icelander
Automotive
- Mar 10, 2007
- 9
This belatedly picks up an interesting thread from earlier in the year, titled "One speed/one load genset for electric vehicles". Please refer to thread 71-207534.
Great stuff, hard facts. Thanks. Brian Peterson rightfully points out the benefit of chamber size in the quest for efficiency. Lopping 5 cyl.s off a Sulzer and installing the remaining one in my daughters Honda would benefit the environment through 50% efficiency fueled by recycled road tar. Impressive lbs/ft at 180 revs. Some weight increase, though.
Let’s slip down the size/efficiency graphs somewhat from full bore oil tanker engines to the generic 2 liter 4-banger, and swap it out of the minivan for 1/6 of a 12 litre I6 truck engine. Same swept volume, hp similar or down a tad, same torque, but revs go down 60%. Impossible for NVH reasons with a normal drivetrain. But when not asked to cover 900-2000 revs to bridge gear gaps and load fluctuations? Staying perennially put at BSFC? Married to a dedicated single-point generator? Harmonics guys could counterweight the sows ear into a silk purse, what?
Seriously though, Brians excellent info actually rather underpins the “single-point” point, I think.
My initial purpose was to find the negative facts to strike the single-point idea off the “interesting enigma” list. Things are getting interesting, as your contributions, not least Ed Danzers, to a large extent lead the opposite way.
Let’s see. Best point BSFC of VW TDI 197 g/kWh. + 15% deviation = kissing 230 g/kWh + engine not always happy + what about the drivetrain + who’s driving and, the part missing from most BSFC maps – what kind of time does that engine actually spend converting that “knocking on 47% thermal efficiency” into useful shove and odometer spin? How much time does the engine spend “off the map”, in the idle or near idle zone where efficiency knocks on 0? A lot of time, in fact. So valuable chemicals die a futile death, spinning and sliding and wearing all the pricey gubbins in a complex engine adding 10% or more to the vehicle weight.
An engine that is started before departure and keeps burning away until after the trips end, will inevitably give us a mean efficiency for the trip of… a few percent? More? Let us measure the actual energy expended during the trip to push air and roll tyres (strain gauge on drive axle?). Let us then measure the BTUs missing from the tank. The discrepancy is chilling. Where did the 47% efficiency go?
Try this test yourself. Drive your modern car at a steady speed, and observe the consumption display. Now drop a gear. Then drop another. Maybe one more. You have now roughly doubled the amount of fuel (mis)used to travel the same distance at the same speed. We’re not talking 15% here, but 50%.
This also drives home that steady travel power needs are in the region of 10% of many consumer cars’ installed maximum output, used for occasional spikes of acceleration. Western consumer perceived car acceleration “needs” of 2008 are now bordering on the silly, this coming from a life-long motorsports man. A Citroën 2CV gives you more fun than a Toyota White Goods 4.0, any day or night. In spite of having a really inefficient engine for these computed times. Fisker is weighing down his Karma with a 250 hp 2.0 turbo solely for generative purposes in a full-EV. Effectively installing two whole propulsion systems with associated weight and cost.
We are, in fact, on to the whole system energy equation here. The baseline is the classic straight IC driveline, straight average driver, average conditions. Can we arrange solid concepts and common components to do better? If so, then how?
Electric vehicles have a few established benefits. Like being well understood, having been around for centuries. Like being eminently scalable (LectraHaul in your garage, sir?). Like being wonderfully efficient with a long enough extension cord (I’ll take mine without batteries, please). Only taking energy to give energy, and when they do, at up to 97% efficiency if some proponents are to be believed.
Note that EVs score twice here. Efficiency when drawing juice, and not drawing any when not propelling. Adding regenerative abilities to the motor drops efficiency but these losses are soon won back in normal use, especially in cities.
There´s more. Packaging, bulk, power-to weight, noise attenuation, parts count, user friendliness …………. (add remarks on dotted line, knowledgeable electric guys), even longevity. Electricity makes a great car, truck, bus, mega-dumper, or ship and always has. A modern E vehicle can beat a modern IC vehicle easily.
If only you can leave out the batteries.
Let’s plug then. Trolleybuses, trains, trams etc whir away all over, in the Alps too, encrusted in smoked ice. The downsides are expensive, conspicuous and maintenance heavy infrastructure, and where that ends, your mobility ends.
Plugging wherever you stop then? Speed charging and widespread charging opportunities would possibly have a much greater impact on E-vehicle acceptance than the elusive Überbattery, as it can be implemented sooner. Zap up an extra 60 miles while your burger fries. Zing a full charge in the K-Mart parking lot. Nice, but not here. Work is being done on this – never forget the ubiquitous 230V nightheater outlets in Sweden – but is still stuck in the future.
For us stuck in the present, onboard chemical-to-electric energy conversion is here. There is a great economic and technological advantage in de facto existence. Could this chemical-energy-to-mileage conversion be made considerably more efficient, not only in the future, but now? Economically?
