The electronics revolution of the past few decades has brought about an increasingly digital society with a critical dependence on electricity. As this dependence, has grown, so too have the needs to generate and use electricity in efficient, environmentally sensitive and economic ways.
A class of chips known as power semiconductors has played a key role in satisfying these needs. Power semiconductors are widely used in all sectors of the economy in equipment for lighting, transportation, industrial, medical and other uses. They have made possible a host of innovative, energy-efficient and versatile products such as compact fluorescent lighting, adjustable-speed electric motor drives and hybrid/electric vehicles.
Power semiconductors are also vital to the success of evolving renewable energy generation and electrical transmission and distribution (T&D) applications. They are the fundamental building blocks of the inverters which convert electricity from solar panels and wind turbines into the voltages and frequencies needed by the power grid, and they help grid operators efficiently control and regulate the flow of electricity across HVDC and other power networks.
From an energy utilization point of view, the positive impact of power semiconductors on society has been enormous. It hasn’t been fully appreciated, though, because these devices are embedded in products and thus largely hidden from the eyes of end-users.
Consider just one type of power semiconductor, the insulated gate bipolar transistor (IGBT). First commercialized in the early 1980s, IGBTs are ideal for many high-current and high-voltage applications because their power-handling capabilities, energy-efficiency and ruggedness give them superior operating characteristics in these applications compared to other power semiconductors or alternative technologies.
According to B. Jayant Baliga, a North Carolina State University professor who developed the IGBT while working at General Electric Co. in Schenectady, NY, IGBT technology has led to the development and widespread use of many innovative products whose reduced energy consumption and lower costs have brought about many societal benefits.
For example, Baliga noted in a paper presented at the 2014 IEEE International Electron Devices Meeting (IEDM) that over the past three decades IGBT technology has led to a worldwide reduction in gasoline consumption of some 1 trillion gallons, and a reduction in electricity consumption of more than 50,000 terawatt-hours. These correspond to 75 trillion pounds of avoided carbon dioxide emissions globally, as well as cost savings to consumers of more than $15 trillion.
For the utility industry, specifically, Baliga says that power savings attributed to the use of energy-efficient IGBTs have enabled utilities to avoid more than $2.8 trillion in capital expenditures globally that otherwise would have been needed to build new power plants.
That’s an enviable track record, but can it continue?
It has to, not only because the world’s population is growing but also because developing economies are moving upmarket. That means the needs to increase efficiency, reduce costs and lessen environmental impacts in the generation, supply and use of electricity are becoming even more important.
However, for all the progress IGBTs have made to date, they are approaching some technological limits. One possible way around this is to make power semiconductors from materials other than silicon, the base material not just for IGBTs but for most of today’s chips.
Power semiconductors made from so-called wide bandgap materials such as silicon carbide, gallium arsenide and gallium nitride can operate at higher voltages, frequencies and temperatures than their silicon counterparts. This means that greater power-handling capabilities, significant increases in energy efficiency and reductions in equipment size, weight and cost are possible.
Although they are more difficult to work with than silicon, and manufacturing economies of scale are not yet in place to the same degree as they are for silicon chips, momentum is building to develop wide bandgap semiconductor devices.
A case in point is the recently announced collaboration between GE and Danfoss Silicon Power to produce silicon-carbide power modules in Utica, NY for solar inverters and other applications. The collaboration is under the auspices of the New York Power Electronics Manufacturing Consortium (NY-PEMC), a public-private partnership established by the state.
It exemplifies the development work that needs to be undertaken if power semiconductors are to continue playing such an important role. As GE Global Research Vice President Danielle Merfeld put it, the collaboration “will usher in the next revolution in power.”
— by Gary Dagastine, energy writer