For MORE information on Hypercars see www.hypercar.com.
RMI has coined the term "Hypercar" to describe a conceptual vehicle that combines ultralight and ultra-aerodynamic design, a hybrid-electric drivesystem, and other features to achieve very high fuel efficiency and very low emissions. Modeling by RMI (Rocky Mountain Institute) suggests that full-sized Hypercars should be able to get 90 miles per U.S. gallon of gasoline or equivalent (2.6 L/100 km) in the near term and 200 mpg (1.2 L/100 km) in the long term. How this is possible is explained in the next answer.
Uniquely, the Hypercar concept achieves high efficiency without sacrificing important vehicle characteristics such as safety, performance, affordability, durability, and comfort. Because Hypercars are intended to be equal or superior to conventional vehicles in every significant respect, their success in the marketplace need not depend on the support of the minority of buyers who care about fuel efficiency.
A car's fuel economy can be improved by reducing any or all of the following:
Minimizing these losses piecemeal is good, but redesigning the entire car for maximum overall efficiency—taking an integrated, "whole-system" approach—is much better.
The Hypercar concept is based on a combination of ultralightweight and aerodynamic design, hybrid-electric propulsion, special low-rolling-resistance tires, and efficient accessories. Separately, these demonstrated features yield only modest improvements in fuel economy, and each has attributes that have prevented it from being widely adopted by the auto industry. But combining all of them in a whole-system approach captures impressive synergies, multiplying the fuel savings and avoiding the disadvantages of each. Some of these synergies are described below.
Ultralight Construction
Vehicle mass is a critical factor to minimize because it affects power requirements, overall drivesystem efficiency, tire rolling resistance, and the amount of energy used to accelerate that is later lost in braking. Ultralightweight design can be accomplished without making the car any smaller or less safe by replacing steel with new materials, such as advanced polymeric composites, in the car's body and chassis.
Making a component lighter allows for others to be made lighter as well. This principle is called "mass decompounding." For example, reducing the weight of the body allows the engine to be fractionally less powerful for equivalent performance. It also allows the car's transmission and other drivetrain components to be slightly smaller because they don't have to transfer as much power to the wheels. All these mass reductions in turn allow the car's body and suspension to be even lighter because it won't have to support as heavy an engine, etc.
Obviously, mass decompounding has a limit, but the limit is much lower than might be expected, because reducing a car's mass below a certain threshold makes possible new options and even the elimination of some systems altogether. For instance, a car that's light enough can utilize unconventional lightweight and efficient drivetrains and do without power steering. All told, it should be possible to make Hypercars that are 50-65 percent lighter than conventional cars of the same size.
Aerodynamics and Rolling Resistance
Today's cars are already fairly sleek, but aerodynamic drag can be further cut by 40-50 percent or more through cab-forward design, a smooth underbody, a tapered rear end, minimized body seams, and aerodynamically designed air intakes, suspension, and wheel wells. These improvements could be achieved without significantly restricting the stylist's freedom to make attractive and distinctive-looking cars. Large improvements could be made by just smoothing the underbody, which is essentially invisible.
Rolling resistance is affected by the mass of the vehicle, the type of tires, and the amount of friction in the bearings and idle brakes. In addition to minimizing the vehicle's mass, special tires, wheel bearing assemblies, and brakes can be employed to reduce overall rolling resistance by more than 50 percent. Such changes would be mostly transparent to the driver, since low-rolling-resistance tires are designed to provide traction and durability comparable to conventional tires.
Hybrid-Electric Drivesystem
Another of the Hypercar's key divergences from today's cars is its drivesystem. Conventional automotive drivesystems consist of an internal combustion engine (ICE) mechanically coupled to the drive wheels through a multi-speed transmission. Such a drivesystem's efficiency suffers from having to operate over a wide speed and power range. The engine can be tuned to operate efficiently under specific operating conditions (say, at constant highway speed on a level road with two passengers), but it must be run far from this "sweet spot" of efficiency much of the time. The engine's efficiency is further impaired because it must be grossly oversized so that it can accelerate the heavy steel vehicle quickly.
To improve the efficiency of converting fuel into traction at the wheels, the Hypercar would use a hybrid-electric drivesystem. Like a battery-electric car, a hybrid-electric car is powered by an electric motor or motors, but the electricity, rather than being drawn from batteries recharged from the grid, is generated onboard with a small engine or other device. This offers two big advantages over a battery-electric car: the hybrid car doesn't have to haul around hundreds of pounds of batteries, nor is its range limited by the need to recharge them.
