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Electric Vehicle Thoughts, Questions & Answers
Sethodine
Elio Addict
Didn't forget
I'm just trollin' though. As I've said before, I couldn't really care less about how the electricity is made or how many holes China wants to dig in their desert. I care about the performance and low cost of maintainence.
johnsnownw
Elio Addict
Not to be THAT guy, but:
Major energy sources and percent share of total U.S. electricity generation in 2015:1
- Coal = 33%
- Natural gas = 33%
- Nuclear = 20%
- Hydropower = 6%
- Other renewables = 7%
- Biomass = 1.6%
- Geothermal = 0.4%
- Solar = 0.6%
- Wind = 4.7%
- Petroleum = 1%
- Other gases = <1%
Source
Sethodine
Elio Addict
It's a regional thing. Here in WA, we get about 60% of our power from hydro, with the rest being mostly coal-fired plants (we ship coal from Montana). I like seeing natural gas catching up to coal though
I recall seeing a design where the electric powered vehicle put the "motor" inside the "wheel".... I can see some advantages to it; but also some downsides. Does anyone know if it has been tried yet? and if so, how it went?
johnsnownw
Elio Addict
The Riversimple Rasa has this system, though it's an FCEV.
Sethodine
Elio Addict
There are a few issues with doing it that way, but it's been done. Chiefly, it adds a lot of "unsprung weight" to the wheel, which effects the driving characteristics of the car. Also, it can be difficult to fit a strong enough motor in the hub space of a wheel, while still allowing room for brakes.
There are some pretty good 8kw hub motors out there, but their Max RPMs limit you to about 40mph on most car-sized wheels.
Mostly, I see hub-wheels as being more practical for low speed/energy applications, such as "hybrid kits" for cars. You drive on the electric rear wheels on city streets, then you use the gas-powered front wheel drive for highway. I could see the Elio doing something similar, if you could find a place to put the batteries. To re-charge the batteries, you just set the rear wheel to regenerate and "pull" it along with the FWD. If you want good highway mileage, you turn off the electric motor and let it free wheel. The nice thing about the Elio is that you don't actually need to use a hub motor, because it would be pretty easy to belt-drive it using a more conventional electric motor.
wizard of ahs
Elio Addict
The issues. (Edited: I see Sethodine got the wheel weight issue first, cudos!)
The only advantages, getting the motor out of the body space, and a slight reduction of drives and gears.
In the wheel they tend to be exposed to more dirt and damage. There is one controller per motor.
The 'unsprung weight' becomes an issue (the biggest), so generally all-wheels get powered to help spread that weight around. But in a three wheeler you can't spread that around as much as a four. Six wheel vehicles have off-times been of interest for this reason.
A single e-motor is very slightly more efficient than two smaller ones, and less complex for the controller. Liquid cooled motors are capable of higher efficiency using higher RPM and voltages, yet inherently, exceptionally difficult to apply inside the hub.
A very good system is to use two motors(low cost or the liquid cooled, high RPM ), one for each front wheel, without a transmission, just gearbox's (or direct driven for low cost motors only) and CV shaft's to connect.
It has relatively little space usage in the vehicle body, and an easy upgrade to all wheel drive to suit sports performance. Each motor needs it's own controller, or at least their own RPM limiter. But this is preferable to the unsprung weight issue.
Having said that, if a hi power-density liquid cooled motor were used, having the coolant plumed back into the vehicle radiator, and an internal gear set for high RPM/Voltage, since that motor can be as little as 10% the weight of the direct driven air-cooled, this could be a suitable hub motor system without excessive wheel weight. Dirt and Damage still will be an issue. At the current time, such a motor would be high-tech and expensive.
When I say high voltage we're starting at 500volts and on up. For example, a 10x experimental motor was set to something over 1000volts and above 30k-RPM. The efficiency was very good, I'm guessing maybe 97% compared to 83%. But the motor itself was 1/10 the weight for the power output.
Since the heat created was the same as the comparable and larger motor, it had to have excellent liquid-cooling. In this case tranny fluid was pumped directly inside the stator and splashed back out into the casing, where it was collected, re-cooled and pumped again.
Another example, here is a 91% efficiency motor.. link
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