Stepping on the (Hydrogen) Gas

Sixteen years ago Karl Ludvigsen set out his stall on the subject of hydrogen fuel for automobiles. Let's see if what he had to say passes muster in the 21st century.

For the late and much-missed Winding Road in 2006 I took a look at the use of hydrogen fuel in the past, present and future potential for motor-vehicle power. Taking another gander my effort, it still looks like a reasonable review. I’ll stick with my forecast of hydrogen as the best fuel for later in the 21st century because it can be made from so many sources of energy.

However I’m now convinced that we should set aside all thoughts of H2 as a suitable fuel for passenger cars. There’s no hope of having a dense network of hydrogen supplies akin to the one we’re try to establish for electric cars. It could and should be used for trucks, coaches and vans that have regular routes and return to their bases for refueling.

Nor do I believe that fuel cells are the answer. When I wrote my review, many auto and power-unit makers were finding ways to burn H2 in conventional engines. Last year’s Dewar Trophy was awarded to JCB, which has succeeded in using hydrogen as fuel for its industrial equipment. The real challenge was and is the storage of fuel, but there too we’re making progress.

So…here’s my fearless forecast from 16 years ago…

I said I’d scream if I saw another article about hydrogen as a fuel headlined “Stepping on the Gas”. Well, I’m screaming because I’ve created another one.

There have been quite a few such articles lately because industrial groups including car makers are building up pressure (there I go again) on the future use of hydrogen as a fuel not only for cars but also for many other purposes including home heating and power generation. Three main arguments underpin the case for hydrogen: pound for pound it’s the most energetic of all fuels, it can be made available in virtually unlimited quantities and when burned to liberate energy its emissions are harmless. Very compelling virtues these!

In our world of combustion engines the first practical use of this gas for fuel was in the power units of dirigibles held aloft by the buoyancy of hydrogen. Lighter-than-air engineers realized that burning some of the hydrogen from their gas bags would be an economic way of doing what they had to do anyway, namely reducing lift to compensate for the lightening of the ship as its regular fuel was consumed. Used in this way hydrogen could be a range extender.

First experiments in the 1920s with this technology were advanced in the early 1930s in Germany by Rudolf Erren, who successfully fed hydrogen to the diesel engines of dirigibles. With direct injection he overcame two of the fuel’s disadvantages: ultra-fast combustion that provokes detonation and backfiring into the inlet manifold. Erren’s research died with the loss of the Hindenburg in 1937 in flames at Lakehurst, New Jersey. Ending the age of the Zeppelin, the big ship’s conflagration was often blamed on its hydrogen-filled gas bags although flammable materials in and under its skin, ignited by current reaching the ground through damp ropes, were later found to be the more likely cause of its loss.

 British engine-combustion pioneer Harry Ricardo also conducted tests with hydrogen during the 1920s. Then when the Japanese fleet cut Australia off from its usual sources of fuel during World War 2 that nation’s scientists set to work on the adaptation of hydrogen to power its domestic vehicles. Before the war’s end they successfully ran prototypes with the new energy source.

In the early 1970s interest in hydrogen surged again although not as a primary fuel. Instead, researchers found that they could exploit its ability to burn at a wide range of fuel/air mixtures as an additive that permitted gasoline engines to run at “ultra-lean” mixtures and thus extend fuel economy in the midst of the Energy Crisis. This worked well, although the resulting hydrocarbon emissions were relatively high.

 Nudged by increasingly strict emissions limits, the next big push for hydrogen in cars came in the early 1990s. By 1991 hydrogen-powered Mercedes-Benzes had logged half a million miles of testing while BMW, Nissan and Mazda were evaluating the clean yet energetic fuel. Pound for pound hydrogen delivers almost three times the heat value of gasoline and six times as much energy as methanol. Its rotary engine, said Mazda, was exceptionally well suited to burn hydrogen by virtue of its leisurely combustion mode and its widely separated ports, which are less likely to ignite backfires.

