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Bristol set to supercharge growth of next generation zero carbon emission technology

Image shows the heart of the reactor within the Metal Organic Chemical Vapour Deposition (MOCVD) machine. This is where the heated substrate is placed, forming the base on which Gallium Oxide is grown. Cohen Rautenkranz, Agnitron Technology

Image shows the outside of the MOCVD machine. The processes are monitored by computers; temperatures and gas flows are controlled. Prof Martin Kuball

27 April 2022

Power transformers currently the size of shipping containers delivering energy to homes and businesses across the UK could be shrunk to the size of a suitcase, thanks to a pioneering process which deploys a new supercharged material with unprecedented levels of efficiency.

The industry-changing technique is being developed at the University of Bristol at a time when the need to reduce energy consumption has never been greater, as the drive to cut carbon emissions intensifies and fuel costs soar.

A team of leading scientists have just installed the UK’s first-ever machine to make layers of Gallium Oxide, the wonder semiconductor which forms the crucial component of future revolutionary power devices with the potential to cut overall energy usage by around 20% in both domestic and industrial settings.

Most power converters and electricity supplies function by converting an AC voltage to another AC voltage, or an AC voltage to a DC voltage or vice-versa. This is the case with wider energy distribution networks, such as power lines, as well as when plugging in electrical devices. Traditional transformers can be heavy, metal-based and inefficient due to the excess heat generated in the process, whereas more modern energy converting circuits are mostly made of more common Silicon (Si) semiconductor components.

In recent years significant advances have been made to replace the Silicon-based power electronics   with new devices made of so-called wide bandgap semiconductors. This makes them much smaller and more efficient, for instance electric cars and laptop chargers use components made of low-loss semiconductors Gallium Nitride (GaN) or Silicon Carbide (SiC).

But challenges remain to successfully convert high voltages cost-effectively with minimum energy loss. This includes replacing old and bulky metal-based transformers located in neighbourhoods down to the common mains electricity voltage from sockets at home. There are also still significant inefficiencies with even modern semiconductor-based converters with Silicon components which, for example, feed in energy from solar plants into the national grid.

The university’s new Metal Organic Chemical Vapour Deposition (MOCVD) machine, which can grow then next generation semiconductor Gallium Oxide, presents a compelling solution to this problem.

Project lead Martin Kuball, Professor of Physics and Royal Academy of Engineering Chair in Emerging Technologies, said: “This is a hugely exciting and urgently needed opportunity. With the push to introduce more efficient power electronics and advanced renewable technologies amidst the pressing climate crisis, this presents a game changer for more sustainable and affordable future energy supply.

“At present nearly three-quarters (72%) of global primary energy consumption is wasted. While most low-carbon technology still relies on Silicon-based electronic devices, we are slowly starting to see this replaced with semiconductors made from Gallium Nitride and Silicon Carbide. As action to reduce our carbon footprint accelerates, a stronger focus on developing devices based on Gallium Oxide must happen and we are committed to progressing this at scale and speed.”

The 20-strong team of researchers is collaborating with other groups across the globe including in Japan, the United States, and Germany, as well as industry partners such as Dynex Semiconductors. Funded in part by the Royal Academy of Engineering, the Gallium Oxide MOCVD system from Agnitron Technology in the US is the first of its kind in Europe.

“The MOCVD system will be used to grow thin layers, much thinner than a human hair, of Gallium Oxide as well as Aluminium Gallium Oxide, in a chamber containing highly purified gases. These layers then go into our clean room, an almost entirely dust-free area, where metals and other layers are added, effectively electrical contact, to produce the finished power electronic component which is ready to use. These are even more energy efficient than current GaN and SiC components,” Professor Kuball explained.

“We will be activating the machine this month and aim to have our first Gallium Oxide-based components within the next few months, putting us at the very forefront of making energy efficient power devices of the future.”

The technology not only means power distribution networks will waste much less energy, but they could also look very different.

Professor Kuball said: “Existing power converting units, often found in our streets, are container-size. Taking this technology to the next level could see them reduced to the size of a suitcase. You could then build distributed power networks, or smart grids, because the compact proportions make it possible to have more of them widely distributed. This would lower the risk of power outages for large parts of the town or city, as is presently the case when a power line goes down. The advantages of Gallium Oxide-based technology are vast. Now more than ever we must develop and refine the processes to fully realise this.”

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