**Preface to "Energy Efficiency in Electric Motors, Drives, Power Converters and Related Systems"**

The promise of sustainable growth through the use of renewable energy has been attracting increased attention around the world. With the same goal of sustainable growth in mind, the potential for obtaining transformative results (that have an immediate, short-term impact) through increasing energy efficiency should not be ignored. As an example, the European Union has set itself a 20% energy savings target by 2020, which is roughly equivalent to turning off a few hundred power stations. Today, 20% of all final energy consumption in the EU is electrical energy, but this is predicted to grow significantly over the next few decades. Within this scenario, power electronics is a key enabling technology that allows not only the efficient generation, use and distribution of electrical energy, but also the implementation of energy saving applications at reasonable costs. The widespread diffusion of electric motor drives has also been enabled by power electronics.

Power electronics is a transversal technology, which covers a very high power range, from the order of mW required for mobile phone operation to the order of GW for applications in the field of energy transmission. Advanced power electronics can achieve very substantial energy savings. There are many market segments that can potentially benefit from the use of this technology: home and office applications; heating, ventilation and air conditioning; consumer digital products; communications; factory automation and electric drives; electric traction; the automotive industry; and renewable energies.

Power electronics is the key technology that allows the flow of electricity from the source to the load to be controlled with extreme precision, satisfying the load specifications. It is responsible for the reliability and stability of the whole electrical grid, including sources; transmission; and distribution of energy to a very wide variety of applications in industry, transport systems and almost infinite domestic and office applications. As a technology that allows for the efficient use, distribution and generation of electricity, it enables significant energy savings. There are many fields of application worth mentioning.

The connection of renewable energy sources to the electricity grid would not be possible without power electronics: power electronic converters optimize the efficiency of photovoltaic panels and allow making the best use of the energy produced by wind turbines.

Electric motor drives use 50%–60% of all electricity consumed in industry. By using power electronics, it is possible to achieve a reduction in energy consumption of about 20%–30%.

In domestic applications, electronic thermostats for refrigerators and freezers can lead to savings of around 20%, while another 20% can be saved by using power electronics to control the compressor motor. Further energy can be saved if the motor is built with permanent magnets.

Advanced power electronics can, for example, achieve savings of more than 50% of energy losses in the conversion of mains or battery voltage to that used in electronic equipment.

New technologies in power supplies can increase efficiency by around 2%–4%, reducing absorption in conditions of low power requirement or standby, reducing losses from 14% to 30%. Digital control can further reduce energy consumption.

In automotive applications, electric or hybrid drives are only possible using intelligent power electronics. The concept of a "drive by wire" fully electric vehicle can allow savings of more than 20% thanks to power electronics.

Despite the strategic importance of power electronics, there is a lack of awareness of its role in

modern industrial society, even among the generally well-informed public. The impact of power electronic technology, capable of providing reliable and precisely controlled electric power sources in all areas of human life, is not known at the public level. Energy savings, which would be achievable in the short term using the electronic power technologies already available today, are not implemented in many fields of application. The enormous energy saving potential available through the development of new technologies that affect the entire supply chain, including consumer equipment, remains to be understood and implemented. Furthermore, from both public and political points of view, it is clear that power electronics does not have the same appeal compared to, for example, microelectronics or nanotechnology, with a negative impact on the attractiveness for students and on the destination of research funds.

The publication of this collection of scientific articles, dedicated to the topic of energy efficiency using power electronics and electrical drives, is our contribution to better disseminate this information to people.

> **Mario Marchesoni** *Special Issue Editor*
