A common enabler for all alternative fuels

[Harmonic_Subset]

Fuel contains only a certain amount of energy for a given volume. Therefore a given amount of fuel will only do a certain amount of work. The amount of work, and therefore fuel, needed to move a vehicle from A to B is determined primarily by the weight of the vehicle. That's because the weight directly affects the kinetic energy and the rolling resistance. This was first quantified by Sir Isaac Newton over 300 years ago:

Work done to move vehicle = Fuel burned

Fuel Energy = (n*KE) + (RF*d)

where,
n = number of stars and stops
KE = kinetic energy
RF = rolling friction
d = distance travelled

Expanding this formula in more detail gives:

Fuel Energy = (n*0.5*m*(V^2)) + (u*m*g*d)

where,
m = mass
V = velocity
u = coefficient of friction
g = gravitational constant

So you see vehicle mass is a factor in both terms of the equation. While reducing speed affects only one part of the equation, reducing vehicle mass affects both. The heavier the vehicle the more fuel is burned. Doubling the weight doubles the fuel consumption.

CASE STUDY:

Chrysler Sebring:
mass = 1520 kg
fuel economy = 30 mpg (gasoline)

FuelVapor Ale:
mass = 635 kg
fuel economy = 92 mpg (gasoline)
website: http://www.fuelvaporcar.com/

Clever Car:
mass = 395 kg
fuel economy = 110 mpg (natural gas)
website: http://www.clever-project.net/index.htm

Testing the Hypothesis:

Compared to the Sebring, the FuelVapor Ale has 0.418-times the mass, and should get 1/0.418 = 2.39-times the fuel econony, or 72 mpg. According to the website the FuelVapor Ale does better than that, getting 92 mpg. Excellent result, possibly due to the claim of an innovative fuel system and low air resistance. Appears to lack rear-view and side mirrors though, and these would be required to be street legal. Great looking vehicle all around, but low-slung and might not have good forward-looking visibility, and it still uses fossil fuel. No tilting mechanism required for cornering stability - one less thing that can go wrong. Top speed is 140 mph, great for freeway speed, and hackers could disable the electronic speed limiter and get even more out of the 180 hp engine! Waaaay outpowered for a car this size, but who cares right? Looks alot like the old Merlin Roadster from Corbin Motors (bankrupt 2003). FuelVapor still looks like one of those small startups with an uncertain future.

The Clever Car has 0.26-times the mass of the Sebring, and should get 1/0.26 = 3.85-times the fuel economy, or 115 mpg. According to the website the Clever Car gets 110 mpg equivalent using natural gas, very close to the expected performance. At the same time, the Clever Car might provide better visibility than the low-slung FuelVapor Ale, but needs a computer-controlled active tilting system for cornering stability. Top speed is only 60 mph, and this might be frustrating for people who like to use freeways (or even the passing lane). BMW is funding the development of this vehicle.

Conclusion:

While there are other factors that can improve fuel efficiency, reducing vehicle weight has the greatest effect. Compared to a basic sedan such as the Chrysler Sebring, the FuelVapor Ale achieved 240 percent improvement in fuel economy through weight reduction alone, while other factors such as their patented fuel vapor technology only gave them an additional 60 percent improvement. In other words, without any weight reduction the FuelVapor Ale might only have achieved 48 mpg fuel economy. This is not even as impressive as a hybrid car. However, similar analysis can show that hybrid cars also rely on weight reduction to exaggerate their improvement in fuel economy.

Factors that might reduce weight in any car:

- a car with one seat instead of four need only be 1/4th the size and weight
- frame and other parts made of lightweight material such as aluminum tube, aluminum honeycomb, aluminum-magnesium alloy, magnesium, plastic, or carbon composite
- 2-cycle engine has more power per cubic inch, and therefore less weight, than a 4-cycle
- engines with less horsepower tend to be lighter
- two or three wheels instead of four eliminates tires

Even Supermileage vehicles that get upward of 2000 mpg depend mostly on reducing vehicle weight to achieve most of their performance goals. However, these are all prototypes that operate under impractical track conditions, so other factors besides weight reduction can be significant under these unusual situations.

