Environmental and energy saving potential from greywater in hotels

Highlights: • Central located DWHR systems were implemented and analysed in hotel. • Vertical, horizontal heat exchangers were adopted and compared. • Influence of constant and variable supply cold water temperatures was analysed. • Daily, monthly and yearly observations of energy savings were illustrated and discussed. • Carbon dioxide emission (CDE) was calculated and discussed. Reducing energy consumption, increasing energy efficiency technologies and solutions, decreasing emissions are very effective tools towards EU environmental policy. The constant demand for domestic hot water (DHW) throughout the year creates great benefits for drain water heat recovery (DWHR) systems in hotels, which is the most promising and significant feature of energy saving potential for the hotel sector in Poland. This paper determines the feasibility of heat recovery in a typical hotel in Poland. The energy analysis was carried out for the installed DWHR system (from washbasins and showers) at the hotel building. To evaluate the energy saving potentiality, daily, monthly and yearly calculation results were performed for an exemplary hotel in Poland. Two types of heat exchangers were adopted for further calculations: vertical (System 1) and horizontal (System 2), this intention aimed to find the most efficient type and relevant solution of energy saving and reduction of CO2 emissions in the analysed hotel. The analysis and calculations were repeated to enhance the saving potentiality of the proposed DWHR systems for various parameters like constant and variable temperature of supply cold water, daily hot water consumption profiles, the efficiency of heat recovery, reduction of annual carbon dioxide emission (CDE), facility standard of operating procedure, the impact of hotel size, etc. The obtained results of the conducted calculations ensure a significant potential of energy savings by implementing the proposed DWHR systems in analysed hotel, which allow to save energy demand and to reduce CO2 emission by 27.3% and improve the efficiency of the DHW preparation system.