Drain-water heat exchangers: the efficient technology
The wastewater heat recovery systems that use heat pumps to capture and recycle thermal energy from drains and sewer lines is an economical and environmentally friendly technology.
ETPA reports that wastewater potential of industrial enterprises such as dairy, meat processing, textile industry, medical institutions, hotels is so far untapped. The average temperature of the wastewater is between 30 and 75 °C. Based on water consumption measurements, the estimated daily wastewater volume is 240 m3 (240,000 ltr). In various industrial (eg light) companies, after technological processes, the waste water temperature can reach 50-70 °C. The use of thermal energy from heat pumps results in high seasonal operating factors, enabling the economical and environmentally friendly use of internal heat recovery systems.
Continued efforts to reduce the heating demand of industrial plants will significantly increase the share of energy used for hot water supply in the coming years. This huge amount of energy is usually released into sewage systems without the use of thermal energy. To achieve Europe’s climate protection goals, heat recovery from wastewater offers tremendous and untapped potential for utilizing resources that will reduce the load on heating installations. Particularly significant reduction of thermal energy consumption from heat-generating plants in industrial plants, where large quantities of high-temperature water are discharged into sewage networks.
It is clear that heat recovery from wastewater with heat pumps is certainly not new. Since the 1980s, centralized systems in Germany, Switzerland and the Scandinavian countries use heat in wastewater. Either in a sewage system or in a sewage treatment plant. The temperature of wastewater from residential buildings is about 10-15 ° C a year, and up to 20 ° C in the summer. During the winter months when there is a high demand for heating, the waste water temperature is only about 10 ° C, which reduces the efficiency of the heat pump. However, in sanatoriums and especially in industrial plants, the temperature of wastewater after technological processes is independent of the season and almost unchanged.
The research published in 2020 journal Energies shows that waste heat recovery has a great deal of potential in helping to achieve 2050 climate goals. For example, heat from data centres, metro systems, public sector buildings and wastewater treatment plants could be used to supply 10% of Europe’s heat demand. Despite this, at present, urban waste heat recovery is not widespread and is considered an immature technology. The policy of raising awareness of waste heat recovery, encouraging investment and creating a legal framework should be implemented. It is also recommended that pilot projects should be promoted to help demonstrate technical and economic feasibility.
