6

Energy and Environmental Management

The scientific community, particularly in particle physics, is increasingly aware of the need to continue optimizing its use of resources. This includes reducing the energy footprint of accelerators, detectors, and computing infrastructure, as well as innovating new technologies for practices with broad applicability outside the field.

FUTURE ACCELERATORS AND EXPERIMENTS

By far, the largest impact associated with particle physics is that of large accelerators. The main challenges associated with the development of the next generation of accelerators and experiments for experimental particle physics—in particular, Higgs factories and energy frontier colliders—are cost, human resources, and sustainability. In the long term, sustainability may be the most challenging, because it comprises both electric power needs and environmental impacts and, as such, it directly affects the operating costs of a facility as well as the integration and acceptance of large scientific facilities in local communities.

The estimated power needs for the proposed future high-energy accelerators are in the range of ~100–300 MW for Higgs factories, ~300–550 MW for future energy frontier colliders (Muon Collider, Super Proton-Proton Collider, Future Circular Hadron Collider [FCC-hh]), and ~450 MW–1 GW for the wake-field colliders (plasma and laser driven). These power consumptions are comparable to that of a U.S. city with a population between 300,000 and 1 million and, hence, are both significant and impactful. In addition to power consumption, there are significant environmental impacts, including major tunnel and civil construction, heat waste and recycling, water consumption, and waste management and recycling, including radioactive waste.

Sustainability in accelerator design includes efficient technologies to minimize power consumption and environmental impact. There is a coherent, growing community effort to address sustainability issues both in Europe and in the United States. A useful figure of merit is luminosity, a proxy for scientific data collection, per power usage, as considered by the Snowmass 2021 Collider Implementation Task Force.¹ Figure 6-1 summarizes the luminosity per power consumption for several proposed collider projects.

The construction of large accelerators requires concrete, steel, and other raw materials, all of which result in environmental emissions. These can be as much as halved by employing recycled materials and new, low-emission methods for concrete production. An effort to reduce the impact of the Future Circular Lepton Collider, for example,

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¹ T. Roser, R. Brinkmann, S. Cousineau, et al., 2022, “Report of the Collider Implementation Task Force,” https://doi.org/10.48550/arXiv.2208.06030.

has already decreased the expected production of CO₂ by 500,000 tons,² and further reductions could come from measures such as reducing the thickness of concrete slabs, reducing the steel content, and selecting low-impact sites.

In addition to overall design optimization for sustainability, it is important to develop technologies for all subsystems that are far more efficient than the technologies used today.

The main power drivers of an accelerator are the radio frequency (RF) systems, which are necessary to transform grid power into a longitudinal field to accelerate the particles, and the magnet systems, which are necessary to generate the transverse magnetic fields that bend and focus the particles. In current and future accelerators, superconducting cavities and superconducting magnets are the most efficient in reaching high accelerating gradients and high magnetic fields respectively. Therefore, the efficiency of the cryo-plants needed to cool the systems

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² D. Mauree, 2024, “FCC – Carbon Budget Study,” presentation at the Tenth Future Circular Collider Conference, June 3, https://indico.cern.ch/event/1298458/contributions/5981426/attachments/2876462/5037578/100196.09_FCC_Carbon_budget.pdf.

to produce superconductivity is also of paramount importance. The development of efficient RF, magnets, and cryogenics systems is key.

The efficiency of RF power generation is presently in the range of 30–60 percent; improving the amplifier efficiency and reducing the impact of microphonics may push the efficiency to more than 80 percent. The use of permanent magnets where appropriate, and research and development (R&D) on high field superconducting magnets is needed to increase magnet efficiency. The use of high-temperature superconducting magnets and RF can reduce the energy consumption of cryo-plants.

The largest dividends in increasing the overall efficiency of accelerators and colliders can be achieved by reducing the waste of beam power that is either dumped (in linear colliders) or radiated away by synchrotron radiation (in circular colliders). The use of energy recovery linacs, for instance, can almost entirely eliminate the wasted power by recovering the beam energy with appropriately phased cavities.

