At full blast they are the most efficient engine in any vehicle, but most land vehicles rarely use all of their power all of the time. Thus conventional Diesels and Gasoline beats gas turbines when it comes to idle or when they are stuck in traffic going 25 mph.
On the other hand a gas turbine with an electric drive system "solves" this problem by having the gas turbine go full blast when it is on, any extra power produced goes to charge the batteries, and when the batteries are charged, the turbine shuts off. Thus the advantage of the gas turbine are used to its max.
The downside is you are looking at a truck with two engines in it (an electric and a gas turbine) and all of the weight that brings with it. In the hybrid automobiles this has been a problem, they do NOT get the fuel economy they could do to the weight of the two engines and the batteries (and have a harder time meeting the EPA fuel economy number then do conventional cars).
On the other hand an electric drive has several inherent advantages. First electric drive can provide more power to the wheel then conventional power cars. This was one of the reasons why the Railroad replaced steam with diesel locomotives. Diesel Locomotives are Diesel engines acting as generators of electricity that provide the power for the electric engines that drive the actual wheels of a Diesel Locomotive (in reality Diesel locomotive should be called Diesel-electric locomotives).
The big issue is the life span of most tractor trailers on the road. Here is a 1998 report on trucking, the report was on using natural gas to replace diesel, the report final decision was the only advantage was reduction in oil consumption, but Green house gases would NOT be reduced nor save energy. On the other hand the report is a great source on data about large trucks and the trucking industry:
The number of heavy trucks is much smaller than the number of light trucks and cars (totals: 47 million trucks and 146 million cars), but mileage and emissions for heavy trucks are high and fuel economy is low.
Heavy trucks averaged 60,000 miles/y in 1993 (8). At a typical mileage of 5 mpg, the 781,000 trucks in the largest class allowed nationwide consume more than 9.4 billion gallons (223 million barrels) of diesel fuel per year. This is about 8% of total U.S. highway fuel use and over 40% of highway diesel use.
Other sources indicate much higher annual mileages -- up to 250,000 mi/y for some trucks in the chosen category -- which would make their total fuel consumption much higher (9). Thus, this is an important class of vehicles to examine for possible reductions in fuel use and emissions
http://www.transportation.anl.gov/pdfs/TA/102.pdfFrom the same report (remember this is 1999, but I have NOT seen much improvements since the 1970s, when I saw a HUGE improvements in Trucks:
Table 3. Sources of Truck Power Demand
Source
...........................................Full Load,,,,,,,,,,,,Partial Load
..........................................(80,000 lb).........(65,000 lb
Aerodynamic losses.............. 45%.................... 49%
Wheel losses.........................35........................ 31
Drivetrain losses....................13.........................13
Accessory loads........................7..........................7
TOTAL................................... 100%.................. 100%
While aerodynamics is by far the #1 cause of loss of energy (under 50%), drive-train, wheel losses and accessory loads actually exceed aerodynamics (Those three exceed 50% of energy losses).
In 2002 a study found heavy trucks used 80% of all energy used by Medium and Heavy Trucks (Pickups are in the light Truck Category, so are Hummers)
http://info.ornl.gov/sites/publications/files/Pub37730.pdf
On page 1-19 of the above report, is an interesting chart. Oil use by Automobiles is about the same in 2012 as it was in 1970 (about 4 million barrels of oil a day). Light trucks have gone from under 1 million barrels of oil per day in 1970, to almost equal cars at about 4 million barrels a day in 2012. Heavy trucks have gone from 3/4 of million barrel per day in 1970, to almost 3 million barrels a day in 2012. Off road has gone from 1/2 million barrels a day to 1 million barrels a day (and I suspect this is affected by Jeeps, which was in 1970 the principal "off road" vehicles, but today classified as SUVs and thus light trucks, while the All Terrain Vehicles took over the role of going off road). Marine has gone from 1/3 million barrels a day in 1970 to over 2/3 miillion barrels of oil a day. Railroads seem to have held onto about 2/4 of a million barrels a day, i.e. the a slight drop in oil usage betwee 1970 and in 2012. Air has gone from 2/3 million barrels a day to over 1 million barrels a day.
Please note the above is my observation of that chart, the exact numbers will be different, but it was an interesting graph.
Actual Numbers were on the next chart, here they are, in thousdans barrels of oil a day:
Year.....Cars.....Light... ...Light ....Motorcycles...Buses....Class....Class....Heavy.... Highway....Total
........................Trucks...vehicle........................................3-6........7-8......Trucks.....Subtotal....Transportation
..................................subtotal.......................................Trucks...Trucks
1970..4,424......803.......5,227..........4..................62........140........598......738........6,031............7,333
2010..4,395...4,193.......8,588........28..................90.........557....2,375...2,933.....11,639..........13,548
Year........Air......Water........Pipeline.....Rail.........Nonhighway.....Total
............................................................................subtotal.........Transportation
1970.....625........381...............43.........253........1,302................7,333
2010..1,040........626................3..........240.........1,909.............13,548
Thus 61% of oil usage in the US is in cars and light trucks, which basically means personal transportation to and from work, school and other activities.
