An Estimation of Reduction of the Primary Energy and the CO₂ Emission in Residential PEFC Co-Generation System with Li-ion Battery Modules

Abstract

This paper presents the effects of introduction of residential polymer electrolyte fuel cell (PEFC) co-generation system with batteries in comparison with conventional systems that consist of a gas boiler and electric power from commercial grid, by computer simulation. The PEFC co-generation system in commercial use provides the average primary energy saving rate of 12.7% and CO 2 reduction rate of 15.4% with respect to the conventional system. Addition of 8.0-kWh batteries to the PEFC system results in limited improvements of 0.8 points and 0.9 points in the reduction rates, respectively, yielding 13.5% and 16.3%, when using a conventional operation planning method. A new operation planning method is proposed in order to make a precise control of charging and discharging the batteries. The average primary energy saving rate reaches up to 16.9% by the improvement of 4.2 points, and CO 2 reduction rate reaches up to 20.4% by the improvement of 5.0 points in the PEFC co-generation system with 8.0-kWh batteries using the new operation planning method. The new method can thus realize a substantial improvement in reduction rates. Furthermore, it is shown that the suitable battery module capacity for the residential PEFC co-generation system is 4.0 kWh.

Improved Optimal Operation Planning Method Based on Tabu Search for Residential PEFC-CGS Considering Ramping Rate

“…In addition, we also used modified local search (MLS) in the simulation for the purpose of comparison. Table 4 shows the summation of electricity demand and hot water demand in each season, which is determined based on [7]. The demands are assumed to be known in advance.…”

“…The demands are assumed to be known in advance. According to [7], these demands are measured values. Reference [7] classifies hot water demand into 3 patterns, large, middle, and small on the basis of the summation.…”

“…In this paper, we assumed 2 cases of ramping rate constraint. One is harsh ramping rate; the other is standard one [7], and they are shown in Table 5. The value of harsh case, case 1 is selected the half of standard ramping rate.…”

“…Therefore, we introduce the electricity and heat efficiency shown in Figure 2. The efficiency and the specifications are assumed based on [7]. According to [7], they are not the best ones in Japanese top-runner program, but reasonably selected considering aged deterioration.…”

“…The efficiency and the specifications are assumed based on [7]. According to [7], they are not the best ones in Japanese top-runner program, but reasonably selected considering aged deterioration. In addition, the adequacy of the specifications is calculated and evaluated in [8].…”