Absolutely - if I can get a little predictive model going, I could estimate the wort temperature based on weather and wort activity. What I'm planning on doing is developing a thermal model to predict my requirements.
Concerning temperature swing; take this study on the internal temp of a
shipping container, high thermal inertia means much less of an internal temperature swing. The thermal response can be predicted using a
thermal time constant to be determined:
For air and water - the density and specific heat capacity differences are enormous: 1.22kg/m3 versus 1000kg/m3 and 1005J/kg/K versus 4200J/kg/K (these values sit on the numerator of the fraction). The only thing air has going for it is the convection coefficient being lower as air is quite insulative.
So if I put it in water the temperature swing is much smaller. In my water bath last time I had a time constant of about 3 hours - I was only getting about 2 degrees rise after work and then I would just swap a litre or two of the water with fridge cooled water.
I need to figure out how the house responds to the weather, and how the water bath responds to the house temperature, with that and yeast activity as a heat source I might be able to have something just good enough avoid an expensive cooling system.
Probably all of that deserves a separate thread - if I get around to doing this I'll post it about it - maybe write a bit of code or a spreadsheet for others to give it a try.