Long term energy storage-definition, benefits and forecast growth speed

What is long term energy storage

Long term energy storage generally refers to the technology of energy storage for more than 4 hours. Long term energy storage system is an energy storage system that can realize cross day, cross month, and even cross season charging and discharging cycles to meet the long term stability of the power system.

The higher the penetration rate of renewable energy generation, the longer the energy storage time is required. Renewable energy power generation is intermittent. The main power generation periods and peak power consumption periods are misaligned, and there is a gap between supply and demand. With the increase of permeability, the load requirement of balancing power system increases.

What’s the essence of long term energy storage and why do we add energy storage devices

Like the core of energy storage, the core of long term energy storage is to realize the movement of energy in time and space, which essentially makes the energy more controllable. By normalizing the essence of various power generation modes, we can find that thermal power, nuclear power and biomass power generation naturally have corresponding media for energy storage.

The media are suitable for storage and transportation, that is, they are configured with long term energy storage function. For hydropower generation, wind power generation, photothermal power generation and photovoltaic power generation, the sources of power generation are instantaneous, non storable and non transportable. 

Accordingly, if we want to make these energies more controllable, we must artificially add long term energy storage devices. It can be understood that the addition of long term energy storage devices will make water power, wind power, photovoltaic and photothermal power generation more ideal.

Long term energy storage vs short term energy storage-what’s the benefits

Compared with short term energy storage, long term energy storage system can better realize power translation, transfer the power of renewable energy generation system to the peak time of power demand, and play the role of balancing the power system and large-scale power storage.

The function of peak shaving and valley filling of energy storage products is prominent, and the long term energy storage equipment represented by 4h is necessary for development. According to the data, the long term energy storage equipment stores electric energy at high power during the day, and discharges at high power during the peak of power consumption at night, with the peak discharge duration exceeding 4h.

The research report shows that by 2045, solar energy will become the most important renewable energy in California, accounting for 75%. In order to balance solar power generation, it is necessary to store 8 to 12 hours of electric energy in the daytime, and the amount of storage and scheduling in the evening will also increase. At most, it needs to discharge continuously for 12 hours, so the development of long term energy storage is indispensable.

Due to the high proportion of renewable energy generation, California is one of the first places to deploy a large number of long term energy storage systems with a continuous discharge time of 4 hours.

Since 2019, California has begun to deploy 4-hour long term energy storage system in succession. According to the prediction, California will deploy 2-11GW of long term energy storage equipment by 2030 and 45-55GW of long term energy storage equipment by 2045.

How to evaluate the rhythm of building pumped storage and new long term energy storage

The generation side and the grid side have been undertaking the task of making energy more controllable, and long term energy storage will be used as a way to provide flexible resources. Before the large-scale construction of pumped storage and the rise of new long term energy storage, more flexible resources of the power grid need to be provided by thermal power.

At present, in the presence of a high-quality power grid, the flexible regulation resources of long term energy storage system are jointly provided by pumped storage, new energy storage, thermal power, etc. At this time, the rhythm of building pumped storage and new long term energy storage should be evaluated in two aspects:

● Economic dimension

From the perspective of economy, we need to consider which is the best: the construction of pumped storage, the construction of new energy storage or the thermal power flexibility transformation;

● Demand dimension

From the perspective of demand, thermal power flexibility transformation has constraints on the number of units in stock, and pumped storage has constraints on geographical resources.

The propulsion of long-term energy storage is divided into three stages

For long term energy storage, the most important thing is to provide support for flexible regulation of power system. The flexibility of power system mainly comes from two aspects, one is the flexible power generation of the original generator set, the other is the configuration of energy storage facilities. When analyzing the pace of advancement, the flexibility provider can be simplified into three parts:

● Stock units;
● Mature energy storage mode – pumped storage;
● New energy storage technology.

In this way, we can roughly outline the pace of energy storage with the gradual increase of the proportion of wind power generation. It can be divided into three stages.

The first stage-about 10% of wind power generation

The strategic window period for the development of new long term energy storage technology. At this stage, the existing generator sets (coal power, gas power) can be transformed to provide more flexible resource support.

Because of the long construction period (6-8 years) of traditional energy storage, pumped storage needs to be planned as soon as possible; The cost of new energy storage projects is still too high, but if there is still a flexibility gap, new energy storage projects need to be made up as soon as possible.

The second stage-about 20% of wind power generation

The decisive period for the industrialization of new long term energy storage technology to reduce costs is at this stage, and the transformation of existing generator sets is basically completed, which cannot provide more incremental flexibility.

Pumped storage projects have been gradually completed, becoming the main force for flexible regulation together with the existing units; At this time, the demand for new energy storage is further enhanced.

The third stage-about 30% of wind power generation

During the period of rapid growth of the installed capacity of long term energy storage technology with optimal cost, there is no room for improvement and the stock units are phased out; Pumped storage cannot continue to increase due to geographical resource constraints; Only new long term energy storage technology can provide incremental flexibility resources.

Prediction of the future development of long term energy storage in the world

Geographically, the development of long term energy storage is fast in European and American countries, followed by China. In Europe and the United States, represented by California, Germany and southern Australia, the proportion of wind power generation is already high, and the demand for long term energy storage is becoming increasingly urgent.

Considering the economy of various new types of energy storage, they more choose to configure lithium battery energy storage system. China’s lithium energy storage battery manufacturers, represented by CATL and SUNGROW, is occupying a global share.

In China, It is estimated that the proportion of wind power generation in China will increase from 9.5% to 16.4% from 2020 to 2025. According to the target, by 2025, the annual power generation of renewable energy will reach 3.3 trillion kWh, the proportion of the increment of renewable energy power generation in the increment of power consumption in the whole society will exceed 50%.

And the weight of the total consumption responsibility of renewable energy power in China will reach about 33%; The wind power and solar power generation will double, and the non hydropower consumption responsibility weight of renewable energy power will reach about 18% by 2025.

Assuming that:

● The annual utilization hours of thermal power decreased from 4290 hours in 2020 to 4000 hours;
● The proportion of gas, other thermal power and biomass power generation in 2025 will be consistent with that in 2020;
● Water and electricity utilization hours remain unchanged;
● The average annual increase of wind power is 50GW, and the utilization hours are increased to 1700 hours;
● The average annual increase of PV is 90GW, and the utilization hours are increased to 1050 hours.

Under this assumption, China’s goals can be met. According to this hypothetical scenario, from 2020 to 2025, the proportion of wind power generation in China will increase from 9.5% to 16.4%.

New long-term energy storage will gradually become the main force

Thermal power transformation and pumped storage are the main force of flexibility increment, which provides a strategic window period for the accelerated development of new long term energy storage.

Taking China as an example, under the current circumstances, on the one hand, there are a number of units that can be retrofitted to increase flexibility; On the one hand, China has a part of pumped storage resources reserve.

Different unit characteristics, transformation objectives, fuel characteristics and other conditions will bring huge differences in transformation investment. Generally, the investment is calculated at 30~90 yuan/kw, which is the cheapest flexible adjustment resource. The second is pumped storage, followed by a new type of energy storage represented by lithium ion battery.

According to the analysis, China will complete the flexibility transformation of 200 million dry watts of coal storage motor units, increase the system regulation capacity by 30 million to 40 million kilowatts, and add 150 million dry watts of coal power units with flexible regulation capacity.

By 2025, the installed capacity of new energy storage will reach more than 30 million dry watts; The pumped storage capacity will reach more than 62 million kilowatts in 2025 and about 120 million dry watts in 2030. And the new long term energy storage will gradually become the main force of flexible regulation after 2025.