A sudden collapse of the power grid in England and Wales has led to a massive power outage at . London’s busiest station, King’s Cross, was forced to temporarily shut down in an emergency, stranding a large number of passengers; many other citizens were trapped in the subway, and hospitals with insufficient backup power were forced to suspend. In this summer twilight, one million people were in a state of uncertainty.
At 16:52:33.49, a lightning strike caused a short circuit in the line of a substation, which was quickly cleared but led to the first off-grid of the distributed power supply and the weakening of the main power grid.
16:52:33.728 seconds, located in the North Sea, the world’s largest Hornsea Horn offshore wind power station, there is a significant drop in wind power output. As the UK has been vigorously promoting clean energy, 40% of the country’s electricity relies on wind and photovoltaic power generation, and the Achilles heel of these new energy sources, is not stable enough.
At 16:52:34-53:58, a series of outages occurred at the steam unit of the Little Barford Power Station, and the distributed power supply off-grid expanded in size. Since then, the triple stack of distributed power sources, Horn wind farm and Little Barford steam units that went off-grid due to lightning strikes resulted in a loss of 6.5% of the total load on the grid, a significant drop in frequency and the start of power outages in many areas.
Analysis of the incident indicates that it was a grid collapse due to a high percentage of clean energy (wind power) connected to the grid and insufficient power system backup. The large amount of new energy generation replacing traditional energy generation led to a reduction in the power system’s ability to withstand the power differential. In the event of successive disturbances in the power system, the system backup was insufficient to make up the power shortfall in time, leading to the accident.
In the end, it was fortunate that the pumped storage unit was able to increase its output in time to prevent further expansion of the accident, thus showing the importance of energy storage for high percentage of new energy sources when connected to the grid.
Both wind power and photovoltaics are very dependent on the weather itself. For example, PV tends to peak at noon, and at night there is no electricity available, but at night is exactly the peak of electricity consumption, so other energy sources have to be used to regulate the peak, which is a great load on the grid.
Under China’s big goal of carbon neutrality, the National Energy Administration has given a plan to rapidly boost clean energy such as photovoltaic and wind power, which requires large-scale and systematic energy storage support. Currently the most traditional means of energy storage in the world is pumped storage, while in the new energy storage, electrochemical energy storage is growing at an alarming rate.
Today’s in-depth analysis is the third article in the “Carbon Neutral” Science and Technology Hub, where we will focus on new energy storage, with a focus on electrochemical energy storage. We will first summarize what energy storage methods are available, and what are their technical iteration potential and market incremental space? Under the trend of increasing the proportion of new energy generation, what scenarios can different energy storage methods meet? And the economic analysis of energy storage, who pays for energy storage?
1、Why is energy storage exploding?
To understand why energy storage is exploding, you need to understand the grid first.
The speed of electricity is very fast, transmitted at the speed of light, so the generation, transmission and distribution of electricity need to be completed in an instantaneous synchronization, and the whole power system is in a dynamic balance at all times. When the grid is in normal operation, the active power generated by the generator and the active power consumed by the load are in balance, and the frequency of the whole system is maintained at the rated value.
When the power supply power is greater than the load power, the system frequency increases, and vice versa, it decreases. Therefore, the grid needs to ensure that the frequency is within a reasonable range by means of primary frequency regulation and secondary frequency regulation, otherwise a frequency collapse will occur, resulting in a large area blackout, just like that accident in the UK 2019 blackout at the beginning of this article.
But wind power, photovoltaic and other new energy, a fatal weakness is a strong intermittency and volatility. For wind power, what if the wind becomes weak at a certain time, or even no wind? For photovoltaic, what if it rains a lot in a month, no sun? And generally the light is strongest at noon and weakest at night, and its power generation is also fluctuating.
This instability is a nightmare for the grid and must be regulated by other means. This new energy supply, such as wind power daily fluctuations of up to 80% of installed capacity, will make the entire grid becomes vulnerable, if extreme weather, the risk of grid collapse, which has happened in the United States and Europe, so that wind power and photovoltaic was once called “garbage power” by the power people.
In this high volatility, if there is no energy storage, like Qinghai, Inner Mongolia and other places of scenic power, in the case of sufficient light or wind, generate a lot of electricity but can not use up, it faces a very high rate of abandoned light, abandoned wind.
The International Energy Agency (IEA) has given a guideline that divides the proportion of intermittent renewable energy (wind and PV) to be absorbed by the grid into four stages.
Phase I: below 3%, basically no impact on grid operation.
Stage 2: Between 3%-15%, the impact on the grid is smaller, and the volatility and intermittency can be smoothed out by forecasting intermittent renewable energy unit generation and by strengthening dispatch.
The third stage: between 15%-25%, the impact on the grid is larger, when the grid flexibility requirements are greatly increased, the need to increase the frequency regulation power station in the short term, the medium and long-term need to introduce energy storage.
Stage 4: Between 25% and 50%, grid stability is challenged, with 100% of the power supplied by intermittent renewables for some hours, and all power plants must be configured to operate flexibly with energy storage to cope with random variations on the power and load side.
