By Dennis Polhill
CE 172 Urban Transportation Planning
Prof Matzzie

Table of Contents

I. Problem Definition

The first indication of an energy shortage came in 1965 with the Northeast blackout The problem became particularly serious in April of 1973 It was then that the U S became fully aware of its dependence upon foreign energy It was decided that the U S should strive to be energy self-sufficient by 1980.

A large portion of the US energy consumption is for the purpose of transportation This is shown by Figure 1, Energy Utilization Pattern – 1970 Transportation constituted 22 3;0 of the total US energy consumption.

Figure 01 – Energy Utilization Pattern 1970

Figure 1 also shows that vehicles are only 25Yo efficient in terms of useful utilization of energy consumed

The most significant utilizer of transportation energy is the automobile The automobile, in particular, has several inefficiencies inherent in its design and added by luxury providing subsystems Thus, the automobile utilizes the 25″0 useful energy output of the power-plant at an efficiency of about 2~~ for a total efficiency of 2TIo x 25;o equals 5%

Since oil creation in nature is a process which takes 600 million years, the supply of available oil, both globally and nationally, can be considered as a fixed and limited amount

The extent of available oil in nature is a question which has received much study. Two of the most reputable projections are shown in Figure 2.

Figure 02 – Oil Limitations

The above are facts and are sufficient to lead one to the conclusion that major changes are in order to reduce or supplement energy needs related to transportation

It is beyond the scope of this paper to study the feasibility of concepts which might reduce the need for transportation through changing life-style, such as mass utilization of advanced telecommunication systems or major adjustments in land use priorities In other words, it is assumed that there will be a need for automobiles in the future

It is also assumed that major technological changes in the automobile as we know it today are unlikely This assumption, though beyond the scope of this study, is somewhat substantiated by the recent United States Department of Transportation predictions for the year 2001:

1. There will be a greater variety of specialized – vehicles, powered largely by diesel and sterling cycle engines

2. Fuels will be 20-30i6 blends of methanol, diesel fuel, liquefied coal, gasohol or cellulose products

3. Fuel will be $2 00 per gallon but cost per passenger mile will have increased only 25-100io

4. Trucks will operate in designated lanes with a — single tractor pulling 3 to 12 trailers with axle loads of 40,000 pounds

5. Carpooling will be an established way of life

6. Control technology will have been developed and will permit vehicles to travel at much closer headways. All major cities will have exclusive bus lanes and several automobile restricted zones

II. Energy Alternatives

The sources of energy are: nuclear fission, nuclear fusion, geothermal, solar, wind, tidal, hydroelectric, chemical and fossil For practical use in transportation, all except chemical and fossil require the development of fixed-location electrical generating plants, electrical energy storage and utilization capabilities of automobiles Generating capabilities would have to be tripled to meet the transportation demand Considering the time necessary to develop generating capabilities and the retooling, capital investment and economic impacts on automobile related industries, it is unlikely that sources other than chemi-cal and fossil can be significantly implemented before 2000 as long as chemical or fossil fuel is available

As available oil reserves dwindle and as the rate of discovery of new reserves continues to decrease, the U S, will become more and more dependent on foreign oil The need for oil, per se, may be subverted by technological breakthroughs which appear to be near

Coal liquidification may be achieved by catalytic hydrogenation, solvent extraction, pyrolysis or indirect liquidification Several approaches to coal gasification are already in the demonstration phase:- Chicago, Illinois; Rapid City, South Dakota; Bruceton, Pennsylvania; Homer City, Pennsylvania (to open in 1976) The most ambitious demonstration plant is at New Athens, Illinois, and is under construction at an estimated cost of $237 million

It is reasonable to expect that a synthetic oil substitute derived from coal will be technologically and economically feasible by 1980 Commercial development of such processes is not likely to be sufficient to eliminate dependence on foreign petroleum until 1985

There is sufficient coal in the United States to last 400 years In addition the development of technologies to remove oil from shale are within sight At least 54 billion barrels of shale oil could be derived just from the deposits in Colorado, Utah, and Wyoming

If fossil fuel is to be used, the problem is somewhat complicated by the commitment of the U S to clean up the environment This commitment is expressed in the Clean Air Act of 1970 (PL 91-604) which established emission standards for passenger vehicles:

