By John Palmour
Solar power generation has experienced rapid growth over the past several years. Net solar power generation reached its highest levels in the U.S. - 66.6 gigawatt-hours in 2018, compared to just two gigawatt-hours in 2011. During this period of growth, a robust alternative has emerged that challenges the more traditional semiconductor material of silicon: silicon carbide. Silicon carbide significantly increases the sustainability of renewable energy, resulting in lighter, smaller, and more efficient solar inverters.
As the demand for technology supports the increased use of sustainable resources, we need to be sustainable in the way we transmit and transform that power. Silicon carbide power components are well positioned to increase the sustainability of renewable power, as well as the technology that makes it possible.
Benefits of Silicon Carbide
The power semiconductor space is in the midst of a major transition, as it moves from silicon-based technologies to silicon carbide. This yields major benefits for a number of industries. From a scientific perspective, silicon and carbon create very strong covalent bonds, and this bond strength is key in allowing much higher breakdown to the electric field and higher thermal conductivity.
Silicon is the most common semiconductor used today. Silicon carbide, on the other hand, is considered a wide bandgap semiconductor. This distinction allows devices using silicon carbide to operate at much higher voltages, power densities, and temperatures, making silicon carbide ideal for the increased performance demands of next-generation applications. Silicon carbide also offers significantly lower switching losses than silicon, leading to much higher efficiency.
The proven performance of silicon carbide is powering new sectors and reviving established ones. For example, when looking at the impact on electric vehicles, using silicon carbide can increase the range of that vehicle by 5-10 percent, or enable manufacturers to use 5-10 percent fewer batteries for the same range. These numbers are significant to say the least. In industrial applications, silicon carbide power devices can increase efficiency, shrink system size, and reduce heat dissipation, helping businesses make the most out of every kilowatt hour of electricity and every square meter of floor space.
Implications for Sustainable Solar Power Design
A solar panel’s semiconductors absorb sunlight and convert it to electricity; however, they are not particularly efficient in doing so. That makes every watt generated precious. In the process of converting that power into a usable form from the solar panel to the grid or load, you want to keep every bit of energy. Fortunately, the same benefits of silicon carbide highlighted above also apply to solar power systems, with the potential to enable 98 percent efficiency of that power to be converted - even with varying temperature, humidity, harsh, or remote environments.
The technology also positively impacts the sustainability of solar power generation design, specifically that of highly efficient solar inverters for residential use. These inverters can operate at much higher frequencies, resulting in a dramatic shrink in the size and cost of the magnetics required, along with an overall decrease in system cost. For example, using silicon carbide power components instead of silicon for solar inverters can save 10 megawatts for each gigawatt and 500 watts/sec in operations - significant energy savings.
Taking it a step further, 650V silicon carbide Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) - which are commonly used for power conversion in electronic systems - can increase the efficiency of solar power systems. When compared to silicon, for instance, 650V silicon carbide MOSFETs require fewer components, have a smaller footprint, and a lighter weight. They lower switching losses by up to 75 percent, enabling higher efficiencies at higher frequencies, while allowing up to 70 percent greater power density and vastly improved thermal performance. Again, all at a lower system cost. 650V MOSFETs are also targeted to make highly compact and efficient switch-mode power supplies for servers, which will reduce the large amount of energy wasted in large data farms.
The benefits of silicon carbide can be used strategically for everything from utility-scale solar farms to solar panel chargers for electric vehicles in the home. Compared to silicon alternatives, silicon carbide enables smaller, faster, lighter, and more efficient systems across all applications. The technology has a positive impact on the sustainability of solar power generation design, paving the way for the next generation of renewable energy systems, and creating the road to a greener, more secure energy future.
John Palmour is CTO at Cree, a semiconductor company focused on silicon carbide and GaN technologies.