There are solutions in the market for this. The heat recovery system is filled with glycol solution, which means it doesn't freeze over even if left unpowered during sub-zero outside temperature. Then there's a temperature sensor and a control unit that only runs the pump when the fluid in the panels is warmer than the warm water accumulator of the home heating system.

The heat collectors are vacuum insulated, so provided with enough solar radiation, they will work even when it's very cold outside. These systems work okay for example here in Finland. Of course it's a limiting factor that you normally need the heating most when the solar radiation is at the minimum. If you've got a swimming pool or some other use for the hot water during the summer, it's a good deal.