Fuels for Tomorrow's Vehicles

It was encouraging to see Nobel Laureate George Olah (chemistry, hydrocarbons) recently point out that a "Methanol Economy" seems more practical than a "Hydrogen Economy" [1]. He notes that in recent years, very efficient methods of dehydrating bio-methanol into bio-ethylene (C₂H₄) and water have been developed. Ethylene, in turn, can be used to efficiently produce all hydrocarbon fuels and products currently obtained from fossil sources. But this is just one of literally dozens of highly promising biofuel avenues that are just beginning to be explored and developed. Bio-diesel, ethanol, bio-gasoline, bio-jet-fuel, and bio-methane can be efficiently and safely produced, stored, and transported within the current infrastructure. Direct Methanol Fuel Cells (DMFC), which convert methanol directly into water and CO₂ while producing electricity, have advanced to the point that they are now beginning to appear in commercial products such as cellular phones, laptop com- puters, and some military equipment. While there will undoubtedly be some economically viable applications for DMFCs and perhaps some for non-mobile hydrogen fuel cells, as shown in Figure 1, economically viable solutions for a number of fuel-cell challenges in automobiles seem highly unlikely within the next half century.

Hydrogen Fuel costs. For the past 40 years, most cities of population over 100,000 in industrialized nations have had dozens of industrial and research users regularly purchasing 14 MPa (2000) psi hydrogen gas in heavy steel cylinders containing about 0.6 kg H₂ per cylinder. The price of this hydrogen has been reasonably stable at about $100/kg (over fifty times the cost of gasoline per unit energy), plus cylinder rental. The current cost of a full tanker truck (15,000 gallons, or 4300 kg) of liquid hydrogen (LH2) in most regions in the U.S. for high-volume customers is about $6/kg [3]. One of the basic assumptions underlying the putative "hydrogen economy" is that the cost of high-pressure hydrogen gas can be reduced to a few dollars per kilogram for the individual consumer even while the price of natural gas rapidly increases over the next 30 years. There are serious problems with this assumption, as discussed in more detail in a separate article [4] and summarized here.

A number of studies have been carried out over the past seven years on the cost of hydrogen, but there are major problems with most of these studies that are not widely appreciated. The four biggest problems with most hydrogen cost projections are:

1. The rate of introduction of hydrogen-fueled vehicles is currently nearly two orders of magnitude lower than was generally expected 4 to 8 years ago [5], and it seems likely to remain at such a depressed rate for at least several more decades [6]. This is largely because the cost of moderate-weight proton exchange membrane fuel cell (PEMFC) stacks are still $3000/kW [7], which is nearly two orders of magnitude higher than was officially expected in the late '90's [8]. Also, their lifetime under road conditions is still 20% that of the diesel engine, and they achieve under 35% efficiency [7] while current diesel engines achieve over 40% efficiency [9].

2. North America is facing natural gas (NG) shortages that will steadily worsen over the coming decades [10]. The U.S. price of NG has increased by a factor of 10 in the past 30 years and nearly a factor of three in the last six years [11]. Its cost seems likely to increase by more than another factor of two (in constant dollars) within 10 years in North America.

3. Small hydrogen-dispensing stations [12] are costing about $600K each, which is ten times more than was initially expected for stations an order of magnitude larger [13] and is thus another error in earlier assumptions of two orders of magnitude.

4. Hydrogen storage costs by all methods (at least for quantities below tens of thousands of kilograms) are two orders of magnitude greater than for liquid hydrocarbon fuels [14]. This is not appreciated in many published studies which have often referenced erroneous earlier works [8, 13].

Other issues which were not well appreciated in earlier studies include (1) the increase in pipeline costs to avoid hydrogen embrittlement failures [15] and (2) the implications of taxes, including the imposition of a fossil-carbon tax or similar disincentive to the use of fuels such as fossil hydrogen which have huge life-cycle green-house-gas emissions.

All of these errors in prior studies have been in the direction to make hydrogen seem more attractive as a fuel. However, it is important to point out that several thorough and generally accu- rate infrastructure studies have been carried out [14, 16]. But even the rather scholarly works are often misused by hydrogen advocates who fail to carefully note their assumptions:

1. NG costs were usually assumed to be $3.5/GJ - compare to today's $5.5/GJ at the well head, $7/GJ at the city gate, and probably $15/GJ at the city gate in 2020.

2. Dispensing stations were often assumed to be filling 300 vehicles each per day about two orders of magnitude more than seems likely for at least 15 years.

3. Often 300,000 hydrogen vehicles were assumed within 100 km of the central station with a total demand of 150 tons/day - three orders of magnitude more vehicles than seems likely for at least another decade.

It has been suggested that the show-stopper issues of FC-stack cost and reliability can be avoided by using hydrogen-fueled internal combustion engines (ICEs). Indeed, such have been demonstrated, but it does not appear that they can achieve efficiencies above 28% [17] - 70% that of the advanced gasoline engine [9]. Moreover, hydrogen ICEs still have all the fuel-cost, fuel-storage, and safety issues of hydrogen FC vehicles [7].

Some studies have concluded mini-reformers (if mass produced) at corner filling stations could produce hydrogen at $3.4-4.3/kg for natural gas priced at $5/GJ [18]; but other data and experienced-based studies suggest this is a realistic price only from a much larger plant (24 tons/day), and the cost would be four times higher from mini-reformers (100 kg/day) at the likely future city-gate gas prices [19]. Moreover, local reformation is simply not compatible with CO₂ sequestration, and it would increase dependence on natural gas. Current proved U.S. natural gas reserves will last only 10 years, and there is increasing pessimism about future discoveries [20]. Until quite recently, most analysts have predicted sufficient natural gas reserves worldwide for the next 30 to 50 years. However, the most recent, detailed gas resource analysis, published in the Oil and Gas Journal, now predicts global conventional gas production peaking in 2019 [21].

There are, of course, a number of possible sources of hydrogen other than NG - coal, nuclear breeder reactors, wind farms in ideal locations, biomass (pyrolysis and water shift), catalytic reformation of ethanol, hydrogen-producing bacteria (such as various Clostridium), and solar electrolysis. Of these, only coal currently begins to compete economically with NG, but generat- ing LH2 from coal produces at least 8 kg of carbon (29 kg of CO₂) per kilogram of H₂ [4, 7]. When a realistic future (fossil) carbon tax of $0.1/kg of carbon is included [22], coal is likely to remain uncompetitive.

While the DOE/EIA are still predicting no increases in the price of fossil fuels over the next 15 years, it is worth noting that they have been forced to revise their price estimates upward (for gas, oil, and coal) every year for the past six years, and there is currently no question that another major upward revision will be required in their next annual projection. (Most experts outside the U.S. have done a much better job.) Although there are theoretically abundant stranded NG reserves worldwide for at least the next 40 years, the shortages in North America are becoming critical, as Canada is cutting back on exports (at the rate of at least 2%/year) to preserve their limited domestic resources [20, 23]. This is forcing the U.S. to frantically develop the infrastructure needed to import more liquefied NG (LNG) from the Persian Gulf, East Caspian, Northern Africa, South Pacific, Western Siberia, Nigeria, and other places where NG is currently abundant and cheap [24]. It is worth noting that in the past year the DOE/EIA have nearly quadrupled their projections for 12-years-out of LNG imports while cutting their projections of NG imports from Canada in half [25]. Also, numerous downward revisions of gas and oil reserves by various companies have been made during the past year.

