... you can drive the heater with a (different) higher voltage - check, if you can change the heater support ... or use a DC-SSR (SolidStateRelay).
Some power sources can be adjusted by a trim-pot, so a 12V PS can be set to maybe 15V max ... but ensure, your electronics (and voltage regulators) can handle this ...
Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [
reprap.org] -- Deutsche Facebook-Gruppe - [
www.facebook.com]
Call for the project "garbage-free seas" - [
reprap.org]