Code Changes Impacting Solar Design
Solar energy across the country is booming and has been for the past 10 years. In response, the National Electrical Code (NEC) as it relates to photovoltaic solar arrays has been evolving for a quite a while. The last two editions represent a direct response to the number of systems being installed at all levels and sizes.
Overall, the code is smarter and more responsive to the reality of the market today. What’s most exciting is that design engineers, authorities having jurisdiction, and emergency responders have played a key role in the most recent developments.
Because of the dynamic nature of the solar industry and the number of parties involved in influencing the code, the code is actually preceding the product in many situations. The code is pushing the marketplace to develop and engineer more reliable and safer products.
Rooftop solar arrays are getting safer
It's been commonplace for rooftop solar arrays to have high-voltage DC cables, each ranging from 600-1,000 volts. A lot of people are anxious about having a high-voltage system on their rooftops: owners, insurers, and firefighters in particular. In response to this apprehension, ‘rapid shutdown’ requirements have been incorporated into the NEC.
First introduced in the 2014 edition of the NEC, and expanded in 2017, the code requires a rooftop solar array to have the means to safely terminate the high-voltage component by an accessible switch on the ground level. To meet these requirements, the industry is moving to designs that include module level electronics/devices. The most commonly used devices are micro-inverters which have extremely low DC voltages and automatically remove any power flow from each module upon activation of the disconnect switch.
These are required designs that will allow an emergency responder to not worrying about being electrocuted by a source that cannot be disconnected.
Code is getting simpler
Article 690, which governs photovoltaics, has been condensed by 20 percent, removing nearly 11,000 words in the last two code cycles. Potentially confusing language, wiring methods, and system definitions have been streamlined making it easier on everyone.
A more simplified code leads to more reliable designs, cheaper installations, and ultimately a safer product.
A ‘large-scale’ or ‘utility-scale’ solar array has more in common with a modern power plant than it does with a residential or commercial array, yet both had been governed by the same rules of article 690. Until now.
The massive arrays which are typically built out in the desert or away from commercial or residential areas, secured behind a fence, and are only accessible to skilled and qualified individuals. A new article, 691 specifically addresses arrays 5MW+ allowing the engineer to employ design techniques more relevant to the system size.
The last code revisions have delivered a very clear message that the code will continue to evolve, be proactive and responsive to the expanding renewable energy industry.