Can this satisfy the world's energy needs? High-altitude wind power.

[Ivan Seeking]

I was curious about the solar efficiency of the algae. Using his numbers and these

http://www.nafa.org/Content/NavigationMenu/Resource_Center/Alternative_Fuels/Energy_Equivalents/Energy_Equivalents.htm

I show an average of about 80 watts per sq meter. That's pretty amazing if true!

 

[Cliff_J]

Ivan - some of the biggest problems with BioDiesel is in the implementation. The fuel acts as a very effective solvent that dislodges gunk that's in the fuel system and can attack older hoses and seals that aren't robust enough to handle the fuel. Unlike a gasoline engine, the typical mechanical injection diesel operates with the fuel under incredible pressures and the tolerances inside the parts leaves little room for any impurities. Also, the system is very intolerant of any moisture, and biofuels don't help in this area.

E85 has a similar downfall, according to Motorweek (as I recall) the biggest limitation of E85 (besides the limited distribution of FFV cars setup to handle the fuel) is that when E85 was sent down an existing gasoline pipeline that its solvent-like characterists removed enough varnish buildup on the pipes that it caused leaks. So its distribution method is solely by truck at the moment, and explains its regional availability.

There is also E95 for diesels, and biodiesel can be blended to help with its cold weather performance. So there are some more things to understand than just fillin' 'er up.

With an educated consumer base who understands how to respect the biofuels they are a great substitute and even a 20% reduction would be outstanding. I was reading a report on a test-drill scenario where %5 of the worlds oil supply was cut off, and the price of oil went to $120 a barrel. I think a little consumer education, and maybe a little more monitoring by manufacturers (similar to warning lights) to assist in proper use of biofuels, that we as a planet could switch this problem around. Once the economics happen, I think it will occur whether the Luddities would like it to or not.

 

[joema]

Any alternative energy source if EVER expected to supply much of the world's energy, must be scaleable to gigantic industrial levels. This entails several requirements:

- Must fit within the available real estate. Does no good if it requires 3/4 continent full of windmills or solar panels.

- Must have significantly positive net energy balance (energy in vs energy out). If it takes more energy to manufacture or harvest than it produces, it's not workable.

- Must be economically affordable to build, including ALL development costs, and any related distribution and technology changes. Even if the technology works, if it costs $50 trillion if scaled to world need, that's not affordable. E.g, solar power satellites clearly would work on a small basis, but can't economically be scaled upward to world need.

- Must be implementable within the time frame for exhaustion of conventional energy source. For replacing petroleum, this means the alternative must be completely on line within two decades at the outside. For utility energy we have longer.

While there are many alternatives that work on a small experimental basis, there are very few that can be scaled to the titanic level required for global energy needs.

We can eliminate most alternatives as totally impossible based on the above criteria. E.g, hydrogen/fuel cells for transportation energy via solar or wind power. You can't complete fuel cell development, build solar arrays the size of Australia, replace the entire distribution infrastructure and replace most road vehicles with new technology within 20 years. It's impossible. If it's doable in 50 years, that's irrelevant, since global commerce can't stop for 30 years to await availability.

Another example of an alternative that works on a small scale but not a global scale is ethanol from corn. The yield is just too low, plus there's insufficient unused acreage for global-level output.

I don't know if all issues related to biodiesel from high yield algae are solvable. However it at least it satisfies the areal efficiency, net energy efficiency required, implementation cost and timeframe requirements. It also mostly solves the CO2 problem, as it only emits CO2 it absorbed during growth.

If a biodiesel from high yield algae project was scaled up to global size, it might encounter unforeseen problems that preclude implementation. However there are no current known insurmountable problems By contrast most other alternative approaches have already visible insurmountable problems if scaled to that level.

All issues about biodiesel in diesel engines can be solved by minor modifications of current engine and fuel production technology. You have to distinguish between somebody making biodiesel in their back yard from waste vegetable oil vs a well engineered large production complex.

Extrapolating from the numbers on http://www.unh.edu/p2/biodiesel/article_alge.html (141E9 gal/yr to replace all US transportation energy), to replace all global energy, it would take roughly 22x that much: (400 quadrillion BTU / (141E9 gal * 130000 BTU/gal). Land area required would be somewhat larger than Texas, but it could be 100% in non-arable land (e.g, deserts) around the world. It would use essentially existing distribution, storage, and engine technology, unlike other approaches that require total replacment of all those.

 

[Ivan Seeking]

While we agree much more than not, a few additional comments.

Also, a good link
http://www.eia.doe.gov/emeu/international/total.html

Any alternative energy source if EVER expected to supply much of the world's energy, must be scaleable to gigantic industrial levels. This entails several requirements:

- Must fit within the available real estate. Does no good if it requires 3/4 continent full of windmills or solar panels.

This is a little unfair since it would take less acreage for solar cells to produce the same amount of power as biofuels. However, we don't really know the well-to-wheels efficiency of either approach, so it is possible that neither would yield a net positive when all is said and done. Since in both cases we are talking about future technlogies, large scale production of products like paint-on solar cells [currently in development] could prove viable and superior to biofuels as solar energy converters. And taken at face value, at about 100 watts per sq meter, they already are.

- Must have significantly positive net energy balance (energy in vs energy out). If it takes more energy to manufacture or harvest than it produces, it's not workable.

From what I see, this is still a problem for many alternatives. I'm not convinced that we have any net positive alternative yet.

- Must be economically affordable to build, including ALL development costs, and any related distribution and technology changes. Even if the technology works, if it costs $50 trillion if scaled to world need, that's not affordable. E.g, solar power satellites clearly would work on a small basis, but can't economically be scaled upward to world need.

True, however, most Joes-on-the-street expect far too much, and most engineers expect far too little. It doesn't pay to be cynical based on guesses. The economy of scale can be extreme and surprising.

- Must be implementable within the time frame for exhaustion of conventional energy source. For replacing petroleum, this means the alternative must be completely on line within two decades at the outside. For utility energy we have longer.

It means that a set of solutions must be online within some time that some claim is as little as two decades. My feeling is that if some technologies pan out, we could do this in a decade.

While there are many alternatives that work on a small experimental basis, there are very few that can be scaled to the titanic level required for global energy needs.

Your opinion and far too broad a statement to defend.

