Warehouse operator takes rooftop solar offline after six fires in fourteen months

What happened

A warehouse operator is reported to have taken rooftop solar offline at all 47 of its North American sites after six fires or arc-flash events between April 2020 and June 2021. A three-alarm fire at a Fresno fulfilment centre on 14 April 2020 damaged 220 modules. A two-alarm fire at Perryville, Maryland, about fourteen months later, drew in around sixty firefighters. By that June every US rooftop array at the operator had been taken offline.

An outside inspection returned one critical finding and 259 major findings, but it covered rooftops in the United States, Asia Pacific and Europe, the Middle East and Africa, not the 47 North American sites alone. The inspection reported mismatched connectors, connectors installed incorrectly, poor wire management and water inside inverters, and not a panel defect. Each event was reported to have averaged 2.7 million dollars, and lost generation at the switched-off sites was put at about 940,000 dollars a month. The account rests on internal documents obtained by a news organisation in 2022.

Contributing factors

The inspection, as reported, identified mismatched connectors, incorrect connector installation, poor wire management and water inside inverters. The article also describes how a loose connector can heat, and how a direct-current solar string does not pass through zero and so does not interrupt an arc in the way an alternating circuit does. It is not reported which of these factors applied to each of the six events.

Lessons learned

1. Where mating connectors are not the same type and brand, they need to be listed and identified for intermateability at installation.
2. A loosening joint may not show in production data, so rooftop arrays need inspection after commissioning, not only at handover.
3. Connector assembly and wire management should be treated as safety-critical installation work, because a poor joint or an unsecured lead can become a fire risk years later.

Not yet known

• Which factors applied to each of the six events
• Operator name
• Equipment model and age

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Source

ecoportal.net