Efficiency is a ubiquitous term in the solar industry and an important one — better efficiency means more power, which is what the world needs. But the levelized cost of energy (LCOE) is a truer measure of project value, and there are a variety of ways manufacturers up and down the supply chain are working to push LCOE down. Inverter selection plays a huge part in a system’s LCOE as it effects the lifetime planning and performance of PV systems.
Operations and maintenance functionality in PV inverters is basically a given now, with many including enhanced monitoring capabilities. Inverters can now provide module-level monitoring, sometimes cloud-based, and offer a glimpse not just at PV system production but energy consumption and the status of the system battery. This allows for remote troubleshooting.
Microinverters in particular are well equipped for keeping LCOE as low as possible over time. APsystems uses what it calls the Field-Programmable Gate Array (FPGA) chip to handle the constant DC-to-AC conversion, which is easily reprogrammed to modify and/or enhance its capabilities to meet new demands or work in new environments, without redesigning and replacing the chip itself. This type of architecture then simplifies the surrounding topology because more functions can be carried out within the FPGA processor, which means fewer purpose-built components are required elsewhere within the device.
Because the FPGA chip does so much work within the unit, APsystems microinverters have about 30 percent fewer discrete internal components than is standard. Fewer components means fewer points of failure.
“The FPGA architecture allows multiple, distinct processes to run in parallel on the same chip,” says Christopher Barrett, director of technical services at APsystems. “This cuts down significantly on the number of internal components. This again is a significant savings at the supply-chain level as fewer components must be sourced to manufacture each unit, while also gaining an increase in reliability.”
DC optimized inverters have also entered the mix in order to increase energy production throughout the system by improving system uptime and energy harvest.
“While the inverter may have an upfront cost of only about 10 percent of the system cost, it influences about 30 percent of system cost — eBOS, inverter, labor — and controls O&M expenses,” says Lior Handelsman, VP of marketing and product strategy at SolarEdge. The SolarEdge DC optimized inverter with longer strings and maximum design flexibility is able to significantly increase string length, thus decreasing BOS costs. Microinverters and optimizers also have the benefit of panel-level monitoring, which provides a clearer snapshot of system performance at any given time.
The Enphase Microinverter System competes on an LCOE basis due to higher production, robust reliability and remote monitoring and maintenance, but Teff Reed, senior director of microinverter systems for Enphase says their “product roadmap will drive costs down even further by integrating new technology and materials and simplifying the installation process for installers.”
With the industry heading in the direction of self-consumption and energy storage, SolarEdge’s StorEdge solution is an all-in-one solution that uses a single on-grid DC optimized inverter to manage and monitor both solar generation and energy storage.
“It is with the help of inverters that a PV system can transform into a smart system, which measures, displays, monitors and manages the system’s performance,” Handelsman says. “As part of its smart energy management solutions, SolarEdge’s DC optimized inverter offers a feed-in limitation feature, which limits export power to the grid to allow system owners to install larger PV systems.”
Reliability plays its part in the LCOE equation, especially as many older PV systems are reporting inverter failures the last year or so. A better performing inverter will avoid those performance issues and require less maintenance. Many manufacturers extensively test their products during the development stages and production process, beyond code and standard requirements, to achieve that reliability. But things happen, in which case a company like Fronius will offer a field serviceable option that reduces overall O&M costs and potentially save on downtime significantly.
“Often when performing LCOE calculation, a very detailed look at inverter replacement costs is not taken,” says Tristan Kreager, director of Solar Energy for Fronius. This point of view factors into why it has chosen not to manufacture microinverers, instead focusing on field serviceability. “There could be wide-ranging differences in replacement or repair costs depending on the type of inverter chosen.”
With a typical inverter warranty being half the life of the system warranty, these end-of-life replacement costs need to be considered.
Multiple inverter vendors have exited during the solar industry’s rise; some that were dominant players. This, in turn, left stranded assets — gigawatts worth. Due to this issue, customers have become much more savvy about selecting vendors that not only provide a sound technical solution, but also demonstrate corporate profitability and bankability.
Choosing a lesser known, newer option could leave a project with bigger problems down the road. CPS America’s parent company, Chint, for example, is a $5 billion group of energy-centric companies with supply chain scale economies and supplier roots in Asia. These attributes enable the lowest cost from a diversified and bankable company.
“Inverter costs are 90 percent related to the supply chain, so Chint is optimized for cost efficiency,” says Ed Heacox, GM, sales and marketing for CPS Americas.
And now that the ITC has been extended, 2016 should mark officially when solar stops being an “only child,” as Reed from Enphase phrased it, and that transition is made possible through inverter innovations.
“We see solar making a fundamental move from being energy generation hardware to being a seamlessly integrated part of an energy solution,” he says. “While the move was started by the inclusion of monitoring and control software, the emergence of storage and the Internet of Things is speeding up the transition. The result will be a fundamental change in how the energy is stored, generated and consumed.”
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