What were the cylindrical structures Rey was salvaging from in the Star Destroyer?

Question

In the beginning of The Force Awakens, Rey is shown to be salvaging components from large cylindrical structures in what appears to be a crashed Star Destroyer's hangar.

Is there any information (cue the TFA Visual Dictionary, Incredible Cross-Sections, etc.) on the function of those structures?

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NOTE: This is a different question from "What were the objects Rey was salvaging in the Star Destroyer hangar?", which deals with the objects Rey was salvaging, not the structures she was salvaging from.

Answer 1

Well, from the answer to the other question, we do know that what was INSIDE the cylindrical objects are Capacitor Bearings. This implies that the object Rey is salvaging from are quite possibly Capacitor Banks. In this Wookieepedia link:

A capacitor bank was an energy storage unit. Rows of capacitor banks were used in the inner mechanisms of turbolasers. The energy stored in the capacitor banks was converted into charged laser beams via the weapon's laser actuators. The storage capability of the capacitor banks allowed the turbolaser to fire rapidly.

So it would appear that Rey was inside one of the many Turbolaser Batteries found on Imperial Star Destroyers, taking Capacitor Bearings out of the Capacitor Banks that power those Turbolasers.

Answer 2

The Star Wars: Force Awakens official Novelisation, Star Wars: Force Awakens junior novelisation and original script all identify this mystery structure as a wall.

One such individual clung insectlike to a dark metal wall pimpled with protruding sensors, manipulators, and other decaying mechanisms. Clad in light protective goggles with green lenses, face mask, gloves, and gray desert clothing, the busy figure was burdened with a substantial backpack. A multifunction staff strapped to her back made precision work in such tight and dangerous quarters difficult. Wielding an assortment of tools, the scavenger was excising an assortment of small devices from one metal wall. One after another, bits of booty found their way into the satchel that hung below the slender figure.

_{^{Star Wars: Force Awakens - Official Novelisation}}

and

She hung on to the wall of a demolished destroyer and used her tools to wiggle free various components that rust hadn’t devoured. The ship was a treasure trove of metal sheeting and military-grade tech that, if given a proper cleaning, could fetch Rey a meal or two at Niima Outpost.

_{^{Star Wars: Force Awakens - Junior Novelisation}}

and

A metal sheet is pulled open to reveal the wrapped up face of A SCAVENGER, perhaps alien, in GOGGLES, FACE MASK and GLOVES. Backpack with a STAFF strapped to it. Uses TOOLS to remove various MECHANISMS from inside the wall. We are in an upside-down, canted CORRIDOR. The Scavenger finds a valuable piece, drops it in a SATCHEL. Swings the bag back and begins CLIMBING DOWN on a cable, between treacherous WALLS OF MACHINERY, headed to:

_{^{Star Wars: Force Awakens - Script}}