SunSpec Alliance replace on work to simplify speedy shutdown signaling techniques

sunspec alliance laboratories

In just a few short years, the industry’s concept of a Distributed Energy Resource (DER) has shifted from a straightforward rooftop solar system that cuts your electricity bill to an incredibly complicated device that does what the old system did and stores energy and the light stays on at night or in the event of a power failure, electric vehicles are supplied with power and the supply network is strengthened.

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Given the rapid pace of technological and regulatory change, complexity has crept into DER system design and business models. And as complexity increases, the likely outcome is the prospect of higher costs, lower predictability, and increased risk. These statements apply to the DER system and also to the individual components in the system. To illustrate this point, let’s consider module-level power electronics (MLPE), which are now part of the equation.

In 2014, the National Electrical Code (NEC) introduced requirements for detecting arcing faults and shutting down system arrays to improve safety. By 2017, the NEC began expanding the scope of the regulation by requiring that any rooftop solar array must have both arc fault protection and the ability to shut down every single module in the system within 30 seconds of being deactivated by a user.

To meet these compounding requirements, manufacturers have introduced a variety of proprietary add-on devices (MLPE) to develop inverter-based solar system designs. The result has been a dramatic increase in the total number of parts, a doubling in the number of connectors, and the inadvertent consequence of signal overload (“noise”) on the DER system’s DC wiring that affects both arc fault detection and quick shutdown functions can. Overall, these factors lead to higher component failure rates, an increased safety risk for construction personnel and system owners, and lower system performance.

There has to be a better way.

Simplicity through standardization, integration and adaptability

In anticipation of this future, the members of the SunSpec Alliance realized that adding more parts would not be a successful strategy for DER system manufacturers who rely on efficiency and longevity to maintain profitability. With this in mind, the goal of DER system design should be to implement strategies that allow compliance with sometimes overlapping regulatory requirements while keeping the number of parts, connection points, and physical work required to build the system constant, and those goals without Introducing to achieve risky, new technologies.

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When SunSpec began developing the open SunSpec RSD (SunSpec Communication Signal for Rapid Shutdown) standard, the companies involved adopted three key principles:

1. The challenges of implementing a shutdown standard are old. Basic, proven, and well-aged solutions would be used to address the problem.
2. Regulations set limits for possible solutions. The need to embed technology into existing system components (e.g. the PV module junction box, PV connector, or inverter housing) and use the PV array cabling was evident and necessary to minimize costs and create a to enable legally prescribed mass introduction.
3. A quick shutdown signal is likely one of many mandatory signals that would be forced to share DC power lines. The Federal Communication Commission regulations had to come into play.

Given these principles, the intellectual property that makes up the standard would need to be mature, unencumbered, and well supported by high-volume component products to ensure reliability, acceptable cost-to-market, and sustainable long-term costs.

This combination of factors sets the bar high for a de facto standard that requires a number of points of evidence to be easily marketed. The SunSpec RSD solution would require a primary silicon chip vendor (Texas Instruments). Harmonization with the test standard UL 1741 SA; a network of SunSpec Authorized Testing Laboratories to validate the implementation; and shipping products from at least a dozen manufacturers that could be embedded in PV modules and other popular system components. The SunSpec ecosystem has achieved all of these things by 2020.

Since then, SunSpec has restarted its technical working group to adapt the SunSpec RSD standard to multi-module and string applications. In addition, an online university-level installer training course was developed and is now available at the UC San Diego Extension and North Carolina State University. Finally, SunSpec released a white paper describing the technology and published a state-of-the-art intellectual property study to demonstrate the work on defining an open standard. As a reputable standards development organization seeking a simple, complete solution, SunSpec understands the industry needs transparency and strives for it every day.

SunSpec has gone to great lengths to fulfill its mission of defining open information standards for distributed energy that will expand the market for all parties involved. SunSpec members and the entire DER supply chain expect SunSpec standards to result in solutions that offer lower cost and complexity, shorter installation times, fewer component failures, fewer safety risks for workers, lower overall system costs, a growing number of competing suppliers, and a growing number The market.

Tom Tansy is chairman of the SunSpec Alliance.


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