Energy optimization of a thermal storage tank for Domestic Hot Water production

Abstract

[EN] According to the European Commission, the residential sector is responsible at this moment of the 40 % of the energy consumption and 36 % of the associated CO2 emissions in Europe. Regarding the water heating consumption, it is currently responsible for 14.5 % energy consumption of the average European dwelling. This percentage is expected to increase drastically within the concept of Near Zero Energy Building (NZEB) since the associated heating consumption percentage will be decreased largely. In this way, the energy consumption associated for water heating should be reduced, and it only can be done by using highly energy efficient technologies, such as heat pump (HP), and decreasing the energy losses associated to the facilities. In the frame of the European Project NEXTHPG of the 7th framework program, a new prototype of heat pump booster for the production of domestic hot water was developed. The developed prototype uses an innovative subcooling control system, which allows increasing the COP of the system in more than 30% compared to conventional subcritical heat pump systems. Nevertheless, in a real installation apart from the heat pump there are other factors contributing to the final energy consumption of the whole system like system configuration, control algorithm, tank size and the like. Therefore, an estimation of the final energy consumption of the system could be significantly different from the obtained taking into account only the pump performance. The present work is focused on the development of a model in order to optimize the design of the whole system using the prototype of the NEXTHPG project in order to satisfy the domestic hot water demand of a building for 20 people. The integrated system model will include the heat pump, the water tank, a heat exchanger in order to recover part of the waste heat (such as the heat coming from the sewage water in the domestic sector or from condensing loops in tertiary sector) and a random generator of domestic hot water demand profile. From the results of this work, the proper sizing of the heat pump and the water tank, as well as the control algorithm, are obtained and the potential annual energy consumption of this type of system is estimated.