Having to hold the accelerator pedal exactly in one position to be able to coast is difficult and tricky, and should not have to be learned. Driving long distance like this is not good for efficiency, or for the leg muscles. I do a lot of ecodriving, and coasting is by far the most efficient way to roll -- in an EV, you would use zero energy, and reclaim the potential energy directly.
If you have to use the brakes, then you have accelerated too much. Regenerative brakes should only be used to slow the car in unanticipated situations, and at the last moments to come to a stop.
Not only is ecodriving much more efficient, but it also helps to improve traffic flow. The worst thing for traffic flow is also the least efficient way to drive: accelerate hard and then brake hard. This sets up lots of oscillations in the traffic flow, which causes many drivers to apply their brakes for no apparent reason.
Smooth predictable driving results in smooth and predictable traffic flow, and it is the most efficient way to drive.
Heated brakes are to be avoided, and having hot brakes for normal driving is the clearest indicator that the driver can improve their efficiency.
Coasting uses the weight and momentum of the car in the best way possible. So, it makes sense that making it as easy as possible to coast -- by just lifting your right foot completely off the accelerator to coast will predictably; and by the way, provide a couple of moments to relax the muscles in the driver's leg, too.
All the braking should be engaged by the brake pedal; pure and simple. On an EV, all the regenerative braking should be used to regain as much of the energy as possible -- but this is less efficient than coasting, by definition; so it should not be the way you drive to maximize range on an EV. So, as much braking as possible should come from regeneration, and the engineers need to integrate the hydraulic brakes to provide emergency braking and stop the car at slow speeds; when regen cannot.
Yes, the data is out there -- how do you think a Honda CRX HF gets 118MPG?
http://ecomodder.com/blog/20-yearold-modified-honda-crx-hf-scores-118-mpg-fuel-economy-run/
Coasting is better for several reasons:
When you coast you are getting most of the energy that it took to accelerate back; as you only lose from aero and rolling drag.
With regenerative braking, you lose the aero and rolling drag AND from the losses of the generator/charger/batteries, too.
More importantly, in many situations if you cannot coast easily -- it is too easy to accelerate and then immediately brake. So, you over accelerate and then have to over brake.
Think about it: there are three possible modes of driving, right?
1) Accelerating
2) Coasting
3) Decelerating
Accelerating uses energy, depending on the weight of the car, the steepness of the grade, and the rate of acceleration.
Coasting uses no added energy, and it uses the accumulated momentum / kinetic energy gained by the acceleration. It only loses energy to aerodynamic and rolling drag.
Decelerating loses energy to energy to aerodynamic and rolling drag and either to losses in the regen, and/or converting kinetic energy to heat in the brakes.
To be the most efficient, we need to minimize the energy it takes to accelerate and the energy lost through braking, and we need the car to lose a minimum amount of kinetic energy by being as low aerodynamic and rolling drag as possible.
To cover the most distance with the least energy, we need to accelerate up to a speed that will then allow the car to coast as close to the end as possible, and then use regen to regain some of the remaining kinetic energy. The brakes needs to stay as cool as possible.
Of course, cruising longer distances and/or up hills requires some additional acceleration; either to maintain a constant speed, or to climb a hill / slope. You can do pulse and glide instead of constant acceleration (using the terrain as possible) and climbing hills well requires what I call "swooping". This involves accelerating ahead of the uphill slope (when gaining speed takes less energy) and then use this to help carry speed up the hill. Think how a bicyclist would climb a hill, and you'll understand.
Coasting downhill is a no-brainer, and it certainly is easier to do this when you don't have to constantly fine tune your foot on the accelerator pedal. If you go too fast, then use the regenerative brakes, on the brake pedal! And prepare to "swoop" if there is an uphill.
If coasting is the most efficient way to cover distance, then it should be the easiest mode to achieve; not the hardest. If all the regenerative braking is integrated into the brake pedal, and lifting your right foot off the accelerator lets you free-wheel coast -- then you will quickly learn how to maximize the time spent coasting. You will learn the dynamics of your car, on the routes you routinely drive, and you will maximize your range / efficiency; ICE or EV.
Sincerely, Neil
Wednesday, November 24, 2010
Wednesday, September 29, 2010
CarBEN EV5 Open Source Project Part 3 - Updated 12 Jan 2011
CarBEN EV5 Part 1
CarBEN EV5 Part 2
CarBEN EV5 Part 4
The single entry is probably the most controversial feature of the CarBEN EV -- it has to do with weight savings and surrounding safety structure.
It's not like the the benefits aren't well worth the minor sacrifice: the CarBEN EV could well be the most efficient car yet made, and it could be one of the first electric cars to have a range of 400 miles (or more) on a single charge. If I was able to take part in the X-Prize, the CarBEN EV would have held the most people of any car in the contest. It might have a Cd under 0.14 and weigh less than a ton; hopefully less than a ton with the driver onboard.
I'm serious about these goals, and I have to make choices that save weight, while not diminishing safety, and yes, body gaps add aerodynamic drag. The Bionic increased the Cd from 0.095 (the early blue clay model that I am starting with) up to 0.19. The main reasons for much of this increase is the uncovered wheels and the cooling for the diesel engine.
Since about 97% of all accidents involve impacts on the front and sides of the car, I want to have maximum protection in those areas.
Since a square encloses the most area with the least perimeter (except for a circle, naturally), it is the best shape to make a car with a given frontal area, and it gets the most usable interior volume. The Mercedes Bionic/Boxfish model provides an amazing opportunity: it combines an amazingly low coefficient of drag (Cd) in a shape that is nearly a square in the frontal area. This makes it possible to have comfortable seating for 5 people in a car less than 14 feet long.
A compact car can be much lighter and stronger, and still keep the frontal area down to ~25 sq ft (2.323 sq m). If the Cd of CarBEN EV is 0.14, then the effective frontal area (CdA) is 3.5 sq ft (0.325 sq m). And it is possible to get the Cd as low as 0.11 or so, and that would lower the CdA to 2.75 sq ft (0.255 sq m).
