STATEMENT SUBMITTED TO THE SUBCOMMITTEE ON SCIENCE, RESEARCH, AND DEVELOPMENT BY GEORGE A. HOFFMAN, UNIVERSITY OF CALIFORNIA, AUGUST 17, 1966 ENERGY REQUIREMENTS FOR ELECTRIC AUTOMOBILES (By George A. Hoffman, research engineer, Institute of Government and Public Affairs, University of California, Los Angeles, Calif.) I. INTRODUCTION: WHY ELECTRIC AUTOMOBILES? Automotive propulsion accounts today for about half of the energy generated by combustion in the United States. A review paper on the energy requirements of automobiles-particularly electrically driven cars appears therefore to be appropriate for this first conference on energy conversion. The internal combustion engine was not always the favorite energy conversion device for propelling passenger cars. At the turn of the century there were more battery-operated, electric motor cars in use in this country than either steam or gasoline powered. But the severe range and speed limitations of storage batteries in those days soon doomed the electric car for oblivion. Quantity demand and production of electric automobiles ended half a century ago. But in the last decade or so some automotive trends specifically favorable to the reconsideration of electrically driven passenger cars have developed. For example: Electric motor design has progressed very rapidly in recent years. Improvements in electromechanical conversion efficiency and in weight reduction are now at the point where the electric motor merits reinvestigation for automobile traction. In the past decade, the weight of batteries and regenerative fuel cells per unit of stored energy has dropped to a small fraction of their value of a half-century ago. The large increase in air pollution from the exhausts of the internal combustion engine has become a serious national problem. The socioeconomic losses due to degrading the quality of the air we must breathe might yet force installation of smog control devices on cars costing as much as the engine itself.1 Batteryoperated electric cars do not contribute significantly to air contamination. The demand for cars per capita is increasing with a related proliferation in diversity of automobile models. The rate of increase is greatest for the second car in the U.S. family, used NOTE. The views expressed in this paper are those of the author. They should not be interpreted as reflecting the views of the institute nor of the university, or the official opinion or policy of the sponsors of this study. 1 George A. Hoffman, "Los Angeles Smog Control," Rept. MR-56, Institute of Government and Public Affairs, UCLA, March 1966. either for commuting or for household-type trips, and characterized by more missions than the first car, but of shorter range. These suburban cars appear the most readily adaptable to electrical conversion. Consumer prices for gas and oil are rising proportionately faster than the price of electricity, and will do so for the foreseeable future. Electric propulsion of ground vehicles is therefore steadily becoming more attractive economically. Automotive energy conversion would be more efficient and operating costs cheaper if non fossil electrically regenerable fuels were used. For these reasons, the design of the electric car is reviewed here with estimates of its energy requirements. II. GENERAL MAKEUP OF ELECTRIC AUTOMOBILES Automotive marketing history shows clearly that it is almost impossible to successfully introduce a radically changed car to the motoring public if it departs too noticeably from the established demand and acceptance criteria of the time. To be popularly wanted, manufactured, and sold in large numbers, electric automobiles should conform to the major characteristics of conventional gasoline engine cars. This requirement spells out most of their basic design criteria. Electric cars should therefore be engineered to resemble or excel present-day cars in most of the following respects: General appearance and diversity of models; Convenience, comfort, passenger capacity and protection, interior design; Performance, top speeds; Costs, initial and operating. After a century of development, the weight composition of automobiles has been dictated by the consumer to reflect the above six points and others. For the great variety of cars on the road today, ranging in curb weight (takeoff gross weight) from 1,500 to over 5,000 pounds, the weight composition is remarkably uniform, both as to proportions of weight and as to linearity with curb weight. Figure 1 is an illustration of the consistency of the weight ratios of major component categories of 1966 domestic and imported models, designed for the above set of criteria. These ratios are listed in table 1 for 16 component subgroupings, and are the starting point for any successful design of electric cars. Basing the design on the ratios shown in table 1, assures that the driver at the wheel and his passengers perceive little difference in driving, or riding in, an electric auto versus a conventional car. Figure 2 shows this undifferentiability either from the interior or the exterior of the car. Eliminating those components that are not required in electricmotor propulsion would at first give the weight composition of electric cars shown in the left-hand column of table 2. It is assumed that the least-value ratios from table 1 represent the better engineered product in current demand. But there are advantageous side effects on each of these components in going to battery operation and electric motors. Some of the weight reductions and alterations applicable to each category are also enumerated in table 2, with an estimate of the weight fraction decrease. The right-hand column shows the finally altered component weight of electric cars as portions of curb weight. |