If you got any real heat from it, I think it would stop the composting. The bacteria that make it work need pretty high temperatures to really do anything. Any heat you pull out would just kill the process. The other thing is the gasses given off by the compost. In a close environment like a winter greenhouse, it could be deadly.

That being said, there is no reason to put pipes in it. All the energy released by the compost will leave the pile and go into the air. No reason to put plumbing into it. Energy can't be destroyed, so it will come out of the pile at the same rate it is being released over time. Putting PVC pipes in the middle to prevent turning soulds like a good idea.