Auto makers and independent designers have already built experimental cars that are ultralight or hybrid-electric but seldom both. Yet combining these approaches yields extraordinary, and until recently little-appreciated, synergies. Adding hybrid electric drive to an ordinary car increases its efficiency by about a third to a half. Making an ordinary car ultralight but not hybrid approximately doubles its efficiency. Doing both can boost a car's efficiency by about tenfold.
This surprise has two main causes. First, as already explained, the ultralight loses very little energy irrecoverably to air and road friction, and the hybrid-electric drive recovers most of the rest from the braking energy. Second, saved weight compounds. When you make a heavy car one pound lighter, you in effect make it about a pound and a half lighter, because it needs a lighter structure and suspension, a smaller engine, less fuel, and so forth to haul that weight around. But in an ultralight, saving a pound may save more like five pounds, partly because power steering, power brakes, engine cooling, and many other normal systems become unnecessary. The design becomes radically simpler. Indirect weight savings snowball faster in ultralights than in heavy cars, faster in hybrids than in nonhybrids, and fastest of all in optimized combinations of the two.
All the ingredients needed to capture these synergies are known and available. As far back as 1921 German auto makers demonstrated cars that were about twice as slippery aerodynamically as today's cars are. Most of the drag reduction can come from such simple means as making the car's underside as smooth as its top. Today's best experimental family cars are 25 percent more slippery still. At the same time, ultrastrong new materials make the car's shell lighter. A lighter car needs a smaller engine, and stronger walls can be thin; both changes can make the car bigger inside but smaller outside. The smaller frontal area combines with the sleeker profile to cut through the air with about one third the resistance of today's cars. Advanced aerodynamic techniques may be able to double this saving.
Modern radial tires, too, waste only half as much energy as 1970s bias-ply models, and the best 1990 radials roughly halve the remaining loss. "Rolling resistance" drops further in proportion to weight. The result is a 65-80 percent decrease in losses to rolling resistance, which heats the tires and the road.
Suitable small gasoline engines, of the size found in outboard motors and scooters, can already be more than 30 percent efficient, diesels 40-50 percent (56 percent in lab experiments). Emerging technologies also look promising, including miniature gas turbines and fuel cells—solid-state, no-moving-parts devices that silently and very efficiently turn fuel into electricity, carbon dioxide, water, and a greatly reduced amount of waste heat.
In today's cars, accessories—power steering, heating, air conditioning, ventilation, lights, and entertainment systems—use about a tenth of the engine's power. But a hypercar would use scarcely more energy than that for all purposes, by saving most of the wheelpower and most of the accessory loads. Ultralights not only handle more nimbly, even without power steering, but also get all-wheel anti-lock braking and anti-slip traction from their special wheel motors. New kinds of headlights and taillights shine brighter on a third the energy, and can save even more weight by using fiber optics to distribute a single pea-sized lamp's light throughout the car. Air conditioning would need perhaps a tenth the energy used by today's car air conditioners, which are big enough for an Atlanta house. Special paints, vented double-skinned roofs, visually clear but heat-reflecting windows, solar-powered vent fans, and so forth can exclude unwanted heat; innovative cooling systems, run not directly by the engine but by its otherwise wasted by-product heat, can handle the rest.
Perhaps the most striking and important savings would come in weight. In the mid-1980s many auto makers demonstrated "concept cars" that would carry four or five passengers but weighed as little as 1,000 pounds (as compared with today's average of about 3,200). Conventionally powered by internal combustion, they were two to four times as efficient as today's average new car. Those cars, however, used mainly light metals like aluminum and magnesium, and lightweight plastics. The same thing can be done better today with composites made by embedding glass, carbon, polyaramid, and other ultrastrong fibers in special moldable plastics—much as wood embeds cellulose fibers in lignin.
In Switzerland, where more than 2,000 lightweight battery-electric cars (a third of the world's total) are already on the road, the latest roomy two-seaters weigh as little as 575 pounds without their batteries. Equivalent four-seaters would weigh less than 650 pounds, or less than 850 including a whole hybrid propulsion system. Yet crash tests prove that such an ultralight can be at least as safe as today's heavy steel cars, even if it collides head-on with a steel car at high speed. That's because the composites are extraordinarily strong and bouncy, and can absorb far more energy per pound than metal can. Materials and design are much more important to safety than mere mass, and the special structures needed to protect people don't weigh much. (For example, about ten pounds of hollow, crushable carbon-fiber-and-plastic cones can absorb all the crash energy of a 1,200-pound car hitting a wall at 50 mph.) Millions have watched on TV as Indianapolis 500 race cars crashed into walls at speeds around 230 mph: parts of the cars buckled or broke away in a controlled, energy-absorbing fashion, but despite per-pound crash energies many times those of highway collisions, the cars' structure and the drivers' protective devices prevented serious injury. Those were carbon-fiber cars.
