for charged capacity much as we change out propane tanks?
Then the power can be generated on the grid. If that is nuclear, coal, hydro, solar, or wind power - it can be whatever makes sense for the region. What ever is used, the filling station grabs the electricity from the grid and charges up batteries or capacitors. I swap mine out for a charged one and pay for the service.
Seems to me that this is something we could do now. Seems to me this way we could adopt newer, cleaner sources of power much quicker than waiting the life span of the auto.
Let's take your average car. Not being picky, I'll surf over to Carmax and choose whatever pops-up first
- Engine: 2.4L 166-hp (~575kW) inline-4
- Outside dimensions: 172" x 72" (4.4m x 1.8m)
So you've got 7.92 sq.m. of available roof area. I'll assume you can cover that 100% with your solar converter, and I'll further assume you can keep it pointed normal to the incident light. Typical insolation is 1000W/m^2, so your roof-mounted collector can harvest 7.92kW. Period (i.e. you don't get more energy than what is incident on the vehicle's cross-section.) You're collecting solar energy, and storing it in the potential reactive energy between hydrogen and oxygen. With a 15% efficiency, your converter stores 1.188kW while it's illuminated.
Getting back to our example Honda Element - 575kW engine
And therein lies the fundamental limitation. There isn't enough energy intercepted in a vehicle's cross section to make this structure viable. At 100% conversion efficiency, you just start to be able to power the econobox-class vehicles for around-town drives. Anything with distance or power requirements will need to be fueled by something much larger than the vehicle itself.
Go ahead and try. Electricity is far more valuable than chemical fuels. You can do so much more with it with much more efficiency. Electric cars, for example, run at, what, 90% efficiency? Electric heat pumps can actually get more heat in your home than they use to do it. You can produce light very efficiently as well. Ever try to light your home with natural gas? Electricity is the universal form of energy with the highest value, joule for joule.
I'm repeating myself in this thread, I know, but this point is very important:
The ONLY reason that chemical fuels seem valuable now is because we essentially get them for free. Or rather, all the work has already been done to store the energy. We just need to dig it up, refine it a bit, and get it where it is needed. If there ever came a time when there was no natural hydrocabons available, we'd very quickly realize just what a waste chemical fuels are.
"THERE IS NO JUSTICE, THERE IS ONLY ME." -Death