As commercial and industrial solar grows, Jeff Routledge of Tigo Energy explains the case for including rapid shutdown capabilities as a buttress against disaster.

Module-level power electronics and rapid shutdown are relatively rare subjects in the world of solar PV. Most times projects are described in terms of load, output, export, bill savings and little more.

I came across module-level power electronics (MLPE) and rapid shutdown about eight years ago while working for an Australian solar distributor which at the time was sole distributor for SolarEdge and Tigo Energy products. My previous experience in the UPS industry had instilled in me a very healthy respect for high-voltage DC and the need for good DC safety options such as rapid shutdown.

First, let me explain. MLPE-rapid shutdown is the ability to switch the DC output of individual panels off, rapidly and automatically. For SolarEdge this means 1VDC output per MLPE device, and for Tigo Energy and Enphase this means zero VDC output per MLPE device.

When we started promoting these new MLPE products in Australia, many solar installers made comments like, “We have been doing this for years and solar just works, we do not need online inverter monitoring. And besides, solar systems are safe; you don’t need any additional safety. It’s just a waste of time and money.”

But validation was just around the corner.

That same year NSW was hit by flooding and many towns went under, including Wagga Wagga and Cowra. This prompted the Clean Energy Council to post several warnings to flood-affected areas that for those forced to take shelter on their roof tops fitted with roof top solar, there was a very real danger from high voltage DC that would still be present within the solar array while the sun was shining.

Shocked on top

Today, virtually every inverter sold in Australia has web-based monitoring as standard equipment, or has it available as an option card, and the industry has embraced inverter-level monitoring as valuable.

Significant educational progress has been made in relation to the safety benefits of implementing rapid shutdown, and through the efforts of companies like SolarEdge, Enphase and Tigo Energy market awareness is higher today than it has ever been. But in the commercial space we have not seen the same degree of promotion and uptake of the rapid shutdown standard as we have seen with other new tools such as inverter monitoring. This might be because rapid shutdown is a product that everyone hopes they will never have to use – but it is foolish to ignore its long-term benefits.

Commercial solar customers are very different from residential customers, with different needs and decision-making processes. It seems that many commercial solar companies in Australia do not fully appreciate the long-term value that increased safety (rapid shutdown) and DC safety afford commercial solar customers. Many commercial solar systems are still being sold based on the lowest upfront system price as opposed to the best commercial system design and lowest total cost of ownership.

A good system design will provide commercial customers higher levels of safety, greater bankability, efficient O&M and asset protection and risk mitigation for the businesses in relation to preventing business disruptions.

Around the world many countries – the United States (NEC 609.17), Canada (CSA C22.2 NO. 107.1-01) and Europe (VDE) – have been leading the way in relation to safety and many have begun legislating various forms of rapid shutdown. In Australia we have seen some steps in this direction through the introduction of manual tools like the roof top isolator, but more can be done.

A commercial decision

With energy costs continuing to trend upwards, Australia manufacturers are increasingly looking at ways to become more competitive and efficient with their energy usage; and most are looking for long-term solutions that will enable the business to both fix energy and production costs. For many companies solar PV is becoming a viable option for consideration.

Over the past six years of working in the MLPE space I have been privileged to work on a number of large-scale 1MW-plus commercial solar projects here in Australia and overseas. Many of these projects mandate the integration of rapid shutdown; one was a 1.2MW system installed on a commercial airport in Adelaide and more recently a 1MW system for Finlay Cold Storage in Sri Lanka.

In those examples system safety coupled with the ability to prevent disruption to the daily business operations were key drivers as to why these companies voluntarily adopted rapid shutdown. A simple fault within the DC wiring of the array could result in disruption of business and significant business losses simply because the array’s DC energy could not be switched off.

It happened in February this year when an array fire in Japan resulted in both the loss of the solar asset and the loss of the commercial premises. Firefighters did not contend the array fire because of the risks posed by high-voltage DC, but had the system been equipped with MLPE features like rapid shutdown the outcome most have been very different.

As an industry we need to provide our customers with long-term solutions and partners, not just short-term sales.

Jeff Routledge is Asia-Pacific manager of US-headquartered solar technology company Tigo Energy.