The hybrid-electric drivesystem also has at least two big advantages over conventional ICE systems. First, the engine (technically called the auxiliary power unit, or APU) runs over a smaller range around its most efficient operating point, and can even be turned off when not needed. Any extra power required can be provided by a small electrical buffering or load-leveling device (LLD). The engine can either be coupled directly to the wheels, as in today's cars, or be connected to a generator that produces electricity for separate electric motors connected to the wheels. The first case is called a parallel hybrid because both the APU and one or more electric motors drive the wheels simultaneously. The second is called a series hybrid because the APU, motor(s), and wheels are connected in series—the APU produces electricity for the motor(s) and keeps the LLD charged, and they in turn power the wheels, but the engine has no mechanical link to the wheels.
A second advantage of hybrids is that they can recover part of the braking energy that would otherwise be lost as heat in the brakes. Some experimental vehicles have demonstrated up to 70 percent peak energy recovery, but recovery of about 50 percent is seen by many experts as a more realistic goal. Hypercars would probably still use conventional brakes, but much less, so they'd last longer.
Accessory Loads
Currently, little attention is paid to designing cars for minimized heating and cooling loads or making their accessories energy-efficient. But in a Hypercar, where the power needed for propulsion is minimized, standard accessory loads would become an important part of total power consumption. Through careful choice and integration of efficient components, however, the accessory loads could be reduced to no more than about one-fourth of the current average, while providing equivalent or better functions.
For a more detailed technical discussion of these concepts, see the RMI publication "Vehicle Design Strategies to Meet and Exceed PNGV Goals,".
The fundamental thesis underlying the Hypercar concept is that high fuel efficiency and low emissions can be achieved without compromising the car's marketable features (such as performance) and without imposing burdensome constraints on its body styling. RMI bases its fuel-efficiency modeling on a vehicle that would perform equivalently to, or better than, a current five-to-six-passenger touring-class sedan, such as the full-featured versions of the Ford Taurus, Chevrolet Lumina, or Chrysler Concorde.
While some changes would be required to improve aerodynamics, the body designer would still have significant stylistic freedom. Features like thinner body seams, a smooth underbody, recessed windshield wipers, and flow-optimized air intakes and wheel wells would be relatively transparent to the user, but could significantly lower the car's aerodynamic drag. Further changes such as partially covered wheel wells, cab-forward design, and a tapered rear end would also lower drag, and could be implemented to the extent that they are accepted by consumers.
The Hypercar's aerodynamic body design would enable it to achieve high speeds more easily, and its light weight and electric propulsion (which provide very high torques, especially at low speeds) would provide sporty acceleration. These attributes, plus nimble handling and short stopping ranges, should be welcome in the marketplace. Furthermore, ultralight body materials can typically provide superior acoustics, stiffness (hence comfortable ride and refined handling), fit and finish, and resistance to corrosion and fatigue.
In summary, fuel efficiency is only one feature of the Hypercar concept—equivalent or superior performance is also integral. Some styling changes will be necessary to improve the car's aerodynamics, but the Hypercar concept does not prescribe a single body design to enable it to work.
For more technical details, see the RMI publication "Ultralight Hybrid Vehicles: Principles and Design,".
Battery-electric vehicles (BEVs) suffer from limits of battery cost, life, and energy per kilogram that make them unsuitable as all-purpose cars for most people. Recently, their performance has significantly improved, opening certain niche markets, but they're still far from being widely attractive.
However, ultralight hybrid-electric cars can achieve the important advantages of electric propulsion—building on the same technological foundation—without the disadvantages of batteries. As explained in the previous answer, hybrids wouldn't need the massive storage batteries that are largely responsible for BEVs' short range, increased cost, and other limitations. Technical modeling by RMI suggests that hybrid-electric Hypercars could meet or even beat the cost and performance criteria of comparably sized conventional cars.
BEVs' big selling point is their low emissions, and it's with BEVs in mind that California regulators have mandated that 10 percent of cars sold in that state must be "zero-emission vehicles" by 2003. But of course the term "zero-emission vehicle" is a misnomer, since all cars produce emissions somewhere; battery-electric cars simply displace them from the tailpipe to the power plant. RMI calculates that a BEV adds about as much to Southern California's pollution, in the form of local power-plant emissions, as a modern car getting about 90 mpg would. Recognizing that cars capable of getting that mileage or better may be feasible, California is in the process of rewriting its regulations to allow any vehicle that runs as clean as a "zero-emission vehicle" (taking into account the energy-supply systems of both) to qualify as one.
Hypercars, then, can achieve comparably low emissions without BEVs' drawbacks. This should lead to a more positive overall environmental benefit, since the Hypercar's potential market is much larger than the BEV market.
