Unlimited Firestorm Wall
If you have the original unpatched game you can do the following trick to get a fully charged Firestorm Wall to last indefinitely without having to turn it off to recharge. Fully charge your Firestorm Wall and turn it on. Then before it turns off or runs out of power, sell or turn off your power plants until the message 'On Hold' appears in the Firestorm Icon. Your Firestorm Wall will now remain on indefinitely unless you build or turn on your power plants.
Added by: Sanzano May 2nd 2011, ID#16160