These would be unprecedented drag numbers for any car, let alone one that seats up to 5 people. Having an electric drive train also contributes a lot to this packaging efficiency: the electric motor is much smaller than an equivalent ICE and it's transmission (an electric motor only needs a reduction gear -- or can be direct drive!) and they need just a fraction of the cooling air flow.
And here's one of the reasons where the aero and the aero shape enter into why the entry door is in the back: since truncating the back of the shape (called a Kamm back) makes the vehicle makes it much more practical, and has a very small increase in drag (and the Boxfish model achieves it's staggering Cd of 0.095 with a Kamm back), and this is where a small fraction of the accidents occur anyway, this is where I chose to put the main entry door.
Side doors add weight and reduce the safety; by cutting big holes in the structure (think about a large box beam web) which then has to be reinforced all around the perimeter, and the door itself has to have a similar frame all around the perimeter, and you add the hinges and if you want to have as much strength as possible, you need 2-4 latches (instead of the usual 1). Adding the latches, means that you gain back some/much of the strength you had with no side doors, but it will weight more.
Since I would need a rear hatch door anyway if I put in a side door; I can save a lot of weight and get the safety protection even better than most cars.
Another aspect of the aero that affects many other things, including the seating arrangement: the tapered shape required for ultra low drag means that conventional rows of seats is not the best way to fit everything in. Since the electric motor is so compact, the driver can be moved forward between the front wheels, opening up more room. And the staggered seating means that even more legroom is available by angling your legs off to the side. So, the CarBEN EV fits 5 comfortably, in a package that most cars fit 4 less comfortably. The mesh seats are also a big part of this.
On the asymmetrical seating -- basically, the most the weight would be unbalanced is about 300-350 pounds (the two "extra" seats are for shorter adult/kids), and that weight is on the higher part of the road crown; and away from the much rougher right side edge. I've only ever had to replace wheel bearings and the like on the right side of any of my cars. The battery pack in the floor is 800-900 pounds, and since most cars have the driver on the left -- and most often the driver is the only person in the car; so, most of the time the CarBEN will be in total balance! On the other hand, most cars are usually out of balance by up to 250 pounds (or more).
I think I've shown that the choices I've made so far, are aimed at achieving unprecedented ultra-efficiency, in a compact, very practical people moving machine. Since the most import part of that function is just that: moving people with safety, the small inconveniences of slightly more effort getting in and out of the car are more than offset, if I can get anywhere near the performance I think are possible. Form follows function, and I think the CarBEN EV can function at a very high level, indeed.
As Oliver Kuttner says: you must get the physics right to get to higher efficiency; and all design choices affect the efficiency. Using less energy is my focus, and that is where I cannot compromise.
After I get a prototype and running, I hope to experiment with rigid wheels and solid (non-inflatable) tires and regenerative shock absorbers. The solid tires and rigid wheels could be much lighter weight (which counts double to weight losses anywhere else), and they could have vanishingly low rolling resistance, and they would pass along most of the energy to the regenerative shocks; making their effect greater than it would be with conventional tires.
The ride quality could actually be better than with conventional tires, since light wheels makes the system more compliant (they move rather than moving the car), and the suspension can be fully tuned and damped to match the wheels.
This could help get the energy consumption even lower than 100Wh/mile, and that could extend the range, as well as recharging the batteries (a bit) from the energy regained from the shock absorbers (instead of wasting it as heat). Every little bit counts.
****************
Here's the latest video animation: Final Design Intent Video
Here are the newest images and of the SketchUp model. If you want a copy of the model, I'd be happy to email you a copy!
CarBEN EV5 Part 2
CarBEN EV5 Part 4
The single entry is probably the most controversial feature of the CarBEN EV -- it has to do with weight savings and surrounding safety structure.
It's not like the the benefits aren't well worth the minor sacrifice: the CarBEN EV could well be the most efficient car yet made, and it could be one of the first electric cars to have a range of 400 miles (or more) on a single charge. If I was able to take part in the X-Prize, the CarBEN EV would have held the most people of any car in the contest. It might have a Cd under 0.14 and weigh less than a ton; hopefully less than a ton with the driver onboard.
I'm serious about these goals, and I have to make choices that save weight, while not diminishing safety, and yes, body gaps add aerodynamic drag. The Bionic increased the Cd from 0.095 (the early blue clay model that I am starting with) up to 0.19. The main reasons for much of this increase is the uncovered wheels and the cooling for the diesel engine.
Since about 97% of all accidents involve impacts on the front and sides of the car, I want to have maximum protection in those areas.
Since a square encloses the most area with the least perimeter (except for a circle, naturally), it is the best shape to make a car with a given frontal area, and it gets the most usable interior volume. The Mercedes Bionic/Boxfish model provides an amazing opportunity: it combines an amazingly low coefficient of drag (Cd) in a shape that is nearly a square in the frontal area. This makes it possible to have comfortable seating for 5 people in a car less than 14 feet long.
A compact car can be much lighter and stronger, and still keep the frontal area down to ~25 sq ft (2.323 sq m). If the Cd of CarBEN EV is 0.14, then the effective frontal area (CdA) is 3.5 sq ft (0.325 sq m). And it is possible to get the Cd as low as 0.11 or so, and that would lower the CdA to 2.75 sq ft (0.255 sq m).
These would be unprecedented drag numbers for any car, let alone one that seats up to 5 people. Having an electric drive train also contributes a lot to this packaging efficiency: the electric motor is much smaller than an equivalent ICE and it's transmission (an electric motor only needs a reduction gear -- or can be direct drive!) and they need just a fraction of the cooling air flow.
And here's one of the reasons where the aero and the aero shape enter into why the entry door is in the back: since truncating the back of the shape (called a Kamm back) makes the vehicle makes it much more practical, and has a very small increase in drag (and the Boxfish model achieves it's staggering Cd of 0.095 with a Kamm back), and this is where a small fraction of the accidents occur anyway, this is where I chose to put the main entry door.
