Dr. Red
9th Jan 2001, 05:48
Most big motor companies seem to have an "alternative fuels" division. Whether this is serious or just to appease environmentalists remains to be seen.
The following (largeish) article from New Scientist is a semi-relevant discussion of alternatives to the internal-combustion engine.
<font face="Verdana, Arial, Helvetica" size="2"> Petrol. We can't live with it, we can't live without it. Burning it in the engines of our cars causes pollution and global warming. It shackles us to unstable Middle Eastern countries. And one day it'll run out. But we're hooked. As recent protests in Europe over the price of fuel have shown, shut off the supply and countries grind to a halt. We need a cleaner, greener fuel, and lots of it. Here it is...
THEY'RE calling it the "Bahrain of the North". These are exciting times in Iceland, the birthplace of the hydrogen economy. Thorsteinn Sigfusson, professor of physics at the University of Iceland in Reykjavik and chairman of Iceland New Energy, says that within 20 years his country can become the first in the world to run on hydrogen without recourse to fossil fuels. To start with, hydrogen will run its fleets of buses, trucks, cars and trawlers, and later it will provide electricity and heat its buildings through the long winters. Iceland could be the first of the 21st-century successors to the OPEC sheikhdoms. Call them HYPEC--the organisation of Hydrogen Producing Countries.
It's early days yet, Sigfusson admits. The first three hydrogen-fuelled buses won't hit the streets of Reykjavik until 2002. That's several years after Vancouver and Chicago introduced theirs. But Iceland's buses are the start of something much bigger. Unlike most hydrogen-powered buses, which fill up with hydrogen derived from old fuels such as oil, Reykjavik's buses will run on hydrogen made by splitting water, using hydroelectricity generated from Iceland's raging rivers. The umbilical cord to fossil fuels will be cut.
Since Iceland has a population of only 276,000, and you can't drive there from anywhere else, it is an ideal place to test out a future world where cars are no longer environmental pariahs, where urban smogs and greenhouse gases are banished. A world, in short, that has kicked the carbon habit.
Ask anyone with a stake in the energy economy if the revolution is really necessary and they will say yes. There are compelling reasons for change. Emissions of carbon dioxide from internal combustion engines are stoking the greenhouse effect. (See our Special Report on Global Warming, www.newscientist.com/global)Burning (http://www.newscientist.com/global)Burning) oil fills our cities with smogs that kill hundreds of thousands every year. Technological improvements to cut emissions from conventional cars cannot keep pace with the rising tide of vehicles. There will probably be a billion on the world's roads by 2020--one for every seven people.
Meanwhile, the oil economy is starting to give us a bumpy ride. Nations the world over remain shackled to OPEC--a risky position to be in, as the price hikes of the past six months have shown. It doesn't take much to rock a government and threaten global recession. And one day the oil will run out. Oil geologist Colin Campbell was quoted in New Scientist last year as saying that "the world's oil companies are now finding only one barrel of oil for every four that we consume"
Even big oil companies now concede that we cannot carry on burning oil as we have in the past. "If the motor car is to stay with us, we need to explore radical new ways to fuel it," says Paul Histon, fuels technology manager at BP Amoco's oil technology centre in Sunbury-on-Thames near London. "If we are truly to get big CO2 reductions, hydrogen is the best long-term choice."
Why hydrogen? Well, it's ubiquitous, inexhaustible and clean. You can drive across the US on hydrogen without adding to the atmosphere anything more noxious than a bathtub-full of water. Back in 1874, Jules Verne argued in The Mysterious Island that when fossil fuels run out, hydrogen "will furnish an inexhaustible source of heat and light". Hydrogen's time seems to have come.
But is it safe? Some industrialists argue that storing hydrogen on filling station forecourts or in vehicle tanks is too dangerous. The image of the 1937 Hindenburg airship disaster still looms large. This is curious. The hydrogen filling the airship did not explode, and the 35 dead were either killed by burning diesel or jumped to their deaths. In 1997, a retired NASA scientist found that the real culprit was the flammable fabric of the airship's outer skin, not the hydrogen (!).
And let's not forget that cars are already carrying round tanks of dangerously explosive liquid, so it's really a question of comparative risk. Hydrogen is easy to ignite, but it's buoyant and dissipates rapidly. And if it is caught in a confined space, it requires more oxygen to burn than oil does. "Hydrogen is less hazardous than gasoline," says Amory Lovins of the non-profit Rocky Mountain Institute in Colorado, which specialises in the future design of cars.