The use of fossil fuels is merely the process of releasing solar energy stored by plants in the form of chemical energy Other types of chemical energy may be utilized in resolution of the energy problem Such processes use energy from other sources in a more convenient manner The most promising form of chemical energy is hydrogen: Initial indications are that it can be used in gaseous form as a substitute for natural gas The application of liquid hydrogen to the transportation issue may be the simple solution to the complex problem everyone is looking for Hydrogen can be burned in either internal or external combustion engines Thus societal adjustment to a new system would be minimal The emissions from hydrogen combustion are water vapor No energy is created by the manufacture of liquid hydrogen Hydrogen must be generated by dissolution of water through electrolysis (or other process) The energy of electrolysis is equivalent to the energy of hydrogen combustion Thus, development of hydrogen technology would create a significantly increased demand for electrical power Therefore, chemical energy falls subordinate to the development of electrical generating capabilities originating from other energy sources Use of liquid hydrogen merely offers a perhaps more convenient way of trans-porting energy in the freewheeling vehicle Chemical energy is not a viable alternative energy source before the turn of the century Some interesting characteristics of liquid hydrogen are represented in Figure 3.

Figure 03

In summary, heat engine technology will remain the predominant form of powerplant for freewheeling vehicles through the turn of the century Subsequently, the United States will move more and more in the direction of the all-electric society The rate at which this change occurs will be dependent upon the progress of research in several areas Magnetohydrodynamics (MHD) could increase electrical generating efficiencies to 60,70 (almost double) PHD systems convert coal to hot gas that moves at high velocity through a magnetic field to produce direct electrical power Figure 4 shows the energy utilization pattern of an all-electric society.

Figure 04 – Energy Utilization (30 to 100 Years Hence)

III. Practical Alternatives – Description

Figure 5 shows eight practical alternative heat engines of which prototypes have been constructed and are being tested They are divided into two broad categories: internal combustion engines (ICE) and external combustion engines (ECE) Within the ICE category there are two types: spark ignition engines (SIE ) and compression ignition engines (CIE) Under SIE both uniform charge ignition (UC OTTO) and stratified charge ignition (SC OTTO) are applied Both the uniform charge and stratified charge are applied using both the reciprocating (conventional) and rotary (Wankel) principles

Figure 05 – Alternative Prototype Heat Engine Technologies

The CIE is embodied in the diesel. A rotary CIE would be possible but has not yet been attempted; only the reciprocating principle is utilized.

The ECE are divided into open cycles and closed cycles. The Brayton or gas turbine is the only prototype consideration in this category. Within the closed cycle group, both condensing working fluid and noncondensing working fluid are possible. The condensing working fluid is exemplified by the Rankine (steam) engine. The noncondensing working fluid is exemplified by the Stirling.

1 – 2. UC Otto – Figure 6 shows the operation of the conventional uniform charge, spark ignition, internal combustion engine Most people are familiar with its operation – intake, compression, power, exhaust The rotary engine uses the same (otto) cycle – intake, compression, power, exhaust, but accomplishes it by means of a rotary principle rather than a reciprocating principle The rotary appears not to offer significant advantages in fuel economy and emissions control over the reciprocating Figure 7 illustrates the rotary engine operation.

Figure 06 – Uniform Charge Otto

Figure 07 – Rotary Engine

3 – 4. SC Otto – Figure 8 shows the operation of the direct injection stratified charge, spark ignition, internal combustion engine- It utilizes the same principles as the uniform charge with the exception of the gas dynamics within the combustion chamber The principle of the stratified charge is to utilize variable fuel/air concentrations throughout the combustion chamber to maximize combustion, maximize power, and minimize emissions Several techniques have been attempted including use of precombustion chambers, direct fuel injection, and staged-combustion compound engines If the injection, ignition, fluid motions, and combustion can be made to follow the arrows in Figure 8, the full potential of low emissions and fuel economy can be realized The stratified charge principle is being used both in reciprocating and rotary engines

Figure 08 – Stratified Charge Otto

5. Diesel – The diesel engine is a compression ignition engine (CIE) of the ICE class It functions by intermittent combustion in which the fuel is ignited by the high temperature of the induced air after compression A diesel engine is shown in Figure 9.

Figure 09 – Diesel Engine

6. Brayton – The Brayton which is taken generally to be synonymous with the gas turbine is an external combustion engine (ECE) Figure 10 shows the hierarchy of Brayton type engines being studied Figure 11 illustrates the differences in operation of the four types of gas turbines.

