Posted on April 30, 2020 by Cameron Tarry

What if we could harness the reaction at the core of the sun to generate power? For decades, scientists have been trying to do just that: create a fusion generator that could supply the world with unlimited clean electricity from hydrogen molecules found in seawater. In the past decade, innovative designs and scientific breakthroughs have brought this goal close enough to impact our electricity system on a climate-relevant timeline. This 101 explores how fusion works, what has happened lately, and why fusion could help reduce emissions.




A fusion reaction is basically a miniature star. Fusion is the collision of extremely heated atoms; when the atoms are heated, they turn into plasma, the super-charged state of matter where electricity can flow. By fusing a tiny amount of fuel, usually hydrogen, and containing that reaction, clean energy can be generated.

Fusing atoms isn’t the problem – the challenge has been doing this efficiently so the reaction produces more energy than it consumes. Fusion requires a combination of high heat and intense pressure; the sun has 330,000 times the mass of Earth and a temperature of 30 million degrees Fahrenheit1. That’s 8,500 times hotter than a coal or natural gas plant! Since the sun’s mass can’t be recreated here on Earth, the temperature has to be cranked way up — about six times (or more) hotter than the sun. The extremely low volume of fuel means the reaction is safe at such high temperatures. Pressure and inertia help, too: superconducting magnets, lasers, or piston-driven pressure can force the atoms together to efficiently fuse under Earth’s conditions.



One problem, different approaches

Creating a self-sustaining plasma without the sun is kind of like trying to keep a campfire going in the wind and rain. We know how to make sparks, but turning those sparks into a roaring campfire needs effort and protection from the outside in normal conditions. Add in wind and rain, and you’re putting in a ton of effort to keep the tiny sparks alive. Plus, think of how temperamental those sparks are! That’s fusion — we can get it going, but reaching a self-sustaining reaction at a large enough scale has not yet happened in Earth conditions.

So far, no one has been able to “keep the campfire going” (create a “self-sustaining” plasma) here on Earth at a level that could produce energy because there are so many factors to hone to get it just right. Fortunately, scientists have brought this goal closer than ever in innovative ways in the past couple of years:



Beyond the science: a fusion power plant

Regardless of its form, one thing is clear — a fusion energy system would look very different from a fission reactor. Different physics means different needs.

Until recently, the main commercialization path for this technology was through ITER, a U.S. co-founded international project to build an experiment in France that will prove how to burn plasma. ITER gives U.S. scientists the invaluable chance to study plasma through international collaborations and provides a market for specialized U.S. industries.2 In addition to ITER, though, some startups are trying to prove fusion energy on a quicker timeline and at a smaller scale. There are over twenty fusion startups in the U.S. alone, each with their own take on a design from shapes to materials. Scientists and investors increasingly believe that these alternate approaches could unlock not only the science behind a fusion plant, but the market for fusion-based electricity.3

Once online, fusion plants could make a global impact. A fusion plant could be small, cost-competitive, and zero-carbon, meaning fusion could help countries around the world decarbonize at a lower cost than other options.

A fission reactor vs a tokamak-based fusion reactor, one of the designs for a fusion core.
A fusion plant could take advantage of existing power plant infrastructure while dramatically differing in core design.


Environmental Potential

First, fusion’s fuel — hydrogen — renders massive environmental benefits. It’s a clean generator powered by the most basic element.

      • Zero-emission electricity: Because it’s fueled by hydrogen, fusion generates zero greenhouse gas emissions from its energy production. The reaction is simple physics: two hydrogen atoms collide; they produce neutrons, helium, and heat; the neutron hits a “blanket” made up of lead and/or lithium; and the neutron and lithium react to form hydrogen (tritium) that is re-injected as fuel. It’s a cycle of clean elements!
      • No long-lived radioactive material: Fusion’s neutrons are high speed and therefore do not produce the high-level radioactive material produced by fission’s slower speed neutrons. Tritium produces radiation that can be stopped by a single piece of paper and is already safely used around the world — from exit signs to biomedical research.4,5 Parts of the fusion system will be irradiated by the spare neutrons, requiring disposal, but at a manageable level onsite for a few decades, after which they could be moved to any conventional waste disposal site.

