If we didn't know otherwise, the burning of the complex substance gasoline, in internal-combustion engines would appear to be a bad propulsion method for automobiles. About 20 percent of the thermodynamic energy arrives at the tire road interface. The atmosphere polluting effects of the toxic exhaust products would be unthinkable were it not already an everyday fact of life. You cannot too quickly fault those who contend it was a mistake to abandon the horse as the prime mover of people and goods!
The dilemma of the gasoline-dependent auto is easily explained, however. For notwithstanding all of its shortcomings, it has so far exhibited the overall transportation characteristics of any fuel-engine format. Various environmental, political, and economic pressures might alter this situation. On the horizon, we see alcohol and methane-fueled cars. These provide partial remedies to some of the negative features of conventional automobiles. The use of hydrogen to fuel an internal-combustion engine looks good from the standpoint that the main exhaust constituent would be water vapor. However, storing and transferring hydrogen might impose some nasty problems. Also, hydrogen enthusiasts tend to overlook the cost and side effects of producing the hydrogen in the first place.
For many decades, electric vehicles have not lacked their share of eager proponents. These proponents rightfully call attention to the quiet and smooth operation of such cars. And, it is easy to support their contention that electric vehicles are simple and reliable, being devoid of the hundreds of moving parts (many of them reciprocating) in gasoline-motored autos. They also emphasize the lower order of maintenance probably needed.
However, these proponents tend to overlook some disturbing aspects of their euphoria. For example, it is true that the electric vehicle need not pollute the air from its own operation. But, the electric generating utility will be obliged to eject more pollutants into the atmosphere. Probably, in balance, fewer toxins will hover over cities, however. Also, a beneficial trade off could result considering the nature of the polluting substances on a global scale.
It is sometimes also overlooked that, thus far, electric vehicles don't appear likely to rival gasoline cars in performance. Any increase in power or acceleration is at the expense of range, which remains at short supply at best. Then too, the owner of the electric vehicle will probably have to allow for overnight charging from his residence. Special stations would be available for faster charging, but nothing approaching the two or three minutes it takes to refill a gasoline tank. Finally, this owner will probably have to cough up a sum for battery replacement at two to several-year intervals—all practical batteries deteriorate from repeated charge-discharge cycles.
Although dramatic breakthrough has not been made, the electric vehicle is steadily gaining a respectable measure of public acceptance, and is finding its own special niches. The laws of physics and the constraints of practical engineering do not stand in the way of continuing progress in batteries, motors, and control techniques. At some point, the more general market will decree overall performance to be worthy of investment. That time might be close at hand, especially if the cost factor can be relaxed via mass production—admittedly easier said than done.
The lead-acid battery: survivalist-hardened energy source
The Achilles heel of the electric vehicle in 1913 was the battery. Even then, it was all too evident that the energy stored in a gallon of gasoline greatly exceeded the energy stored in either the same weight or volume of an electrochemical storage device. The practical manifestation of this was that automobiles with internal-combustion engines and fueled by gasoline could easily outperform electric vehicles despite the much lower overall efficiency of gasoline cars. Particularly distressing has been the limited range between charges in electric vehicles. The lead-acid storage battery was used in 1913 electric autos, and it is amazing that this type of battery remains a viable energy source for electric vehicles.
Battery technology is a voluminous subject. However, it is not necessary to cover the subject in great detail. Despite the investigation of almost countless battery types (many using exotic materials and sophisticated operational techniques), most prove deficient in some performance characteristic. The frustrating aspect is that there invariably appears to be unacceptable trade offs between important parameters. For example, the highly touted sodium-sulfur battery must operate at an elevated temperature (about 570° F) to keep both, the sodium and the sulfur, in a molten state. The container for such a battery is like a thermos bottle in order to pre vent appreciable heat leakage. Although such a battery outperforms the simpler lead-acid type, the public is not enthused by the prospect of being doused with either highly reactive molten sodium, or by hot liquid sulfur in an accident. Incidentally, advanced lead-acid batteries are of the gel type, in which relatively little sulfuric acid electrolyte is retained in sponge-like material.
A unique attribute of the venerable lead-acid battery is its ability to provide high levels of power for short durations. Indeed, that is a major reason it has been so useful in conventional automobiles where tremendous starting current might be demanded by a large engine on a cold morning. For the electric car, such capability is needed for passing, acceleration, and hill climbing. Interestingly, one overseas electric-vehicle uses exotic batteries to gain range from superior energy storage, but also carries enough lead-acid batteries to supply short-time demands of high power.
Many exotic batteries have aroused premature enthusiasm with high specific energy, acceptable specific power, manageable cost, and tolerance of wide ambient- temperature swings, only to fail miserably because of limited life span. All practical batteries deteriorate with charge-discharge cycles. Again, the lead-acid battery is found to provide a compelling balance among all performance parameters, including initial cost. Until exotic batteries can prove as impressive on the road as in the benign environment of the laboratory, the time-proven lead-acid type is not destined to be quickly obsolete.
The chemical action in the lead-acid cell
The lead-acid battery has always been recognized as possessing a very desirable feature—it could be restored to use after being discharged by reversing the direction of current flow. In other words, such a battery could be recharged by receiving energy from an external current source. Such behavior stands in contrast to a large class of batteries in which discharge is a unilateral process; either one electrode is consumed, or non-reversible chemical changes render such batteries permanently un suitable for further use. Thus, we have the two major types of cells or batteries—the primary batteries that are good for a single discharge action, and the secondary or storage batteries that can be restored to active performance by recharging from an external current source.
The chemical action within the lead-acid cell is depicted in FIG. 1. Initially, one electrode consists of lead dioxide, PbO The other electrode is lead, Pb. These are immersed in a sulfuric acid electrolyte, H. The electrolyte provides dissociated positive hydrogen ions, H and negative sulfate ions, SO as current carriers within the cell. These ions charge the electrode plates, which promote electron flow in the external circuit. Ultimately both electrodes become coated with lead sulfate, PbSO and we no longer have an active electromotive cell. In the process of discharge, water is formed that dilutes the electrolyte. That is why a hydrometer can be used to sample the density of the electrolyte, and to infer from it the state of charge of the cell. The nice thing about the chemical reactions is that they can be reversed by reversing the current flow for an appropriate period of time.
FIG. 1 Chemistry of the lead-acid cell. As discharge commences, both plates become converted to lead sulfate, PbSO At the same time, part of the electrolyte becomes converted into water, H The reverse reactions occur when the cell is charged from an external source of dc.