Side doors add weight and reduce the safety; by cutting big holes in the structure (think about a large box beam web) which then has to be reinforced all around the perimeter, and the door itself has to have a similar frame all around the perimeter, and you add the hinges and if you want to have as much strength as possible, you need 2-4 latches (instead of the usual 1). Adding the latches, means that you gain back some/much of the strength you had with no side doors, but it will weight more.
Since I would need a rear hatch door anyway if I put in a side door; I can save a lot of weight and get the safety protection even better than most cars.
Another aspect of the aero that affects many other things, including the seating arrangement: the tapered shape required for ultra low drag means that conventional rows of seats is not the best way to fit everything in. Since the electric motor is so compact, the driver can be moved forward between the front wheels, opening up more room. And the staggered seating means that even more legroom is available by angling your legs off to the side. So, the CarBEN EV fits 5 comfortably, in a package that most cars fit 4 less comfortably. The mesh seats are also a big part of this.
On the asymmetrical seating -- basically, the most the weight would be unbalanced is about 300-350 pounds (the two "extra" seats are for shorter adult/kids), and that weight is on the higher part of the road crown; and away from the much rougher right side edge. I've only ever had to replace wheel bearings and the like on the right side of any of my cars. The battery pack in the floor is 800-900 pounds, and since most cars have the driver on the left -- and most often the driver is the only person in the car; so, most of the time the CarBEN will be in total balance! On the other hand, most cars are usually out of balance by up to 250 pounds (or more).
I think I've shown that the choices I've made so far, are aimed at achieving unprecedented ultra-efficiency, in a compact, very practical people moving machine. Since the most import part of that function is just that: moving people with safety, the small inconveniences of slightly more effort getting in and out of the car are more than offset, if I can get anywhere near the performance I think are possible. Form follows function, and I think the CarBEN EV can function at a very high level, indeed.
As Oliver Kuttner says: you must get the physics right to get to higher efficiency; and all design choices affect the efficiency. Using less energy is my focus, and that is where I cannot compromise.
After I get a prototype and running, I hope to experiment with rigid wheels and solid (non-inflatable) tires and regenerative shock absorbers. The solid tires and rigid wheels could be much lighter weight (which counts double to weight losses anywhere else), and they could have vanishingly low rolling resistance, and they would pass along most of the energy to the regenerative shocks; making their effect greater than it would be with conventional tires.
The ride quality could actually be better than with conventional tires, since light wheels makes the system more compliant (they move rather than moving the car), and the suspension can be fully tuned and damped to match the wheels.
This could help get the energy consumption even lower than 100Wh/mile, and that could extend the range, as well as recharging the batteries (a bit) from the energy regained from the shock absorbers (instead of wasting it as heat). Every little bit counts.
****************
Here's the latest video animation: Final Design Intent Video
Here are the newest images and of the SketchUp model. If you want a copy of the model, I'd be happy to email you a copy!
Some pictures of a 1/12th scale (1" = 1') model of the eggcrate frame similar to what could be used to lay the fiberglass shell:
CarBEN EV5 by Neil Blanchard is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.
Sunday, September 5, 2010
Oil Is Finite, Electricity Is Infinite
Oil has a lot of embedded energy to account for:
Exploration is getting harder all the time; and can take years; and lots of energy is consumed doing so.
Drilling is very hard to do, and takes a lot of energy, including making a lot of "drilling mud", which takes a lot of energy to make, and to inject deep down underground. Look it up! The BP drilling rig is nowhere the deepest at ~23,000 feet below the surface of the ocean.
Extraction takes a lot of electricity (with all of it's overhead!) -- possibly more than refining(!); never mind the energy to build and move and operate those gigantic oil rigs.
Transportation to land is expensive, and super tankers burn a lot of fuel, with it's overhead of embedded energy. The routes taken now have to be lengthened to avoid pirates, and pipelines are hard to build and maintain.
Oil then has to be pumped into tanks onshore for storage, and/or into pipelines. Any energy used along the way has it's own overhead of embedded power.
It then has to be transported to refineries; burning more fuel with it's embedded overhead.
Refineries use a lot of electricity (and all it's overhead!) and they use a lot of natural gas to heat the oil, in a process that takes days. There is a lot of blending and other chemicals used, all of which that have to be made ahead of time, using yet more energy and all of it's overhead. The various fuels and by products are then pumped again to storage tanks.
Then the gasoline/diesel is pumped and transported using pipelines, trucks, and trains, burning more fuel and using electricity, added yet more to the overhead.
It then has to be pumped into the storage tanks at the filling stations, and then pumped out again into the cars, using more electricity, adding that overhead of energy.
I almost forgot -- it isn't just the fuel! ICE engines require a lot of lubrication and maintenance: you have to add in all the steps to find, produce, transport, store, refine, store, transport, use, then dispose of the engine oils used in the ICE. So, many of the same steps I listed above have to be repeated for the other consumable carbon based things used by ICE machines, including the lubrication oils and the filters, etc. This accumulates even more carbon footprint.
I HAVE PROBABLY OVER SIMPLIFIED THIS LONG AND ENERGY INTENSIVE PROCESS.
Electricity from coal, on the other hand is fairly easy: mining takes a lot of effort and energy, then moving it around in the storage yards, then transporting it on trains (which are the most efficient way to move anything!), then moving it around storage yards, then burning it, and disposing of the ash waste. This fly ash can be used as aggregate in concrete. Dealing with fly ash is a significant challenge.
Electricity generated from natural gas is more similar to making gasoline/diesel, except for the refining stage. Coal produces the most carbon waste, but has less embedded energy, while natural gas produces far less carbon, but represents a greater amount of embedded energy; just not nearly as much as oil.
Grids losses are not as bad as you might think: the average is a bit less than 8% loss on the grid. Any and all of the overhead for electricity that is used at all the various stages along the way to produce oil -- get added to the oil! So, the 7.5kWh PER GALLON of gasoline could instead just be used directly to move a car 30-60 miles *rather* that making the gasoline.