The key questions today are not so much "Do we want a hydrogen economy?", as "What sort of hydrogen economy do we want, and how do we get there?" Do we make the new wonder-fuel from petrol, natural gas, methanol, biomass or water? Do we make it in centralised hydrogen factories, on the forecourts of service stations or under the bonnet? How do we store it? And do we put it in conventional internal combustion engines or fuel cells?
The world's biggest car makers are busy drafting a road map to the hydrogen-fuelled future. But nobody yet seems sure of the way. BMW is betting on an internal combustion engine that burns hydrogen, claiming it's the only way to deliver the acceleration and responsiveness drivers are used to. But most believe that the internal combustion engine, with its Heath-Robinson assembly of transmission and drive shafts, is too inefficient. It converts barely 20 per cent of its fuel's energy into traction. Electric engines can have an efficiency of up to 80 per cent. But batteries don't deliver enough power for their weight and need frequent recharging. So attention is increasingly focusing on electric engines without batteries.
Plan A, the so-called hybrid engine, has already been on Japanese roads for three years, under the bonnet of Toyota's Prius model. It's a petrol-burning engine hooked up to an electric motor. The engine doesn't drive the car directly, but generates electricity, which is stored in a battery and released as necessary to drive the car. So the petrol engine can always operate at its most efficient speed, rather than surging or slowing to the demands of road and driver. Result: fuel savings of 10 to 20 per cent and similarly reduced pollution. It's a start.
Further improvements could be made if the engine burnt a cleaner fuel. But the smart money is on something more radical. That something was invented way back in 1839 by Welsh physicist Sir William Grove: a fuel cell that runs on hydrogen.
Many types of fuel cell have been developed over the years (see "Fuelling the future", p 38). But until recently they were too large, cumbersome and low on power to run a car--even after NASA tinkered with them to provide pollution-free electricity inside the Apollo spacecraft.
The breakthrough came in the mid-1990s when a small company, Ballard Power Systems of Vancouver in Canada, dramatically improved their power-to-volume ratio. Up to that point, fuel cells delivered around 167 watts per litre. A car engine built with these would commandeer the entire boot and back seat. Around five years ago Ballard achieved 1000 watts per litre. For the first time, fuel cells could fit under the bonnet. The company's latest cell, the "Mark 900", delivers 1310 watts per litre, powerful enough to make a 75 kilowatt (100 brake horsepower) engine that fits comfortably inside a car.
Soon fuel cells will be on the highways. Ballard vice-president Paul Lancaster promises that by 2004 a quarter of a million fuel cells will be rolling out of its $400 million production plant every year. And he has development deals to put them in cars made by Ford, General Motors, Toyota, DaimlerChrysler, Nissan and Honda.
Ferdinand Panik, director of DaimlerChrysler's fuel-cell project in Germany, reckons hydrogen fuel cells will power a quarter of new cars worldwide by 2020. It could be a lot sooner, especially now oil companies are lining up too. Shell gave its blessing last March when Don Huberts, chief executive of Shell Hydrogen in Amsterdam, predicted hydrogen would be the world's number one fuel in the 21st century.
Ballard's proton exchange membrane fuel cell converts fuel into power twice as efficiently as an internal combustion engine while producing no noise or noxious emissions. No wonder hydrogen fuel cells have a green halo. British transport minister Gus MacDonald declared in December last year that fuel cells would allow more than half of new British cars to be "pollution-free" within a decade. But hang on a moment. Fuel cells are a major advance because they are a more efficient way of powering a vehicle. But "pollution-free" they are not.
This is what we might call the "electric kettle problem". Fuel cells, like electric kettles, emit only steam. But kettles are powered by electricity generated in power stations that burn coal or oil. And fuel cells are powered by hydrogen made by . . . well, by what? You cannot mine hydrogen or pluck it from the air. It has to be manufactured. And the method of manufacture determines the pollution. "If we make hydrogen from the wrong fuel source, such as gasoline, the green halo could vanish," says Rob Macintosh of the Pembina Institute for Appropriate Development in Alberta.
There are two main ways of producing hydrogen. The first is electrolysis, passing an electric current through water to split it into hydrogen and oxygen. This requires large amounts of electricity, most of which is generated by burning fossil fuels such as coal or oil. Use this to run a car and there's little, if any, gain. To make environmental sense, the electricity has to be generated from renewable resources (see "Make hydrogen while the Sun shines").
