China's power storage industry is experiencing rapid growth as the country continues to move toward a more sustainable energy mix, with renewables taking up an increasing share.
Energy storage is the process of retaining energy in a system for later use. This can be accomplished through various methods such as batteries, pumped hydro, and other means. Energy storage systems play a crucial role in ensuring the reliability and stability of energy supply, especially in renewable energy systems.
Take Hebei-based Fengning Pumped Storage Power Station for example. It has the largest installed capacity in the world. Since 2021, seven units have been put into operation, which generated a total of 1.4 billion kilowatt-hours of green power. Based on the monthly power consumption of roughly 250 kWh per household, this amount of electricity can supply power for nearly 500,000 households for a year.
In the past, fossil fuels like coal were virtually the only source of electricity, and many grid operators did not store energy because it could be an expensive undertaking. Instead, grid operators had dispatch centers that consistently managed supply to meet demand, and would burn additional coal to ramp up power generation during peak hours.
However, as concerns about climate change and resource depletion grew, the focus of power generation is gradually shifting towards renewable energy resources such as solar and wind. The problem with these modalities is that they are intermittent and not always available when needed. That's easy to understand. Wind is not stable and sunlight is unavailable after dark, making it extremely difficult to manage power supply.
That's why energy storage becomes important. It helps bridge this gap by retaining energy when it is available and releasing it when needed.
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"Differing from fossil fuels, new energy power generation has higher requirements for the safe and stable operation of power systems. That's because most new energies are intermittent resources, which undergo sudden and random fluctuations. This makes it difficult to realize stable and steady power generation. In addition, it presents challenges to grid stability, such as voltage fluctuations, during power transmission," said Lin Boqiang, head of the China Institute for Studies in Energy Policy at Xiamen University in Fujian province.
There are various forms of energy storage systems, each with its own advantages and disadvantages. Some of the most common forms include lithium-ion batteries, which are widely used in consumer electronics and electric vehicles, and pumped storage hydropower, which is currently the major means of storing massive power generated from solar and wind.
Pumped storage facilities have two water reservoirs at different elevations. The facility pumps water from the lower reservoir to the upper reservoir when there is excess power on the grid, and releases water to let it flow back downhill to generate power when there is greater demand for electricity.
The total installed capacity of pumped storage hydropower in China increased 15.6 percent year-on-year to 36.39 million kW by the end of 2021, ranking tops in the world, according to the China Renewable Energy Engineering Institute.
According to estimates from the institute, total installed capacity of pumped storage hydropower will reach 62 million kilowatts in China by 2025.
