Do a web search for "voltage doubler" or "voltage multiplier" and you will find many solutions.
For AC, using appropriate diodes and resistors in the proper configuration with a transformer will do the trick. There are "step up" Transformers, which have a different number of windings on the primary and secondary coils. For DC circuits, you can obtain free bitcoin mining without investment 2018 low withdrawal-cost integrated circuits to effectively increase the input voltage.

Look up "dc voltage doubler".