We can eliminate most alternatives as totally impossible based on the above criteria. E.g,

So you say.

hydrogen/fuel cells for transportation energy via solar or wind power. You can't complete fuel cell development, build solar arrays the size of Australia,

not an accurate statement. Also, fuel cells are hardly in their infancy. To me the big question with fuel cells is the lifetime efficiency. Some people argue that when taken in total, it makes more sense to run hydrogen in IC engines, than fuel cells in electric vehicles. And we could run H2 in regular cars as well. I think it is BMW that makes a car that goes from petro to H2 combustion with the flip of a switch, which is a great solution to the chicken and egg problem. And the distribution technology for H2 is well under way - Iceland is changing to H2 right now.

replace the entire distribution infrastructure and replace most road vehicles with new technology within 20 years. It's impossible. If it's doable in 50 years, that's irrelevant, since global commerce can't stop for 30 years to await availability.

I agree that we are running out of time.

Another example of an alternative that works on a small scale but not a global scale is ethanol from corn. The yield is just too low, plus there's insufficient unused acreage for global-level output.

It only makes sense to me to grow the most eff bio-fuel crops.

I don't know if all issues related to biodiesel from high yield algae are solvable.

Twenty years to figure it out? Already looking bad.

If a biodiesel from high yield algae project was scaled up to global size, it might encounter unforeseen problems that preclude implementation. However there are no current known insurmountable problems By contrast most other alternative approaches have already visible insurmountable problems if scaled to that level.

It has never really been done either. They need to move ahead with this program quickly and see if it really pays in joules. I can still imagine this ending up as a net loss.

All issues about biodiesel in diesel engines can be solved by minor modifications of current engine and fuel production technology. You have to distinguish between somebody making biodiesel in their back yard from waste vegetable oil vs a well engineered large production complex.

Extrapolating from the numbers on http://www.unh.edu/p2/biodiesel/article_alge.html (141E9 gal/yr to replace all US transportation energy), to replace all global energy, it would take roughly 22x that much: (400 quadrillion BTU / (141E9 gal * 130000 BTU/gal). Land area required would be somewhat larger than Texas, but it could be 100% in non-arable land (e.g, deserts) around the world. It would use essentially existing distribution, storage, and engine technology, unlike other approaches that require total replacment of all those.

I totally support the use of bio-fuels, and it sounds like they could free us of petro, however, it is still a dirty fuel that can't satisfy all of the worlds energy needs. As I said, no mention of aviation, for one. And the demand for water, which can be a large energy liability, also competes directly with the needs of people; thus biofuels put food into competition with energy on two fronts - for airable land, and for water, and of these, water being the most critical.

 

[Ivan Seeking]

The best current deal on new 50 watt solar panels is about $4.25 a watt--$212 for a 50 watt panel, in quantity.

http://www.otherpower.com/otherpower_solar.html

So right now, with a demand of 2.7E16 Watt-Hrs, it would cost about $10¹³ to replace US oil energy with off-the-shelf, solar panel energy. Not very practical right now.

One positive note: Given solutions such as $300,000,000,000 worth of algae farms, consider Iraq. We have spent $200,000,000,000 in just a few years. So given a clear and effective plan, large scale change could happen very quickly.

 

[Ivan Seeking]

If we assume that just the barebones wings from an Airbus 380 could be purchased at 5% of the total sales price of the vehicle, for 300 Billion, we could purchase 23,000 sets wings.

Again, sorry for all of the late edits but I'm just playing with the numbers here. Interestingly, if we built 10,000, 10 MW FEG platforms, 10¹² watts and 200 per state, the basic equipment costs would probably come in on the order of $300 billion, and this would produce about the same energy per year as is contained in all US oil - with an average demand of about 3X10¹² watts. Obviously these are just seat of the pants calculations, but the estimates seem reasonable.

whoops, off by ten, that would be 10¹¹ watts. So we need ten times as many for the same power.

 

[Ivan Seeking]

The website mentions using 20 MW FEGs without any analysis of whether that's actually possible. The largest terrestrial wind turbine ever made is the REPower 5M, a 5 megawatt unit with a rotor diameter of 126 meters. It weighs 120 tons. Each rotor blade weighs 18 tons. You'd need something maybe TWICE that size -- flying overhead -- for a single 20 MW FEG (accounting for higher rotor disc areal efficiency

I was looking over the wind data for this issue. For a 126 meter diameter [worth of] rotor at 35,000 feet, based on avg wind conditions at about 45 degree latitutde, we have an average of about 37 MW of wind power available. This assumes about 3KW per sq meter as is indicated in the data plots.

From what I am seeing, state of the art designs can run close to 50% efficient. So instead of expecting 5MW, for that amount of rotor swept area we might do as well as 15MW, correct?

 

[joema]

...it would take less acreage for solar cells to produce the same amount of power as biofuels. However, we don't really know the well-to-wheels efficiency of either approach, so it is possible that neither would yield a net positive when all is said and done. Since in both cases we are talking about future technlogies, large scale production of products like paint-on solar cells [currently in development] could prove viable and superior to biofuels as solar energy converters.

We know the approx. biodiesel via algae real estate required: I calculated it above, and it's based on real data, not paper hypothesis.

Solar PV real estate required is roughly the same size, but that area must be filled with solar arrays, not algae ponds. Solar PV acreage calculation:

Average solar insolation in US southwest: 5000 watt-hrs/m^2/day, or 1.8E6 watt-hrs/m^2/year
Overall PV efficiency: 10% (must include DC/AC conversion losses, cell aging, etc). Solar cell efficiency degrades at about 2% per year, so after 20 years, output has declined by 1/2.
Average actual useable annual solar PV energy output: 186,000 watt hrs per year per square meter.

Hydrogen electrolysis is about 70% efficient, transport about 90% efficient, vehicle/depot storage about 80% efficient, fuel cells about 70% efficient, electric motors about 92% efficient, for total end-to-end efficiency of about 32%. That's roughly the same end-to-end efficiency as biodiesel.

Solar PV acreage required for world energy demand (1.18E17 watt hrs/yr):

1.18E17 watt hrs/yr / 186,000 watt hrs/yr/m^2 = 634 billion square meters, or 245,000 square miles (roughly the size of Texas).

So the acreage requirements seem roughly the same, but solar/hydrogen/fuel cells require total replacement of the distribution infrastructure and totally new vehicle technology. That also assumes you can economically make solar PV arrays to cover 634 billion square meters, plus replace them about every 20-30 years.

A 10 MW FEG at 80% capacity factor produces about 70E9 watt hrs per year. The number of 10 MW FEGs required to handle world energy is:

1.18E17 watt hrs per yr / 70E9 watt hrs per FEG = 1.7 million 10 MW FEGs.

