Commonwealth Fusion Systems Presentation 20 Nov 2025

Fusion Energy: Can it help protect Harvard’s Open Space?

  • Darby Dunn, Dr Clayton Myers, Jessica Strunkin of CFS

Intro

  • nice to think about terraforming Mars, but how do we protect the planet we’re currently on
  • Net Zero
    • eliminate 51 billion tons of emissions every year from
      • transportation 16%
      • Food and agriculture 19%
      • Manufacturing 31%
      • Heating and cooling 7%
      • Power 27%
  • Need breakthrough technologies in all 5 areas
    • EVs
    • Vertical farming
    • “Green” steel, concrete - might even be carbon negative
    • Heat pumps
    • Fusion for power (but first solutions all require power!)

Ideal energy source

  • Clean, safe, on demand, scalable, secure
  • Devens project is based on Tokamak – big magnets forcing the fusion
  • Fuel: deuterium (based on hydrogen)
  • 1 bottle of water’s hydrogen could be extracted to power 1 persons’ power needs for entire life

CFS efforts

  • spin-out from MIT
  • physics – completed in 2016
  • Magnet tech – completed in 2021
  • SPARC: under construction, due in Q1 2027 (commercial demo)
    • SPARC is built in Devens
  • ARC: power on grid by early 2030’s (commercial powerplant)
    • will be about twice as large as SPARC
    • Will be built in VA
  • ultimate goal 10,000 of these power plants!

How did CFS come to Devens?

  • 2019 CFS site search for:
    • HQ, R&D, manufacturing, SPARC
  • 2021 closed on the property
  • 2022 CFS-1 completed
  • 2023 ribbon cutting
    • US secretary of energy
    • Congressional delegation
    • MA Lt Governor
  • lots of parallel work, working on magnets, while building Devens, still working on SPARC, but already building in VA for ARC

CFS then and now

  • world’s largest and leading private fusion company
  • Founded in 2018
  • Spun out of MIT
  • Decade of research
  • Over 1000 employees
  • Almost $3B raised
  • They are confident that their magnet technology will enable them to really go live with fusion (and the magnet test worked)
  • About 45 private fusion energy companies (this is a good thing, will generate demand for the supply chain)

SPARC

  • first of a kind
  • Started in 2021
  • 70% complete
  • Global supply chain already engaged
  • On site assembly begun
  • Commissioning begun
  • Q1 2027 (will prove more energy out than in)
  • Land use
    • 46 acres in Devens
    • 90 acres in VA (building will need about 25)

why VA for ARC

  • one of the fastest growing electricity markets
  • Access to interconnection to grid
  • Access to ports and other transportation to supports supply chain
  • Signed power purchase agreements with Google and ENI
  • Site was originally going to be a gas plant, but community shot it down

Clayton Myers - Plasma and Fusion Scientist

  • started work studying plasma flares on sun
  • Worked at a Tokamak in mid-2010’s
  • Worked at Sandia national laboratory (Z facility until 2022)
  • Why did he come to CFS
    • international project in France called ITER
      • may come online in mid 2030’s, may not come together
    • CFS – will do same performance as ITER, but much smaller
    • SPARC will produce same amount of power 10x more than power (Q of 10)
    • ARC will do 50x more than power in (Q of 50)
  • CFS
    • high temperature superconductors (HTS)
      • discovered in late 1980’s but commercially available in 2009
      • CFS has the majority of them
    • supercondcutivity depends on temperature, current density, and magnetic field
    • HTS has higher critical values compared to Lts
    • ITER uses LTS (less power output)
    • CFS having HTS will produce more power, much smaller
  • Tokamak research
    • Decades of tokamak research informs the rellationship between device size, magnetic field, and fusion output
    • Machine cost scales steeply with size (also gets more expensive)
    • MIT has long led the charge on smaller, higher yield tokamaks
  • high field path has long been recognized as more economical path to commercial fusion power (since 1990’s)
    • but fusion community followed LTS because that was what was available, fundamental limit on the steady state field that can be achieved
  • CFS is well into producing the dozens of HTS magnets needed for SPARC, each magnet will process 100 megamps thru the stainless steel of the case, takes specialized steel to handle it
  • He joined after magnet test, working on the diagnostics systems and sensors (his expertise is magnetic field measurements)
  • 2 toroidal field stations of magnets (on each side)
  • SPARC will demonstrate only, but won’t put power on the grid
  • Elsewhere, JET (in UK)
    • only had Q of 0.37 (35mw heating power in, 13 mw fusion power out)
    • SPARC will have a Q of 1.1 in its first campaign but will (11mw in, 12mw out)
    • eventually get to Q of 11 (140 mw of fusion power with 12.8 mw of heating power)

Q&A

  • could SPARC ever be converted to provide power in our area?
    • SPARC is only designed for 30 minutes pulse, not for ongoing power conversion and output
  • how much water does SPARC use?
    • sources of water? Devens utilities and within their capacity
    • Thermal pollution?
  • what are differences in environmental impact between fusion and fission?
    • fission produces highly radioactive waste from the activation, this is fundamental to the process
    • Fusion has a much lower radioactive activation output, the reaction to neutrons can be controlled in choice of materials
    • SPARC will only need about 10 gallons of water for cooling
      • but will overheat after 10 seconds of running, because it doesn’t have production-class cooling
      • SPARC also only has a lower capacity transformer, compared to what ARC will need
    • Tritium has a half life of only 12 years, small amount of waste
    • They are licensed similar to a particle accelerator due to Low amount of activated material
    • After ARC goes live, SPARC will continue to run to do further tests in support of ARC
    • You only need a puff of gas to cool down a fusion reaction