SiC Shines a Light on Solar Power

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The technology of solar power generation has improved steadily year-on-year, while prices have fallen dramatically. Solar PV is also a scalable technology that can be manufactured in high volumes, enabling rapid deployment and economies of scale.

Manufacturers are continuing to invest heavily in developing more efficient PV technology, enabling solar cells to capture more of the sun’s energy. While the market has been dominated by passivated emitter and rear contact (PERC) and passivated emitter, rear totally-diffused (PERT) panels, the industry is shifting to the newer, tunnel oxide passivated contact (TOPCon) technology, which promises higher efficiency at a competitive cost.

As well as the panels themselves, it’s vital that all the power electronics involved in solar energy generation are as efficient as possible. The key component is the inverter, which takes the DC generated by the solar panels and converts it to AC that can be fed back to the grid or used to drive local loads.

Research is focussed on improving inverter efficiency, as well as developing smarter inverters that integrate with a smart grid: to help balance supply and demand, and to handle ‘Dunkelflaute’ events when the wind doesn’t blow and the sun doesn’t shine.

Wide bandgap efficiencies in solar PV systems

An inverter in a solar PV system is based around a switching power device, which has traditionally meant a silicon MOSFET or IGBT. Over the years, there have been continued improvements in these devices, but the industry is now reaching the physical limits of silicon as a material – which means that to further improve efficiency, we need to look elsewhere.

The answer is silicon carbide (SiC), a wide bandgap (WBG) semiconductor that has some key advantages over silicon. Most importantly, SiC can switch faster than silicon, reducing switching losses and thus improving efficiency in power conversion devices such as an inverter. SiC MOSFETs deliver lower turn-on, turn-off, and conduction losses than equivalent silicon MOSFETs, which means their overall losses are over 60% lower.

SiC devices can also handle higher temperatures and voltages better than silicon, and have superior thermal properties, enabling them to dissipate heat more effectively. Additionally, SiC’s higher efficiency means it generates less waste heat than silicon, so heat sinks can be smaller, reducing overall equipment size and decreasing cost.

For small-scale solar PV systems, such as on homes and commercial buildings, another good option, in theory, is gallium nitride (GaN). This would provide higher switching speeds again, such as up to circa 300 kHz in a solar inverter application. The higher frequencies mean that output filters can be smaller, leading to a more compact design with higher efficiency than silicon.