 

[Ivan Seeking]

The numbers that you cite are based on ideal conditions and lab testing conditions and not on data from real algae farms. We don't know how this will scale up. So my objection is not that we shouldn't try it, my objection is that it is still theoretical and may not prove as viable as it appears. 80 watts per sq meter does not leave a lot of room for the practical energy needs of irrigation, harvesting, processing, ect. And aside from price, solar cells have the same problem. We don't know the true energy investment in a solar panel. But, as I have been saying for thirty years, the technology coming along looks promising.

As for comparing FEGs to algae farms, we have no idea how large FEGs could be built or how many it would take, or the price, or the total efficiency, so it is premature to state the performance or costs of one approach over the other. But just playing with wild guesses of 30 million per 10MW unit, with as much in maintenance costs over a twenty year lifespan, I come up with 4 cents per KW-HR at 45 degrees latitude, and 35,000 feet, which is highly competitive now. And in the end, the price per kw-hr is the key test.

 

[Ivan Seeking]

Oh yes, and based on the weight estimates, given the increased power per unit rotor area, it would appear that something on the order to the Airbus 380 wings could lift enough equipment to produce 30 MW avg power, in ideal locations. So if we are going to shoot from the hip, you need to divide by three - 560,000 FEGs.

And I would bet a year's wages that we could do much better given a serious effort.

 

[Ivan Seeking]

So the acreage requirements seem roughly the same, but solar/hydrogen/fuel cells require total replacement of the distribution infrastructure and totally new vehicle technology.

That technology and distribution is already well under way as, people have been working on it for decades, and the major auto manufacturers are aleady heavily invested. Also, as mentioned, we can select at will to burn either H2 or petro in existing engines, which seems like an excellent solution to supply transition issues. Finally, the exhaust is almost entirely pure water, so this would make a huge and immediate difference in pollution levels in the cities, which would in turn have a large pay off in reduced health care costs.

 

[Ivan Seeking]

Consider for example, Ontario, which happens to have easily found estimates.

In the year 2000, Ontario is forecast to suffer in the order of 1,900 premature deaths, 9,800 hospital admissions, 13,000 emergency room visits and 46 million illnesses as a result of air pollution. (Forecasts of doctor’s office visits are not included due to the absence of supporting epidemiological studies.) If air quality conditions remain constant for the next 20 years (i.e., to the year 2020), these illnesses and deaths will increase substantially. This increase is due to an expanding population as well as an aging population which is at higher risk to air pollution impacts.

These health impacts involve about $10 billion in annual economic damages. Loss of life and pain and suffering account for about $4.1 and $4.8 billion of this total. Annual health care costs of air pollution are in the order of $600 million; lost productivity accounts for an additional $560 million in annual damages. These economic damages are expected to increase substantially over the next 20 years.

The ASAP will reduce health and economic damages by about 11% overall, compared to the status quo. The residual damages (i.e., those damages expected even with full implementation of the ASAP) in 2015 are substantial and in total are forecast to be in the order of $10.7 billion annually.

http://www.oma.org/phealth/smogexec.htm

This is for a population of 11.4 million.

These become real dollars in a hydrogen economy.

 

[Ivan Seeking]

While playing around a little, one thing that I am noticing about the idea of FEGs is that it becomes difficult to build a flying wing and wind turbine that won't interfere with each other. One tends to steal wind energy from the other in almost any configuration.

That is, without the use of more structure.

 

[Ivan Seeking]

The Magenn Power Air Rotor System (MARS) is an innovative lighter-than-air tethered device that rotates about a horizontal axis in response to wind, efficiently generating clean renewable electrical energy at a lower cost than all competing systems.

Electrical power generated at the floating Air Rotor is transferred down the tether to ground level equipment. Depending on size of the Air Rotor, power is sent to users ranging from campers to large power grids. Helium (an inert non-flammable lighter-than-air gas) sustains the Air Rotor which ascends to an altitude for best winds. No towers or heavy foundations are necessary and sizes range from small "backpack" models to large megawatt generating devices.

Due to design simplicity, low capital & operating costs, and higher efficiency, MARS represents a paradigm shift from the standard wind turbines of today. Magenn Power will start a projected billion-dollar business through sales and licensing of its wind generators. Our first step is the development of a 4 KW prototype which the company will demonstrate in the later part of 2006.

http://www.magenn.com/

I thought of something like this but have no idea how pracital a helium based system could be. I guess helium is cheap though...

One other concern with the flying wing concept: I keep trying to imagine how one might launch and land it. What would be really slick is if the turbines could be powered to enable lift, and then switched from a motor to gen mode for power generation. But obviously this would be no small engineering challenge. And it seems that the wing has to be backwards as compared to its operational mode for this to be easy... Fun problem.

 

[joema]

The numbers that you cite are based on ideal conditions and lab testing conditions and not on data from real algae farms. We don't know how this will scale up...

No, it's based on an actual 1/2 acre pilot plant, not lab testing. See http://www.unh.edu/p2/biodiesel/pdf/algae_salton_sea.pdf (PDF).

In addition there is extensive well funded research on biodiesel production from algae: http://www.nrel.gov/docs/legosti/fy98/24190.pdf (warning: large PDF)

For solar PV production there is plenty of actual data from current large installations. One of the world's largest solar PV arrays is the Springerville Generating Station Solar System (SGSSS) in northeastern Arizona. It covers 44 acres (178,000 m^2), and produces about 7.6 gigawatt hrs per year (7.6E9 watt hrs/yr). That's an average of 42,696 watt hrs per m^2 per year. http://www.greenwatts.com/pages/solaroutput.asp

Scaling that up to provide world energy need would require:

(1.18E17 watt hrs/yr / 42,696 watt hrs/yr/m^2) = 2.76 trillion square meters, or over 1 million square miles -- over 1/3 the continental U.S.

So we have good numbers from solar pilot plants and at least some numbers for an algae pilot plant, but nothing for FEGs except back-of-the-envelope calculations.

As always the actual achievable numbers are significantly less than theoretical numbers, which illustrates the need for caution when comparing energy sources for which we have pilot plant data (solar, wind, biodiesel/algae) to those we have no significant test data for (FEGs, etc).

That doesn't mean FEGs are without merit, or should not be further investigated. But at this point, any output/cost characteristics are very speculative. As the above solar PV plant indicates real-world production numbers are generally much less than theoretical calculations.

As for comparing FEGs to algae farms, we have no idea how large FEGs could be built or how many it would take, or the price, or the total efficiency, so it is premature to state the performance or costs of one approach over the other.

As stated above pilot plant algae farms have been built, unlike FEGs. With algae farms we have some basis for extrapolating larger plant costs and efficiencies. With FEGs we do not.

