Rooftop solar photovoltaics can help real estate owners/managers lower energy costs, boost operational resiliency and meet ESG commitments, but proponents of the technology caution that it also packs a potentially lethal electrical charge. Vigilant maintenance and risk management are critical for what is, in essence, a power plant affixed to a highly valuable asset.

Clean Energy Associates (CEA), a consultancy providing project management, engineering and technical services for solar, green hydrogen and energy storage systems, is sounding the alarm after safety audit data from more than 600 rooftop solar PV installations worldwide revealed a disconcerting magnitude of fire hazards. Just 3 per cent of audited sites were completely clear of safety concerns, while nine of the 10 most prevalent issues surfaced in more than one quarter of the inspections.

“This is frightening: one, for your buildings; and two, for the industry,” Chris Chappell, CEA’s senior director of engineering services, asserted during a recent online presentation. “These things are happening on your roofs right now.”

Canada was among the 14 countries in North America, Europe and Asia-Pacific where the safety audits were conducted. Nearly half the examined installations — 49 per cent — were improperly grounded in some places, posing risks for on-site personnel and compromising equipment performance, while 47 per cent of the installations sported cracked or soiled modules, creating shock and fire hazards in addition to diminishing operational performance.

Connectors emerge as a hazardous link

A large share of the identified risks relate to connectors — or the wiring and cabling connecting the modules, racking and inverters — of which there may be hundreds or thousands in a rooftop installation. Faulty connectors could be the source of arc flashes, an opening for water infiltration or an ignition source should they overheat, melt and drop down onto the roof ballast. Chappell and his colleague Ankil Sanghvi, CEA’s engineering manager, cited examples of all those occurrences during the presentation.

“The 10 most common items that we found, these are not equipment-related per se. These all have to do with workmanship,” Chappell maintained. “The modules, inverters and racking are all integrated with wires and it’s these little things that are the biggest issues that we see on sites.”

Sloppy or perilous practices include: pairing the positive and negative sides of connectors from two different assemblies; placing wiring over sharp metal edges that can inflict damage as they expand and contract in fluctuating temperatures; and over-torquing connectors or other kinds of aggressive handling that can cause cracks in components. Manufacturers’ specifications typically state the required type of DC connector, but safety auditors found that instruction had been flouted at 41 per cent of the sites they examined. Connectors were improperly installed in about the same portion (40 per cent) of systems.

“These connectors are UL listed and come as an assembly. You can’t cross and mix parts, but it happens a lot, more times than not, because the threads (from different assemblies) are the same,” Chappell explained.

“This is a big no-no. We have seen, a lot of times, connectors burning because of cross-mating,” Sanghvi concurred. “With all DC connectors, please follow the manufacturer’s manual very closely and please make sure that you are using the right tools while assembling the connectors.”

Hotspots implicated in arc flashes and ignitions

In some cases, lurking fire hazards should first become evident through a drop in power output. For example, damaged, soiled or shaded modules can cause a mismatch in voltage that will result in underperformance and can also lead to hotspots where one cell is operating at a higher temperature than those surrounding it. Such hotspots could potentially ignite nearby organic material and/or cause the backside of the module to melt, increasing the risk of arc flashes.

Shading could occur if modules are crowded too closely together. Natural elements — including wind, hail, lightning and animals — and on-site personnel could cause other types of damage. In the latter case, Sanghvi chides some marketers for misleading messaging.

“We see module manufacturers advertising their modules by walking on them and showing people: Look how strong they are,” he recounted. “Every time they walk on the module, they break the cells.”

“Those cracks are going to grow and grow and grow,” Chappell added. “Tell the teams up on your rooftops: Do not walk or kneel on the modules.”

CEA’s safety audit data shows hotspots detected on modules at 31 per cent of the inspected sites. As well, hotspots were recorded in enclosures encasing solar batteries at 19 per cent of sites. That’s in part attributed to improper termination of wiring to enclosures, which was found at 40 per cent of the audited sites.

Sanghvi recommended infrared scans as part of the maintenance schedule with scans of all enclosures at a maximum interval of six months. As part of daily operational oversight, he suggests keeping watch for “inconsistencies” with connectors and obvious damage like cracks and broken pieces. Nevertheless, potential hazards are often difficult to detect through cursory visual scrutiny and impossible in some cases. For example, he recalled physically opening an enclosure during one field inspection and finding some questionable splices.

“A lot of these decisions are made on the side by a technician or an electrician,” Sanghvi reflected. “For this particular site, no one knew the splices existed in this box. No one knew there was something bad going on in this box. Luckily, we found this before it became a major incident.”

Timely risk management reminder for envisioned new project development

Vigilant safety monitoring programs could be particularly important for building owners/managers who acquire rooftop solar PV systems through a transaction and have had no input into its design and installation. In any case, some aspects of that process can become murky through the chain of contractors and sub-contractors involved. For new installations, Chappell sketches out some basic parameters.

“What you want to do is control your installers with design,” he submitted. “In your notes and your design drawings, you want to tell everyone: This type of connectors is acceptable; cross-mating is not. Then you meet with that EPC (engineering, procurement and construction) and you reiterate: Do you understand?”

A risk management reminder is timely as jurisdictions throughout North America and around the world encourage new solar PV installations in an effort to increase renewable supply and promote distributed energy resources (DERs) that can help alleviate demand pressure on the electricity grid. In Ontario, for example, a regulation was enacted last year to permit third-party net metering, freeing prospective clients, such as commercial and multifamily landlords and condominium corporations, from upfront capital investment and ongoing operating costs.

This aligns with the Ontario government’s vision to tap into an estimated 10,000 megawatts of DER capacity, as outlined in the clean energy plan it released earlier this summer. “Eligible third-party ownership arrangements now include leasing, renting and financing options with energy service providers as well as power purchase agreements with a licensed third-party generator, making rooftop solar and other DERs accessible to more Ontarians looking to better manage their energy costs,” it states.