Even the relatively dilute sulfuric acid is a much less harmful agent than the chemical substances used in some of the more exotic battery types. Replenishment of the acid is not necessary; only distilled water need be added to compensate losses from evaporation and electrolysis. Even this is not necessary in advanced designs. A further improvement is the use of a gel instead of liquid electrolyte. And finally, lead is an inexpensive and benign material. It is easy to see why research programs not only seek out new exotic-battery formats, but focus considerable effort in further improvements of the venerable lead-acid battery. Its specific energy of about 40 or possibly 50-Whlkg is not impressive, but its overall features adapt it well to electric-vehicle service.
The nickel-iron battery: another enduring tough one
The lead-acid battery has a companion type that was also in use during the turn of the nineteenth century. It was the nickel-iron battery with potassium hydroxide electrolyte as devised by Thomas Edison. It, too, possesses some notable qualities and has undergone some significant improvements over the course of the years. It has both superior and inferior features compared to the lead-acid battery. It is lighter, but has less specific power than lead-acid types. The nickel makes its initial cost higher, but it can endure more charge-discharge cycles. Environmentalists tend to frown on nickel as a toxic metal. All things considered, the nickel-iron battery, like the lead-acid battery, exhibits a good balance of important characteristics. Significantly, it was the battery of choice for the Impact electric-automobile developed by General Motors. Nickel-iron batteries undergo little damage from idleness, whereas the lead-acid battery can be permanently damaged by long periods of nonuse (plates become sulfated).
Discharging Pb + PbO2 + 2H2SO4 <-- > 2PbSO4 + 2H2O Charging
The nickel-iron battery enjoys another advantage along with the lead-acid storage battery. Both of these batteries have profited from a century of manufacturing experience. This is very important and is a major explanation why many apparently superior batteries do not yet qualify for consideration for use in electric vehicles. From a purely textbook approach, it is easy for the electrochemist to select battery materials to maximize cell voltage, minimize weight, and optimize other parameters of battery characteristics. For use in the practical world, however, other things enter the scenario. Highly reactive electrodes and/or electrolyte pose safety questions. The charging characteristics are not readily calculable, and many otherwise satisfactory battery formats could not endure a reasonable manner of charge/discharge cycles. Some battery types have required auxiliary equipment, such as electrolyte pumps or cooling provisions. Some batteries lose charge rapidly when not in use. Some battery systems are vulnerable to mechanical shock and vibration. Many are too costly, or don't lend themselves to easy mass production. And, not infrequently, unpredictable “bugs” turn up. A case in point was the “memory” behavior that long plagued the operation of nickel-cadmium batteries.
Summarizing, the lead-acid battery and the nickel-iron battery remain viable energy sources for electric vehicles, and will remain so until displaced by higher performance types that can also comply with the many practical demands of the road.
Basic chemistry of the nickel-iron cell
Although different materials are used in the Edison, or nickel-iron battery, it shares important features with the lead-acid battery. Most important, both formats qualify as secondary batteries because they permit replenishment of stored electrochemical energy by the simple technique of recharging. Instead of an acid electrolyte, the nickel-iron cell makes use of potassium hydroxide; for this reason, it is sometimes referred to as an alkaline cell. Interestingly, the density and composition of the electrolyte remains fairly constant regardless of the state of charge. Thus, the use of hydrometer is not indicated for ascertaining the charge condition.
Some unique features of this battery include: it is not very susceptible to damage from overcharging, it remains functional in colder climates than does the lead acid battery, it can be stored in inactive condition for many years with negligible chemical deterioration, and it is a lighter battery than the lead-acid type. Obviously, if the vehicle can haul less dead weight, its range can be extended. A shortcoming is that the nickel-iron cell develops about 1.4 volts compared to the approximately 2.15 volts of the lead-acid cell. Thus, a designer must incorporate more cells in order to attain a desired operating voltage in the vehicle.
When a nickel-iron cell is charged, its positive electrode is a higher oxide of nickel and its negative electrode is iron. During discharge, the positive electrode is converted to a lower oxide of nickel, and the negative electrode becomes iron-oxide. Recharging from an external source of current reverses this change in electrode composition. In essence, you have the transit of oxygen ions in one direction or the other depending on whether the bell is being discharged or charged. A chemist would say that the iron electrode (negative terminal) undergoes oxidation during discharge, and that the nickel-oxide electrode undergoes reduction during discharge. Oxidation and reduction then take place at opposite electrodes when the cell is charged. The nickel-oxide electrode alternates between the higher oxide of nickel, Ni0 and its lower oxide, NiO.
An unusual constructional feature of the iron-nickel cell is that its container and its various mechanical support elements are largely made of steel. No corrosion, undesired chemical reactions, or interferences with the cell operation are experienced from this fabrication technique, which actually contributes to the long life and stability of this cell format. Where necessary, hard rubber, or more advanced insulating materials are used for separators between plates, and where conductive supports are ruled out.
Batteries—Plain and fancy
It is not easy to define a battery format that is “exotic”. In this book, the general idea will be that batteries other than lead-acid or nickel-iron types qualify as exotics, at least from the standpoint of applicability to electric vehicles. Admittedly, some battery types will occupy nebulous positions in which a valid argument can be presented regarding their exotic status. For example, it is easy enough to question the “exoticness” of nickel-cadmium batteries, which have had many years of experience in all manners of practical power applications. However, the very fact that this battery for mat has, and continues to evoke, strong objections for vehicular use because of environmental, cost, marginal performance, safety (real or perceived), or other reasons inhibits wide acceptance for powering electric vehicles. Because a battery format is labeled exotic doesn't mean that it has no potential for consideration. Indeed, the very opposite tends to be true; they generally possess a cluster of very compelling at tributes in conjunction with one or a few shortcomings. Exotic batteries are worthy of mention for the simple reason that much time, money, and effort is invested in endeavoring to overcome the shortcomings. Most certainly, some of these efforts will meet with enough success to merit consideration.
Keep in mind that the near-term objective of improved battery performance is not to necessarily match or exceed the performance of conventional automobiles. However, there is general consensus that the range between recharging should be on the order of at least two-hundred miles of “average” driving conditions. The cost should not be exotic—this takes into account the number of replacements needed over, say a five- or six-year term of ownership. Although “quick charging” cannot be done from the residence wall outlet, the battery should be amenable to shorter than the generally prescribed eight-hour period. Although not an impenetrable barrier, the need for elevated temperatures and the reliance on highly reactive agents are negative factors. Very superior performance would be necessary to overcome these negative factors. (That is why the public accepted the conventional automobile even though it uses the highly volatile, flammable, and potentially dangerous fuel, gasoline). Some of the exotic electrochemical systems that have at one time or another been touted as the “breakthrough” for the electric vehicle, or that could conceivably show favorable prospects in the future are listed in Table 1.
