America is addicted to oil, and that our addiction to a fossil fuels has to come to an end is obivous. One of the more widely panned panacea’s to our current energy situation is the promise of a Hydrogen economy. Just one small catch:
Rakesh Agrawal, Purdue’s Winthrop E. Stone Distinguished Professor of Chemical Engineering, co-authored an article in 2005 that outlined the daunting technical
challenges standing in the way of the mass production and use of hydrogen fuel-cell cars.
The article, titled “The Hydrogen Economy: Opportunities, Costs, Barriers and R&D Needs,” was the cover story in the AIChE Journal, a publication of the American Institute of
Chemical Engineers.
According to Agrawal, today’s fuel cells generate power at a cost of greater than $2,000 per kilowatt, compared with $35 per kilowatt for the internal combustion engine, so they
are more than 50 times more expensive than conventional automotive technology.
At the same time, fuel cells have an operating lifetime for cars of less than 1,000 hours of driving time, compared with at least 5,000 hours of driving time for an internal combustion engine.
“That means fuel cells wear out at least five times faster than internal combustion engines,” Agrawal said. “If I buy a new car, I expect it to last, say, 10 years, which equates to about 3,000 hours of driving time. If my fuel cell only lasts 1,000 hours, you can see that’s not very practical.”
To bring down the cost of fuel cells, less expensive catalysts and membrane materials are needed, said Agrawal, who also noted that a fuel-cell car built with today’s storage and transportation technology would cost about $250,000.
I guess we better get used to walking…….
Beyond the current economics of the hydrogen car, there is huge potential for a hydrogen economy.
First, I think it’s important to make a few things clear.
At this time, the most common methods for producing hydrogen involve the steam reformation of various fossil fuels:
Steam Methane Reforming
About 95% of the hydrogen produced today in the United States is made via steam methane reforming, a process in which high-temperature steam (700 – 1000°C) is used to produce hydrogen from a methane source, such as natural gas. In steam methane reforming, methane reacts with steam under 3-25 bar pressure (1 bar = 14.5psi) in the presence of a catalyst to produce hydrogen, carbon monoxide, and a relatively small amount of carbon dioxide. Steam reforming is endothermic – that is, heat must be supplied to the process for the reaction to proceed.
Subsequently, in what is called the “water-gas shift reaction,” the carbon monoxide and steam are reacted using a catalyst to produce carbon dioxide and more hydrogen. In a final process step called “pressure-swing adsorption,” carbon dioxide and other impurities are removed from the gas stream, leaving essentially pure hydrogen. Steam reforming can also be used to produce hydrogen from other fuels, such as ethanol, propane, or even gasoline.
Steam Reforming Reactions
Methane:
CH4 + H2O (+heat) → CO + 3H2
Propane:
C3H8 + 3H2O (+heat) → 3CO + 7H2
Ethanol:
C2H5OH + H2O (+heat) → 2CO + 4H2
Gasoline (using iso-octane and toluene as example compounds from the hundred or more compounds present in gasoline):
C8H18 + 8H2O (+heat) → 8CO + 17H2
C7H8 + 7H2O (+heat) → 7CO + 11H2
Water-Gas Shift Reaction
CO + H2O → CO2 + H2 (+small amount of heat)
Great…. in the future you won’t need to close the garage door to kill yourself, just walk outside. At the very least this is yet another reiteration of an unsustainable carbon
based economy. There is another way, electrolysis using electricity.
In order to produce 1000 kg ofHydrogen (1 kg H2 has roughly the same energy density as a gallon of gasoline) you need to have 51,000 kWh of electric capacity. Spread over the course of 24 hours, that requires 2.125 MW of generating capacity, which is just within the limit of modern wind turbine technology.
GE Wind has largely abandoned the 3.6 MW model in favor of a larger model, but I’m going to use the wealth of technical information on their website to perform some extrapolations. In an area with Class 3 wind resource (generally considerd the threshold above which wind power is economically viable, about 6.4-7.0 m/s), the average annual production of a 3.6 MW model would be around 6 million kwh, or enough energy to produce 117,647 kgs of the equvalent of H2, the equivalent of the same number of gallons of gasoline.
