DC OR NOT DC, THAT IS THE QUESTION

The number one issue being discussed around the world in terms of electrification is ‘how are we going to generate enough electricity to meet the ever-growing demand?’

Of course, microgrids and renewables figure highly in these discussions, but the stark reality is that the world has really only got two options to consider, with either of them representing a challenge of frightening proportions.

Our existing AC-based infrastructure of electrification is technology that was essentially developed well over 50 years ago. Even in the fast-moving 21st century, the world is still working with mechanical switches that are enhanced by electronics. There are transformers, power lines and safety circuits, but the bottom line is that hardly anything in the infrastructure has changed for a considerable amount of time. This is simply unsustainable moving forward.

If we stick with using existing technology, one option that would enable the world to generate and distribute more electricity would be to put more and thicker cables into the ground and add more transformers to the landscape. However, that’s going to be a huge challenge in our current system because the world simply does not have sufficient amounts of cabling, it doesn’t have the manpower and it doesn’t have the space. At the same time, the efficiency of doing this would not be particularly high.

The second option is to step back from AC and use DC directly throughout factories and in domestic environments, which presents an equally staggering proposition – in other words, DC grids (especially small-scale or sub-distribution) will become more common in the future. AC will never fully disappear because there will always be scenarios where it is required, but experts are already gathering in committees to discuss what previously might have been considered unthinkable. As an example, the Current/OS Foundation is dedicating itself to developing an open standard system for DC distribution that will improve resilience, sustainability and safety.

It is an undeniable fact that the concept of switching most of the world’s consumed electricity to DC is gathering pace rapidly, even though the costs and logistics involved are literally unfathomable. On the plus side, there will no longer be any need to convert from DC to AC and back again, a process which always results in a considerable loss of power while delivering far from optimal efficiency.

One of the biggest issues that the electrical sector will have to face in any switch to DC is safety – what kind of safety measures would be needed and what kind of switch gear and power electronics would be required around that?

Essentially, all switch gear would have to change to realise a mainly DC-powered world. Indeed, virtually everything in the existing installed base would have to change – except for the cables, which could stay, as long as the right choices on DC voltage levels are made.

The positive outlook is that most household electrical appliances have power supplies built in which rectify the AC and create DC. This means that if the electricity coming in was already DC, the front end of all those power supplies would no longer be required, leading to a more efficient power supply with less disturbance.

From a technical point of view, DC is certainly a sensible idea, even if the impact of making the change would be huge. The infrastructure is simply currently not there and installers don’t have the knowledge or experience required in setting up a DC circuit. Indeed, the people that the world would need to make this change happen don’t exist yet. That’s why making the switch could take up to 20 years, giving schools, colleges and further education institutions notice that they need to be looking now at how to help people manage the skills and transfer knowledge that will be required in a DC-dominated world.

From an electrification standpoint, the switch is certainly going to happen because the benefits are undeniable – a DC-based infrastructure will deliver fewer disturbances, lower losses and result in greater efficiency in the distribution of electrical power.

While change will inevitably have to come, AC/DC systems will co-exist way past our children’s lifetime, because they both have a reason to be. For the first five or 10 years, most changes will take place on a small scale, such as on an industrial compound or even small domestic communities sharing renewable (e.g. photovoltaic) power. Stepping away from AC is only likely to happen on a large scale in 20 to 30 years’ time when the market fully matures and becomes viable. By then, all test and measurement equipment from companies, such as Fluke, will need to have changed dramatically as well, and the electrified future will require a dynamic response from all the links in the supply chain.