Table 1. Some exotic battery systems with possible application to electric vehicles. Watch for careless comparisons between kilowatt-hours per kilogram and kilowatt-hours per pound in the technical literature. One-kilogram = 2.205-pounds and one-pound = 0.4536-kilogram.
(match numbers in each column for correlation)
“Fill it up” . . . but, how quickly?
When evaluating the characteristics of a battery system for an electric vehicle, it is almost instinctive to hope for the ability to recharge quickly. In such a quest, how ever, it is all too easy to overlook a practical barrier to rapid charging, other than the battery itself. Consider, for example that a vehicle has a battery supply rated at 60-kilowatt hours. Suppose that half of this energy has been used up and it is de sired to replenish the fully charged condition from the 120-volt wall outlet of a typical residence. To accomplish this in ten hours, the required current drain from the household would be:
30 kw-hrs / 120V x 10hrs
1/40 kilo-ampere, or 25 amperes. So far, so good. Certain electrical appliances do successfully run on 25 amperes in the home. For simplicity, the less than 100 percent efficiencies of the rectifier and the electrochemical process within the battery are ignored in this example. The gist of the idea being developed will not be materially affected, however.
In the example, as so far presented, the charging technique is practical, even if it be argued that it is only marginally so. But now, suppose that you are somewhat less patient and demand replenishment of your “fuel” in one hour. The wall outlet would then be called upon to supply 250 amperes under the postulated conditions. This would be clearly unacceptable and in a practical sense would constitute a short circuit.
What might help? Many homes have 240-V optional outlets. The use of this option might reduce the required charging time to five, or possible four hours. For quicker charging than this, it would be necessary to go to a special “fifing station” where the time could be further reduced, say to an hour or less. It is not too easy to visualize much faster service, although it is not clear exactly where to establish a limit to such rapid charging. Such a limit might exist because the battery itself might have its life threatened or shortened by an excessive charging rate. The mindset of the owner of an electric vehicle will have to change to comply with the new circumstances—no longer is he likely to enjoy the luxury of refilling the “tank” in a couple of minutes or so.
This problem might bring into being battery or fuel-cell systems in which spent electrodes and/or electrolytes are physically replaced by new materials. This might conceivably be done in some minutes, but one would hope there would be no detrimental trade off in other performance features. Then, there is the possibility of temporarily trading one's discharged battery for a quickly replaceable fully charged one. The economic and mechanical practicability of this strategy is open to question, however.
No rest for the virtuous
There is another aspect of the recharging scenario that tends to hold back the popularization of electric vehicles. The matter of charge rate has already been alluded to and it will be assumed that the public is willing to live with appreciably slower energy replenishment than prevails for conventional automobiles in which a quick visit to the gas station suffices. This has to do with the handled by the motorist to recharge his vehicle battery; it merits special attention be cause it involves safety. It looms up as a particularly nasty obstacle, but you might be heartened by the fact that the public routinely handles the gasoline pump—a potentially dangerous operation that we just take for granted because it has been in place for so many years. We have learned refrain from smoking while refueling, but otherwise we don't give much thought to the flammability of the volatile liquid we are dispensing.
In the case of the electric vehicle, there is the matter of electric shock from the 120-V ac line, or worse, from 240-V lines that will be used to gain shorter recharges. Recessed connectors and other hardware innovations can be used, but with millions of electric vehicles (eventually) being recharged around the clock, the probability for injurious or lethal electric shock is not negligible. The danger would be enhanced in wet weather, and would increase with extended use of the cables, plugs, and receptacles. The problem is also related to the controversial issue as to whether the charging equipment and/or cables should be carried on board the vehicle, or should they be incorporated in a stationary location. The vehicle manufacturer is reluctant to carry the charger in the vehicle because it counters the objective of transporting as little weight as possible. A compromise might readily be made, however, if the charger is not too massive; this implies that the charging rate cannot be too high.
Another approach—one likely to receive serious consideration—uses inductive coupling to transfer energy from the ac utility line to the on-board battery charger. The owner would merely have to position his or her vehicle over an induction loop on the floor. Because of limited ferromagnetic material, the efficiency of this technique would best be served via frequencies in the supersonic, or low RF region.
As with many of the exotic batteries, here is a disparity between what the technologist knows is feasible, and the mundane requirements imposed by practical ownership of electric vehicles. Commendable performance and affordability are not enough if the public suspects problems of safety, reliability, or undue convenience. A little contemplation shows that these matters are closely interlinked.
Can the utilities handle the load imposed by electric vehicles?
The arrival of popularity of electric vehicles will not be an isolated phenomenon. A supporting infrastructure will be necessary. Some of the elements are already in place, such as roads, traffic signals, and utility power. However, the latter element requires some scrutiny, because it is the most important—it is the utility that really provides the energy for the electric vehicle, even though storage batteries are used as intermediary agents. The all-important question is whether electric vehicles will adversely impact the electrical generating station. This will decide whether electric vehicles are destined to fill a meaningful transportation niche, or whether they will continue as interesting toys of technically inclined hobbyists.
We might conceivably be pessimistic regarding this matter, for it is common knowledge that utilities have been complaining about overloads. In the summer, air conditioners sap a great deal of energy. In the winter, electric heaters tend to be the culprit. It might seem that the additional load imposed by battery chargers replenishing energy-hungry batteries could be the straw that breaks the camel's back. Massive upsizing of generating capacity would surely run into economic roadblocks; also, delays would likely be brought about by environmentalists. Thinking in these terms, it appears that our discussions of batteries, motors, and control techniques is an interesting academic exercise, but devoid of practical relevance.
Fortunately, it turns out that advocates of electric vehicles have both brains and luck. The utility companies would actually welcome such additional loading, al though under certain easily complied with conditions. The size of a generating station is determined by the peak load it expects to handle. But, during off-peak hours (during night time) the larger than necessary facilities are expensive to run-efficiency is low and there is not much revenue. For this reason, some means would be imposed to induce electric vehicle owners to do their charging at night, a not necessarily inconvenient activity. Calculations reveal that it will be many years before most utilities will need to increase their energy capacity. It will be important in many cases, however, to discourage too much daytime recharging.