The second route to hydrogen is to refine it--either from a conventional hydrocarbon or a novel source such as plant matter. This refining, or "steam reforming", can be done in a number of ways: centrally at a refinery for delivery by pipeline to service stations; at the filling station itself, using hydrocarbons trucked or piped in; or on-board the car in a small "reformer" that directly supplies the fuel cell. In each case, reforming combines a hydrocarbon and water at high temperatures to produce carbon dioxide and hydrogen. The trick, in environmental terms, is to choose a hydrocarbon that produces maximum hydrogen for minimum carbon dioxide. Natural gas, which is mostly methane (CH4), is the best because it has the highest possible hydrogen-to-carbon ratio.
There are other potential methods of hydrogen manufacture, such as mimicking photosynthesis, using heat or high-energy particles to split water, or even harnessing bacterial enzymes. But all are still largely confined to the lab. Reforming natural gas, however, is already widely used in the production of chemicals.
But which of the options would be best for the environment? Macintosh accepts that "to be truly pollution-free, the hydrogen must come from a renewable source, such as solar or wind power". The green dream of electrolysis using a renewable energy source is technically feasible, but not yet economically viable. So Macintosh has analysed available technologies, using the test of how much greenhouse gas would result from making and using the fuel needed to drive a standard vehicle--a Mercedes A-class hatchback--on a 1000-kilometre drive across Canada.
Worst, not unexpectedly, was the regular gasoline-burning car. It emitted 248 kilograms of CO2, most of it in the exhaust gases. Next worst was a fuel-cell car with an on-board reformer that turned gasoline into hydrogen. This so-called "pollution-free" vehicle chalked up 193 kilograms, mostly from the reformer. After that came on-board reforming of methanol, the chemical many fuel-cell pioneers see as the most likely route to mass-produced fuel-cell cars. In Macintosh's study, methanol outperformed gasoline, producing 170 kilograms of CO2. But it lagged way behind the vehicles carrying hydrogen made from natural gas reformed either on forecourts or at a central facility. These emitted between 70 and 80 kilograms of CO2-- 70 per cent less than gasoline. Macintosh only looked at greenhouse gas emissions, but he reported that smog-creating emissions would show a similar profile.
Even if the problem of hydrogen generation is cracked, there are still roadblocks between here and a hydrogen economy. One is storage (see "Where to keep it"). Another is the need to create a new infrastructure for producing and distributing bulk hydrogen, costing perhaps trillions of dollars. This looks especially problematic, but there are potential solutions.
One is kick-starting the hydrogen economy in smog hot spots, such as southern California, or in areas of abundant "green" energy for hydrogen production, such as Iceland. Another is to make the transition in stages, perhaps by concentrating first on fuel-cell vehicles with on-board hydrocarbon reformers.
But which hydrocarbon would make the best stepping stone? Much of the car industry favours methanol. The argument is that methanol is a liquid, so is easier to manufacture and handle in bulk than hydrogen while still offering significant environmental advantages over oil.
Last year, Ballard signed a deal with Methanex of Vancouver, the world's largest methanol producer, to set up a prototype distribution system in Canada. Ballard is backing a similar project in the US along with the California Air Resources Board, Ford and DaimlerChrysler.
Macintosh, though, says this is misguided. "Unfortunately, on-board processing of methanol fuel does not offer anything near to the life-cycle greenhouse gas advantage of natural gas reforming," he says. It also requires a whole extra stage of manufacture, a reformer in every car, and its own distribution and storage systems. Methanol is corrosive so would have to be held in reinforced tanks. It's also water soluble, which means leaks into groundwater would be hard to contain. Paul Histon of BP Amoco fears setting up a system for shipping methanol round the country, only to have to move again to a hydrogen distribution system a few years later. "We only want one big change," he says. "If it's going to be hydrogen, let's get on and do it."
The logical solution, argues Macintosh, is for cars to fill up with hydrogen produced on garage forecourts from natural gas. This is cheap, because the natural- gas distribution network is already in place. It is the most environmentally friendly technology currently available. And it is very easy. Indeed, you might not even need filling stations. Your office or neighbourhood could do it (see "Fill 'er up"). A reformer the size of a water heater "can produce enough hydrogen to serve the fuel cells in dozens of cars", says Amory Lovins. The scenario is also flexible. As demand grows, bulk suppliers of hydrogen might get interested, developing pipeline networks if they felt they could undercut local production.
Natural gas, says Lovins, offers "a long bridge to a fully renewable energy system". And there could be unexpected bonuses along the way. Robert H. Williams of Princeton University's Center for Energy & Environmental Studies, sees potential for the owners of gas fields turning their product into hydrogen at the wellhead. That way, the resulting CO2 emissions could be injected right back into the emptying well.
