I admire your inginuity but I am missing something that may have been earlier in the thread, but if it was I've missed it. My question is, why would you want to take this route rather than a more conventional RIMS or HERMS?
I am looking for something to do step mashes with a cooler based mash vessel. I want my mashes to be as traditional as possible, ie the least amount of pumping and the gentlest heating. With a well insulated cooler, one should only have to add heat once in a while to maintain temp and other than that just boost it periodically as per the schedule.
The problem with RIMS (ie a heater element heating circulating wort) is wort scorching, especially if the recirculating flow isn't high. In order to avoid wort scorching, one has to get the power density down to less than 10 watts/in^2, as far as I can tell.
The problem with a conventional HERMs system (heat exchanger in the HLT) is that:
a) the HLT water has a lot of mass, so its hard to quickly change its temperature for step mashes
b) One really needs 2 pumps or at least a pump and a stirrer. One pump circulates the wort and the other device moves the water in the HLT. If the water in the HLT isn't moving the heat exchange is poor.
HERM systems work, but its a slow responding system. People have gotten around this by using a very small dedicated heating tank, but now we are talking another vessel, heating element, etc.
So, I am proposing 2 new ways of heating the mash.
The first method is the steam injection system. This is theoretically a non circulating system ! The mash might be stirred occasionally and probably as the steam is being added, but the heat goes to the mash rather than the wort to the heater. I've got my boiler built and pressure tested. I'll be generating test steam one of these days when I get time.
The other method is the microwave RIMS system. What I like about it is that we have full control over the microwave power output, there is no scorching of the wort, the temperature response should be fast, I don't have to put a heat exchange coil in my HLT, etc. Its a pretty simple system.
"Well, if I attempt this it will really be a preheater for my boils. After reading the thread on using the tankless water heater this sounds like a viable alternative the that."
Yeah, it should be. I wonder if the tankless hot water heater would scorch the wort. Generally heating elements for water are fairly high watt/in^2.
"Does that sound like a good idea to you guys?"
As far as a preheater for the boil, a microwave doesn't output much power compared to a burner. 1300 watts is only 4435 btu per hour. If your sparge took 30 minutes and drained 6 gallons (50 pounds), it would only raise the temp of the wort by 44 degrees. (From 170 to 214F.) I mean it helps, but its not a powerhouse in that regard.
I see it more as a means to gently heat recirculating wort. It could work really well for doing 5 gallon step batches in a cooler.
Truthfully, I am thinking the steam generator is going to work really well and I might not test the microwave heater. But if I was only interested in 5 gallon batches, I think I would be using it.