M ajor research facilities such as accelerators and reactors each consume roughly as much electric- ity as a small town — hundreds of gigawatt hours (GWh) of energy per year or more (see ‘Annual energy expenditure’). International and national labs use a total of roughly 3 tera- watt hours per year in Europe and 4 terawatt hours (TWh) in the United States, add- ing up to about the energy consumption of countries such as Estonia or Ghana. This energy use is perhaps these facilities’ greatest environmental impact, greater even than the radioactive waste that many produce. Radio- activity can be contained and handled safely; climate change cannot. The European Spallation Source (ESS) — a neutron source to be built in Lund, Sweden, by 2019, for which I am the energy manager — aims to be the first sustainable such facility. We will use only renewable energy sources to power the accelerator and the lab. We will limit our energy use: so far in the design process we have reduced our energy requirements by more than 20%. And 70% of the energy that we consume will be recovered as usable heat. Many of the specific solutions that we are adopting at the ESS rely on local condi- tions, including a liberalized energy market, a well-developed district heating system, a relatively cool climate and public and politi- cal support. But the project stands as proof of principle that big science can be sustainable science, and it challenges other facilities to live up to the same standards. USE IT, DON’T LOSE IT One area in which there is obvious room for improvement at big labs is the use of waste heat from lab equipment. Water at 40 °C can easily supply buildings with under-floor heating or thermal ventilation, if the right systems are in place. Waste heat of 75 °C can even be used to run cooling air condition- ers. But most labs intentionally destroy this resource. Conventionally, equipment ranging from accelerators to manufacturing machinery is cooled to run at 40 °C or lower. This is in part because early electronics operated best at lukewarm or cool temperatures, and in part to avoid harming aquatic life when the cool- ing water from hotter systems is discharged into natural systems such as rivers. This tar- get has become so firmly entrenched that manufacturers were surprised two years ago when we began asking them if their modern equipment would work efficiently at higher temperatures. No one else had asked. It turns out that many modern systems can work at much higher temperatures, allowing the heat to be saved for reuse, with or without conversion to electrical power, rather than being extracted by a heat pump, dissipated in expensive cooling towers, or dumped into the air or water. Sometimes this requires small modifications, such as using sturdier components, or adding adaptable cooling systems that can handle variable heat loads and deal with rare instances of overheating. At the ESS, we are working to design power systems for our accelerators and helium com- pressors for our cryogenics that can operate at 75–100 °C. One of the challenges is finding the room for extra sets of pipes: some parts of the facility will still need to be cooled to 40 °C for proper operation, so we need paral- lel cooling systems for parts that are cooled to different temperatures. Few places recycle their heat. Instead, they burn fossil fuels to meet their heating and cooling needs. For example, CERN, the European high-energy physics laboratory near Geneva, generates waste heat at 40 °C before disposal. This could be used for heat- ing, but its current system uses pressurized 120 °C water instead. Changing CERN’s entire heating system retrospectively might be too costly, but new buildings could be Cutting science’s electricity bill Large-scale research facilities need to reduce their energy consumption and begin moving towards sustainability, says Thomas Parker. The European Spallation Source, to be built in Sweden, will be powered entirely by renewable energy. ESS 15 DECEMBER 2011 | VOL 480 | NATURE | 315 COMMENT © 2011 Macmillan Publishers Limited. All rights reserved