From Samus' ship, travel through the door on the far left of the region and proceed through the cave to the far left side. Bomb open the obstructing wall there,
head through the door and run down to the bottom of the sloping
cavern to find this Energy Tank resting there.
You'll need the Speed Booster to reach this one. From Samus' ship, run
over to the door on the far left then run back to activate the Speed
Booster. Crouch when it kicks in, then quickly stand over at the mound on
the left of the ship. Face left, angle up (hold R) and jump, you'll Shinespark
right up the wall and blow open a hidden tunnel in the otherwise blank wall.
Move through the door
behind the wall ahead and proceed through the adjacent corridor. Dismantle the obstructing rocky
overhangs with either bombs or the Screw Attack as you go but watch out for the rising lava. Upon reaching the end simply go through the door to find this Energy Tank straight ahead.
Once you've done away with Kraid, from the elevator leading down to
Norfair, sneak through the right side of the room (using a Super Missile to penetrate the wall) and go through
the door past the massive gruesome statue in the next dark room. Descend the shaft
and you'll find a flashing door that was initially sealed before you faced Kraid.
Go inside, whack the small energy-sucking enemies, then shoot open a roof
section four blocks along from the left wall find this
Energy Tank hidden in the ceiling.
From the main elevator in the green thorny shaft, go to the very
bottom and blow open the floor with a Power Bomb. Descend to the
bottom of the open shaft and head through the door there. Once you reach the
corridor lined with gray bricks you'll spot the Energy Tank sitting on
the left side. Just be careful of the hidden hole right in front of
it - the X-Ray Scope will help you spot it. Leap over the hole to reach the tank.
In the same corridor as missile no. 2, shoot out a hidden section in the
roof to the left of the blue rocky overhang to find this Energy Tank. The Hi-Jump Boots or Space Jump easily allow you to reach it, or you can try propelling Samus up with bombs while in Morphing Ball mode.
In the huge purple shaft with the falling snowflakes in the
background, you should find a yellow door along the right wall. Blow it
open with a Power Bomb and head inside. Whack all the attacking
Sidehoppers, then wall-jump up the wall or use the Grappling Beam
block to reach the top. You'll need the Wave Beam to open the shutter
at the top. Once it's open move through and hop back down to the ground. Head through the door below to find this Energy Tank.
You'll usually need the Gravity Suit to reach this one. In the same small chamber as the Charge Beam, blow open a hidden tunnel in the floor with
a Power Bomb and crawl through. Descend the shaft and go through the
door at the base to find an incredibly long corridor partially filled with water.
Run left and blast any enemies along the floor, then go back to the
right and dash to the left. Once the Speed Booster kicks in you'll
blast through a few walls to find this Energy Tank sealed away in a hidden room beyond.
You don't necessarily need the Gravity Suit to move through the water freely, as it's possible to use the long dry platform further in to charge up the Speed Booster (just barely). Then simply hop into the water and Shinespark left to penetrate the walls (the water won't stop the Varia Suit).
When you enter Norfair for the first time, drop down to the bottom of
the shaft containing the main elevator and head through the door on
the left to find the Energy Tank in plain sight.
Once you've finished Crocomire and found the Grappling Beam, go back
to the long corridor where you fought the red beast and travel to the far
right. You'll notice that the roof above the lava lake is lined with Grappling Hook
blocks, swing across to the far right end to find this Energy Tank there.
Just after you've left the enormous cavern slowly filling with lava in Ridley's
area, go right to find yourself in a darkened shaft where the terrain
ahead is shaped like a dragon's head. Freeze the small dragon head firing blue
flames at you in the wall straight ahead then destroy it with a Power Bomb.
Walk through the wall where the head was to find a hidden shaft
leading below. Go down to find an area filled with spikes and the
floating enemies with glowing balls. Move down to the bottom right
corner of the room to find this Energy Tank atop a platform.
Right after crushing Ridley, go through the door on the left side of
his room to find the shattered capsule that once contained the Metroid
hatchling. Shoot open the wall just below the door to reveal this
Energy Tank tucked in an alcove.
Travel to the shaft on the right area of the ship where the door is leading outside to Crateria (of which leads down to Maridia), then shoot open the
roof at the top to find a hidden passage. Go through the door at the
top to find a large flooded room filled with water. Use the floating platforms
and the Grappling Beam to reach the Energy Tank on the far left of this chamber.
Just after you beat the water serpent Botwoon, go through the door on the
right side of the underwater chamber to enter a long corridor where part of the
floor is filled with sand. Run to the right end of the corridor, along the
way you'll spot this Energy Tank hidden within the purple blocks above.
Go to the far right of the purple blocks in the ceiling and jump up there to find a
narrow way in. Use the X-Ray Scope to reveal the hidden passages, just be
careful as right before the Energy Tank lies a hole sending you down into the
sand.
In the large hidden cave containing the (almost) harmless turtles and missile no. 8, use the adult turtle or the Space Jump to reach the Energy Tank perched
high up on a Grappling Hook block at the top of the region.