The prices of LNG and fuel oil have stayed fairly close per unit energy for the past two decades (especially for the past seven years), and it is clear that LNG will not drop below fuel oil prices for prolonged periods. World-wide oil demand is beginning to exceed oil production. This will steadily drive oil prices up, and world oil prices (the dominant market) will establish minimum international LNG prices. As carbon taxes begin to be imposed and China's demand for LNG explodes, LNG will exceed pre-tax petroleum prices - probably by at least 25% within 25 years.

The assessment of oil reserves by the Association for Peak Oil [20] is now internationally recognized (except within the U.S.) as the gold standard in this field. The data are undeniable that the gap between global oil production capacity and global demand has dropped from over 8% to under 1.5% in the past three years, and China continues to deal with chronic oil and gas shortages. Clearly, the stage is set for continued increases in oil prices in the coming decade. Moreover, Campbell, Simmons, and other oil experts contend there are good reasons to believe that the Middle East reserves are significantly overstated [20]. Campbell's famous graph, "The Growing Gap", reproduced in Figure 2, is most telling.

The price of oil will trend toward the price of the replacements [23], which seems likely to be at least $60/bbl for next-generation biofuels from unsubsidized energy crops (as discussed shortly). The target price of $60/bbl has been publicly advocated over the near term by some ministers and economists from oil-producing nations [26]. If oil is $65/bbl 15 years from now (in 2004 dollars), imported LNG will be at least $12/GJ (more likely $13/GJ, assuming a modest carbon tax) and NG at the city gate will exceed $14/GJ. (Appreciation of this expectation has caused Iran to delay its LNG developments to get more favorable prices five years from now.)

Figure 2. Reproduced with permission from Colin Campbell [20].

So what can the typical consumer expect to pay (in current dollars) when filling his/her vehicle with pressurized hydrogen from an unsubsidized dispensing station in a mid-sized city not near a gas field? Clearly, previous cost estimates [5, 7, 14, 16, 19], that (1) assume 50,000 to 300,000 hydrogen vehicles per city, (2) are based on natural gas prices from several years ago, and (3) ignore the huge, demonstrated dispensing-station costs, are of very little value.

As earlier noted, as recently as five years ago some well-placed "experts" (at DOE and elsewhere) were expecting there would be 10,000 fuel cell vehicles (FCVs) on the road today [5]. Most experts today are expecting fewer than 800 will be on the road six years from now. Some think the numbers will grow much more rapidly in the following decades, though there is really no economic basis to support such projections. But let's be optimistic and assume there are 100,000 hydrogen vehicles on the road in 2015 - divided amongst the 100 cities of population over one-half million in the industrialized nations throughout the world. Figure 3 summarizes projected cost components for several different scenarios. For example, in case 3, assuming 1000 hydrogen vehicles per large city in the year 2015, consumers could expect to pay $19/kg for hydrogen. Note it is the huge dispensing costs associated with hydrogen when the number of vehicles per city is under 4000 that have previously been most often ignored, but available historical data support the estimates here [4]. The other component that will surprise many is the reforming cost, as most prior estimates have assumed a plant producing several hundred tonnes of H₂ per day, even though such a plant would be too large except for the largest cities with over 50% of the vehicles using hydrogen. The methods and realistic assumptions for these projections have been laid out in more detail elsewhere [4].

The current U.S. pre-tax cost of diesel, on the other hand, for the individual consumer at the local station is about $0.5/kg. Of course, one needs 3 kg to equal the energy of 1.0 kg of H₂, but that still leaves an order of magnitude cost advantage for diesel per unit energy. Estimates suggest the pre-tax price of bio-diesel from either bio-methanol or several oil-seed crops could ultimately be below $0.6/kg in the U.S. We return to this subject in a little more detail later.

Figure 3. Unsubsidized hydrogen cost breakdown for several years and numbers of FCVs per city. Assumptions, notes: All costs in 2004 USD/kg of HB2B. "LNG" is cost of imported liquefied natural gas, distributed to city, with energy equivalent to 1 kg HB2B. "Reforming" includes additional LNG and equip-ment costs. Additional local demand present to utilize all LH2 from a plant producing 22 tons/day. Power costs inflating 1.5%/ year. Tanker truck distribution. 5000 psi dispensing station.

At the risk of being extremely repetitious, we emphasize that we are well aware of the sharp discrepancies between our projections and those of others. It is only necessary to attempt to purchase pressurized hydrogen from any unsubsidized supplier to confirm that its current retail price is about $100/kg plus cylinder rental, not $6/kg, as most other experts imply. And no one should attempt to make any energy-related projections without reading Chapter 3 of Vaclav Smil's "Energy at the Cross-roads", in which he discusses hundreds of failed energy projections over the past thirty years [27]. A key lesson there is to appreciate historical data.

It should also be noted that global, recoverable, coal reserves are more limited than previously thought, so even coal is a relatively short-term option, especially if also used to meet oil and gas deficits and to produce LH2 with carbon sequestration, where net efficiency is under 48%.

Fuel-cell engine costs and performance. Phosphoric-acid, carbonate, and alkaline fuel cells, all of which are an order of magnitude easier to produce than PEMFCs, are available at prices under $3500/kW, but they are far too massive for use in automobiles [7]. The only type of hydrogen fuel cell being pursued for automotive applications is the PEMFC, also called PEFC (polymer electrolyte fuel cell). The cost of PEMFC vehicle engines (fuel cells, power conditioning, electric motors, etc.) is often reported to be in the range of $3,000-8,000 per kilowatt (100 times that of the common diesel engine), but available data suggest otherwise.

Inspection of the sales and financial data over the past two years from the largest current producer of PEMFCs for non-mobile use (Plug Power) suggests costs of 5 kW PEMFC-based AC power sources (not including R&D) are actually in the range of $15,000-$30,000/kW [28]. Larger PEMFCs with 30-35% HHV (higher heating value) electrical efficiency may be available in the range of $3000-5500/kW for combined heat and power (CHP) applications [7], but these FCs have inadequate environmental and vibrational tolerance for vehicles in addition to being much too large and massive. (UTC secured DOE funding by proposing to make CHP PEMFCs available for $1500/kW. They apparently delivered some 75 kW demo units (partially subsidized by EPRI, and getting only 31% efficiency) for $2600/kW [7].)

Over the past ten years, Ballard Power has probably furnished ~80% of all vehicle fuel-cell engines world wide. By some methods, one could conclude that the manufacturing cost, not including true R&D, of their latest fuel-cell engines (which still don't work reliably over an acceptable range of climates) has been over $1M each [29, 30]. Honda estimates the cost of their fuel-cell car will be $100K in mass production, which is expected to begin in 2012. Since similar cost projections in the fuel-cell industry for the past five years have proven overly optimistic by factors of 3 to 8, it may be more realistic to expect the Honda fuel-cell car to cost over $200K. It is noteworthy that fuel cells, including polymer types, have been in use and development for over forty years, and costs have not yet begun to drop significantly - notwithstanding many assertions to the contrary that use artificial costs from heavily subsidized projects or cite costs of massive, stationary fuel cells that are unsuitable for vehicles.