Fusion also has the potential to help decarbonize not only the U.S. economy, but the world:

      • Baseload energy: When used for electricity, a fusion plant is a firm electricity source, meaning it can run constantly regardless of weather or immediate need. Once a fusion reaction has a self-sustaining plasma it can continue mostly powered by its own reaction.
      • Flexible energy: Many fusion companies are designing their plants to be able to ramp up and down in order to respond to needs of the grid. Fusion could provide an emissions-free way to balance solar and wind on the grid when the sun doesn’t shine and wind doesn’t blow.
      • Deep decarbonization: To reduce emissions completely, the world will need to decarbonize difficult-to-reach sectors of the economy. Fortunately, fusion might be able to help: because a fusion reaction itself must reach such high temperatures, it is possible that a fusion plant could supply high-quality consistent heat for industrial processes. Fusion could also help produce synthetic fuel for transportation. These ideas need more exploration but hold significant promise.
      • Non-proliferation: By not using uranium, fusion reactors have limited non-proliferation concerns that can be managed by traditional safeguards around tritium.6 This means the non-proliferation concern with exporting a fusion plant is significantly reduced. A fusion system could thus be exported around the world, opening a trillion-dollar market and helping to decarbonize developing countries.

Economic Potential

Although there is still some unknown, the very basics of a fusion reactor lend to potential savings.

      • Fuel: Running on elements like hydrogen yields advantages. Although tritium must still be processed from common hydrogen, this process could happen on site. Being able to manufacture and store fuel on location makes fusion’s infrastructure both safer and cheaper.
      • Safety: The fundamental physics of fusion on Earth make an accident impossible — remember the wind and rain around a campfire. Additionally, as mentioned, a fusion system’s waste is low-level and shorter-term. As such, a fusion plant needs a fraction of the safety equipment of a fission reactor. That means two things: a smaller plant footprint, making a plant easier to site (and sell), and a potentially shorter regulatory process,7 which nets huge savings.

Currently, auxiliary parts of the plant — containing tritium safely and making more fuel, for example — present the biggest cost unknowns, but the best and brightest are already on it. The Department of Energy is working with private companies on ways to design these components for a cost-effective plant. To read more about some of the ways American innovators are rethinking fusion, check out the work at ARPA-E.

Recent Developments

The wider fusion community, both public and private, has seen concrete action in the last couple of years:

      • The Advanced Research Projects Agency-Energy (ARPA-E) program under the Department of Energy launched Accelerating Low-Cost Plasma Heating and Assembly (“ALPHA”) in 2014 to help develop “new, lower-cost pathways to fusion power.” ALPHA was so successful that ARPA-E recently launched two more programs to further lower the cost of fusion and help develop the components of a fusion reactor. Read more about ALPHA and ARPA-E here, as well as the two newest programs: BETHE and GAMOW.
      • In 2018 the Fusion Industry Association (FIA) was formed, representing over twenty fusion startups. Investors are interested, too — private fusion endeavors have received almost $1.5 billion collectively. To catapult this interest, FIA, Stellar Energy Foundation, and Pegasus Fusion Strategies host workshops looking at fusion’s economic boost for climate sensitive investors, the next of which is planned for Fall 2020.
      • In 2019 the Fusion Energy Sciences program under the Office of Science (fusion is not housed in the Office of Nuclear Energy) started the INFUSE program, which allows developers to benefit from the expertise and facilities of the DOE national laboratories.
      • In 2020 the Nuclear Regulatory Commission (NRC), in coordination with the DOE, is beginning discussions regarding a regulatory pathway for commercial fusion in the U.S. This process was directed by the Nuclear Energy Innovation and Modernization Act of 2019 and will reach a conclusion in the next several years — stay tuned!