After years of incremental advances, a variety of innovations both simple and exotic are promising to boost the output of solar photovoltaic (PV) systems as much as 30% over current technologies—if the market can be convinced to adopt them.
The Dawn of SiC
For a generation, silicon has been the go-to material for semiconductor substrates. It’s difficult to manufacture in the purity required and comes with a variety of limitations, but so far nothing else could match it for economics. That may finally be changing if GE has its way.
At the Solar Power International (SPI) exhibition in Las Vegas September 13, GE announced that it was introducing a solar inverter using a silicon carbide–based chip. Silicon carbide (SiC), a ceramic compound composed of silicon and carbon, has been manufactured for industrial use for more than 100 years but is only just beginning to see use in electronics.
SiC has significant advantages over crystalline silicon. SiC-based chips can operate at much higher temperatures and frequencies and are far more rugged—they can operate at twice the power density of a Si-based chip. This makes them ideal for high-power devices like inverters because they can convert power at higher efficiencies and lower losses, Keith Longtin, product breakout lab director for GE Global Research told POWER.
“This allows us to switch up to 10 times faster, which gives us a much cleaner signal,” he said.
The SiC inverter chip forms the core of GE’s LV5+ Solar Inverter, also announced at SPI, which it estimates can deliver around $2.5 million more revenue over the life of a typical 100-MW solar plant (Figure 1).
GE has been working with the State University of New York College of Nanoscale Science and Engineering in Albany to build a fabrication line for manufacturing SiC power devices. To scale up the technology and reduce fabrication costs, manufacturing must move from the current industry standard of 4-inch wafer production to 6-inch wafers. The Albany facility will be set up for 6-inch wafer production.
Dual-Axis Tracking Comes to Rooftops
Dual-axis tracking has been recognized for some time as a method to boost PV capacity factors, especially in areas with less-than-optimal insolation. Tracking systems also have much flatter output profiles because they collect sunlight more efficiently when the sun is lower in the sky at the beginning and end of the day.
But the mechanical supports necessary to implement dual-axis tracking have thus far restricted such systems to ground mounting, because they’re much too heavy for rooftop use. Among other problems, this greatly reduces opportunities for use in urban areas.
A remarkably simple design called the PV Booster from Pasadena, Calif.–based Edisun Microgrids may change all that, however.
The PV Booster mounts a standard PV panel on a lightweight pivoting frame that keeps the panel pointed directly at the sun. Because the mounting is so light, it’s able to use a direct-drive design and brushless motor rather than needing a gearbox (Figure 2). That makes it light enough to mount on a roof and substantially reduces maintenance issues. The panels also move individually so each maintains its own optimal orientation toward the sun rather than being centrally controlled.
Designed for commercial and industrial rooftop use, the PV Booster can deliver as much as 30% more power for only a slight increase in cost, Edisun CEO Bill Gross told POWER. Consequently, system returns using the PVBooster are estimated at 20% higher than conventional mountings.
The system can also be installed on carports using specially designed mountings that employ truss supports rather than conventional carport mounts. Because the design uses substantially less steel, it’s cheap enough that the efficiency boost provided by dual-axis tracking can pay for the carport installation.
“We make carports cheaper than rooftop solar,” he said.
Gross said Edisun has a test installation operating at its location in Pasadena and is in discussions with customers for the first commercial installations.
More Solar Technology Funding on the Way
If the Department of Energy (DOE) has anything to say about it, there will be more such developments over the next few years. The DOE’s SunShot Initiative, which is intended to drive down the levelized cost of PV generation, announced another round of funding at SPI.
Operating under the DOE’s Office of Energy Efficiency and Renewable Energy, the latest round will fund 40 projects with a total of $42 million to improve PV performance, reliability, manufacturability and enable greater market penetration for solar technologies. In addition, the DOE said it hopes to provide $65 million in additional funding (subject to appropriation) for upcoming solar research and development projects to continue driving down the cost of solar energy and accelerating widespread national deployment.
The 40 projects include 19 that will receive a total of $17 million to “advance next generation solar technology,” most of them in academia, and 21 that will receive a total of $25 million for “development of new tools, technologies and services for the solar industry.” Those latter awards support several advanced analytical tools for locating optimal sites for solar and solar-plus-storage projects.
One of these tools, created by San Francisco firm Kevala Analytics, maps locations of wholesale price nodes and substation locations together with historical data for insolation, weather, and price fluctuations. Kevala CEO Aram Shumavon said in a statement announcing the award, “Instead of searching an entire territory or region, we can help developers find the best locations in a few clicks.”
SunShot Initiative Director Charlie Gay told POWER in an interview that tools like this offer enormous potential for advancing the role of PV in the grid, not just for developers but for utilities as well. Advances in cloud computing and data storage capabilities, he said, means “being able to leverage a massively parallel network of servers to address problems in mapping the distribution network in a given area” and anticipating changes and challenges before they occur.
“The utility can anticipate that they need to make adjustments in this load center or this substation to handle the change in that area,” he noted, and that kind of interaction “can create opportunities to greatly improve long-range planning” and maximize the value of existing assets.
The funding announced on Sept. 14 is on top of the $59 million awarded in early 2015.
—Thomas W. Overton, JD is a POWER associate editor (@thomas_overton, @POWERmagazine).
[9/15: Updated with comments from Charlie Gay of DOE.]