 Although billed as “emissions-free”, car engines fueled by hydrogen do have one dirty-exhaust secret. With the atmosphere nearly 80 percent nitrogen, that gaseous element forms oxides at high temperatures in engines — the NOx that’s a proven contributor to smog formation. However if combustion temperatures are kept below 1,000°C or 1,800°F the rate of NOx creation is very low. This can be controlled by water injection or exhaust-gas recirculation.

Meanwhile another hydrogen-burning prime mover has been moving up in the fast lane. This is the fuel cell, first conceived as an “inexhaustible battery” in 1839 by English scientist William Grove. Not until the 1930s did work begin to create a practical fuel cell in the Cambridge laboratories of Francis T. Bacon. Soon after World War 2 Bacon demonstrated a workable cell generating five kilowatts of power. Running on hydrogen and oxygen, Francis Bacon’s concepts were used in the fuel cells that powered the Apollo missions to the moon.

As William Grove found, the fuel cell reverses the reaction that uses electricity to separate water (H2O) into Hydrogen (H2) and oxygen (O). Encouraged by catalysts, in the fuel cell the hydrogen molecules ionize and travel from a negative electrode through a membrane to the oxygen’s positive electrode. An external current between the electrode results. With oxygen present in 21 percent of the atmosphere and hydrogen accounting for one-ninth of the earth’s water, ample resources are available to feed such cells. And with nitrogen unaffected by the relatively low temperatures in such cells, their “exhaust” is pure water. The Apollo astronauts drank it.

 An important and inherent characteristic of the fuel cell is high efficiency. Claims vary but conversion efficiencies as high as 80% have been quoted. In practical cells the efficiency is in the range of 50-60%, far better than the 25-35% of internal-combustion engines. This is a powerful motivation for fuel-cell use, as is the inherent quietness of the devices — as long as the blower for the air supply is quiet enough.

In the early 1960s Allis-Chalmers was powering a tractor, golf cart, fork-lift truck and an underwater research vessel with its fuel cells. The first fully fledged fuel-cell road vehicle was GM’s Electrovan of 1966, which carried both hydrogen and oxygen on board in liquid form to power its Union Carbide cells.

With aerospace applications driving demand, the first such cells cost $400,000 per kilowatt. By the end of the 20th Century the cost had fallen to $10,000 per kilowatt. Though some currently claim fuel-cell costs as low as $15 per kilowatt, the cost of a complete system is still well in excess of the $50 per kilowatt that’s needed in order to contemplate rivaling the low-emissions internal-combustion engine.

To their credit, leading car makers have been contributing to the development of fuel cells suitable for cars. Several have been working with one of the pioneers, Canada’s Ballard Power Systems. Hydrogenics and UTC Fuel Cells are other developers.

General Motors, Toyota and DaimlerChrysler have led in making installations of these cells. Plowing its own furrow as it has done so often, Honda is not only building fuel-cell cars but also developing its own cells.

In 2006 two impressive advanced fuel-cell vehicles were unveiled: GM’s Sequel and Honda’s FCX Concept. The latter is a stylish successor to the humble-looking FCX of 2002, the first fuel-cell car to be certified as a zero-emissions vehicle by both EPA and CARB for commercial use. At the end of that year leased FCXs went into government service in Los Angeles.GM is producing a run of 100 Equinox SUVs with fuel-cell power and Ford has just unveiled a cell-powered Explorer for which it claims a world-record distance of 1,556 miles in 24 hours. More than 300 fuel-cell vehicles have already taken to the road. That number will quickly be doubled.

Two important challenges still face the makers of hydrogen-fueled vehicles whether they’re driven by fuel cells or by adapted engines. The first of these is the on-board storage of hydrogen. The classical method is as a gas compressed to some 5,000 psi, the equivalent of 350 atmospheres. This is the method most used in Japanese and North American fuel-cell cars, with both Ford and GM storing hydrogen at an impressive 10,000 psi, the latter using costly spun-carbon tanks in its Sequel.

