Google and the IEEE have launched the Littlebox Challenge—an open competition to design and build a small kW-scale inverter with the highest power density (of at least 50 W/in3, or 3.05 kW/L) in an enclosure of less than 40 in3 in volume (0.66L). The winning inverter, which will receive a $1-million prize, will be the unit which achieves the highest power density while meeting the required specifications under testing for 100 hours. In the event of a tie on volume, efficiency will be used to determine the grand prize winner. The grand prize winner will be announced sometime in January, 2016.
Google and IEEE are emphasizing size reduction in their challenge, without targeting a specific application area such as automotive. As a few points of comparison, the Bosch INVCON 2.3 inverter used in the Fiat 500e has a volume of about 5 liters, while the motor inverter used in the 2010 Prius drivetrain has a volume of about 5.4L (according to a DOE deconstruction.) The peak power density of the 2010 Prius motor inverter is 11.1 kW/L (while the peak PD for the Lexus 600h 6.4-liter unit reaches up to 17.2 kW/L.)
(In its efforts to encourage the development of next-generation inverter technologies for vehicles, DOE is emphasizing a balance of cost, power density, specific power, and efficiency. For example, GM is leading a DOE funded project for a next-generation inverter targeting improving costs to $3.30/kW produced in quantities of 100,000 units; power density to 13.4kW/l; specific power to 14.1kW/kg, and an efficiency >94% (10%-100% speed at 20% rated torque) to meet the DOE 2020 goals.)
We believe that inverters will become increasingly important to our economy and environment as solar PV, batteries, and similar power sources continue their rapid growth. More broadly, similar forms of power electronics are everywhere: in laptops, phones, motors drives, electric vehicles, wind turbines, to give just a few examples. We expect that the innovations inspired by this prize will have wide applicability across these areas, increasing efficiency, driving down costs, and opening up new uses cases that we can’t imagine today. It also doesn’t hurt that many of these improvements could make our data centers run more safely and efficiently.—Google FAQ on the challenge
Applicants must register their team by 30 September 2014. Eligible academics interested in pursuing grant funding must apply by 30 September. Registered teams must submit a technical approach and testing application by 22 July 2015.
Up to 18 finalists will be notified of their selection for final testing at the testing facility. They are required to bring their inverters in person to a testing facility in United States by 21 October 2015.
To be considered for testing, participants in the competition must submit a technical approach document not to exceed 4 pages. The document should describe at a high level what approach and innovations the team are using to achieve the high power densities claimed for their inverters. A 1-page appendix with biographical information about the key team members must also be included.
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Google will make public a subset of the technical approach documents; the level of detail required in the technical approach document is meant to be high-level and not divulge any trade secrets. The content and descriptions of the device should be comparable to a short IEEE paper meant to explain conceptually how a new device can work without revealing all the details about the exact values of components used, nor going into details about the control algorithms and other more detailed aspects. General guidelines include:
Power density achieved: the volume of the rectangular enclosure used and thus the resulting power density achieved at a load of 2 kVA should be specified.
Switch level schematics: schematics should be detailed enough to reveal what general topology is being used, but not include every passive component or other circuit detail.
Order of magnitude passive component values: For passive components which typically take up a large volume, or are otherwise critical to the the conceptual design of the circuit, an order of magnitude value for what was used (e.g. 10s of microfarads vs. 100s of microfarads) is acceptable.
Order of magnitude frequency values: For switching frequencies used in creating an alternating current output from a direct current through a pulsewidth modulation or other technique, specifying the order of magnitude of frequency used (e.g. 10s of kilohertz vs. 100s of kilohertz) is acceptable.
Semiconductor device type(s): Participants should specify the type of semiconductor switching devices that they are using (e.g. silicon, galliumnitride, siliconcarbide, etc.). Participants may or may not specify the vendors and providers of these semiconductor switching devices at their discretion. The same is true of any novel passive components used.
Teams should also provide clearly indicated sections on what innovations they have used to confront challenges including: the 120 Hz input current/voltage ripple requirement; miniaturization of components for DCAC conversion; thermal management; and electromagnetic compliance.