Austin company tweaks solar panels for greater output
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PDFAustin American-Statesman (September 11, 2010) - If solar power is going to fulfill its promise as an important “green” energy source in this country, experts say some technical improvements have to be made.
Several companies are pushing to revamp one key component of a solar power system, something called a power inverter.
It’s a box that takes the direct current produced by solar panels and transforms it into alternating current that is usable inside the home or in the electric power grid.
The challenge for the industry is to make power inverters that last longer, that are cheaper to install and that operate with more efficiency and flexibility.
The traditional approach has been to have one big central inverter that transformed the current from an entire array of solar panels, which could be 20 or more sitting on the roof of a home or business.
The newer approach has been to use smaller devices — called microinverters — that convert the power of a single solar panel.
The advantage is efficiency and “energy harvest.”
A central converter system links panels in a “string” circuit where the performance of the entire system is limited to that of the weakest link.
Microinverters can be wired together in parallel circuits so that each panel can contribute power at its own rate.
The microinverter’s job is simple, but difficult. It must convert electricity from direct to alternating current.
It must monitor the efficiency of the solar panel it works with and adjust to changing conditions such as clouds, shading or even dirt. It must communicate its status to an energy management device that controls an entire system of panels.
And, if there is a problem with sending power to the grid, it has the smarts to shut down power generation to avoid a potential safety problem.
For many microinverters, installation is still costly, because the network of inverters must be installed and inspected before the solar panels are installed.
Austin’s SolarBridge Technologies Inc. has addressed that problem by developing a microinverter that fits into the back of a solar panel, so that both are installed at the same time.
Doing it that way means building an inverter that lasts just as long — 20 to 25 years — as the solar panel does. And that is what SolarBridge says it has done. It is working with panel manufacturers that will install its inverters into their panels at the factory. Its first products will be shipped this fall.
Much of the “smarts” of the solar system on a house or business is tied to a separate power management device that monitors the performance of the entire system and that can pinpoint potential problems.
SolarBridge’s power manager also has the communications circuitry to send its status reports on the performance of the system wirelessly to the homeowner.
Both the homeowner and the system installer can check on the performance of the systems through Web-based software.
“This is all about achieving the vision of grid parity,” said Greg Madianos, the product line director with SolarBridge.
“That means being able to reduce the cost of renewable sources, such as solar, down to a level that is equivalent to fossil fuel sources, including coal, oil and natural gas. This is all a fundamental step forward in making renewable energy from solar cheaper, more reliable and more efficient.”
The microinverter will deliver up to a 30 percent cost savings over the life of a solar power system, according to SolarBridge.
That savings comes from three areas: Installation is dramatically simpler and cheaper because each panel will come with its microinverter pre-installed; reliability goes up because the company has designed its inverters to last the lifetime of the solar panel; and the energy harvest is greater, because each inverter is automatically “tuned” to the operating characteristics of the panel it is paired with.
His company projects that systems using its products will speed the arrival of grid parity by two years.
The company estimates that its system will deliver a 5 percent to 10 percent increase in energy harvest, compared with a central inverter, over the life of the system.
IMS Research, which tracks the solar industry, estimates that more than 16 million microinverters and similar devices will be shipped worldwide in the next five years.
“With any industry growing as rapidly as photovoltaics, there are huge opportunities available,” said IMS analyst Ash Sharma. “Although there was only one supplier shipping any significant volume (California’s Enphase Energy) that is all about to change. Soon more than a dozen suppliers will be serving the growing market.”