In general, a multipronged approach must be taken in developing the technologies necessary to make future accelerators affordable and sustainable. Sustainability must also be considered in land use for the siting of future accelerators. Planning for new facilities and new laboratories must be done hand-in-hand with local communities, and synergies (such as heat recovery to warm local households) should be identified and implemented.

As for accelerators, researchers must change their approach to and minimize the impact of particle detectors. Current detectors in particle physics mostly use fluorinated gases as the active medium for some of their components as well as for their cooling systems; these gases are harmful to the environment, and efforts are being made to decrease their use. At CERN, given that the electricity source is nuclear, greenhouse gas emissions are mainly due to gas leaks from the Large Hadron Collider detectors.

For current and future detectors, identifying environmentally friendly gases that meet the requirements for use in particle detectors will be impactful. These requirements include being non-flammable and low in toxicity while maintaining detector performance, long-term stability, and radiation hardness. Alternatively, detectors of the future need to be designed with sustainability with respect to detector gases in mind.

PARTICLE PHYSICS FOR SUSTAINABILITY

Particle physicists are increasingly focusing on sustainability within their own research with broader applications. This includes the development of advanced models for understanding Earth’s temperatures, atmospheric conditions, and ocean dynamics. Research in physics is also driving innovations in clean energy, such as improved photovoltaic devices and materials development.

Energy management is essential to particle physics facilities. In this context, guidelines for the field of particle physics include the following:

• Laboratories and projects should develop and implement an energy management plan, aiming at reducing energy consumption with time.
• The approval process of new projects should consider the sustainability of energy use and management as one of the criteria.
• Resources should be allocated toward R&D on technologies that may help the field and society to improve energy efficiency.

Department of Energy national laboratories currently have energy management plans—for each laboratory as whole and for projects. As an example, the Proton Improvement Plan II project at Fermi National Accelerator Laboratory (Fermilab) has a sustainability effort that includes goals for energy management, energy efficient technologies, campus and building management, energy recovery, and waste heat recovery.

An effective energy management strategy for the field would prioritize the following goals:

• Maximize renewable energy use, and where not possible, opt for low-carbon sources like nuclear power.
• Design new equipment and facilities with energy efficiency as a fundamental criterion from the outset.

• Regularly update facilities with the latest energy-saving technologies, such as
  • Permanent and high-temperature superconducting magnets
  • High-efficiency power sources
  • High-Q RF cavities
  • Efficient cooling systems
  • Data centers with optimal power usage effectiveness, aiming for a ratio as close to 1 as possible
• Recycle waste energy from cooling systems to heat adjacent buildings, utilizing heat pumps.
• Optimize facility operations by aligning shutdowns and maintenance with peak energy demand times in society, ensuring resources are appropriately allocated for these measures.
• Continue to improve data management, as well as the software codes used by the community, to allow the software to run more efficiently on the most advanced hardware platforms.
• Continue to develop and extend the use of machine learning and artificial intelligence technologies, which contribute to reducing computing resources needs.

Technological advancements in particle physics, particularly in high-field superconducting materials, are poised to revolutionize energy efficiency. High-temperature superconductors enable efficient electricity transport through compact cables, facilitating innovations in clean air transport and data center operations.

In parallel, the scientific community is re-evaluating traditional practices to embrace energy-conscious operations. Reducing travel for conferences and meetings, especially air travel, is a key focus, with an emphasis on virtual collaboration tools. This shift aims to balance the value of in-person exchanges, particularly for early-career scientists.

The pursuit of scientific discovery, spanning the microcosmic to the cosmic, necessitates the integration of sustainability into the design and operation of new research facilities and experiments. Sustainable science is not just an option but a necessity for the future of research and the planet.

Recommendation 8: Funding agencies, national laboratories, and universities should work to minimize the environmental impact of particle physics research and facilities.

While the environmental and energy footprint of particle physics is small when compared to that of society as a whole, not only is it important for scientists to set a good example, but innovations that arise in addressing sustainability in particle physics are likely to have broader applicability. Examples include Fermilab’s development of using electron beams for the destruction of per- and polyfluoroalkyl substances, water treatment, and destruction of toxins in soil and, more broadly in particle physics, superconducting cables for the transport of large amounts of current without losses.