More and more businesses and domestic households are installing rooftop solar systems due to their affordability and many benefits. As solar photovoltaic (PV) installations become more popular, it is critical firefighters receive proper solar education and training to ensure their safety with regard to the presence of high DC voltage.
The authorities require all solar systems comply with electrical safety standards as outlined in electrical codes to mitigate risks for those working on or around solar systems. Unfortunately, the codes are not sufficient to remove all risks to ensure a safe environment for firefighters or those not familiar with solar technologies.
Vision Energy Solutions partners with a premier solar technology company, SolarEdge, that provides an additional safety feature, SafeDCTM that is beyond what is required by regulatory agencies to protect responding firefighters.
With Traditional Inverters Shutting down the inverter, string DC disconnect, or AC breaker does NOT shut down voltage on the roof
Most solar panels have an output capacity of 30-60V each. Connecting several panels together in a string (solar array) can result in dangerously high voltage levels for installers, and others working on or around the system, like firefighters. Traditional string inverters cannot reduce the panels’ combined DC voltage output, even if the main AC circuit breaker is turned off. The AC voltage supplying the building will be shut down when the power is turned off, but the DC voltage generated by the panels from the sun will remain high.
In short, an average-sized solar array of only 20 panels of 40V/each string together in the traditional method would output 800V of DC power that cannot be turned off as long as the sun is shining. This is a deadly level of power for those working on or around the system, as the human body can only tolerate 50-60V.
Several safety measures have been attempted, but none of them remove high DC voltage risks:
- Manual Inverter Shutdown Switches: This will interrupt the current flow, but voltages remain dangerously high.
- Automatic DC Breakers: Many inverters have an automatic breaker feature to interrupt the current flow, but again it does not disconnect the panel voltage.
- Solar Panel Covering: Firefighters have attempted to cover the panels, so they do not absorb sunlight generating DC voltage. Spraying foam on the panels proved to be ineffective because the foam evaporates or slides off the panels before the fire is extinguished. Covering the panels with an opaque material requires firefighters to climb onto burning roofs to drape the coverings over the panels. There are several dangers involved in this process, valuable fire extinguishing time is wasted, and the risk of electrocution remains.
With SolarEdge SafeDC™ Power optimizers shut down DC voltage in modules and string wires immediately when the inverter is turned off, or when the AC breaker is disconnected
The SafeDC Solution: Panel-Level Voltage Shutdown
Our SolarEdge systems have a built-in safety feature, which eliminates safety risks during installation, maintenance and firefighting.
The SolarEdge SafeDCTM does the following:
- Automatically shuts-down the PV systems during emergencies.
- Lowers and maintains the voltage in all DC conductors below a safe range.
For system maintenance or firefighting purposes, shutting down the AC power will automatically reduce the solar panel DC voltage to 1V each. AC power can be shut down in several ways that firefighters are already familiar with:
- Switching the main AC circuit breaker off
- Turning the inverter switch to OFF
- Turning the AC/DC Safety Switch to OFF
Therefore in our 20-panel solar system example above, when any of these methods of powering down the system are employed, the total system voltage is reduced to 20V. In other words, the same solar system with and without the SafeDCTM feature goes from deadly to safe voltage levels when the sun is shining. This allows installers, maintenance workers, and firefighters to safely do their jobs on buildings with solar systems using the SolarEdge system.
Please read SolarEdge’s white paper outlining more technical details about the SafeDCTM feature.
Vision Energy Solutions takes safety seriously. Our technicians have all received training from SolarEdge representatives to ensure systems are installed with the safety of our clients and first responders in mind.
We are proud to bring firefighter-safe solar PV systems to Fiji. To learn more, please request a free project feasibility assessment.