The news of a fire at an energy storage station in Zhenjiang brought attention once again to the issue of energy storage safety. How do we guarantee the safety of storage systems? How can the developing storage industry maintain a reasonable balance between cost and safety? China Electric Power News sat down with China Energy Storage Alliance Vice Chairman Johnson Yu to discuss these questions. CNESA has provided a summary of the content below:
Current Domestic Energy Storage Safety Situation
Energy storage is still an emerging industry in China. The industry got its start relatively late in China in comparison to other countries, and domestic projects are still few. The coexistence of numerous technologies, each with their own unique safety needs, has meant that industry regulations, standards, and verification practices are still lacking. Therefore, performing strict evaluations of energy storage systems remains difficult, and irregularity between systems exists. Such conditions can lead to a number of hidden dangers.
Causes of Energy Storage System Accidents
At present, the major cause of accidents is the combination of Li-ion battery flammability with thermal runaway. However, the source of the accident is usually not the battery cell itself, but an electrical accident. Safety is a complicated issue, and it is not possible to trace the cause of an accident back simply to the choice of battery or battery cell. The supporting system is equally important. However, many peripheral system components and measures surrounding battery cells currently lack proper safety standards, such as the designs of battery management systems, energy management systems, and system containers, as well as emergency handling procedures, choice of insulation materials, and fire extinguishment methods.
In addition, safety issues will differ based on technology. Because Li-ion batteries rely on an organic electrolyte solution, they are susceptible to thermal runaway and combustion. Lead-acid and flow batteries will not combust, but this does not mean that these technologies are not susceptible to other electrical accidents. Last year’s newly constructed energy storage capacity totaled 127 MW. Lead-carbon, Li-ion, and flow battery technologies each made up part of this capacity, and each technology has its own different level of developmental maturity, attributes, and system needs. Accidents also have their own degree of randomness, and it is impossible to have a complete evaluation method for one individual system. The problem also cannot be solved by simply eliminating the use of a certain technology or battery cell to prevent accidents from occurring.
It is also difficult to compare the probability of accident occurrence due to the wide variety of settings for energy storage applications. For example, grid-side storage and behind-the-meter storage, open air deployment and indoor deployment—such variations each have their own standardization needs. Energy storage for grid frequency regulation requires the use of high frequencies and heavy electric current for charge and discharge, requirements that are much higher than that needed for behind-the-meter systems. However, that does not mean we can say that grid-side systems are inherently less safe than behind-the-meter systems. Many other factors are at play, such as the design requirements of each system, control strategies, operating regulations, etc.
The Effects of the Zhenjiang Fire on the Domestic Energy Storage Industry
Energy storage projects in China that have experienced fires are those that are innovative and exploratory, though are the types of projects that would be considered already mature in many other countries. Safety issues can be resolved through engineering techniques, and it is unlikely that safety issues will cause a panic within the public, though it is imperative that industry players still place system safety as a priority.
Most of the accidents that have occurred have been due to a lack of strictness regarding technological thresholds and safety measures. Another factor is that cost restrictions can lead to a lowering of requirements for safety. One of the industry’s major challenges is guaranteeing system safety while still preserving technology costs that are reasonable.
Suggestions for Improving the Safety of China’s Energy Storage Systems
China’s energy storage safety standards and related regulations still have a lot of catching up to do. Whenever an accident happens, it is crucial that we determine its true cause so that proper measures for dealing with the problem can be enacted. Updating and improving standards will require regulators to put greater effort into research and reform. Proper verification or certification of projects before they are implemented should also not be taken lightly.
Though China has taken greater consideration to safety issues in recent years, more attention has been paid to technological choices. In the long term, we should encourage more safe technologies to enter the market, such as solid-state batteries. Yet in the short- and medium-term, improving system safety will require considering the entire system design, analyzing the cause and site of accidents and taking the proper measures to prevent them. We also must of course ensure that proper measures are in place to maintain the safety of the public and our utilities.
Globally, Li-ion batteries are widespread, particularly in electric vehicles, and their qualities are well-known in the industry. Most new energy storage projects rely on Li-ion batteries. In the past year, projects in China, South Korea, and Belgium have all had fires, though mainstream Li-ion battery manufacturers in the European and American markets maintain a low accident rate. Some projects have seen continued safe use for over eight years. Much of the valuable experience accumulated in other countries has lent itself to the creation of standards and regulations. What this means is that though Li-ion batteries still carry the risk of flammability and thermal runaway, with proper and strict management, safety of such systems can be maintained. Increasing safety measures is not only a necessity, it will also help our industry develop in a healthy direction.
Originally published in China Electric Power News, 2018-9-27
Reporter: Deng Huiping Translation: George Dudley