It has already been pointed out that although large-scale use of electric vehicles would shift the pollution source from city streets to the remotely located utility station, a worthwhile reduction in net pollution would nevertheless result. Not only would there be less overall pollution, but the solution products indirectly attributed to the energy demand of electric vehicles would be relatively benign compared to the exhaust gasses from the internal-combustion engines of conventional automobiles.
DC or AC motors?
For many decades, the dc series motor had been the basic workhorse of various types of electric vehicles. Sometimes, an extra shunt field was incorporated and the compound motor thereby created enabled better optimization of the speed-torque relationship, as well as refinement of control. Later, when high-flux permanent-magnet motors became practical, these motors were also found to be satisfactory. And when solid-state power devices began to be used as choppers or duty-cycle modulated control elements, it was felt that the drive/control functions had at last attained mature technological status in the electric vehicle.
However, these same solid-state devices also enable design and construction of very efficient inverters, and it wasn't long before serious consideration was given to the use of ac motors. This was largely inspired by the desire to eliminate the commutator and brushes inherent in conventional dc motors. The attainment of this objective would dispense with a major maintenance item. Enthusiasm was enhanced by the fact that these solid-state inverters could be implemented in two-phase and three-phase formats, and the frequency could be readily controlled. Successful drive power was achieved with induction motors, and also with synchronous motors. Additionally, so-called brushless dc motors were demonstrated as successors to the venerable dc series motor. Giant stepping motors offered yet another way to circumvent the need for brush and commutator motors.
Actually, an ongoing controversy developed between the proponents of the time-proven dc series motor, and those who see ac motors as harbingers of advanced technology. Both design philosophies are imbued with much merit. Despite the mechanical motion and sliding contact of brush and commutator motors, an electric vehicle appears able to accumulate about 80,000 miles before brush and commutator “tune ups” are needed. And compared to various repairs required in an internal-combustion engine, such maintenance is not major surgery. Also, it must be conceded that when such a motor is duty-cycle controlled, the overall performance is very satisfactory.
On the other hand, even better efficiency can be realized with ac motors. They tend to be smaller and lighter. Another advantage is that they lend them selves better to total enclosure, thereby keeping out dirt and grit. Polyphase induction motors and synchronous motors are less costly to manufacture. But it is difficult to find overwhelming evidence in favor of either type of motor. In the near term, we might expect to see both types used in electric vehicles. This is especially true because electronic control enables desirable performance characteristics to be tailored into a variety of motors no matter what the natural behavior of the motor might be.
Reducing losses with germanium power transistor choppers
An electric golf cart is a relatively primitive electric vehicle, somewhat reminiscent of “horseless carriage” automobiles marketed during the early years of this century. In particular, the use of the dc series motor and lead-acid storage batteries can cause you to ponder the progress of technological development made three-quarters of a century or so ago. There are, of course, more sophisticated golf cart designs, some with 10-horsepower ac motors, but the described format still yields satisfactory performance.
The dc motor is usually the series type, often with a dual series winding arranged to allow convenient reversal of motor rotation. Some designs have used permanent-magnet motors and compound motors. In any event, dc motors of about two-horsepower capacity seem to provide optimum compromise among performance and cost factors. The storage batteries are similar to those used in automobiles, except that they are designed for long survival in the face of many deep discharge/charge cycles.
The control of speed by variable resistance, although workable, would be undesirable because of the waste of energy and the shortening of serviceable time between battery charging. A dc chopping technique is much better. Indeed, the ability to implement such control is one of the greatest advantages over the early electric automobiles. A simple and effective chopping format can be provided by the PWM control-ICs commonly used for switching-type power supplies. The modulation can be either constant frequency, variable pulse width, or constant pulse width, variable frequency. In either case, the average voltage applied to the motor is varied by a means that. would be 100 percent efficient in ideal form.
For golf carts, at least, germanium transistors merit consideration as the power switches to supply the chopped dc to the motor. Germanium power transistors are inexpensive and exhibit very low collector saturation voltages, making dissipation from conductive losses low. However, successful use of those devices often requires ways to deal with their switching losses and their tendency towards high leakage current. The partial circuit of an electric golf cart shown in FIG. 2 illustrates practical methods of circumventing much of these losses, while still benefiting from the desirable features of germanium power transistors. Notice the two departures from conventional circuits of this variety: All germanium transistors have turn-off biases applied to their bases and there is an SCR connected across the paralleled bank of germanium switching transistors (Q3 through Q8).
The consequence of this arrangement is that the part of the switching loss inherent in the slow turn on of the germanium transistors is overcome; the SCR turns on much more quickly. Moreover, the motor current is carried by the transistors for most of the conduction time. This comes about because of the lower voltage drop in these transistors. Thus, each device is allowed to be active where it is advantageous. SCRs alone would cause higher conductive losses; germanium transistors alone would cause higher switching losses. The nice thing about this hybrid scheme is that the de sired transitions from one type of switching device to the other occur automatically.
It is natural enough to ponder the relevance of discussing a golf cart when our investigation of electric vehicles purports to deal with a possible substitute for the gasoline-powered automobile. Many electric car enthusiasts have often used scaling- up techniques on golf cart designs to produce an electric automobile. Also, to satisfy the needs of the golf cart, battery manufacturers have developed lead-acid batteries that feature good longevity in the face of many repeated deep-cycle discharges. Thus, these batteries proved tailor made for many experimental electric autos. The inordinately high electrical ruggedness of these golf cart batteries also enable faster charging rates. This sets well with electric car owners, whose patience for this interlude is notoriously in short supply.
Germanium power transistors are now made by Germanium Power Devices Corporation of Andover, Massachusetts. This firm has taken over the device lines of Motorola, RCA, G.E., and others, and has developed its own family of improved devices. Readily available are 25, 50, and 100 ampere power transistors. When experimenting with germanium transistors, keep in mind their polarity requirements inasmuch as they are PNP devices. Fortunately, in vehicle applications, massive heat sinking is usually not objectionable and it is not difficult to operate germanium transistors at moderate temperature rises. This alone circumvents one of their common short comings in non-vehicular uses.
Experimenters with electric vehicles should also be aware that this company has developed germanium Schottky diodes with several hundred ampere capability. These drop less voltage and waste less power than either silicon junction diodes or silicon Schottky rectifiers. A possible use might be in battery systems combining two different types of batteries, usually one for high specific energy to give the car a long range, the other for high specific power to enable sudden acceleration, and to aid iii hill climbing. Electrical isolation of the two battery types is achieved by connecting them in parallel through a diode. Each battery is then free to undergo its own independent charging rate.
