Feasibility Study on Power Interchange Operation of Multiple Household Gas Engine Cogeneration Units by an Optimization Approach

Abstract

Household cogeneration systems have been increasingly utilized for energy saving; however, their energy-saving effect in Japan is not necessarily sufficient due to their operational restriction that electricity generated by them cannot be transmitted to commercial electric power systems due to the regulation. To relax the restriction, the authors propose power interchange operation of multiple household gas engine cogeneration units and investigate its feasibility from the energy-saving viewpoint by an optimization approach. In this power interchange operation, a micro-grid using the units is constructed in a housing complex; electricity generated by them is shared among households without transmitting to a commercial electric power system outside the housing complex so that the operating time of these units may increase. To evaluate the energy-saving effect of the power interchange operation, a numerical analysis of operational strategies by the mixed-integer linear programming is conducted for ten households and three types of household energy supply configurations: the power interchange operation of the gas engine cogeneration units, a stand-alone operation of each gas engine cogeneration unit, and conventional energy supply system without the gas engine cogeneration unit. A computational result clarifies the advantage of the power interchange operation from the energy-saving viewpoint over the other energy supply configurations.

Suitable operational strategy for power interchange operation using multiple residential SOFC (solid oxide fuel cell) cogeneration systems

“…Second, the energy balance and supply-demand relationships for electricity and hot water are considered. Those for the electricity depend on the household energy supply configurations [11]. For the IC, they are considered for the housing complex; for the SA and CO, they are considered for each household.…”

“…The characteristics of these demands are summarized as follows [12]: the energy demands are less than those for typical detached houses in Japan; the hourly electricity demands, which are mainly used for air conditioners, appliances, and lighting, differ widely among the intended households on any representative day; the hourly hot water demands are concentrated in the nighttime in any household on any representative day. The authors consider the total daily heat to power demand ratio of the 20 intended households THPR to be the dominant characteristic of the energy demands that affects the energy-saving effect of the IC [11]. The total daily heat to power demand ratio on the mth representative day is defined by the following equation:…”

“…Thus, the authors focus on only the interchange of the generated electricity. The authors have clarified the high energy-saving effect of the power interchange operation using multiple residential gas engine cogeneration systems, which must adopt a rated output operation, has been clarified [11,12]. The power interchange operation is also expected to improve the energy-saving effect of R-FCGSs because the aforementioned operational restrictions can be relaxed.…”