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."
1. At least eight photons are required to store one molecule of CO2 which means 1665 kJ of light energy are required to store 477 kJ in the plant. Max efficiency is 0.286 or 28.6 %
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.286x.43x.8x.67 =.066 or 6.6%
So, the Wikipedia editor left out an important part of the equation. Ops! As a side note, asking "Can anybody shed some more light on this?" instead of "Anybody have any more insight into this?" would have earned you a cheesy pun point.
Indeed. Water alone is bad enough for corrosion, let alone water containing free hydrogen and oxygen. Some of their cells have operated only for days. On top of this, the cells use an expensive "special glass" (haven't seen anywhere that goes into more detail than that) to pull off the trick. Really, the tech looks to be at about the point that solar cells were in the '60s. Not that hydrogen cars [daughtersoftiresias.org] are a realistic solution to our current problems anyways.
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.
Hydrogen is a lousy source of potential energy. It's bulky, corrosive, explosive, leaks *very* easily, is very inefficient, and in general is an expensive pain to work with. It's no surprise that most of the energy storage mechanisms being looked into for bulk storage of electricity are not hydrogen but "pumped" storage, either water or air. The largest in the world is a pumped water storage system in China. As for battery/capacitor breakthroughs, there are now no fewer than three of them trying to make t
Electricity is, by far, more valuable than hydrogen (or any common chemical fuel for that matter). I'd take a 40% efficient solar cell that produces electricity over a 15% efficient solar cell that produces hydrogen any day.
Also note that that the article states that they could *theoretically* get this hydrogen cell up to 15% efficient. Hard to get excited when the theoretical max of a new idea can't even match the practical (if uneconomical) maximum of existing technology.
I disagree. Lots of the best places for solar collection are a long way away from human habitation. If you can efficiently produce hydrogen (or, better, an energy-dense hydrocarbon) in these places then you can easily transport it to where it is needed.
According to http://en.wikipedia.org/wiki/Electrolysis#Electrolysis_of_water [wikipedia.org], electrolysis of water to produce hydrogen has an efficiency of more than fifty percent, at least theoretically. If that's true, then you might be better off using the 40% efficient cell to generate hydrogen at 20% efficiency, rather than using this new cell to generate hydrogen directly at 15% efficiency.
Of course, there are lots of other factors which might make using the new one more attractive. In particular, it certainly s
Parent is first one to point out storage benefit...
Grandparent missed to point out that good storage doesn't only mean to transport energy in space, but also in time -- for later use. So, pure electrons really don't cut it...
I'm not going to waste my time digging up the numbers to refute this.
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.
Electric heat pumps can actually get more heat in your home than they use to do it.
Heat pumps as the name implies aren't generating heat, they're moving it from one place to another and heat pumps using chemical fuels (like natural gas) also get more heat into your home than they use to do it. I doubt converting electrical energy to heat via resistive heating is any more efficient than converting a chemical to heat via combustion. (Certainly not when you consider that most of that electricity is generate
The break even problem hasen't generally been true for almost 20 years.
All consumer grade solar cells easily produce more power than they use.
Only the super high efficiency 40+% cells used by NASA and the like are even close to using as much energy to create as they will generate. This is do not just to the manufacturing techniques but to the harsh, highly radioactive environment they are in which decreases the life expectancy of the cell.
I thought that current solar cells have efficiencies of up to 40%. So how is this better?
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.
This one isn't even 15% efficiency...That's what they think they could get up to. That's competitive with most commonly produced cells...the 40% ones you're talking about are far too expensive to be produced outside of a lab environment, so while they're more efficient, it's more practical to just put down more of the cheap ones. The thing that's cool about this is the conversion efficiency; converting water to hydrogen and oxygen using traditional methods isn't itself all that efficient. If they could get t
Except where space/weight might be very limited (eg. space applications), the important measure is $/W. Silicon PV is nowhere near a viable $/W for general purpose application.
Who cares if the efficiency is 10% and you have to cover your whole house in the stuff?
