Me and two brew friends have during the spring stared planning and building a 50L automated electric brew kettle (inspired by the Speidel Braumeister, though not a clone of the mechanism), with a 3.5kW ultra-low watt density element, PID thermostat, and circulation pump. We currently have all the materials, expect the tap valve, and have started with the metal work. The basic construction is presented in the picture below:
The brew kettle will consist of a 50L outer kettle (as a base) and a 35L inner kettle (we have two of these, during the mash one will function as a BIAB bag (it will have stainless steel mesh along the bottom), and during the boil the other will function as a hop bag (it will have stainless steel mesh along the bottom and sides)). The outer kettle will have a drain hole in the bottom, which is connected to a tap and a pump. The pump will circulate the wort during the mash. The mash temperature is controlled by a heating element, which in turn is controlled by a PID thermostat connected to a temperature sensor located before the tap valve.
Here is a picture of one of the inner kettles, with the bottom cut. We will weld fine stainless steel mesh over the holes (mesh placed inside the kettle):
I will post updates on the blog as the project progresses.