Additional factors include:

- high compression ratio improves carnot efficiency of the engine
- single speed transmission reduces losses between engine and wheels
- better lubricant improves mechanical efficiency of drive train
- properly balanced parts reduces vibration losses
- low frontal and planform area reduces aerodyamic drag
- laminar airflow over vehicle surface improves aerodynamic drag coefficient
- constant speed engine can be more easily optimized for high efficiency
- pure chemical fuel narrows combustion temperature range for more complete combustion
- removing catalytic converter improves fuel economy
- removing muffler improves fuel economy
- turbocharger improves fuel economy
- engine-off during overspeed, such as downhill stretches & while braking, reduces fuel consumption
- slick tires can reduce coefficient of friction
- high tire pressure can reduce coefficient of friction
- in-wheel electric motors can nearly eliminate mechanical losses
- regenerative braking using an electric, gas-charged, or hydraulic accumulator can reduce losses during starts & stops
- reducing the number of starts & stops reduces fuel consumption
- reducing top speed reduces fuel consumption
- a non-mechanical auxiliary power unit can replace an inefficient alternator
- no air conditioning or other power-hungry gadgets improves fuel economy

Generally though, it is the vehicle weight reduction that gives the best results. Unfortunately, cars that achieve vast improvements in fuel economy face a marketing dilemma best illustrated by this statement by an SUV driver:

Cristian Crespo of Valley Village, California, said he found it ridiculous that automakers hadn't yet come up with a way to combine fuel efficiency with luxury provided by a SUV.

"It's not that Americans don't want to be environmentally friendly, it's just that we don't have much of a choice," he wrote. "As an SUV driver, telling me that my only alternative is a Toyota Prius or a Honda Civic is like telling me to eat beef jerky when I'm used to filet mignon."

source: http://www.cnn.com/2007/US/07/06/fa.critical.mass/index.html

You can ignore the laws of physics, but the laws of physics won't ignore you!

 

[Billy T]

It is good that you try to make an analysis of the fundamentals, but you do have somer conceptual mistakes. The main one is that the fuel is related to the kinetic energy, and even this is partially correct. At constant speed, the kinetic energy is constant, and thus requires zero fuel. What is related to the KE is the loss due to wind resistence and the disipation of constantly flexing the different sectors of the rubber tires.

Perhaps a better approach, which will also show the importance of vehicle weight is to recognize that the energy released as the fuel is oxidized is all going to be in the form of heat when the car is parked again. At least half of this energy is immediately lost as heat out the exhaust pipe. As you must change your speed another large fraction is used to heat the brakes. The losses to the air, wind resistance is a strong function of speed, at least as the cube of the speed. the heat lossed tothe air by the hot tires (rubber flexing) is proportional to the distance traveled and you can pull part of the losses to the wind out with a distance factor alos if you like. ]For example air reasitance term could have a "D" factor and then perhpas only goes quadratically with speed. I.e. ~Dv^2.

Many of your conclusions are valid but they do not all follow from your analysis.

 

[spidergoat]

Can we just eliminate the personal car as a method of transportation? I don't think those that concentrate on alternative energy for cars really understand the nature of what is in our future.

 

[Harmonic_Subset]

I don't think you understood my formulas. The number of starts & stops is multiplied by the kinetic energy. You must accelerate at least once to get up to speed, and introduce n=1 into the equation. That burns fuel.

I purposely omitted aerodynamic drag for the following reasons:

- for simplicity,
- because it is insignificant unless you are driving a cube van or towing a U-Haul trailer
- and because most people drive at or near the speed limit regardless of what kind of car they are driving. All vehicles have roughly the same highway speed, and because most people want to get where they are going in a reasonable time, most will object strenuously to reducing speed limits.

I did mention reducing air drag coefficient and surface area as additional factors that can improve fuel economy. But unless you are driving a sailboat, it is most definitely not as significant as vehicle weight. Vehicle weight is the first thing that should be reduced. You can do all the other things, but if someone designs a car that is 20 percent lighter, their fuel economy will be better than yours and all your efforts at perfecting minutiae will be wasted.