Brian points out the approx. 15% battery charge/discharge losses and the efficiency of the Prius serial approach reducing the size, though not complexity, of the electrics. Valid, but when tested by Auto Motor und Sport magazine in factual everyday use against a couple of popular family cars of far superior performance and utility (VW and Peugeot diesels), the Prius consumes 20% more fuel. Sobering facts. Where are the diesel hybrids?
The evidence presented in these posts and elsewhere and mathematics rather support the theory that a dedicated present-day-tech single-point engine can further the parallel hybrid to the point of parity with the most efficient straight ICs and then some. Now. In terms of tech and $&€. In the future, it’ll get better, with free-pistons, continuous combustion, external combustion, linear electrics et al, but that, gentlemen, is the future. A boggo piston&crank can do it now.
How?
By shedding all the accumulated complexities of compromise. By single-mindedly optimizing towards simplicity. Minimizing materials, mechanicals, bulk and waste. Leading possibly to a high pressure, high specific output (valveless) DI 2 stroke relying on modern expertise in fluid dynamics and harmonics. Turbocompounding, recuperation and partial adiabatic strategies following.
What it boils down to is this: Offsetting partially decreased transmission efficiency through increased chemical energy conversion efficiency.
Now, as before, the optimal transmission is no transmission. Attaching an IC engine crankshaft straight to a wheel ?100% transmission efficiency. This efficiency is scuppered by the ICE being inefficient except within narrow parameters. So for a century engines have been compromised to fit transmissions and vice versa. A juggling act.
In this post, it is suggested that transmission inefficiency inherent in electrical production, partial storage and use, can be more than offset through as near as possibly absolute chemical-to-electrical conversion efficiency in a low-cost, optimized on/off single-point piston engine.
Losses for single-point optimized electric driveline:
ICE: 50%. Transmission path: 5-15%. Total system efficiency: 40-45%. Not including regeneration.
Losses for conventional ICE+gears driveline:
ICE: 55-100%. Transmission path: 3-8%. Total system efficiency: 0-40%. No regeneration.
Furthermore strengthening our approach as opposed to pure ICE+gears or pure electric with a humongous battery:
1) The battery of our single-point vehicle can take in external energy (be plugged in), saving fuel
2) Kinetic energy can be recovered and reused
3) Waste heat can be used for cabin heating
4) Comparable system weight to straight conventional ICE+gears
5) System cost between current hybrid and conventional drivelines
Yes?
No?
Please challenge!
Great stuff, hard facts. Thanks. Brian Peterson rightfully points out the benefit of chamber size in the quest for efficiency. Lopping 5 cyl.s off a Sulzer and installing the remaining one in my daughters Honda would benefit the environment through 50% efficiency fueled by recycled road tar. Impressive lbs/ft at 180 revs. Some weight increase, though.
Let’s slip down the size/efficiency graphs somewhat from full bore oil tanker engines to the generic 2 liter 4-banger, and swap it out of the minivan for 1/6 of a 12 litre I6 truck engine. Same swept volume, hp similar or down a tad, same torque, but revs go down 60%. Impossible for NVH reasons with a normal drivetrain. But when not asked to cover 900-2000 revs to bridge gear gaps and load fluctuations? Staying perennially put at BSFC? Married to a dedicated single-point generator? Harmonics guys could counterweight the sows ear into a silk purse, what?
Seriously though, Brians excellent info actually rather underpins the “single-point” point, I think.
My initial purpose was to find the negative facts to strike the single-point idea off the “interesting enigma” list. Things are getting interesting, as your contributions, not least Ed Danzers, to a large extent lead the opposite way.
Let’s see. Best point BSFC of VW TDI 197 g/kWh. + 15% deviation = kissing 230 g/kWh + engine not always happy + what about the drivetrain + who’s driving and, the part missing from most BSFC maps – what kind of time does that engine actually spend converting that “knocking on 47% thermal efficiency” into useful shove and odometer spin? How much time does the engine spend “off the map”, in the idle or near idle zone where efficiency knocks on 0? A lot of time, in fact. So valuable chemicals die a futile death, spinning and sliding and wearing all the pricey gubbins in a complex engine adding 10% or more to the vehicle weight.
An engine that is started before departure and keeps burning away until after the trips end, will inevitably give us a mean efficiency for the trip of… a few percent? More? Let us measure the actual energy expended during the trip to push air and roll tyres (strain gauge on drive axle?). Let us then measure the BTUs missing from the tank. The discrepancy is chilling. Where did the 47% efficiency go?
Try this test yourself. Drive your modern car at a steady speed, and observe the consumption display. Now drop a gear. Then drop another. Maybe one more. You have now roughly doubled the amount of fuel (mis)used to travel the same distance at the same speed. We’re not talking 15% here, but 50%.
