Tallinn University of Technology

Andrii Chub is a power electronics scientist. He is a joyful man. He is from Ukraine. Chub works for the future: he is developing future converters for future houses, finding better ways for electric energy conversion.

Andrii Chub laboris

Mari Öö Sarv, translation by Kitty Mamers | Photos: Karl-Kristjan Nigesen

We met for this interview on the 39th day of Russian war against his homeland. His home town Chernihiv had just been liberated by Ukrainian forces and he could communicate with his family again. 

Chub works as a senior researcher in the power electronics group which is a founding member of “Centre of Excellence for zero energy and resource efficient smart buildings and districts”. It is one of the biggest groups here in TalTech. He says he is the funny guy in his group, and that shows when we walk around his lab and he talks to his colleagues.

Let’s start with the hard part. You are from Ukraine. How are you doing?

Overall it has been really stressful, to say the least. It’s not easy to concentrate. This month there was also a submission of a big project proposal, so this was double stress. I submitted a five year project application with collaboration from Brazil, Chile, Netherlands. I wish it had been better refined, but I did my best considering the situation.

The hardest part is to stop reading the news. My family is in Chernihiv - my parents, my brother, my cousin, her whole family, my aunt, a lot of friends… All of my family is alive but they had no heating, no electricity, no water, no anything for weeks. Right now our army is clearing out the region. Russians used special radio-electronic warfare to minimize the connection and only one out of three SMS-s arrived. It was really stressful and hard. Now it’s much better, they finally have some internet. They still don’t have electricity and they go to special places to charge their phones. 

How’s your alma mater now?

My university in Chernihiv was partially bombed, so the buildings are there but the windows, doors and many things inside were destroyed. People are trying to do their best to teach online. 

You have been in TalTech since 2013. How did you get here?

Connections. There was a big conference, run by Kharkiv Polytehcnic Institute. They did the best Russian-speaking conferences in my field there in a resort base in Crimea. Professor Dmitri Vinnikov had good connections in Ukraine and Russia at that time and one of my colleagues from Chernihiv was already working here: Oleksandr Husev who got the best young researcher title this year in Taltech. 

I came here three years after my Master’s degree. I had been working in the industry for three years and it had become a bit boring. First years are really enriching for a young engineer in industry, you learn real things, but then it starts to be more and more routine.

It’s the first time I hear that engineering work can be boring or routine.

At the beginning you’re “how to do this?” and “how to do that?” because after university you don’t have the experience. But after that, things are starting to be more routine. There’s still some level of innovation, but mostly you just do what you have to do and you already know how to do it. 

As a scientist, what motivates you?

I’ve always liked learning things, and in science you can not only learn, but also do new things. I want to make something tangible. We are in an applied field, so we are doing things that people can eventually use, or at least based on this something can be built further to be used by people.

In the energy crisis we think more and more about things like autonomous houses, autonomous heating, energy supply security in homes. Big part of our research is how to build future houses with a new type of energy systems inside. 

Tell me about your work. I know you invented a converter that adds an important piece to a picture where the whole city is solar power plant.

Andrii Chub

We are used to typical energy systems with alternating current, but we are looking into a house that will work on a direct current. Direct means that it holds a certain value, just like a battery of 1.5 Volt, just much higher.

Imagine you have a solar panel on your roof, it is direct current, and you have a battery to store solar energy. We invert the direct current into alternating and from alternating - back to direct. There is no reason to go through alternating current, you can go from direct to direct, using our new technology. Such houses are expected to be up to 20% more efficient. 

Moreover, I’m trying to create new power electronics that will be more universal. The idea was to make a converter that could work with any type of photovoltaic modules that can be used in buildings. You can have a solar roof, solar facade, even a solar road - the pavement is being worked on in our university by the colleagues from the Department of Material and Environmental Technology - and have one converter that fits them all. There were articles about this in Novaator and “Research in Estonia”

So, this new converter works with different voltages?

Yes. It’s important because there are a lot of different technologies on the market. The most known is based on silicon, it’s rigid and mature, that’s why the industry likes it. But imagine you need more flexibility or better performance in shady conditions. In this case, other technologies, like thin-film could be used. Those technologies are actively developing and expected to be much cheaper than silicon in the future when we ramp up the production scale. 

Also it is flexible which means there could be a lot of different shapes and forms and you can cover different surfaces with it. There are also solar facades in a lot of colours. It brings a difference in aesthetic or architectural design, also in retrofitting heritage buildings. 

You work in the future. We cover future houses with solar panels and your inverter makes the solar energy usable for future devices...

Yes. Basic idea is that you have certain direct current voltage in your house that feeds more powerful loads, and for smaller loads like TV you can use USB-C wall connections. We are following practice that is already happening in Netherlands. Netherlands is the most advanced country in that field and the only country that actually has regulations on how to build direct current networks inside houses - how to put wires, what voltages should be, what kind of protection should be. In our developments we are trying to target their regulations because this is the only example we have for now. 