The cost of the PEMFC has relatively little dependence on the cost of the platinum catalysts. Its cost is mostly in the manufacturing complexities, and there are a number of fundamental reasons why the manufacturing problems of PEMFCs have not yielded to the hundreds of millions of dollars of R&D directed at them over the past decade. The simple concept figures often shown of two cross-flowing streams, hydrogen and oxygen, separated by a magical membrane, belie the serious challenges in a vehicle-grade PEMFC. Figure 4, taken from the DOE Fuel-Cell Handbook [31], does a little better job by showing that at least three isolated adjacent streams are required; as without the coolant stream, both water and thermal management are impossible. Miniaturization results in rapidly increasing pressure and electrical resistance losses. The limited dimensional stability of membrane materials contributes to flow separation and reliability issues. One of the big challenges is keeping just the right amount of moisture present in the membrane for good efficiency as temperature, load, and flow rates change.

A cost discussion is not complete without a discussion of reliability and lifetime. Some PEMFCs have reportedly demonstrated lifetimes com- patible with driving more than 100,000 miles, but lab tests and road tests are very different. (We're still waiting to see a fuel-cell vehicle driven from Miami to Maine via the Smoky Mountains in the winter - even one time, with a few stops and re-starts in Maine. Then, we need to see one hold up to a 40-minute daily commute for more than two years with minimal maintenance, and come through a highway accident with less than $200K in damages.)

Fuel-cell-stack lifetimes under environmentally limited road conditions are still typically 15-25% those of conventional diesel engines, partially because trace amounts (below several ppm) of SO₂, NO₂, HS, NH₃, CO and other contaminants in the atmosphere or fuel can temporarily or permanently incapacitate a PEMFC. When lifetime and maintenance are considered, one can argue that vehicle-qualified PEMFCs, which are still not competitive on a power per mass basis, are currently 400 times more expensive than diesel engines.

Finally, it is necessary to look objectively at efficiency. Yes, it is possible to exceed 65% efficiency in a very expensive and very massive solid oxide fuel cell (SOFC) at very high temperatures under moderate loads, but economic factors will dictate the use of low-cost PEMFCs, operating only a small fraction of the time at optimum load, so mean stack efficiency is likely to be under 38% [7]. The power electronics needed to regulate the battery charging and drive the motors could achieve 97% efficiency, but in the real world, 92% is more likely. The motors could achieve 96% efficiency, but 86% is a more likely typical number, for both cost and mass reasons. So net highway tank-to-wheels efficiency is likely to be under 32% in a production FCV. Moreover, the idle power consumption of an FCV is around 3 kW, while the idle power consumption of a hybrid vehicle is usually under 1 kW. It is also useful to note that the vendor of the state-of-the-art 2 kW PEMFC shown earlier in Figure 1 does not publish an efficiency. Rather, its volumetric hydrogen consumption rate, 25.2 L/min, is published, from which one initially calculates an HHV efficiency of about 41% at 2 kW, assuming the hydrogen at atmospheric pressure - until noticing that the minimum allowable inlet pressure is 130 kPa. So apparently its HHV efficiency at rated power is only 31.5%, comparable to that of an advanced diesel gen-set of similar size.

Gasoline engines have achieved 30% peak efficiency for two decades, and soon they will reach 38% efficiency [9]. Diesels have achieved 42% peak efficiency for more than a decade, and soon they will exceed 58% efficiency [9]. With variable valve timing, they can achieve high efficiency over a very broad speed range. Either ICE is fully compatible with low-cost renewable fuels that release no fossil CO₂. Advanced diesels with next-generation catalytic converters are clean, quiet, efficient, reliable, and affordable.

Fuel storage mass, volume, and safety. Safety-approved low-cost compressed gas cylinders currently achieve 1.5% H₂ storage by mass at 34 MPa (5000 psi). Aluminum tanks might achieve 6% H₂ storage. Pricing data from the high-volume production of aluminum scuba tanks suggest high-volume production of 5000-10,000 psi tanks for storage of 3-8 kg of H₂ might cost $600/kg of H₂ [32], which is about 30% less than suggested in an earlier study [14]. Carbon-fiber-wrapped tanks have rather low impact strength, and their costs are not dropping. A $12,000, carbon-fiber-wrapped fuel tank achieving 11% H₂ storage seems impractical for the small private car. The ultra-thin wall of these brittle tanks is not faithfully presented in the manufacturer's promotional pictures, as shown in Figure 5.

At 5000 psi, the volumetric energy density of H₂ is only 10% that of diesel. The mechanical energy alone stored in the hydrogen tank may be 5 times that of a 50-calliber artillery shell. The risks associated with carrying this mechanical bomb around are probably two orders of magnitude greater than we are accustomed to accepting in our gasoline-powered cars today. For safety reasons, the recent NAS/NAE study concluded both high-pressure tanks and cryogenic storage "have little promise of long-term practicality for light-duty vehicles" [7].

It is important to point out that leaks are not uncommon in high-pressure systems, especially with hydrogen, partly because of its very low molecular weight. A leak, whether slow or fast, from a hydrogen tank inside a garage can easily lead to an extremely dangerous explosion, owing largely to the combination of its very high flame velocity and extremely low ignition energy - about 0.02 mJ, or less than one-tenth that of methane or gasoline [30]. Unfortunately, alternative, safer storage methods (metal hydrides, carbon nanotubes, etc.) have thus far proven even less practical because of serious mass, fill time, and cost issues.

Of course, the energy per unit mass of pure hydrogen is three times that of diesel. So the net practical energy density (MJ/kg) of stored hydrogen, after including some extra structure needed for protection in the event of a collision, may be 18% that of diesel. The huge mass and volume penalties associated with practical H₂ storage seem likely to keep the range of marketable hydrogen-powered automobiles (such as the Honda FCX [33]) about 60% that of the diesel hybrid - notwithstanding some very expensive concept demonstrations to the contrary [34].

Infrastructure Development. Some have estimated that the development of an efficient hydrogen distribution infrastructure would cost only $300B [34], but those sources have consistently underestimated other "hydrogen economy" costs by huge factors. More careful estimates put the minimum infrastructure cost at $500B [30]. Most studies are now concluding the best approach would be based on large, central plants [7, 16], but the low energy density of LH2 means this will require an increase of a factor of twenty in the number of tanker trucks on our already overcrowded highways.

But infrastructure is more than just fuel distribution. The average vehicle lifetime is currently about 15 years, but it has been increasing rapidly for the past few years and could be 20 years within a decade. The cost of replacing 120 million cars and trucks over a shortened time frame at even a $70K premium per vehicle exceeds our nation's total national debt and is comparable to the total global energy investment over the past two decades! Even more daunting is the thought of revamping our vehicle manufacturing infrastructure (which includes dozens of multi-billion-dollar factories, thousands of smaller support factories, and millions of experienced workers) - before we really have a clue as to how it should be done.

