If the hot-side temperature is only 100°C, the turbines really would have to be massive to produce electricity at economically sustainable rates.
Everything would have to be big; condensers, pipes, boilers. The only thing that wouldn't be oversized would be the generator at the end of the shaft.
The Titanic had a low-pressure steam engine to run its center propeller; it was driven by exhaust steam from the low-pressure side of the two triple-expansion steam engines. The rotor of this turbine was twelve feet long and twelve feet in diameter, with the turbine blades adding another four feet of diameter. It's rated power output was 16000 horsepower, or about 12000 kW.
Modern high-pressure steam turbines are about the same size (though smaller in diameter) and generate more like 300,000 kW, or 25 times the power in about the same space. Of course, the Titanic turbine was primitive compared to modern units, with no advanced alloys, low-precision machining, etc.
Granted, in New Zealand they can probably find hotter reservoirs if they look, but economical electric generation requires fairly high temperatures, at least with current technology.
I remember Power Engineering magazine having a glowing report on a power plant going in in New Mexico which would use geo-thermal.
They figured what they needed, bought the equipment including the turbine-generator, set it all up, drilled the hole.
All the equipment was up for sale in a later edition of the magazine. They didn’t get enough heat out of the hole to make anything work.
My assumption was a more accessible source of hotter temperatures or steam/water transfer. Not sure if that is feasible. Thank you for the info, particularly regarding the massive Titanic turbine and how modern ones differ.