I use SSR (Solid state relays) to control the elements in large industrial dryers They can be cycled rapidly to regulate the elements controlled by a temperature controller or thermostat. Athena Controls as well as others make proportional control relays that can control the amount of current that passes. These are driven by a 4-20 ma controller. Thermocouple needed to send the temperature to a controller. Somewhat complicated for just a heater. I think a SSR with a standard thermostat would be better.