It's better if you want to create hydrogen, because using electricity to convert water to hydrogen is horribly inefficient. However, the whole idea is pretty stupid when you consider that with today's technology you could just generate electricity, charge a battery, and run an electric car. The whole process would be much more efficient than the 15% advertised by this system, and even the 15% is just a theoretical number. Sadly, hydrogen cars are basically a scam brought about by oil companies to distract
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.
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.
If you own a four stroke, spark ignited, internal combustion engine, you have one now. The conversion to run on hydrogen gas instead of liquid gasoline is quite trivial.
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.
The practicality of your idea fails on several fronts.
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!"
Thermal Depolymerization can convert almost any organic substance into raw hydrocarbons. So yeah, converting humans into oil is entirely possible.
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=
First they want to make energy from our food. Now they are making it out of our drink
I'm reminded of a mediocre Niven/Pournelle novel where dramatic climate change was blamed on inhabitants of a space station needing to be resupplied with oxygen from time to time. What will burning all the water do to the planet? Won't someone please think of the fishes??
The water splitting requires 1.23 volts, and the current experimental configuration cannot quite achieve that level so the researchers add about 0.3 volts from an outside source. Their current system achieves an efficiency of about 0.3 percent.
perhaps they should take a lesson from real photosynthesis and use an equivalent of a second photosystem. in photosynthesis,photosystem II is excited to a higher state followed by an electron transport system producing ATP then with a second photon to excite photosystem I which produces the reducing equivalent required for further reactions.
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"?
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."
there's nothing saying we couldn't use energy from nuclear plants to electrolyze water but considering the sheer amount of energy in the form of sunlight that is available, ignoring it is not an option. as you said, storing hydrogen is the problem although we have catalysts to react carbon dioxide and hydrogen to form numerous compounds, hydrocarbons, misc carbohydrates, even plastics. imagine it, using sunlight or nuclear power to reduce and remove carbon dioxide from the air while simultaneously making
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 [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...:( )
[...] 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.
So they don't even pretend to understand how it works, but they know it can eventually attain 15% or so efficiency.
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.
well, it's only H2 on demand if you can drive under direct full sun with enough solar panels on your roof to do it. Since solar panels get 40% or so efficeinecy, and this gets 15%, and considdering solar powered cars barely run at 25MPH in desert tests after using rediculous aerodynamic and wieght reduction methods, there's no way you can make enough H2 on the run. The only possibility for this would be refueling stations making H2 on location, instead of having it trucked in, but even with that, in most
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.
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.
That would require a large network of small pipes all across the painted surfaces of the car to bring the water to the paint. This would be rather complex but not undoable. You would have to consider the possibility of any small dents as well, and ensure that that doesn't ruin the whole network.
The way to deal with dents is to use lots of interconnections and make the transport system from a tube in a tube design. The outer tube contains a polymer that hardens when exposed to H2O, any dent significant enough to cause the tubing to burst seals itself and the interconnections route around the blocked tube. Think of it as a cross between internet routing and the bodies clotting system =)
Awright, before you start building the converter for the roof of your car, I'm going to put on my Homer Simpson hat and lecture that "in this house, we obey the laws of thermodynamics." And now for something completely different... math!
Let's take your average car. Not being picky, I'll surf over to Carmax and choose whatever pops-up first... hmm, Honda Element. Not what I expected, but I'll run with it. Pertinent specs:
- 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... damn. Okay, you're not running at peak power all the time. Let's be generous and say you need 10% of peak for grocery runs. That's 57.5kW. The ratio of consumed-to-collected energy is 57.5/1.188 = 48.4. So for every minute you drive your Honda Element at 10% of peak-rated power, it needs to be illuminated by sunlight for 48.4 minutes. If we make the generous assumption of 12 hours of 1kW/m^2 insolation, you'll be able to collect enough energy from sunlight to drive a whopping 14.076 minutes each day.
S #1: What? A swallow carrying a coconut?
A: It could grip it by the husk!
S #1: It's not a question of where he grips it! It's a simple question of weight ratios! A five ounce bird could not carry a one pound coconut.
