- Category: Technology
20 Aug 2009
- Published on Thursday, 20 August 2009 10:06
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Inverter with an efficiency exceeding 99%. Photo from the Fraunhofer Institute for Solar Energy Systems ISE
The Fraunhofer Institute for Solar Energy Systems ISE has set a new world record of 99.03% efficiency of inverters used in photovoltaic (PV) systems.
Inverters convert direct current or DC electricity generated by PV systems into alternating current or AC, the kind distributed to users from the grid. Higher inverter efficiency means higher system yield.
“We now use junction field-effect transistors made of silicon carbide (SiC) manufactured by SemiSouth Laboratories Inc. This is the main reason for the improvement,” explained Bruno Burger, a professor and the leader of the Power Electronics Group at Fraunhofer ISE. “In addition, we have optimized the gate units and many other details of the circuit.”
SemiSouth Laboratories is an American firm with offices in Austin, Texas and Starkville, Mississippi.
SiC transistors are significantly better than the conventional insulated gate bipolar transistor of silicon used commonly today, particularly for higher reverse voltages. The main reasons are the breakdown field strength, which is ten times higher for SiC than silicon, and the band gap, which is three times larger for SiC than silicon.
By using new components and improving the circuit technology, the researchers reduced losses compared with their own previous top-level performance by a further third.
Further advantages result when the improvements are transferred to series production: higher efficiency means lower thermal losses, smaller cooling devices and a more compact construction.
The next steps toward application in series production include further testing of the components and adaptation of the circuits and switching frequencies to the new specifications. Finally, field tests are planned to demonstrate viability in practice.
The work to improve the inverter efficiency was supported by the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU) within the project entitled “Ultra-compact PV inverters with silicon carbide semiconductors and high efficiency values.”
- Katrice R. Jalbuena