A new European champion for fusion: Proxima spins out from Max Planck

I’m very excited to announce that Plural and UVC Partners are going to be co-leading a €7m seed round for Proxima Fusion, the first ever spin out from the Max Planck Institute of Plasma Physics, creators of the world’s most advanced stellarator. Given the excitement that is building around fusion, I thought it would be interesting to lay out why we are committing to Proxima.

1. Why fusion?

Clean, reliable, safe, cheap, zero carbon, baseload energy generation is increasingly critical as Europe navigates both the climate crisis and works towards true energy security - fusion has the potential to satisfy every single one of these requirements. At Plural we are big believers in wind and solar and are lead investors in Field Energy, a developer of grid-scale battery storage (needed to help manage the volatility of renewables). However renewables are still limited in their ability to provide baseload power to the grid, and require significant land resources. Nuclear fission is an amazing and proven technology but challenges around disposing of nuclear waste, and the risks of catastrophic meltdowns drive both political resistance and increased cost. Fusion has the potential to take advantage of the energy density of nuclear energy but without these constraints.

Beyond the climate crisis and energy security it is important to remember that fusion is the energy source that powers the universe. Harnessing it directly on Earth would be a foundational technology for humanity and one that could take us to a world of true energy abundance. So much human progress has been unlocked by cheaper energy and fusion could take us into a fundamentally new era. Like today’s most advanced submarines, the spacecraft of the future will likely be powered by nuclear reactors. I first fell in love with the vision of fusion playing Sim City as a child - as a game it beautifully captured the path towards more and more ideal sources of energy and by the end of a game my city would always be powered by fusion!

2. Why now?

The old joke about fusion is “it’s 30 years away…and it always will be”. This is not true anymore due to spectacular progress in the field over the past decades - I believe it is now likely we will see the first fusion power plants connected to the grid in the 2030s. This graph shows the progress towards the conditions required for a fusion power plant over time:

Source: [1]

Progress in magnetic confinement (a kind of fusion reactor that uses powerful magnets to confine plasma) has been advancing faster than Moore’s law and we must now have some confidence in extrapolating what might be possible from here and not falling back on tired cliches. Fusion reactors on Earth now routinely reach temperatures above 100 million degrees: we are getting close!

A major enabling technology for magnetic confinement fusion has been incredible improvements in superconducting materials. You can think of the relationship between superconductors and fusion as similar to how progress in semiconductors has underpinned progress in computing.

Over the past decades we now have new superconducting materials that can be made into tape, that superconduct at higher temperatures and produce much higher magnetic fields. This is transformational for magnetic confinement fusion because many properties dramatically improve as you increase the magnetic field. In the case of stellarators, doubling the magnetic field can increase the power output of the machine by as much as 16x (power output scales to the fourth power of the magnetic field). This allows us for example to design much smaller fusion reactors that can achieve similar performance. 

I believe that in the coming decades we will continue to see breakthroughs in higher field superconductors and if this happens, it will be utterly transformational for fusion. However this is all upside - just with the superconducting materials of today we should be capable of putting fusion on the grid.

3. Why stellarators?

Stellarators are maybe the best kept secret in fusion. The stellarator was the original design for a fusion device, created by Lyman Spitzer at Princeton in 1951. It is a fundamentally beautiful design that uses a series of external magnetic coils to entirely confine a plasma across 3 dimensions. If you were trying to come up with the simplest and most elegant way to make magnetic confinement fusion happen you would probably arrive at the stellarator.

The big challenge with stellarators is that in the 1950s we did not yet have the computing resources to fully optimise the design of these complex coils and in 1958 a new kind of fusion device was proposed, the tokamak. This radically simplified things by only confining the plasma on two dimensions using external magnets. The final dimensionality reduction of confinement was achieved by inducing a current in the plasma. As you can see this yields a dramatically simpler machine:

If stellarators are a pretzel, tokamaks are a donut.

This simplification in design complexity led to tokamaks racing ahead of stellarators and absorbing the vast majority of funding for magnetic confinement fusion over the following 50 years.

However there is a serious challenge with tokamaks - what is simpler to design is not simpler to operate. Although the initial design is easier, inducing a current in the plasma can cause what are known as disruptions. Disruptions are almost like a lightning strike inside the tokamak and they can be extremely violent. When I recently toured JET, one of the most advanced tokamaks in the world, it was amazing to see the vast metal frame that is needed to hold the 2800 tonne reactor down in the event of a disruption. Unbelievably a machine the size of 14 blue whales can literally lift off the ground under the explosive force of a disruption! Disruptions remain a major unsolved challenge for tokamaks.

