Scalability of fusion reactors. Smaller means sooner
First of all, let us begin with a brief overview of fusion for those who are less familiar with the subject. This process involves a fusion of two hydrogen atoms in order to produce a single atom of helium. Through it, a significant amount of energy is released. It naturally occurs in the sun’s core and once recreated it should be a humongous energy source with a completely sustainable fuel (seawater, isotopes of hydrogen). On top of that, the fuel requirements are much smaller in volume, compared to existing power plants. In order to recreate it, the temperature of the sun’s core has to be reached and surpassed, and the resulting plasma contained by the powerful magnets. This enables the collision of hydrogen nuclei and releases great amounts of energy. Which can be converted to electricity through the same turbine method that is used on current power plants. Since this reaction was already achieved, the current research is mainly focused on decreasing the power input and increasing the output. As well as increasing the reaction time.
A powerful magnetic field remains the most viable means of keeping everything contained in a fusion reactor. To achieve these, tokamaks such as EAST and ITER use a concept that was first invented in the 1950s, employing a ring-shaped design that creates a necessary magnetic field. By now the design is fairly common in fusion research but remains rather inefficient in comparison to the recent developments. China claimed that it’s EAST reactor now holds the world record for the longest sustained fusion reaction at 100 seconds. While France’s Tore Supra, a tokamak as well, holds the record for longest plasma discharge at just over six minutes.
There are two different approaches, as mentioned previously. They differ in the financing, organization, and commercial issues. The most prominent example of the first one would be ITER. It is the largest scientific project in continental Europe. The former are private companies, such as Lockheed Martin, General Fusion and Tae technologies. Which due to their smaller scale should give sooner results, as soon as in 5 years. Those will bring practical, functioning technology that will become more affordable after reaching commercial production. This will affect almost everyone in several ways. First of all, it will enable countries to gradually replace nuclear and thermal power plants that produce significant amounts of CO2. Fusion reactors have no harmful emissions at all. Second, the electricity costs will go down the further the development goes since all of the currently developed power plants will produce considerably cheaper energy. The more fusion is developed the greater its energy output will become in relation to its input, and the cheaper it will be as a consequence. Third, it will be possible to install such power plants, most likely in collaboration with local governments, in developing nations to bring affordable clean energy there. This will enable them not only to improve the household use but allow them to more easily and readily power existing and future factory plants.
MIT Plasma Science & Fusion Center is in the process of developing SPARC — compact, high-field, net fusion energy experiment. It will be the size of the current mid-sized fusion reactors, but with a much greater magnetic field. It is predicted to produce 50–100 MW of fusion power and to achieve significant energy output gain. It would be the first demonstration of net energy gain and would validate the promise of high-field devices. SPARC fits into an overall strategy of speeding up fusion development by using new high-field, high-temperature superconducting (HTS) magnets. Those are capable of giving a much higher magnetic field.
It is currently conducting the research that should lead to the development of the large, superconducting magnets needed for fusion applications. This is done in collaboration with a private fusion start-up company, Commonwealth Fusion Systems (CFS). It will join MIT’s Energy Initiative (MITei) as part of a new university-industry collaboration to execute this plan. The next step would be to use the obtained technology to build SPARC. The conceptual design will have a 1.65m major radius and a 0.5m minor radius. Operating at a toroidal field of 12T and plasma current of 7.5 MA, producing 40–100 MW of fusion power. Its mission is being able to demonstrate break-even fusion production and to show the integrated engineering of fusion-relevant HTS magnets at a meaningful scale.