Though staying at 5,000 psi, Honda says it has increased fuel capacity by putting a new-fangled hydrogen absorption material in its tanks. There are many such materials, for hydrogen readily forms affinities with certain metals and chemicals. Indeed, a long-favored storage method has been the use of metal hydrides, a method first reported on by the Brookhaven National Laboratory in the mid-1960s. Hydrides are the safest storage means but excruciatingly heavy for their capacity, which struggles to be better than 3% of their weight. Thus a hydride “tank” holding ten pounds of hydrogen weighs at least 350 pounds including its container.

While considering that hydrogen stored under pressure would be satisfactory for smaller cars, BMW rejects both that and hydride storage as being too heavy and bulky for larger vehicles. Like a spacecraft, its new Hydrogen 7 stores its fuel in liquid form at –253°C, only slightly above the –273°C of absolute zero. Its double-walled stainless-steel tank holds some 18 pounds of hydrogen, enough for a range of 125 miles in the big 7-Series sedan with its V-12 engine. Though gradual loss of the fuel occurs through its “boil-off” as a gas, the tank can retain its contents for a surprisingly long time. BMW also advocates the use of a small fuel cell to drive the car’s on-board accessories.

In Europe Ford is another advocate of this cryogenic storage system. Carrying their fuel in liquid form, examples of its fuel-cell Focus FCEV are in service in Berlin with a courier company. Partnering both BMW and Ford in fueling and delivery systems is Germany’s Linde, one of the major makers of hydrogen and its infrastructure. The chief executive of Linde? None other than Wolfgang Reitzle, former head of car development at BMW and one-time chief of Ford’s Premium Automotive Group.

            If a range of 125 miles for a big BMW doesn’t sound like much, it’s because the new model also runs on gasoline with a tank big enough for a range of more than 300 miles. Switching between the two systems is seamless, so the 100 prominent citizens in important markets who’ll be invited to lease these Bimmers won’t have to worry about being caught short of their next hydrogen fueling station.

            There aren’t many such stations yet, but their numbers are set to increase. You’re out of luck in Russia, Africa and South America but Europe and North America aren’t doing badly. There’s much still to be resolved between delivery in the form of a gas, a liquid or even the semi-solid slurry that holds future promise. Honda’s angle is a self-contained unit next to your house that makes hydrogen from natural gas for your car and also drives a fuel cell for home electricity and heating.

The source of the hydrogen is a hotly debated issue. Like electricity, hydrogen will always be a secondary form of energy that demands more energy to liberate it than it can deliver. Its advocates say that the renewable forms of energy generation can and should be used to generate hydrogen. Electrolysis by electricity from nuclear reactors was once the favored source and may indeed become so again.

Most compelling for the use of hydrogen as a vehicle fuel is its versatility. Never has the long-term outlook for fuel supply been so cloudy. We want and indeed need to step up our recycling and our use of renewables. Hydrogen is by far the most energetic fuel that can be made from everything, be it crude oil, coal, biomass, solar energy or wind. In the final analysis the ability of hydrogen to be generated from a vast variety of sources will speak most strongly for its role as the universal fuel for the second half of this century.

In September of 2004 at Miramas in the south of France BMW’s H2R record car established a portfolio of records in acceleration and maximum speeds for a hydrogen-fueled car. Driven by Alfred Hilger, Jörg Weidinger and Günther Weber, its fastest timing was 178.62 mph, just topping Europe’s magic 300 km/h. Its 232 bhp propelled it through the standing quarter-mile in 14.93 seconds. In the sleek lines of the H2R was a fresh challenge by BMW: the marriage of clean energy with sporting speed and dramatic style.

This was BMW’s hydrogen-fueled V-12 for a small series of cars for assessment. A more powervful version propelled the BMW record-setter.