Besides that, the direct link between weight reduction and increased fuel economy were borne out in the case studies that I provided.

 

[spidergoat]

You would have to make a comprimise between weight, safety, and cost. A light vehicle like a motorcycle is less safe. A light car made of carbon nanotubes would be expensive.

 

[Harmonic_Subset]

Indeed. And smaller cars have higher insurance premiums that cancel out any cost savings from higher fuel economy. Therefore a small lightweight car will not cost less, it will merely consume less fuel.

Also, there is very little reason to make huge improvements in fuel economy. There is presently no oil shortage, nor will there be for at least several years. And we will probably exhaust fossil fuel reserves before global warming really becomes a problem. We'll reduce our 'carbon emissions' by virtue of the fact that we will have run out of fuel. I'll be a very old man before I expect to see people zipping around in super-efficient single-seat commuter cars that don't weigh much more than their drivers. But at that time I also expect that we'll have little choice in the matter, since renewable fuels will be all that is left, and so everyone can still have individual freedom and mobility, car will have to be small and lightweight so as not to consume more than their fair share of fuel.

 

[Carcano]

Also, there is very little reason to make huge improvements in fuel economy. There is presently no oil shortage, nor will there be for at least several years.

Thats what some experts said in 1971, when the US was at the peak of domestic oil production.

When there was a 5% reduction in world production in the 1970s the price of gas quadrupled!

 

[Harmonic_Subset]

No, it didn't. Here are historical gas prices in today's dollars. During the Iran-Iraq war there was a significant spike. But it was nowhere near 4-fold. More like an 87 percent price increase. And it went no higher than it has more recently. The fact is, there is no cause for alarm. And even if there were a crisis, there is an engineering solution: simply reduce the weight of motor vehicles so they consume less fuel. It really is that simple.

source: http://zfacts.com/p/35.html

 

[Businesswiz]

There was a thread about this a while back, glad to see it back.

Unless someone here wields power, no one will change the W/P ratio.


I read an article in the WSJ, before the prices went down mainly because of exploration and getting more juice out of what is available now. The problem is that with inflation and equipment costs soaring, this is difficult now. The high price will be able to last a while. I think it was Exxon that reported bad earnings lately for this exact reason.

 

[Harmonic_Subset]

Let's expand the formula to include all the math then.

Work done to move vehicle = Fuel burned

Fuel Energy = (n*KE) + (RF*d) + (AD*d)

where,
n = number of accelerations
KE = kinetic energy
RF = rolling friction
AD = aerodynamic drag
d = distance travelled

The formula has three terms, one each for kinetic energy, rolling friction, and aerodynamic drag. You must accelerate at least once to get up to speed, and introduce n=1 into the first term of the equation. That burns fuel. You must also travel a certain distance over land to get to a destination. Forces that oppose movement such as rolling friction and air resistance rob you of energy along the way, as in the 2nd and 3rd terms of the equation. That burns fuel. Expanding this formula in more detail gives:

Fuel Energy = (n*0.5*m*(V^2)) + (u*m*g*d) + (Cd*0.5*rho*(V^2)*S)

where,
m = mass
V = velocity
u = coefficient of friction
g = gravitational constant
Cd = aerodynamic drag coefficient
rho = atmospheric density
S = planform area of vehicle

The formula still has just three terms, but each term has its own set of factors. As such there are a number of things that can be done to reduce fuel energy consumption based on the individual factors in each term of this equation:

1. Reduce the number of accelerations (n). This benefits the 1st term in the equation.
2. Reduce the mass of the vehicle (m). This benefits both 1st and 2nd terms.
3. Reduce the speed (V). This benefits both 1st and 3rd terms.
4. Reduce the coefficient of friction (u) of the wheels. This benefits the 2nd term.
5. Reduce the distance travelled (d). This benefits both 2nd and 3rd terms.
6. Reduce the gravity (g). Joke. But it would work if you could do it.
7. Reduce the aerodynamic drag coefficient. This benefits only the 3rd term.
8. Reduce the density of air(rho). This benefits the 3rd term.
9. Reduce the planform area of vehicle (S). This benefits the 3rd term.

