Concepts and classification concerning municipal sewage heat energy utilization

Classifies the municipal sewage as crude sewage, primary sewage and secondary sewage from the aspect of heat energy exploitation. Analyses the application characteristics and prospects, and states that the crude sewage will be the main source of heat energy usage in the future. Clarifies the concepts such as the sewage heat energy utilization, sewagelike cold/heat sources, sewage source heat pump, sewage source heat pump system (SSHPS), and points out their categorical relationship and status. Classifies the SSHPS as direct systems and indirect systems, compares their merits and faults, and indicates that the direct system has huge space to be developed. Presents two realizable forms for this system.