But just playing with wild guesses of 30 million per 10MW unit...

As stated previously it would take about 1.7 million 10 MW FEGs to provide world energy need. At $30 million each, that's 51 trillion dollars, just for construction costs.

 

[joema]

That technology and distribution is already well under way as, people have been working on it for decades, and the major auto manufacturers are already heavily invested...

Technology and capacity for global hydrogen distribution is essentially nonexistent. There are about 200,000 gasoline filling stations in the US. You'd have to convert most or many of those to hydrogen. That is a titanic undertaking requiring decades.

There is no infrastructure for transporting the gigantic volumes of hydrogen needed just for transportation -- not to mention non-transportation use. Liquid hydrogen has 27% of the energy per gallon as gasoline. Therefore it would take nearly 4x the number of tanker trucks just to move the same energy content.

Whether fuel cells or hydrogen internal combustion engines are used, if you can't get the fuel to the end user, it's irrelevant.

As stated previously, you must distinguish between a technology working on a small scale vs an industrial scale. Some small scale technologies can be readily ramped up. Others cannot.

Solar/wind/Hydrogen/fuel cells or hydrogen internal combustion works fine on a small scale. But that's irrelevant if it can't economically be scaled upward to meet global need within a useful time frame.

There are two discrete energy problems:

(1) Transportation -- roughly 25% of total energy (primarily petroleum),which will exhaust conventional sources within a couple of decades.

(2) Utility/industrial/residential -- roughly 75% of total energy consumption (coal, nuclear, hydro) which will last at least at least 100 years.

For any energy solution, you must be precise about which of these you're addressing, over what time frame, and why.

The transportation energy problem is very difficult due to the limited time frame. Fortunately there are alternative petroleum sources (tar sands, oil shale) that will likely be tapped, albeit at significant environmental cost. Without those it would be apocalyptic when conventional oil runs out.

 

[joema]

...Finally, the exhaust is almost entirely pure water, so this would make a huge and immediate difference in pollution levels in the cities, which would in turn have a large pay off in reduced health care costs.

Existing new internal combustion (IC) engines are so clean the conventional pollution problem is mostly solved. The pollution output of SULEV (Super Ultra Low Emissions Vehicles) is incredibly low, and it's possible to get further reductions with incremental improvements to existing technology. You don't need alternative engine technology because of conventional pollution. You need it because the petroleum supply is fast running out.

The cause of health threatening IC emissions is two fold: (1) Industrial non-automotive emissions, and (2) Older vehicles.

In fact most automotive emissions come from a small fraction of the total vehicle fleet -- the older cars. That's because newer cars are so incredibly clean the few older cars contribute much of the pollution.

You could tremendously reduce total conventional automotive emissions almost overnight by just getting rid of the oldest 20% of the vehicle fleet.

 

[russ_watters]

Dunno if I missed some discussion on this, but...

While playing around a little, one thing that I am noticing about the idea of FEGs is that it becomes difficult to build a flying wing and wind turbine that won't interfere with each other. One tends to steal wind energy from the other in almost any configuration.

That is, without the use of more structure.

Because of that, I don't see why you would want to have a wing at all. If you're flying it like a kite, part of the turbine's drag is the lift you need to keep it aloft.

Are you concerned about not having the turbine perpendicular to the wind? I wouldn't be, because as you said, a turbine and wing would steal from each other and the net effect would be the same as not having the wing (actually, probably a little worse with the wing) .

 

[Ivan Seeking]

No, it's based on an actual 1/2 acre pilot plant, not lab testing. See http://www.unh.edu/p2/biodiesel/pdf/algae_salton_sea.pdf (PDF).

In addition there is extensive well funded research on biodiesel production from algae: http://www.nrel.gov/docs/legosti/fy98/24190.pdf (warning: large PDF)

That's all great but a half acre is still a lab. We haven't even begun to get into real, practical problems like mold, parasites, disease, infestations, etc. There is no way that this will be problem free. And I seriously doubt that a complete analysis of all hidden energy costs is considered. My only real objection here is that this is new and it will have problems. And it could have serious problems. We are not ready to cover Texas with algae.

For solar PV production there is plenty of actual data from current large installations.

(1.18E17 watt hrs/yr / 42,696 watt hrs/yr/m^2) = 2.76 trillion square meters, or over 1 million square miles -- over 1/3 the continental U.S.

To be fair, you are comparing untested technology to what is probably twenty year old technology. The cutting edge of PV is probably ten times better. But even so, the average Watts per sq meter was a real surprise.

 

[Ivan Seeking]

As stated previously it would take about 1.7 million 10 MW FEGs to provide world energy need. At $30 million each, that's 51 trillion dollars, just for construction costs.

Well, we can guess at numbers all day, but you are ignoring the factor of three for the increased wind velocity, for a given weight to power expectation at high atltudes. However, I'm not really trying to pit FEGs against algae farms as I am only looking at both ideas for the first time. But I don't see it as being cut and dried as you seem to.

I think we should proceed immediately with further development of biofuels from algae, by all means! As I think Cliff mentioned, even if 20% of the petro was replaced with bio fuels, that would be huge. We could go for all existing diesel sales, for starters.

However, just to consider the FEG idea on its own merit, it might be cost competitive immediately in which case it won't really matter how much it cost. If I can double my money on an FEG I'll buy one myself. But I think we basically agree: It is very speculative as far as costs, capacity, etc. Also, it seems that the FEG idea has been around for quite some time and tends to come and go in the literature, but it also seems to be an idea that is ripe, or at least could be given modern tether, wing [materials], turbine, and transmission technology. I think it is definitely doable by some means and really it becomes a matter of how and at what cost; which is what caught my interest in the first place. But, the real beauty of it is, at least in part, that we could fly one just about anywhere given ten miles or so of rural, ocean, or lake as a buffer from population centers. And as soon as it flies it becomes a part of the existing electrical distribution system - no plantations to harvest, processing, or distribution of fuel, no miles of solar panels to maintain, no waiting - just hook up to any major transmission line. That is valuable technology.

 

[joema]

Well, we can guess at numbers all day, but you are ignoring the factor of three for the increased wind velocity, for a given weight to power expectation at high atltudes..

I didn't totally ignore it -- I factored in a factor of two improvement.

I agree any reasonable alternative energy source should be closely examined. However unless the technology is economically scalable to a gigantic industrial level within a meaningful timeframe, it will make no real difference. E.g, does hydrogen via solar or wind work? yes. Can you scale it to provide a large % of transportation energy consumption within two decades. No -- totally impossible. If Ralph Nader was absolute dictator over the entire globe it wouldn't be possible.

