No, fusion energy will not be “limitless”

Last December, researchers at the US National Ignition Facility achieved what many in the fusion industry call the moment “Wright Brothers“. Using a laser, they irradiated a gold vessel with a microsecond pulse of energy and ended up with about 50 percent more energy than they put in. This process is called fusion ignition, and it is a triumph that has been expected since the 1970s. Fusion technology, which has always been in the 30-year perspective, is suddenly closer.

But not too close. The ignition experiment is still energy-consuming overall because the laser burned up much more energy than it delivered to the target. And there is still much to be learned about how to use fusion energy to generate electricity. But the result was reminiscent of long-standing predictions that thermonuclear fusion would solve all the energy problems of mankind. Fusion startups have seen a surge in investor interest this year. The US government announced a record $1.4 billion in research funding, marking the start of a 10-year journey towards practical fusion. The potential benefit is great: Understand the Science, Wisdom Says, and Fusion Will Unlock “Unlimited Clean Energy”.

To a large extent this expression is true. Just look up at that burning ball in the sky. He has another 5 billion years left. Various national programs, a major international program called ITER (International Thermonuclear Experimental Reactor) and at least 40 private companies are trying to replicate this process here on Earth. The goal is to slam the atoms into each other – typically two hydrogens to form helium – and lose some mass in the process, which, following the formula e = mc2, also releases energy. Therefore, it can be argued that the energy of thermonuclear fusion is as limitless as the hydrogen atoms in the universe are.

But following the same logic, wind farms and solar panels can also appear to be inexhaustible, powered by endless streams of water pressure, wind and photons. In fact, of course, they are limited by practical considerations. Authorizations from the authorities. Financing. Designs and supply chains required for the production of turbine blades and photovoltaic film. Features complex electrical networks that require power at inopportune times or lack connections in certain areas.

That is why, as the field develops, some are now beginning to explore the likely practical and economic limits of fusion. Current findings suggest that fusion power will not be cheap, and certainly will not be the cheapest source of electricity in the coming decades, as more solar and wind energy enters power grids around the world. But fusion can still find its place because the power grid needs energy in different forms and at different times.

“I was wondering how the hell fusion could ever compete economically with the amazing advances in renewable energy.” – Jacob Schwartz, a physicist at the Princeton Plasma Physics Laboratory.

It was the question that inspired the transition from working on the details of fusion engineering to energy system economics.

In a paper published in the journal Joule, Schwartz and colleagues used a complex model of the US power grid from 2036 to 2050 to study the conditions under which it would be economical to build 100 gigawatt fusion power plants, enough to power an estimated 75 million homes. How cheap does a fusion power plant have to be to use it?

The results show that the answer can vary greatly depending on the cost and combination of other energy sources in a decarbonized electricity grid, such as renewable energy, nuclear power plants, or natural gas plants equipped with carbon capture devices. In most scenarios, fusion is likely to fill a niche very similar to that of good old nuclear fission today, albeit without the same safety and waste concerns. Both systems are essentially gigantic, using a lot of specialized equipment to extract energy from atoms so that it can heat water and power steam turbines, meaning high upfront costs. But while the energy they generate can be more expensive than from renewable sources like solar, this electricity is clean and reliable no matter the time of day or the weather.

So, can fusion compete on these terms? The purpose of the study was not to estimate the cost of a single reactor. But the good news is that Schwartz managed to find at least one design that could produce energy at a competitive price: the Aries-AT, a relatively detailed model of a fusion power plant developed by UC San Diego physicists in the early 2000s. Schwartz cautions that this is just one point of comparison, and other fusion plants may well have different cost profiles or fit into the grid differently depending on how they are used. Also, geography will matter. For example, on the US East Coast, where renewable energy resources are limited and transmission is difficult, simulations have shown that fusion can be useful at higher costs than in the West. Overall, it’s fair to imagine a future in which fusion becomes part of the “diverse energy diet” of the US power grid, he says.

In an earlier analysis in 2021, Samuel Ward, a physicist at the time at York University, and his colleagues took a more cautious view. They describe a number of scenarios that could sideline fusion, some of which could be good news for the world: for example, wind power and solar power could do most of the work of decarbonizing the power grid by the time fusion comes along. Even conventional nuclear power plants could become more efficient with the development of so-called “small modular reactors” that are designed to be cheaper to build. In addition, says Ward, who is now at the Eindhoven University of Technology in the Netherlands, fusion cost projections include materials and supply chains that in many cases do not yet exist.

“Essentially, it all comes down to a lot of uncertainty. It’s an insidious feeling, especially when people bring up the idea of ​​a “Holy Grail” or “limitless” energy. They use these words, and I don’t think it’s good for fusion.”

Fusion companies are, unsurprisingly, eager to explain why their designs will not only change the physics of fusion, but also be unique in an economic sense. The proposed reactors can be broadly divided into two categories: one, known as a tokamak, uses powerful magnets to produce plasma. The other uses an approach called inertial containment, the purpose of which is to shatter the target and energize it by hitting it with a laser, as in the NIF ignition experiment, or with high-velocity projectiles.

“This is not a question I get asked very often.says Michl Binderbauer, CEO of TAE Technologies, when asked about the organization of his company’s economy. People are more likely to ask how he plans to heat the plasma in his reactor to 1 billion degrees Celsius, compared to the 75 million the company has demonstrated so far. But the issues are interrelated, he says.

Such extreme temperatures are necessary because TAE Technologies uses boron as a fuel along with hydrogen, which Binderbauer believes will ultimately simplify the fusion reactor and make the power plant cheaper to build. He puts costs somewhere between classical fission and renewables – about where the Princeton modellers think it should be. He points out that while fusion plants would be expensive to build, the fuel would be extremely cheap. In addition, the lower risk of accidents and less high-level radioactive waste should mean a reprieve from costly regulations that have pushed up the cost of fission facilities.

Bob Mumgaard, CEO of MIT’s subsidiary Commonwealth Fusion Systems, says he was excited to see Princeton simulations because he believes their tokamak can reduce high cost requirements. It is based on a super-powerful magnet, which the company hopes will allow it to run this tokamak model, and therefore power plants, on a smaller scale, saving money. CFS is building a scaled-down prototype of its fusion design in Massachusetts that will include most of the components needed for a working plant. “You can really go and look at it and touch and look at the devices,” he says.

Nicholas Hawker, CEO of First Light Fusion, an inertial fusion company, published his own economic analysis of fusion power in 2020 and was surprised to find that the biggest costs are not from the fusion chamber and its unusual materials, but from capacitors and turbines. necessary for any power plant.

However, Hawker expects this type of power plant to grow at a slower pace than some of his peers. “The first power plants will break down all the time,” he says, and the industry will need significant government support – just like the solar industry has for the past two decades. That’s why he thinks it’s good that many governments and companies are trying different approaches: it increases the chances that some of the technologies will survive.

Schwartz agrees. “It would be strange if the universe allowed only one form of fusion energy to exist,” he says. This diversity is important because otherwise the industry risks sorting out that branch of science only to paint itself into a corner. Both nuclear fission and solar panels have previously gone through similar periods of experimentation in their technological paths. Over time, both projects converged on common structures – photovoltaic cells and massive pressurized water reactors – that were built around the world.

However, for thermonuclear fusion, first of all it is a science. This may not work in the near future. It may take another 30 years. But Ward, despite his caution about the limits of fusion in the power grid, still believes that research is already paying off, generating new advances in basic science and in the creation of new materials. “I still think it’s worth it,” he says.