Honda Es21
HONDA ES21
A SHOCKER FROM THE TOKYO MOTOR SHOW
KEVIN CAMERON
OUTDRAWING REALITY ITSELF AT THE RECENT Tokyo Motor Show was Honda's ES21 futuretech idea bike. Do you like food for thought? Here's a whole meal. Let's dine. The scanty official info says ES21 is powered by a hydrogen-fuel battery that drives a super-conducting electric motor. A double-arm front suspension/steering system is used, and Sbarrolike rim drive is implemented at the rear. Scan the swell color photo. It shows the single-shock front end, some kind of shiny rotating machinery just where you'd expect a swingarm pivot, twin air intakes flanking the front fender, and no evidence of brakes anywhere. It looks as though the bars and windscreen may slide on a track to provide variable riding positions. The size and type of tires (semi-slick) suggest 100 horsepower, and the aggressive styling shouts SPORTBIKE.
But the engineering called for doesn’t as yet exist. ES21 is a “what if’ exercise, but one based solidly upon technologies now in development.
Therefore let’s try to unravel Honda’s future-speak. Hydrogen-fuel batteries were first used in the U.S. space program in 1965, and they currently supply electric power on board the Space Shuttle. Without noise or vibration, a fuel battery uses the energy of its fuel, combining with an oxidizer, to generate electricity directly, without combustion. Present examples are 50-60 percent efficient-far moreso than gasoline engines at 25 percent. Remember demonstrating the electrolysis of water in high school chemistry? Electric power flows into one electrode, through water to another electrode, and in the process supplies energy to separate the hydrogen and oxygen out of the water. A hydrogen fuel cell (many cells make a battery) is simply electrolysis in reverse; put in hydrogen (and oxygen from the air) and get out electricity. No noise, little heat, zero pollution.
Where will the hydrogen come from? We aren’t told, but futurists predict an economy fueled not by electricity, but by hydrogen, set free from water by electrolysis driven by some other plentiful, cheap source of power. Unfortunately, at present this conversion is only 60 percent efficient, and power to make hydrogen is neither plentiful nor cheap. However, hydrogen might become competitive in some future time.
How would ES21 carry it? Compressed in high-strength pressure vessels, hydrogen is, as they say, “huge.” Even in the ultra-cold liquid form preferred as rocket fuel, hydrogen occupies four times the volume of an energy equivalent of, say, gasoline. Is that what we are to believe lies concealed within ES21’s bulbous red forebody? Hydrogen storage as a metal hydride is prohibitively heavy, but attractively safe-hydrogen is easily ignited and bums fast. Other types of fuel cells may be able to use more familiar liquid fuels-alcohols or hydrocarbons.
The fuel battery’s electrical output is then sent to ES21’s superconducting motor, the shiny end of which we are presumably seeing in the photo. The forces driving electric motors are magnetic, and when you try to make a motor more powerful by increasing magnetic field strengths inside it, you reach a limit; the iron core material, used to intensify the magnetic field, reaches magnetic saturation, preventing further field strength increases. The trick way around this is to do away with the core and create the fields with coreless solenoids, carrying extremely high
currents. Another limit appears; copper wires don’t like to carry more than 400 amperes per square centimeter. More than that and they require fancy cooling that defeats the exercise.
Answer? Superconductivity. Certain materials, at very low temperatures, suddenly cease to offer any resistance to electric current. This is superconductivity, which eliminates resistance and heat, so conductors can carry far more current, generate far more intense fields. Small motors could then deliver big power. Superconducting motors and generators have been built, but their superconductors require cooling to near absolute zero by expensive, hard-to-handle liquid helium. But, as it happens, superconductor materials that work at higher temperatures are a hot development in current science; now there are ceramic superconductors that offer zero resistance at 125 degrees K above absolute zero (still about a zillion degrees below Christmas in Montana), but able to be cooled by cheap liquid nitrogen.
The more optimistic researchers-and ES21’s creators-hope that some day soon, someone will devise practical room-temperature superconductors.
And now the rim drive. The rear wheel is shown grasped at its front edge by a screwdotted black “paw,” and there are two other round things spaced around the rim’s inner edge. I think the whole interior of the wheel is non-rotating, and carries the rim on three rollers (two of which are visible). The paw contains the rim-drive “sprocket,” which engages teeth on the inner surface of the rim, unseen by us. A similar affair is shown at the front. Does ES21 have two-wheel drive? Why so trick? Here’s one idea: regenerative braking. With present-day friction brakes, we convert vehicle kinetic energy into heat and throw it away. But ES21 may stop by reversing its electrical cycle; to stop, the motor(s) become generators, sending power back to the fuel cell.
ES21 represents imaginary engineering, but the concepts involved are all real-world developments now in work. We may not be riding bikes when and if room-temperature superconductors and lightweight, cheap fuel cells and their fuel arrive. Nevertheless, Honda is telling us there is hope. We hear a lot of frightening talk lately about how maybe soon we’ll be forced to drive politically correct, no-fun electric cars with 20 horsepower and 2000 pounds of short-lived batteries on board. We get the idea the future is a good place to avoid. Maybe not. The very forces that provide energy in today’s gasoline-powered vehicles are themselves electrical-the bonds that hold fuel molecules together.
Present-day vehicles release this energy by combustion, but Honda is reminding us that there are other ways to do this that may one day bring us far more efficient, largely pollution-free machines that are just as much fun to ride as today’s best sportbikes. □
