ᐅ Fireplace with heat recovery system

Hello everyone,
I once came across a solution where a heat exchanger is installed in the chimney or its hot exhaust gas flow, which is then used to transfer additional heat to the heating system for support.
Now my question is: What happens if the power goes out and the pump cannot operate? Would I then be unable to use the chimney as well?

The question is more: Do you really want this? What benefits will it bring you? What are the investment costs (definitely not low)? What type of heating system have you planned?

Underfloor heating. The fireplace is used very often in winter because I have a lot of firewood. The investment is the heat exchanger, sheet metal (I might build it myself), plus the circulation system in the heating appliance room (HAR).

Underfloor heating is not the heating system itself – gas, oil, geothermal, etc.?

Not yet decided: Preferred heat pump. Alternative: Gas

With a heat pump, forget about that – it only leads to problems and short cycling. With gas, it works... in that case, I would rather go for a water-based fireplace.