16 September 2011

ECONOMIC AND ENVIRONMENTAL EVALUATION OF CO2 HEAT PUMP SYSTEMS TO SUPPLY HOT WATER FOR A HOSPITAL


An electrically driven heat pump using CO2 as the refrigerant is developed to
supply hot water with a high coefficient of performance [COP] for use in buildings such as hospitals, hotels, and so on. In addition, these COP values of conventional heat pumps which
use alternative chlorofluorocarbon gases have also risen step by step in recent years. This study compares several alternative heat pump and hot water tank systems as well as a
gas-fired boiler system from economic, energy saving and environmental points of view based on a mathematical optimization method. A hospital is taken as the objective of this study, and
the energy demand for hot water supply is estimated hourly and monthly through one year. As there are alternative modes for the system’s operation, a mathematical optimization method is applied at this stage for responding to changing energy demands in a timely manner. The
economic evaluation of the systems is done by applying the annualized costs method. Our results show that there exists an economically optimal combination of heat pumps and
hot water tank of proper capacity. It is also seen that systems adopting heat pumps have advantages over gas systems from the economic, energy saving and environmental points of
view.