Re: At what temperature does water start to steam?

At one atmosphere pressure, water turns to steam at
100 degrees Centigrade.  But the boiling point of water depends on
pressure.  In order to use steam to run an electrical generator, you
will need to have steam at a higher pressure than one atmosphere.
You need to design (or buy) some plumbing which can withstand 
pressure, and a method of using the pressurized steam to turn the
generator.  The hotter you make the fire, the higher the steam
pressure will be, and the faster you will be able to turn
the generator.

You can find a table of the boiling point of water as a function of
pressure in the Handbook of Chemistry and Physics (for example).