REVA G-Wiz Research
Reva G-Wiz Owner's Manual |
Energy economy analysis |
Development and Launch
The battery is 48v by 200Ah, so that's 9.6kWh.
Electric price in the US is around 10c per kWh.
Electric price in the UK is around 10p per kWh.
So the Reva Gwiz would costs 96c or 96p to charge.
Practically speaking it would go about 40 miles from full to flat.
So this is 96/40miles or 2.4 cents/pence per mile.
Realistically, you wouldn't drive the car to completely flat just like you wouldn't drive until the tank is empty,
so most of the time it would be a partial recharge -like topping up the tank- costing less than 96 cents/pence.
...in the US
Fuel (gasoline) price is about $3 per gallon
On $3 (cost of a gallon of gas) the car would go 125 miles so this is equivalent to 125 mpg.
...in the UK
Fuel (petrol) price in the UK is about £1.15 per litre
1 gallon is 4.55 litres so UK is £5.23 per gallon
In the UK on £5.23 (cost of a gallon of petrol) the car would go 218 miles so this is equivalent to 218 mpg.
So here in the UK I get about 220 mpg out of my Reva Gwiz!
And this is at full speed of 50mph.
Most piston engined cars have a peak efficiency around 30-40 mph, below which you actually waste more fuel driving slowly.
Electric motors have very high efficiency right down to 0mph, so the slower you drive the less charge per mile.
If you are going through towns (slow traffic) the fuel efficiency goes to 1,000mpg equivalent and some.
Now it starts to make sense.
Direct Energy Conversion
Working it out in terms of energy density alone:
Specific Energy (by mass) = 0.17 MJ/kg = 47.2 Wh/kg
Energy Density (by volume) = 0.56 MJ/L = 156 Wh/L = 0.156 Wh/m3
Specific Energy = 44.4 MJ/kg = 12.33 kWh/kg
Energy Density = 32.4 MJ/L = 9.5 kWh/L = 43.19 kWh/gallon(UK)
1 gallon of petrol is 43.19 units(kWh) of electricity.
The G-Wiz goes 40 miles on 9.6 units so 4.17 miles per unit.
Conversion from electricity to petrol is 43.19 units per gallon(UK)
...so this would be 180.09 miles per gallon(UK)
and if the G-Wiz could extract all the energy from petrol (e.g. using fuel cell) it would go 1,800 miles on a 10 gallon tank!
So ... what is your engine doing with all that fuel?
Easy: it's a big heater which produces a bit of motion as a by-product of the heating!