For a more on this, see "Vehicle Design Strategies to Meet and Exceed PNGV Goals" or the shorter (but more recent) "Ultralight Hybrid Vehicles: Principles and Design,".
Hypercars could be designed to run on almost any type of fuel—liquid or gaseous, renewable or non-renewable. Although emissions depend on fuel choice, the Hypercar platform would be so efficient to begin with that it would be much less polluting than a conventional car even if it used standard gasoline or diesel. Hypercars' high fuel-to-traction efficiency would also make cleaner gaseous fuels (such as methane) more feasible, because smaller, lighter, and cheaper storage tanks could be used without compromising range. (The same reasons would make hydrogen an attractive Hypercar fuel, especially if converted to electricity via an onboard fuel cell—see the next answer.)
Many factors are likely to influence which fuels are used in Hypercars, including fuel price, market preference, fuel distribution and refueling infrastructure, and public policy. In Europe, for instance, early Hypercars might be powered by small diesel engines, since European automakers are very good at building relatively clean diesels. In the United States, compressed natural gas or unleaded gasoline engines might be preferred in the near term.
But in the medium to long term, hydrogen looks like the most promising fuel for Hypercars because it produces very low to no emissions and can be made using renewable energy. More on this in the next answer.
Yes, vigorously, by both RMI and automakers. Fuel cells are an exciting APU (auxiliary power unit—i.e., engine) option because they're very efficient, produce zero or near-zero emissions (depending on the type and origin of the fuel used), could be extremely reliable and durable (since they have almost no moving parts), and could offer a high degree of packaging flexibility. Currently, however, they're very expensive because they're not produced in volume, and a widespread refueling infrastructure doesn't yet exist for some of the fuels considered for their use.
Fuel cells generate electricity directly by chemically combining stored hydrogen with oxygen from the air to produce electricity and water. The hydrogen can be either stored onboard or derived by "reforming" gasoline, methanol, or natural gas (methane). Reforming carbon-containing fuels generates more emissions than using hydrogen created directly with renewable energy, but these fuels are much more readily available and may be used as a transitional step until a hydrogen infrastructure develops.
Fuel-cell technology has advanced significantly in the past few years, and a handful of automakers have shown prototype fuel-cell-powered vehicles. However, these prototypes have been quite heavy, requiring large (and therefore expensive) fuel-cell powerplants, which has led some observers to predict that it may take 15 to 20 years for fuel cells to become economical. Yet Hypercars could accelerate the adoption of fuel cells, because the Hypercar's much lower power requirements would require far less fuel-cell capacity than a heavy, high-drag conventional car. This could make fuel cells affordable much earlier in Hypercars than in conventional vehicles.
Polymeric composites combine superior strength and stiffness with light weight by embedding very strong reinforcing fibers in a supporting "matrix" of plastic. The fibers can be chosen and oriented to match the mechanical properties required, improving performance still further. Hypercars' bodies would probably use mainly "advanced" composites, which contain carbon, aramid (Kevlar), or similar fibers, making them stiffer and stronger per kilogram than glass-fiber-reinforced composites. The composites would probably be molded into a "monocoque"—a shell that is itself the structure and requires no separate frame or chassis. Advanced composites are already widely used in aerospace and in high-performance boats and sporting goods.
Advanced composites have many benefits, both technical and strategic:
Advanced composites' main disadvantages are their high material cost, steel-based automakers' unfamiliarity with them, and the fact that high-volume manufacturing processes haven't yet been demonstrated for similar applications.
Safety is critical, and it is part of RMI's ongoing Hypercar research. We believe that any new vehicle concept should not just equal but exceed the safety of today's vehicles, and that Hypercars can do so.
Ultralightweight vehicle design, while presenting new challenges, does not preclude crashworthiness. Using proven technologies for energy absorption, force-limiting occupant restraints, and rigid passenger-compartment design, light vehicles could surpass the safety of today's cars in many types of collisions.
In a head-on collision with a vehicle much heavier than itself, a Hypercar would have to absorb proportionally more energy to protect its occupants. Although this puts the Hypercar at an initial disadvantage, other features can more than compensate. For example, since the hybrid drivesystem can be small and modular, a larger portion of the space under the hood can be used to absorb energy and slow down the vehicle—instead of being filled with a large, uncrushable engine. Composites can make the most of this extra space because they can absorb many times more energy per pound as steel, and can do so more smoothly, thus using the crush space more efficiently. These two features, along with other benefits of composites, could make it possible for a Hypercar to protect its occupants adequately in a head-on collision with a car roughly twice its mass. (Other kinds of collisions require additional engineered safety features that are already available.) We are currently investigating what the practical lower limit to a Hypercar's mass would be for safety reasons, given the current mix of vehicles on the road, but believe better design and materials will prove an adequate substitute for the "juggernaut strategy."