Conversions: A practical path to electric propulsion
It is somewhat of a paradox that the “most bang for the buck” electric cars have been designed, produced, and marketed by small-scale entrepreneurs. For a much higher initial cost, the large corporations have developed electrics with exotic batteries, elegant motor-drive systems, and sophisticated electronic controls. But, thus far, they have not impressed the public with their claims of performance, reliability, convenience, and overall ownership expenses. The situation is not unlike the auto market during the great depression when many different makes of cars competed for the consumer's interest by offering a myriad of then state-of-the-art innovations. It turned out that the best-seller was the economy-priced, no-nonsense Model A Ford.
With electric cars, too, the public has been best served with straightforward, time-proven systems involving low-cash outlays and capable of readily acquired maintenance. This generally translates into the conversion of light four-cylinder automobiles to electric propulsion. Most often, a dc series motor fed from heavy-duty lead-acid batteries via a variable duty-cycle electronic chopper comprises the “guts” of the installation. Cleverly designed kits are offered that enable the purchaser to easily replace the gasoline engine with the dc motor. Often, no welding, machining, or special mechanical procedures are involved in the conversion. Typical performance ratings are top speeds of 65 mph and ranges of 60 to 80 miles. Advertising emphasizes practicability within the limited performance capability—the public is not deceived to expect comparable performance to gasoline cars.
An example of such electric cars is shown in the photograph of FIG. 3. From the exterior, you see what appears to be a “normal” VW Rabbit four-passenger sedan. However, as shown in FIG. 4 the transverses internal-combustion engine and its peripherals have been removed. In its place, are the lead-acid storage batteries, but the dc motor is beneath them, not visible (the cylindrical object is the vacuum tank for the brakes). Figure 8-5 shows an installation. The eight-inch diameter dc motor is shown mounted to the car's transmission in FIG. 6.
The conversion kit was [ca. 1993] marketed by Electro-Automotive, P.O. Box 1113, Felton, California, 95018. All hardware, cabling, adaptors, controls, as well as special tools and heavy-duty springs and shocks are included. User-friendly instruction are also provided—the author interviewed a young lady who made the conversion with minimal outside assistance and was very pleased with the smooth, noise-free operation of the car. The overall cost of the kit was about $7,000 in 1992. A nice feature of this electric-car conversion is that the charger is carried aboard, enabling the driver to place the batteries on charge anywhere a 60-Hz, 120-V outlet is available.
From the user's vantage point, an electric car of this type has some compelling advantages when compared with more exotic designs. To begin with, the initial cost tends to be half or less of ordinarily encountered outlays. Note that the original transmission is retained. This confers the psychological benefit that it is “natural” to drive such an electric car (it has been determined that the loss of efficiency from retention of the gear box is not significant). The transmission also allows reverse, with out reversing the motor's rotation.
Lights and other electric peripherals that operate from a single 12-V battery in conventional automobiles also are supplied from their individual battery in the electric conversion. This battery is separate from the bank of 8 batteries that power the dc series motor. Instead of an alternator, a dc-dc converter samples the nominal 96-V “line” and delivers approximately 13.5 V to this additional battery in order to maintain its charge. The purpose of this technique is to provide equal drain to all eight of the “main” batteries.
Although, the performance parameters admittedly fall short of those attainable from internal-combustion engine automobiles, the practical fact of auto transportation is that about 60 percent of motorists probably demand less than a daily 45-mile excursion to get to and from their jobs, and for shopping and miscellaneous purposes. It appears that an electric car of this type can fill such a niche and be found rewarding because of its reliability, relatively low maintenance, smooth operation, and its environmental cleanliness.
The smoothest path to an electric car via conversion is to first find out what con version kits are available and then see about the availability of the appropriate vehicle. The Ford Escort happens to be a relatively easy car to deal with. In any event, what is needed is a light automobile with stick shift. The more mechanically adventurous often forego the kit and do the job from scratch. Popular motor experimenters have had success with the dc generators from large military aircraft. These have been available at government auctions and are often advertised by surplus out lets in hobbyist magazines.
The fuel cell
Most workers in the electric field agree that electric motors and motor-control techniques have forged ahead of the quest for a suitable source of on-board energy. As pointed out, the fancy numbers defining the performance of many touted battery formats simply do not translate readily into practical implementations. Exotic batteries look good in the laboratory, but exhibit serious shortcomings for actual use. There is one electrochemical cell, however, that deserves special mention, if for no other reason that it appears to offer the greatest promise together with tantalizing disappointments.
I am speaking of the fuel cell. To those familiar with the chemistry of primary and secondary voltaic cells, and with other electrochemical systems, such as electroplating, the fuel cell does not appear as a radical departure from its electrochemical cousins. It is, however, a unique device. Unlike primary cells, neither electrode is consumed. And unlike secondary cells, neither electrode undergoes chemical change; moreover, the fuel cell cannot be recharged, nor does it need such energy replenishment. Rather, as its name implies, it operates from a fuel, the simplest of which is hydrogen gas. It must also be provided with oxygen, but this need is satisfied by admitting air. A nice thing about a fuel cell, fed these ingredients is that the exhaust comprises hot water and the unused nitrogen of the air.
Hydrogen or hydrogen-rich gas
CO (Carbon dioxide if a hydrogen-rich gas is used; no emission if fuel is hydrogen.)
Hot water, also, unused nitrogen from the air.
Air for the purpose of using its oxygen content.
A basic fuel cell is shown in FIG. 7. The anode and cathode electrodes are porous carbon surfaced with a catalyst, such as platinum, which also is porous, or is applied so as not to clog the pores of the electrodes. These electrode assemblies are separated by an electrolyte to provide ion conduction. A commonly used electrolyte is phosphoric acid, which takes no part in any chemical reactions. Because both electrodes are of essentially similar materials, the device delivers no current as hitherto described.
If, however, hydrogen or a hydrogen-rich gas is introduced into the anode region and oxygen-bearing air is allowed to enter the cathode region, things begin to hap pen. Electricity is then supplied to an external load circuit. Let us see how this comes about.
Hydrogen molecules consist of pairs of positively charged hydrogen atoms, or ions. Ordinarily, there is a certain amount of separating and reuniting of hydrogen ions. In the presence of a catalyst, such as platinum, the separating of the ions from the molecule is greatly speeded up. As a result, many of these liberated ions migrate through the electrolyte and are attracted to the cathode, which bears a negative charge. But, when the catalytic action at the anode splits the hydrogen molecule into its constituent ions, it simultaneously liberates two electrons, which also reside in the hydrogen molecule.
