During your run of Lost Planet 3 you'll have the option to buy an upgrade for your rig that detects thermal energy pockets around E.D.N III. This achievement does not require you to empty the T-Posts, just planting them. In total there are 6 T-Posts to plant.
This review may contain some spoilers.
1) The first T-Post is located in Diaz Cavern which you can access through White Canyon Junction and is pretty unmissable. The T-Post will already be planted at this location by Diaz, and you’ll be required to empty it during the Empty a T-Energy Post Mission after helping Laroche.
2) The second post is found in Bailey’s Crossing. If you start or head to the south exit in Bailey’s Crossing you'll notice a small cave you can enter opposite the machinery. Proceed down that path and eventually you'll come to a clearing, at the far end of that clearing you'll find the spot to plant the T-Post.
3) The third post is in Bishop’s Wake and is in the area in which you defend the drill at the beginning of the game. To reach this place however you will need to have unlocked the Winch for your rig. To get to the area simply look inside the cave in Bishop’s Wake as normal until you find a Winch icon (it's on the same side you defended). Use the winch to zipline up, fight a couple of Akrid and the T-Post should be located near the middle.
4) The fourth post can be found in Shackleton’s Peak and you'll need the zipline attachment for this one. This one isn't too difficult to find. In Shackleton's Peak you'll find a pipe which you may or may not have repaired depending on how far you have progressed at this point. Exit your rig and grapple hook to a platform on the right and then zipline across to access a cave. The T-Post is located toward the back of this cave.
5) The fifth T-Post is located in Pickett’s Folly and you will need to have unlocked the magnetic grappling hook for this. You'll want to head towards the Killing Fields and on the left you'll notice a ledge that can only be accessed with the magnetic grappling hook. The T-Post is located toward the back of this cavern and you may have to fight a couple of Akrid before you plant it.
6) The sixth and final T-Post is in The Killing Fields and for this you will need the extended winch upgrade for your rig. If you enter the Killing Fields from Pickett's Folly, head down the lower path and approach the platform on your right. From here you should be able to use your winch to reach an area to the east, when you're across simply have a look around and you'll find your final T-Post.
and my own experience.