In the wake of recent flooding on the east coast, industry group Safer Solar is calling for mandated rapid shutdown technology on solar power systems in Australia.
Most rooftop PV systems in Australia output high voltage DC current that is delivered to the solar inverter installed on a wall below. This can be problematic in flooding, particularly if the inverter isn’t first switched off before inundation. Even if it is, the solar panels are still outputting power.
During recent floods on the east coast, we saw images of people awaiting rescue on rooftops – some of these with solar panels. Being on a rooftop isn’t particularly safe at the best of times, and a wet solar rooftop even less so. While rooftop DC isolators are useful in this scenario (one of the few where they are), there are still a bunch of panels cranking high voltage DC current to that point. There remains a risk of a powerful electrical current running through the roof if damage to wiring occurs.
Thankfully, there doesn’t appear to have been any serious injuries or deaths from live solar panels during a flood emergency in Australia to date. But safety can always be improved and it seems we are lagging behind other countries in this respect.
Safer Solar Systems With MLPE
MLPE (Module Level Power Electronics), aka Panel Level Optimisation (PLO) are technologies that can help reduce the risks. Two forms of MLPE are microinverters and power optimisers. These devices are installed on the back of solar panels or on the racking beneath them, usually one per panel. In the case of microinverters, the devices replace conventional string inverters and convert the DC output from a solar panel to safer AC.
Safer Solar spruiks these technologies as providing solar energy management systems able to:
- Quickly and easily shut down solar PV systems when the need arises
- Isolate individual solar panels that fail to meet safety standards through remote management
- Monitor solar panels remotely for problems to enable quicker post-disaster recovery.
The most popular microinverters used in Australia are manufactured by Enphase Energy – and it’s no surprise the company is involved with the Safer Solar initiative.
“Rapid shutdown is already mandated in the US so solar panels can be made to stop producing energy in the event of a disaster like fire, flood or tornado,” said Enphase Energy General Manager ANZ Wilf Johnston. “Even developing countries such as Thailand and the Philippines now mandate rapid shutdown systems.”
Mr. Johnston believes the risk in Australia is increased considering many systems are now 10 years old or more.
“Australia needs to mandate that replacements for these old systems and all new systems meet the highest safety standards – which includes rapid shutdown,” he said.
Master Electricians Australia is also backing the call for safer solar, stating in the short term it would be helpful for governments to launch information campaigns ahead of flood season.
“In the longer term, we need to address this through legislation and upgraded standards and we need our state governments and regulators to step up on this issue,” said Master Electricians CEO Malcolm Richards.
The use of microinverters and optimisers offer other benefits, such as increased flexibility in system design – but the use of MLPE devices will increase the cost of a system by around 20%.
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Conservatively it costs around 55AUD per panel for RSD devices in the US which is getting onto half the cost of the panel. Micro inverters are about the most expensive way of doing solar; they have their place, but not as a mandated option. DC optimisers again have their uses for shaded zones, but have the added cost above, and I’ll just ignore the added, hard to access, point of failure on every panel.
Lets do some quick math. In 2023 Australia installed 970MW of small scale rooftop solar. At an average of 300W/panel that is 3.233 million panels. @55AUD/ panel for RSD, that is 178million AUD/ year to save… well no one, because no one has been killed by this yet. maybe someone in the future?
forget your stance on climate, this $178mill/year or the 20% above stated installation cost increase will put many people off solar, leading to more air pollution from power generation. Meanwhile, 1780 people die in Australia every year due to outdoor air pollution according to Our World in Data. Safer is better, but the whole picture is important and there has to be some balance.
Most roofs are not 100% covered in solar, surely something along the lines of “Residential houses with inadequate, solar panel free, roof standing space for the occupancy, which have roof access (Such as a sky light), that are located in a flood risk zone, require RSD” would be much more sensible, along with some public education not to jump around on PV panels. Either way, people need to know more – RSD will only help if someone actually pushes the button to trigger it (NEC RSD is entirely aimed at firefighters who are trained for it).
-AC IS NOT SAFER THAN DC, they will kill you just the same, electricity is dangerous at 50V and quite deadly around 100V, anything past that is like jumping off a 50m or a 60m cliff, same outcome. AC is 240V (which actually means +-340V), Typical PV strings are DC 100-500V. it is more about where it touches you, not AC vs DC…
How is an automatic shutdown system supposed to know when there is a fault, any sort of fault?
Perhaps there could be a way of calculating the theoretical voltage and current output of a solar panel system from the panel characteristics, the panel temperature and a measured solar intensity and then comparing this with the voltage and current at the load wherever that is.
This system would need to allow for a power-limited load and also panel aging but could be a single-box solution located off-roof somewhere convenient.
Another option might be to just build the panels with all wiring in heavy duty conduit for robustness but might there be other points of failure?
I note that the grid is run in bare wires at the top of tall poles, no doubt with earth-leakage detection at the kiosk but the only other safety measure is to warn people not to go near fallen wires.
Hi Bill
Arc fault detection in simple terms is a layer of electronics that “listens” to a circuit for the signature interference an arc creates. When there’s a short the voltage may stay up and maintain the arc at a significant level, but it’ll create something akin to radio noise in the process. Once detected the circuit can be shut off or shorted to ground.
The yanks are mad for bare earth wires, steel conduit & 1920’s looking infrastructure. They like rapid shutdown systems but the rest of the world copes without.