New neutron source aims to be top in energy and environmental stewardship

Renewable, recyclable, responsible. That is the motto of the European Spallation Source (ESS). The ambitions to build the facility to be energetically self-sufficient and to have as small a carbon dioxide footprint as possible are, at least in part, what landed the project for Lund, Sweden, last year.

The ESS will be the world’s most powerful neutron source. “We will deliver a factor of five higher in power, and a factor of six in neutrons per proton, giving 30 times the neutron intensity of the SNS [the Spallation Neutron Source in Oak Ridge, Tennessee],” says ESS director Colin Carlile. The incident proton pulses that hit a target and knock out neutrons for experimental use will be longer at the ESS than at other sources—2 ms compared with about 1 µs at the SNS, the Japan Proton Accelerator Research Complex, and ISIS in the UK. Longer pulses are the best route to neutron economy, says Carlile. “With short pulses, you have to cut down the intensity to maintain sharp pulses. With long pulses, you basically exploit the natural time it takes for neutrons to slow down.” Adds Hague-based Peter Tindemans, an independent adviser on science, technology, and innovation policies and chair of the board of the ESS Preparatory Phase, “It’s becoming clear that long pulses can do almost everything short pulses can do, and many other things too.”

Now, two decades in the planning, and after a failed bid to build it in 2002, the ESS finally looks like it will go forward (see Physics Today, June 2008, page 22 ). A refinement of the earlier ESS design is under way. Construction is expected to begin in 2013, the first neutrons would fly in 2019 with 7 of the 22 planned instruments online, and the machine would be fully operational in 2025. Half of the funding is being guaranteed by Sweden, Norway, Lithuania, Estonia, Latvia, and Denmark, which is coordinating the facility’s data management. Pledges from several other countries bring the commitments to nearly 90% of the total cost, which is capped at €1.5 billion ($2.1 billion). Although Germany, Italy, France, and Spain are partners in the ESS, smaller countries have taken the leading role. “It is a significant development in European science policy,” says Tindemans. “It shows that there are some limits to the predominance of the bigger countries.”

Proven technologies

Among the advanced technologies for science that the facility will incorporate are neutron guides, which, Carlile says, “save space so you can fit in more instruments.” Neutron guides were used in the Institut Laue-Langevin, a continuous neutron source in Grenoble, France, in the 1970s but have never been used systematically on pulsed sources, he adds. Because of the shortage of helium-3 (see Physics Today, October 2009, page 21 ), the ESS is also looking into thin-film boron and other alternatives for detecting neutrons. As for computers and remote control, says Carlile, “We have to dream up what will be around in 10 years. We have to hit the moving target relating to instrument control.” For the most part, the ESS will use proven technologies. “Because 5 MW is extremely powerful. You cannot afford to take too many technological risks,” he says.

Likewise, the technologies to be implemented for sustainability purposes will be tried and true. “When I went to the research ministries in different countries, the science was interesting to them. But the thing that made them sit up was when we talked about our sustainability plans,” says Carlile. Still, he adds, sustainability cannot come at the cost of the ESS’s scientific prowess. “We have to reassure our funders that we are not doing research into energy sustainability. If [the funders] feel it’s the tail wagging the dog, they won’t like it at all.”

The biggest energy-saving measure will be capturing and recycling excess heat. “You put 40 MW in and get 20 MW out in waste heat,” says Richard Bengtsson, senior project manager at the global E.ON, one of four energy companies that ESS planners are working with. “All that is typically just vented out to the air.”

“You see all these instances where people are heating and cooling at the same time,” says ESS energy manager Thomas Parker. “We will try to use heat from things that are too hot to heat things that are too cold. If we do this right, we won’t have to build boilers. We hope we won’t have to build cooling towers either. I have a strong vision that we will never heat and cool at the same time.”

Referring to the “renewable, recyclable, responsible” motto, Parker notes that the most basic aim is to be responsible—that is, to use as little energy as possible. In line with the European Union’s 20-20-20 initiative to reduce energy consumption and greenhouse gas emissions by 20% and to have 20% of energy come from renewable sources by 2020, the ESS team is working on reducing the design power needed to 32 MW.