These days the European authority on standardization IEC is working on new standards of low-voltage direct current grids for residential houses, there should be a new European standard by 2025. We also try to be in touch with people developing these standards.

What are the next challenges to bring your super-fitting converter to the market?

Currently the biggest challenge is the same in the whole electronics industry: shortage of components. In power electronics we use a lot of chips and transistors, and there are delivery times in June 2023. In our research it’s a problem because I constantly need to redesign and build a new prototype. We used to have an industrial partner for that, but now they have the same problems. But this is temporary. 

If we imagine that we have enough chips, two biggest challenges will be to convince people with the price and that this is safe and reliable. 

Direct current systems in houses is a new thing, although the world is full of direct current systems. For example, telecommunication. All new warships are full of power electronics. Boeing 787 Dreamliner, the first “more electric aircraft”, has a DC grid on board with the peak power one megawatt, maybe like TalTech NRG building! Electric car is basically a moving DC microgrid. Direct current is a trend. 

By “convincing people”, do you mean politicians or customers?

Also installers. What is always problematic: industry is not sure. Good examples are electric grids. Nowadays they can have more power electronics inside but people are not confident with it. Electric power grids have used transformers: it has worked perfectly for 100 years and has a lifespan up to 50 years. Power electronics may not do this, but it’s something that can bring a lot of flexibility and control in your environments. Power electronics have made a big leap of development in the last 20 years. 

To convince people, of course you have to have a nice cost as well. That’s one of the reasons we try to make converters smaller and increase frequency. Minimizing the cost is not always easy in the university environment – some technologies are justnot available. But we can develop ideas to technology readiness level 5 or 6. Above that you need industry to be involved because this is the point you need to play with bigger money and have access to certain technologies. 

Typically the first step in cooperation with a company would be some kind of project to bring the technology to higher level. A good example in Estonia is Nutikas program. Everything is about technology readiness levels. The company engineers have more knowledge about how to build a converter or a board to make it easier to certify. This is something I may not be thinking about when I build. But in university we cannot do industrialisation, we cannot do mass production. We can only help companies to bring things to life.

Andrii Chub

You mentioned the 50 years lifespan of transformers. How about your converter’s reliability?

My research lately has been concentrating a lot on reliability and fault tolerance of power electronic systems. For some systems the expectation is that the converter should run reliably for 20 years. This requires a lot of research in reliability at component level and at system level - how long can this survive, how long that, and how do they survive together? How many years, in which conditions? I am one of the people dealing with this. 

We are developing new methods of prediction of the lifetime of a converter, based on their mission profile. There is a system recording data on our roof: Sun intensity, solar irradiance, temperature. It’s easy to find information about Sun energy production with 15 minutes step for almost every country, but when you work with power electronics, you need one second step at most.


For example, with a 50 Hz grid we have 50 times per second temperature fluctuations, also the Sun intensity could change fast. Basic problem is mechanical strain because of heat pulsing in converter components. The converter heats up, cools down, heats up, cools down - eventually something will happen, something will break or crack and disconnect from the board.

When a component operates for years, it accumulates certain damage until it breaks. We need to take into account all the smallest fluctuations to really calculate the damage. And to really predict this damage finally, we need this kind of dataset.

In one research line I’m working on fault tolerant converters - if one transistor breaks, disconnects or burns, it doesn’t break the system. Of course there are limits, you cannot load your converter as much, but you can continue operation after some of such failures. 

We need to make the converter reconfigure itself. It’s a little like a self aware control system: it tracks conditions and if it sees something is wrong, it starts to identify what is wrong, isolates the fault and continues working without it. 

How about patents and intellectual ownership when we talk about industrialisation of your inventions?

Some of them are patented, some of them are not. Power electronic converter is a complicated circuit and if you change it a little bit, you need another patent. It could be very costly. So sometimes you just keep know-how inside - how to really build certain components. As a university we must publish, but we are not necessarily uncovering all the secrets. 

Have you thought about making your own company to bring your systems to life yourself?

This is an interesting question. To be honest, and I have seen this with different people - it’s not easy to be in both places, university and business. At some point, if you want to do things seriously, you will have to choose. Right now I don’t want to fully switch to the commercial part, I still see a lot of things for myself to do in university. I defended my PhD just in 2016, I think I still have some juice in me going regarding the research.

In the beginning of the interview you told about routine days in the company. That feeling hasn’t visited you here?

Andrii Chub

Here it’s much better, definitely. I have more different tasks, more variety of things and also the tasks are not standard. In Estonia you have a lot of startups and startups like new things. But big industry doesn’t like new things, they like robust, known, something that is shown in the field for 10 or 20 years. 

But your work in these labs still meets real life, right?

It does, yes. My work allows me to keep updated about the latest industrial developments. Just recently, our group has entered into an agreement with the TOP1 company in the market of power electronic components - Infineon, their Austrian branch. We will hire two doctoral students who will be jointly supervised by our university and industrial R&D department, developing top-notch industry-oriented technologies.