To use an analogy, the power grid is like a big river, if only 1-2 small tributaries into the time, the overall water flow on the big and not too big impact on the water Minaziff also not too big impact, but when more and more tributaries, and sometimes some tributaries have water, sometimes no water, the main river water level changes greatly, it is necessary to regulate. When the proportion of new energy exceeds 15%, the use of energy storage technology to “cut the peak and fill the valley”, it is imperative.
Especially in the case of an increasing proportion of electric vehicles, the number of charging posts will also grow at a high rate, and the impact on the large power grid at the peak of charging will be relatively large. Equipped with a buffer storage system like a reservoir, it is also one of the main driving forces for the development of domestic energy storage business, which is closely related to the ownership of electric vehicles.
The big explosion of domestic energy storage comes from policy changes. In the context of carbon neutrality and improving energy self-sufficiency, the National Energy Board in the “Notice on Matters Relating to the Development and Construction of Wind Power and Photovoltaic Power Generation in 2021”, plans to reach a total installed capacity of 1.2 billion kilowatts of wind power and photovoltaic in 2030, and as of the end of 2020, the total scenery is only 630 million kilowatts, this goal means that in the next 10 years, wind power and photovoltaic to add 300 million kilowatts each.
For the supporting energy storage industry, since 2020 there has been an intensive policy, especially in 2021 so far there are many specific landing policies issued, including mandatory PV, wind power with storage policy, requiring new installations must be configured with 15% to 20% of energy storage. This ratio is calculated based on the PV power plant at night power curve down, or wind weakening, but also continue to ensure 2 hours of power input.
According to the estimation of the national grid, before 2035, the installed capacity of wind and light will reach 700 million and 650 million kilowatts respectively, and the maximum daily fluctuation rate of wind and solar energy is expected to reach 156 million and 416 million kilowatts respectively, which greatly exceeds the current regulation capacity. It is urgent to reconstruct the peaking system to have the regulation capacity to cope with the daily power fluctuation of about 500 million kilowatts of new energy.
On the one hand, energy storage can solve the mismatch between power generation and electricity consumption load during peak and valley hours by cutting peaks and filling valleys; on the other hand, it can participate in providing power auxiliary services to solve the instability of the grid caused by the volatility of scenery power generation. In addition, the flexible configuration of energy storage system can also increase the local consumption of electricity and reduce the construction cost of transmission system.
Taken together, mandatory distribution and storage will become an explosive growth point on the short-term generation side. On the grid side and power side, policy-driven demand for energy storage will also steadily advance, with peak and valley tariffs and local subsidies, etc., all contributing positively to industrial and residential energy storage.
Second, what are the new energy storage methods?
Due to the ready-to-use nature of electricity, energy storage is the conversion of electrical energy into other forms of energy, through physical or chemical media.
So there are various ways of energy storage, the main ones include pumped storage, electrochemical energy storage, compressed air energy storage, flywheel energy storage, molten salt energy storage, electromagnetic energy storage, hydrogen energy storage and so on.
The oldest and most technically mature form of energy storage is pumped energy storage. It is actually very simple: excess electricity is fed into the pumping resistance and the water level is pumped to a high level using the difference between the height of the dam. When electricity is needed, then open the gates and release the water to generate electricity. The amount of electricity it can store is very large.
From 2000 to 2020, pumped storage accounts for 90% of the cumulative global installed capacity. The key reason why it accounts for such a large proportion is its economics. Although the investment in pumped storage is very large, generally 3 billion to 5 billion to start with, and also takes 5 to 8 years to build, equivalent to the construction of a small reservoir, but its life cycle far exceeds other storage methods, up to 50 to 60 years of application period, and the discharge of pumped storage are gigawatt-hour level, can achieve long-time energy storage and 4 hours to 7 hours of discharge, the overall cost of the most economic.
But pumped storage has a fatal weakness – it must find the right water resources and geographical structure, and many provinces and cities do not have the appropriate conditions if they want to lay out systematically.
When the proportion of new energy on the grid is relatively low, the use of low-cost pumped storage for thermal power is a very good solution, but when the proportion of new energy exceeds 15%, a solution with flexible site selection, lower individual input costs, shorter construction cycle and good economics is needed.
Among all the new energy storage solutions, the brightest star is electrochemical energy storage, which is also one of our most promising energy storage methods, and we will analyze it in detail in the next section. In addition to electrochemical, we will first briefly introduce several new energy storage options that are not yet commercially available on a large scale, and some are still in the experimental stage.
Compressed air energy storage: The volume is still very small, and its working logic is to compress the air to high pressure with excess electricity and store it in the storage chamber during the low period of electricity consumption, that is, to convert electricity into air internal energy and store it. When electricity is needed, high pressure air is released from the storage chamber into the combustion chamber, which is heated up by fuel combustion to drive the gas turbine to generate electricity. In practice, in order to save the construction cost of the storage chamber, it is often to find a mine cave to use as a natural storage chamber, which can also be limited by the geographical structure. The energy efficiency of compressed air is relatively low, at 65-75%. By the end of 2021, compressed air energy storage accounted for 2.3% of the global installed capacity of new energy storage, and commercial promotion is currently relatively small.