Over the long term, replacing conventional cars with lightweight Hypercars would markedly improve safety for all road users. Heavy cars protect their occupants at the expense of the occupants of other cars with which they might collide, but lighter Hypercars would pose less threat to the safety of others (including pedestrians and cyclists). Lightweight, but very strong and protective, Hypercars would thus be a win-win situation for both parties in a collision.
Whether a Hypercar—or any car—is recyclable depends on many factors. Three of the most crucial ones are briefly discussed below. For more detail, see the RMI publication "Ultralight-Hybrid Vehicle Design: Implications for the Recycling Industry,".
Design and Constituent Materials
Since they'll be starting from a clean slate, Hypercar designers will have the opportunity to incorporate recyclability into the entire car. For example, they could make the Hypercar from materials that can be recycled together or that are easily separable. (The more dismantling effort required, the harder it is to recycle a car economically.) The advanced composite materials RMI proposes to use in Hypercars are very different from those currently used, and thus will require a new recycling infrastructure, so attention to recycling is of even greater importance.
Recycling Technologies Available
The perception that composite materials are unrecyclable is due in part to the problems of recycling plastic packaging and containers. But while the issues may be similar, the economics are very different. Junked cars, regardless of what they're made of, have considerable salvage value. Roughly 90 percent of vehicles retired each year in the United States end up at a dismantler's yard, where their salvageable parts are removed for remanufacture or reuse—unlike plastic packaging, which typically isn't worth the cost of collecting it. Since the advanced composites proposed for use in the Hypercar are expensive, there would be an even stronger incentive to find an economical means of recycling them.
At least two such technologies exist—low-temperature catalytic pyrolysis and solvolysis—and both appear to provide the required attributes.
Standard pyrolysis breaks down polymers at very high temperatures in the absence of oxygen. The result is low-value "pyro-oil" (a mix of petrochemicals whose exact composition depends on the feedstocks), ash, and heat. While technically feasible, standard pyrolysis would not be desirable for recycling scrapped advanced-composite autobodies because the fibers could not be recovered. However, a handful of innovative processes based on pyrolysis have shown great promise by reducing the operating temperatures so that the fibers are not destroyed.
Solvolysis is used to break down a variety of polymers at high temperature and pressure and with an appropriate solvent. Solvolysis has proved successful on a small scale for recycling pure, unmixed manufacturing scrap and some post-consumer plastics. Research is being done to adapt the process to handle certain mixed-plastic streams and to be more tolerant of contaminants. Despite some success with unmixed plastics, solvolysis has never been used to recycle advanced composites. More research on this application is needed.
Markets for Recycled Materials
Processes such as low-temperature pyrolysis demonstrate the technical feasibility of advanced composite recycling, but markets for the recycled material are essential in order to justify implementing the technologies. While predicting the future of such markets is difficult, current trends suggest the economics will be favorable.
For resins, some recycling processes already in existence could return recycled material to the polymer fabricator at a cost competitive with virgin feedstocks—encouraging evidence that the polymers in a Hypercar could be economically recycled. For fibers, the markets for chopped and milled versions are strong. Fibers recycled through the low-temperature pyrolysis process could potentially be sufficient for this market and others, but at a fraction of the current price. Preliminary cost estimates indicate that chopped recycled carbon fiber could be profitably supplied at less than a fifth of the current virgin price.
Of course, a few factors could devalue the materials recycled from Hypercars. First, Hypercars wouldn't be retired in large numbers for 20 years or more, by which time the price of virgin materials is likely to be much lower than it is today. It's impossible to predict whether the price of recycled materials will keep pace. Second, products not designed with recyclability in mind, such as composite autobodies with combinations of fibers that aren't easily separable, could make materials recovery very difficult, thus less economic. Third, the profitability of dismantling could be affected by rapid technological progress, causing demand for components from older cars to plummet. It's worth noting, however, that these forces could affect the viability of any automobile recycling system, not just one based on Hypercars. Moreover, although Hypercars would not be technically suited to the current car-recycling infrastructure, there would be plenty of time to adapt existing methods and equipment.
In any case, Hypercars may prove to be so durable and so readily upgradable in both hardware and software that they could undergo many "reincarnations" before requiring remanufacturing or recycling. And even if none of this were true, and if Hypercars, after removal of valuable components, were simply chopped up whole and landfilled at the end of the same lifespan as steel cars, our modeling suggests they would still generate roughly the same amount of shredder "fluff" (unsalvageable and unrecyclable material) as today's cars.