Nuclear fusion: the start-ups chasing energy’s holy grail

Nuclear fusion is the process that powers the sun; the hope is that it could also power our homes

Nuclear fusion: it’s the energy source that has powered our sun for billions of years. Now, it’s the bright star scientists are following to save us all from fossil fuel dependency.  

Natural gas is the National Grid’s main resource, used to power 41 per cent of the UK’s electricity. Globally, 80 per cent of the world’s energy is derived from fossil fuels.  

With the Government’s net-zero aims for 2050 and beyond, energy suppliers have been set a target to produce net-zero energy by 2035.    

Bioenergy, offshore wind and nuclear energy will almost certainly have to do most of the heavy lifting to meet that target. For the long-term vision, though – and it could take decades – scientists are working to crack the code that could give us the “holy grail”: a limitless amount of clean energy.  

What is nuclear fusion?  

Very simply, nuclear fusion is the act of combining two light atoms against one another, creating a new, heavier one. This process lets off an abundant amount of energy.  

Nuclear fusion is not to be confused with nuclear fission, which splits atoms rather than fusing them. Fission gave birth to the atomic bomb and existing nuclear power. It emits harmful radiation and produces radioactive waste. The by-product of a nuclear fusion reaction is helium, and there’s not much to worry about a gas which is used to fill party balloons.  

The reason nuclear fusion is so hot and desirable right now compared to existing renewable energy sources is because the amount of clean energy it could produce if commercialised is unprecedented. There would be enough energy produced to power homes for thousands of years and it would be completely free of carbon.  

History of nuclear fusion  

The theory of nuclear fusion was first speculated in the 1920s when British astrophysicist Arthur Eddington published a paper suggesting stars drew their energy from the fusion of hydrogen into helium. At the time, what stars consisted of and the source of their energy was a complete mystery. 

One of the brains behind the atomic and hydrogen bomb, Hans Bethe, later went on to prove this theory in the lab – consequently winning a Nobel Prize.  

In the following decades, active efforts were made to replicate the nuclear fusion process using the Soviet-born tokamak, a doughnut-shaped machine which uses magnetic fields to confine a plasma – a hot gas of ions and free electrons.  

It was time the UK got in on the act, and Culham, near Oxford was given the honour of being the UK’s laboratory for nuclear fusion research. The sleepy village’s airfield came under the wing of the UK Atomic Energy Authority (UKAEA) in 1960 and transformed into the Culham Centre for Fusion Energy (CCFE).  

It was at here that the Joint European Torus (JET) project was introduced in the 1980s, a pan-European research project and home to the world’s most advanced tokamak.  

JET’s success ultimately led to the international nuclear fusion research project ITER (the International Thermonuclear Experimental Reactor) in southern France. The brainchild of Mikhail Gorbachev and Ronald Reagan, ITER will be the largest tokamak in the world once fully completed in 2035.  

Where are we currently with nuclear fusion?  

The aim for the international community is to achieve a breakthrough in commercialising nuclear fusion. That’s difficult, and there’s a decades-old joke in the nuclear fusion industry that commercial fusion is always about 30 years away. 

To achieve it, scientists need to create more energy from nuclear fusion than it takes to power the reaction.   

At the dawn of 2022, scientists claimed a major nuclear fusion breakthrough when JET produced the most amount of fusion energy than ever before.  

Although it still took more energy to use than to produce, scientists claimed this could be overcome when plasmas are scaled up – like at ITER, which hopes to achieve breakeven and then a ten-fold return on power.  

At the end of the year, scientists in California then achieved a net energy gain from a fusion reaction for the first time in history using 192 lasers rather than a tokamak – what is known as inertial fusion. However, the total energy needed for the lasers and the project itself still consumed more energy than was produced. 

In April 2024, South Korean scientists announced a world record in the amount of time they sustained a temperature of 100 million degrees Celsius – seven times hotter than the core of the Sun – during a nuclear fusion experiment.

The temperature was sustained for 48 seconds during tests between December 2023 and February 2024 – beating the previous record of 30 seconds set by South Korean researchers at Seoul National University in 2021.

In the same month, the US and Japan agreed to partner to accelerate the commercialisation of nuclear fusion by tackling scientific and technical challenges together via their universities and private companies.

For fusion to be truly commercially viable, the energy output would need to be significantly more and over a much longer period.  

That achievement has let inertial fusion into the room, though, which to date has only attracted a small slice of nuclear fusion investment. Something which will now likely change. 

To scale up the UK’s fusion operations, the Government has announced that West Burton in Nottinghamshire will be the site for the UK’s prototype fusion energy plant – an area currently dominated by a large power station – with the aim of being built by 2040. UKAEA will produce a concept design for this by the end of this year.   

The plant will be the home of the STEP programme (Spherical Tokamak for Energy Production) which the UK Government will pump £220m to. 

Who’s developing nuclear fusion in the UK? 

Tokamak Energy  

Based down the road from Culham, Tokamak Energy is developing tokamaks and high temperature superconducting magnets, pursuing commercial fusion.  

A spin-off from CCFE, the company employs a team of experts from the UK and around the world.    

