Brent Harris, P.Eng, is CTO of Sustainable Energy Technologies, and a co-founder of the company. He led the development and commercialization of the company's technologies, from early demonstrations to the launch of its latest Sunergy inverters. Mr. Harris has a passion for decentralized energy in general and for solar power in particular. He is an active proponent of changes to the management and regulation of our electric system that will enable greater adoption of decentralized and renewable energy technologies. Mr. Harris is a member of the board and treasurer of WADE Canada, and was a member of the board of directors of the Canadian Solar Industries Association from 2005-2008.
AltEnergyMag Interview - Solar System Safety
Brent Harris | Sustainable Energy Technologies
From the perspective of firefighters and first responders – what are the greatest safety concerns with solar installations?
Firefighters and first responders have a number of concerns in mind when they are responding to an emergency call at a residence or building with a solar PV system. It is difficult to pinpoint one “greatest” safety concern in particular because I believe that it is the combined risks of all of the potential issues that lead to their greatest concern.
Buildings with high voltage solar PV arrays on the roof can lead to numerous predicaments. Emergency crews have noted issues such as:
- An inability to properly “vent” a building (cut a hole through the roof or floorings to allow noxious fumes and smoke to escape).
- Significantly decreased walking space on the rooftop
- The bursting of burning modules leading to flying glass, and chemical matter
- Dangers of electrocution
Just to name a few.
However it could perhaps be said that the greatest concern for safety, firefighters and emergency crews have is not knowing if there is a solar PV array at that location. When responding to emergencies at tall buildings, or fires with a large amount of smoke, emergency crews are then forced to enter the building “blind”; meaning they do not know what they are going to face when they enter into this building. Although beginning to be noted as a concern in places throughout California – this is an issue which holds greater weight in Europe, particularly in countries such as Germany where rooftop solar systems are more prevalent
What are some of the proposed solutions to address these issues and concerns by the solar industry? Governments? First Responders?
For a long time these issues were not really seen as a major cause for concern. It was believed that whatever situations could arise from the solar array, or be caused by the solar array would be manageable. It is because of this old way of thinking that the solar industry and governments have not taken a serious look at these issues. The solar industry has always met with certification standards of safety – but have not, in any significant way – gone beyond that.
With the exception of small local government legislation being proposed and implemented just recently, there has been relatively no government action to propose and enforce solutions to increase the safety of first responders.
Emergency teams however have really started to pick up on the problems arising from and potential dangers of rooftop solar PV systems. Crew members unfamiliar with and not trained to deal solar PV systems can greatly increase those risks. Therefore many first responder crews and in various jurisdictions have really taken the reins to develop solutions to system design, and first responders safety protocols and training in case of a solar PV system. Through the creation of training videos, hosting information and training workshops, and writing training documentation first responders are helping to develop the knowledge and confidence of their fellow crew members of what to do in case of a solar system. Just having the knowledge is a major step to increase the safety of emergency crews responding to a situation.
Some jurisdictions have even taken it upon themselves to write system design guideline documents which make recommendations for safe system design for both the home owners and emergency crews.
Recommendations such as setting the system back 2-3ft from the roof edge to create a walking area, installing systems with lower voltages, creating a system which is compact (having all or most of the system components located either on the roof or all together), and creating an array which runs AC wiring from the roof through the building rather than live DC wiring could all potentially decrease the risks to emergency first responders.
Following these suggestions some local governments – for example Oregon- have instigated either a setback rule for residential rooftop solar systems, or other recommendations to work with the Firefighters and emergency crews making safer solar for everyone.
Are there currently any technologies available for the market – or in development – which could address these safety concerns, and provide solutions?
Low-voltage inverters, and micro inverters which focus on having a low-voltage array with an AC system design are currently available to the market today. These inverter products do not compromise performance – and in some cases have been shown to actually improve system yields. Also, because of the AC system design with the inverters mounted close to the array, the safety of the system increases. There are no live DC wires running through the building walls which may be of concern for first responders and because the systems overall DC voltage is limited to 120V the risk of electrocution is significantly decreased.
Other high voltage inverter manufacturers are offering solutions which relying on additional system components to break the system into smaller pieces as an attempt to bring down system voltage – creating a sort of pseudo parallel configuration. However, it is unclear whether relying on electronics for protection against electric shock will be determined to be an acceptable solution. Would you bet your life on a burning transistor?