However some true believers continued to keep the dream of stellarators alive. Progress in computing allowed for more complex magnetic fields to be designed. New manufacturing techniques and superconducting technologies allowed for new possibilities. The most remarkable stellarator effort has been led by the Max Planck Institute for Plasma Physics in Germany. The team there continued to build larger and more powerful stellarators, starting in 1988 with the Wendelstein 7-AS which established remarkable new records for stellarators and was then succeeded by the Wendelstein 7-X which took stellarators into a totally different performance regime. As part of making the decision to commit to Proxima Fusion I visited this incredible device and it is one of the most impressive things I’ve ever seen in my life - a masterpiece of physics and engineering. 

Stellarators, whilst harder to design, are radically easier to operate. They do not suffer from disruptions and can be run for much longer than tokamaks allowing them to achieve remarkable new performance records. This graph shows two key attributes of magnetic confinement fusion, the triple product (a good measure of how close a fusion reactor is to net power output) and the maximum confinement time achieved at this triple product (longer confinement is both a desirable engineering achievement and allows for higher output from a power plant):

Figure: triple product of ion density, ion temperature and energy confinement time as a function of the time the triple product was sustained. Adapted from Refs. [2] and [3].

The ideal is to be in the top right hand corner of this graph, and stellarators are taking us closer by the year.

Stellarators and specifically the Wendelstein 7-X are now achieving breakthrough results compared to the field of tokamaks. This is an even more remarkable achievement when you consider that the total funding for stellarators has been tiny compared to funding for tokamaks over the past 50 years. The German approach to nuclear energy has recently come under fire as it has closed down its remaining 3 nuclear fission power plants whilst continuing to keep coal powered power plants in operation. This tweet alone had over 25m views showing that in the face of climate change and Putin’s invasion of Ukraine, European energy policy is a major public issue. The German government who has provided the funding for the Wendelstein series of stellarators deserves enormous credit as does the exceptional team of engineers and scientists who achieved these breakthroughs. I am a visiting professor at Mariana Mazzucato’s institute at UCL. Mariana coined the idea of an Entrepreneurial State - one that has vision to pick critical missions and underwrite the development of breakthrough technology. The German government’s leadership in stellarators is a perfect example of that. Thanks to their incredible leadership and billion plus Euro investment over the last 30 years stellarators have re-emerged as a leading fusion design and we are now much closer to putting fusion on the grid.

4. Why Proxima?

The world’s most advanced stellarator is in Germany and fusion is moving within reach. It is now time to spin up a start-up to take the advances in the field and put fusion on the grid by developing a first of its kind powerplant. This is Proxima Fusion. Founded by an incredible team of engineers and scientists with backgrounds spanning Max Planck, MIT, McLaren and Google they are a remarkable group of high energy founders with deep support from the Max Planck Institute of Plasma Physics. The founding team includes world experts in stellarator optimisation and I’m thrilled to see a true intergenerational effort where Dr. Lutz Wegener and Dr. Felix Schauer who recently retired after leading the development of the Wendelstein 7-X are joining as engineering advisors and Prof. Per Helander and Prof. Elisabeth Wolfrum key leaders at IPP who are scientific advisors to Proxima. It was wonderful to spend time recently in Munich with a team who have been working on fusion for a combined 200 years!

Proxima is taking a simulation-first approach. The design space for stellarators is vast and there is likely a significantly better stellarator design waiting to be discovered prior to building a powerplant. I believe a combination of advanced simulation and the latest superconducting materials will allow Proxima to design the most high performance, grid-ready fusion reactor in the world. 

Europe and the world need fusion as soon as possible. Time to accelerate! This is exactly the kind of mission we want to support at Plural and I am thrilled to be leading the round alongside UVC Partners with participation from Wilbe, HTGF and Torsten Reil.

See also coverage today in the FT, Handelsblatt and Il Sole 24 Ore.

[1] https://www.fusionenergybase.com/article/measuring-progress-in-fusion-energy-the-triple-products

[2] Kikuchi and Azumi, Frontiers in Fusion Research II, Springer, Berlin, 2015

[3] Wolf et al., Physics of Plasmas 26, 082504, 2019.