I used a homemade peltier cooler for temp control for about a year. It was great fun to build and mess around with. I used an Arduino controller. I learned a ton about both peltiers and programming Arduino's in the process. For me that made it worth it.
I eventually bought a freezer off of Craigslist and moved my controller over to that. The peltier setup had a number of shortcomings. Probably the most important one was that my engineering would fail from time to time. I got tired of fixing it! lol
The think about the Peltiers is that they are not very powerful. I had a two chip setup. I delivered the cooling to a glass carboy with a 25' long 1/4" copper tube that was coiled around the carboy. I insulated by wrapping it all up in packing blankets and securing it with bungies.
Because the system has limited cooling, efficiency of heat transfer is critical. You need to make sure the chips are super efficient at moving the cooling to the heat exchange block. That is the blue aluminum block in the example you linked. Having really good technique with thermal paste is important there. (That was a learning curve for me.) I would think that the unit you showed would require some serious insulation. It is going to loose a ton of cooling just in the aluminum retainer plates and the lines that loop them all together. Depending on your ambient temperatures and humidity, you are also going to get condensation. Insulation will help with that, if you do a good job of sealing it up.
What I found in my time using one is that, even when I got things working really well, that it just barely had enough cooling to get down to the low 60's. (Especially in the summer, even in my relatively cool basement.) I was able to get about a 10 degrees delta from ambient with mine. It also really struggled during very vigorous ferments raising the temp. I found that for some brews the insulation around the carboy stopped it from shedding heat and the cooler could not fully keep up.
The design of the one you linked is interesting though. I constructed mine with the peltier on either side of a single water block. The unit you showed appears to be in series. That would allow the second and third blocks to start cooling at a lower temps. It would be interesting to see how well that worked.
The other piece of advice I would give you, is that the mechanics of pumps, cooling fluid, and heat transfer into your fermenter cost you a lot of efficiency. That is inevitable of course, but because the peltier doesn't have a lot of extra capacity it is essential to come up with a really good design. (I was using glass carboys, which also create some inefficiencies in heat transfer.)
The brew jacket tries to avoid many of these losses by only having two transfer surfaces. The peltier to the rod and the rod to the beer. My water cooled system had 5 (Peltier to block, block to water, water to tubing, tubing to fermenter, fermenter to beer.) Toward the end of my time with my system I had contemplated making something like the brew jacket cooler. However, if I was going to continue to use liquid cooling. I had plans to make a stainless tubing bundle that would fit down the mouth of the carboy and sit in the beer. I figured this would greatly increase efficiency.
As I said, this was a really fun learning experience for me. I don't regret it at all. Before I spent more time investing in that system, I got a really good chest freezer off Craigslist for $50. Which is way less than I spent on peltiers and the associated equipment. (They do burn out if you don't adequately cool the hot side.) I had the space for the freezer, and for me it was a wonderful choice that didn't need fixing all the time. It just works and I can rely on it to do it's job.
Whatever you do, please keep us updated.