CRITICISMS:

Notice that "Reduce" is a common theme. Should we do all of these things? Of course! But some are more realistic than others:

1. To go any distance, "n" must be at least equal to one. Regenerative braking might recover some of the kinetic energy, so this technology is worth mentioning.
2. Reducing speed would reduce both kinetic energy and air drag. But people want to get where they are going in a reasonable time, and time is money. It is no surprise that there is enormous opposition to lower speed limits.
3. Reducing the distance people have to travel would be really helpful, and might contribute to lowering speeds. Of course with traffic criss-crossing, and people travelling every-which-way, reducing distance might increase the number of traffic lights, and hence the number of accelerations.
4. Fitting cars with high pressure slick tires would help reduce coefficient of friction, except in winter. And hydroplaning would be a real nuisance.
5. Higher altitude would reduce the density of air, but not much.
6. Better streamlining would promote laminar air flow and reduce the aerodynamic drag coefficient on any vehicle. In fact, alot of cars already have a pretty decent drag coefficient. Although some are a little better than others.
7. Reducing the planform area (upper or frontal surface area) of vehicles would also reduce aerodynamic drag. But smaller surface area means a smaller vehicle. In other words a smaller vehicle will have lower aerodynamic drag.
8. Reducing the mass also means a smaller vehicle. The trade-off of course is reduced safety in collisions with heavier vehicles, and even if you don't get in a collision you will pay higher insurance premiums due to the assessed risk associated with this mode of transportation.

COMMENT

These are illuminating facts as to why a small lightweight vehicle could achieve such extraordinarily low fuel consumption, because compared to a more massive vehicle:

1. It would have proportionally lower kinetic energy.
2. It would have proportionally lower rolling resistance.
3. Its surface area would also be lower and that means proportionally lower air resistance.

Lower mass affects two terms of the fuel consumption equation directly. And if one assumes that the surface area of a car is proportional to its mass, then it may be hypothesized that vehicle mass directly affects ALL THREE terms of the equation, and therefore vehicle mass directly affects fuel consumption, as a general rule.

HYPOTHESIS:

Reducing mass by 50 percent will reduce fuel consumption by 50 percent.

(Return to my original post for example case studies of this hypothesis)

 

[madanthonywayne]

Can we just eliminate the personal car as a method of transportation? I don't think those that concentrate on alternative energy for cars really understand the nature of what is in our future.

The personal car is the basis of American life. It will not be surrendered. Heads would roll before it was surrendered.

That said, this ale car sounds pretty damned cool. I started a similiar thread some time ago about an equally cool electric car.

I think we're about to see some major changes as one or many of these ideas takes off.

All they'd need to do is put this thing into production and sell it at a reasonable price (twenty thousand or less) and it would sell like crazy. I'd buy one.

 

[Harmonic_Subset]

Here is a more comprehensive formula that you can actually plug numbers into and get a reasonably accurate approximation for fuel consumption, for any car. Below the formula are a list of several vehicles, with the calculated versus published fuel consumption. Keep in mind I've still used a number of guestimates for input values, such as the frontal area fill fraction, and the engine efficiency. Most interesting is the Chevy EV1 (no longer in production). There is strong indication from the calculation that the published energy efficiency took into account the centralized stationary powerplant efficiency (e.g. nuclear generating station), and assumed electrical transmission, charging, and dissipation in the electric motors was 100 percent efficient. Very interesting indeed. Anyhow, it seems the Clever Car is a close competitor with the EV1. One has to ask what the trade-offs are between these two vehicles! Amazing what you can learn from doing the numbers. I certainly learned alot.

 

[spidergoat]

The personal car is the basis of American life. It will not be surrendered. Heads would roll before it was surrendered.

That's why we're fucked.

 

[Harmonic_Subset]

Here is a chart showing how frontal surface area varies with vehicle mass. As you can see it conforms quite closely to a linear relationship.

