> If you cycle between 45 C and 55 C water temperature (as mentioned by the press release), you are only getting a 10 C delta.

You are calculating the wrong delta T. To heat a space, you need your working fluid to be warmer that the space you’re heating by an appropriate amount.

55°C is certainly on the cool side to heat a building, but it’s entirely workable with a high-area, highish-thermal-conductivity system. Here’s an actual chart:

https://www.warmboard.com/wp-content/uploads/2022/04/WaterTe...

You don’t actually want an absurdly warm floor.

Even for buildings that need warmer fluid, water at 45-55°C is a fantastic source for a heat pump.