The preparation of hot sanitary water in an average household represents approximately 10 % of all energy needs. It is a process that takes place every day in every residential and also non-residential facility to ensure human comfort. Hot water is used for cooking, laundry, dishwashing, washing, showering or bathing. After use, the entire amount of hot water is poured into the sewage system, thereby throwing away not only the water but also all the heat that is still accumulated in it. By using a system for reusing the heat of waste hot water, the water is stored in a tank, from which thermal energy is extracted with the help of a dedicated heat pump. The heat is then used to heat fresh sanitary water. The hot waste water is cooled to a lower temperature before being poured into the sewage system, and the fresh sanitary water is partially heated with the same amount of heat. The portion of heat that is reused represents energy savings for the user. The water just needs to be heated to the desired temperature. Energy savings for the preparation of hot sanitary water in the case of using a waste water heat reuse system can be up to 50 %. In the diploma thesis, we calculated energy savings in the case of the installation of a waste water heat reuse system, which would be used to heat fresh pool water and sanitary water for the needs of showers in the pool complex, using the example of the Faculty of Sports of the University of Ljubljana.
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