Electricity can come from renewable sources: solar PV, solar heat, wind power, geothermal (by drilling deep holes!), biomass (methane from plant and animal waste and others), wave power, tidal power, small scale hydro, etc. The more we use of these, the smaller the carbon footprint becomes in the future, as we make the new wind turbines from renewable energy, and so on, and so on.
All of these use energy from our sun, in one form or another -- much more directly that oil an gas. The Sun is our big-fusion-reactor-in-the-sky!
Each gallon of petroleum fuel represents ~100 TONS of biological material, that is millions and millions of years old. We are squandering it -- using so little of it potential. We should use it only when absolutely necessary.
Exploration is getting harder all the time; and can take years; and lots of energy is consumed doing so.
Drilling is very hard to do, and takes a lot of energy, including making a lot of "drilling mud", which takes a lot of energy to make, and to inject deep down underground. Look it up! The BP drilling rig is nowhere the deepest at ~23,000 feet below the surface of the ocean.
Extraction takes a lot of electricity (with all of it's overhead!) -- possibly more than refining(!); never mind the energy to build and move and operate those gigantic oil rigs.
Transportation to land is expensive, and super tankers burn a lot of fuel, with it's overhead of embedded energy. The routes taken now have to be lengthened to avoid pirates, and pipelines are hard to build and maintain.
Oil then has to be pumped into tanks onshore for storage, and/or into pipelines. Any energy used along the way has it's own overhead of embedded power.
It then has to be transported to refineries; burning more fuel with it's embedded overhead.
Refineries use a lot of electricity (and all it's overhead!) and they use a lot of natural gas to heat the oil, in a process that takes days. There is a lot of blending and other chemicals used, all of which that have to be made ahead of time, using yet more energy and all of it's overhead. The various fuels and by products are then pumped again to storage tanks.
Then the gasoline/diesel is pumped and transported using pipelines, trucks, and trains, burning more fuel and using electricity, added yet more to the overhead.
It then has to be pumped into the storage tanks at the filling stations, and then pumped out again into the cars, using more electricity, adding that overhead of energy.
By rights, we should also include the military used to defend and maintain our access to oil, and maintaining stability in oil prices. There are huge hidden subsidies in foreign policy, too. Don't fool yourself to think that much of our battle with terrorism is tied to this whole messy and corrupt situation. Do you know how much oil gets stolen in the Congo or in Iraq?
I almost forgot -- it isn't just the fuel! ICE engines require a lot of lubrication and maintenance: you have to add in all the steps to find, produce, transport, store, refine, store, transport, use, then dispose of the engine oils used in the ICE. So, many of the same steps I listed above have to be repeated for the other consumable carbon based things used by ICE machines, including the lubrication oils and the filters, etc. This accumulates even more carbon footprint.
I HAVE PROBABLY OVER SIMPLIFIED THIS LONG AND ENERGY INTENSIVE PROCESS.
Electricity from coal, on the other hand is fairly easy: mining takes a lot of effort and energy, then moving it around in the storage yards, then transporting it on trains (which are the most efficient way to move anything!), then moving it around storage yards, then burning it, and disposing of the ash waste. This fly ash can be used as aggregate in concrete. Dealing with fly ash is a significant challenge.
Electricity generated from natural gas is more similar to making gasoline/diesel, except for the refining stage. Coal produces the most carbon waste, but has less embedded energy, while natural gas produces far less carbon, but represents a greater amount of embedded energy; just not nearly as much as oil.
Grids losses are not as bad as you might think: the average is a bit less than 8% loss on the grid. Any and all of the overhead for electricity that is used at all the various stages along the way to produce oil -- get added to the oil! So, the 7.5kWh PER GALLON of gasoline could instead just be used directly to move a car 30-60 miles *rather* that making the gasoline.
Electricity can come from renewable sources: solar PV, solar heat, wind power, geothermal (by drilling deep holes!), biomass (methane from plant and animal waste and others), wave power, tidal power, small scale hydro, etc. The more we use of these, the smaller the carbon footprint becomes in the future, as we make the new wind turbines from renewable energy, and so on, and so on.
All of these use energy from our sun, in one form or another -- much more directly that oil an gas. The Sun is our big-fusion-reactor-in-the-sky!
Each gallon of petroleum fuel represents ~100 TONS of biological material, that is millions and millions of years old. We are squandering it -- using so little of it potential. We should use it only when absolutely necessary.
The cost of electricity is very low compared to gasoline -- an EV can be driven the same distance as an ICE powered car for a fraction of the cost. And again, we are not talking price; but rather the amount of embedded energy.
So, in total gasoline/diesel represents a FAR GREATER amount of carbon per mile traveled -- even now before we produce very much electricity from renewable energy.
And that, my friends, is electricity's greatest strength -- it can come from a great variety of energy resources; many of them being renewable.
Petroleum in finite.
Electricity is (for all intents and purposes, until our Sun burns out) infinite. If we used mostly/all renewable energy sources, then we would not even have to conserve...
We *must* think very long term, if we are to survive on this Eaarth we share. We can live without a lot, but we cannot live without the Eaarth.
So, in total gasoline/diesel represents a FAR GREATER amount of carbon per mile traveled -- even now before we produce very much electricity from renewable energy.
And that, my friends, is electricity's greatest strength -- it can come from a great variety of energy resources; many of them being renewable.
Petroleum in finite.
Electricity is (for all intents and purposes, until our Sun burns out) infinite. If we used mostly/all renewable energy sources, then we would not even have to conserve...
We *must* think very long term, if we are to survive on this Eaarth we share. We can live without a lot, but we cannot live without the Eaarth.
Friday, September 3, 2010
Eaarth
Originally posted on 14 Aug 2010:
"Eaarth" by Bill McKibben
"Read it, please. Straight through to the end. Whatever else you were planning to do next, nothing could be more important." —Barbara Kingsolver
I agree.