“Tokamak Energy aims to demonstrate clean, grid-ready power by the early 2030s,” its CEO Chris Kelsall tells Growth Business. “We’re looking to create significant amounts of energy to power future electricity grids, provide heat for hard to abate industrial sectors and create clean hydrogen for a range of applications.  

“Our objective is to have a solution that can be low cost, and genuinely deployable in many countries to address climate change and energy security.” 

Tokamak Energy signed an agreement with UKAEA in October to closely collaborate and will build a new tokamak at Culham, due to be fully operational in 2027. 

“Our ST80-HTS advanced prototype will demonstrate the advantages of the spherical tokamak with HTS magnets, informing and helping us to optimise the design of our fusion pilot plant,” Kelsall says. 

“The ST-E1 fusion power plant is targeting the early 2030s. Its core mission will be Q greater than around 25, and to demonstrate the capability to put electricity into the grid ahead of the first of a kind device in the mid-2030s.” 

“Q” is the symbol for fusion energy gain. For perspective, ITER is setting its sights on 10, meaning a ten-fold return on power. 

“From there, we are looking at global deployment.” 

First Light Fusion  

Based at Culham, First Light Fusion is a start-up focusing on inertial fusion – the method which saw the breakthrough in California.  

In January, it signed an agreement with the UKAEA to build a demonstration facility – also at Culham – at a cost of £30m.  

Over the last 12 years, the business has grown from a research-focused university project to a fully-fledged company that has developed not only a new approach for how to make fusion energy work, but what it believes is a sustainable business model based on its technology. 

“We take an innovative and unique approach to fusion,” the company says. “Our approach, a form of inertial confinement fusion called projectile fusion, creates the extreme temperatures and pressures required to achieve fusion by compressing a target containing fusion fuel using a projectile travelling at a tremendous speed.  

“This differs from approaches pursued by other mainstream fusion companies in that it doesn’t involve using complex, energy-intensive, expensive lasers, or magnets. First Light’s approach is simpler, cheaper, more energy-efficient, and has lower physics risk.” 

First Light co-founder and CEO Nick Hawker drew inspiration for this confinement process from the pistol shrimp, a crustacean which clicks its claw to form cavities or bubbles in the surrounding water, producing a shockwave which stuns its prey. The air inside these cavities is heated as they implode, causing a plasma to form. Apart from supernovas, it’s the only known example of inertial confinement in nature that we know of.  

“Our equipment is relatively simple, built-in large part from readily available components. We believe this approach accelerates the journey towards commercial fusion power as there is a large amount of existing engineering that can be leveraged and reused to realise its proposed plant design.” 

Is there enough funding for nuclear fusion?  

Investment into nuclear fusion is heating up. More was invested in nuclear fusion in a 12-month period than in the past decade last year with £2.5bn and £1.6bn invested respectively.  

“Support for our technology has really taken off in the past two years,” Kelsall says. “The level of awareness, interest and engagement with the investment community has been palpable. 

“We’re currently evaluating opportunities with potential financial investors and strategic partners to support our plans to demonstrate clean, grid-ready fusion power by the early 2030s.” 

Most nuclear fusion funding comes from venture capitalists and high-net worth individuals, prompting physicists to ask the question of whether the Government, too, can do more to fuel the industry.  

The research centre in Culham has been publicly funded through UKAEA, which in recent years has been a hotbed of public-private partnerships.  

According to the Department for Business, Energy and Industry Strategy, the UK economy has gained £1.4bn from its £346.7m investment into fusion energy between 2009 and 2019.  

Despite this, the level of investment in fusion is still dwarfed by mainstream energy sources. 

What are the advantages and disadvantages of nuclear fusion?  


  • Produces a plentiful supply of clean energy  
  • Doesn’t produce radioactive waste, like nuclear fission  
  • Get it right, and it’s a fantastically cheap source of energy – one estimate claims it would cost £0.02 per kilowatt hour. To put that in context, for the same amount of energy electricity costs 34p and gas 10p 


  • Barring some miraculous breakthrough, nuclear fusion won’t be able to help global targets to reduce emissions 
  • If there aren’t any significant technical and technological advances, nuclear fusion will not be feasible in its current state  
  • We are in unchartered waters and any negative unforeseen consequences of commercial use of it could yet reveal itself 

What are the chances of using nuclear fusion to power the grid in future?  

Because of timeframe scientists are working on, around a quarter of scientists working at the JET facility are at the early stage of their careers, so they can hand down the baton of knowledge to the next generation.   

First Light Fusion is more optimistic, betting on commercial fusion being available within the next 10 years because of the number of projects working on it around the world.  

The UK’s STEP project is aiming to connect to the National Grid in the 2040s, while California-based TAE Technologies, the world’s largest fusion company, is aiming to have a commercial power plant by 2030.  

The International Atomic Energy Agency (IAEA), though, say widespread commercial use of nuclear fusion is expected to take place in the second half of this century, depending on funding and technical advancements. That makes it about 30 years away.  

More on renewable energy funding   

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Qatar set to launch £1.5bn green energy fund in UK The fund will be part of a larger £4bn investment from the Qatar Foundation into the development of a green energy R&D facility

Dom Walbanke

Dom Walbanke

Dom is a feature writer for Growth Business and Small Business, focused on matters concerning start-ups and scale-ups. He has also been published in the Independent, FourFourTwo magazine and various lifestyle...