A certain Italian oil company is investing 62 million USD in Commonwealth Fusion Systems. It aims to bring fusion power in 15 years. “CFS is commercializing fusion using the high-field approach, where we are developing new high-field magnets to make smaller fusion devices using the same physics approach as the bigger government programs. To do this, CFS works closely with MIT in a collaborative project, beginning with developing the new magnets.” It uses powerful magnetic fields to hold in place the hot plasma — a gaseous soup of subatomic particles — to prevent it from coming into contact with any part of the doughnut-shaped vacuum chamber. The experiment is designed to produce around 100 MW of heat in ten-second pulses, enough to power a small city. However, it will not include the systems to turn the fusion power into electricity. MIT scientists anticipate output to be more than twice the power used to heat the plasma. To achieve a positive net energy form of fusion. “Fusion occurs inside a plasma held in place and insulated using magnetic fields,” says Mumgaard. “This is conceptually like a magnetic bottle. The strength of the magnetic field relates very strongly to the magnetic bottle’s capability to insulate the plasma so it can reach fusion conditions. Thus, if we can make strong magnets we can make plasmas that can get hotter and denser using less power to sustain it. And with better plasmas, we can make the devices smaller and more manageable to construct and develop. With high-temperature superconductors, we have a new tool to make very high-strength magnetic fields, and thus better and smaller magnetic bottles. We believe this will get us to fusion faster.”
There is a new generation of large-bore superconducting electromagnets that have the potential to produce a magnetic field twice as strong as those employed in any of the current fusion experiments. Made from steel tape and coated with a compound called yttrium-barium-copper oxide (YBCO), the new superconducting magnets will allow SPARC to produce a fusion power output about the fifth that of ITER but in a device that is only 1/65 in volume. By reducing the size, timeline and organizational complexity required to build net fusion energy devices, YBCO magnets will also enable new academic and commercial approaches to fusion energy.
SPARC is an evolution of a tokamak design that has been studied and refined for decades, including work at MIT which began in the 1970s. It will pave the way to the world’s first true fusion power facility with 200MW capacity, on par with current commercial power plants. Which will cost an estimated 3 billion USD to develop by 2033. Their smaller scale will enable the cheaper path to consumer electricity from the fusion energy. “There is still research to be done, but the challenges are known, new innovation is pointing the way to accelerate things, new players like CFS are bringing a commercial focus to the problems and the basic science is mature” says Bob Mumgaard, CEO of Commonwealth Fusion Systems (CFS)
Lockheed Martin’s concept uses a high faction of the magnetic fissure pressure for its reaction. The current device is 10 times smaller in comparison to their previous concepts. It relies on a magnetic bottle and can sustain temperatures of up to hundreds of millions of degrees and release energy in a controlled fashion. Similarly to the current power plants, it will give heat that will drive the turbine and produce electricity. It will achieve this by replacing the combustion chambers with simple heat exchangers. The turbines can also be used to generate propulsive power. This will have several interesting areas of potential practical application. Including planes, enabling them to obtain an unlimited range and endurance. Large sea ships, effectively replacing nuclear-powered and other engines. It should also speed up space travel, shortening the journey to Mars to just one month. On top of that, it will enable a 60 percent reduction in desalination costs. Making clean water more available.
Lockheed Martin is currently in the process of constructing its newest experimental reactor — T5. “This year we are constructing another reactor — T5 — which will be a significantly larger and more powerful reactor than our T4.” Their designated company — Skunk Works has already built four different test reactor designs. T5’s main purpose will be to test whether it can handle the heat and pressure from highly energized plasma inside. If all goes well it should go online towards the end of this year.
The CFR program is built around the newly patented reactor which uses superconducting coils to more effectively generate a magnetic field that contains the heat and pressure of the reaction. Lockheed Martin’s hope is that it will overcome the past challenges of nuclear fusion. Such as extremely high temperatures that generate extremely high pressures inside the vessel.
“The problem with tokamaks is that “they can only hold so much plasma, and we call that the beta limit,” McGuire says. Measured as the ratio of plasma pressure to the magnetic pressure, the beta limit of the average tokamak is low, or about “5% or so of the confining pressure,” he says. Comparing the torus to a bicycle tire, McGuire adds, ‘if they put too much in, eventually their confining tire will fail and burst — so to operate safely, they don’t go too close to that.”