This also drives home that steady travel power needs are in the region of 10% of many consumer cars’ installed maximum output, used for occasional spikes of acceleration. Western consumer perceived car acceleration “needs” of 2008 are now bordering on the silly, this coming from a life-long motorsports man. A Citroën 2CV gives you more fun than a Toyota White Goods 4.0, any day or night. In spite of having a really inefficient engine for these computed times. Fisker is weighing down his Karma with a 250 hp 2.0 turbo solely for generative purposes in a full-EV. Effectively installing two whole propulsion systems with associated weight and cost.
We are, in fact, on to the whole system energy equation here. The baseline is the classic straight IC driveline, straight average driver, average conditions. Can we arrange solid concepts and common components to do better? If so, then how?
Electric vehicles have a few established benefits. Like being well understood, having been around for centuries. Like being eminently scalable (LectraHaul in your garage, sir?). Like being wonderfully efficient with a long enough extension cord (I’ll take mine without batteries, please). Only taking energy to give energy, and when they do, at up to 97% efficiency if some proponents are to be believed.
Note that EVs score twice here. Efficiency when drawing juice, and not drawing any when not propelling. Adding regenerative abilities to the motor drops efficiency but these losses are soon won back in normal use, especially in cities.
There´s more. Packaging, bulk, power-to weight, noise attenuation, parts count, user friendliness …………. (add remarks on dotted line, knowledgeable electric guys), even longevity. Electricity makes a great car, truck, bus, mega-dumper, or ship and always has. A modern E vehicle can beat a modern IC vehicle easily.
If only you can leave out the batteries.
Let’s plug then. Trolleybuses, trains, trams etc whir away all over, in the Alps too, encrusted in smoked ice. The downsides are expensive, conspicuous and maintenance heavy infrastructure, and where that ends, your mobility ends.
Plugging wherever you stop then? Speed charging and widespread charging opportunities would possibly have a much greater impact on E-vehicle acceptance than the elusive Überbattery, as it can be implemented sooner. Zap up an extra 60 miles while your burger fries. Zing a full charge in the K-Mart parking lot. Nice, but not here. Work is being done on this – never forget the ubiquitous 230V nightheater outlets in Sweden – but is still stuck in the future.
For us stuck in the present, onboard chemical-to-electric energy conversion is here. There is a great economic and technological advantage in de facto existence. Could this chemical-energy-to-mileage conversion be made considerably more efficient, not only in the future, but now? Economically?
Brian points out the approx. 15% battery charge/discharge losses and the efficiency of the Prius serial approach reducing the size, though not complexity, of the electrics. Valid, but when tested by Auto Motor und Sport magazine in factual everyday use against a couple of popular family cars of far superior performance and utility (VW and Peugeot diesels), the Prius consumes 20% more fuel. Sobering facts. Where are the diesel hybrids?
The evidence presented in these posts and elsewhere and mathematics rather support the theory that a dedicated present-day-tech single-point engine can further the parallel hybrid to the point of parity with the most efficient straight ICs and then some. Now. In terms of tech and $&€. In the future, it’ll get better, with free-pistons, continuous combustion, external combustion, linear electrics et al, but that, gentlemen, is the future. A boggo piston&crank can do it now.
How?
By shedding all the accumulated complexities of compromise. By single-mindedly optimizing towards simplicity. Minimizing materials, mechanicals, bulk and waste. Leading possibly to a high pressure, high specific output (valveless) DI 2 stroke relying on modern expertise in fluid dynamics and harmonics. Turbocompounding, recuperation and partial adiabatic strategies following.
What it boils down to is this: Offsetting partially decreased transmission efficiency through increased chemical energy conversion efficiency.
Now, as before, the optimal transmission is no transmission. Attaching an IC engine crankshaft straight to a wheel ?100% transmission efficiency. This efficiency is scuppered by the ICE being inefficient except within narrow parameters. So for a century engines have been compromised to fit transmissions and vice versa. A juggling act.
In this post, it is suggested that transmission inefficiency inherent in electrical production, partial storage and use, can be more than offset through as near as possibly absolute chemical-to-electrical conversion efficiency in a low-cost, optimized on/off single-point piston engine.
Losses for single-point optimized electric driveline:
ICE: 50%. Transmission path: 5-15%. Total system efficiency: 40-45%. Not including regeneration.
Losses for conventional ICE+gears driveline:
ICE: 55-100%. Transmission path: 3-8%. Total system efficiency: 0-40%. No regeneration.
Furthermore strengthening our approach as opposed to pure ICE+gears or pure electric with a humongous battery:
1) The battery of our single-point vehicle can take in external energy (be plugged in), saving fuel
2) Kinetic energy can be recovered and reused
3) Waste heat can be used for cabin heating
4) Comparable system weight to straight conventional ICE+gears
5) System cost between current hybrid and conventional drivelines
Yes?
No?
Please challenge!
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