In the beginning of 2000s this department was involved in renovation of trams. If you remember, trams in Tallinn got new automation systems and new automatic stop announcements. Actually for a while it was running with the voice of one of my colleagues before they hired a professional. 

This group also developed certain converters for company Estel here in Tallinn that collaborated with Russian railway systems for many years. 

Currently our developments target nearly zero energy buildings, cleantech industry, and transport electrification. We also participate in European projects which are not as scientific as people expect but more practical. 

How difficult would it be to create a converter for the Russians that you can switch off all at the same time on the Russian railway?

I don’t know (laughing). But you’ve got a good point here because in power electronics, cybersecurity is a new field of research and a big field of awareness. Power electronics is starting to be more and more connected. The question is what to do about this because when you have a device that can feed something with electricity in your home, it is connected to the Internet. There are a number of examples when people have been breaking in solar inverters because those are running on standardized operating systems. 

In case of our converters, they are not connected. This is one of the things we try to do - converters should be autonomous, first of all to avoid extra wires and also to ensure more safety inside your house. You definitely don’t want somebody digging into your converters. Everything is possible if you are on the grid. That’s why no atomic station is ever connected online, they are totally autonomous systems typically, or at least there are layers of isolation. 

By the way, solar energy is basically wireless nuclear fusion energy, if you think about it: it is nuclear fusion and it comes to us wireless. This is the idea from my friend professor Samir Kouro, he is very famous in Chile and the world. 

Coming back to solar energy: there’s still storage issue…

Our group also works on this. Not me personally but I was involved. But as of now, Australia is the first country where batteries are actually profitable in some regions because of high cost of energy and zero cost when you give your energy to the grid, so you can really pay back your batteries. 

What’s the next big problem you want to solve as a researcher?

Just a few days ago I submitted a big project application, this is a Personal Research Team Grant supported by several companies. It’s an idea of a new type of converter, a so-called partial power converter. 

What does it mean? 

Imagine a converter with a volume of one liter, that can process 1000 W of power. Using the new technology I am proposing, a converter of a similar size can proces 3-5 times more power. This is possible since the new technology processes only part of the power needed for regulating voltage and current in the system. Typically, power converters process all power and thus lose more power than the new converters proposed in my project. They can achieve lower cost, better efficiency and less material use when compared to the existing technology.

I’m talking first of all about cost: how many cents you pay per watt. With traditional power converter you pay between 10 and 30 cents per watt, i.e., between 100 and 300 euro for 1 kilowatt converter. The partial power converters feature up to 50% lower cost. On the other hand, the new type of converters cannot be used in all applications. Nevertheless, they suit for needs of modern applications, like solar photovoltaic energy or hydrogen fuel cells.

The converters I aim to develop could be very useful in energy storage system with ultracapacitors. Therefore, Estonian company Skeleton has supported this project. Ultracapacitors can supply very high power pulses, which makes it complicated and costly to develop power electronic converter for them. The technology proposed by me allows for improved efficiency and lower cost of energy storage systems using ultracapacitors. They can provide a big performance improvement - in speed of control, in cost, in technical and economical aspects.

I also have support from Powerup, a local company developing fuel cells. This technology I’m proposing could be used for integrating hydrogen fuel cells into the DC microgrid of houses. For example if every energy disappears, this could be like an energy buffer. 

Estonia is actually very good in fuel cells, not many people know that. We have two companies in Estonia: Elcogen, a big company doing fuel cells techs, and as far as I know, most of them are sold to Japan. And another one, a smaller company called Power Up. They entered the business from yachts. In many environmentally protected harbours you cannot use diesel generators, but you need to maneuver for parking. Therefore maneuvering is done on electrical motors. Fuel cells are an excellent solution there. There is always a niche for every technology. 

Now I have to ask the million dollar question: what is a good energy solution for Europe, considering the current political situation and everything?

I think the question is not “Russian or not Russian”. It’s “fossil or not fossil”. Of course we cannot switch to green energy immediately. Probably Europe will need to start burning coal for some time, if we want to switch from Russian gas for political reasons, until we can replace coal with something better. Cost of electricity from coal is higher than electricity from solar panels right now, and this trend will be stronger in the future. This makes transition to green energy sources also a profitable move.

Did you know that 5 years ago, Estonia had one of the dirtiest economies? We were the second worst in EU because of oil shale we used. But we’ve made a super jump and we are fourth now.

Estonia has reduced its CO2 pollution in the last several years by over 30%. In Estonia people underestimate how much the government is doing. It’s been mostly wind energy, but Estonia is switching to cleaner sources in general.* 

But for Estonia, oil shale is also a security. There is always a chance to go back to oil shale if something happens. In general, energy supply security is the most important topic. And when the economy grows, and we hope for the economy to grow, it takes more energy. 


Andrii Chub