[rb808]

Also excuse my ignorance - but does the heat released warm the Earth's atmosphere? I realize it doesn't create greenhouse gases, but wonder if the newly released heat would make a difference to sea & air temperatures, or just gets radiated away.

[hwillis]

It actually warms the atmosphere infinitesimally less than other methods of generating power (aside from solar, wind or hydro). Normally when you burn something to generate electricity the excess heat is released into the air. The same process, with the same efficiency (in fact, slightly better), still happens in geothermal but it also very very slightly reduces the amount of heat coming up from the earths core elsewhere.

[saalweachter]

The short answer is "it depends what they are using as a cold source". They are probably heating the ocean.