Please read "Eaarth". Check it out from your local library, or buy it and pass it along to someone.
[From now on, I will be spelling the name of the planet we all share "E-a-a-r-t-h".]
"Eaarth" by Bill McKibben
"Read it, please. Straight through to the end. Whatever else you were planning to do next, nothing could be more important." —Barbara Kingsolver
I agree.
Please read "Eaarth". Check it out from your local library, or buy it and pass it along to someone.
[From now on, I will be spelling the name of the planet we all share "E-a-a-r-t-h".]
More Vehicle Efficiencies!
This post is a continuation/generalization/more organized version of my earlier blog post.
There are a lot of improvements possible for internal combustion engines (aka ICE's). It helps to list the areas that are causing losses, to start:
-- The geometry of the physical layout of the piston, connecting rod and the crankshaft is less than ideal. The connecting rod needs to be ~60 degrees past top dead center to get the best leverage on the crankpin; but the pressure from the fuel ignition occurs much earlier than this; when the connecting rod is essentially trying to bend the crankshaft sideways. The motion of the piston is necessarily sinusoidal.
- The power stroke is only 25% of the full cycle, and there is a lot of mass that has to be accelerated, stopped and accelerated again.
- The valvetrain has to physically resist being moved, and it has to work against the air flows.
- The piston tends to scrape the sides of the cylinder, because it would "rather" twist that stay straight. The rings must exert friction on the cylinder.
- The oil must be pumped through little tiny passageways.
- Electricity must be generated.
- An ICE is a self-powered air pump, in essence. Air flow and the pressures generated, and the cyclical nature of them cause resonances, and backpressures, and the gasses become spring-like.
- Small volumes, like the space above the top ring and the top edge of the piston, trap unburned fuel because the flame cannot reach it.
- Everything flexes and springs -- the crankshaft and the camshaft flex torsionally and longitudinally, the piston vibrates and distorts, as do the cylinders. Valves bounce and stretch and distort into potato chip shapes.
The list goes on... The net result is a typical internal combustion engine that uses ~20% of the energy in the fuel for output motion at best, and requires a transmission to keep the torque of the engine relatively close to the speed of the vehicle.
So, knowing all this, how can we make incremental or wholesale improvements?
+ Offsetting the crankshaft center away from the power downstroke gives the connecting rod some better mechanical leverage -- but is the compression stroke adversely affected?
+ Variable valve timing allows the torque to be available over a broader range of RPM's.
+ Valves can be electrically/hydraulically moved in both directions (opened and closed) to avoid fighting the springs. This also makes it easier to use subtle or more abrupt adjustments to the valve timing.
+ Use cams rather than the crankshaft, to gain a lot more mechanical leverage, and to allow the piston motion to be controlled by the designer; like the Revetec:
This particular design also reduces piston scrape (but it introduces some tendency to spin the piston within the cylinder). It also avoid big changes in crankcase pressures (in configurations with even numbers of pistons). This design effectively doubles the efficiency.
+ Use the Atkinson valve timing, like the Prius does, which has a lot of overlap of the exhaust valve with the beginning of the intake downstroke (I think?) so that there is built in exhaust gas recirculation (aka EGR). This also effectively doubles the efficiency.
Hmmm, how well would a 2-cylinder Revetec with Atkinson cycle and electrically activated valves work?
+ Use a rotary design that reduces the reciprocal motion.
+ Use a 2-stroke design to cut the parasitic losses in half.
++ Use a continuous burn design to further reduce the cyclical nature of the engine; or at least reduce the time between power cycles.
+ Figure out how to reduce waste heat from being produced, and then try to use the remaining excess heat to produce output.
What are other ideas to improve ICE's?
There are a lot of improvements possible for internal combustion engines (aka ICE's). It helps to list the areas that are causing losses, to start:
-- The geometry of the physical layout of the piston, connecting rod and the crankshaft is less than ideal. The connecting rod needs to be ~60 degrees past top dead center to get the best leverage on the crankpin; but the pressure from the fuel ignition occurs much earlier than this; when the connecting rod is essentially trying to bend the crankshaft sideways. The motion of the piston is necessarily sinusoidal.
- The power stroke is only 25% of the full cycle, and there is a lot of mass that has to be accelerated, stopped and accelerated again.
- The valvetrain has to physically resist being moved, and it has to work against the air flows.
- The piston tends to scrape the sides of the cylinder, because it would "rather" twist that stay straight. The rings must exert friction on the cylinder.
- The oil must be pumped through little tiny passageways.
- Electricity must be generated.
- An ICE is a self-powered air pump, in essence. Air flow and the pressures generated, and the cyclical nature of them cause resonances, and backpressures, and the gasses become spring-like.
- Small volumes, like the space above the top ring and the top edge of the piston, trap unburned fuel because the flame cannot reach it.
- Everything flexes and springs -- the crankshaft and the camshaft flex torsionally and longitudinally, the piston vibrates and distorts, as do the cylinders. Valves bounce and stretch and distort into potato chip shapes.
The list goes on... The net result is a typical internal combustion engine that uses ~20% of the energy in the fuel for output motion at best, and requires a transmission to keep the torque of the engine relatively close to the speed of the vehicle.
So, knowing all this, how can we make incremental or wholesale improvements?
+ Offsetting the crankshaft center away from the power downstroke gives the connecting rod some better mechanical leverage -- but is the compression stroke adversely affected?
+ Variable valve timing allows the torque to be available over a broader range of RPM's.
+ Valves can be electrically/hydraulically moved in both directions (opened and closed) to avoid fighting the springs. This also makes it easier to use subtle or more abrupt adjustments to the valve timing.
+ Use cams rather than the crankshaft, to gain a lot more mechanical leverage, and to allow the piston motion to be controlled by the designer; like the Revetec:
+ Use the Atkinson valve timing, like the Prius does, which has a lot of overlap of the exhaust valve with the beginning of the intake downstroke (I think?) so that there is built in exhaust gas recirculation (aka EGR). This also effectively doubles the efficiency.
