Silfab Solar has ceased all production at its solar cell and panel manufacturing site in Fort Mill, South Carolina, after two separate chemical incidents on site. The South Carolina Dept. of Environmental Services (SCDES) requested the shutdown but reiterated that there is “no impact to people, nearby communities or the environment.”
Silfab has not yet begun full capacity production of silicon solar cells at the Fort Mill site but is gathering the necessary chemicals and materials. Silfab alerted York County officials that potassium hydroxide had leaked at the site on March 3. Two days later, the SCDES was alerted to a leak of hydrofluoric acid that was fully contained within the building.
Silfab’s Fort Mill operations have been under scrutiny by concerned residents since it was first announced in 2023. Community members have questioned the safety of the facility, including its “heavy industrial” zoning approval within close proximity to a newly built elementary school. Flint Hill Elementary closed on Thursday and Friday after learning of the two incidents although local environmental organizations said there was no risk.
Greg Basden, Silfab Solar director of operations, talked with local media on Friday to clarify details about the incidents. He stated that the March 3 incident resulted in an accidental release of 300 gallons of water containing a small amount of potassium hydroxide. The chemical was measured at a dilution level of 0.03%.
The potassium hydroxide was captured and contained in Silfab Solar’s stormwater pond, and the 300,000 gallons are being sent to a local zero-waste recycling facility. Basden stated that out of an abundance of caution, crews will remove the soil at the retention pond. “There is no indication the soil was contaminated, nor has any liquid from this leak been detected beyond Silfab’s property,” he said.
As for the March 5 incident, Silfab received a delivery of hydrofluoric acid during the week of February 23, and a minor leak (approximately one drop per hour) was identified. The drip was managed and neutralized, and Silfab is repairing the faulty valve on the tank.
Silfab expressed concern that the hydrofluoric acid drips, which did not require reporting to local officials, were “discovered” by local residents using a drone and trespassing on the property. Basden said these actions “contributed to needlessly alarming the public”
The Fort Mill operations are still paused, and the EPA will begin an investigation today.
Potassium hydroxide is used in silicon solar cell production to etch the cell surface to encourage electricity production. The National Institute for Occupational Safety and Health (NIOSH) states that potassium hydroxide exposure typically happens via inhalation, ingestion or skin/eye contact, which can cause skin and respiratory irritation, skin burns and vomiting. The recommended airborne exposure limit is 2 mg/m3. It is recommended to isolate 150 ft from any liquid spills — approximately one-half of a football field.
Hydrofluoric acid is also used on the surface of a silicon cell, creating textures that maximize light absorption. Skin contact with hydrofluoric acid can result in a rash or burns. A 150-ft isolation zone is also recommended for any liquid spills.
The United States currently has two operational solar cell manufacturing facilities — ES Foundry in Greenwood, South Carolina, and Suniva in Norcross, Georgia. The ES Foundry facility is in an industrial area, while the Suniva plant is in a mixed-use community and within sight distance of a high school. Solar Power World is unaware of community complaints against these sites.
