This answer claims that hoppers cause chunks to be loaded "at least partially."
Using a loop of hoppers, is it possible to keep chunks loaded, specifically for farming, smelting, and mob grinding? What are the limitations to chunk-loading in this way—are only the hoppers loaded? Does the hopper loop need to span multiple chunks, or will a loop in a single chunk work?
Best Answer
Yes
You can
This video explains the phenomenon, and how to build one:
Basically, it works as you have said, a long loop of hoppers will keep a chunk loaded, but the hopper chain must start in the spawn chunks. You can use chains of hoppers to basically extend the area of chunks at spawn that is kept loaded.
In this diagram, the yellow area represents the spawn chunks. As long as the hopper chain starts in the spawn chunks and leads out of it, those chunks will all be kept loaded.