It is an inevitable trend that energy storage technology will see a major development

It is an inevitable trend that energy storage technology will see a major development. Electricity is at the heart of modern energy, which used to be a 'source-grid-load' structure consisting of the generation side, the grid side and the consumer side. With the trend towards cleaner electricity under the guidance of "carbon neutrality", it will gradually become a "source-grid-load-storage" structure, with energy storage running through the entire power system.

 

 

Why add 'energy storage'?

 

The answer is simple: as the mainstay of clean energy, wind power and photovoltaics are both highly volatile and must rely on energy storage to achieve efficient power generation. With coal, it is up to people to decide how much coal to use, and controlling the amount of coal used can largely eliminate volatility.

 

With wind and photovoltaics, wind and light are determined by God and volatility is inevitable, so energy storage at different time scales is required.

 

 

Wind power and photovoltaic in different time scale volatility energy storage technology has a variety of, we only need to remember 3 points:

 

Pumped storage: current mainstay, the future stable development. Highly restricted by geographical conditions.

 

Electrochemical energy storage: Costs are entering the viability zone and will develop rapidly. Not limited by geographical conditions, flexible and rich in functions.

 

Other energy storage: technology has not yet entered the mature stage, or the scale is small, or less suitable for power storage.

 

I. Pumped storage: The principle of pumped storage is simple:

 

excess electricity is pumped to the mountains, and water is allowed to flow down to generate electricity when there is a shortage.

 

After the pumped storage power station principle was built, people marvelled at the great mountains and rivers of the motherland

 

 

It is the 'invisible hand' of the tariff that is promoting the development of pumped storage: the tariff reform requires that where the peak-to-valley differential exceeds 40%, the differential should be no less than 4:1, which provides pumped storage with room for arbitrage and impetus for development.

 

Pumped storage is, to put it bluntly, the storage of gravitational potential energy. There is also a gravity tower 'brick-moving' type of energy storage that was an eye-opener in the previous paragraph.

 

It is actually a change of carrier from water to concrete blocks, reducing the geographical constraints. Other than that, it has no advantage over pumped storage. I don't think it compares favourably with electrochemical energy storage either.

 

 

From 2000 to 2020, 90.3% of the world's installed capacity will be pumped storage, which is arguably the mainstay of the current, mainstay.

 

 

Not only is it the mainstay currently, but it will also grow rapidly in the future. <The Medium and Long Term Development Plan for Pumped Storage (2021-2035) states that pumped storage capacity will double from the 13th Five-Year Plan to more than 62 million kilowatts by 2025, and double again to around 120 million kilowatts by 2030.

 

Our country is large, so there are many locations suitable for building pumped storage power plants. The advantages of a large land area are reflected in the pumped storage industry to the fullest.

 

Second, electrochemical energy storage: the next baton in the relay race pumped storage cannot meet the further development of wind power and photovoltaics for the following reasons Three:

 

1.The motherland's mountains and rivers are no longer magnificent, and the locations suitable for building pumped storage power stations are always limited.

 

2.Where wind power is strong and PV is strong, pumped storage power stations cannot necessarily be built nearby.

 

3.Smart grids require not only low-frequency energy storage, but also high-frequency energy storage.

 

Let's start with the low-frequency and high-frequency aspects of energy storage. I wrote an article on V2G in 2016, pointing out the auxiliary role of lithium batteries for the grid, both in low-frequency load shifting (Load shifting) and high-frequency load regulation (Regulation) and spinning reverse (Spinning reverse).

 

Pumped hydro power stations can act as load shifting, but not for load frequency regulation and spinning reverse. Further, in a well-established smart grid, electrochemical storage can fully perform all the functions in the diagram below, while pumped storage can only perform a small part of them.

Electrochemical energy storage is more flexible and can be used in a wider range of applications, to name a few:

 

power generation side: grid connection for wind power and photovoltaic power generation (pumped storage is not always possible due to geographical constraints)

 

grid side: auxiliary peaking and frequency regulation to prevent large-scale blackouts (pumped storage cannot do this) user side: self-generation and storage of photovoltaic (pumped storage cannot be built at home)

 

electrochemical energy storage has good prospects for development, but has been slow to develop. The reason is that batteries are too expensive! Batteries are too expensive,

 

so they are built to lose money → no one builds them because they lose money ...... This is another "chicken begets egg, egg begets chicken" cycle, who will break it? 

 

The rapid development of electric vehicles has led to the cost of lithium-ion batteries falling at an incredible rate: from 2010-2020, the price of lithium battery packs fell steadily, by an average of 19.4% per year.