Figure 10 – Brayton Engine

Figure 11 – Brayton Engine

7. Rankine – The Rankine engine is a closed cycle ECE Figure 12 shows several alternative types of the Rankine The Rankine is generally referred -to as the steam engine Its operation is illustrated by Figure 13

Figure 12 – Rankine Engine

Figure 13 – Rankine Engine

8. Stirling – The Stirling engine is a closed cycle ECE Its only difference from the Rankine is the fact that it does not condense its working fluid The advantage of this will become apparent in the comparative section The working fluid most commonly used is hydrogen rather than water in the Rankine The operation of the Stirling is exemplified by Figure 14

Figure 14 – Stirling Engine

IV. Practical Alternatives – Comparison

Figure 15 shows a plot of specific power (power per unit weight) versus specific energy (energy per unit weight) Specific power can be equated to acceleration and maximum speed. The Rankine and Stirling are lumped together and referred to as external combustion engines The several types of Otto cycles, including reciprocating and rotary engines and the diesel, are lumped together as internal combustion engines The gas turbine is represented separately as are fuel -cells and several types of electric battery vehicles Envelopes are generated The objective in this comparison is to maximize both power and energy (maximize both velocity and range) The superiority of the heat engine technologies reflects the need for additional research and development on the alternative technologies Among the heat engines the gas turbine appears to be superior

Figure 15 – Automotive Power Plants Specific Power vs Specific Energy
Figure 16 represents comparative emissions data The continuous combustion (ECE) powerplants have little difficulty meeting the emission standards The intermittent combustion (ICE) powerplants, with the exception of the diesel, can be squeezed to meet present statutory standards However, large ICE vehicles will have difficulty meeting the ultimate standards for hydrocarbons (HC) and nitric oxides (PiOx) at the same time

Figure 16 – Comparative Emissions

Figure 17 represents the comparative fuel consumption Both mature and advanced technologies are estimated and contrasted against the projected Otto technology Mature implies utilization of existing technology with minor improvements

Figure 17 – Comparative Fuel Consumption

Advanced implies some results from R & D efforts and is probably not producible until 1990 Among the mature technologies the Stirling is clearly superior Among the advanced technologies where gas turbine can more effectively exploit both high temperature capabilities and the potential for engine weight reduction afforded by ceramic materials, the Brayton takes first place over the Stirling

Figure 18 illustrates the projected energy consumption under three conditions:
1 No change in vehicle design or market mix;
2 The Otto engine evolves to the mature configuration; and
3 The Otto engine evolves to the mature configuration and then is replaced by the Stirling.

Figure 18 – Projected Energy Consumption.

The mature Otto would yield a 10% improvement in efficiency by 2000. The mature Otto replaced by the Stirling would realize a 37% improvement over no change by 2000

V. Powerplant – Independent Vehicle Improvements

From Section I, Problem Definition, it was stated that vehicle subsystems contributed significantly to the inefficiency of the automobile Thus, overall efficiency may be improved by powerplant-independent vehicle improvements Factors which effect vehicle efficiency are: weight, transmission losses, aerodynamic drag, accessories, and rolling friction By implementing vehicle improvements within present technological capabilities efficiencies represented by “intermediate technology” on Figure 19 can be realized (30’/ improvement by 2000) By implementing “long-term technology” those requiring some develop-ment and producible by 1985, a 43% improvement can be realized by 2000.

Figure 19 – Power Plant Independent Improvements

In addition to the above, some consideration is being given to the energy lost in braking. Braking accounts for 12:6% of the powerplant-independent losses. Several types of energy storing or energy recovery systems are being considered They include flywheels, batteries, and fuel cells

1. Flywheels – During braking energy which would normally be lost in heat in the brakes is transmitted to a flywheel and stored in the form of angular kinetic energy During acceleration the stored energy is transmitted to the wheels to reduce the load on the regular engine

2. Batteries – The principle is the same but not feasible with today’s battery technology During braking a generator is powered which charges storage batteries

3. Fuel cells – Where chemical energy may be utilized such as hydrogen, a hydrogen generating subsystem can be applied to the vehicle in which supplemental hydrogen fuel-is generated during braking through electrolysis powered by an electric generator attached to the braking system Advances are required before this system can become practical Other fuel cell fuels may include ammonia, hydrazine, or methanol

VI. Conclusion

The conclusion is inherent in the context of the report Heat engine technologies will dominate the transportation scene through the year 2000 (and possibly beyond 2050)

Energy supplies are available New technologies will create additional energy sources for heat engines Heat engine improvements can improve fuel consumption (37;o by 2000) Powerplant-independent improvements can reduce fuel consumption (43% by 2000) By 2000 it can be expected that heat engine powered vehicles will be nearly twice as efficient as those of today


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