It is these freed electrons that pass through the external load and back to the cathode, giving it its negative charge. The electron transit through the load constitutes the electric current in the load. An interesting thing then happens in the cathode region. Here, the atmospheric-borne oxygen is dissociated into negative oxygen ions, again by catalytic action. It so happens that if you have oxygen ions, hydrogen ions, and electrons in one region, the easiest recombination for these charged entities to enter into is the formation of H or water.
From the foregoing, a complete cycle of events has been traced—hydrogen molecules are dissociated into charged hydrogen atoms, that is positive ions, in the anode region. This ionization process also liberates free electrons that provide the electric current for the external load, and then return to the cathode. In the cathode region the cycle is completed when oxygen obtained from the air is catalytically ionized, and exhaust water is formed from hydrogen and oxygen ions and electrons.
The exhaust water carries away some of the heat from processes that are less than 100 percent efficient. Also, the atmospheric nitrogen, serving no chemical purpose, is ejected from the fuel cell. In the event a hydrogen-rich gas, such as methane, is used instead of pure hydrogen gas as fuel, carbon dioxide will also be exhausted from the fuel cell.
Practical fuel cells of this type provide about three-quarters of a volt per cell. Thus, such a dc power source must consist of many series-connected cells to develop suitable voltage levels for electric vehicles, generally in the 75- to 300-V region.
This energy technology compels consideration from the standpoint of allowing acceptable ranges for the electric vehicle; the fuel cell's specific energy can greatly exceed that attainable from electrically charged batteries. However, there are unsettled controversies regarding the nature and cost of the hydrogen-rich fuel. Also, our simplified discussion doesn't deal with various problems occurring with the catalysts and the electrolyte in actual applications. Much will be learned from the recent experimental installations of fuel cells in utility stations, where they will provide standby and peak-load power. Also, fuel cells have given good accounts of themselves in spacecraft. It is interesting to observe that some of the high-performance exotic batteries seem to use “semi” fuel cells inasmuch as they, too, consume oxygen from the air.
A common sense appraisal of electric autos
Caution is the name of the game in attempting to justify or condemn the electric automobile. Numbers can be cited to advance arguments, but the true meaning of numerical comparisons is often less than crystal clear. “X” battery might have three times the energy capacity of “Y” battery, but does such a statement take into account initial and maintenance cost, safety, reliability, environmental impact of its materials, mechanical ruggedness, charge retention, and recharge characteristics? Even more nebulous are the time-worn comparisons periodically made between gasoline-fueled cars and electric vehicles. It turns out that the energy problems faced by an industrial society are very complex; in the larger picture, the usual assertions about a preferred transportation mode often loses relevancy.
Consider oil in the ground of an overseas country. That oil must be extracted and transported at costs that are as likely to be influenced by politics, intrigue, and manipulation, as by economic forces alone. A barrel of oil represents a quantity of energy.
Energy is lost when the oil is refined to gasoline. Energy is lost when the oil is burned in a fossil-fuel utility station. Energy is lost when electricity is sent to the customer's wail outlet. Energy is lost when gasoline is converted to thermodynamic energy; thence to mechanical energy in the internal-combustion engine and transmission of conventional automobiles. Energy is lost in the discharging and recharging of electric- vehicle batteries. All of these energy losses beget various cost and environmental con sequences. The relative importance of these consequences depend in the first place upon the mix of fossil fuel, hydro, and nuclear generating stations. Also much involved are the demographic features, life-styles, and infrastructures of the society. It should come as no surprise that many assertions about electric vehicles vs. gasoline autos essentially compare apples and oranges.
If one attempts a consensus of electric vehicles predictions, a list of generalized statements can be compiled. Of course, all bets would be off in the event of a dramatic technological breakthrough on either side. A battery or fuel cell clearly able to extend presently practical ranges by a factor of five could speedily usher in the electric vehicle era. By the same token, a combustion technique extracting double the mechanical energy at one quarter the toxic emissions from the gasoline engine would likely ensure retention of this locomotion mode. In any event, the generalized statements that presently appear valid are as follows:
• The public wants more than performance suitable for nearby shopping excursions. Payload, acceleration, speed, cost, and range should not lag far from that attainable in a small gasoline-fueled economy car.
• Toxic fumes, such as carbon monoxide, carbon dioxide, nitrogen oxide, and ozone will be much reduced in urban areas. Sulfur dioxide will tend to be in creased in the fossil-fueled generating station, but it will be much easier to cope with this than to suppress emissions from millions of automobiles.
• Despite fancy numbers attributed to a host of exotic chemical formats, the first batteries are likely to be advanced lead-acid, nickel-iron, and in more limited number, nickel-cadmium types.
• These rather mundane batteries will eventually give place to more sophisticated types involving more reactive electrodes such as lithium or zinc. Some of these will be air breathing, and will otherwise resemble fuel cells. Polymer and other solid electrolytes will merit serious consideration, but preference will be given to those formats that can operate at ambient, rather than elevated temperatures.
• Both dc and ac motors will probably be used. However, dc motors could gradually shed their brushes and commutators. As time goes on, there might be less difference between dc and ac motors because both will be heavily dependent on the logic of control electronics.
• Many small companies will likely get into the act, but domination will be at tempted by the “big-three” auto makers. Small firms will have to be nimble and innovative to qualify for a slice of profits from the electric vehicle pie. Advertising hype will be dangerous to both small and large manufacturers— claims of extend range that pertain to unrealistic traffic conditions will damp the public's enthusiasm for electric cars.
• The smoothness, quietness, and maintenance-free (almost) features of electric vehicles are bound to win favor. The manufacturers must not compromise the inherent reliability of the electric vehicle with cost-cutting, but unreliable electronics.
• If electric vehicles get off to a good market start, a snowball effect known to economists as the “learning curve” will set in and costs will dramatically de cline. Accompanying this will be the less tangible, but never absent, unexpected technological advances.
• In popular literature, the public is often influenced to expect a large energy contribution from solar cells appended to the vehicle. Unfortunately, even if solar cells could attain efficiencies of 50 percent (rather than 10 - 15 percent in mundane varieties) there is not sufficient surface area to gather in much energy. However, in some cases, a solar panel on the roof can provide some useful energy. It does not appear likely to become a common feature because of its fragility and vulnerability to dirt, and its reliance on the vagueness of weather.