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.
So, this is also exactly why we also don't drive around in portable oil refineries. A slightly more clever arrangement of the involved technolgoies could prove surprisingly useful in real-world applications.
Duct Tape* I used to think it was duck tape too. But then I got arrested by the RSPCB and put through their re-education program, kinda like in that Clockwork Orange thingy.
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
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Not that hydrogen cars [daughtersoftiresias.org] are a realistic solution to our current problems anyways.
15% efficiency (Score:2, Interesting)
Re:15% efficiency (Score:5, Insightful)
Parent
Re:15% efficiency (Score:5, Informative)
Parent
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As for battery/capacitor breakthroughs, there are now no fewer than three of them trying to make t
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Also note that that the article states that they could *theoretically* get this hydrogen cell up to 15% efficient. Hard to get excited when the theoretical max of a new idea can't even match the practical (if uneconomical) maximum of existing technology.
-matthew
Re:15% efficiency (Score:5, Insightful)
Parent
Re: (Score:3, Interesting)
According to http://en.wikipedia.org/wiki/Electrolysis#Electrolysis_of_water [wikipedia.org], electrolysis of water to produce hydrogen has an efficiency of more than fifty percent, at least theoretically. If that's true, then you might be better off using the 40% efficient cell to generate hydrogen at 20% efficiency, rather than using this new cell to generate hydrogen directly at 15% efficiency.
Of course, there are lots of other factors which might make using the new one more attractive. In particular, it certainly s
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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
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They also have substantially higher energy density today than the theoretical limit of chemical batteries. That counts for an awful lot.
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Heat pumps as the name implies aren't generating heat, they're moving it from one place to another and heat pumps using chemical fuels (like natural gas) also get more heat into your home than they use to do it. I doubt converting electrical energy to heat via resistive heating is any more efficient than converting a chemical to heat via combustion. (Certainly not when you consider that most of that electricity is generate
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All consumer grade solar cells easily produce more power than they use.
Only the super high efficiency 40+% cells used by NASA and the like are even close to using as much energy to create as they will generate. This is do not just to the manufacturing techniques but to the harsh, highly radioactive environment they are in which decreases the life expectancy of the cell.
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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.
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The thing that's cool about this is the conversion efficiency; converting water to hydrogen and oxygen using traditional methods isn't itself all that efficient. If they could get t
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$/watt is more important than eficiency (Score:2)
Who cares if the efficiency is 10% and you have to cover your whole house in the stuff?
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However, the whole idea is pretty stupid when you consider that with today's technology you could just generate electricity, charge a battery, and run an electric car. The whole process would be much more efficient than the 15% advertised by this system, and even the 15% is just a theoretical number. Sadly, hydrogen cars are basically a scam brought about by oil companies to distract
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
need to get hydrogen engines??? (Score:3, Informative)
If you own a four stroke, spark ignited, internal combustion engine, you have one now. The conversion to run on hydrogen gas instead of liquid gasoline is quite trivial.
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
Energy from water... (Score:2, Funny)
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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=
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I'm reminded of a mediocre Niven/Pournelle novel where dramatic climate change was blamed on inhabitants of a space station needing to be resupplied with oxygen from time to time. What will burning all the water do to the planet? Won't someone please think of the fishes??
photosynthesis (Score:5, Interesting)
could eventually (Score:5, Funny)
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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."
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Isn't "could eventually" one of those warning phrases that tells you something is dubious,
Sure. It think it's really more like communicating an upper limit. The more interesting number would be cost/watt.
15% (Score:2)
And then begins the energy intensive liquification stage. Having those carbon atoms attached to your hydrogen is just a huge advantage.
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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.
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As opposed to current gasoline vehicles, which are non-flammable.
Every auto shop I've been too has very high ceilings, and big, wide open doors that can easily vent TONS of vapor.
When my idiot neighbor put a shovel through a natural gas line, the fire department didn't t
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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.
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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:You don't need high efficiency though... (Score:4, Insightful)
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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.
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Re: no free lunches (Score:4, Insightful)
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