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New Solar Cell Harvests Hydrogen From Water
Posted by
ScuttleMonkey
on Mon Feb 18, 2008 01:27 PM
from the stealing-what-plants-crave dept.
from the stealing-what-plants-crave dept.
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."
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Science: Microbes Churn Out Hydrogen at Record Rate 168 comments
FiReaNGeL writes to mention that Penn State Researchers have improved on their original microbial electrolysis cell design bringing the resulting system up to better than 80 percent efficiency when considering all energy inputs and outputs. "By tweaking their design, improving conditions for the bacteria, and adding a small jolt of electricity, they increased the hydrogen yield to a new record for this type of system. 'We achieved the highest hydrogen yields ever obtained with this approach from different sources of organic matter, such as yields of 91 percent using vinegar (acetic acid) and 68 percent using cellulose,' said Logan. In certain configurations, nearly all of the hydrogen contained in the molecules of source material converted to usable hydrogen gas, an efficiency that could eventually open the door to bacterial hydrogen production on a larger scale."
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TFA is worthless. (Score:5, Informative)
The original article [sciencedaily.com] was on Science Daily [sciencedaily.com] a few days back.
Re:TFA is worthless. (Score:5, Informative)
Parent
Re:TFA is worthless. (Score:5, Informative)
2. Only light in the range 400-700 nm can be used. This amounts to 43% of total solar incident radiation.
3. Canopy limits absorption to 80 %
4. Respiration required for translocation and biosynthesis requires about 33% of the energy stored which leaves 67%
The overall efficiency is then
Parent
photosynthesis (Score:5, Interesting)
could eventually (Score:5, Funny)
Re: (Score:3, Insightful)
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"?
Or "we'll develop it and then an 'energy company' which is a front for an oil conglomerate will swoop in and buy up all the intellectual property and sit on it."
15% would be pretty good (Score:5, Informative)
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 [www.upei.ca]
I tried to find a peer reviewed one, but can't find one right now(I'm at work, break almost over...
What they know (Score:4, Insightful)
So they don't even pretend to understand how it works, but they know it can eventually attain 15% or so efficiency.
...about those hydrogen cars (Score:5, Interesting)
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.
Re:15% efficiency (Score:5, Insightful)
Parent
Re:15% efficiency (Score:5, Informative)
Parent
Re:15% efficiency (Score:5, Insightful)
Parent
Re:Wrong. (Score:5, Insightful)
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.
Parent
Re: (Score:3, Informative)
It allows energy storage (in the form of hydrogen) for later use. Maybe it's not as efficient as using compressed air [sciam.com], as was described in the cover story in January's issue of Scientific American, but it's still worth investigating.
Re:15% efficiency (Score:5, Interesting)
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.
Parent
Re:15% efficiency (Score:5, Interesting)
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.
Parent
Re:15% efficiency (Score:4, Interesting)
For one, there is no standard battery pack, nor could there be without making all the systems similar enough. How would you like to own an electric sports can that has the same battery pack as a single seat local commuter vehicle? There's also the need to invest in sufficient numbers of battery packs by the stations to meet consumer need. Many gas stations server over 1k customers a day! Even counting that the batteries are being charged and then re-used, you'd have to have 250 packs to service a station open for 16 hours/day with a 4 hr. mean charge time.
There's also the issue of battery life. Since every battery eventually needs to be replaced, you have to have a way to track and credit or debit the customers for bringing in new or almost defunct batteries. That means every battery would have to have a battery life indicator on it, and a complex formula worked out for pricing. You: "I need recharged batt-paks." Service station attendant: "I only have once-recharged, and your's are at end-of-life, that'll be $1285.60, plus tax." You: "But I only need to go 50 more miles, I have brand new ones at home!"
Parent
Re:Yawnnn (Score:5, Informative)
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Re:Yawnnn (Score:4, Informative)
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.
Parent
You don't need high efficiency though... (Score:5, Insightful)
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.
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Re: (Score:3, Interesting)
Re:You don't need high efficiency though... (Score:4, Insightful)
Parent
Re: no free lunches (Score:5, Informative)
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 [wikipedia.org] 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.
Parent
Re: no free lunches (Score:4, Insightful)
Parent
Re: (Score:3, Interesting)
That's actually how I'd prefer my body to be disposed of when the med students are done with it. Burying corpses is so wasteful in the grand scheme of things.
=Smidge=