Hmmm, how well would a 2-cylinder Revetec with Atkinson cycle and electrically activated valves work?
+ Use a rotary design that reduces the reciprocal motion.
+ Use a 2-stroke design to cut the parasitic losses in half.
++ Use a continuous burn design to further reduce the cyclical nature of the engine; or at least reduce the time between power cycles.
+ Figure out how to reduce waste heat from being produced, and then try to use the remaining excess heat to produce output.
What are other ideas to improve ICE's?
X-Prize Knockout Round - Con't.
Originally posted 1 July 2010:
I think that the X-Prize competition is fulfilling the objective of focusing on vehicle efficiency. Starting with the results so far, I am hoping to contribute to the discussion and to the process.
Here's the link to the PDF that shows the results of the X-Prize Knockout Round:
Progressive Automotive X-Prize Knockout Round Results
The measured MPGe of the teams in this round -- remember this is the Combined number from the City, Urban, and Highway tests:
American HyPower 54.5 Hybrid
Spira 84.8 ICE (E10)
FVT eVaro 152.5 Hybrid (serial)
Zap 111.0 EV
Tata 134.3 EV
Electric Raceabout 128.1 EV
AMP'd Sky 86.7 EV
West Philly (MS) 63.5 Hybrid
West Philly (Alt) 53.7 Hybrid
Global-E 50.4 Hybrid
Li-ion 182.3 EV
Aptera 140.1 EV
TW4XP 107.0 EV
WWU 92.5 Hybrid
Tango 86.8 EV
BITW 51.1 ICE (diesel)
X-Tracer (#72) 180.0 EV
X-Tracer (#79) 188.8 EV
Illuminati 119.8 EV
Enginer 53.0 Hybrid (electric/ICE w/ steam heat recovery)
Edison2 (#95 Alt) 97.0 ICE (E85)
Edison2 (#97 MS) 101.4 ICE (E85)
Edison2 (#98 MS) 80.3 ICE (E85)
I think these results speak for themselves! The electric cars are in general, giving much better efficiency, and several of those (the X-Tracer, FVT, Tata, and the Aptera) also have excellent acceleration. The Li-ion, Illuminati, TW4XP, and Edison2 (among others) were not as quick -- the Li-ion and Edison2 cars are through to the finals, though. I am sad that neither the FVT eVaro nor the Illuminati Seven made it through, due to (relatively) minor technical reasons. They failed at the moment (which is how racing/competitions work, to be sure), but I think their problems are solvable, and the strong merits of their vehicles are obvious.
The Aptera is through, but still a bit disappointing -- it's aero is equal or better to anybody (save the X-Tracer), but their efficiency seems to have suffered. It barely betters the Tata, which is "just" a well executed EV conversion of a decent but ordinary hatchback. The Global-E had an ignition mapping error that made their number lower.
So the lowest MPGe of an electric drive; the AMP'd Sky was 86.7MPGe (Tango was 86.8), while the best of a car with an internal combustion is the Edison2 #97 at 101.4. (Actually, the FVT has a ICE powered generator onboard, but did not need it *at all* in the X-Prize. It would be great to see how the eVaro does for MPGe in charging mode!) The hybrids all were all below the 67MPGe -- except the WWU at 92.5 (and the FVT).
The average of the 12 vehicles using electric drive MPGe (I'm including the FVT in this) was 134.7MPGe
The average of the 6 hybrids (not including the FVT) was 61.26MPGe (Please note, these are all parallel hybrids?)
The average of the 5 internal combustion drive cars was 82.92MPGe
The X-Prize results table does not include weights, but I daresay that the average weight of the internal combustion cars was lowest (the Edison2 and Spira are all much lighter!).
The best aero drag is on the X-Tracer, followed by a very close group including the Aptera, Edison2, Li-ion.
As many have said, the X-Prize is setting a very high standard (which is both good and bad). They are essentially looking for the complete package, and virtually no glitches. Even the well financed/professional teams had several glitches. I would have set up the X-Prize a bit differently; to measure (and therefore emphasize and encourage) the four main things that need to be improved to get the maximum efficiency.
Those four critical things are; from most important to least important (as I am interpreting the Knockout results):
* Drivetrain Efficiency
* Aerodynamic Drag
* Weight
* Rolling Efficiency
I would have scored these in relative terms, which pits each vehicle against the others (rather than setting standards that are somewhat arbitrary). On drivetrain efficiency, I would either use a dynamometer or the best result of the three economy tests: the City, Urban, or Highway. (This will indicate what vehicle is good for a particular role, and measures the drivetrain at it's best.)
For Drivetrain Efficiency, the points awarded would be the best MPGe x Number of Seats. So, using the Overall MPGe for 23 vehicles that competed in the Knockout Round listed above (we do not have the separate measured results from the City, Urban, and Highway test): the X-Tracer #79 would be 188.8 x 2 = 377.6 points, and so on. The best mainstream MPGe was the Illuminati Seven: 119.8 x 4 = 479.2 points.
Aerodynamic Drag would use the Weight and the Rolling Efficiency, and the results of a Coastdown test to determine the Cd of each car. I would take the inverse of the number of entrants divided by the Cd, then multiplied by the Number of Seats: So the Aptera and the Li-ion and the Edison2 alternate cars may be at the top: 23 (22, 21) / 0.15 x 2 = ~306.6 and ~293.3 and ~280 points respectively. The Edison2 mainstream cars would get 20 and 19 (or higher depending on their Cd) resulting in 20 (19) / 0.15 x 4 = 533.3 and 506.6 points respectively.
For Weight, I would take the lightest one and score it by inverting the number of Entrants x the Number of Seats – the Spira would get 23 x 2 (seats) giving it 46 points. The Edison2 alternate car would be next with 22 x 2 = 44 points. The two Edison2 mainstream cars would be 21 x 4 = 84 points and 20 x 4 = 80 points respectively; and so on. This give priority to the cars that seat more people, and it is realistic in terms of what is achievable in the real world.
