Here is a furnace array I built on my survival world as part of a project.

The structure is composed of giant hoppers, a giant furnace and a giant chest. Each is functional!

The giant furnace hosts 80 regular furnaces connected in parallel. its main particularity is that it lights on when smelting in the same way a Minecraft furnace would.
The giant hoppers are used to move the items. the one at the top is for the item you want to smelt. The one at the back is for the fuel.
The giant chest is a storage area with 96 double chests. It automatically fills up as the furnaces smelt items.