In 1991, fifty General Motors experts built an encouraging example of ultralight composite construction, the sleek and sporty four-seat, four-airbag Ultralite, which packs the interior space of a Chevrolet Corsica into the exterior size of a Mazda Miata. The Ultralite should be both safer and far cleaner than today's cars. Although it has only a 111-horsepower engine, smaller than a Honda Civic's, its light weight (1,400 pounds) and low air drag, both less than half of normal, give it a top speed of 135 mph and a 0-to-60 acceleration of 7.8 seconds—comparable to a BMW 750iL with a huge V-12 engine. But the Ultralite is more than four times as efficient as the BMW, averaging 62 mpg—twice today's norm. At 50 mph it cruises at 100 mpg on only 4.3 horsepower, a mere fifth of the wheelpower normally needed.
If equipped with hybrid drive, this 1991 prototype, built in only a hundred days, would be three to six times as efficient as today's cars. Analysts at Rocky Mountain Institute have simulated 300-400-mpg four-seaters with widely available technology, and cars getting more than 600 mpg with the best ideas now in the lab. Last November a four-seater, 1,500-pound Swiss prototype was reported to achieve 90 mpg cruising on the highway; at urban speeds, powered by its 573 pounds of batteries, it got the equivalent of 235 mpg.
Similar possibilities apply to larger vehicles, from pickup trucks to eighteen wheelers. A small Florida firm has tested composite delivery vans that weigh less loaded than normal steel vans weigh empty, and has designed a halved-weight bus. Other firms are experimenting with streamlined composite designs for big trucks. All these achieve roughly twice normal efficiency with conventional drivelines, and could redouble that with hybrids.
Hypercars are also favorable to—though they don't require—ultraclean alternative fuels. Even a small, light, cheap fuel tank could store enough compressed natural gas or hydrogen for long-range driving, and the high cost of hydrogen would become unimportant if only a tenth as much of it were needed as would be to power cars like today's. Liquid fuels converted from sustainable farm and forestry wastes, too, would be ample to run such efficient vehicles without needing special crops or fossil hydrocarbons. Alternatively, solar cells on a hypercar's body could recharge its onboard energy storage about enough to power a standard southern-California commuting cycle without turning on the engine.
Even if a hypercar used conventional fuel and no solar boost, its tailpipe could emit less pollution than would the power plants needed to recharge a battery-electric car. Being therefore cleaner, even in the Los Angeles air shed, than so-called zero-emission vehicles (actually "elsewhere-emission," mainly from dirty coal-fired power plants out in the desert), ultralight hybrids should qualify as ZEVs, and probably will. Last May the California Air Resources Board reaffirmed its controversial 1990 requirement—which some northeastern states want to adopt as well—that two percent of new-car sales in 1998, rising to 10 percent in 2003, be ZEVs. Previously this was deemed to mean battery-powered electric cars exclusively. But, mindful of hypercars' promise, the CARB staff is considering broadening the ZEV definition to include anything cleaner. This alternative compliance path could be a big boost both for hypercar entrepreneurs and for clean air: each car will be cleaner, and far more hypercars than battery cars are likely to be bought. By providing a large payload, unlimited range, and high performance even at low temperatures, hypercars vault beyond battery cars' niche-market limitations.
This result brings full circle the irony of California's ZEV mandate. Originally it drew howls of anguish from auto makers worried that people would not buy enough of the costlier, limited-range cars it obliges them to sell. The business press ridiculed California for trying to prescribe an impractical direction of technological development. Yet that visionary mandate is creating the solution to the problems. Like the aerospace, microchip, and computer industries, hypercars will be the offspring of a technology-forcing government effort to steer the immense power of Yankee ingenuity. For it is precisely the California ZEV mandate that radically advanced electric-propulsion technology—thereby setting the stage for the happy combination with ultralight construction which we call the hypercar.