Rooftop solar systems are designed to produce electricity for years, but problems in their wiring and connections can create serious safety risks. Amazon faced this issue at several of its facilities in North America between April 2020 and June 2021, when six solar sites reported critical fire or arc flash events.
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Amazon had solar installations at 47 North American sites. Six of them experienced either a fire or an arc flash event during the 14-month period. This meant that about 12.7% of the sites with solar installations were affected.
The incidents included a three-alarm fire at an Amazon fulfilment centre in Fresno, California, on April 14, 2020. The fire damaged 220 solar modules. Fourteen months later, a two-alarm fire at a facility in Perryville, Maryland, brought around 60 firefighters to the site.
The incidents led Amazon to take its US solar operations offline by June 2021. The company wanted the systems to be properly designed, installed and maintained before they were switched back on. According to Eco portal, an internal Amazon report described the rate of dangerous incidents as “unacceptable and above industry averages”.
What caused problems
Amazon brought in Clean Energy Associates (CEA), an outside inspection firm, to examine its rooftop solar portfolio. The audit found one critical issue and 259 significant findings across sites in the US, Asia Pacific and Europe, Middle East and Africa.
The findings included mismatched module-to-module connectors, incorrectly installed connectors, poor wire management and signs of water entering inverters. These were not defects in the solar panels themselves. Instead, many of the problems were linked to how the different parts of the systems had been connected or installed.
Connectors are important because they join electrical cables and allow electricity to move between different parts of a solar system. If two connectors do not fit properly, electrical resistance can develop at the connection.
Resistance can produce heat. As the connection becomes hotter, the plastic around it can soften, which can make the connection even less secure. In some cases, this can lead to an electrical arc.
Solar systems also have a particular safety challenge because they generate direct current, or DC. Unlike household alternating current, or AC, direct current flows continuously in one direction.
In an AC system, the current repeatedly passes through zero. This can help an electrical arc stop. A solar circuit, however, can continue supplying current while sunlight is available, allowing an arc to keep burning.
