Power electronics driving new demand for metals

Advances in a technology that underpins the consumption, distribution and increasingly the generation of electricity is driving demand for new types of microchips that combine silicon with carbon and electronic metal gallium.

"When we think about digital, the digital age, we are usually thinking about the processing of communications and data and performing calculations. But there is another important area, the control of power," the University of Edinburgh's chair of power electronics, professor Stephen Finney, said.

Huge systems such as interconnectors that connect the power grids of different countries, factories, a mobile phone or a single LED light bulb all rely on microchip systems that can control, measure and convert electricity. More than 80pc of the energy generated globally passes through some kind of power electronics. Hidden away from view in grid infrastructure and inside devices and machines, many people are unaware of the technology.

"All those packets of biscuits we ate during lockdown, they were made using power electronics," UK Research and Innovation's Challenge Director - Driving the Electric Revolution, professor Will Drury, said. "The most efficient and often the only way to run a machine is to alter the amount and form of electricity it receives. And data centres consume an awful lot of power and need power electronics to make them affordable to operate."

A mobile phone is a mini-power system. The direct current (DC) battery is charged from a 50Hz alternating current (AC) grid and different voltages are needed for different components.

"If you wonder why the power supply for your laptop or mobile phone charger is much smaller today, it is because people have got better at building the power electronics in it. And more change is coming," Finney said.

Generation gap

Electricity in the 1950s was largely generated from rotating turbines. By controlling the amount of fuel and regulating the speed, it produced a fixed frequency AC grid. "Now we are talking gigawatts of wind power and significant amounts of photovoltaic," Finney said. "We need to capture the maximum amount of energy from what is available. We need power electronics to connect up offshore wind and use high voltage DC to transport electricity over longer distances and connect national grids for pooling," he said.

Changes in the way electricity is produced and consumed will require solid-state (semiconductor) substations and transformers and smart grids that relay information and use temporary storage. The question for the UK is whether it imports this technology or seeks to manufacture some of its own.

All of these advances will also require new materials. Conventionally, silicon was used for power electronics, but as the demands increased, scientists and engineers began to look to new materials — compound semiconductors. In a compound semiconductor, the wafer is made of two or more elements chemically combined in an ultra-high purity crystal lattice. This combination makes it possible to obtain some important properties. Silicon carbide — silicon combined with carbon — and gallium nitride — gallium and nitrogen — are what is known as wide-bandgap semiconductors. This means that they handle much higher voltages than silicon, which is why they are so important to power electronics and essential for the growing electric vehicle industry.

"There is an opportunity in automotive semiconductors, which is why we need to keep investing," Drury said. The UK has a long history in power electronics — a company in Wales has been making industrial drives — power electronics converters attached to motors — since the 1970s. The UK government launched a power electronics strategy in 2011 looking at key growth areas, followed in August 2019 by the launch of the Driving the Electric Revolution Challenge with funding of £80mn ($110mn) from the Industrial Strategy Challenge Fund (ISCF). The goal is to make the UK a global leader in the manufacture of the core technologies that support electrification — power electronics, electric machines and drives (PEMD) and accelerate supply chain development. So far the ISCF has invested £33mn in four industrialisation centres, designed to support research and development in the UK by enabling businesses and researchers to develop and scale new PEMD technologies and manufacturing processes. It has also provided around £40mn in funding to over 40 projects from wind turbine generators to electric propulsion for boats, and from electric hub motors for farm vehicles to nuclear coolant system components.

Net zero race

"Power electronics is a race to cope with increasing electricity consumption," Drury said. "We cannot achieve net zero without power electronics," he said.

Power electronics is a technology of the future. As all industries push to increase energy efficiency and reduce CO2 emissions, power electronics will play a key role.

By Caroline Messecar