Compressed air or oxygen into the compost pile?
Outside United States
Although compost water heaters are an exciting concept, I have yet to see an example of one of these in my State (Utah). If you are concerned that the mound will become too saturated, it would not hurt to push oxygen into it to keep microbial life and associated heat at a high efficiency level. I'm sure you've seen it, but if not, you may wish to read "The Compost-Powered Water Heater" http://books.wwnorton.com/books/The-Compost-Powered-Water-Heater/. My extension work has mainly focused on simple backyard compost systems and vermicomposting. I would love to see a picture of your system.