The average fuel economy of all 2005 US vehicles is 21.0 Mpg. 2002 statistics show that the average American car traveled 12,200 miles annually, so that fueling a car for a year would require 581 gallons of gasoline or the same quantity of hydrogen, thus over the course of a year one of GE Wind’s 3.6 MW turbine at the low end of prdoduction capacity has the capacity to produce enough fuel for 200 vehicles, meaning that to fuel the nations fleet of 136 million passenger cars would take 680,000 3.6 MW turbines. That’s a lot of “windmills”, but it’s doable. Put another way in the 6% of US land area suitable for wind power development, that would equal out to just about 2 3.5 MW wind turbines per square mile. Tremendous potential, and one very big roadblock.
While hydrogen can be used as fuel in internal combustion engines, the great hope for hydrogen has been in conjuction with fuel cells
The proton exchange membrane fuel cell (PEMFC) uses one of the simplest reactions of any fuel cell. First, let’s take a look at what’s in a PEM fuel cell:
Figure 1. The parts of a PEM fuel cell
In Figure 1 you can see there are four basic elements of a PEMFC:
* The anode, the negative post of the fuel cell, has several jobs. It conducts the electrons that are freed from the hydrogen molecules so that they can be used in an external circuit. It has channels etched into it that disperse the hydrogen gas equally over the surface of the catalyst.
* The cathode, the positive post of the fuel cell, has channels etched into it that distribute the oxygen to the surface of the catalyst. It also conducts the electrons back from the external circuit to the catalyst, where they can recombine with the hydrogen ions and oxygen to form water.
* The electrolyte is the proton exchange membrane. This specially treated material, which looks something like ordinary kitchen plastic wrap, only conducts positively charged ions. The membrane blocks electrons.
* The catalyst is a special material that facilitates the reaction of oxygen and hydrogen. It is usually made of platinum powder very thinly coated onto carbon paper or cloth. The catalyst is rough and porous so that the maximum surface area of the platinum can be exposed to the hydrogen or oxygen. The platinum-coated side of the catalyst faces the PEM.
Fuel cells use platinum, an extremely rare metal that at $1068 per troy oz costs more than gold.
The scarcity of platinum has lead to concerns of shortages as fuel cells become more common.
The car industry is preparing for the day when oil wells run dry by investing billions of dollars to develop clean and efficient hydrogen-powered vehicles.
But the new fuel comes with its own built-in commodity crisis. Today’s experimental hydrogen fuel cells use so much platinum that there is not enough of the precious metal to replace all the world’s petrol engines.
At the current 60g or so of platinum in each fuel cell, the world’s 780m cars and trucks would use 46,800 tons of the metal – just below the 47,570 tons estimated to be still in the ground. And this assumes each vehicle has only 100 horsepower.
We’ve only got one world, and shortages are popping up everywhere. Then again if we think outside the box (and the atmosphere), and look to the sky, there are rich mineral deposits to be had: asteroids
Spectroscopic studies suggest, and `ground-truth’ chemical assays of meteorites confirm, that a wide range of resources are present in asteroids and comets, including nickel-iron metal, silicate minerals, semiconductor and platinum group metals, water, bituminous hydrocarbons, and trapped or frozen gases including carbon dioxide and ammonia.
As one startling pointer to the unexpected riches in asteroids, many stony and stony-iron meteorites contain Platinum Group Metals at grades of up to 100 ppm (or 100 grams per ton). Operating open pit platinum and gold mines in South Africa and elsewhere mine ores of grade 5 to 10 ppm, so grades of 10 to 20 times higher would be regarded as spectacular if available in quantity, on Earth.
Water is an obvious first, and key, potential product from asteroid mines, as it could be used for return trip propulsion via steam rocket.
About 10% of Near-Earth Asteroids are energetically more accessible (easier to get to) than the Moon (i.e. under 6 km/s from LEO), and a substantial minority of these have return-to-Earth transfer orbit injection delta-v’s of only 1 to 2 km/s.
Return of resources from some of these NEAs to low or high earth orbit may therefore be competitive versus earth-sourced supplies.