Being much smaller than most fusion reactors CFR will avoid these issues by tackling plasma confinement in a radically different way. Instead of constraining the plasma within tubular rings, a series of superconducting coils will generate a new magnetic field geometry in which the plasma is held within the broader confines of the entire chamber. Superconducting within the coils will generate a magnetic field around the outer border of the chamber. ‘So for us, instead of a bike tire expanding into air, we have something more like a tube that expands into an ever-stronger wall’ McGuire says. The system is therefore regulated by a self-tuning feedback mechanism, whereby the farther out the plasma goes, the stronger the magnetic field pushes back to contain it. The CFR is expected to have a beta limit ratio of one. ‘We should be able to go to 100% or beyond,’ he adds.”
The design will eventually be small enough to fit inside a shipping container and still be able to power a Nimitz class aircraft carrier or up to 80000 homes. On top of that, current patent documents confirm that the eventual size reduction will reach a point where it will be small enough to be installed in a large aircraft. Not to mention that it will require far less fuel, a fraction of what current reactors use. The fuel will need less refinement as well.
Founded in 2002, General fusion uses a pulse-powered system similar to a diesel engine. Its total cost will be several hundred million dollars. However, it already has several large individual investors like Jeff Bezos and companies like Cenovus Energy. That have provided 127 million USD overall, according to Crunchbase.
The main plan of General fusion lies in making a 70% scale pilot plant to test the viability of generating electricity. This construction will be done over the next five years. Followed by 18 months of testing. The produced model will have around 500 2–3 meter pistons and it will run on deuterium fusion, without adding tritium.
TAE Technologies is a company based in Foothill Ranch, Califronia that was established for the purpose creation of aneutronic fusion power. Their past C-2U machine met the ‘Long Enough’ reaction standard, while their current Norman’s (C-2W) plasma has reached nearly 20 million degrees Celsius. Twice the C-2U max number and greater than the temperature of the sun’s core. They also collaborate with Google on machine-learning simulations of plasma physics that should provide a considerable speed up to the process. In addition to employing US Department of energy’s supercomputer program to boost their data-processing resources.
They aim for a hydrogen-boron fusion reaction, cleaner than deuterium-tritium reaction. With its target plasma temperature eventually reaching 3 billion degrees Celsius. “It is profound to see TAE’s scientific innovations bear out in Norman’s performance,” Specker said in the news release. “Our remarkable progress signals the reality of a future powered by fusion energy, and hydrogen-boron is as safe and clean a fuel source as you can find. It’s a win-win for us all.” It involves shooting “smoke rings” of high-energy plasma at each other within a magnetic confinement chamber, with neutral beams directed into the chamber. With its commercialization scheduled for 2023, according to their plan, the next device will be called Copernicus and will demonstrate the net energy gain. “What we’re really going to see in the next couple years is actually the ability to actually make net energy, and that’s going to happen in the machine we call Copernicus,” he (TAE CEO — Michl Binderbauer) said in a “fireside chat” at UC Irvine.
The above-mentioned machine learning computers are used to decide on the experiments. Those perform 60 beam shots per day and get 10 gigabytes of data per shot. Being able to process the data in 3–4 seconds.
TAE Technologies’ current plans involve going to higher temperatures for safer hydrogen-boron reactions. Additionally, they have already raised 700 million USD and have a 3 billion USD valuation. They are fully privately funded and they own the largest, most modern machine in the U.S. and plan to license the technology
Their end goal is utility-scale electricity that is price-competitive with the current alternatives. The capacity of future commercial power plants will be between 350 MWe and 400 MWe. Also, in the last 20 years they were evolving an advanced beam-driven field-reversed configuration (FRC) approach.
Helion Energy grew from research at the University of Washington. Launched with a 5 million USD research fund. They plan to build fusion reactors in Washington and deploy them at industrial facilities. They have already raised 30 million USD in the past three years that will be enough to get Helion through the debut of its 50-megawatt break-even prototype.
In 2018 Helion reported its fifth-generation plasma machine — Venti. “Venti aims to compress a plasma target to 20 Tesla and to fusion temperatures” according to David Kirtley — CEO of Helion Energy. While the sixth-generation machine named ‘Trenta’ (presumably) is already being designed. The seventh-generation machine will hit net energy gain. Currently, it does not have a specific date for when its construction phase will be complete but they aim for 2021.
