Energy storage system
Grid Scale ESS
Moving towards the goal of climate and lower-carbon actions, Taiwan is developing green power actively, along with the installation of energy storage systems (ESS). According to the Forward-Looking Infrastructure Project, the Bureau of Energy, Ministry of Economic Affairs has launched the “Regional ESS Technology Verification Project”. Therefore, Taiwan Power Company (TPC) and Industrial Technology Research Institute (ITRI) have cooperated on developing ESS in Taiwan. ESS can not only smooth green power generation, but also maintain power system frequency stability. In addition to those advantages, it also increases the capacity value of renewable energy and solves the problem of power dispatching.
The target for Battery Energy Storage System (BESS) in 2025 is 590MW. TPC will build 160MW of equipment in own site and purchase 430MW through ancillary services. BESS can help smooth the intermittency of variable renewable energy. After a power system accident, it can help withstand the trip of one largest unit without touching the low-frequency relay action to trip the user load.
At present, February 2021, TPC has completed energy storage battery systems at two sites, including Kinmen with a total of 3.8MW (11.8MWh) and the Sulin branch of Taiwan Power Research Institute with a total of about 1.25MW (1.9MWh). At the same time, ITRI has also completed energy storage battery systems at TPC's Solar PV sites in Yong-An Kaohsiung, Long-Jing Taichung and Zhangbin Changhua, with a total of about 6.5MW (6.4MWh). In addition, TPC expects to purchase 45MW of battery energy storage equipment in 2021.
In 2020, TPC also purchased 15MW automatic frequency control (AFC) ancillary service from five private companies. These energy storage battery systems will start operation in 2021.
Kinmen Energy Storage System
Kinmen is an islanding power system. As renewable energy penetration increases, a possible way to make the power system more reliable is to install energy storage system (ESS). TPRI has already installed two sets of ESS in Xia-xing Power Plant, which not only assist power system operation but also enhance the knowledge and dispatch experience of ESS.
The power type of ESS uses Li battery(2MW/1MWh), which has already been constructed in December 2009. This system provides power system ancillary services and spinning reserve, carries out functions like renewable energy smoothing, frequency-watt control, voltage-var control and frequency deviation-P control. The energy type of ESS uses NaS battery(1.8MW/10.8MWh), which has already been constructed in December 2020. The main purposes are to execute load transformation, adjusting renewable energy generation period, and increasing diesel engine’s dispatch flexibility.
Green Energy Smart Management System of TPRI Sulin branch
The green energy smart management system installed in the Sulin branch of Taiwan Power Research Institute(tpri-EMS) was designed base on micro-grid concept. The tpri-EMS is consists of 8 energy management subsystems, including the photovoltaic storage test site. By 2019, the performance test and verification of all-vanadium redox flow batteries and lithium-ion battery energy storage systems have been completed. In the future, the focus will be on the development of application functions of energy storage systems in microgrids, such as peak shaving, load tracking, automatic demand response, reduction of contract capacity as well as photovoltaic smoothing.
Evaluation of all-vanadium flow battery in renewable energy storage
With an aim to increase the ratio of renewable energy to the total power generation to 20% in 2025, Taiwan Power Company has actively been promoting solar power generation and wind power generation. Taiwan Power Research Institute (TPRI) has conducted energy storage demonstration experiments for smoothing renewable energy generation and controlling peak power demand. To successfully achieve these goals, TPRI has introduced an all vanadium redox flow battery’s energy storage system from Sumitomo Electric Industries Ltd. in May 2016. This 125kW/750kWh system was installed at Shulin branch of TPRI in February 2017. Battery performance test, demand response, renewable energy smoothing, island mode operation, and cost minimization are tested in this system. In addition, a 250kW/400kWh and a 1.MW/1.5MWh container type lithium-ion battery energy storage system from local company has been constructed in this area in 2019.
Demonstration and experimental study of a flywheel energy storage system for long duration applications
Flywheel Energy Storage System (FESS) stores energy by converting the electricity and the spinning kinetic energy with a bidirectional power conversion device. FESS is suitable for use cases that require hundreds of thousands cycles of charge & discharge. The power output ranges from kW to MW within a short period of 1 second
FESS is one of the oldest energy storage mediums. The performance in terms of energy storage density, energy efficiency, power, and response time of the FESS is outstanding. Using mechanical energy for energy storage has advantages of long cycle life, reliable operation and zero impact to the environment. The energy efficiency of the FESS depends on manufacturing materials, electrical machines, types of bearing, and the vacuum chamber housing the rotor. The State of Charge (SOC) of the FESS can be directly calculated by monitoring the rotational speed of the flywheel which effectively improves the reliability of the power management system
In general, most FESSs can provide high power instantaneously with short duration. However, the FESSs providing the long charge and discharge duration for peak shaving and energy shifting is rare. Therefore, a FESS with rated power of 8kW, discharge duration of 4 hours, and 32 kWh energy has been installed by TPRI in TPC in February 2019. The FESS is tested for various technical characteristics, and the reliability and corresponding performance of the specification have been demonstrated for the reference of application in the future.
To respond to domestic renewable energy development and energy management demand, energy storage equipment, installed by consumers, is a great tool which can be used with demand management and participate in ancillary service, is beneficial to improving power system stability.
To meet the demand of domestic energy storage equipment installation, TPC announced guidelines for grid connection of energy storage system on March 6, 2020.