I bought an upright charcoal grill/smoker years ago because it was cheap and I was interested in doing both grilling and smoking. However, I didn't find it to be a great grill (too small, and the airflow to the charcoal pan was lousy) and my one attempt to use it as a smoker didn't end well, either (keeping a constant, low temperature with the charcoal + wood was really tough). I've since bought a larger kettle grill and love it, but I would love to try to smoke again with the old upright...but this time, using an electric hot plate instead of charcoal (Alton Brown-style).
My plan is this:
Put the hot plate on the bottom rack (of three), running the cord out the bottom.
Put wood chips/chunks in a heavy pie pan and place directly on the hot plate's heating element.
Put the water pan on the middle rack.
Put the meat on the top rack.
Use one probe-style thermometer to monitor the air temp around the meat, and another thermometer to keep an eye on the internal temperature of the meat.
Add additional wood to the pan as needed through the access door.
Do I need the water pan if using this method? I'm reading conflicting information about the purpose of the water. Most sources say it is to maintain moist air in the closed cooking space, but others say this isn't really true, and that it is used as a "thermal buffer" to absorb heat and/or smooth out temperature changes.
What is the best way to adjust the temperature up or down? My hot plate does have an adjustment knob, but should I also drill some holes in the smoker's lid (it doesn't currently have any) that can be opened/plugged as needed?
1- The meat drying out is a very real problem when cooking for so long. When I have smoked with water it has seemed to be less of a problem. I'm sure it also gives a nice thermal buffer but I haven't conducted experiments on this.
2 and 3-
When I built the AB style smoker mine was smaller and earthenware so it would retain heat better. My cheap little hot plate was not able to get the temperature up to even 200F.
With a bigger smoker and one made out of metal I don't think a normal little hot plate will be able to get hot enough. You can experiment of course. It may be that my cheap hot plate was just under powered.
In my smoker I adjusted the hot plate temp knob as necessary. Eventually of course it stayed at full on.
If you are interested in more of a project- there are many hobbyist projects for making temperature controlled smokers. They would be more work but for an excellent reward. I was just looking at this one today that uses a wireless router for a web interface and an Arduino for control. Kind of like a homemade sous vide setup but for a smoker: http://tvwbb.com/eve/forums/a/tpc/f/9270072103/m/5721075126