There are two discrete energy problems:

(1) Transportation energy (primarily currently petroleum). This will be significantly exhausted within 20 yrs, and possibly peak oil will hit within 10 yrs, if not sooner. This is by far the most time critical need. Working on a utility energy solution won't address this more immediate problem.

(2) Utility/industrial/residential energy (power, heating, etc). This comprises about 75% of all energy consumption, but there's sufficient conventional sources for at least 100 years. It may not be clean or desirable, but at least the lights won't go out. Much sooner transportation could grind to a stop, or oil prices disrupt world economy beyond anything yet seen.

If FEGs can be made to work -- fine, use them. Unfortunately too little is known about the viability, especially if used on a huge scale.

I mentioned biodiesel from algae mainly because it's one of the few solutions that (1) uses the existing distribution infrastructure (2) uses existing vehicle/engine technology, (3) solves most of the emission problems, inc'l CO2, and (4) fits within available real estate. Yes there are still unknowns that could preclude its use, but those are UNKNOWNS. By contrast most other alternative technologies have KNOWN problems (even at this early stage) limiting their huge industrial deployment.

We often hear of promising new energy sources. However it's important to separate what's technically feasible on a small scale, vs what can be deployed on the required vast industrial scale. We can't say "somebody will figure that part out" -- that IS a limiting factor even more than the technology itself.

 

[Ivan Seeking]

Dunno if I missed some discussion on this, but...
Because of that, I don't see why you would want to have a wing at all. If you're flying it like a kite, part of the turbine's drag is the lift you need to keep it aloft.

Are you concerned about not having the turbine perpendicular to the wind? I wouldn't be, because as you said, a turbine and wing would steal from each other and the net effect would be the same as not having the wing (actually, probably a little worse with the wing) .

In principle it seems to make sense to avoid [design around] sacrificing power for lift.

 

[Ivan Seeking]

I didn't totally ignore it -- I factored in a factor of two improvement.

Well, it turns out that 120 tons plus the generator and wing is not a lot of weight on the scale that we are discussing, and we haven't even tried to reduce weight in a proper turbine or generator design made specifically for this application. So it seems that double that number is more likely where we start hitting limits. And we have only been talking about a tinker toy approach - a worst case - as a basis. It is hardly fair to compare this to something that has a few years of actual testing.

As for the rest, I am thinking beyond just the US transportation problem. There is a real movement towards nuclear power again, and this has nothing to do with transportation energy.

 

[Ivan Seeking]

Btw, we might also run bio-diesel in fuel cells. In fact Bush has already pushed for the idea of petroleum powered fuel cells.

So this could help to make the transition to electric cars while still solving the immediate need for oil.

Oh yes, traditionally, diesel cars really suck, which is why we drive gasoline powered cars.

 

[joema]

Btw, we might also run bio-diesel in fuel cells. In fact Bush has already pushed for the idea of petroleum powered fuel cells.

So this could help to make the transition to electric cars while still solving the immediate need for oil.

Oh yes, traditionally, diesel cars really suck, which is why we drive gasoline powered cars.

That may be true historically, but newer diesels (e.g. VW PDI) are almost like gasoline engines -- very little of the old characteristics.

Re "dirty", newer diesels burning low sulfur fuel can be very clean. Biodiesel largely solves the CO2 problem -- it mostly only emits what the plants absorbed during growth.

While current SULEV and PZEV gasoline engines have reduced traditional emissions (SOx, NOx, etc) to incredibly low levels, you can't greatly reduce CO2 emissions from those. CO2 is the natural by-product of perfect, clean hydrocarbon combustion. That's where biodiesel has a big advantage, plus it's manufactured vs draining a non-renewable resource.

If biodiesel can work in fuel cells that's great, but new technology diesels are already approaching current real world fuel cell overall efficiency, and they're here today and can be immediately manufactured in vast quantities.

 

[Ivan Seeking]

Well, I must admit that this all sounds very promising. Do you have any idea what the cost of these new engines will be as compared to traditional diesel engines? Also, HP to weight ratios, lifespan, maintenance, etc, do we know how they compare in these areas yet?

Would US cities smell like french fries? I know that the veggy oil crowd drive cars that smell like fries. Hydrogen would leave us with cities that smell like clean laundry. In fact it is officially dubbed as the "clean laundry smell".

There is another huge advantage to going diesel over gasoline, I think... IIRC, diesel is much less volatile than gasoline. I don't recall the numbers, but simply filling the tank is one of the larger sources of air pollution. Many states require the vapor return line on the dispensing nozzle, but I see people defeat these all the time.

 

[joema]

Well, I must admit that this all sounds very promising. Do you have any idea what the cost of these new engines will be as compared to traditional diesel engines? Also, HP to weight ratios, lifespan, maintenance, etc, do we know how they compare in these areas yet?

The new PD diesels are already in production starting with the 2004 model year for VW and Audi. HP, hp-to-weight, etc. are generally equal or better. Lifespan and maintenance are probably equal or better than older diesels, but time will tell.

http://www.canadiandriver.com/articles/rr/04jettatdi.htm

The VW PD diesel is just one example of new-tech refinements. Other manufacturers are working on similar technology. Even cleaner, more efficient diesels than these are readily attainable.

There's a tendency to discount existing engine technology in favor of new concepts -- a few decades ago piston engines were thought obsolete and soon to be replaced by Wankels, turbines, flywheels, etc. However continuing technical refinement has produced piston engines with very low emissions, and very good power, drivability and reliability.

Would US cities smell like french fries? I know that the veggy oil crowd drive cars that smell like fries.

I don't really know how it would smell. Although biodiesel from waste vegetable oil gets a lot of press, it can't have a major influence on the energy situation -- there's just not enough of it.

...I don't recall the numbers, but simply filling the tank is one of the larger sources of air pollution. Many states require the vapor return line on the dispensing nozzle, but I see people defeat these all the time.

Yes, in fact a key difference between SULEV (Super Ultra Low Emissions Vehicles) and PZEV (Partial Zero Emissions Vehicles) is the PZEVs have lower evaporative emissions. When tailpipe emissions get this clean, the evaporative emission component becomes a greater factor.

 

[Ivan Seeking]

Now are you going to tell me that we have diesel lawn mowers coming?

Turns out that lawn mowers and weed eaters are huge offenders in the cities; so much so that some cities have begun to ban gasoline powered yard equipment.

 

[Cliff_J]

Until the US finishes its switch from diesel with the highest sulfur content to the lowest, a clean diesel is going to have the extra premium added to it. And the price has yet to really stabilize on regular diesel fuel post-katrina, so the oil companies may even step this up higher if the refining costs are higher to remove the sulfur.