Are there currently any wide scale or formal policies or procedures in place? If so – could you please provide examples?
As of yet, no wide scale policies or procedures have been put in place – apart from the required certification standards for system safety, which vary greatly from region to region. In some places, local governments or government offices have developed their own policies or procedures to try and find a solution.
The Federal Network Agency in Germany has set up a central registry system through which homes/buildings with solar arrays can register their address as having a solar PV system. This sounds like a brilliant idea – and once fully implemented it will be very valuable to emergency crews – however this registry system does not currently have the capability to ‘talk’ to the emergency response databases – so although the idea is right, there are still some kinks that need to be worked out.
In the state of Oregon, due to the introduction of their pilot FIT program, and the anticipation of a large amount of residential solar installations, the government has introduced a ‘setback’ rule. Rooftop solar systems must be a minimum of 2ft away from the roofs edge. This allows for more walking room for emergency crews and also allows for safer ventilation.
In California, the CALState Fire Department – together with a whole team of representatives from business, the solar industry, firefighter, government officials etc – to develop ‘guidelines’ for a safe solar array; to date none of these suggestions have become formal policy.
Are safety concerns appropriately addressed by these solutions ie: are they certifiable? Why or Why not?
For a long time many of the safety concerns which are being raised for serious discussion now, were seen as manageable and were assumed to be of rare occurrence. Now, with aging systems, the discovery of external issues raising new concerns (shoddy workmanship, wear on the wiring from UV exposure or animals chewing on the wires) and through the strong actions being taken by firefighters and first responders we are developing a greater understanding of the complexity, and the magnitude of the risks which may be encountered by emergency crews.
Even still –with all of this knowledge coming to the forefront – emergency services workers are driving all of this development themselves. There has been very little push for safer systems from the industry itself, or by demands from government.
Currently the only certifiable solution is to design a system which meets with the European IEC’s requirements for an Extra-Low voltage (ELV) system – which means limiting the PV arrays’ operating voltage to below 120V. Creating a system which operates at this level at all times provides greater assurance of safety than depending on solutions which rely on electronics to break the system up into smaller ELV compliant components in the case of a fault. These “solutions” also add cost and potential failure points to the system.
Is there any legislation requiring certain solutions for the protection of firefighters and EMS personnel?
Currently the only protection offered to firefighters and EMS personnel that is legislation is "the right to refuse entry". Firefighters and EMS personnel maintain the right to refuse to enter a building if:
- there is no one/thing in the building which may be endanger
- they feel that entering into the building to attempt to extinguish the fire would jeopardize the lives of their crews and themselves
- they have a high enough level of confidence that they can commence with a 'controlled' burn
Will or do these proposed technologies and solutions abate the energy yield or have an effect on the cost of solar rooftop PV systems?
So far these technological solutions for low-voltage systems have shown to have no negative effect of the energy yield of a system, and in most cases can actually increase the system’s energy yield. When arranged in parallel (which is a low-voltage architecture) systems are less susceptible to real-world disturbances because each module can act independently of the others. So if one module’s performance is impacted by shading or soiling it will not bring down the performance of the system.
High-voltage systems couple the performance of all modules in a string, so when one panel is adversely affected so is the rest of the string. High voltage systems also have an inherent risk associated with them, and the solutions to address these risks will most definitely incur an additional cost; however it is unclear at this time how much additional cost there will be. In the end, no matter what a person does – adding fault detectors, monitoring electronics or “subcombiner” boxes – to try and turn a high-voltage system into a low voltage system, they are only adding potential failure points and cost, and will never really be able to achieve the required level of safety.
How is Sustainable Energy Technologies addressing these issues with their products and services?
Sustainable Energy Technologies has always maintained a clear focus on the safety of solar systems. Our proprietary technology keeps the operating voltages of an array to within the 'extra low-voltage’ bandwidth; and by having an outdoor rated inverter mounted on the roof with the array we are able to create low-voltage compact systems. Isolating the DC wiring to the roof removes the concerns first responders may have when ventilating a burning building because there is only easily managed AC wiring running through building.
The AC system design decreases system losses from the DC wiring, and through parallel architecture increases the energy yield of a system. Our system was built with safety in mind, and is a perfect match with the recommendations and “guideline” suggestions for system design made by emergency crews, and firefighters.
Low voltage systems also decrease the chances of arcs that can cause fires to start, because not enough voltage is available to initiate or sustain an arc.
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