T(t)=e−kt(∫ekt[KM(t)+H(t)+U(t)]dt+C)
M is the outside temperature, H is other things that affect temperature
in the tank(0 in this case), and U is the solar panel. K comes from the
time constant, and should be the inverse of the time constant I believe.
T is temperature, t is time.
T(t)=e−164t(∫e164t[164(80)+4t]dt
After integrating I keep getting
−16304+256t+Ce−164t
I calculate C to be 16414 setting t equal to 0 and using the initial conditions