“Low-hanging fruit”

“Our goal for recapturing heat is 60%,” Parker says. Some will be recycled in-house, but the plan is to feed most of it into Lund’s district heating system. “This is the low-hanging fruit,” says Bengtsson. “You invest in heat exchangers to move heat, but you get paid for the heat.” The waste heat from the ESS will provide a quarter to a third of Lund’s heat demand of roughly 1 TWh, according to Mats Didriksson, who is in charge of business development at Lund Energy Group. “It’s tremendously important to both parties.”

Redirecting waste heat from the ESS also means, says Didriksson, “that we can substitute gas fuel with waste energy and reduce emissions in the whole system.” Adds Lars Lavesson, an architect from Lund University who heads up licensing and planning for the ESS, “It’s not just a question of morals. It is highly economical.” In total, says Parker, the energy-saving measures could amount to 7.5% of the construction costs but will save money in the long run.

The ESS and Lund Energy Group are looking into storing hot water underground in limestone aquifers. “If you go down about 70 to 100 meters, the ground looks like Swiss cheese,” says Didriksson. “Put the water there, it works like a storage facility. In the winter, when you have demand for the energy, you pump it up.”

The ESS plan also calls for buying windmills. In fact, the idea for the ESS’s focus on sustainability was hatched about two years ago around the idea of “owning our own means to produce power,” says Carlile. He and colleagues “were sitting around a coffee table, drawing on paper napkins, and we realized that would give us more control of the research budget. It factors out the fluctuations in energy costs.” Carlile and his team calculate that “25 state-of-the-art windmills, for about €125 million, would supply all the power we need.” The ESS will feed power into the public power grid and take it out, according to need. Another advantage of buying windmills, notes Parker, “is that we’re not just shifting who uses renewable energy. If we bought renewable energy, then the utilities could just sell other customers more energy from non-renewable sources.”

Energy-conscious culture

Besides the big-ticket measures, the ESS is also looking at smaller ways to improve energy efficiency and otherwise be environmentally conscious. Parker is spending a year at the SNS to get ideas for the ESS. “I spend a lot of time going out and feeling things, finding stuff that is hot. It’s a tactile exercise,” he says. “I’m also trying to build up an understanding of flows—benchmarking where the energy is coming from and going. This is nothing but a big plumbing project, as someone at the SNS put it to me.”

Among the smaller-scale measures the ESS is either adopting or considering are green roofs—a mat of sedum, a succulent, which, Lavesson says, will not only act as an insulator but also help control flooding and water runoff caused by introducing buildings and parking lots. The ESS is being built on agricultural land, next to the MAX IV synchrotron light source now under construction. “We are going to plant trees and put in dams to delay storm water drainage. We will probably make it better for wildlife,” says Lavesson.

In the construction process, Carlile says, “we will impose certain environmental standards on our suppliers. We will use nontoxic materials. We will design from the outset to make decommissioning as easy and inexpensive as possible.” The little things add up, he says. “And they have a knock-on effect: They send a signal to staff that we are energy conscious and that the profligate use of energy is not acceptable. They provide a culture which underlies everything.”

In aiming for zero negative environmental impact on the planet, Carlile says he feels “comfortable putting a ring around the facility and even the staff the moment they leave their front doors. We can compute their energy use and include it in the equation.” And he’d like “to include the carbon dioxide emissions cost of bringing users here, but I am not yet sure I can deliver.” One item for which there is no environmentally clean solution is disposal of the target at the heart of the neutron source, which will be radioactive.

When the SNS was being designed in the late 1990s, “we attempted to build in some rudimentary sustainability,” says SNS operations manager Frank Kornegay. “But at the time, any additional costs associated with energy-efficient this or reduced that was considered fair game to cut to meet the budget.”

Now, Kornegay adds, “the science community seems more interested in energy efficiency. And it’s not always more expensive. The ESS will build in their goals upfront. That is the way to go. It forces engineers and architects out of their comfort zone and frees them to be really innovative.”