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Thursday, September 27, 2007 Hydrogen from AlgaeContinued from page 1 By Prachi Patel-Predd
Switching 100 percent of the algae's photosynthesis to hydrogen might not be possible. "The rule of thumb is, if we bring that up to 50 percent, it would be economically viable," Melis says. With 50 percent capacity, one acre of algae could produce 40 kilograms of hydrogen per day. That would bring the cost of producing hydrogen to $2.80 a kilogram. At this price, hydrogen could compete with gasoline, since a kilogram of hydrogen is equivalent in energy to a gallon of gasoline. In 2000, Melis, working with researchers at the National Renewable Energy Laboratory (NREL), found that depriving the algae of sulfur nutrients forced the cells to make more hydrogen. The researchers were only able to deprive the algae of sulfur for a few days at a time, but during that time, about 10 percent of the algae's photosynthetic capacity went toward making hydrogen. Researchers at NREL are making progress in increasing hydrogen-production efficiency, according to lead researcher Michael Seibert. They can now force the algae to generate hydrogen for up to three months, as opposed to just a few days. Seibert expects that Melis's chlorophyll-trimmed algae will be useful when the process is transferred to large bioreactors. Until the NREL researchers test the mutant algae, though, he says that it may be too early to tell. |
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Cheap Hydrogen
01/31/2008
Massachusetts Institute of Technology
Comments
nick47g on 09/27/2007 at 6:28 AM
17
My thought is that, since it has a built in deficiency, in the wild it would be out competed by it's fully photosynthetic bretheren.
cyberpageman on 09/27/2007 at 7:40 AM
27
SirLanse on 09/27/2007 at 9:05 AM
35
This makes the algea GROW.
The problem with going really big on this is, collecting the H2 from a lake. This forces you to have a glass covered greenhouse. The oil producing algea could be grown in open lakes.
eak on 09/29/2007 at 1:20 AM
8
Suppose you had H2. You could transport to filling stations, compress it, and fill up vehicle fuel tanks, and then in the vehicle decompress it, and feed a fuel cell, generate electricity, and power an electric motor. A fuel cell vehicle (FCV) is just a battery electric vehicle (BEV) with some of the batteries (but not all) replaced by a tank and a fuel cell. The only problem is that mobile fuel cells (e.g. PEMs) are inefficient, converting more than half of the energy in the H2 into heat instead of electricity. What else could you do? You could turn the H2 into electricity in a stationary fuel cell (e.g. molten carbonate, much more efficient than PEMs) and follow that with a steam turbine (sort of combined cycle). That combination has been prototyped, and in the future with development is estimated to reach 70% efficiency. Transmit this power over the grid (92% efficient), and charge a battery pack in a BEV or plug-in hybrid, and then deliver that battery power (86% efficient) to the motor and you get 70%*92%*86%=55% efficiency, which is higher than anything you'll get from the compress/transport hydrogen and then decompress and convert it to electricity on the road.
Of course if one had electricity to start with, it would be even more efficient to just use it directly (to generate H2 from electricity would be crazy). Generating H2 from sunlight might make sense, but the above analysis suggests it does only if the efficiency of sunlight to H2 is much greater than the current sunlight to electricity efficiency of 30% (cost-effective solar thermal). Given current mobile PEM fuel cells, it might have to be as much as 60% efficient to beat 30% efficient sunlight to electricity. That seems extremely unlikely (NREL's algae for biodiesel acheived only 7.5% efficient conversion of sunlight to oil, for example).
acetonitrile on 10/01/2007 at 5:54 PM
1
RosenfeldR on 10/03/2007 at 10:04 AM
1
Hydrogen generated during the day can make electricity at night or on a very cloudy day.
Also, some people feel that they need more range for their electric vehicles. Vehicles with hydrogen stored in tanks can travel farther between refueling than vehicles with electricity stored in batteries.
Grak on 10/05/2007 at 11:34 AM
1
But if it really is a nearly catalytic system, I can see this working quite well. The algae are pumped along through enclosed, transparent flow channels under sunlight. When they reach the end of the channel, you feed them back to either be "fattened up" with sulphur rich diet or they're flocculated and recycled as nutrient for the next batch.
Either way, this is not as simple as dumping algae into a pond. But I still like the concept.
killian on 10/09/2007 at 10:16 PM
55
Batteries in vehicles also store energy, at efficiencies >85%. Such efficiency in the H2 world is unheard of as far as I know of.
killian on 10/09/2007 at 9:47 PM
55
Actually, as I understand NREL's work on algae from the late 1990s, open ponds were found not to work, due to contamination and other strains crowding out the desired strains. They suggested that sealed bioreactors are required. Do you know of more recent research that suggest otherwise?