The big problem with space mining is that putting products into orbit and bring them back to Earth is extremely expensive. To get a pound of cargo into geosynchronous orbit (GTO), where permanent cargo transfer facilities are viable, costs at on the low end $7000 a pound.
There is a technology that is increasingly viable, that could dramatically reduce the cost of putting products and people into orbit:Space Elevators.
A space elevator is essentially a long cable extending from our planet’s surface into space with its center of mass at geostationary Earth orbit (GEO), 35,786 km in altitude. Electromagnetic vehicles traveling along the cable could serve as a mass transportation system for moving people, payloads, and power between Earth and space.
Current plans call for a base tower approximately 50 km tall — the cable would be tethered to the top. To keep the cable structure from tumbling to Earth, it would be attached to a large counterbalance mass beyond geostationary orbit, perhaps an asteroid moved into place for that purpose.
“The system requires the center of mass be in geostationary orbit,” said Smitherman. “The cable is basically in orbit around the Earth.”
Four to six “elevator tracks” would extend up the sides of the tower and cable structure going to platforms at different levels. These tracks would allow electromagnetic vehicles to travel at speeds reaching thousands of kilometers-per-hour.
Conceptual designs place the tower construction at an equatorial site. The extreme height of the lower tower section makes it vulnerable to high winds. An equatorial location is ideal for a tower of such enormous height because the area is practically devoid of hurricanes and tornadoes and it aligns properly with geostationary orbits (which are directly overhead).
Eventually costs could be reduce to the point that it would cost just $222 to put person into orbit. A lot of money for an elevator ride, but this is no ordinary elevator ride.
Liftport a private corporation based in Washington State, plans to have a working space elevator in operation by April 12, 2018, and while their estimated cost of $200/kg is higher than that offered by scientists at NAFTA, with high value products like platinum, this would be cost competive with terrestial mining operations. Estimates on costs for the project range from a low of $5 billion to a high of $10 billion. Considering the monetary and human costs of sustaining our petroleum based economy, this is a good investment, that could open the door to the resources of our solar system to our growing global population.
With a greatly reduced lifting cost, and the possiblity of space based shipyards, manned trips to Mars and beyond come into the realm of the possible. I’m not the only one who’s harping on this. Over on the dark side they seem to believe the progressives are too wedded to the promise of global warming as a way to kill capitalism to support a space elevator.
Why should Republicans propose building space elevators?
I admit it: part of the reason I want Republicans to make space elevators part of their 2006 campaign is that I am a Republican and fear that otherwise we will lose considerable power in the midterm elections. A space elevator proposal would be visionary, pro-defense, pro-environment and easy to understand, so it could attract significant support for Republicans.
It would be difficult for Democrats to enthusiastically support a space elevator proposal. The left-wing environmentalists view the threat of global warming primarily as a means of combating capitalism, and they would be horrified by any proposal that could reduce the harm of global warming without curbing commerce.
The Democrats would be uncomfortable with the militarization of space that U.S.-owned space elevators would allow. They would undoubtedly prefer that space elevators be built not by the U.S. but by some international coalition. Such Democratic opposition to a U.S. space elevator would allow Republicans to portray Democrats as being not only weak on defense but also hypocritical on the environment.
They’re right in that the militarization of space is a bad, bad idea, but they are dead wrong when they think that progressives are the anti-science crew. A space elevator, can and should be built, by an international coallition, the gang over on the dark side seem to have missed the detail that any viable space elevator would have to be built in the tropics, thereby making a completely US program impossible unless we intend to invade Venezuela. We’ll call this the target box, see anyplace else ripe for “regime change”?
Do you see French Guiana in there?
Seriously, the existing European Space Agency site in French Guiana, makes this area a good pick for a space elevator. It’s politically stable, and it’s in an area largely unaffected by hurricanes. And the symbolism of a Franco-American project (Euro-American?) to move beyond petroleum would be powerful. By sharing the cost between a variety of nations, the cost of a space elevator could be brought down to levels that can be sold to the public back at home. It may seem like a stairway to heaven or a pipe dream, but it is a viable opportunity if we as a nation (and planet) take the chance.
