【Haichuan Chemical Accident Updates】Fire at energy storage container at photovoltaic power plant in Corsica, France

The essence of an energy storage station is lithium batteries, which are quite dangerous!

In March 2019, a severe fire broke out at a photovoltaic power plant in the north; thick smoke filled the premises of the plant, and the fire was not extinguished in time, causing heavy damage to the facility. On June 9, 2019, a building at a school in Bung Kan Yang Province caught fire. The fire started when the solar panels on the roof of the building ignited; the flames spread throughout the entire building. Fortunately, no injuries were reported. On August 21, 2019, foreign media reported that Walmart claimed in a new lawsuit filed in the New York State Supreme Court that defective Tesla solar panels caused fires at at least 7 Walmart stores, resulting in losses of hundreds of thousands of dollars. However, even hydroelectric photovoltaic power plants were not spared. On September 9, 2019, the largest water-based solar panel facility in Japan, located in Ichihara City, Chiba Prefecture, caught fire suddenly. Firefighters concluded that the cause of the fire might have been strong winds brought about by Typhoon Faxai; these winds caused the panels to topple over and pile up on those that remained upright, and the overheating resulting from this pile-up led to the fire.

One of the causes of fires in photovoltaic power plants is the hot spot effect of the modules: under certain conditions, the solar cell modules that are shaded in a series circuit act as a load, consuming the energy generated by the other solar cell modules that are exposed to light; as a result, these shaded solar cell modules heat up. According to statistics, 40% of fires in photovoltaic power plants are caused by direct current arcs. There are thousands of connections in such systems, and if even one of these connections becomes loose, it can lead to a direct current arc; once an arc is formed, it can trigger a fire. This necessitates that power plants adhere strictly to design standards and specifications to ensure the quality of construction. Construction quality also affects the subsequent operation and maintenance of the power plant. Given the extreme complexity of the wiring in photovoltaic power plant systems, it is very difficult to carry out maintenance tasks solely relying on human effort. The emergence of intelligent photovoltaic systems is helping to address this issue; such systems enable real-time monitoring of the power plant, which facilitates timely troubleshooting by maintenance personnel and helps reduce losses for the plant. In addition to photovoltaic power plants, fires have also occurred in photovoltaic enterprises: in September 2019, an explosion took place at Runxiang Technology Company in Wuxing District, Huzhou, with materials such as sponges and alcohol catching fire. On March 8, 2020, a fire broke out in the purification workshop of Changzhou Sailan Photovoltaic Technology Company. The preliminary investigation into the cause of the fire indicated that it resulted from molten iron coming into contact with water after the newly installed furnace lining was damaged during boiler testing. Some netizens expressed relief that the high-temperature siliceous water melted the boiler, turning the water used for cooling into steam instantly. When this steam came into contact with the electric heating elements, it was electrolyzed into hydrogen and oxygen, which can easily lead to explosions; fortunately, only a fire broke out. In recent years, photovoltaic companies, especially those involved in silicon wafer processing, are prone to accidents. Flammable silicon powder is processed in high-temperature ingot furnaces, and the slightest carelessness can easily lead to fires or even explosions. To minimize unnecessary losses, it is necessary for enterprises to choose mature manufacturing processes and equipment, to keep the production facilities dry, and to continuously raise employees’ awareness of safety, so as to avoid irreversible consequences resulting from carelessness.

A direct current arc is a type of gas discharge phenomenon, which can be understood as a high-intensity instantaneous current that occurs under insulating conditions. According to literature reports, when the current is interrupted by a electrical switch or there is poor contact, and if the circuit voltage is at least 20 volts and the current is 80–100 mA or more, a direct current arc will be generated between the contacts of the electrical appliance. Unlike alternating current arcs, direct current arcs do not have a zero crossing point, which means that if a direct current arc is formed, the ignition site will remain burning steadily for a considerable length of time without going out. In photovoltaic power plants, loose cable connections can lead to poor contact ； Reliability of connectors or direct switches ； Prolonged aging of the insulating layer, as well as issues such as damage to the insulating layer caused by external forces, can all lead to direct current arcing. As the plant operates for longer periods, the probability of DC arcing also increases. The high temperature generated by a direct current arc easily exceeds 3000°C, which can directly cause a fire. Based on domestic and international cases and data, direct current arcs have clearly become the leading cause of fires in power plants.