First off, solar systems aren’t killers, but in certain—very unusal situations, they can be lethal. Once a PV module is connected to wiring, it’s outputting electricity when light hits it, and when the array’s wiring is compromised, or the grid is compromised, PV modules can pose a shock hazard. Solar manufacturers are aware of this and are designing systems to be as resilient as possible, but thus far, there are few if any PV modules that are designed to stop operating when they detect an event. Bosch thinks it has a solution.
German engineering giant Bosch is bowing out of silicon photovoltaic manufacturing this year. However, the company is still thinking about how to make a better PV module. Now it’s developed a junction box that makes PV modules safer by automatically turning them off when facing hazardous conditions, like during a house fire or after a tornado—and it’s interested in selling the technology.
One of the issues that has plagued PV is the inability to easily turn a system off at the module level. So in the rare case where a PV array is in a fire or a tornado on a damaged structure it could still be producing electricity and sending it down frayed or damaged wiring before the power is cut off at the inverter, posing an invisible and potentially deadly shock hazard to firefighters and other emergency personnel.
At this point, there’s also no safety standard for PV modules related to automated cutoff (also known as de-energizing) developed by Underwriters Laboratories (UL) or in the National Electric Code, though they are working towards developing standards. Such standards could involve using a device like Bosch’s switching junction box.
But there are already some ways to cut-off power at the module level, like using microinverters from companies like EnPhase, or Westinghouse Solar, but that requires some additional equipment. Other safety devices can be activated by heat, but may need to be replaced after the event. Bosch’s solution? An automated cutoff at each panel’s junction box. The junction box is where all the cells in a PV module are harnessed together to provide their collective power to a larger array.
The cutoff operates automatically. “Intelligent electronics in each junction box ensure an automatic switch-off of the individual modules and the whole system when the building mains supply is interrupted,” Bosch said. “The switch-off function can also be activated by an external control signal from installations such as a fire alarm system control panel or an emergency switch,” it added.
One of the ways the devices Bosch has developed are different than microinverters is they will turn themselves back on. “The new Bosch concept automatically initializes a subsequent re-start once the critical situation has ended. In this way, full yield is ensured after a safety-relevant switch-off,” the company said.
In developing their safer junction box, Bosch brought in multiple areas of expertise, including its automotive division, the company said. However, since the company will cease producing PV modules this year, the company is interested in selling off the technology, which the company said is viable for all types of PV modules. “In many cases, there is no need to retool machines to integrate the solution into the module production process. In addition to a general improvement in solar power system safety, the new Bosch Solar Energy solution concept also ensures that solar power systems comply with different industrial standards and guidelines which already apply or are in preparation,” the company said.
Bosch will showcase the devices at the European lntersolar convention in Munich, Germany between June 19 and 21.