 

Little did you know, didn't you, that you thought you were just buying an electric car, that you were also driving the development of electrochemical energy storage from a battery cost perspective and indirectly driving the development of photovoltaic and wind power generation?

 

When the cost of lithium batteries is reduced to a threshold, its explosion is inevitable: electrochemical energy storage has become the mainstay of the new installed structure from 2016-2020.

 

 

There are also many kinds of electrochemical energy storage, both lead-acid batteries and lithium-ion batteries (ternary lithium or lithium iron phosphate) that we usually hear about, as well as sodium-ion batteries that we have heard of but not yet seen, and liquid flow batteries and sodium-sulfur batteries that we have not even heard of.

 

CITIC Securities compares them as follows

 

 

TUV Rheinland of Germany compares them as follows.

 

 

In summary there are several key points:

 

lead-acid batteries: the lowest cost in daily life, but used in energy storage scenarios due to their short life span so the cost is not low.

 

Lithium-ion batteries: The current mainstream route (developed by electric vehicles), lithium iron phosphate has an advantage over ternary lithium due to its long life and relatively good safety. There are still some safety technical problems that need to be solved.

 

Sodium ion battery: not dependent on rare resources lithium, safer, lower cost, very promising. However, there is no mass production yet, Ningde Times is catching up with the work, and there is hope that it can be used in cars.

 

 

Liquid flow battery: high safety, long life, large scale, and dominant in energy storage with a length of 4-10 hours.

 

Other batteries: there are liquid metal batteries, multivalent metal cation batteries, water-based batteries and other emerging directions, which are still in the early stages of research.

 

Third, other energy storage other energy storage, either due to the smaller scale, or due to immature technology, or because it is not suitable for wind photovoltaic, and therefore has not yet formed a major trend, here only to do a brief introduction to some of the interesting things.

 

1. Hydrogen energy storage

 

Hydrogen energy storage has one big advantage: the long distance transport of liquid hydrogen is also economical (in the future). As a comparison, pumped storage and gravity bricks can only be regulated in the time dimension, not in the space dimension! 

 

2. Photothermal energy storage Remember the story of Archimedes burning an enemy ship with a mirror?

 

 

Dunhuang also has a 'super mirror power station': a molten salt tower photothermal power station uses 12,000 mirrors to concentrate light on a 260-metre-high heat-absorbing tower to heat and melt stored molten salt for energy storage, and then exothermic at night. It generates 100 megawatts of power and produces 390 million kilowatt-hours of electricity annually.

 

 

As for the advantages and disadvantages, I don't know much about it, so I won't ramble on.

 

 

3. The advantages of compressed air

 

energy storage are large storage capacity, long cycle time, high efficiency and small investment ratio; the disadvantage is that it depends on geographical conditions. Personal understanding is similar to the principle of pumped storage, except that one is the storage of gravitational heat, one is the storage of high-pressure air to do work capacity,

 

 

2021, China completed a number of milestone projects: Shandong Feicheng 10MW salt cavern compressed air energy storage power station, efficiency of 60.7%; Guizhou Bijie 10MW gas collection device storage compressed air energy storage system; Jiangsu Jintan 60MW/300MWh salt cavern compressed air energy storage power station; Zhangjiagang 100MW compressed air energy storage demonstration project.

 

4. flywheel energy storage

 

If pumped storage stores the gravitational potential energy of water, then flywheel energy storage stores the kinetic energy of the rotating body.

 

If water is pumped up, it won't seep down on its own, but the friction will stop the rotating body (otherwise you'd be in a dream world)! One way to reduce this frictional loss is to use magnetic levitation. 2021 saw the launch of a 600kW fully magnetic levitation energy storage device from the Huayang Group for high frequency start-stop scenarios like the Shenzhen Metro.There are also flywheel applications in cars, which I fear are hardly mainstream.

 

Full summary:

 

Pumped storage: current mainstay, future stable development, doubling in 25 years and doubling again in 30 years to 120 million kW. Large geographical constraints, and thus cannot fully support the development of photovoltaic and wind power.

 

Electrochemical energy storage: Costs are entering the viability zone and will develop rapidly. It is not limited by geographical conditions and supports not only low-frequency applications but also high-frequency applications, so it is the main force in supporting both PV and wind power, and also in upgrading the grid from a "source-grid-load" structure to a "source-grid-load-storage" structure.

 

Other energy storage: Technology has not yet reached maturity, or is on a smaller scale, or less suitable for power storage.