The National Renewable Energy Laboratory’s “Little Box Challenge” — a competition designed to spur the creation of smaller inverters for use in interconnecting solar energy systems to the power grid — has been won by Belgium’s Red Electrical Devils (a team from CE+T Power), according to a recent announcement from Google and IEEE.
The win nets the research team $1 million in prize money for its work to show that “inverters can be the size of a tablet or smaller rather than the size of a picnic cooler.”
The winner of the competition was selected following testing and analysis of the various submissions at The Energy Department’s National Renewable Energy Laboratory’s (NREL) campus in Golden, Colorado. Submissions were brought to the Energy Systems Integration Facility (ESIF) in Golden back in late-October 2015.
“The overall idea was to test these inverters in a similar fashion to how they would be used out in the field,” stated Blake Lundstrom, the NREL project lead.
Here’s more via an email sent to CleanTechnica:
The first step was to verify that the inverters met all critical safety-related specifications and then to simply turn the inverters on and see if they functioned. Next, was a three-hour procedure to operate the inverters at a number of different operating points and to verify that key specifications were met throughout the three hours. After these challenges, the field of eighteen finalists was narrowed to the remaining inverters that would proceed to the third round.
Those final inverters were subjected to a 100-hour simulation of real-life conditions, including a direct-current source of electricity that emulated a solar power system, with rapid ramp-ups and ramp-downs in power typical of an intermittently cloudy day, as well as a realistic, changing load typical of a residence that the inverter needed to supply. Each inverter had to meet most of the same specifications required of commercially-available inverters.
“We were checking that all the specifications were met, under realistic conditions that a similar solar inverter in the field would experience, and evaluating their thermal performance over the long term — those are the key things that we were looking for over those 100 hours,” continued Lundstrom.
Following review by judges from Google, the IEEE Power Electronics Society, and NREL, the Red Electrical Devils were unanimously selected as the winner.
Their inverter had a power density of 143 W/in3-far greater than the minimum requirement of 50 W/in3 and 50% higher than the nearest competitor-and a volume of only 14 cubic inches, smaller in volume than a cube measuring 2.5 inches on each side. The winning inverter also performed better on measurements of electromagnetic compliance (the amount of electrical noise emitted from the unit).
Shrinking inverters by an order of magnitude and making them cheaper to produce and install will enable more solar-powered homes and more efficient distribution grids, while helping bring electricity to remote areas. A key factor in the winning inverters was the use of wide bandgap semiconductors, a technology that enables power electronics to operate at higher voltages and temperatures, allowing them to transmit more energy through a smaller volume.
“Wide bandgaps offer a lot of advantages over traditional silicon that enabled teams to hit some of the miniaturization and efficiency targets that were needed to be successful in the competition,” noted Lundstrom. “Not every single team used wide-bandgap devices, but the vast majority did.”
“The Little Box Challenge actually forced people to try to optimize space, and a nice outcome of that is that some of the techniques to do that are going to be pretty helpful for other aspects of inverter development,” concluded Lundstrom. “For example, once you have a device that is almost entirely integrated onto a printed circuit board, it’s easier to manufacture. Plus, some of the teams were able to incorporate all this innovation without adding any additional cost to the inverter and in some cases these designs may result in reduced inverter cost when mass-produced.”
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