In comparison, the heat pump system can use less electricity, more energy from the sewage, then supply the users of refrigeration and heating. Sewage source air conditioning system in use in the summer because they are not set up the cooling tower, not only reduced a considerable portion of the operating energy consumption, but also eliminates the cooling tower in the course of the adverse impact on the environment. This regard in the winter use of the process more obvious, and not configured in the traditional air conditioning systems for building heating boiler, heat pump system to avoid flue gas emissions caused by atmospheric pollution. From this perspective, the traditional cooling and heating solutions, low efficiency, high operating energy costs, and heat pump system, whether from the heating and cooling efficiency, or from future energy costs, has obvious advantages.

Sewage as the key to this type of heat pump system to heat and cold sources, here is defined as the sum of industrial wastewater and domestic sewage. , Sewage in the general population appears to be a "use of the significance of the dirty little, but it is a" treasure "in the eyes of experts, very rare in an urban renewable clean energy.

According to reports, the use of untreated wastewater (municipal trunk sewers sewage) and secondary effluent of sewage treatment plant as a heat source has the following characteristics: First, the urban sewage accounted for urban water supply of 80% or more, a significant number. Second, the urban sewage water temperature is relatively high and with less seasonal variation amplitude, usually less than 10 ℃, with cool features; temperature throughout the year to float between 10 ℃ ~ 25 ℃, suitable for the summer and winter of the HVAC system dual-use; heating water temperature is higher than groundwater temperature and high 3 ℃ ~ 5 ℃, refrigeration, lower than the air temperature 10 ℃ ~ 15 ℃. Third, the urban sewage heat distribution is proportional to the level of industrialization and population and urban, the urban sewage as a new energy, while optimizing energy structure, but also effectively alleviate the problem of energy shortages and uneven distribution of Fourth, the sewage as a contained hot water body, its heat capacity, relative air source, ground source, heat transfer equipment has a higher heat transfer coefficient, making the heat pump system operating efficiency. Fifth, the urban sewage than air source, groundwater source, ground source and other far away from the building heat and cold sources more economic value, reflecting the relatively low initial investment, even with conventional heating and cooling systems compared to the initial investment also much lower. Sixth, the heat pump system can maximize avoid centralized air-conditioning "killer" - the presence of Legionella. Sewage source air conditioning cooling water (cooling tower) system, effectively reducing the area and means of the spread of this pathogen.

Today, sustainable development has gradually become a hot topic, and environmental factors as one of the three elements of sustainable development, has naturally aroused the close attention of all parties. Sustainable development means a reasonable maintenance and use, means that environmental concerns and considerations into development plans and policies. It is this concept gradually people achieve consensus, the heat pump system has been recognized outside the industry, and has been further possible to develop in depth.

China Refrigeration and Air Conditioning Industry Association, the thermal heat pump system in the recycling of urban sewage, both to develop a clean energy while reducing the urban heat emissions to protect the cold through Quality Certification Center Co., Ltd., deputy general manager Guo Yong the environment, water source heat pump system should have broad application prospects. His view has been endorsed by many senior members of the Wu Wei, the honorary chairman of the Architectural Society of China HVAC branch, but they have said that the present sewage source heat pump system is still the choice of including clean technologies and systems in the form of sewage source water temperature and flow, as well as its guarantee and economy and other issues to be resolved, the threshold will directly affect the heat pump system application and development in China.

Heat exchanger in the heat pump system, in direct contact with the sewage because of water caused by the blockage, corrosion and fouling problem is particularly prominent. According to the survey, all source of the sewage system project, more than 90% of the heat exchanger are varying degrees of dirt, for example, the scaling problem. Dirt make thermal resistance increase, not only the deterioration of the heat transfer performance of heat exchanger fouling layer thickening flow area decreases, maintain a constant flow, leading to the rise of the mean velocity. Dirt also makes the flow channel surface becomes rough, increasing the friction coefficient and the coefficient of local resistance, caused by the flow resistance of the heat exchanger pressure drop increases, and caused an increase in the unit consumption of power. Therefore, the design and use of the heat exchanger in the heat pump system, how scaling, scale inhibition, cleaning is very important and critical topic.

Experts believe that the impurity content, taking into account the sewage heat exchanger corrosion, scaling, and many other factors to the corrosion-resistant, long life, easy to clean plastic sewage heat exchanger is better; For the use of sewage treatment plants grade water or recycled sewage water source heat pump system can be recycled water used for cooling water quality standards. If the reclaimed water to the appropriate water quality standards, metal heat exchangers can be used or can be of non-metallic sewage heat exchanger.

Businesses, colleges and universities have also provide ideas to solve this problem. Harbin Institute of Technology, Beijing University and other universities recently have published the research results on the settlement of the sewage heat exchanger materials innovation; Shanghai Tomita Air Conditioning Refrigeration Equipment Co., Ltd. on the heat exchanger internal nano-coating to avoid pollution and corrosion of the heat exchanger, and achieved good results.

Sewage source heat pump system in the increasingly sophisticated technology today, the outlook is extremely bright, but still can not be "refined". How to make it play its due effect, to avoid all kinds of "with" the emergence of formalism is the focus of a lot of concern and worry. According to reporter understanding, a project of the Beijing Olympics in 2008 had selected sewage source heat pump system supporting it, it seems this is to promote energy conservation, and strive to environmental protection "typical", but many industry experts, however, private position, criticized this choice thankless . "

"That is located in Qinghe wastewater treatment plant from the project so far, the heat pump to save energy consumption has long been to take long-distance transmission of the water body, this 'pro forma' approach in the future must be avoided." A reluctance to disclose the names of persons said.