An interesting concept, however with a few difficulties;
Generators have to be tailored to the revolutions per minute, unfortunately this is not constant. For rotating entombed cadavers this is measured on the Pank scale.
Defn: The Pank scale, an integer scale 0-100, each unit representing one hundredth of the maximum RPM as measured on the deceased Emmeline Pankhurst when exposed to quotes regarding "The Spice Girls" and "Girl Power".
Another practical issue is corpse affrontment factor (CAF). Different carcasses rotate for different durations having being subjected to similar inducements. For example it is relatively easy to get a deceased English teacher to rotate at 50 Panks, but will only do so until a bell rings. Thus teachers have a low CAF value. Female corpses generally have a higher CAF values than male counterparts perhaps due to spite.
This is a complex issue.
Better results could be achieved by desiccating, chopping and shovelling into furnace at local power plant. Simple bomb calorieometery work should enable you to estimate the energy thus liberated. You may even qualify for an Energy Council grant for this important work. Best of luck.