The goal of Helion energy is to achieve the commercial Magneto-Inertial Fusion. This will combine the stability of a steady magnetic fusion and the heating of pulsed inertial fusion, at a smaller and lower cost than existing programs. Those two reactions will be magnetically accelerating plasma together and then compressing it once every second. Such a breakeven fusion machine would cost only 35 million USD, which is a rather small price compared to other projects. Helion has already raised that sum and will be able to complete its next machine with it.
However, they will require another 200 million USD for a commercial power plant development in order to start building such by 2024. Therefore, right now they would need to raise that sum in order to be on schedule. Since funding is the main problem that may stretch the dates.
Their technology — “The fusion Engine” will use helium from the engine exhaust, along with deuterium fuel from seawater. It will be heated to become plasma and then compressed with magnetic fields to reach fusion temperature. This will reach more than 100 million degrees and will allow them to investigate staged magnetic compression of field-reversed configuration (FRC) plasmas.
The power switching electronics in wind turbines and in other energy systems help Helion energy. As well as recent advancements in high power electronics, developed for the space propulsion and smart grid. Additionally, if better superconducting batteries and materials are created in the future they would allow such reactors to become smaller and more powerful. though Helion energy is fully capable of producing the 2021 design with their current technology that is the next stage of their development plan. They have already proven their technology in a series of prototypes that are generating Deuterium-Deuterium albeit on a small scale. Those run on the advanced Helium-3 fuels and by capturing the alpha particle energy directly the company eliminates the need for steam turbines and cooling towers.
Other large projects. China
There is a large governmental project in China that also works towards bringing fusion energy — Experimental Advanced Superconducting Tokamak (EAST) also known as HT-7U. It was activated by Hefei Institutes of Physical Sciences of the Chinese Academy of Science in 2006.
They employ lower hybrid wave heating, electron cyclotron wave heating, ion cyclotron resonance heating and neutral beam ion heating. The team that operates it has managed to heat the reactor’s internal plasma to 100 million degrees. Six times hotter than the sun. That temperature was held for 10 seconds. The team used a high-temperature experiment to study the way plasma behaves at such high temperatures. Which in turn could improve the future reactor designs.
The Chinese government plans to have it fully operational this year. “On Sunday Duan Xuru, an official at the China National Nuclear Corporation, announced during the annual session of the Chinese People’s Political Consultative conference that engineers would wrap up construction on the nation’s HL-2M Tokamak in 2019.”
German Wendelstein 7-X has been 10 years in construction by the Max Planck Institute of Plasma Physics in partnership with the University of Greifswald. Being the largest stellarator - the device that moves plasma along a route containing twists and turns that are designed to keep plasma stable. With 400 million EUR invested in it, this project will not be used to produce electricity but will be used to evaluate the main components of the future power plant.
It has already produced record-high values for both plasma density (2 x 1020 particles per cubic meter) and plasma energy content (more than 1 megajoule). While also achieving the longest plasma discharge time on record for a stellarator (100 seconds) and a plasma temperature of 20 million degrees Celsius (36 million degrees Fahrenheit). They anticipate achieving 30 minute plasma discharge by 2021.
It consists of a toroid comprising of 50 non-planar and 20 planar superconducting magnetic coils that are used for adjusting the magnetic field that prevents the plasma from colliding with reactor walls. They aim for a plasma density of 3x1020 particles per cubic meter and a temperature of 60–130 Megakelvin (MK).
To conclude, there are several major projects that should bring fusion energy rather sooner than later. It is very likely that the more working prototypes are created, the more investments and government incentives they will attract. Particularly the ones that will manage to produce more energy than they require. Thus, creating the snowball effect of greater investments, followed by greater scientific progress. All until the point where the first commercially viable reactors are produced. Which, when reached, should start to pay off for themselves and start spreading across multiple countries. Since the energy that they will produce will be considerably cheaper than nuclear counterparts and more efficient than both solar and wind. In addition to that, it has no attached prejudice as nuclear power does and, most importantly, they have no harmful waste that might potentially damage the environment. Their fuel is self-contained and produces no highly active, long-living nuclear waste or CO2 emissions. Making it a very attractive option for our sustainable and clean future.