One relatively simple setup that comes to mind is ...
Get a number of elements, of a lower wattage than a normal kettle.
Thermostat that can have it's sensor positioned over the contents so it will be triggered by the steam when boiling.
Relay
Momentary button to set it off.
Then work out the wiring so that on pressing the button, the relay pulls in, and all the elements are connected in parallel for full heat. The relay is held in through one of it's own contacts and the thermostat.
When the stat triggers (the contents are up to the boil), the relay drops out, and reconnects the elements in series for the simmer.
Examples with 1kW elements :
2 elements: 2kW in parallel, 1/2kW in series - 4:1 change in power
3 elements: 3kW in parallel, 1/3kW in series - 9:1 change in power
However, the PID controller sounds much more elegant.
Get a number of elements, of a lower wattage than a normal kettle.
Thermostat that can have it's sensor positioned over the contents so it will be triggered by the steam when boiling.
Relay
Momentary button to set it off.
Then work out the wiring so that on pressing the button, the relay pulls in, and all the elements are connected in parallel for full heat. The relay is held in through one of it's own contacts and the thermostat.
When the stat triggers (the contents are up to the boil), the relay drops out, and reconnects the elements in series for the simmer.
Examples with 1kW elements :
2 elements: 2kW in parallel, 1/2kW in series - 4:1 change in power
3 elements: 3kW in parallel, 1/3kW in series - 9:1 change in power
However, the PID controller sounds much more elegant.