On April 28 and 29 during the long holiday this spring, an experiment for adjusting the demand and supply of power using a large sodium sulfur (NAS) battery system was carried out at a research and development base of Honda R&D Co Ltd in Wako City, Saitama Prefecture, Japan. The experiment took place at the Automobile Center (Tochigi) in Haga Town, Tochigi Prefecture. The storage battery features an output of 12MW and a capacity of 100MWh (Fig. 1).
The system is one of the largest in the world among storage batteries introduced to offices of power consumers.
Honda R&D is engaged in research and development as a subsidiary of Honda Motor Co Ltd. A variety of power generation equipment and storage batteries have been introduced to the center for use by the on-site grid. The company has also been carrying out validation tests of demand/supply adjustment for stabilization of power systems in collaboration with the Tokyo Electric Power Company Holdings Inc (TEPCO) Group and utilizing the systems.
Kyushu Electric Power Company Ltd controlled (limited) the output from solar power plants during the period from the autumn of 2018 to the spring of 2019. It is likely that the supply exceeds the demand in the daytime in spring and autumn, when the load is low, in other regions in the future following introduction of solar power plants on a large scale.
The days on which the supply/demand adjustment was carried out were fine and clear when supply tends to exceed demand. It is possible that output control will be implemented in the regions covered by TEPCO in the future.
For grid operation, power companies began to ask companies that consume power in large volume to make adjustments to operations at their plants, in addition to other efforts including the adjustment of thermal power generation and interchange among regions.
In the experiment, a large storage battery owned by a consumer is used for supply/demand adjustment, which is an advanced solution in Japan. At this stage, the number of consumers that own large storage batteries is limited, but entities that have storage batteries larger than a certain level, including electric vehicles (EVs), will increase in the future.
If supply/demand adjustment of this kind is realized through cooperation of many more companies, solar power output control will be minimized, realizing stable grid operation while receiving more solar power to grids. To increase solar power continuously and utilize the power as much as possible, the use of consumers' storage batteries is one of the promising technologies.
For the supply/demand adjustment in April this year, TEPCO did not provide a financial incentive, etc, to Honda R&D. Honda R&D wants to cooperate with TEPCO to establish a grid operation system that maximizes the use of power generated by renewable energies, according to the company.
The power supply tends to exceed the demand during the long holiday in spring because the demand for business use declines. Power companies normally make adjustments by controlling thermal power generation and using the power for pumping water at pump-storage power generation plants. The demand was increased by using the NAS battery at Honda R&D, and the effect of the battery for reception of more renewable energy was confirmed.
Specifically, the NAS battery was charged by the power from the grid for three hours in the daytime, and the charged power was discharged for six hours in and after the evening for use on-site. The demand was increased in the daytime when solar power tends to exceed the demand, while the stored power was consumed on-site in and after the evening, when the solar power generation amount decreases and the demand increases, to reduce the amount of power received from the grid.
This supply/demand adjustment is possible because the center consumes a large amount of power even on holidays. The center consumes power constantly for durability tests, etc (Fig. 2). The equipment is constantly in operation to perform the tests on a 24-hour basis.