Rolling Efficiency includes tires and alignment and would be prorated for weight – a slower coastdown test using a ramp would be needed. I think an inverted number of the entrants would be a fair way to award points.
Obviously, all four of the critical factors are interrelated, and they all would be reflected in the Overall MPGe number – but testing for them and awarding points (in some manner) for them separately, helps focus the designs on the most important aspects – and more importantly helps demonstrate their performance; whether or not the designs get ALL of them right and in the right balance, and if there is something that lags (or breaks) and the vehicle is DQ'd, people will still be able to judge the merits of the design.
We could quibble about how each of these was scored – I am just throwing this out there. At this moment in time, I feel that the emphasis on the safety, and meeting the letter of the rules, etc. are distracting the designers from the main point; of maximizing the efficiency. Obviously, for a finished, production, reasonably priced, appealing vehicle – ALL of these things are also critically important. These would be determined by finished vehicle, and the buying public. But, I feel that an emphasis on the overall efficiency, and the four most important factors that directly contribute to maximum efficiency, would have better served the purposes of the X-Prize.
One of the most important things I learned while I was at the X-Prize Knockout competition was: do not dismiss or ignore anybody! There is a LOT more than meets the eye with all of the entrants, and no matter the results, all the designs have strengths – and weaknesses that are all very informative.
I also was floored by the height of passion by so many people; on all the teams. Emanuele Pirro -- 5-time Le Mans winner, was there driving for the Edison2 team -- because he wanted to do his part. The sight of Oliver Kuttner with tears streaming down his face; returning from the starting line of the City Test with the first of his cars about to actually get to the heart of the matter; moves me to tears, as well. And I'm quite sure that every person involved in the X-Prize, who has put in a similar Herculean effort, feels the same.
Here's the link to the PDF that shows the results of the X-Prize Knockout Round:
Progressive Automotive X-Prize Knockout Round Results
The measured MPGe of the teams in this round -- remember this is the Combined number from the City, Urban, and Highway tests:
American HyPower 54.5 Hybrid
Spira 84.8 ICE (E10)
FVT eVaro 152.5 Hybrid (serial)
Zap 111.0 EV
Tata 134.3 EV
Electric Raceabout 128.1 EV
AMP'd Sky 86.7 EV
West Philly (MS) 63.5 Hybrid
West Philly (Alt) 53.7 Hybrid
Global-E 50.4 Hybrid
Li-ion 182.3 EV
Aptera 140.1 EV
TW4XP 107.0 EV
WWU 92.5 Hybrid
Tango 86.8 EV
BITW 51.1 ICE (diesel)
X-Tracer (#72) 180.0 EV
X-Tracer (#79) 188.8 EV
Illuminati 119.8 EV
Enginer 53.0 Hybrid (electric/ICE w/ steam heat recovery)
Edison2 (#95 Alt) 97.0 ICE (E85)
Edison2 (#97 MS) 101.4 ICE (E85)
Edison2 (#98 MS) 80.3 ICE (E85)
I think these results speak for themselves! The electric cars are in general, giving much better efficiency, and several of those (the X-Tracer, FVT, Tata, and the Aptera) also have excellent acceleration. The Li-ion, Illuminati, TW4XP, and Edison2 (among others) were not as quick -- the Li-ion and Edison2 cars are through to the finals, though. I am sad that neither the FVT eVaro nor the Illuminati Seven made it through, due to (relatively) minor technical reasons. They failed at the moment (which is how racing/competitions work, to be sure), but I think their problems are solvable, and the strong merits of their vehicles are obvious.
The Aptera is through, but still a bit disappointing -- it's aero is equal or better to anybody (save the X-Tracer), but their efficiency seems to have suffered. It barely betters the Tata, which is "just" a well executed EV conversion of a decent but ordinary hatchback. The Global-E had an ignition mapping error that made their number lower.
So the lowest MPGe of an electric drive; the AMP'd Sky was 86.7MPGe (Tango was 86.8), while the best of a car with an internal combustion is the Edison2 #97 at 101.4. (Actually, the FVT has a ICE powered generator onboard, but did not need it *at all* in the X-Prize. It would be great to see how the eVaro does for MPGe in charging mode!) The hybrids all were all below the 67MPGe -- except the WWU at 92.5 (and the FVT).
The average of the 12 vehicles using electric drive MPGe (I'm including the FVT in this) was 134.7MPGe
The average of the 6 hybrids (not including the FVT) was 61.26MPGe (Please note, these are all parallel hybrids?)
The average of the 5 internal combustion drive cars was 82.92MPGe
The X-Prize results table does not include weights, but I daresay that the average weight of the internal combustion cars was lowest (the Edison2 and Spira are all much lighter!).
The best aero drag is on the X-Tracer, followed by a very close group including the Aptera, Edison2, Li-ion.
As many have said, the X-Prize is setting a very high standard (which is both good and bad). They are essentially looking for the complete package, and virtually no glitches. Even the well financed/professional teams had several glitches. I would have set up the X-Prize a bit differently; to measure (and therefore emphasize and encourage) the four main things that need to be improved to get the maximum efficiency.
Those four critical things are; from most important to least important (as I am interpreting the Knockout results):
* Drivetrain Efficiency
* Aerodynamic Drag
* Weight
* Rolling Efficiency
I would have scored these in relative terms, which pits each vehicle against the others (rather than setting standards that are somewhat arbitrary). On drivetrain efficiency, I would either use a dynamometer or the best result of the three economy tests: the City, Urban, or Highway. (This will indicate what vehicle is good for a particular role, and measures the drivetrain at it's best.)
For Drivetrain Efficiency, the points awarded would be the best MPGe x Number of Seats. So, using the Overall MPGe for 23 vehicles that competed in the Knockout Round listed above (we do not have the separate measured results from the City, Urban, and Highway test): the X-Tracer #79 would be 188.8 x 2 = 377.6 points, and so on. The best mainstream MPGe was the Illuminati Seven: 119.8 x 4 = 479.2 points.
