Un-Packing the Heat: Urban Streets to HVAC

Wastewater is the encompassing term for human excreta, plus so-called "graywater". The latter is the stuff we discharge from food- body- dish- and clothes-washing. As the Chinese Academy of Engineering points out, in a SciDev.net story, you can use wastewater's capacity to give and take heat to significantly increase domestic heating and air conditioning efficiency. Hey TreeHuggers: we told you there was more good stuff just around the corner.Rather than separate gray- from sewerage-water, they seem to be aiming at using all wastewater. Not sure that combined discharge part would make sense in developed nations that have already invested in extensive wastewater collection and treatment: you'd have distributed, self-purging bar screens that were redundant on the city systems. Anyhow, the basic concept relies on off-the-shelf-engineering and has good applicabilty for commercial, municipal, and apartment buildings anywhere where there's a constant confluence of in-building discharges toward the collection main, but before much heat is lost enroute to the sewerage treatment plant.

As reported in the SciDev.net story of July 15: "Chinese researchers say they have" ... "created a device that extracts heat from raw sewage that has been temporarily diverted on its way to the processing plant...The device makes the air conditioning units run more efficiently, and absorbs the heat removed from the buildings. It can reduce the cost of heating and air conditioning systems by 20%, says lead researcher Sun Dexing, a professor in the environmental science department at Harbin Institute of Technology"..."After reclaiming some heat from discharged wastewater, HVAC refrigerant... "is compressed to further warm it, and diverted to a condenser, which heats a water-filled coil. A fan blows the heated air around the coil into the room"..."In summer months, the process works in reverse. Heat from the air is transmitted through the coil and back to the condenser and then onto the liquid portion of the sewage".

From an engineering standpoint, piping, ducting, and electricals could be common with the Ice Energy device that is capable of adding 30% efficiency to air conditioning. Put Ice Energys' 30% with the proposed 20% gain from this idea and you approach 50% effficiency increase with less capital and maintenance. We oughta get these people to meet!