Emcore inks PV supply deal, SemiSouth improves solar inverter efficiency

In addition to its purchase of more of Intel Corp’s optical business this past week, Albuquerque, NM-based Emcore Corp inked a supply agreement for concentrator photovoltaic (CPV) systems to China energy company XinAo Group.

Under the agreement, Emcore will first deliver a 50 kilowatt (kW) CPV system to be installed in Langfang, China, which will be used for test and evaluation purposes. Then, once the expected reliability and performance metrics have been met, XinAo said it would install CPV systems to provide electric power for its coal gasification project — estimated to have a requirement of 60 megawatts (MW) of power.

XinAo also said it plans to build a manufacturing plant in China, to be jointly owned by Emcore, which will manufacture CPV systems designed and certified by Emcore for the Chinese market.

In other photovoltaic news, Austin, Texas-based silicon carbide (SiC) based semiconductor company SemiSouth Laboratories Inc and the Center for Advanced Vehicle Systems (CAVS) at Mississippi State University reported late last week that SemiSouth’s enhancement-mode silicon carbide (SiC) junction field effect transistor (JFET) improved the efficiency of an off-the-shelf inverter commonly used in residential and commercial solar power energy systems.

CAVS noted that it guided the work and provided precision test equipment to measure and validate the efficiency improvement, and said that by replacing the existing silicon transistors with SemiSouth’s enhancement-mode SiC JFETs, the inverter reduced losses in the power semiconductors by as much as 50%.

Also, CAVS said it used the JFETs as “drop-in” replacements for the silicon devices, making no design changes to the inverter before inserting the SemiSouth components, and explained that the grid connected, low-frequency isolated inverter, purchased from commercial inventory of a leading solar inverter provider, was designed with conventional silicon insulated gate bipolar transistors (IGBTs).

Dr. Rand German, director of CAVS and professor of mechanical engineering at MSU, commented in a statement, “CAVS is putting a major emphasis on positioning itself for a lead in automotive power electronics R&D. This result validates our belief that developing and testing applications for silicon carbide power electronics through our partnership with SemiSouth is leading to breakthroughs in energy efficiency.”

Beyond the reduction in conduction and switching losses, SemiSouth said the use of SiC JFETs as drop-in replacements to achieve the efficiency gains is unprecedented, as explained by Robin Kelley, applications engineer for SemiSouth. “All that was necessary to drop-in the enhancement-mode JFETs was the addition of a few passive components in the control circuit to take into consideration the change in threshold voltage between the original IGBTs and these JFETs. We started the inverter and it ran without any problems,” Kelley said.

With this change, the company noted immediate improvement with respect to performance and efficiency, which opens the door for additional modification to fully take advantage of the SemiSouth device that is expected to yield improvements in performance and efficiency, as well as overall system reliability.

Further, SemiSouth said the enhancement-mode SiC JFET is cheaper to produce, smaller than any comparable silicon or silicon-carbide transistor, and free of reliability concerns with gate-oxides that have plagued more conventional approaches to develop an enhancement-mode field effect transistor using silicon carbide.

The JFET can be used as a direct replacement for silicon MOSFETs and IGBTs in virtually any off-the-shelf converter or inverter design.

Vess Johnson, SemiSouth’s president and CEO concluded, “The fact that the JFETs can be used as a drop-in replacement means that the barrier to entry has been greatly reduced and that designers working with these devices will be able to see immediate performance and efficiency improvements and will be able to drive new and better products to market much faster.”

–Ann Steffora Mutschler, Senior Editor