I want to buy an external hard drive enclosure for may laptop and was curious about the power required to use it. I want to be able to use it anywhere. I want speed when I need it through ESATA and a power source and still be able to use it anywhere with a usb port and without other power cable required. Is there an enclosure I can use to do this?
It depends on what type of drive you are using. If you're using a 2.5" drive (laptop harddrive), you can get an enclosure that is powered solely by USB power. Most of the newer drives don't need as much power, but some of the older ones can be a little power hungry.
If you do need more power, you can get a USB "Y" cable - they have 2 USB plugs - a black one (your normal power+data) and a second, sometimes red plug (just for extra power). You can usually get these for a few bucks, depending on where you get them from.
As for enclosures, I always recommend taking a look at NewEgg's selection.
If you want an external enclosure for a power-hungry drive, it will have to get the power from somewhere, but you don't seem to want a plug pack adapter for the enclosure.
Modern drives tend to require more power than the USB port can supply.
You may have to compromise. A 2.5-inch hard drive (intended for a laptop) is more likely to require less power.
I regularly use a 120GB 2.5-inch LaCie drive in an enclosure which is quite happy with the USB cable alone. No external power supply.