Capacitors are a means of storing energy and are vital to the process of converting DC power from the vehicle battery, into AC power required to drive the motor. However, most current capacitors do not meet EV requirements, due to an inability to function reliably under the high temperatures created in electric vehicles. Up till now the absence of suitable capacitors is one of the major barriers to meeting an important EV goal – that of representing more than 50 per cent of worldwide light duty vehicle sales by 2050.
NPL says that it has overcome this issue by creating the HITECA capacitor, which can operate close to normal efficiency at over 200°C, significantly higher than any other capacitor on the market. It also offers a high energy density - the measure of how much energy it can store.
This could mean an increased mileage range, reduced maintenance, and an enhanced driving feel in EVs.
To develop the capacitor, NPL investigated a range of lead-free materials that could have the desired properties to develop into a high temperature capacitor. They measured current at a range of high temperatures using advanced measurement techniques. The most promising materials were optimised to achieve the desired properties. The resulting capacitor is created from a ceramic, based on doped-BiFeO3 compound.
“The opportunities for electric vehicles are huge, both financially and environmentally, but they are currently being held back by a few technical issues,” said Tatiana Correia, lead scientist on the project. “With this high temperature capacitor we believe we have solved an important one of those issues and will play a vital part in the move towards mass market electric vehicles.”
A recent Frost & Sullivan report shows that capacitors represent a £10 billion global market in the automotive industry alone. This capacitor also has huge potential in other areas of high temperature electronics for other industries, such as pulsed power applications (defibrillators and x-ray generators), energy conversion in photovoltaics and integrated circuits, downhole power electronics in oil and gas industry, which need to work at high temperatures or are subject to overheating.
The project has also allowed NPL to develop a range of new capabilities in metrology to assess energy and power in capacitors across a temperature range, which it will be offering as a new service.
The capacitor was developed as part of the Technology Strategy Board project Advanced Capacitors for Energy Storage (ACES). NPL is interested in hearing from industrial partners interested in licensing the innovation.