On the right side of the platform with the first Energy Tank, Samus should shoot a missile up. Then she should destroy the next block with her beam. If she jumps up to the destroyed blocks, and heads right, she will find an Energy Tank.
In the room below the Sub-Zero Containment is a hidden tunnel made of Power Bomb Blocks to the left. Near the end of a tunnel is a hidden shaft that can be bombed open. The Tank is in a block at the top of the shaft.
Reactivate Reactor Silo (Can be obtained early after reactivating the main elevator)
Once Nettori is defeated, powering the doors, Samus can use a Power Bomb to destroy a large Geron and access the room with this Tank. Samus will acquire it by jumping up into a hidden tunnel in the wall and navigating it with her Morph Ball.
Alternatively, the tank can be obtained early as soon as Samus can return to the Main Deck. This is done through a series of Shinesparks, with the final shinespark destroying the Geron. However, obtaining the Power Bomb Tank early doesn't allow Samus to use Power Bombs. The tank will only take effect after Power Bombs are collected normally.
In the Restricted Zone, this Tank can be accessed following the Restricted Laboratory's destruction and once Samus is able to return to the area. It is achieved by keeping a Shinespark charged up, and then blasting into the middle of a shaft suspended in space.