Make Mac boot upon plugging in power

There are no build-in power modes in Mac OS X. Still, the standard configuration in Mac OS X in combination with the high capacity batteries used in the MacBooks offers quite good battery life.

If you want to optimize your energy usage, you need to manually tweak settings.

Here's, what OS X offers to save power:

System Settings -> Energy Saver

• dim display when using battery
• display/computer sleep

System Settings -> Display

• Automatically adjust brightness

System Settings -> Security & Privacy

• disable remote control infrared receiver

Menubar

• Wifi Icon -> disable Wifi
• Bluetooth icon -> disable Bluetooth

The power adapter is required for closed display mode on any Apple portable machine, without it you can't use closed display mode.

Reference: http://support.apple.com/kb/ht3131

There is however a third party solution, called Caffine. Which when enabled, forces the mac to stay on until the battery dies, it won't ever sleep.

http://lightheadsw.com/caffeine/