thorpie
1 µW
Hello, I hoping some you guys could offer some advice.
I have been looking at ultra efficient vehicles, 1000 km/litre is a minimum.
I do not want to go fast, I just want assistance, and the only assistance I really require is going uphill. Downhill (any downhill) is already terrific, flat is OK, it is the uphill and only the uphill that really matters.
The methodology I have been examining has been to use steep uphill sections powered by a petrol motor, then turn the motor off for long gradual declines. This is storing power in height, it is efficient. It is also problematic, we often don't have terrain that allows this and even where terrain is conducive to the concept existing roads have not been arranged to allow this. Rearranging our cities to allow it will cost trillions.
However the concept is fine, it is as efficient as using an engine with a constant small dribble of power and it provides relatively massive power when needed for climbing steep hills.
As we currently have few routes that allow the concept to function I need a solution that also provides dribble power. Engines are not conducive to dribble power – 50 watts is just too small to be efficient. Also, if I only dribble, I don't have power to use my methodology when I encounter suitable terrain, I cannot pull out 8* the normal output to go up a steep hill.
I have devised a hybrid system that will function for both methodologies and am seeking reviews and comments.
General Discussion
Personal energy of 80 watts can be provided by the rider – this is the equivalent energy to strolling. Expending this energy is basically effortless, you can go to work in the office without stinking after expending 80 watts for a considerable period of time.
80 watts will drive an 80 kg bloke on a mountain bike on flat terrain at 16 km/h.
A further 50 watts raises the flat speed to 21 km/h. To travel at 20 km/ on a 1% uphill gradient requires an extra 100 watts. This 50 - 100 watts is what I call dribble power.
There are really only two ways to provide dribble power, height or electricity. Using height to get a 1% downhill gradient provides 50 watts of power, you travel at 21 km/h when expending your personal 80 watts.
Engines cannot efficiently provide 50 watts of power – the smallest 4 stroke generally available is the Honda GX22 which loses efficiency if it provides under 625 watts. At 625 watts it is 24% efficient, when providing 460 watts its efficiency reduces to 21%, a 12% reduction.
For an efficient system we want to use the engine at a minimum of 460 watts, and we want to use this power effectively.
460 watts will drive our 80 kg bloke up a 7.6% slope at 20 km/hr. On gradients less than this you go faster than I want to go for efficiency.
Direct drive from small motors will not provide efficiencies of the 94% quoted by drive-train manufacturers. These quoted efficiencies are achieved for optimum larger capacity motors traveling at faster speeds.
A matched generator hooked up to our Honda engine should manage 70% efficiency. This is less efficient than direct drive, however if we are using the engine to provide electrical storage energy it means that we only have one drive mechanism – electricity. The advantage of having only only one drive mechanism is considerable. If we can get 70% efficiency from our engine/generator then electricity is an acceptable drive mechanism for steep hills.
At 70% efficiency our engine/generator provides 320 watts. With 80% hub motor and peripheral efficiency this gives 258 watts at the wheel, which will drive our 80 kg man up a 4% incline at 20 km/h.
To get this efficiency on steep hills we have to bypass any electrical storage system.
The engine can be used to provide power for a storage system to dribble out the dribble power required. This will not provide anything close to the 70% efficiency for hill climbing. But it needs to be as efficient as practicable using our 320 watts of power from the generator.
Putting 320 watts into storage when using dribble power of 50 watts means the engine will be functioning on 15% of the time – if you have 100% storage efficiency.
Batteries won't handle the 320 watts input very effectively, if at all
Maxwells ultra capacitors will handle it, they are comparatively heavy, they provide storage of 4.5 wh/kg. A pack rated at 5 wh will weigh 1.1 kg and will provide 50 watts of dribble power for 6 minutes (2 km) on flat ground.
The storage system adversely affects performance fourfold: how much extra weight I have to lug, including storage and control mechanisms; how much of the 320 watts it wastes going in (including input control mechanism losses, at no losses it will fully charge from the engine in 56 seconds); how much of the power is lost internally (lots); and how much extra power the extra output control mechanisms use. Anyone who could provide reasonable calculations on these aspects would gain my utmost appreciation.
This then gives 4 modes of operation for the bike:
Anyone else coming along for the ride?
Thanks for your time
I have been looking at ultra efficient vehicles, 1000 km/litre is a minimum.
I do not want to go fast, I just want assistance, and the only assistance I really require is going uphill. Downhill (any downhill) is already terrific, flat is OK, it is the uphill and only the uphill that really matters.
The methodology I have been examining has been to use steep uphill sections powered by a petrol motor, then turn the motor off for long gradual declines. This is storing power in height, it is efficient. It is also problematic, we often don't have terrain that allows this and even where terrain is conducive to the concept existing roads have not been arranged to allow this. Rearranging our cities to allow it will cost trillions.
However the concept is fine, it is as efficient as using an engine with a constant small dribble of power and it provides relatively massive power when needed for climbing steep hills.
As we currently have few routes that allow the concept to function I need a solution that also provides dribble power. Engines are not conducive to dribble power – 50 watts is just too small to be efficient. Also, if I only dribble, I don't have power to use my methodology when I encounter suitable terrain, I cannot pull out 8* the normal output to go up a steep hill.
I have devised a hybrid system that will function for both methodologies and am seeking reviews and comments.
General Discussion
Personal energy of 80 watts can be provided by the rider – this is the equivalent energy to strolling. Expending this energy is basically effortless, you can go to work in the office without stinking after expending 80 watts for a considerable period of time.
