There is a lot of scary content on the internet about roof mounted solar panels right now. Many of SolarCity's roof installations have caught on fire, endangering people inside the buildings.
So, are solar photovoltaic (PV) systems really safe?
Solar panel failure:
Solar panels can "fail" in different ways. Like LEDs, the theoretical lifetime is many years (10-30+ years) with a degradation in performance as the years progress.
But in our case, we will consider safety failures.
When a lot of stress is induced on a solar panel frame, it can cause the entire panel to experience a lot of strain. Stress can be induced by improper installation (accidentally bolting a panel down where a twist is imposed on the aluminum frame, extreme daily temperature fluctuations, etc).
Poor wiring practices have caused electrical damage since electricity was discovered. This has been a prime suspect in the SolarCity / Walmart investigations.
It's important to always verify wire sizing with the NEC 310.15 Allowable Ampacity table. Wire size can be determined based on the insulation rating of the wire. Remember: A wire's maximum ampacity (current) rating is based on the material (usually copper) and the temperature rating of the wire. Sizing wire too small will typically overheat the terminal connections, and almost certainly cause a fire. Don't just guess what wire size you need! When in doubt, comment on this blog and we'll be glad to help.
There are many other components that can fail in a large solar panel system. These include microinverters, circuitbreakers, fuses, connectors, etc.
One thing is certain: Heat is the worst enemy of any electronic device. Microinverters, or any inverter, should always be kept as cool as possible. They should never be installed in the direct sunlight. Check the inverter's datasheet to verify the maximum operating temperature.
Freak accidents happen. And when they happen, it's best to be prepared. A freak solar accident example could be, a metal object falling on the pos (+) and neg (-) wires of a solar panel, essentially creating a short circuit. Another example could be electrical surges, like lightening.
Solar panels must be installed with failsafes that open the circuit. (This is different from wind turbines, which need a circuit to fail closed with a dump load resistor bank). A failsafe that opens the circuit includes fuses or circuit breakers. Although they are more expensive, we always prefer circuit breakers. This is because many of our devices are portable and having a blown fuse while camping with no spares does not usually end up with a happy camper. Also, although cheaper in the short run, fuses are just one more component for our customers to keep track of, source, and keep in stock.
All exposed metal parts (e.g. frame, racking, conduit, enclosures) of PV systems (regardless of voltage) must be grounded to protect against surges, lightening, etc.
Risk management of solar PV systems is not something that people usually think about. Usually the panels are included in your homeowners or business property insurance, but make sure you include the microinverters, racking, mounts, and anything else that adds value to your PV system.
....But an insurance policy can't replace lives...
That's why Cutting Edge Power always prefers a ground mounted PV system. We offer many different packages to mount solar panels on a strong steel structure on the ground. Ground mounted solar panels can be extremely easy to install, clean and maintain. But most importantly, when assessing fire risk management, they are much safer than roof mounted systems!
Here's a 3D example you can move around: