Residences in the United States use 10.8 × 109 MJ (10.25 quadrillion Btus) per year, and the resulting energy cost exceeds $5 billion annually. Electricity use accounts for over 30 percent of residential energy needs. This electricity is typically provided by large remote power plants that discharge more than 60 percent of input energy as waste heat to the environment. The advent of fuel cell power systems makes on-site power generation feasible for residential applications. With on-site generation, waste heat can be recovered and used to meet the thermal needs of the residence including space heating and water heating. Combined heat and power (CHP) systems can substantially reduce the energy required for residential applications.
The energy use and economic benefits of fuel cell based CHP systems are investigated for single-family residential applications. Hourly energy use profiles for electricity and thermal energy are determined for typical residential applications. A mathematical model of a residential fuel cell based CHP system is developed. The system incorporates a fuel cell system to supply electricity and thermal energy, a vapor compression heat pump to provide cooling in the summer and heating in the winter, and a thermal storage tank to help match the available thermal energy to the thermal energy needs. The performance of the system is evaluated for different climates.
Results from the study include an evaluation of the major design characteristics of the system, load duration curves, an evaluation of the effect of climate on energy use characteristics, and a comparison of the life cycle cost of the fuel cell based CHP system to the life cycle costs of conventional residential energy systems.