80 watts will drive an 80 kg bloke on a mountain bike on flat terrain at 16 km/h.
A further 50 watts raises the flat speed to 21 km/h. To travel at 20 km/ on a 1% uphill gradient requires an extra 100 watts. This 50 - 100 watts is what I call dribble power.
There are really only two ways to provide dribble power, height or electricity. Using height to get a 1% downhill gradient provides 50 watts of power, you travel at 21 km/h when expending your personal 80 watts.
Engines cannot efficiently provide 50 watts of power – the smallest 4 stroke generally available is the Honda GX22 which loses efficiency if it provides under 625 watts. At 625 watts it is 24% efficient, when providing 460 watts its efficiency reduces to 21%, a 12% reduction.
For an efficient system we want to use the engine at a minimum of 460 watts, and we want to use this power effectively.
460 watts will drive our 80 kg bloke up a 7.6% slope at 20 km/hr. On gradients less than this you go faster than I want to go for efficiency.
Direct drive from small motors will not provide efficiencies of the 94% quoted by drive-train manufacturers. These quoted efficiencies are achieved for optimum larger capacity motors traveling at faster speeds.
A matched generator hooked up to our Honda engine should manage 70% efficiency. This is less efficient than direct drive, however if we are using the engine to provide electrical storage energy it means that we only have one drive mechanism – electricity. The advantage of having only only one drive mechanism is considerable. If we can get 70% efficiency from our engine/generator then electricity is an acceptable drive mechanism for steep hills.
At 70% efficiency our engine/generator provides 320 watts. With 80% hub motor and peripheral efficiency this gives 258 watts at the wheel, which will drive our 80 kg man up a 4% incline at 20 km/h.
To get this efficiency on steep hills we have to bypass any electrical storage system.
The engine can be used to provide power for a storage system to dribble out the dribble power required. This will not provide anything close to the 70% efficiency for hill climbing. But it needs to be as efficient as practicable using our 320 watts of power from the generator.
Putting 320 watts into storage when using dribble power of 50 watts means the engine will be functioning on 15% of the time – if you have 100% storage efficiency.
Batteries won't handle the 320 watts input very effectively, if at all
Maxwells ultra capacitors will handle it, they are comparatively heavy, they provide storage of 4.5 wh/kg. A pack rated at 5 wh will weigh 1.1 kg and will provide 50 watts of dribble power for 6 minutes (2 km) on flat ground.
The storage system adversely affects performance fourfold: how much extra weight I have to lug, including storage and control mechanisms; how much of the 320 watts it wastes going in (including input control mechanism losses, at no losses it will fully charge from the engine in 56 seconds); how much of the power is lost internally (lots); and how much extra power the extra output control mechanisms use. Anyone who could provide reasonable calculations on these aspects would gain my utmost appreciation.
This then gives 4 modes of operation for the bike:
- no power – downhill @ 0.9% gradient – 22 km/h - heaven
- direct power – using 320 watts – uphill @ 4% gradient – 20 km/h – gateway to heaven
- stored power only – using 50 watts @ dead flat, 100 watts @ 1% uphill – 20 km/h – misery, need to restart engine & recharge @ 2 km (6 minutes) and 1 km (3 minutes) respectively
- stored power while engine is charging
- Honda GX22 engine
- Matched efficient generator to attach to engine, 4,000 rpm
- Hub motor – matched – suitable for power from direct or from storage - volts/specifications??
- Maxwell UltraCapacitor module – 4 wh – 16V – BMOD0110 P016 B01 or equivalent – can we utilize this with the engine/generator/hub motor?
- Mechanism to start engine
- Mechanism to stop engine
- Selector to choose no-assistance/direct/stored/stored and charge
- Contoller for using direct
- Controller for using stored
- Controller for using stored and charging
- Charger to fully charge (in 10 seconds??) ultracapacitor from 120/240 Volts before starting to travel
- Fittings for all components
- wiring
- a bike
- a test track (6 – 8 km) for heavenly mode to see how close to 2,000 km/litre we get. (I suppose we need to check misery mode as well, although I already assume that performance will be abysmal!?)
- organize manufacturing of a fully integrated unit with the engine, generator, storage and contollers built in, and with simple controls and matched hub motor;
- start lobbying to: ensure mongrel councils don't cut off viable heavenly mode routes; that we get assistance opening up identified routes; and getting priority over cars and other inefficient transport
- start identifying heavenly mode routes using existing terrain – ups of 4% or greater gradient rising 10 – 50 metres, long slow downs of 0.5% - 1% downhill gradients with no ups.
- In a few years time some cities will have sufficient heavenly routes for people to remove the dribbling storage from their bikes. This will provide an instant improvement in efficiency of 50% as direct drive (not electricity) is implemented between motor and back wheel
- After heavenly routes become commonplace an off-vehicle power supply will be made available for the steep uphill climb – power will be transferred to the moving bike resulting in the only extra items on the bike being an electric motor and power pickups weighing 2 kg
- This convoluted route, using engine and electricity, then going to only engine, before moving back to only electricity, is the only way to stagger the implementation of this concept. We know that the initial step of using engine and electricity can be hugely improved on heavenly routes by direct drive, but the complexity of running a direct drive system for steep ascents and an electrical system for misery sections makes it much cleaner to use only the engine/electricity option at this time.
Anyone else coming along for the ride?
Thanks for your time