But journey's end will be a true hydrogen economy, in which the link to fossil fuels has been cut for good. Greens and industrialists alike are beginning to glimpse the day when renewable energy--whether solar or wind, geothermal or hydroelectric--is ready to take over electrolytic production of hydrogen from water. Indeed, manufacturing hydrogen may turn out to be the most effective use of renewable energy. For it gets round the inconveniently intermittent nature of many sources--available only when the wind is blowing or the Sun is out. Hydrogen will, in effect, be able to store that energy.
Lovins sees hydroelectric dams, in particular, becoming "hydro-gen" plants. They have the unique advantage of bringing together abundant water and electricity supplies and could "earn far higher profits by selling not electricity but hydrogen--in effect shipping each electron with a proton attached".
This strategy even gets round one of the major problems of hydroelectricity--the need to flood large areas of land to store water. Reservoirs are only needed so that electricity can be generated on demand. But the need disappears if that electricity can be generated "at nature's convenience"--varying according to rainfall--and its energy stored as hydrogen. Large reservoirs could be replaced in many places by "run-of-river" hydroelectric plants that take power from passing water without damming it.
The hydrogen age could be closer than we think. Certainly, the route map is slowly emerging. But who will get on the road first? Right now, revving up at the front of the grid is the country with one of the largest hydroelectric reserves in the world. Plucky Iceland.</font>
So how could this technology be adapted for aircraft?
SRR99
10th Jan 2001, 18:22
Or how about the nuclear alternative that GE started development of? (1950s)
The idea was to use a heat exchanger in the combustion chamber.
Think I'm joking? Think again.
I believe it was called the XB-211 - similar to another engine I can think of.
Just imagine, aircraft able to stay in the air for weeks at a time - bliss. As long as you have life in the turbine blades etc, you can stay up. OK, so the shielding might be a tad heavy, and "heavy landings" might cause a bit of fall-out, but that's a real nuclear deterrent.
Flight Safety
12th Jan 2001, 21:41
The ideal ultra-green hydrogen cycle for autos would be something like this I think:
A desalinization/demineralizing plant on the coast pumps distilled quality fresh water to a solar water splitting plant in a location with lots of annual sunshine. The minerals extracted from the sea water are then sent back into the sea, preferably in an area with good sea currents so there is good mixing and the minerals do not concentrate.
The solar powered water splitting plants then produce the hydrogen for distribution, and either release the oxygen into the atmosphere, or sell it for medical or industrial uses. The existing energy companies (who may own and run the water splitting plants) provide the infrastructure to store and distribute the hydrogen, since they know how to build and operate such an infrastructure from their hydro-carbon experience.
Autos, buses, trucks, and trains use something like the high efficiency Ballard fuel cells to generate electric power for use in mechanical locomotion. Oxygen taken from the atmosphere combines with the hydrogen in the fuel cell producing distilled steam-water as the only chemical by-product. The steam-water is then cool-condensed and collected in a storage tank within the vehicle for periodic dumping at designated dumping stations.
Why is this scenario ultra-green?
Water supply: Inexhaustable
Solar energy: Inexhaustable
Ultimate energy source for the complete hydrogen cycle: The Sun
Net effect on the oceans: zero
This is because the fresh water produced in the fuel cells eventually will end up back in the earth's water cycle and back into the oceans. There will be no mineral buildup in the oceans since the fresh water will eventually return there.
Net effect on cities: zero plus
The steam-water from the fuel cells will have to be collected and dumped since a large city with large urban traffic would become a sauna without this. The water collection and dumping would also provide an alternative source of fresh water which might be handy in desert communities.
Net effect on the oxygen content of the atmosphere: zero
Oxygen released (or sold) from the water splitting plants when eventually released into the atmosphere, would balance the oxygen used in the fuel cells.
Net thermal effect on the earth's environment: zero
The solar heat that would have been released by sun warming of the ground (but is used instead in the water splitting), will eventually be released in the fuel cells, steam-water and electrical locomotion, since all the energy released will eventually end up as heat.
Net chemical effect on the atmosphere: zero
No chemical pollutants would be released into the atmosphere from this process.
The issues with airplanes have to do with the weight density of hydrogen and the strength of the pressure vessels required to store it.
