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Interview with Marek Kubik, leading expert on energy storage

April 1, 2021

Gabriela Herculano


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Marek Kubik is an energy storage aficionado and a big believer in the power of technology to fundamentally improve our living standards. He is a Doctor in Engineering and was named a 2017 Forbes 30 Under 30 honouree. He was also invited by the United Nations to be an industry contributor to “The group of experts on cleaner electricity systems”, a subsidiary body of the Committee on Sustainable Energy. He is the Market Director and a founding member at Fluence, a joint venture between AES and Siemens. Founded in January 2018, Fluence has already delivered or been awarded over 100 battery storage projects in more than 22 countries, totalling more than 2000 megawatts.

Gabriela: Renewable energy is intermittent in nature. Is utility scale energy storage the solution to this problem? Could you tell us the characteristics of the current systems that Fluence is delivering? Is the current technology shifting the time and location of the power delivery at the level needed? Please tell us about what advanced in battery storage solutions will be needed for the world to be able to evolve into a 90% renewable energy based grid.

Marek: It’s an important part of the solution but it’s a classic ‘it depends’. If the objective is to get to 80% or 90% renewable, that’s different to 100%. Generally, battery-based energy storage which is responsible for almost all new energy storage deployment worldwide is ideally for dealing with the balancing from second to second and keeping the grid stable even when there’s a lot of intermittent generation like wind or solar. It’s also equally well suited to bridging daily imbalances – a 100MW solar farm with a 100MW/400MWh battery attached to it can more or less provide firm power around the clock, even at night. It might be surprising, but we don’t actually need that much duration to deal with daily variability. The longest durations we see being commercially required are 6-8 hours, and batteries have already competitive for that.

On the other hand, weekly or seasonal storage is needed to get the last 10-20% of electricity off reliance on fossil fuels. Whilst wind and solar are somewhat complimentary – it being windier in the winter and sunnier in the summer, we still get periods where both will be limited. There are plenty of technical solutions to this already – thermal storage, hydrogen, compressed or liquid air, pumped hydro; the question isn’t really if we can solve this issue, but rather what the most cost effective solution will be when this starts to become a problem.

Gabriela: I believe you recently told me that Fluence is somewhat agnostic in terms of the type of battery technology you deliver. You will design a solution based on what you see as the best available battery. Lithium-ion seems to be the most prevalent solution today. There are also companies developing kinetic energy solutions (even with “flying bricks”). Could you please tell us more about what type of battery you would expect to be used the most in the next 5 years, for utility scale energy storage? What do you predict will be the most important technological advancements in battery technology in the next 10 years?

Marek: That’s right. Fluence is technology agnostic technology company. Rather than take a vertically integrated approach by making our own batteries and trying to convince customer’s they’re the best fit for everything (which is impossible!) we recommend the right solution depending what a project is set up to do. The type of solution you would recommend for using batteries to regulate frequency only is different to one where you know the batteries are going to load-shift from day to night for example. It also means we can easily pivot to take advantage of any new breakthroughs that emerge in the field.

It may sound a little boring, but unfortunately over the next 5 years or even 10 years there is one very clear winner and that’s lithium ion batteries. The learning rate continues to be very steep and there are positive feedback loops, as demand drives further R&D and spurs on further cost declines. The most interesting technological advancements are likely to be under the umbrella of lithium ion chemistries, but there is fortunately still a lot of nuance here with lots of sub-chemistries, new designs of anodes and cathodes, solid state electrolytes and so on. Each will contribute promising further incremental advancements for safety, longevity, performance or density. Big step changes in any of these are of course much harder to predict!

Gabriela: What about hydrogen as a long-term large-scale energy storage solution to support renewables? Is hydrogen a potential solution? Do you think different types of energy storage have room to co-exist or it will be one versus the other?

Marek: It’s certainly an option – technically it’s feasible, it is just a question of economics, infrastructure and fit. Personally, I believe these three tests aren’t currently favourably met – hydrogen conversion needs to get much more efficient for it to become cheaper; it isn’t readily possible to convert and re-use existing infrastructure e.g. natural gas pipelines to carry hydrogen which means throwing out our current infrastructure and starting with something afresh; and finally it doesn’t really fit the trajectory of decarbonisation which is following an “electrify everything” narrative.

If heat networks and transport became hydrogen based rather than electricity based it’d be a neat solution, but I feel the momentum for electric vehicles is clear.

Having said that, we still have time to deal with the last 20% weekly or seasonal storage problem which batteries can’t solve, so there’s plenty of time for innovation in hydrogen, but the same is true of all the other potential long duration solutions out there.

Gabriela: Wind and solar are blamed for threatening grid stability. What is your view on this? Is that really the case and is battery storage again the solution to this problem?

Marek: It’s at best a bit disingenuous and at worse nonsense. Ironically, the stability issues they cause are predominantly affecting fossil fuel power plants, which, for instance, don’t operate well in low-inertia environmental and are sensitive to tripping. If the grid was completely wind and solar based these stability problems would also go away!

The argument is frequently used that wind and solar require “backup” fossil fuel generation in case the wind dies down or a cloud passes over – again, ironically, this requires turning a blind eve to the fact that fossil fuel power grids have to provide even larger reserves in case a 1 gigawatt power station trips. This usually has a bigger stability impact than wind and solar which are more distributed and therefore reduce the single point of failure impact of a centralised system.

Of course – these arguments unravel even more when you add storage – a recent California Public Utilities Commission study identified that a fixed axis solar farm on its own has a 5% contribution to effective load carrying capability (read this as reliability), but by adding just 4 hours of storage it jumps to 99.8% – so yes, clearly batteries can solve the reliability and grid stability concerns effectively.

Gabriela: We recently interviewed Chris Goodall, the author of the book “The Switch”. He thinks V2G will change everything and make distributed generation prevalent and disrupt the traditional model of utility distribution. Do you share that view? Are batteries – utility scale and EV ones – to dramatically disrupt incumbent players (both energy producers of fossil fuel based large power stations as well as the energy distribution companies) in the next 10 years?

Marek: Not in its entirety. I agree with Chris that distributed generation will disrupt the traditional incumbents (we’re already seeing that), but I don’t think it will come from V2G. My view is that the V2G model rightly picks up on the trend of transport electrification and that there will be mobile batteries on wheels everywhere but misses two other important trends – autonomous driving and the move away from car ownership towards “mobility as a service” and ride hailing.

If you have a fleet of autonomous, driverless Ubers rolling around the amount of time that cars would spend plugged in drops way down (to maximise their return on investment), which significantly reduces the V2G opportunity. I think it’s far more likely that stationary batteries at EV charging points will act as “buffers” for fast chargers and other infrastructure so that we can more easily manage two way power flows on the network and deal with sudden power spikes.

All in all, EVs therefore likely create a growing need for even more stationary energy storage to manage spatial issues and local network constraints and act like virtual transmission lines, as well as the temporal issues we more commonly think about of moving renewable energy from the time when it’s generated to the time when we need it.

Gabriela: We really appreciate that you are making the time to talk to us and explain battery storage and your views on how this solution will evolve in the future. We look forward to following you and reading your future articles. Thank you!

If you would like to read Marek’s views on energy storage, you can follow him on LinkedIn at

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