We have seen relatively strong investment in fuel cell companies and divisions during the past ten years - $400M by venture capital firms, $300M from public investments, and much more from private, federal, and corporate sources. Dozens of fuel-cell-related companies were started over the past decade, but today only a handful of serious players are left in North America: Ballard Power BLDP (PEMs), Plug Power PLUG (PEMs), Hydrogenics HYGS (PEMs), Fuel Cell Energy FCEL (Carbonate FCs), Mechanical Technology MKTY (DMFCs), Distributed Energy Systems Corp (formerly Proton Energy Systems) DESC (PEMs), Astris Energi Inc ASRNF.OB (alkaline FCs), UTC UTX (several types of FCs), and Quantum Fuel Systems QTWW (tanks, H₂ infrastructure). Of these, all except MKTY and UTX are still showing huge losses (MKTY is not showing losses for artificial reasons, and UTX is a large company with other products), and probably only one of the hydrogen PEM fuel-cell companies will be a viable company three years from now. The major auto manufacturers and oil companies have their own fuel-cell projects, but none of them currently appears particularly successful. As shown for BLDP in Figure 6, BLDP, PLUG, and DESC are currently trading below 5% of their 4-year highs, and another order of magnitude drop in valuation (to market caps of about half of cash equivalents) seems likely in the coming years.

Undoubtedly, if the U.S. DOE invests $2.2B (as planned) over the next 6 years, a few hundred more demonstration vehicles (at perhaps $400K each) will be on the road, but that won't change much. After all, Ballard, Honda, GM, and Plug Power have each invested over $350M into PEM fuel cells over the past six years (and many other companies and research labs have invested lesser amounts over the past 40 years) with limited progress in manufacturing cost reduction. Notwithstanding recent announce- ments to the contrary, probably only one major auto manufacturer (Honda) will be producing FC vehicles after the DOE support ends seven years from now. And those FCVs will be at a price almost no one will be willing to pay.

Fossil CO₂ release. The primary source of H₂ in the U.S. (and most other countries) is currently natural gas. The nearly adiabatic partial-oxidation/ reformation/shift reactions use at least 3 kg of natural gas (90% CH4) to produce 1 kg of H₂ plus 9.5 kg of CO₂ [7]. When natural gas becomes too expensive, coal is chosen, which results in the release of over 16 kg of CO₂ per kg of H₂. Then, over 3 kg of coal must be burned (releasing another 10 kg of CO₂) to generate the 10 kWhr (36 MJ) needed to purify and liquefy 1 kg of H₂ [14], as required for efficient distribution. The energy efficiency in producing LH2 from natural gas ranges from 40-50%, depending on plant size. (This range has not budged in 15 years. We're near Carnot limits.) The energy content of 1 kg of H₂ is equivalent to about 3 kg (~1.06 gal.) of diesel, which contains only 2.5 kg of carbon, generating 9 kg of CO₂.

At 70 miles per gallon and assuming 85% efficiency in the production of fossil diesel, the advanced fossil-diesel hybrid achieves about 7 miles per kilogram of total CO₂, while the bio-diesel vehicle could achieve infinite miles/kg of fossil CO₂. The next-generation Honda FCX may get up to 57 mi/kg of H₂. At this rate, it achieves 1.9 to 3 miles/kg of total CO₂, depending on the H₂ production and distribution methods. Hence, when miles/kg of total fossil CO₂ ("fossil mileage") is fairly calculated, the total CO₂ generated per mile by a hydrogen vehicle is likely to be 2.5 times that of a comparable fossil-diesel-powered hybrid vehicle. The proposed hydrogen economy will do nothing to reduce CO₂ emissions. Rather, it will greatly increase CO₂ emissions - not just for a few decades, but until renewable hydrogen becomes competitive or scores of new nuclear power plants are built.

The nuclear option seems highly improbable unless fast breeder reactors are accepted and developed. Even though there has been a global glut (with depressed prices) of enriched uranium for the past thirty years, the IAEA concludes the total global uranium reserves (5 million tones) of good quality are sufficient to sustain current nuclear power plants, with a 2% annual growth rate, only through 2040. Others have recently concluded that even with near zero growth the high-grade ores (those greater than 0.15% U) will be depleted within 25 years [35]. Moreover, fifteen years after the high-grade ores are depleted, we'll be into the very-low-grade ores (below 0.02% U), which may have negative energy balance and result in more CO₂ emissions (during the ore refining, processing, disposal, etc.) than would be produced by gas-fired power plants. For reference, it is useful to note that the total uranium abundance in the earth's crust is estimated to be 2.7 ppm, or about 4% that of copper. The price of natural uranium has doubled in the past four years, but still it is only about fifteen times as expensive as copper, even though within a few decades it will likely remain only in hard, low-concentration ores. (The low price of uranium is a direct result of the state funds invested in the nuclear industry, which world-wide over the past 50 years have exceeded $300B in current dollars.) Still, the DOE short-sightedly focuses on once-through designs and doesn't expect to see Generation IV fast breeder reactors beginning to be utilized until after 2040. It's hard to see how the price of uranium will not quad- ruple, in real dollars, in the next fifteen years - and quadruple again in the twenty years thereafter.

Renewable Hydrogen. Wind energy is now a viable power option in specific localities. If used for hydrogen production without a hydrogen gas line to the wind farm, the hydrogen would need to be liquefied for transport. To generate and liquefy 10 tons/day (one rail-tanker per day on average) would require at least 100 MW installed rated capacity for 30 MW average capacity, which requires 200 wind turbines of 39 m span in a Class 5 site [36]. This assumes 80% electrolysis efficiency, even though 65% is currently more common, as there is good reason to expect 80-85% will eventually be practical in large facilities when energy is more valuable. Liquefaction efficiency is assumed to be 60%, though lower efficiencies are currently achieved in plants of this size. The capital cost of the wind turbines (installed) would be about $60M-90M, and the effective power cost (20 year payback) is expected to be about $0.06/kWhr [37]. This could make the wholesale cost of LH2 at a very large wind farm (at a choice location) as low as $6.9/kg within 10 years, assuming substantial progress in cost reduction of electrolysis equipment (which seems probable, [7, 38]) and some further progress in wind turbine technology (especially, for non-synchronous power applications, as for hydrogen or ammonia production).

Quite a number of excellent locations can be found for wind farms in the Dakotas, Kansas, Wyoming, and several other states, and the trend of decreasing costs of wind turbines will probably continue for at least another decade. However, until such time as we are no longer using coal to power the grid within at least 1000 km of wind farms, it seems that the best use of this wind energy would be to put it into the grid, as this would not require wasting 50% right off the top for electrolysis and liquefaction [30]. When surplus wind energy becomes available is select regions, perhaps the best use of it would be to produce ammonia for renewable fertilizers, as ammonia is much more easily trucked than hydrogen and ammonia production currently accounts for about two-thirds of our total hydrogen usage. Electrolysis hydrogen from wind farms in Class 5 sites could compete with natural gas for chemical fertilizer production, hydro-cracking of heavy oils, and hydroforming of fuels when natural gas prices exceed $11/GJ. (Imported LNG seems headed for this price within 10 years.) Nearly 400 GW of installed wind power (30 times the current world-wide in- stalled base, and 4 times the current stated U.S. goal for 2020) would be required to produce all the hydrogen needed for these industries in the U.S. Such a massive scale-up in wind energy could eliminate U.S. dependence on imported LNG for many decades and dramatically reduce U.S. green house gas emissions.

