Sufficiency or Efficiency – The Answer Lies In Between

An interview with Professor Dr.-Ing. Stefan Tenbohlen, Steinbeis Entrepreneur at the Steinbeis Transfer Center for High-Voltage Technology and Energy Transmission

Energy is an essential part of modern life. Having worked in the field of power and energy supply for nearly three decades, Professor Dr.-Ing. Stefan Tenbohlen, Steinbeis Entrepreneur at the Steinbeis Transfer Center for High-Voltage Technology and Energy Transmission and head of the institute of the same name at the University of Stuttgart, is very familiar with this fact. Among other activities, Tenbohlen also helps grid operators offer reliable energy supplies. TRANSFER magazine spoke with Tenbohlen about some of the projects he has worked on and the future of the energy sector.

This slideshow requires JavaScript.


Hello Professor Tenbohlen. It’s a highly topical area at the moment, but you’ve been working in energy for almost 30 years now. When it comes to trends and developments, what for you have been the most important milestones in the energy sector during this time?

In the early years, deregulation and unbundling were high on the list of priorities. Policymakers at the time were striving to change the monopolistic structures of energy supply and move to a free market. Companies should no longer be responsible for everything, from generation to transmission, distribution, and selling electricity; customers should be able to choose electricity providers themselves. It was about deregulating the energy market by dividing up large companies into a number of smaller ones. That was the first step and an important one. Then came expansion into renewables, which was triggered by corresponding technology developments in the early 2000s. By 2009, annual capacity increase of around ten gigawatts was in place.

In more recent years, there’s been a phase when things were a bit quieter, with five or six gigawatts per year. Of course, it’s good to hear that the policymakers now aim to put up to 30 gigawatts in place per year from 2025. That would be three times what we had at the peak time, and five times what we’re installing right now. So it’ll be interesting to see if that really does happen.

The services provided by your Steinbeis Enterprise include fault  investigation and the analysis of outages in the electricity grid. What does that involve for you?

Before a customer inquiry comes in, the experts at the affected companies will have already conducted an analysis of the problem. So by the time they approach me, the problem’s usually gotten more serious and complicated. The first thing I do is read into the background, because various measurements have already been made and some things have been investigated. Then I have to work out if everything stacks up. Do the readings and results fit together? It’s not uncommon for me to have to start by redoing the math.

For example, if an insulation system fails, which is often the main problem with high-voltage engineering, you have to calculate the electrical field to determine the stress. Then I check if they’ve used the right insulation criteria. But there are also cases when the problem is so severe that I have to bring in help. I can give you a recent example of that. I’m working on a project at the moment involving wind turbines; the transformers keep failing. They’re filled with a special oil and they’re subject to specific operational limitations. There aren’t many experts in the world who can say exactly what’s going wrong. But I’ve been working in this field for a long time, so I have lots of contacts who can provide help.

In what way do the insights you gain help manage or even minimize risks to energy supplies?

When you look at the individual circumstances of a fault, you learn how to adapt designs or operations – that’s the bottom-up approach. So it’s important to collect outage data and analyze everything, from start to finish. I’m the chairman of an international working group that investigates faults affecting power transformers worldwide. We collect information from everywhere, from Australia to China, India, South Africa, Europe, and South America, to see what the reasons are for transformer failures. To analyze faults, we take a top-down approach and come to conclusions regarding individual problems based on experience with the entire universe of data, and then we suggest corresponding measures to make improvements. The same working group also writes a report outlining how to make such components more reliable. The aim is to avoid future outages.

But new operational requirements have also become more important. This is a particularly significant aspect right now given energy shortages, or rather local bottlenecks in the grid, because operational resources can also get overloaded. So for example we’re developing algorithms to determine the degree to which a transformer can be overloaded depending on ambient conditions. For instance, a power plant fails in the south and that means more power has to be transferred from the north. This helps grid operators make supplies more reliable.

Lots of stakeholders come into play – grid operators, policymakers, science. There are corresponding research programs in place to develop such solutions, but then those also have to be put into practice. This is a sector of industry that thinks in the long term rather than focusing on the short term, so you also have to convince people to use these kinds of tools in day-to-day operations.

We’re currently in the middle of an energy crisis, so it’s all the more important to think about the future. What factors do you think will determine the future of our energy? What new risks do we face? And how can we deal with those risks effectively?

That’s not a technical question; it’s almost a philosophical one. I sometimes use a comparison, which sounds a bit melodramatic but I don’t find it entirely out of place: Take a petri dish with bacteria starting to grow in it. If you give those bacteria some nutrients to feed on, they’ll grow – exponentially. The moment you remove the nutrients, they disintegrate. Ultimately, it’s no different with us humans: The petri dish is the earth and the nutrients that fuel our development used to be, or still are, fossil fuels. As long as those are part of the picture, the exponential curve of our development gets steeper and steeper.

Keep hold of that picture, and then you have to ask yourself what would happen if those nutrients, in the form of fossil fuels, were no longer there? On the one hand because they’ve been used up, or on the other hand because using them triggers other developments, such as climate change, which calls into question the continuing existence of life on earth. Efficiency measures are certainly potential ways out of this, or making more use of renewables. But on the other hand, everyone has to make their own mind up: Do I really have to do all the things I do right now? Must I consume all those things, just because I can? Do I really need to fly on vacation three times a year, or maybe I should save resources, too?

In other words, sufficiency instead of efficiency, although the answer certainly lies somewhere in between the two. But I believe that for this to work, it’s not just about individuals taking responsibility. Also, no matter how unpopular this area may be for politicians, legislation has to follow suit.


Prof. Dr.-Ing. Stefan Tenbohlen (interviewee)
Steinbeis Entrepreneur
Steinbeis Transfer Center High-Voltage Technology and Energy Transmission (Ostfildern)