Yeah, what did you have in mind to cook, and what would you be cooking it in?
Would you have 75W total, or is that just your maximum line wattage? If you could have multiple 75W outputs, that would help a bunch.
A single 75W source could only output up to 256BTU/hr. That's not much. Your average open flame stove burner can output around 30,000BTU. So that should show you how little energy you have to work with.
http://www.rapidtables.com/convert/p...att_to_BTU.htm
You can then convert that BTU rating to the area you're cooking in. You want 75-100 BTU per square inch, to cook most food. So you could successfully heat an area the size of a few square inches with with a single 75W source.