| Hydrogen and power-to-X
to the electrolyser stack and ensures the electrolyser is operating at its optimum Faradic efficiency. Overall, IGBT rectifiers can achieve an efficiency of around 98.5% and can reduce the overall power consumption of an electrolyser park by up to 10%, compared to a thyristor rectifier. IGBT rectifiers generally offer a total harmonic distortion (THD) below 5%. This performance satisfies stringent grid compliance requirements without the need for external passive filters and capacitor banks which would be required to achieve this low THD when using a thyristor rectifier.
A limitation of IGBT technology is that it cannot supply the high current density required by advanced alkaline electrolysers. It is therefore better aligned with PEM or traditional alkaline water electrolysers, which operate with a lower current density. The dynamic performance of IGBT rectifiers is excellent. This aligns them with variable and intermittent renewable power supply - situations where PEM electrolysers are often specified.
● Silicon carbide semiconductors Silicon carbide (SiC) is a wide bandgap (WBG) semiconductor material which may challenge silicon IGBTs. It is a relatively new technology with limited commercial availability. Furthermore, it has a higher capex cost than IGBT equipment. SiC semiconductors are around four times the price of silicon semiconductors used in IGBT rectifiers.
When considering the semiconductors in the context of the overall rectifier system, SiC can add several percentage points to the total capital cost. However, the cost of SiC semiconductors is likely to fall as the technology is adopted and production scales. SiC offers faster switching speeds, superior thermal properties, and reduced losses versus IGBT, yielding an efficiency improvement of
Alkaline water electrolysis cell assembly. Photo credit: thyssenkrupp nucera
more than 1% and resulting in a rectification system efficiency of more than 99%. Electricity is an ongoing cost of electrolyser operation. The capital cost is depreciated over the lifetime of operation, generally 20 to 25 years. Investing in a 1% efficiency improvement will cost more on day-1, but over the lifetime of the project the efficiency gain may save many times the additional capital cost due to reduced electricity consumption.
The cost of energy and the cost of finance for capital vary from project to project, so each case must be assessed individually. However, it is likely that there will be increasing demand for the most advanced SiC rectifiers for electrolytic hydrogen projects in the coming decade. The ability for SiC to switch at very high frequency leads to a high power density and a small footprint. This means SiC rectifiers can fit into small containerised
electrolyser systems and will offer advantages for offshore electrolysers exploiting renewable wind power.
Part of the broader trend towards industrial electrification Aluminium smelting, via the Hall-Héroult process, is a major consumer of DC electricity. Large graphite anode electrodes are plunged into the melt. DC electricity flows from these anode electrodes to the cathode electrode, which lines the base of the electrolyser bath. The electron flow reduces the molten cryolite to molten aluminium metal. Thyristor electrolysers are required in this application.
Electrification of many more industrial processes using nuclear, hydro, solar and wind power generation is inevitable. This will support a reduction in greenhouse gas emissions and support climate change mitigation. Electrolytic hydrogen production is an example of this broader trend. Several other electrification transitions will require DC electricity. Electric arc furnaces (EAFs) are increasingly being used for scrap steel processing. Modern EAFs use DC electricity to increase the life of the electrodes and improve the system efficiency. To supply the high currents and voltages for this application, thyristor rectifiers are the best fit technology.
Low current density PEM electrolysis process. Source: sbh4 GmbH
DC EAFs range from 20 to 100MW in size: a similar spectrum of power required by many electrolyser schemes which are currently being deployed. Turquoise hydrogen production can be achieved using DC plasma in which case, it requires rectification of AC to DC electricity. Large DC plasma torches consume more than 10 MW of power, so this will also be an application where schemes will be deployed at a similar scale to hydrogen electrolysis.
www.modernpowersystems.com | January/February 2026 | 33
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45