The veggie oil crowd fail to mention that the unprocessed oil has a lot of containiments in it that are harmful for the components needed to make the injection system in a diesel engine work. That's one of the big reasons to run it through the transestification process into biodiesel, is to remove the glycerine that would leave behind deposits in the engine and add particulate matter in the exhaust.

In the 80s GM took their 5.7L gas engine and converted it to run on diesel. It was a pretty good seller in the heartland because farmers could purchase diesel fuel without paying road tax (for farm use and as a business expense) and drive their vehicles with it (practice has since been regulated). Here was an educated customer base, they use diesel in their tractors, yet GM ended up with a bad reputation for the motor as it aged. It would commonly break a head bolt or two and the cause was excess moisture in the fuel system that would cause an injection timing issue. Similar problems exist with biodiesel since its more prone to moisture.

To add insult to injury, the diesel fuel stations, used to only filling up trucks that have oversized fuel filtration systems, vary in quality. I've read some anecdotes of VW drivers who complain about the lack of refueling stations and having to pull their little car in next to giant trucks, and then also having to take them in for filter changes after a bad fill-up on a trip.

Even the new pickup truck diesels from GM/Ford have stepped up in usability, they are very quiet and aside from the RPM range drive similar to a gasoline engine. However, they are a $5000 premium over the gasoline engine, and how much of that is profit or additional cost is a big question. It seems in Europe the small 4cyl fuel-miser diesel is produced in large enough quantities that its price is comparable to the larger gas engine with performance of the smaller gas engine. It could happen stateside, but as joema pointed out the distribution infrastructure is going to be a problem.

And repeating my second point in this post, diesel's premium price would require a large shift in mileage to offset its higher cost for the economic viability to work out. Otherwise the US is stuck in a chicken-egg problem and political whims aren't going to change that.

 

[Ivan Seeking]

Regarding the solar farm linked earlier, I come up with an average peak output of just less than 20 watts per sq meter.

This off-the-shelf panel
http://www.kyocerasolar.com/pdf/specsheets/kc125g.pdf
is 0.9 sq meters and is rated as having a 125 watt peak output.

 

[joema]

Regarding the solar farm linked earlier, I come up with an average peak output of just less than 20 watts per sq meter.

This off-the-shelf panel
http://www.kyocerasolar.com/pdf/specsheets/kc125g.pdf
is 0.9 sq meters and is rated as having a 125 watt peak output.

That panel is crystaline, which works for small applications but can't be scaled to thousands of square miles -- the manufacturing process is similar to a semiconductor wafer. You'd need to use amorphous or some totally new technology capable of industrial scale production, which are typically much less efficient. Amorphous cells are about 6% efficient.

You also can't count peak power, but only average power (solar insolation) based on the climate. In southern Arizona, you have about 6000 watt hrs per square meter per day: http://www.windsun.com/Solar_Basics/Solar_maps.htm#Map1

Even your above crystaline solar panel won't produce 15% efficiency unless it's brand new and the sun is straight overhead. Unlike the AC output of a conventional power plant, solar cell output must be buffered or converted to AC, which costs more efficiency.

All things considered, you're lucky to get over 10% efficiency using crystaline cells, and probably 4% efficiency from amorphous cells.

10% efficiency is about 600 watt hrs per square meter per day in southern Arizona, and 4% is is about 240 watt hrs per square meter per day. In any other climate output will be much lower.

On top of the above losses, if you convert it to hydrogen via water electrolysis, you take another 50% hit (at least) in conversion and transport losses.

 

[Ivan Seeking]

You also can't count peak power, but only average power (solar insolation) based on the climate. In southern Arizona, you have about 6000 watt hrs per square meter per day: http://www.windsun.com/Solar_Basics/Solar_maps.htm#Map1

Not true. If I can show a panel with six times the peak power as compared to the peak power for the panels used, then we would expect a much higher average total power value accordingly. I was comparing peak power to peak power.

Even your above crystaline solar panel won't produce 15% efficiency unless it's brand new and the sun is straight overhead. Unlike the AC output of a conventional power plant, solar cell output must be buffered or converted to AC, which costs more efficiency.

Obviously. You seem to be going out of your way to shoot down a perfectly fair comparison. This was just one example of the improvements made in solar technology. And we haven't even looked at the truly new technology coming such as paint-on solar panels.

 

[Ivan Seeking]

Modern switching technology [power transformation] runs as high as ninety-five percent efficient.

 

[turbo]

Here's a page of links that might keep you busy for a while.

http://peswiki.com/index.php/Directory:Solar_Hydrogen

 

[joema]

Regarding the solar farm linked earlier, I come up with an average peak output of just less than 20 watts per sq meter.

This off-the-shelf panel
http://www.kyocerasolar.com/pdf/specsheets/kc125g.pdf
is 0.9 sq meters and is rated as having a 125 watt peak output.

...If I can show a panel with six times the peak power as compared to the peak power for the panels used, then we would expect a much higher average total power value accordingly. I was comparing peak power to peak power.

Your above two statements illustrate the difference between a real world output figure and a laboratory figure. A small crystalline solar array can be 15% efficient (if new). However that's meaningless since you CANNOT manufacture hundreds of square miles of crystalline semiconductors. It's physically impossible, and will always remain so because of how they're made.

To cover hundreds of square miles you must use much lower efficiency technology such as amorphous cells, or even lower efficiency paint-on cells (assuming it's ever debugged sufficiently for mass deployment).

Re peak power, what counts is the actual delivered power over a period of time. That in turn depends on climate, location, cell technology, cell aging characteristics, etc.

You seem to be going out of your way to shoot down a perfectly fair comparison. This was just one example of the improvements made in solar technology...

As stated above, it's not an illustration of solar technology improvement. The large solar farm has lower areal efficiency NOT because the technology was less advanced -- it's because you MUST use lower efficiency technology to cover large areas. You cannot cover a large area with high efficiency crystalline cells -- they are manufactured in semiconductor plants like integrated circuits are.

 

[Ivan Seeking]

I had a talk with a thirty year or so commercial aviation insider - with a world class company - and the idea of a flying wing was well received.

Hey buddy, that's a lot of wings!

 

[Ivan Seeking]

joema, if you're still around, I'm convinced.

Biodiesel, and bio from algae seem to offer a practical solutions to our energy demand today. Current petro prices makes it price competitive, which seems to have been the biggest issue. When it costs a buck or two more per gallon than regular diesel, forget it. But now I have seen it selling cheaper than regular diesel; at the pump, and right around here. Also, it looks like diesel hybrids are ready to market in the US. This is exciting stuff!

