How would you calculate the energy generated by a thermocouple?

[Warpspeed13]

Say you had a thermocouple 2" wide by half a meter long and the temperature gradient was 2000 degrees Celsius how much electricity would it generate? If it was hot enough could a non metal plasma be used as the secondary conductor rather than a second type of metal?

 

[Simon Bridge]

You would look up the manufacturers specs.
The relationship between the temperature gradient and the potential difference depends on what the material is made of, and will also be different for different temperatures.
There is just not enough information from what you have given.

You may be thinking of:
http://en.wikipedia.org/wiki/Thermoelectric_effect