• The public is also fed distorted information about the benefits of regenerative braking. It appears like perpetual motion in action because energy ordinarily expended to heat brake linings is, instead, directed back into the battery. It turns out that in most driving, relatively little energy is recovered. However, the possibility of increasing range by even a few percent will not be over looked. Also, the mechanical brakes will last longer when preceded or assisted by electrical deceleration imposed by regenerative braking. Accordingly, this feature will be in evidence if for no other reason than its psychological appeal—obtaining a measure of “free” energy.
• Very likely, some type of hybrid format will also appear—one utilizing electrical propulsion assisted in some way by a small internal-combustion engine. In such a format, a worthwhile compromise might be realized where the most desirable features of electric and heat-engine propulsion are blended. It is conceivable that the gasoline-fueled engine would be used to charge, or to help charge, the battery, rather than be coupled to the drive shaft. It has also been proposed that a small gasoline engine could be used to actually power the wheels of the vehicle, but when a burst or increase of power was needed for acceleration, passing, or bill climbing, an electric motor would be energized from the on-board battery.
• There is likely to be both overnight-charging at home, and a number of strategically located quick-charge stations. Also, for safety reasons, charging energy can be supplied to the vehicle battery via inductive pickup.
• Advertising hype commonly omits mention that operation of amenities, such as vehicle heating or air conditioning, necessarily subtracts from otherwise available range.
• Although the knee-jerk reaction is to reject battery formats that have to operate at elevated temperatures, such as the sodium-sulfur type, such electrochemical systems posses an important feature denied to batteries that are said to operate at ambient temperatures. The very fact that elevated temperature batteries must be provided with superb thermal insulation to prevent heat leakage to the environment endows such a system with a remarkable feature; the same thermal insulation that inhibits heat leakage from the exotic battery also immunizes the battery from the effects of wide ambient temperature swings. Thus, such batteries will suffer minimal performance degradation in both, frigid and torrid climates. This feature came “along with the ride” in the thermal design primarily intended to inhibit battery heat from escaping.
• When one evaluates information on new battery systems, the most useful data is that expressed in terms of how the parameters compare to those of the lead-acid battery. Thus, if we read that, compared to lead-acid batteries, newly developed battery “X” has twice the specific energy and one and one half times the specific power, but only a quarter of the life span measured iii charge/discharge cycles, we gain a practical idea of the new battery's merit, especially if some relative costs accompany such comparisons. However if our data is couched in terms of BTU per pound, Kwh/Kg, or Joules per cubic-inch, chances are good that we will wind up comparing apples and oranges. Inconsistent use of energy and energy- density units, as well as speed and range, loom as the major reason for much conflicting comparisons of batteries. Sometimes these erroneous evaluations are rather subtle, such as erratic and careless use of miles per hour and kilometers per hour. Unfortunately, these inconsistencies have a habit of passing the scrutiny of the author, the editor, and the reader!
• Admittedly, many statements invested with technical integrity at the time of writing, stand destined to best be taken “with a grain of salt” after passage of more time. This is due to the state of flux electric vehicle technology finds it self in. Experience teaches that a rapidly evolving applied science is full of unanticipated surprises. An abrupt breakthrough in a related device, such as electrolytic capacitors, or an unsought phenomenon in another energy investigation, such as the controversial “cold fusion”, could dramatically impact electric vehicle technology. Indeed, once the electric vehicle gains a foothold in the market, its further progress will appear to feed on itself.
• Finally, “far-out” technology some of which we have only had tantalizing glimpses, might provide future mutations of the electric-vehicle art. These include high-temperature super conductivity, conducting polymers, 90%-efficient solar cells, replacement of electrochemical cells by rotating flywheel energy-storage devices, association of metal-hydride storage gas with electric motor propulsion, and the like. Note that we do not base our prognostications on UFO phenomena, but rather on projections of known principles. Two of these possibilities are illustrated in Figs. 8 and 9.
The amount of mechanical energy that can be stored in a rotating flywheel is surprising. Feasibility tests indicate specific energy levels of at least several times that of lead-acid storage batteries, with possibilities of even higher values. The simplified drawing of FIG. 8 depicts the basic setup underlying a practical implementation. The space constraints imposed by an electric car prevents the use of a large-diameter flywheel. Also, traditional flywheels made of heavy metal tend to “explode” from centrifugal force if spun too fast. The solution to this problem is to use several relatively small wheels rotated at great speed. To be sure, kinetic energy is lost with the reduced diameter, and also because a light composite material is used. However, much of the lost energy can be regained if the speed of rotation is great enough. This is because the energy increases as the square of the speed. The composite material provides a safety feature, for its failure mode is more like a collapse than an explosion.
Lower magnetic bearing; High spin rate (100,000 RPM in experiments); Flywheels of light composite material; Stator winding; Stator windings
Magnetic bearings are used (details not shown), and the structure is housed in an evacuated chamber. Thus, friction and windage losses are exceedingly low; once “charged” to a high spin rate, the energy of rotation tends to maintain itself. It is like having a battery with a very low internal current leakage. A permanent magnet is also carried on the rotating shaft so that electricity can be generated in externally mounted stator windings. With suitable electronics, this assemblage can also function as a motor; in this way, the system can be “charged” by bringing the flywheels up to speed.
Another “high-technology” format for an electric vehicle is shown in the simplified drawing of FIG. 9. Here, hydrogen gas is stored in an unusual container. It is then fed to a fuel cell where it mixes with incoming oxygen from an air intake, and thereby produces electricity, while exhausting hot water. Of course, the electrical energy can be utilized in various ways. In the drawing, a three-phase inverter is used in order to supply power to an induction motor, a synchronous motor, or a brushless dc motor. The heart of this scheme lies in the relatively safe means of storing the hydrogen gas. The hydrogen is not simply “contained” in the special alloy tank. Rather, it is absorbed in interstitial microscopic spaces in the metallic crystal structure. It is a phenomenon hard to imagine in terms of everyday experiences at the macroscopic level, but more hydrogen can be stored in this way that could be carried by a like sized tank filled with liquefied hydrogen. (A workable, but unsafe storage technique). Such alloys are known as metal hydrides.
For the hydride to release its absorbed hydrogen atoms, it must be heated above the ambient temperature. Once such an electric vehicle was operative, it is likely that this could be accomplished with the hot-water exhaust from the fuel cell. Initially, however, heat would have to be obtained from an auxiliary source, such as lead-acid batteries carried along for the specific tank of starting the system.