I understand that while hydrogen has about twice the BTU's available per pound as either gasoline or Jet fuel, it's also much lighter in liquid form and thus requires more volume to store for a given weight. Also hydrogen has to be stored at a high pressure to remain liquid, especially at altitude. This requires thick walled fuel tanks which would add weight to an aircraft. Obviously a fuel cell would never work in anything other than a very light aircraft, so a hydrogen fueled turbine would have to used.
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Safe flying to you...
[This message has been edited by Flight Safety (edited 12 January 2001).]
Squawk 8888
13th Jan 2001, 04:28
One little problem with that scenario- it is impossible to store large quantities of hydrogen in a tank for extended periods of time, because the H atom is so tiny it can pass through just about anything. The only practical storage method is the use of metal hydrides, which break down and release hydrogen when heated. The rate at which the hydrogen is released is too slow to support a combustion engine, so the only choice (for now) is the fuel cell.
EchoTango
13th Jan 2001, 11:48
There is ABSOLUTELY no substitute for the gasoline base fuels we have for our mobile transport - especially aircraft and automobiles. The energy carrying and energy releasing properties of 8 to 12 carbon atom alkane hydrocarbons are simply the best.
Hydrogen is a nice fuel, but very difficult to manage. Storing it as a hydride, or adsorbed on some material will give you the same problems as battery powered cars - weight, space and low range.
Gas stations that make hydrogen on site are a nonsense, especially when they talk about using petroleum as the raw material. Where does the carbon go ? Back to a power station so they can burn it to make the buckets of additional energy needed ? Then the carbon goes up the stack as CO2 ?
Do some simple arithmetic on my small local gas station.
Lets say he has 3 customers filling at any time for 8 hours per day, 7 days per week, and none in the other 16 hours. It takes about 5 minutes to fill a tank, and I use a very modest 40 litres/week.
So that gas station supports 672 customers like me, and uses 26,880 litres/week. (A bit less than one full tanker per week).
The heat of combustion of hydrogen is 33,887 cal/gram
The heat of combustion of n-octane (gasoline, more or less) is 11,500 cal/gram
Lets say the gas station keeps the hydrogen in its most dense form. Liquid hydrogen has a specific gravity of 0.0709 at -253 centigrade. Gasoline is near enough 0.8.
So if the conversion efficiency (fuel energy to power on the road) for a hydrogen fuelled automobile is the same as a gas powered one, the gas station must make an average 26,880 * (11,500/33,887) * (0.8/0.0709) = 102,930 litres of liquid hydrogen per week.
That sounds absurd. Lets say the hydrogen engine is 10 times as efficient as the gas one. Now the gas station has to make only 1,470 litres/day. If he wants to store 2 days worth to cater for downtime while his plant is serviced, he has to store 2,940 litres or 648 Imp. gallons. And he will need BIG "No smoking" signs.
That bit of arithmetic is extraordinarily optimistic in many ways. By the time you go to hydride storage, then add in the energy requirements needed to crack the H20 and compress it, you will strike insurmountable problems.
Solar cells can't drive practical automobiles (as we now know them). Maximum power solar power flux is (I think) about 1kw/ sq metre. If we say 50% conversion efficiency to power on the road, my little automobile, pottering along with granny driving it at a mere 10kw power on the road, airconditioning off, will need a 2 x 10 metre solar panel on the roof. It will need auto spoilers on it if granny goes too fast coasting downhill.
Solar panels will no longer be reasonably cheap to make when the raw materials (purified silica, metals, glass and plastics) have to be made with the power produced by solar cells, and without the benefits of petroleum and its byproducts.
Metals (Steel, Aluminium, Copper etc), while themselves a depleting resource, will become expensive commodities as the things which make them from their ores (coal, oil, power) dwindle. (Notice how Aluminium smelters like to be near hydro power ?)
Hydroelectric power is good, but limited. Does serious damage to the downstream area. Floods a few people.
Nuclear (fission) energy is no use in airplanes and automobiles (except via the hydrogen route), and is understandably not too popular.
Wind and tide power won't drive airplanes and automobiles (Blaniks and the like will never be a people mover)
Iceland would be a good property investment from an energy cost point of view (thermal).
Nuclear (FUSION) has some promise, except they can't do it.
So all you lucky people swanning around in your Boeings, Airbusses, Harriers (have I missed anyone important ?), enjoy your flight. Gasoline, Avgas and Avtur resources are finite. They will run out. The end is nigh.
But I think you have time to get home before the fuel runs out, and have a G&T. I am about to pour my third.
ET
[This message has been edited by EchoTango (edited 13 January 2001).]