New Solar Panel Sensor Addresses Fire Risk

In September, we invited solar experts to answer a question for us: How could firefighters safely shut off an array of solar panels  on a roof ?

The question related to a devastating fire in which firefighters were forced to let a 300,000-square-foot refrigeration facility stocked full of a business’ deli meats and cheeses burn to the ground. The reason? There was no safety mechanism for shutting off the building’s 7,000 rooftop solar panels. First responders felt they would need to breach the roof to stop the fire, but were ordered by the fire chief to stand down because they could not turn off the panels.

As a result, the entire facility was destroyed.

In our opinion, the story highlighted a crucial question. So we reached out to readers (many of whom we learned, were solar professionals) to solve this confusion.

The result was a healthy dose of helpful comments, and an email from a solar parts distributor, Paul Henson. Henson works for Incoparts, which is the US distributor for a solar panel sensor developed in Germany. The company that developed the sensor, TOPinno GMBH, is based in Aachen.

According to Henson, the inspiration for creating the “Willer electromechanical temperature protection element” was a fire just like the one that occurred in Delanco.

“There was a fire on a building in Munich which had solar panels and the Munich Fire Department let it burn to the ground,” rather than risk injury to its fire fighters, said Henson.

Realizing that this could potentially become a recurrent problem in a geographic area that is  reliant on solar power, the fire department approached TOPinno and asked for its help finding a way that the solar panels could be disabled in cases of fire.

The result was a small sensor, or fuse, that is placed between the panels and monitors the heat of the photovoltaic unit while subbing as a manual shut-off switch for emergency situations.

“The moment the fuses are broken due to the heat, the voltage will go down to below 120V, which is the legal requirement to be able to use water to extinguish the flames,” says TOPinno GMBH’s  General Manager, Raymond Huwaë. But first responders needing to access the roof because of a fire inside the building (such as in Delanco, New Jersey or Munich, Germany) would also have the option of disengaging the fuse manually.

“Currently we are negotiating with the UL Laboratories in Illinois USA, to have the fuse UL certified,” said Huwaë.

The sensor is also being considered for mandatory use in the U.K. TOPinno is hoping that the Solar Trade Association, which has regulatory oversight in the U.K. will require installers to include sensors in all rooftop solar installations.

The patent listing on the World Intellectual Property Organization (WIPO) website describes the Willer as “an over-temperature protection element [that] is particularly suitable for photovoltaic systems, but can also be used in other free wired electrical equipment both indoors and outdoors. In photovoltaic systems, the over-temperature protection element is used for electrical separation of the individual photovoltaic modules in danger cases. The over-temperature protection element also meets all electrical and safety requirements to be met by the operation in photovoltaic systems certified fasteners.

“In photovoltaic systems, the individual photovoltaic modules are usually connected in series. At the end of the chain voltages up to 1000 V DC voltage and currents from 8 to 16 A can occur in strong sunlight.”

The company adds that “the temperature-sensitive element can either be performed as with pine resin coated solder or a bimetallic thermostat switch. When a critical temperature is exceeded, the solder melts and the thermostat switch opens."

According to Henson, the cost of the fuse runs about USD $100 per box of two fuses. “With this in mind a 4200 watt array with 210 watt panels would have 20 panels – calling for 10 Willer fuses or 5 boxes of two [fuses].” That comes to about $500, not including installation and related costs.

Of course, manpower may still be an obstacle in situations that require a manual shutdown of large arrays. Disengaging 7,000 solar fuses by hand, as would have been required in the Dietz and Watson fire last September, would probably not have been possible or prudent during a structure fire.

But TOPinno’s solar panel sensor does open the discussion just a bit further about ways to ensure that a blaze inside a structure that has rooftop solar panels doesn’t result in a total loss of property.

It’s also worth noting that the Dietz and Watson fire may not have been the standard outcome for structure fires where a breach is necessary to ventilate the structure. In some cases. According to one Colorado wildland firefighter, many structures that require a breach are now ventilated from the side, meaning that a building that has rooftop solar panels may not necessarily need to be breached at the roof. But construction and other factors can still play into this decision.

It will be interesting to see what modifications may come up in the future as the solar industry continues to explore these challenges.

Images courtesy of TOPinno GMBH