That would be a standard industrial solution ...
There are a couple of caveats,
The sensor is probably going to require a high impedance input so hanging it on a long cable carrying a voltage based reference is going to be noisy and probably not work well.
you will of course need two sensors tank and panel ...
In industry these would generally be referred to as transmitters, a module that houses the sensor, converts its output to something useful and calibrated which the control system can use.
4-20mA loops are very common, good for long distances and far less susceptible to noise than voltage based signals.
Because the output is current based small changes in cable impedance do not affect accuracy, the voltage necessary to drive a specific current may alter but the current will not.
It depends on the accuracy you want to achieve ... If you use screened twisted pair you may well get away with driving a PT100 from a constant current source and reading the voltage at the source, cable resistance will only be a tiny fraction of that.
Have you considered driving the pump with PWM based on the temperature difference that way you keep the panel as cool as possible at all times and the overall temperature of the system stable, no slugs of hot or cold water flying about the place.
I think it would probably give you some efficiency gains.
Al