Despite the widespread availability of safe solar technology, 70% of solar systems sold in Australia use high DC voltages that pose a fire risk under fault conditions. By choosing an AC or DC optimised solar system, homes and businesses can be assured their property is protected.
FIRE SAFETY: SO HOW IS SAFER SOLAR ACHIEVED?
A growing number of installers, manufacturers and distributors throughout Australia are working to raise homeowner and business owner awareness about the many benefits of safe solar technologies.
There are two types of safe solar system technologies available in Australia:
1. Microinverter-based systems
2. DC optimised systems
The type of system is determined by the kind of inverters that have been installed. More information about safe solar system technologies can be found here.
Conventional DC solar solutions use dangerous DC voltages that pose a serious fire risk under fault conditions. Even if good quality equipment is well-installed, the effects of variables such as weather, degradation, pests and equipment failure mean that if left unchecked, safety risks will always increase as the system ages. Due to the low cost and lack of understanding about these risks, conventional DC solar solutions remain popular across Australia, even though other countries are in the process of phasing them out due to fire safety concerns. Conventional DC solar systems operate with high voltage DC without safety features such as rapid shutdown, increasing the risk of fire in both residential and commercial systems.
THE SOLAR FIRE RISK
Did you know that since 2010, firefighters have attended, on average, two solar-related fires each week in Australia1?
An audit of the Clean Energy Regulator (CER) by the Australian National Audit Office (ANAO) found that potentially hundreds of thousands of homes across the country have substandard solar installations, and tens of thousands are considered unsafe2.
Most solar fires only cause property damage, though there have been instances of homeowner injury. The good news is that if you make an informed purchasing decision based on facts, you can get all the benefits of solar power for your home without any fire risk.
WHY is this important?
Electrical fires are usually caused by an arc when current jumps from one point to another in a continuous flow. An arc fault is a high-power discharge of electricity between two or more conductors. This discharge generates heat, which can break down the wire's insulation and trigger an electrical fire3. The temperature of an electrical fire depends on several factors, but on a typical solar system, it can easily melt glass, copper, and aluminium. DC arc faults can reach 1,085°C.
Conventional DC solar systems can generate up to 600 volts of high-voltage DC, which must run from your panels through your ceiling to the central inverter located on the side of your home. Even the smallest equipment failure, such as a damaged cable or a loose electrical connection, can cause a DC arc fault that can result in an immediate and violent fire.
DC arc faults within the high voltage wiring can happen at any time of day or night on conventional DC solar systems. This wiring runs from the solar modules on the roof down to the string inverter, which is usually installed adjacent to the main switchboard.
There are around 50 joints in the circuit of a typical 5kW domestic DC solar system which are connected when your solar is installed. Each join is a potential future point of failure. To add to the risk, there are also additional connections inside the solar modules, DC isolators, and the string inverter, which can also fail. It would just take one failure at any of these connections to trigger an arc fault that results in a fire.
There are two main causes of DC arc faults:
- The insulation on one or more of the DC wiring is compromised
- A connection anywhere in the DC circuit is compromised
It is inevitable that at some point over the 25-year life cycle of a solar system, a failure will occur, and with a DC system, the consequences can be catastrophic.
Factors that lead to DC arc faults, include
- Animals such as insects, rats, possums, birds, damaging wiring or cables
- Extreme weather events such as cyclones, floods, high winds and hail
- Accidental damage
- Intentional damage such as rocks on panels or loose cabling being pulled out
- Water ingress due to ageing of plastic fittings, conduits, rubber seals
- Failure of plastic fitting and enclosures due to UV exposure
- Moisture build-up within sealed components due to thermal cycling
- Poor installation workmanship
- Inappropriate component selection
- Poor quality equipment.
AC vs DC – Fire Safety Considerations
Unlike DC, the voltage in a 230 volt AC power system continually passes zero as current cycles between positive and negative values, virtually eliminating the risk of a sustained arc fault. For an arc to be self-sustaining, the arc must be continuously present which is apparent with DC as it remains at a sustained voltage. In contrast, the voltage in AC systems constantly alternates, resulting in a self-extinguishing arc.
Improving Australian Standards
Australia lags behind the US and other countries, where conventional DC solar systems are no longer installed due to safety concerns. Despite increasing international momentum in the adoption of stricter solar system safety standards, the Australian Standards are yet to be changed. Are you considering a solar system purchase? It is critical that you request safe solar equipment that incorporates internationally recognised rapid shutdown technology as well as a microinverter or DC-optimiser based system architecture.