So this seems to bear out my prediction as well that all three of the terms of the equation vary directly with vehicle mass. However actual fuel consumption only very vaguely resembles a linear relationship. Why? Because not all manufacturers attempt to minimize aerodynamic drag coefficient. Different cars have different drag coeffcients, and this results in a very poor pattern of fuel economy, one that people cannot readily predict. So not all cars are created equal. There is still a linear relationship between vehicle mass and fuel economy, but if two cars have different drag coefficients, or other factors, then they will obey a different linear relationship. For example, this is illustrated by a couple linear equations:

y1 = m1 * x + b1
y2 = m2 * x + b2

Both equations are linear, but because they have different constants, they result in different plots. So, when comparing cars that are different in other ways besides mass (and things dependent on mass) it is like plotting many different linear equations on the same graph. They cannot be represented by a single line.

The relationship between fuel economy and vehicle mass is intrinsic, and it is the reason why the Loremo is superior to the EV1, as shown in the table above, as it has a very low mass, and a very, very, small frontal area. Its streamlined body gives it a relationship between mass and fuel economy that is very gradual and economical. If the EV1 didn't weigh 3-times more than the Loremo it might have done far better.

So, the same conclusion is that as a general rule the vehicle mass is the most important thing to reduce if you want to reduce fuel consumption. Although reducing all factors in the formula is desireable. Poor design seems to contribute to worse results. There is no reason why a vehicle has to have a drag coefficient as high as 0.40, since drag coefficient is not related to size. An airship (blimp, zeppelin) has a far better drag coefficient than any motor vehicle, and they are huge in comparison. Here are some typical values for drag coefficient:

2.1 rectangular box
1.8~2.0 eiffel tower
1.3~1.5 empire state building
1.0~1.4 skydiver
1.0~1.3 person standing
0.9 bicycle
0.7~1.1 formula one race car
0.6 bicycle with faring
0.5 sphere
0.7~0.9 tractor-trailer, heavy truck
0.6~0.7 tractor-trailer with faring
0.35~0.45 suv, light truck
0.25~0.35 typical car
0.05 airplane wing, normal operation
0.15 airplane wing, at stall
0.020~0.025 airship, blimp, dirigible, zeppelin


I attribute poor drag coefficient of motor vehicles to styling. Car makers design the shell of a vehicle to appeal to different sorts of buyers, adding grooves and bumps and trim and spoilers here and there, and as a result compromise the laminar airflow over the body. If I were a politician, I would make a law putting an upper limit on drag coefficient for any vehicle sold in this country, even before putting limits on vehicle weight. Because if a stalled wing or a blimp has better drag coefficient than a car, then clearly this is something that could be improved without sacrificing other aspects like passenger capacity, range, speed, etc.

 

[Billy T]

Can we just eliminate the personal car as a method of transportation? I don't think those that concentrate on alternative energy for cars really understand the nature of what is in our future.

Good idea, but not easy, especially in the US in less than at least two decades. US will be a "has been" before that.

This is why, in many other posts I have noted that the coming depression will hit US hardest of all, because for last three decades it has been building "surburban infrastructure" instead of public transport, urban high rise housing, etc. Even the culture is slow to adopt the tel-comuting to work it could.

 

[Harmonic_Subset]

Here is a city bus design that goes a long way toward achieving low weight, low drag coefficient, low frontal area, regenerative braking, high engine efficiency, and the appearance of luxury. It's called a Superbus and every city should have a fleet of these bad boys!

Source: http://www.economist.com/science/tq/displayStory.cfm?story_id=7904103

I live in Toronto, Canada, and in the last couple years the government has paid something like a $billion dollars to purchase a new fleet of buses. They've even experimented with CNG fuel, biodiesel, and hybrid electric buses. But what did they all look like? Like a box! All that effort to maximize fuel efficiency and they designed then to have the highest possible drag coefficient!!! What a #$%! waste. And to top it off, these buses will be in service for 20-30 years. Talk about digging yourself a hole. They don't even use swipe cards yet. Still collecting cash fares and tokens. Stone age. Look at this piece of crap. Putting "Hybrid Electric" on the side of this bus is like committing crime with impunity. Only a thin flashy paint job masks its faults. They should have painted it brown, to give people a more realistic impression. The group that published this photo is aptly named "Bus History", because the inset image at bottom-left of the photo shows where this bus design comes from and how little things have improved.