As shown in Figure 7 photovoltaic (PV) production has risen sharply in the past few years, thanks primarily to Japans commitment. The cost of PV cells has dropped by a factor of three in the past decade and is now about $6/W, which works out to about $0.18/kWhr for energy in many locations [39]. Though Japans strong support for solar will soon end, GE appears ready to take over, and another factor of two drop in cost is expected in the next decade [39, 40]. While this could potentially bring the cost of PV-generated bulk hydrogen gas at a large plant down to $8/kg, but, as seen from Fig. 3, that is still twice the projected cost of bulk hydrogen gas from fossil sources twenty years from now. It is also important to keep in mind that the cost would likely be twice this for the private home owner, because of the relatively high costs and poor efficiency of small electrolyzers, purification equipment, compressors, and storage tanks. There would also appear to be unacceptable hazards associated therewith.

Hydrogen from biomass (pyrolysis and water shift) using waste biomass (from logging, paper mills, farming, and clearing) is about 10% more expensive than hydrogen from coal without se- questration [7], but this is not likely to be a significant source, as waste biomass is limited and is likely to be more valuable in the production of bio-methanol and biodiesel, as will be discussed shortly. Tokamak fusion reactors and lunar stations beaming power back to earth appear to have little more practical basis than cold fusion.

As noted earlier, breeder reactors appear highly improbable for at least three decades, but they do seem to offer the real possibility of a nearly limitless energy supply. There are clearly huge safety and proliferation issues associated with the notion of breeder reactors, as advances in robotics will only make it easier for terrorist groups to build powerful nuclear weapons from the plutonium-rich waste and intermediate products from breeder reactors. And there are huge technical issues, as attested to by 40 years of failed attempts to demonstrate an operating cycle [35]. Still breeders seem orders of magnitude more practical than fusion reactors, and the efficiency with which a breeder reactor should in principle be able to utilize natural uranium suggests they may make it cost effective to extract uranium from the sea (even at $1000/kg, 25 times the current price and about three times the price estimated by one study), where there is probably enough to power breeder reactors supplying energy for the entire world for millions of years. Although the above suggests breeder reactors are eventually inevitable, it does not imply a hydrogen economy is, as it will still be more cost effective to distribute their energy via electricity, and it will still be much more practical to utilize liquid biofuels for transportation, even if electrical energy from breeder reactors sixty years from now is half the cost of raw bio-energy.

Hydrogen Hype. How could such a well-intentioned scientific endeavor as clean energy stray so far from reality? Perhaps like this. For three decades, it has been pretty clear to many concerned scientists that our world's cheap oil supplies would be largely depleted within their lifetime and major changes would be forced upon us. Moreover, it was common knowledge in the mid-1970's that hydrogen fuel cells for more than a decade had achieved up to three times the efficiency of gasoline engines, and very cheap natural gas resources (hence, hydrogen) seemed inexhaustible. It was reasonable to expect that major progress could be made in reducing the manufacturing cost of fuel cells, so the notion of a hydrogen economy, ultimately based on nuclear power plants, seemed to have economic merit. Undoubtedly, the fact that the basic reaction was conceptually based on fifth-grade chemistry also contributed to its popularity.

It would then take more than two decades (until early 2001) for five major realities to begin to be appreciated by a few scientists. First of all, order-of-magnitude cost reductions in manufacturing processes are almost never realized after the fourth decade of development. Secondly, the efficiency of ICEs would steadily improve. Thirdly, global warming would have to be seriously addressed much sooner than most had expected. Fourthly, the price of natural gas in many areas would skyrocket early in the 21st century as demand began to exceed local supply. And finally, nuclear power would not be accepted again for many decades.

As long as the sales revenue in any developing industry is an order of magnitude smaller than other sources of revenue (such as investment capital and federal grants), the product sales prices are likely to be severely underestimating actual production costs. However, if we can believe the reports that rather massive, low-efficiency (31%), 75 kW PEMFCs for non-mobile use, now perhaps in small scale production, can finally be produced for about $2500/kW [7], then it seems reasonable to project that the production cost for vehicle-grade PEMFC systems might be ~$5000/kW at a similar (small) production scale. Current commercial experience in the DMFC industry points to the same price as being realistic for small-scale production. Ford is currently estimating the production cost of their 1600 kg Focus FCV (with an 85 kW FC stack) will be about $350,000 each in quantities of 30 units per year [41]. Of course, a cost reduction of two orders of magnitude is possible when going from first experimental prototypes to large scale production, but that opportunity is long past. As previously noted, nearly a billion dollars has already been expended on the central issues of manufacturability and reliability of fuel cells over the past two decades, and they have been in small scale commercial production for several years. The available opportunity is going from small scale production to large scale production. Manufacturing history suggests a factor-of-six reduction in cost is about the limit that can be expected here. The catch is that high-volume production will never materialize, even if a fully adequate fueling infrastructure were completed by 2020, given the (A) short time (perhaps 10 years) that natural gas would still be available at a semi-tolerable price, (B) serious global warming issue with hydrogen from coal, (C) serious safety issues with hydrogen fuel, (D) short FC life in vehicles, (E) limited driving range of hydrogen vehicles, (F) poor tolerance of PEMFCs to normal environmental conditions, and (G) competition from next-generation liquid biofuels in advanced ICEs.

There are several possible explanations for the continuation of the hydrogen hype. It is possible that some have seen a security reason for deliberately hyping hydrogen even after the above facts began to be appreciated. One can certainly argue that it is in the U.S. security interest for Russia's oil reserves to become depleted to below U.S. reserves while oil prices are low. The best way to achieve this is to convince the oil exporting countries they must pump out all of their resources before the hydrogen economy makes their oil resource obsolete. Keeping the price of oil low hurts the oil exporting countries, the second largest of which is Russia. As bizarre as this suggestion sounds, it is actually supported by statements from high-level Middle-East oil ministers [22]. But probably the main reason that hydrogen hype shows little evidence yet of abating is inertia - in research, business, and politics. The careers of thousands of scientists, businessmen, and politicians are now bound up in the hydrogen hoopla. (It has been observed that a number of current U.S. administration high-level officials and family members have notable holdings in companies involved in the platinum-group metals needed for PEMFCs.) It is unlikely that evidence of pervasive scientific flaws will be sufficient to change many minds very quickly on this subject. Our best hope for progress comes from the rapidly rising prices of oil and gas over the past three years, which are likely to result in greatly increased funding of research and industry that can make a difference within the next decade.

Clearly, we must take seriously the fact that the world will soon be running out of cheap, fossil oil; and if we don't prepare by developing viable alternatives, the economic consequences will be severe. Focusing all our efforts on a single dream that seems less and less likely to be of any practical benefit is worse than doing nothing at all because of the false hope it engenders. Simply put, hydrogen will never compete with liquid biofuels in the transportation arena.

Sustainability via Next-generation Liquid Biofuels. It's surprising how few people (even among those who study these issues) understand that bio-fuels needn't contribute at all to global warming. When biomass is burned, the carbon is just going back to where it was a few months or years earlier before the plants took it out of the atmosphere [42, 43]. In fact, intensive cultivation of biomass often results in additional carbon being sequestered in the soil, and thus really reduces atmospheric CO₂. It's true that current methods of producing fertilizers release quite a bit of fossil CO₂ and farming has used petroleum diesel, but it needn't be that way. Anaerobic digestion of animal waste is an economically viable source of fertilizers and could soon begin making a significant contribution to our methane needs [44]. And as mentioned earlier, wind can be used to make renewable fertilizers.

