This contraption is known as an Oji slow drip cold brew coffee system.
You fill the top with ice, and a bit of water.
You fill the center with coarsely ground coffee, and a glass filter disk.
You set it so the top container drips 1 drop of water per second, and the second container so that it drips 1 drop of water per two seconds.
This allows a pool of water to form in the middle beaker, maximizing extraction surface area.
Because you use ice instead of hot water, far less tannins and oils are extracted from the coffee. It also takes 10 times as long to extract the caffeine and coffee flavors out of the ground coffee beans; this is why the brewing process takes roughly 8 hours.
There are lids/filters on each beaker to prevent dust/hidden nasties from contaminating the brew during the 8 hours it takes to brew the coffee.
8 hours may seem like a long time, but if you start it before going to bed, its ready when your ready to drink coffee. Another cool aspect of cold brew is that it doesn't go stale (unless you heat it, at which point it will go stale if you don't drink it).
Because the coffee doesn't go stale you can supposedly age it and develop the flavors even further.
About the build: These setups normally cost at least $500 for a 12 cup system. I pulled this off for $150. I purchased the replacement parts from Yama (the beakers are uniquely suited for the task of brewing up to 12 cups of coffee). I purchased the glass filter (just wash, never needs to be replaced). I already had the carafe. Not pictured are the stopcocks for the top and middle beakers which are just glass valves for precisely adjusting the flow. I bought them on ebay for $20 each. I am still waiting for them to arrive so I rigged some vinyl tape stopcocks for the first brew.
I drew the design in cad, laser cut templates, and cut it out on a scroll saw. I sanded, primed, stained, lacquered, oiled, glued, and mounted in a few hours last night.
It needs to be as practical as a normal coffee maker in terms of cleaning, ease of use
It needs to produce a noticeably better coffee than a coffee press.
The coffee is amazing. I am not a coffee snob. The purpose of building this was for the fun of building it. I expected to not be able to notice any difference in taste compared to other coffee makers being a non-coffee aficionado... I was super wrong. There is almost no bitterness. It is pleasant to drink black (I am a creamer guy). Everyone who has tasted it agrees unanimously it exceeds expectations in terms of taste (my wife was pretty skeptical about this project).