 

[Billy T]

Here is a city bus design that goes a long way toward achieving low weight, low drag coefficient, low frontal area, regenerative braking, high engine efficiency, and the appearance of luxury. It's called a Superbus and every city should have a fleet of these bad boys!

Might be true for bus travel between distant cities on highways, but as a city bus I would want to see a comparison (to regular bus) of the price and weights normalized (divided) by the number of passenger seats before joining you in support for it.

I have a bias in favor of super-flywheel, reversible-motor/generators busses (Regenerative braking of course follows cheaply and naturally.) for in city use. (Unless there are very steep hills that make the flywheel gymbals limit.) Or even return to the old electric trolley. With flywheel bus,there are no over head wires, only a recharge "lamp post" at a few of the bus stops along the route (perhaps only at both end stations), which restore the losses due to lack of 100% energy recovery, wind losses, etc.. Also it can go on other streets if normal route is blocked by firetrucks, etc. I think they can be cheaper (on life cycle cost basis at least) than even conventional busses and make little pollution in the city. (No pollution anywhere, if electric is from hydro or nuclear source.)

 

[leopold]

The amount of work, and therefore fuel, needed to move a vehicle from A to B is determined primarily by the weight of the vehicle.

no, wrong. the energy required depends mainly on the rolling resistance and the internal friction of the motor used.
the weight of the vehicle figures primarily when starting from a dead stop and stopping distance.

 

[Harmonic_Subset]

no, wrong. the energy required depends mainly on the rolling resistance and the internal friction of the motor used.
the weight of the vehicle figures primarily when starting from a dead stop and stopping distance.

Your absurd response requires no further discussion at this point. My previous posts already showed your objections to be absolutely FALSE. Please study the subject first before pretending to be an expert.

 

[Harmonic_Subset]

Might be true for bus travel between distant cities on highways, but as a city bus I would want to see a comparison (to regular bus) of the price and weights normalized (divided) by the number of passenger seats before joining you in support for it.

I have a bias in favor of super-flywheel, reversible-motor/generators busses (Regenerative braking of course follows cheaply and naturally.) for in city use. (Unless there are very steep hills that make the flywheel gymbals limit.) Or even return to the old electric trolley. With flywheel bus,there are no over head wires, only a recharge "lamp post" at a few of the bus stops along the route (perhaps only at both end stations), which restore the losses due to lack of 100% energy recovery, wind losses, etc.. Also it can go on other streets if normal route is blocked by firetrucks, etc. I think they can be cheaper (on life cycle cost basis at least) than even conventional busses and make little pollution in the city. (No pollution anywhere, if electric is from hydro or nuclear source.)

Express bus routes would be the first routes that Superbuses should be implemented on. It's too bad I don't have ridership statistics or financial data for the Toronto Transit Commission. But I bet they wouldn't be very useful considering all the creative bookkeeping they are likely using to secure government grants, union contracts, and public support. I'd hate to be an accountant wading through that bloody mess.

There's some obvious benefits to having a door for every seat. Currently every passenger boarding a bus has to enter through a single door, pay their fare, and then wiggle through the crowd toward the rear to find a seat or a place to stand and grab a handrail. During rush-hour especially that bottleneck results in slow boarding of buses, delays in the bus getting to the destination. Often I've seen 2, 3, or 4 buses tailgating each other because the bus in front picked up far too many passengers, and the tailgating buses have far too few. Buses stacked up like this during rush hour aggravates traffic congestion and it can take 2 to 3-times longer to get home than it should. It's a self-compounding problem that makes public transit a nightmare and something most people would rather avoid. The insistance on using antiquated bus designs that ignore physical principles that have been known for decades, and stupid fare payment methods is the problem. The technology is available and should be used. For example, for over 10 years most libraries have used re-loadable debit cards for their photocopy machines. It's absurd that we have to use cash or tokens to board a bus.

A Superbus solves all these problems: a door for each seat, and a seat for each passenger. There is no question about how many passengers can squeeze in, because the bus is full when the seats are full. Each passenger swipes his re-loadable debit card, their doors close, and the bus moves on to the next stop.