The energy balance (ratio of chemical energy of the biofuel plus co-products to the energy required for fertilizing, growing, harvesting, and processing minus processing energy derived from the raw biomass) for ethanol from corn has increased steadily over the past decade from 1.2 in the early 1990s up to 1.57 to 1.77 today, depending mostly on the processing method [45]. However, there are a large number of promising options for biofuels with much higher efficiency and much lower environmental impact. Ethanol from sugar cane, with fossil energy balance well above 5, is clearly the most cost effective and efficient biofuel today in climates where sugar cane thrives. Ethanol production in Brazil is currently over 4.6 billion gallons per year, nearly 25% of gasoline usage, and ethanol production there may exceed 80% of their private transportation fuel usage within a decade - especially if export restrictions are relaxed.

Cellulosic bio-ethanol (especially from switchgrass, but also eucalyptus, hemp, poplars, pines, and all types of wood wastes) is steadily becoming more competitive [46]. It promises net efficiency well over 40% with no depletion (in fact, augmentation) of soil organic material. (Net efficiency is the energy of the biofuel divided by the sum of the total chemical energy of the raw biomass plus all production energy inputs.) The primary problem with cellulosic ethanol has been the cost of the enzyme, cellulase, needed to convert the cellulose into glucose for fermentation into ethanol. Fortunately, there has recently been major progress here that has reduced its cost by an order of magnitude [47], and further dramatic cost reductions are anticipated in the next few years [48]. This could very well enable ethanol to be produced from waste wood and paper at prices below the current pre-tax cost of gasoline per unit energy. However, advanced diesel engines will still be 50% more efficient than even next-generation spark-ignition ethanol engines, so bio-diesel deserves much attention.

Bio-diesel from waste animal oils (including tallow and lard) and current oil crops is a good place to begin [49]. Rape seed is currently the best oil crop, and other excellent oil crops that do well in many places include peanuts, olives, sunflowers, mustard seed, sesame, and pumpkin seed [50]. Biodiesel production in the U.S. last year was under 25 million gallons, but it is expected to grow to 120 million gallons annually within a few years, largely because of the new fuel tax credit and the recently increased price of fossil diesel. It has been thought that biodiesel could only deliver about one billion (B) gallons per year (less than 1% of U.S. needs) before the mar- ket for the glycerin byproduct is saturated, at which point biodiesel becomes 25% more expen- sive. But hydrocracking of glycerin into simple alcohols, which is just beginning to be studied, seems likely to address this concern. Other possibilities are bio-methanol, higher alcohols, straight vegetable oils, and high-oil algae, none of which are currently being pursued in a major way.

The transesterification process required to produce the methyl ester (biodiesel) from vegetable oils contributes some to its cost. It is possible to use many straight vegetable oils in slightly modified diesel engines. Hobbyists have achieved very promising preliminary results by simply including a fuel warmer to facilitate starting. However, it is not yet known whether this option can compete with the advanced diesel engine in either efficiency or engine maintenance costs.

Methanol is a major commodity chemical (over 10 million tonnes/yr) that is efficiently produced from high-pressure-catalyzed syngas (CO + H₂), usually from natural gas, but syngas can just as easily be produced from gasification (pyrolysis) of any biomass. Biomethanol, from biomass (especially wastes and woody biomass), may be a more economical source for biofuels. Woody biomass can be converted to methanol with up to 61% efficiency [51], and the additional energy required for harvesting and fertilizing may be quite low for switchgrass, hemp, poplars, and eucalyptus. Moreover, when the waste heat from the methanol plant can also be utilized for space heating or Combined Heat and Power (CHP), the total biomass energy utilization rises to 67-82% efficiency [51]. The primary challenge still is the competition from natural gas, as recently developed liquid-phase oxidation methods promise to produce methanol from methane at costs under $60/ton, plus the cost of the methane, which may continue to be quite cheap in some remote locations for several decades.

The woody biomass wasted each year (primarily from logging operations, construction site clearing, and saw mills) in the U.S. is estimated to be sufficient to produce over 12B gal of bio-methanol, from which perhaps 5B gal of biodiesel could be produced, as discussed shortly. The dark liquor waste from domestic paper mills could produce several times that amount of bio-methanol [52]. Switchgrass can produce 11 tons of dry, woody biomass per acre per year [53], which should be sufficient for up to 2000 gallons of biomethanol, or perhaps 800 gallons of bio-diesel, or ultimately up to 1100 gallons (currently, 750 gallons) of cellulosic ethanol. Hemp may have even higher biomass yields in many climates [54].

Efficient, moderate-sized methanol plants have been built to produce 83,000 tonnes (28 million gallons) of bio-methanol per year, which require about 12,000 to 40,000 acres for sustainable harvesting, depending on the climate [46, 51]. Currently, the cost of a plant of this size is roughly $100M, and the cost of a biomethanol plant of five times this capacity is roughly three times as much, while cellulosic ethanol plants may be somewhat more expensive.

A significant part of the operating cost with biomass can be the transportation of the feedstock to the processing plant, even for dedicated biomass land use. For dual-use lands, the transportation costs can go way up, so smaller bio-mass plants could be more cost effective, though plants below 3 million gallons per year have not been cost effective. Hence, we may see a future with thousands of bio-mass plants scattered throughout rural and suburban areas. (Obviously, there are huge economic and social implications involved here - especially, enormous rural job creation and the long-awaited recovery in the chemical industry.) Some of the product would be used locally, but most of the bio-methanol would be trucked or piped to refineries to be converted to diesel, gasoline, and jet fuel.

One might consider using straight biomethanol as a vehicle fuel, though its effective fume toxicity is greater than that of gasoline when its higher vapor pressure is also considered. But it has low energy density (50% that of diesel, by volume) and it is not yet clear that either DMFCs or methanol-fueled ICEs can exceed 35% efficiency in practice. Diesel is a better engine fuel, and methanol can efficiently be converted to diesel (or gasoline) via dehydration to ethylene followed by reformation chemistry similar to, but more selective and efficient than, conventional Fischer Tropsch synthesis, generally referred to as Fischer Tropsch Type (FTT) chemistry [55]. How- ever, 20% methanol in gasoline has very recently been shown to be more effective than either MTBE (methyl tertiary butyl ether), tetraethyl lead, or ethanol additions in improving efficiency and power and in reducing emissions [56].

Novel Biofuels. One of the advantages of the gasification/Gas-to-Liquids (GTL) processes is that the input can be any type of carbonaceous material, including farm waste, sewage sludge, and cheap coal. While operating and maintenance costs are likely to be higher for gasification of very dirty feed stocks into clean syngas, the feed stock itself may have negative cost - i.e., the waste producer may be willing to pay to dispose of it. It's also worth pointing out that relatively minor changes in the methanol GTL process allow it to become an efficient ammonia process for renewable fertilizer. Of course, the gasification process can also be modified to produce high-purity hydrogen with high efficiency, but that does nothing to address the enormous storage, distribution, safety, and engine cost issues still associated with hydrogen. (Other bio-hydrogen processes are currently far more costly and problematic [57].)

