Self-sufficiency in energy supply

Electrical energy is one of the most important resources for industry. Electric motors account for around 70 percent of electricity consumption. Every reduction in the power consumption of these drives through efficiency improvements also means a corresponding reduction in CO2 emissions. Since 2021, all three-phase motors sold in the EU with an output of 0.75 to 375 kW must therefore meet the requirements of energy efficiency class IE3.
 

Reducing losses with gallium nitride and silicon carbide

The use of variable-speed drives is a proven approach to achieving high energy efficiency. This is because the motor only consumes the power that the respective application actually requires. But energy efficiency can also be increased in the inverters themselves – for example, by increasing the efficiency of the power electronics with new WBG semiconductor materials (WBG: wide bandgap). Gallium nitride (GaN) and silicon carbide (SiC) offer higher efficiency compared to the semiconductor technologies that are still predominant today, such as silicon MOSFETs and IGBTs: losses are lower, switching frequencies are higher, higher operating temperatures are possible, robustness in harsh environments is also better and breakdown voltages are higher. Thus, a drive solution with SiC MOSFETs can reduce losses by up to 50 percent.
 

On the way to the direct current microgrid

Losses in drive systems can be reduced even further by reducing the conversion points from alternating current (AC) to direct current (DC) and back. The solution: instead of supplying the electrical systems via an AC network, as is common today, a DC network is established in the factory. This would allow, among other things, the DC intermediate circuits of the frequency converters to be interconnected – making many AC/DC conversions superfluous. In addition, the braking energy of drives could be fed back directly via a DC grid, so that it no longer has to be wasted in braking resistors. Overall, a DC grid can save up to 20 percent energy compared to AC, depending on the application. This was demonstrated by the DC-INDUSTRIE and DC-INDUSTRIE2 projects, in which more than 40 companies and research institutions have participated since 2016.

Advantages of a DC grid in industrial production (Source: DC-INDUSTRIE research project)

Integrating renewable energies

An important contribution to ensuring a stable and secure energy supply is made by integrating the company's own renewable energy sources and battery storage systems into the factory's microgrid. Here, too, a direct current grid offers great advantages: Since systems for solar energy generation supply direct current, all that is needed is a DC converter instead of the much more costly inverter. This not only saves costs, the dynamics and efficiency are also higher. The easily connectable storage units also provide enough energy to limit the loss of production in the event of a utility grid failure.
 

Smart devices monitor energy consumption

In the DC grid, active energy management is an elementary component: it optimises the energy flows between the DC sectors and enables, for example, the marketing of storage energy to support the supply grid. However, energy management requires monitoring of the voltage as well as other measured values at the connected consumers. Until now, this required various components such as measuring and protective devices. These functions are already available in modern electronic switchgear.

Complete self-sufficiency in terms of energy will not be achievable in most factories in the future either. But with high energy efficiency and the introduction of a DC microgrid that directly connects loads, sources (e.g. solar cells) and storage devices, companies can at least become a little less dependent on the external provision of energy.

DC grid in industry with connection of renewable energies and energy storage systems (Source: ZVEI)