Also, I don't suggest photovoltaics, as "high-efficiency solar panels" might suggest in your reply. Solar thermal is enormously lower $/kW and $/kWh than photovoltaics. PV has use in residential applications, but in large installations, solar-thermal (mirrors in the desert powering steam turbines) is probably a factor of 4 or 5 more cost effective.
There are actually several companies trying to commercialize biodiesel from algae, and it is much more high-tech and costly than your analysis suggests (and it involves sealed bioreactors).
There is also the usage-end to consider, as opposed to the production end. Electric vehicles are 2-4 times the efficiency of biofuel and H2 powered vehicles, which again means that much less land is required to generate the same 2.7 trillion vehicle miles traveled each year (rising at about 2%/year) that our nation seems to require.
whoisrtp on 03/28/2008 at 12:03 AM
1
Neilzero on 10/09/2007 at 2:19 PM
5
We already produce H2 = hydrogen. It is available for welding in all cities and many towns and villages. It has some disadvantages over other transportation fuels.
Suppose you had H2. You could transport it to filling stations, compress it, and fill up vehicle fuel tanks, and then in the vehicle decompress it. This provides refrigeration which will sometimes be useful to keep your picnic cold or frozen, to cool the battery and motors and to cool the passengers. In very cold ambient, the cold is a liability. Some of the energy from decompressing can be used = see air powered car. The hydrogen feeds a fuel cell, generates electricity, then powers an electric motor. A fuel cell vehicle (FCV) is just a battery electric vehicle (BEV) with some of the batteries (but not all) replaced by a tank and a fuel cell. The only problem is that mobile fuel cells (e.g. PEMs) are inefficient, converting more than half of the energy in the H2 into heat instead of electricity. The heat is useful in cold weather.
What else could you do? You could turn the H2 into electricity in a stationary fuel cell (e.g. molten carbonate, much more efficient than PEMs) and follow that with a steam turbine (sort of combined cycle). That combination has been prototyped, and in the future with development is estimated to reach 70% efficiency. Transmit this power over the grid (92% efficient at best), and charge a battery pack in a BEV or plug-in hybrid, and then deliver that battery power (86% or less efficient) to the motor and you get 70%*92%*86%=55% efficiency, which is higher than anything you'll get from the compress/transport hydrogen and then decompress and convert it to electricity on the road.
Of course if one had surplus electricity to start with, it would be even more efficient to just use it directly to generate H2 from electricity (50% efficient) Generating H2 from sunlight, or a SBSP = space based solar power, might make sense, but the above analysis suggests it does only if the efficiency of sunlight to H2 is much greater than the current sunlight to electricity efficiency of 30% (cost-effective solar thermal). Given current mobile PEM fuel cells, it might have to be as much as 60% efficient to beat 30% efficient sunlight to electricity. That seems extremely unlikely. NREL's algae for biodiesel acheived only 7.5% efficient conversion of sunlight to oil.
Me: Internal combustion vehicles and hybred electric vehicles can use several percent hydrogen fed into the air intake of the internal combustion motor. This is almost as efficient as present mobile fuel cells and much lower initial cost.
Hydrogen can be made from electricity, economically, when the wholesale price drops to about one cent per kilowatt hour, which occurs after midnight in many locales at present and will occur afternoons in June and July in locales with lots of solar energy. This hydrogen source could total 1% of the world's energy needs, so hydrogen could fill an important nitch. Does anyone have details on the molton carbonate fuel cell? Please refute, embellish and/or comment. Neil
killian on 10/09/2007 at 10:11 PM
55
You said, "Hydrogen can be made from electricity economically, when the wholesale price drops to about one cent per kilowatt hour,..." But the point of the gedanken I proposed is that it is inferior at any cost to produce H2 from electricity, since the electricity can be used directly more efficiently than H2.
Here is one reference for molten carbonate fuel cells:
http://en.wikipedia.org/wiki/Molten_carbonate_fuel_cell
You might also find this reference useful:
http://tinyurl.com/eccv6
XericClapton on 03/12/2008 at 12:46 AM
2
Neilzero on 10/09/2007 at 3:08 PM
5
amphora on 09/14/2008 at 9:30 AM
1
nick47g on 10/18/2007 at 8:59 AM
17
Are our troops dying so you can?
Every study that I have seen that figures in reforestation, shows that it has the biggest and most immediate payoff of any strategy.
Finally, electric vehicles, even ostentatiuos ones, are wildly more efficient than internal combustion powered ones.
DJTal on 10/19/2007 at 4:15 AM
116
pcinpc on 12/31/2007 at 2:34 AM
1
greencash on 05/20/2008 at 5:20 AM
1
I wonder if the real reason none of these viable solutions are being persued by the powers that be are because they may actually believe we can have hydrogen on demand using DC electrolysis with a specific alloy and a portable radio frequency generator to fracture water into hydrogen and oxygen creating an endless supply of clean fuel?