MBA fan noise with no apps running ?

Symptoms:

1. Loudly fan but no apps is running
2. Battery showing 0% charged in "Energy Saver" in "System Preferences"

You may try to reset the SMC, here is the instruction for MacBook Air

1. Shutdown your MacBook Air (go to the Apple menu and choose “Shut Down…”).
2. Make sure your MacBook Air has external power. Connect the power adaptor, if it isn’t already.
3. Using the Air’s built-in keyboard (not a plug in keyboard or bluetooth keyboard), of the left hand side of the keyboard press Control-Shift-Option and on the top right of the keyboard, the power key at the same time.
4. Release all the keys at the same time.
5. Press the power key to start the computer.