Scientists have been studying fusion for decades with the understanding that if we could replicate the process here on Earth, we could create a virtually limitless clean power resource for the world. Fusion is the same process that happens in the stars, when two light atomic nuclei combine to form a heavier nucleus. At extremely high temperatures and pressures, hydrogen nuclei fuse together to form helium, creating enormous amounts of energy in the process. The challenge on Earth is achieving an energy output that exceeds the energy input, often referred to as Q>1. Achieving self-sustaining fusion energy requires that three conditions are achieved, referred to as the “fusion triple product,” which is the product of (1) plasma density (the number of fuel ions in a given volume), (2) confinement time (how long the hot fuel ions are kept together), and (3) plasma temperature (which provides the energy required for the fuel ions to overcome their mutual electrostatic repulsion and come close enough to fuse).
Recently, we have seen a shift from fusion as a scientific endeavor towards commercialization. There are now more than 40 private fusion companies that have emerged with more than $5.5 billion in combined private funding with the goal of delivering fusion energy to market, using several different approaches to achieving commercial fusion energy. Commonwealth Fusion Systems (CFS), which spun out of MIT in 2018, is the largest of these private fusion companies with 600 employees and more than $2 billion in private capital. It is currently building the world’s first commercially-relevant fusion machine called SPARC, on track to be operational in 2025.
SPARC is a machine called a tokamak, one that uses magnets to confine a plasma in which the fusion process occurs. Tokamaks are the highest performing fusion machines that have seen decades of progress. However, in the past, their performance has been limited by magnetic field requiring them to be enormous in size to demonstrate fusion at a commercially relevant level. This size also means long construction timelines and high costs which would not be sensible for commercialization.
Recently, CFS, in collaboration with MIT, has developed and demonstrated a new groundbreaking magnet technology using high temperature superconductors (HTS). These new HTS magnets enable a significantly higher magnetic field, allowing for smaller and less costly tokamaks that can be constructed on a much faster timeline. CFS is now constructing the SPARC tokamak using HTS magnets in Devens, Mass. SPARC has several operating modes that pose a wide range of cryogenic requirements and duty cycles. These include steady-state static loads, increased loads during days-long high temperature bake processes for cleaning, and most demanding of all, the loads associated with up to five fusion pulses per day.
SPARC will demonstrate the commercial viability of fusion. The physics basis verifying that SPARC will achieve net energy has been peer-reviewed and published in the Journal of Plasma Physics. Now the various systems, including cryogenics, are being actively designed, tested and readied for installation at CFS’ fusion campus in Devens. Cryogenic technology plays a pivotal role in fusion, ensuring that superconducting magnets operate at extremely low temperatures. Recent innovations such as HTS have enabled the construction of smaller, more cost-effective fusion reactors like SPARC. Cryogenics is central to the success of these reactors and is actively being refined for various operational modes. And, in the next issue of Cold Facts, CFS is looking forward to diving deeper into how it is working to apply and innovate cryogenics for a fusion future.
Fusion's potential as a clean, virtually limitless energy source is remarkable. Compared to fossil fuels and traditional nuclear fission, fusion offers safety, environmental benefits, and a nearly limitless fuel supply. These attributes make it an essential contender in the transition to a sustainable energy future. As commercial fusion projects progress, it's crucial to consider the economic and environmental implications. Fusion has the potential to revolutionize the energy landscape, offering a cost-effective, low-emission energy source. With international collaborations and regulatory considerations in place, the fusion community is poised to meet global energy challenges, ushering in a new era of clean, sustainable power.
Image: The SPARC facility on the Commonwealth Fusion Systems campus in Devens, Massachusetts will house the SPARC tokamak, which will demonstrate commercially relevant net energy from fusion for the first time in history. The campus also includes CFS headquarters and a 165,000 square foot manufacturing facility where CFS will build all the high temperature superconducting magnets for SPARC. The photo shows a life-sized rendering of SPARC inside the hall in which it will operate. Credit: Commonwealth