Prices for crude may drop for a time, but the demand from India and China for oil can only mean one thing.

 

[Ivan Seeking]

One thing that I don't like [in the long run anyway] is the application of photobioreactors for biodiesel production to industry, to reduce CO2 emissions. This only delays the emissions. It does reduce CO2 emission to the extent that it replaces fossil fuel usage in autos, but if autos are already using alternative fuels, it gets industry off the hook while still allowing the emissions though through a more convoluted path. Instead, ideally, carbon from industry [not produced by biofuel usage] should be trapped for long term storage. Maybe algae bioreactors can be used to mediate this process?

For example, does anyone know if plant oils can be used to make plastics?

edit: photobioreactor appears to be the proper name

 

[Ivan Seeking]

By chance, in the news...

AUDI MAKES HISTORY AS DIESEL-POWERED R10 TDI WINS MOBIL 1 TWELVE HOURS OF SEBRING

Audi is the first diesel-powered car to win a race in the American Le Mans Series.

Sebring, Fla. - Audi Sport North America made history Saturday as the diesel-powered Audi R10 TDI of Tom Kristensen, Allan McNish and Rinaldo Capello won the Mobil 1 Twelve Hours of Sebring. The new prototype is the first diesel car in the world to win a major sports car race. [continued]

http://www.americanlemans.com/News/Article.aspx?ID=1872

The guy who told me about it still hadn't stopped laughing in disbelief.

 

[Astronuc]

Solar power energizing rural China
http://marketplace.publicradio.org/shows/2006/06/19/PM200606195.html

With 20 million people waiting to get on the electrical grid in China, officials in Beijing have launched a campaign to make sure the newest energy consumers will use renewable sources instead. Rob Schmitz reports.

KAI RYSSDAL: Coal is the energy source of choice in China. A billion and a half tons of it were burned there last year to generate electricity. That's three times more than in the U.S., India, and Russia combined. There are about 120 million people in China living off the power grid. So Beijing is trying to get new electricity consumers to use renewable sources. From the Marketplace Sustainability Desk, Rob Schmitz reports.

-----------------------------------------------------------------------
ROB SCHMITZ: A sheep, a yurt, a pasture, and a forest. That once summed up Gulinar Sitkan's world here in Sorbastow, a tiny village in the remote mountains of northwestern China, near the border with Kazakhstan. Last year, her world suddenly expanded.

Through a gauze of static interference, Sitkan now sees important-looking officials shaking hands. Soldiers in a foreign war. A beautiful woman holding a soft drink can to her face. The images on her new television change almost too quickly to take it all in, and they're much more stimulating than watching her sheep.

GULINAR SITKAN [voice of interpreter]: My favorite program is the international news, because I can find out what's happening now. Before, it would take months for us to find out about news.​

Sitkan is one of the many Ethnic Kazakhs in this area who, up to a year ago, didn't have electricity. The Chinese government has provided her and hundreds of thousands of others with solar panels.

This is part of China's plan to use more renewable energy. By 2020, China plans to get 15 percent of its electricity from renewable sources. That'll add up to 120,000 megawatts, more than two times the amount of energy the state of California generates.

Douglas Ogden is vice president of the San Francisco-based Energy Foundation. He's working with Chinese officials to help them fulfill that promise.

DOUGLAS OGDEN: You know, you look around globally, there isn't another country that has set that degree of ambitious renewable energy target.​

Gulinar Sitkan adds wood to her potbelly stove. The pink scarf she wears around her head blends in with the bright red carpets that line the walls of this tiny log cabin. A rooftop solar panel provides enough power for her small television and a couple of light bulbs.

The panel was designed and supplied by one of the world's giant oil companies. You heard right. An oil company. Specifically, Shell Oil's subsidiary, Shell Solar, has supplied 40,000 of these panels to ethnic minorities throughout China's Xinjiang province as part of a project that's funded by the Dutch and Chinese governments. Shell Solar's Bo Xiao Yuan says the portability of the panels is ideal for the ethnic minorities who live in China's most remote regions.

BO XIAO YUAN: In these areas, for nomad, they keep moving all year round, so the grid power cannot be available everywhere. It's too expensive.​

After government subsidies, nomads in this area can buy a portable solar panel for around 60 US dollars. That's equal to about a tenth of what a typical nomad here makes from selling sheep's wool and meat in a year.

In a cabin in the next valley over, newlyweds Kowante and Sandokash Rahmat have finished up a day of shearing sheep. Kowante takes his dombra, a Kazakh guitar, from where it hangs on the wall, and unwinds with a song.

It's a traditional Kazakh song about two lovers who meet near an alpine lake. Kowante and Sandokash have a solar panel, too. It was a wedding present from their parents. The first appliance they bought was a tape player, which is loaded with the newest Kazakh pop songs.

They're expecting their first child this summer. Not only will this child know the latest Kazakh hits, but he or she might have a television, and, says Kowante, a computer, too. And with all of this, access to a world they could have only imagined a year ago.

In Sarbastow, northwestern China, I'm Rob Schmitz for Marketplace.

http://www.efchina.org/home.cfm

In March 1999, after a series of meetings and consultations with scientists, policy-makers, business leaders, and analysts in China and the United States, the staff and boards of The David and Lucile Packard Foundation and The Energy Foundation launched the China Sustainable Energy Program. The William and Flora Hewlett Foundation joined as a funding partner in 2002.

The China Sustainable Energy Program (CSEP) supports China's policy efforts to increase energy efficiency and renewable energy. The program emphasizes both national policy and regional implementation. The program strives to build capacity in China to analyze energy savings and renewable energy opportunities, and to develop policies to capture those opportunities. The program helps Chinese agencies, experts, and entrepreneurs solve energy challenges for themselves. At the request of Chinese non-governmental organizations (NGOs), the program supports capacity building and technology policy transfer through linking Chinese experts with "best practices" expertise from around the world. When it determines there is an unmet need in the field, the program may convene workshops, commission papers, or take other direct initiatives, in addition to its primary role as a grant-maker.

 

[Astronuc]

Interesting article from Purdue Engineering -

The Energy Challenge for Our Generation’s Engineers
https://engineering.purdue.edu/Impact/Energy/

Modern civilization has coasted on fossil fuels, but Earth's supply will peak—then decline. We need a sustainable energy future. Purdue Engineering with support from its partners is taking solving this predicament to heart.

