Solar Reliability: Part IV: How Do We Get There?

The solar industry has grown dramatically over the past three years. In fact, more new solar capacity is added to the grid each year than the capacity added from conventional power sources. This is cause for celebration, but also caution. If these solar installations aren’t reliable, it can stunt the industry’s progress.

“Reliability is a key topic in the solar industry, particularly as we see low-cost products entering the market,” says Henry Dziuba, president and general manager at SMA America. “It affects everyone involved with a project, including owners, integrators and utilities. While each consumer has different reasons for why reliability matters, all are counting on solar installations to be assets rather than a liabilities.”

Out of all system components, Dziuba says inverter selection and application is the greatest determining factor of financial returns.

“A solar array is only as good as its inverter,” he says. “It’s the heart and brains of a PV system because it is responsible for transforming the module-generated electricity into usable AC power. Inverter selection directly affects major levelized cost of energy (LCOE) drivers such as energy production, system cost and operation-and-maintenance costs.”
Many times, solar servicing is in the hands of local owners and operators. Many manufacturers are keeping this in mind as they engineer their products for easier field servicing. Photo courtesy of SMA America.

In the solar industry’s early years, it wasn’t uncommon to have a system with models rated for 30 years, while its inverters were only rated for 5 to 10. But Phil Vyhanek, president of Solectria Renewables, says inverters have come a long way, and most manufacturers offer warranties that cover 10 years or more.

“I think of a PV system like a car,” Vyhanek says. “The system is designed for 20 or more years, a car for 100,000 or more miles. Both, however, require preventative maintenance and sometimes repair. The components that are the most stressed require the most attention: brakes in cars and inverters in PV systems.”
Inverters are arguably the most important installation components with respect to PV system uptime and reliability. Inverters are also the most complex subsystem, and therefore the most challenging when it comes to balancing the demand for solutions that are low-cost and high reliability. Photo courtesy of Solectria Renewables.

Every solar manufacturing company has some reliability issues, Vyhanek adds. He says what really matters is a record of high reliability in the field, and a process for continuous improvement and effective handling of new issues as they appear.

An effective process for handling issues is especially important, say Mark Cerasuolo and Matt James of OutBack Power, because solar does not have a large servicing organization behind it. It’s the power-generating solution that is most in the hands of local owners and operators — including individual businesses and homeowners — so reliability is paramount. Equally important is that engineering inverters for easier field servicing when something does go wrong.

Vyhanek adds that inverter reliability is one of the key criteria that installers, developers and owners consider when selecting equipment because it affects relationships with customers. “The trend is toward more information sharing between manufacturer and customer to validate performance and help with ongoing improvements to inverter quality and reliability,” he says.

Inverter reliability has increased in the last few years, says Bharath Srinivasan, senior vice president of operations at Distributed Sun, which builds and operates solar installations. While long-term warranties for inverters have not yet become a standard, he says accounting for an inverter replacement around year 12 to 15 has satisfied investors. In general, inverter downtime accounts to about 2 to 3 days in each year (about 1% annually) because of problems with inverter electronics or PV-array related problems.

The real challenge lies, Srinivasan adds, in non-standard inverter architecture and design across a manufacturing pool. This means installers and operations-and-maintenance providers must educate themselves on several different software and hardware platforms. In this case, reliability as a concept applies to standard architecture to avoid any field issues during installation. “Reliability can’t be an abstract concept that individual manufacturers live up to, but must be a standard that traverses the entire value chain with clear understanding of the all issues in play,” he says.

Raghu Belur, vice president of products and strategic initiatives at Enphase Energy, says that more reliable products would be better for the industry as a whole.

“It’s critical because, as an industry, if we want achieve our dreams of displacing traditional forms of energy, we will have to provide cheaper, better and more reliable energy to customers,” he says. “If we want to win, we have to meet and ultimately exceed that standard.”

Written by: Kathie Zipp, Managing Editor of Solar Power World Magazine