Carbon dioxide energy storage, the "new quality productivity" in the energy storage industry

• Carbon dioxide energy storage technology has become one of the key technologies to solve the challenge of large-scale grid connection of renewable energy, and can meet the requirements of “long-term energy storage”, “safety and environmental protection” and “rapid implementation”.

• As a technology company that emerged from the Technical Institute of Physics and Chemistry of the Chinese Academy of Sciences, Bo Rui Dingneng has not only successfully achieved the efficient utilization of carbon dioxide with its original "new type of carbon dioxide energy storage" solution, but also promoted the scale-up, standardization and commercialization of related technologies.

00 Introduction

At the just-concluded National People's Congress and the Chinese People's Political Consultative Conference, "new quality productivity" became the undisputed high-frequency word and was listed as the first of the top ten work tasks for 2024.

New quality productivity, different from traditional productivity, is a "qualitative leap" in productivity.

Looking back at the evolution of human production methods, from the hunting era to the farming era, and from the three industrial revolutions of mechanization, electrification, and informatization, energy transformation has played an extremely important role.

Currently, the global power industry is in a critical period of transition from "fossil energy" to "renewable energy". However, new challenges have emerged - the randomness, intermittency and volatility of renewable energy represented by "wind power and solar energy" have caused huge structural pressure on the existing power generation system.

A new energy storage technology that can meet the requirements of "large capacity and long time" is imminent.

At this year's "Two Sessions", Zhang Zhentao, a member of the National Committee of the Chinese People's Political Consultative Conference and a researcher at the Technical Institute of Physics and Chemistry of the Chinese Academy of Sciences, said: "Carbon dioxide compression energy storage and air compression energy storage are one of the best new energy storage technologies to solve the problem of large-scale renewable energy power generation and grid connection. It is recommended to give non-discriminatory policies to new long-term physical energy storage technologies, and truly support the development of new quality productivity with practical actions."

What kind of technology is the "carbon dioxide energy storage" mentioned by Zhang Zhentao? And how can it be commercialized on a large scale?

01New long-term energy storage technology takes the stage

In 1746, Professor Masonbrock of Leiden University in the Netherlands used two pieces of metal foil and a piece of glass to form a capacitor, which was the earliest electricity storage device in human history - the "Leyden jar". At that time, the "Leyden jar" could only store "limited" charges; today, people are beginning to look for a "Leyden jar" that can store huge amounts of electrical energy.

The first to come into the public eye are wind power and photovoltaic energy storage. Over the years, my country's total installed capacity of wind power and photovoltaics has grown rapidly, ranking first in the world for many consecutive years. However, due to the instability of wind and solar power generation, as well as the difference between wind and solar power generation curves and power consumption curves, peak regulation has become increasingly difficult, which in turn affects wind and solar power consumption.

We can also get a glimpse of this from the data. According to incomplete statistics from China Energy News, as of July 2023, within a year, Shanxi, Shaanxi, Anhui, Jiangxi, Hebei and other places have successively announced the latest list of wind and solar project cancellations, and the total installed capacity of the projects to be cancelled has exceeded 10 million kilowatts.

On the one hand, there is a shortage of energy; on the other hand, there is an “overcapacity” of production capacity due to a rush of investment... How can the contradiction behind this be reconciled?

Is it possible to create a huge "Leyden jar" to store the wind and solar power that cannot be consumed, and discharge it during peak electricity consumption, which can not only effectively regulate the supply and demand of the power grid, but also improve the operating efficiency of the power system, while achieving green and low-carbon development?

As a result, "new energy storage" has entered the historical stage. But in the face of the "hundred flowers blooming" of new technologies, who can take on this important task?

The first condition is to be able to meet the requirement of “long-term energy storage”.

For a long time, there has been a misunderstanding outside the industry that increasing energy storage can solve more than 95% of the problem of wind and solar power absorption.

This view is very one-sided. For example, if you want to store 3 tons of water at one time, would you choose a "mineral water bottle" or a swimming pool?

By the same token, if you want to absorb the huge amount of wind and solar power generation, no matter how many "mineral water bottles" - "short-term energy storage" you use, it will not be enough.

According to the charging and discharging time, energy storage technology in China is generally divided into "short-term energy storage" (<4 hours) and "long-term energy storage" (≥4 hours).

Long-term energy storage - represented by pumped storage, compressed air storage, carbon dioxide storage, and flow batteries;

Short-term energy storage - represented by lithium-ion batteries, lead-acid batteries, sodium-sulfur batteries, and supercapacitors.

We can imagine "short-term energy storage" as a mini "power bank", which is flexible, can be used for emergencies, and can also meet the hourly peak and frequency regulation needs. However, due to its limited capacity, the system will quickly become saturated when charging.

"Long-term energy storage" is more like an "outdoor power source" for camping. It has a large energy storage capacity and plays a role of "shifting the universe" in the absorption of wind and solar power. It can realize charging and discharging cycles across days, months, and even seasons, and meet the increased load needs of new power systems.

If you want to absorb the huge amount of wind and solar power generation, the miniature "short-term energy storage" is obviously not enough. The large-scale "long-term energy storage" can "swallow" it and is suitable for scenarios such as long-term grid peak regulation and renewable energy grid connection.

Moreover, from the perspective of the long-term path of "dual carbon", the later the time comes, the more "long-term energy storage" will be needed. It is predicted that when wind and solar power generation accounts for 50%-80% of the power system, the energy storage time will need to be more than 10 hours.

The second condition is to meet the requirements of “safety and environmental protection”.

Energy storage technologies can be roughly divided into two categories: electrochemical energy storage and physical energy storage . The maturity of different technologies varies:

In electrochemical energy storage, lithium-ion battery technology is the most mature and has become the mainstream of global electrical energy storage; liquid flow batteries represented by vanadium batteries developed relatively late.

In physical energy storage, in addition to traditional pumped storage, compressed air energy storage is the most mature, and many demonstration projects have been implemented across the country.

Although currently, lithium-ion batteries have become the undisputed "king" of the energy storage market with a market share of over 90%, taking the lead for the electrochemical energy storage route.

But the safety issues behind it cannot be ignored - between 2011 and 2021, a total of 32 fire and explosion accidents in energy storage power stations were reported worldwide, 25 of which were related to lithium-ion batteries.

On the one hand, the battery system has inherent defects, and overcharging can easily cause internal short circuits. On the other hand, energy storage devices are mostly installed in remote areas, such as deserts, mountains, and seaside areas. The temperature difference between day and night causes repeated condensation and absorbs dust, which in turn damages the insulation layer of the grounded part and causes fires.

Although we can try to avoid tragedies by improving safety standards, in essence, the "safety" of lithium-ion batteries is only "relative".

Because the organic electrolyte used in lithium-ion batteries does not have the ability to reversibly decompose and restore, when the battery is repeatedly charged or subjected to external forces, lithium ions will precipitate on the surface of the negative electrode and irreversibly form solid metal lithium. Metallic lithium is the culprit for lithium battery safety problems. These problems will be more serious in large-capacity power batteries , and even the use of BMS (battery management system) cannot fundamentally solve them.

Let's look at liquid flow batteries represented by vanadium batteries. Although they can be "safe", similar to lithium-ion batteries, their raw materials involve chemical pollution and electrochemical safety issues. More importantly, the initial installation cost of the system is still high. The amount of electrolyte used is large, and the recycling and processing chain will be long and complicated after the energy storage system is retired.

Therefore, the physical energy storage route that meets the requirements of "large-scale, long-term, safe, and environmentally friendly" has obvious advantages.