With the adoption of the Energy market in Bulgaria, large fluctuations in the price of electrical energy have been occurring, which is a challenge for businesses in the different sectors of the economy. This study is aimed at evaluating the energy and financial performance of three energy management strategies for operating hybrid hot water installations in hotels: the first one is one assumes the water is heated only by an evacuated solar tube system; the second one assumes electrical energy is used whenever the water’s temperature falls below a certain threshold; and the third one uses preliminary pre-heating of the water during the off-peak hours when electrical energy is cheaper. A simulation model has been developed based on well-known physical and empirical dependencies, allowing for the necessary evaluations. A hot water installation operation has been investigated for a hotel with a capacity of 80 guests on a sunny summer day. The results showed that the first strategy does not allow for maintaining the temperature of the water in the tank above the required threshold. The second strategy ensured the requirements towards the water temperature are met with minimal application of electrical energy, leading to daily expenses between 3.4 EUR and 62 EUR. The third strategy increased the grid energy usage, but the daily expenses were limited to 18.5 EUR. The obtained results indicate that hotel owners could significantly reduce their hot water expenses with the help of a hybrid hot-water installation and an appropriate energy management strategy.
Evstatiev et al. (Thu,) studied this question.