The heat exchangers and pipework required to make a 10MW plant already exist, but the 100MW facility will need a pipe that is not only 1km long (in order to reach the coldwater at depth) but ten metres in diameter (in order to bring enough of that coldwater to the surface).
The habitable zone is the region of a planetary system which is neither too hot nor too cold - such that water on the surface of a planet will neither evaporate nor freeze, but instead can stay liquid.
Because coldwater releases more CO2 into the air than warm water, the rate at which bottom water rises to the surface has a profound effect on the atmosphere above.