Recent modifications of GTL processes may allow efficient production of a mixture of higher alcohols, including ethanol, propanol, butanols, pentanols, and hexanols, from syngas [58]. High-alcohols have several attractive characteristics as fuels. They have extremely low fire hazard, very high octane rating, relatively low toxicity, low vapor pressure, high energy density (85% that of diesel, by volume), and are water soluble and bio-degradable (which allows them to be shipped without environmental concern in old, surplus, single-hulled tankers). The mixed- alcohol process is being developed primarily for improved gasoline oxygenates and octane en- hancers [58], but there is reason to believe that ICEs burning straight mixed-alcohol fuels could achieve ultra low emissions and efficiencies close to those of diesel engines. The methanol-from-methane plant shown in Figure 8 (Denver area), may soon be converted to this process.

While these high-alcohol GTL processes are still not publicly well characterized, it seems likely they could become very cost-effective. In fact, a significant concern is that it may be possible to produce mixed-alcohol fuels, with no on-site CO₂ emissions, from a mixed feedstock of stranded gas and coal so cheaply that biomass sources, which are essential for global warming mitigation, may have difficulty competing for three more decades. (Of course, the demand for the stranded gas for other growing markets is likely to keep it relatively expensive, so biofuels may still compete.) All GTL processes that do not utilize at least 75% methane as the feedstock also release considerable CO₂, which is a concern if the feedstock is not predominately biomass. If cheap renewable electricity is available locally (e.g., from a nearby wind farm), electrolysis hydrogen can be used to efficiently convert the waste CO₂ from the GTL plant to additional biofuels [59], especially alcohols.

Another promising option under investigation is breaking down clean biomass and separating it into digestible carbohydrates, protein, and remaining biomass (lignins, etc.), with the protein being used as animal feed, the carbohydrates being turned into ethanol using biological proc- esses, and the remaining biomass being converted into bio-diesel or alcohols via a thermo-chemical process. Although the chemical-process-equipment industry is mature, production of the specialized plants needed for biomethanol, cellulosic ethanol, higher alcohols, and biomass separation is still in its infancy. Hence, there is good reason to believe substantial cost reductions will be possible in the future.

Another promising source for biodiesel is high-oil algae. Estimates suggest 100 billion gallons of biodiesel could be produced from 10,700 square miles of salt-water ponds in relatively small farms in the desert. Perhaps enough biodiesel to replace all petroleum transportation fuels in the U.S. could be grown in roughly 10% of the area of the Sonora desert in the Southwest [60]. It has been estimated that it would cost $170B to establish these farms and $50B/yr to operate them to the point of yielding algae feedstock for the refineries. Perhaps it would cost another $40B/yr to produce the biodiesel from the algae feedstock, but all of these estimates have high uncertainties - especially the cost of delivering the hundreds of millions of tons of CO₂ (from coal power plants) and other nutrients to the ponds. Distributed approaches, especially growing the algae off municipal waste streams, may be even more attractive.

Conclusion. Will bio-mass be adequate for the longer range outlook, seventy years from now? Undoubtedly, wind, solar, and clean coal with carbon sequestration will play a larger role, and we'll see electric vehicles with more advanced batteries finally competing. Perhaps we'll also see biofuel plants located near huge wind farms in favorable areas for enhanced production of higher mixed bio-alcohols. But the primary intermediary in transportation will still not be hydrogen - not even in countries where there is no spare farm land capacity for biofuels. Hydrogen simply isn't the best way to distribute energy [61] or to power vehicles. We'll still be pumping liquid fuel into our tanks - whether it will primarily be biodiesel, ethanol, or high-alcohols is yet to be determined. And the huge international petroleum trade may largely be replaced with international trade in biofuels . For now, our first priority should be useful (practical) solutions for the next five to thirty years.

The U.S. DOE commissioned a study by the National Academies of Engineering to review the hydrogen initiative, and it has recently released a draft of its report [7]. This report bluntly points out the serious challenges facing fuel cells and notes that it is unlikely they will have a signifi- cant effect on oil imports or CO₂ emissions during the next 25 years. However, this report still only takes cautious steps and fails to appreciate the urgency of the need for viable energy alternatives - possibly because it was completed before major reserves overstatements by several large energy firms had surfaced and before the DOE/EIA had begun to admit that serious oil and gas shortages may develop within several years.

The evidence for both an impending energy disaster and a climate disaster if we do not respond in meaningful ways is becoming irrefutable, and the scientific case against hydrogen is also now undeniable. Five years from now, in hindsight, the hydrogen program will look more like a ruse then naive scientific exuberance if major changes in energy programs are not forthcoming in response to these scientific challenges. Simply changing priorities in existing hydrogen R&D programs will not bring a useful solution within 30 years and probably not within 70 years, as futuristic energy technology projections beyond five years by scientific organizations have a history of being overly optimistic. (For example, controlled fusion has been 40 years away for the past 50 years.) We must rapidly ramp up all promising renewable options available if we are to be prepared for the likelihood of $70/bbl oil and major climate shifts in the not-too-distant future. Major investments are needed into bio-methanol, cellulosic ethanol, advanced biodiesel crops, mixed-alcohols, high-oil algae, and advanced catalysts for biofuels from bio-syngas. It's time we start putting some serious money into real options for renewable energy to address global warming and our future transportation needs.

