ZEMCH 2019 International Conference Proceedings April.2020 | Page 442
power is supplied to the load after the battery is fully charged. The graph of Mode 4 (September 18,
2019) representatively shows this characteristic. The modes, in which the battery was charged only with
PV (modes 1 and 3), risk full discharge in the absence of PV. Therefore, the ability to maintain battery
voltage is required to use this mode. If the battery charge sources are PV and grid (modes 2 and 4), the
battery is charged by grid power to maintain the battery voltage. The graphs of modes 2 and 4 show
the charge of the grid power before and after the PV time.
As an additional experiment, Mode 4 was applied with changing load to an air conditioner (power
consumption of 2,280 W). The experimental results are shown in Figure 4. The set temperature of the
air conditioner was 22 ℃, and the actual power consumption was about 1,400 W. Based on the PV
generation time, it was confirmed that the battery was charged by PV Power and discharged to the load.
The operation schemes of the residential BESS with the veranda PV were confirmed in individual
households of apartment houses through experiments for each operation mode of the residential BESS.
The results suggest that Mode 4 is the most appropriate among the four operation modes of BESS.
Nevertheless, some functions are still required to apply the scheme to individual households of
apartment houses. First, the load connected with BESS should be the total power consumption in the
household, not the power consumption of the home appliances connected to a separate load line. When
only the veranda PV is installed, the PV power is supplied to the household through the plug of the
inverter to reduce the total power consumption. In order to use the residential BESS to reduce total
power consumption, such as the veranda PV, it is necessary to integrate the grid and load lines that are
currently separated. Second, the battery must maintain the minimum voltage using the grid power
before reaching an unusable battery condition. The charge of grid power is a concept that maintains the
battery voltage at the minimum current rather than the normal charge. Third, it should be possible to
set the voltage range or time for the PV charge. The BESS stops the grid power charge because it
recognizes that PV can charge the battery when PV generation starts. However, there is a risk that the
battery will reach a full discharge state because the PV power is unstable and cannot maintain a
constant charge.
5. Conclusions
In this study, several experiments were conducted with different operation modes to suggest
optimal operation schemes of residential BESS with veranda PV in Korea. The experiments were
conducted in a demonstration house using a 2.016 kWh BESS, a 1.2 kW veranda PV, and electric loads.
According to PV power supply priority and battery charge source, four BESS operation modes were
designed. The results show that mode 4, in which PV power preferentially charges the battery and then
charges the battery with PV and grid power, is the most appropriate among the modes. However, some
functions need to be added to ensure applicability of residential BESS to individual households of
apartment houses in Korea. First, the load connected with BESS should be the total power consumption
in the household, not the power consumption of home appliances connected to a separate load line.
Second, the battery must maintain the minimum voltage using the grid power before reaching an
unusable battery condition. Third, it should be possible to set the voltage range or time for PV charge.
By satisfying the above conditions, BESS with veranda PV can be used efficiently in Korea.
Author Contributions: methodology, data collection and analysis, visualization, validation, writing—original
draft preparation, J.Y. Eum; conceptualization, methodology, writing—review and editing, supervision, Y.K. Kim
Funding: This work was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP)
and the Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea (No. 20172410104720).
Conflicts of Interest: To the best of our knowledge, the named authors have no conflict of interest to declare,
financial or otherwise.
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