-----------------------------------------------------------------
Somewhat related:

Purdue part of new $21 million fluid power energy research center
http://news.uns.purdue.edu/html3month/2006/060519.Ivantys.ERC.html

WEST LAFAYETTE, Ind. — Discovering ways to reduce fuel consumption, developing devices for people with mobility impairments and designing state-of-the-art rescue robots are just three of the goals of a new multimillion-dollar research center involving the Discovery Park Energy Center, Department of Agricultural and Biological Engineering and School of Mechanical Engineering at Purdue University.

The National Science Foundation announced a $15 million, five-year grant to support the new Engineering Research Center for Compact and Efficient Fluid Power. Industry partners will augment the funding with $3 million, and seven universities involved in the center will contribute an additional $3 million. The center will be based at the University of Minnesota Twin Cities campus, and Purdue will house one of the center's research labs in its MAHA Fluid Power Laboratory.

"This center will advance fundamental knowledge, providing a platform for technology that will spawn new industries," said Lynn Preston, leader of the Engineering Research Centers Program at NSF. "We are impressed with the ambitious goals of the center for research and education and the strong partnership with industry."

Fluid power is a $33 billion industry worldwide. Industry areas include aerospace, agriculture, construction, health care, manufacturing, mining and transportation. Fluid-power technology encompasses most applications that use liquids or gases to transmit power in the form of pressurized fluid. The complexity of these systems ranges from a simple hydraulic jack used to lift a car when replacing a tire to sophisticated airplane flight control actuators that rely on high-pressure hydraulic systems.

 

[Astronuc]

Let's not forget Russ's thread - YOU!: Fix the US Energy Crisis

https://www.physicsforums.com/showthread.php?t=42564

It probably should be stickied as should this thread.

 

[Ivan Seeking]

New Zealand Company Produces World’s First Sample Of Bio-Diesel From Algae

New Zealand-based Aquaflow Bionomic Corporation announced today that it had produced its first sample of home-grown bio-diesel fuel with algae sourced from local sewerage ponds.

“We believe this is the world’s first commercial production of bio-diesel from algae outside the laboratory, in ‘wild’ conditions. To date, bio-diesel from algae has only been tested under controlled laboratory conditions with specially selected and grown algae crops,” explains Aquaflow spokesperson Barrie Leay. [continued]

http://www.dieselforecast.com/WireReportDetails.php?wireID=142

 

[Ivan Seeking]

And, a story indirectly related to the FEGs concept:

... Multimax is one of several defense companies pouncing on the military's renewed interest in using high-flying, unmanned, helium-filled balloons -- sometimes tied to the ground with a long rope -- as possible weapons. Lockheed Martin Corp. is developing a blimp that it says will reach an altitude of 65,000 feet, while Raytheon Co. is developing one designed to reach 10,000 feet and be tethered to the ground. Blackwater USA, better known as one of the largest security contractors in Iraq, expects to finish its prototype, which aims to reach an altitude of 5,000 feet to 15,000 feet, in December.[continued]

http://www.washingtonpost.com/wp-dyn/content/article/2006/08/06/AR2006080600499.html

 

[dansydney]

I think there are many viable clean power solutions out there its just a matter of people willing to build and fund the required plants, machines etc. I think its much harder fighting the greed and politics associated with world energy usage than the actual making/finding etc of a clean energy source.

 

[Ivan Seeking]

Last night on a re-broadcast of Scientific American Frontiers, they did a spot on the Algae project at MIT.
http://www.pbs.org/saf/1506/segments/1506-3.htm
http://www.pbs.org/saf/1506/

Note that at the top of the page [under "Hydrogen Hopes"] is the option to watch online.

 

[turbo]

Great link, Ivan! I love it. I have wondered for the past few years if photovoltaic technology would ever allow the production of hydrogen on small (my house and personal vehicles) scales so that we could free ourselves from the petro industry. This gives me some hope. Sure, people in apartments and in the city might have to use commercial retail sources, but what if I could buy or build my own hydrogen generator and supply my own enegy. Right now the only thing that the south-facing side of my roof does is keep out the rain and reflect the Sun's energy. What if it could provide enough energy to keep the house cool in the summer and supplement the heating requirements in the winter?

 

[joema]

...I have wondered for the past few years if photovoltaic technology would ever allow the production of hydrogen on small (my house and personal vehicles) scales so that we could free ourselves from the petro industry...the only thing that the south-facing side of my roof does is keep out the rain and reflect the Sun's energy...

Average solar insolation for much of the US population area is 4-5 kilowatt hrs per square meter per day: http://www.windsun.com/Solar_Basics/Solar_maps.htm

Normally you wouldn't convert to hydrogen for local household use -- that would add considerable conversion loss. You'd just use the electricity directly.

How much solar cell roof area and how many hours would it take to produce enough hydrogen to refuel a fuel cell vehicle with comparable performance to a Honda Accord?

Hydrogen electrolysis is about 70% efficient, vehicle/depot storage about 80% efficient, fuel cells about 70% efficient, electric motors about 92% efficient, for total end-to-end efficiency of about 42%.

A 15-gal tank of gasoline holds 1.86E6 BTUs or 545000 watt hours of energy.

Assume your solar-useful roof collecting area is 20 by 40 feet (74 square meters). Note you can't count the whole roof area, just that portion that receives direct sun.

Your roof receives (74 m^2 * 4500 watt hr / m^2 / day) or 333,000 watt hours per day, on average. At 15% solar cell efficiency, it produces 49,950 watt hours per day. Running it through the hydrogen/fuel cell cycle, the delivered hydrogen energy is 42% of this, or about 21,000 watt hrs per day. So it would take 545000 watt hrs per tank /21000 watt hrs per day or 25 days to fill up your hydrogen car with equivalent energy to a tank of gasoline.

If you live in Yuma, Arizona, you have about a 2x advantage in solar insolation, which lowers the time required to about 12 days.

It appears the solar/hydrogen/fuel cell vehicle refueled by your solar roof panels isn't practical.

I enjoyed the Scientific American Frontiers videos, but such programs never do the above pragmatic math, so constantly leave viewers with unrealistic impressions. Then years go by and people wonder why hydrogen cars aren't here yet. The reason isn't a conspiracy, but the physics work against you, and these items are rarely adequately explained by programs like this.

 

[turbo]

Thank you very much joema for keeping practicality at the forefront.

 

[Ivan Seeking]

Although I agree in principle, not completely. First note that the efficiency of the gasoline engine wasn't considered. The actual energy demand is about 18% of that indicated. Also, this is for a full tank of gasoline, so a few days isn't so bad.

Also, I keep seeing 50% as the practical number for electrolysis efficiency.