References 1. George Olah, "The Methanol Economy", C&E News, September 22, 2003. See also, http://chem.usc.edu/faculty/Olah.html
2. http://www.fuelcellstore.com/cgi-bin/fuelweb/view=Item/cat=31/product=558, 2004.
3. Based on price quote from Air Products, http://www.airproducts.com.
4. F. David Doty, "A Realistic Look at Hydrogen Price Projections", http://www.dotynmr.com/PDF/Doty_H2Price.pdf, 2004.
5. J. Ohi, "Blueprint for Hydrogen Fuel Infrastructure Development", NREL/MP-540-27770, 2000. http://www.eere.energy.gov/hydrogenandfuelcells/pdfs/mp27770.pdf
6. Automotive News World Congress, Bosch report, http://www.calstart.org/info/newsnotes/nn_detail.php?id=6384, 2004.
7. The Hydrogen Economy: Opportunities, Costs, Barriers, and R&D Needs, Committee on Alternatives and Strategies for Future Hydrogen Production and Use, National Academy of Engineering, National Academies Press, http://www.nap.edu/books/0309091632/html/ 2004.
8. J. M. Ogden, T. G. Kreutz and M. Steinbugler, "Fuels for Fuel Cell Vehicles: Vehicle Design and Infrastructure Issues", SAE Technical Paper Series, 982500, 1998. http://www.princeton.edu/~energy/publications/pdf/1998/Fuels_FC_vehicles_V_design.pdf
9. James J. Eberhardt, "Fuels of the Future for Cars and Trucks", presented at DEER, 2002. See http://www.osti.gov/fcvt/deer2002/deer2002wkshp.html.
10. Julian Darley, Post Carbon Institute, http://www.postcarbon.org/, 2004.
11. http://www.eia.doe.gov/neic/historic/hngas2.htm#Price , 2004.
12. http://www.fair-pr.com/background/h2fuelingstations.pdf , 2003. http://www.epa.gov/otaq/fuelcell/hydrogen-fueling.htm, 2004.
13. Joan Ogden, "Prospects for Building a Hydrogen Energy Infrastructure", http://www.princeton.edu/~cmi/research/papers/prospects.pdf (1999).
14. Wade Amos, "Costs of Storing and Transporting Hydrogen", NERL/TP-570-25106, 1998, http://www.eere.energy.gov/hydrogenandfuelcells/pdfs/25106.pdf.
15. S. S. Babu, M. Murugananth, Z. Feng, and M. L. Santella, "Hydrogen Permeability and Integrity of Hydrogen Transfer Pipelines", Lincoln Electric Co., http://mjndeweb.ms.ornl.gov/Babu/EE/h2pipe/h2.pdf, 2003.
16. D. Simbeck and E. Chang, "Hydrogen Supply: Cost Estimates for Hydrogen Pathways," DOE-NERL 540-32535, http://www.nrel.gov/docs/fy03osti/32525.pdf, 2002.
17. http://www.fuelcellstore.com/cgi-bin/fuelweb/view=Item/cat=88/product=476, 2004.
18. http://www.eere.energy.gov/hydrogenandfuelcells/pdfs/33098_sec2-4.pdf.
19. C. E. G. Padro and V. Putsche, "Survey of the Economics of Hydrogen Technologies", NREL/TP-570-27079, http://www.eere.energy.gov/hydrogenandfuelcells/pdfs/27079.pdf.
20. Colin Campbell, ASPO Newsletter #44, http://216.187.75.220/newsletter44.pdf, 2004.
21. A. Imam R. A. Startzman, and M. A. Barrufet, "Hubbert Revisited-6" Oil and Gas Journal 102, 31, Aug. 16, 2004, http://ogj.pennnet.com.
22. A. Traverso, A. F. Massardo, M. Santarelli, and M. Cali, "A New Generalized Carbon Exergy Tax: An Effective Rule to Control Global Warming", J. Engr. for Gas Turbines and Power, 125, 972-978, 2003. David King, "Climate Change Science: Adapt, Mitigate, or Ignore", Sci., 9 Jan. 2004, http://www.sciencemag.org/cgi/reprint/303/5655/176.pdf.
23. Jean H. Laherrre. "How to Estimate Future Oil Supply and Demand", International Confer- ence on Oil Demand, Production, and Costs, Danish Society of Engineers, Copenhagen, Dec., 2003. http://www.hubbertpeak.com/laherrere/Copenhagen2003.pdf.
24. LNG Review, http://www.lngexpress.com/lngrev/intro_sglocs.asp, 2001. See also, http://www.naturalgas.org/lng/lng.asp, 2004.
25. EIA/DOE http://www.eia.doe.gov/oiaf/aeo/issues_3.html, 2004.
26. Andrew McKillop, "Why we need $60/barrel oil", Intern. Assoc. of Energy Economists, Arab Petroleum Research Center, http://www.oilcrisis.org/mcKillop/WhyWeNeedUSD6O_Oil.pdf
27. Vaclav Smil, Energy at the Crossroads, MIT Press, 2003.
28. Plug Power revenue from 600kW of fuel cells was $9.4M, and their losses were six times revenue. http://www.plugpower.com/index.cfm?vid=227422&liak=51908070, 2003.
29. Ballard Power financial data at http://finance.yahoo.com/q?s=bldp&d=t , 2004.
30. Joseph J. Romm, The Hype About Hydrogen, Island Press, 2004.
31. Fuel Cell Handbook, 6th ed., US DOE, http://www.netl.doe.gov/publications/, 2002.
32. http://www.diveriteexpress.com/gas/aluminum.shtml#al6, 2004.
33. Honda, FCX, http://www.hondacorporate.com/fcx/overview.html, 2004.
34. Amory Lovins, http://www.rmi.org/images/other/E-20HydrogenMyths.pdf , 2003.
35. J. W. Storm van Leeuwen and P. Smith, http://beheer.oprit.rug.nl/deenen/, 2003. See also, Hermann Sheer, Nuclear Energy Belongs in the Technology Museum, http://www.renewableenergyaccess.com/rea/news/story?id=19012, 2004.
36. See http://www.nrel.gov/wind/, and http://www.windpower.org/composite-85.htm, 2004.
37. J. DeCarolis and D.W. Keith, Proc. of the 1st Intern. Doctoral Consortium on Tech., Policy, and Management, E.F.t. Heuvelhof ed, Delft Univ., Delft, The Netherlands, p. 199-215, http://www.andrew.cmu.edu/user/dk3p/papers/53.DeCarolis.2002.IsTheAnswerBlowingInTheWind.f.pdf, 2002.
38. John Busby, http://www.after-oil.co.uk/energy.htm#sources, 2004.
39. Jeff Johnson, Power From the Sun, C&EN, June 21, 2004, http://pubs.acs.org/cen/coverstory/8225/8225solarenergy.html.
40. http://www.eere.energy.gov/femp/techassist/photovoltaics.html, 2004.
41. John McCormick, Walking Fords fuel cell vehicle assembly line, Hydrogen Forecast, http://hydrogenforecast.com/AugustArticles/hfc_ford090904.html, 2004.
42. http://ww2.green-trust.org:8383/2000/biofuel/biofuel.htm, 2004.
43. http://www.irish-energy.ie/uploads/documents/upload/publications/biomass_factsheet.pdf.
44. http://www.eere.energy.gov/consumerinfo/refbriefs/ab5.html, 2004.
45. Hosein Shapouri, USDA, http://www.edoane.com/show_story.php?id=25636.
46. L. B. Lave, W. M. Griffin, and H. MacLean, "The Ethanol Answer to Carbon Emissions", Is- sues in Sci. and Tech., Winter, 2001. http://www.nap.edu/issues/18.2/lave.html.
47. Iogen, http://www.iogen.ca/3000.html 2004.
48. http://www.novozymes.com/cgi-bin/bvisapi.dll/biotimes/one_article.jsp?id=27092&lang=en.
49. http://ww2.green-trust.org:8383/biodiesel.htm, http://www.biodiesel.org/, 2004.
50. http://journeytoforever.org/biodiesel_vehicle.html#stds , 2004.
51. Mikael Ohlstrom, T. Makinen, J. Laurikko, and R. Pipatti, "New concepts for biofuels in transportation: Biomass-based methanol ...", VTT Energy, Finland, 2001. http://www.inf.vtt.fi/pdf/tiedotteet/2001/T2074.pdf.
52. http://www.methanol.org/ , 2004.
53. http://bioenergy.ornl.gov/papers/misc/switgrs.html , 2004.
54. http://www.hempcar.org/hempfacts.shtml .
55. G. A. Olah and A. Molnar, Hydrocarbon Chemistry, Wiley & Sons, NY, 1995.
56. A. A. Al-Farayedhi, A. M. Al-Dawood, P. Gandhidasan, "Exp. Investigation of SI Engine Per- formance Using Oxy. Fuel", J. of Engr. for Gas Turbines and Power, 126, 178-191, 2004.
57. http://www.engr.psu.edu/h2e/Pub/Logan_etal_2.htm, 2004.
58. Mark Radosevich, Standard Alcohol Co., http://www.standardalcohol.com/biofuel.htm, 2004.
59. M. Specht and A. Bandi, "The Methanol Cycle Sustainable Supply of Liquid Fuels, http://www.methanol.org/pdf/ZSWMethanolCycle.pdf , 1999.
60. http://www.unh.edu/p2/biodiesel/article_alge.html .
61. P. Mazza and R. Hammerschlag, Carrying the Energy Future, http://www.ilea.org/ 2004.

Comments

Only registered users can write comments.
Please login or register.

Powered by AkoComment 2.0!