Aerodynamic Drag would use the Weight and the Rolling Efficiency, and the results of a Coastdown test to determine the Cd of each car. I would take the inverse of the number of entrants divided by the Cd, then multiplied by the Number of Seats: So the Aptera and the Li-ion and the Edison2 alternate cars may be at the top: 23 (22, 21) / 0.15 x 2 = ~306.6 and ~293.3 and ~280 points respectively. The Edison2 mainstream cars would get 20 and 19 (or higher depending on their Cd) resulting in 20 (19) / 0.15 x 4 = 533.3 and 506.6 points respectively.
For Weight, I would take the lightest one and score it by inverting the number of Entrants x the Number of Seats – the Spira would get 23 x 2 (seats) giving it 46 points. The Edison2 alternate car would be next with 22 x 2 = 44 points. The two Edison2 mainstream cars would be 21 x 4 = 84 points and 20 x 4 = 80 points respectively; and so on. This give priority to the cars that seat more people, and it is realistic in terms of what is achievable in the real world.
Rolling Efficiency includes tires and alignment and would be prorated for weight – a slower coastdown test using a ramp would be needed. I think an inverted number of the entrants would be a fair way to award points.
Obviously, all four of the critical factors are interrelated, and they all would be reflected in the Overall MPGe number – but testing for them and awarding points (in some manner) for them separately, helps focus the designs on the most important aspects – and more importantly helps demonstrate their performance; whether or not the designs get ALL of them right and in the right balance, and if there is something that lags (or breaks) and the vehicle is DQ'd, people will still be able to judge the merits of the design.
We could quibble about how each of these was scored – I am just throwing this out there. At this moment in time, I feel that the emphasis on the safety, and meeting the letter of the rules, etc. are distracting the designers from the main point; of maximizing the efficiency. Obviously, for a finished, production, reasonably priced, appealing vehicle – ALL of these things are also critically important. These would be determined by finished vehicle, and the buying public. But, I feel that an emphasis on the overall efficiency, and the four most important factors that directly contribute to maximum efficiency, would have better served the purposes of the X-Prize.
One of the most important things I learned while I was at the X-Prize Knockout competition was: do not dismiss or ignore anybody! There is a LOT more than meets the eye with all of the entrants, and no matter the results, all the designs have strengths – and weaknesses that are all very informative.
I also was floored by the height of passion by so many people; on all the teams. Emanuele Pirro -- 5-time Le Mans winner, was there driving for the Edison2 team -- because he wanted to do his part. The sight of Oliver Kuttner with tears streaming down his face; returning from the starting line of the City Test with the first of his cars about to actually get to the heart of the matter; moves me to tears, as well. And I'm quite sure that every person involved in the X-Prize, who has put in a similar Herculean effort, feels the same.
Progressive Automotive X-Prize Knockout Round!
Originally posted on 22 June 2010:
I am at the Michigan Speedway, as a volunteer member of the Edison2 team -- Oliver Kuttner made this generous offer and I was all too happy to accept. I have a fair number of pictures, which I am starting to upload. I arrived Sunday (which I calling Day 1, even though it was just setting up; and I'll be here through Friday! :-)
We have been very busy so far, prep and cleaning up loose ends -- two of the four Edison2 cars go in for technical inspection Monday the 21st, and two go in Tuesday the 22nd. The first Edison2 Very Light Car tandem (#95 which was the one without wheel pods at the Shakedown) passed this morning and the first of the two mainstream cars was in the process. The weight of the #95 car was 702 pounds. I not sure how this is figured, but it will be required to carry 99 pounds of ballast weight.
I saw the Aptera for my first time in person, it looks very good "in real life". And I got to sit in the driver's seat -- there is almost too much leg room, and I fit well, though there is not a lot of "extra" head room. (I'm 6'-4"). For that matter -- obviously, this is the first time I have seen any of the vehicles: the Illuminati Seven, the FVT eVaro, the Twike, the X-Tracers, etc., etc. Pretty cool stuff all of it!
The cars that had not completed all the tests in the Shakedown were here earlier last week and they are taking runs on the (very large, high banked) oval track. Other events will happen on the road track.
Tomorrow (Tuesday the 22nd) will be more tech inspections, and the "biggie" economy runs that are the raison d'être are on Wednesday and Thursday! And actually there will also be economy runs on Friday, which is the Public Day, but that schedule has not been fully settled yet.
I am at the Michigan Speedway, as a volunteer member of the Edison2 team -- Oliver Kuttner made this generous offer and I was all too happy to accept. I have a fair number of pictures, which I am starting to upload. I arrived Sunday (which I calling Day 1, even though it was just setting up; and I'll be here through Friday! :-)
We have been very busy so far, prep and cleaning up loose ends -- two of the four Edison2 cars go in for technical inspection Monday the 21st, and two go in Tuesday the 22nd. The first Edison2 Very Light Car tandem (#95 which was the one without wheel pods at the Shakedown) passed this morning and the first of the two mainstream cars was in the process. The weight of the #95 car was 702 pounds. I not sure how this is figured, but it will be required to carry 99 pounds of ballast weight.
I saw the Aptera for my first time in person, it looks very good "in real life". And I got to sit in the driver's seat -- there is almost too much leg room, and I fit well, though there is not a lot of "extra" head room. (I'm 6'-4"). For that matter -- obviously, this is the first time I have seen any of the vehicles: the Illuminati Seven, the FVT eVaro, the Twike, the X-Tracers, etc., etc. Pretty cool stuff all of it!
The cars that had not completed all the tests in the Shakedown were here earlier last week and they are taking runs on the (very large, high banked) oval track. Other events will happen on the road track.
Tomorrow (Tuesday the 22nd) will be more tech inspections, and the "biggie" economy runs that are the raison d'être are on Wednesday and Thursday! And actually there will also be economy runs on Friday, which is the Public Day, but that schedule has not been fully settled yet.
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