On page 2-4 of the above report, it indicates that renewable sources of electricity DECLINED from 14,4 % of all electricity produced in 1973 to 12.5% in 2012. This mostly reflects that the
percentage of electrical power provided by Renewal resources have decline since 1970 for the following reasons
1. very few hydro electrical plants came on line and thus the electricity from hydro-electrical plants, even as the total INCREASED, it was small compared to the other plants that came on line (mostly Nuclear in the 1970s).
2. The other renewables sources of energy are still minor compared to hydro-electrical generation
3. Nuclear went from providing 4.6 % to 20.9% of all electricity produced in the US
On Page 2-14 of the report is an interesting fact. While they are a 1/3 more cars then they are light truck and in miles driven, Cars put 50% more miles on the road in a year. Remember the above table, where Light Trucks use just under what Cars use.
On page 3-11 another chart compares the AGE of cars in 1970 with the age of cars in 2001. Only 2.9% of all cars were older then 15 years old in 1970, today that percentage is 16.1%. For comparison, on page 3-12 are the age of trucks, 15.3 of all trucks were 15 years or older in 1970, in 2001 it was 17.3%, roughly the same. We are retaining and keeping cars that we would have junked in 1970.
On Page 3-18 a chart shows the "Medium Life" of a HEAVY Trucks, today it is 28 years, in 1970 it was 20 years.
On page 4-19 shows a chart of MPG affected by speed, In 1997, the last year given, peak MPG was 50-55 mph. Please note this was an EPA test, using EPA equipment. Thus EPA testing procedure was followed. While the EPA test was valid of comparison purposes in the 1970 (People even then complained that they did not get what the EPA claimed, but what you would get was NEVER the purpose of the test, the test was to be standard so that you could say with confidence that a car with 20 mpg would get better mileage then a car with an EPA of 19 mpg, the test was NEVER intended to show what people would get).
Anyway, as computers took over more and more of the functions of the car in the 1980s, car makers started to program the computer to do the best under the EPA test condition, one of which was a speed of 50 mph. Thus under the EPA test the car would get its best fuel economy at 50 mpg, which is what the chart on Page 4-19 shows. No one drives the way of the EPA test and with the policy to gear the computer for the EPA test, in many ways the EPA test is no longer valid. You can get better mileage, but that requires you to understand the computers driving your car are geared for 50 mpg. It is so bad that in EPA tests Automatics Which since the 1980s are computer computer controlled) are getting close to Manual transmission, while in real life the difference in actual fuel economy is as large as it has ever been.
Just a warning about the chart on page 4-19, interesting, but understand the limitations of the EPA tests and the efforts to work around the EPA test the auto companies have been doing since the EPA test became the only mileage Auto Companies can use in the US.
On page 8-1. shows a summary of the studies of people and their vehicles:
Table 8.2
Vehicles per capita, 2010............................. 0.777
Vehicles per licensed driver, 2010................ 1.14
Vehicles per household, 2010........................1.79 .
Table 8.3
Average household transportation expense, 2010.......... 16.0%
Table 8.5 Share of households owning 3 or more vehicles
1960...... 2.5%
1970...... 5.5%
1980.....17.5%
1990.... 17.3%
2000.....18.3%
2010.... 19.5%
Figure 8.1 Average occupancy rates by vehicle type, 2009 (please note later on a actual chart show home to work is only 1.2 people per vehicle, it is the other uses of vehicles that increase the average above 1.2)
Pickup Truck.....1.49
Car...................1.55
Sports Utility....1.90
Van..................2.35
Table 8.10 Average annual miles per household vehicle, 2009........ 11,300
Table 8.16 Share of workers who car pooled, 2010............................ 10.4%
Table 8.21 Long-distance trips in the United States, 2001
Person-trips ..................................................................................2,554 million
Off the people surveyed, they said 61 % of their trips were then less the 6 miles, but that fell to 42.9 if the trip was to work (see page 8-15 of the report)
One-vehicle household drives 29.0 miles a day with a total of 10,600 miles per year, and drives a 9.0 year old car.
Two-vehicle household, drives the first car 43.6 miles per day. 15,900 per year and averages 7.6 year old.
The second car is driven 21.4 miles per day, and 7,800 miles per year and averages 9.0 years of age
page 8-18 of the report.
On page 8-20 it is reported, 76 % of people drive alone to work, another 10.4% car pool
2.7% use a bus, less .1% use a Streetcar, 1.6% uses a subway. .5% uses a Railroad
.2% use a motorcycle, .5% use a bicycle. 2.8% walk to work and 4.1$ work at home.
Sorry, about the above, but the report was interesting and I got caught up reading it. The numbers show we are NOT prepared for any real reduction in the supply of oil and if that does not worry you, it should.
= new reply since forum marked as read
and a cab wide enough for a passenger seat so you'd have a place for your Qualcomm, load documents or team driver, and that got...oh, 12mpg...would find a following.