Cold fusion, hot debates, and tantalized electric vehicle enthusiasts
Probably second in fervor only to the UFO controversies have been the allegations of “cold-fusion” that some people claim to be readily achievable with simple apparatus bearing resemblance to an experimental setup for demonstrating electroplating. Fusion just happens to be the process responsible for the energy released by the sun and the stars wherein temperatures of tens-of-millions of degrees are involved. Basically what happens is that hydrogen atoms are caused to fuse together to form he hum, together with the release of energy. It is a much cleaner process than the fission process used in our atomic utility plants, inasmuch as it is not accompanied by much of the toxic and radioactive substances associated with atomic fission. Accordingly, scientists have been seeking methods of producing controllable fusion for a number of decades. Their general technique has been to generate extremely high temperatures and pressures in a small pellet of material for very brief time durations. Very expensive laser equipment, electromagnets, and instrumentation has yielded encouraging, but not practical results.
You can imagine the consternation of these pursuers of “establishment science” to awake one morning and read about fusion demonstrated via the use of a simple electrolytic cell. On the one hand, there seemed to be valid grounds for denouncing the claims as a hoax of the caliber of periodic “inventions” of perpetual motion. On the other hand, there surely was an unholy blend of “sour grapes,” and “how in the world did I overlook this discovery?” Amidst gnashing of teeth, charges, and counter chargers, scientists, physicists, chemists, and home experimenters reported a con fusing array of results. The excitement over the matter is easy enough to account for; after all, the potential energy in a cubic foot of sea water is about equivalent to that in 10 tons of coal. The mention of sea water is appropriate because it is made up not only of “ordinary” heavy water is formed of deuterium and oxygen atoms. Deuterium is an isotope of hydrogen, identical in its chemical properties, but containing an extra neutron in its atomic nucleus.
In the initial claim of cold fusion, current from a battery was passed through a cell comprised of palladium electrodes immersed in a heavy water electrolyte. Measured heat evolvement from the cell exceeded that which should have been generated from purely chemical reactions. Also, it was thought that helium and neutrons were given off from the cell—an accepted proof of nuclear phenomena. The general idea might be gleaned from Fig. 10.
Later, other experimenters confirmed the excess-heat observation, but not many detected helium or neutrons. This led to a popular consensus that an unusual chemical reaction might be involved, but there was also the assertion that most investigators were guilty of sloppy heat measurement techniques. This school of thought maintains that very thorough mixing of the liquid in a vessel is necessary be fore attempting to record temperature rise.
Whether or not otherwise-competent scientists possess sufficient sense to properly agitate a liquid bath in order to uniformly spread its temperature is a mute point. And whether any excess heat comes about because of atomic fusion or because of enhanced chemical activity, the practical relevance to electric vehicles demands further investigation. The question that must be answered is whether the process of energy generation, if it indeed exists, can be harnessed to produce electricity on a greater energy-to-weight ratio than has been possible, practical, or economic from mundane and exotic batteries and fuel cells. The tantalizing aspect of the matter is that we are again dealing with an electrolytic cell, one that is all too suggestive of both voltaic and fuel cells.
Adding to the mystery of the claims is the use of palladium electrodes. This metal has been long used as a catalytic agent, a substance that speeds chemical reactions without itself undergoing chemical change. This is interesting because catalytic action, like gravitation and magnetism although well enough understood to manipulate its use in our technology, its true nature continues to be a fuzzy enigma. Fuel cells also are heavily dependent on the presence of a catalytic metal. It should not be an exercise in idle speculation to ponder why the two devices share this common feature.
Aside from the theoretical arguments of the physicists and chemists, a suggestive experiment was carried out at the Stanford University engineering department. Two identically arranged systems were monitored for the presence of excessive heat. In one, however, ordinary water was used; in the other, heavy water was used. It was found that heat evolvement from the cell with ordinary water was possible to ball park from computations. This was construed to be the expected “chemical” heat. The heavy-water cell yielded considerably more heat energy as manifested by a greater temperature rise. Because the same operating conditions prevailed for the side-by-side setups, one is led to suspect energy release from an unknown source. Assuming the experiment to be valid and repeatable by others, one would be more inclined to bend theory to fact, than vice versa. It is fitting to recall that a great mathematician once announced heavier-than-air flight to be impossible (of course, bumble bees are not mathematicians).
I feel that whether it will be called cold fusion, a fuel cell, an exotic battery, or a trillion-farad capacitor, some solution to the energy-storage barrier now limiting the performance of electric vehicles will be found. In the meantime, people will continue upgrading the efficiency and capability of electric motors, and must necessarily pay inordinate heed to such matters as vehicle weight, payload, aerodynamic streamlining, and tire-to-road traction.
“Horse energy”—food for thought
Our digression into the controversial “cold fusion” phenomenon, concluded with the suggestion that even if the alleged excessive-heat energy was not from fusion at all, it merited further investigation as a high-yield chemical reaction—one more exothermic than anticipated from conventional theory. I find that this leads to another interesting speculation.
Consider the strength, endurance, and word capacity of the horse. The fuel of this biological machine is simply grass or hay. Chemical oxidation of this fuel would seemingly provide only a small fraction of the horsepower-hours of work the noble steed performs in the service of man. Where, indeed, does this animal's energy come from? From the hay, to be sure, but via the digestive process under the influence of enzymes. And what are enzymes but biological catalysts performing similar tasks to the inorganic catalysts in more ordinary chemical reactions, and in fuel cells, auto mobile exhaust converters and apparently, the palladium electrodes of cold-fusion cells? Incidentally, the horse is not unique—the migratory flights of birds over continents and oceans wherein they might be buffeted by raging storms and impeding winds also exemplify this mystery. Here again, the derivation of the required energy surely does not come from bugs, worms, and seeds in the form of simple chemical breakdown. Nature harbors a secret here; can we find it?
Because this book is primarily devoted to motor and control technology, these speculations of mysterious energy sources will not be further expounded. The brief mentions that have been made are, of course, relevant to the future of the electric vehicle. It is encouraging that the sought energy-storage device need only surpass the performance parameters of the lead-acid battery by factors of three, four, or five in order to provide ranges of several-hundred miles at freeway speeds, and with practical payloads. Although, battery improvement has been somewhat disappointing, it nonetheless appears that too much magic is not needed; a favorable blend of technical, economic, and psychological factors is bound to bring about wider use of electric automobiles. It is certainly true that the electric motors and control techniques we have investigated are reasonably ready for the task.