Energy Stored in an Inductor, calculating inductance

[PeachBanana]

Homework Statement

The electric-power industry is interested in finding a way to store electric energy during times of low demand for use during peak-demand times. One way of achieving this goal is to use large inductors. What inductance L would be needed to store energy 3.0 (kilowatt-hours) in a coil carrying current I= 300 A?

Homework Equations

U = 1/2 LI^2
L = 2E / I^2

3.0 kWh = 1.08*10^7

The Attempt at a Solution

2(1.08 * 10^7) / 900 A^2 = 24,000 H

 

[gneill]

$300^2 \ne 900$