Shane, that is bottom-hole temperature, not the temperature at...

Shane, that is bottom-hole temperature, not the temperature at the interface between the binary and geo fluids. The data received from HAB3 is a good guideline for the cooling rate as the water travels a path that is measured in kilometres. The boiling point of water (in our case geofluid) has no bearing on the efficiency of this certain heat engine - we're more concerned with the hydrocarbons used in the O.R.C, operating closer to 70C.

Due to the large amount of energy used to bring the binary fluid to boiling point (useless energy), each extra unit of heat has an exponentially larger impact on the efficiency of extraction (up to about 400C, when the rocks at 5000m would begin to display semi-plastic properties, leaving the heat difficult to recover from the rocks).

I agree 180C is more than sufficient for electricity production. Whether is is sufficient for economically-competitive electricity production is yet to be seen.