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Japan's Largest Battery-equipped Solar Plant Almost Completed in Hokkaido (page 2)

102MW of panels, 52MW storage battery set up on former ranch

2019/11/19 16:53
Kenji Kaneko, Nikkei BP Intelligence Group, CleanTech Labo
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Designed, constructed by Toshiba, TMEIC

In this project, a storage battery system with a capacity of 27MWh is installed in order to smooth short-time output fluctuations (short-period fluctuations) of the photovoltaic (PV) system. The rated output of the inverters for the battery system is 52.5MW, and Li-ion batteries are used.

The panel capacity of 100MW and the grid capacity of 75MW are the 10th largest among the initial capacities of the mega-solar plants in operation throughout Japan. Furthermore, as a "mega-solar plant equipped with a storage battery system," this plant may be the world's largest and is, needless to say, Japan's largest.

Toshiba Energy Systems & Solutions Corp and Toshiba Mitsubishi-Electric Industrial Systems Corp (TMEIC) jointly provide engineering, procurement and construction (EPC) services and will operate and maintain this power plant after completion. Toshiba Corp provided solar panels (72-cell, 335W/unit), and TMEIC supplied inverters for both solar panels and the storage battery system. TMEIC also built the battery system using storage batteries manufactured by LG Chem Ltd of South Korea.

In view of snow cover during winter, the panels are tilted by 30° and set up 1.3m from the ground (Fig. 4).

Fig. 4: Toshiba panels, TMEIC PV inverters adopted (source: Nikkei BP)

Storage battery system to meet requirement for '1% fluctuation per minute'

The plant installed a storage battery system in parallel with a PV system in order to meet the "technical requirements concerning measures to smooth output fluctuation of a solar power generation facility" announced by Hokuden in April 2015. Hokuden requires a "1% fluctuation per minute" that limits the range of fluctuations in mega-solar plant output combined with the battery's charge/discharge to 1% or less per minute compared with the rated output of the PV inverters. TMEIC's control system helps the inverters for the PV and battery systems coordinate their outputs so they can meet this requirement.

In regard to storage battery systems installed in parallel with a renewable energy system, the cost for adoption is partly subsidized by the national government in many cases; however, such a subsidy system has not been used this time.

In addition, this power plant was required to accept an "unlimited output control without compensation" as its application for grid connection was filed after applications had exceeded the "limit for 30-day output control" within Hokuden's service area. If renewable energy adoption in Hokkaido further advances, Hokuden might issue an output control directive exceeding 30 days per year, which will consequently increase risk in power generation business performance.

Despite the business risk of "unlimited output control" in addition to the "cost for the storage battery system," the SPC succeeded in structuring project finance this time.

Behind the success lies the cost reduction in the storage battery system as well as the improved evaluation and analysis of future output control. To achieve the grid requirement for a "1% fluctuation per minute," a storage battery with a capacity equivalent to about 80% of the PV inverter output is usually set up while the capacity was only about 70% compared with the PV inverters this time.

The adoption of the "TMEIC Battery Control System (TMBCS)," which controls mega-solar output and battery's charge/discharge in an integrated form, as well as the fact that the same manufacturer produces inverters for both the PV and storage battery systems, also significantly contributed to the success (Fig. 5).

Fig. 5: TMEIC built storage battery and control systems. (source: Nikkei BP)