# Flywheel Energy Storage

1. Aug 28, 2010

### grey

I have an idea pertaining to energy storage in flywheels, something like they do in the KERS, and need assistance here...

Ok, my idea involves using a flywheel of around 10 kg (steel) with I~1 kg.m^2, to be charged to an RPM of around 7,000 RPM.
This allows E = 0.5 x 1 x (7000x2x pi /60)^2 = 268 KJ of energy to be stored.

I want to charge it with a small engine (something like a Honda GX50) which, according to the charts will give max torque of 3 Nm at 4000 rpm and max power of 1.6 kW at 7000 rpm (approx).

I want to discharge it to run a light vehicle (170 kg including driver) such that the discharge takes place at one wheel only (a three wheeler). I want discharge in pulses.

Now, the questions:
1. How do I calculate the time it takes to charge the flywheel to 7000 RPM? Can I do it without using some intermediate device like a CVT or motor/generator?
2. How do I calculate the discharge time (and characteristics)?

2. Aug 29, 2010

### rathat

I think flywheel energy storage is a really interesting topic, I would love to see more practical uses of them! If you end up making something, please post it.

3. Sep 2, 2010

### drMS

Hi-
1. The time it takes for increase the kinetic energy of the flywheel mainly (but not finally) depends on the characteristics of the energy supplier (your GSX50) and utilizer (in a direct coupling). Write down the energy balance and you will get the dynamics (and then the time). But direct coupling seems to me a not real event..
2. For the discharge time you can use the same approach, this time the flywheel is the motor.

M