Researchers propose ‘economic Q’ metric for judging fusion power plant viability

Researchers in the United States have introduced a novel metric to assess the economic viability of forthcoming fusion power plants. This metric is akin to the Q factor employed by fusion researchers to measure the output of fusion reactions, which are the same reactions powering stars. Fusion, a process occurring in stars, entails two light nuclei merging to create a heavier nucleus, thereby releasing substantial energy.

Harnessing fusion on Earth, utilizing hydrogen isotopes deuterium and tritium, could potentially yield an environmentally benign and virtually inexhaustible energy source. In the 1950s, John Lawson, an engineer and physicist, devised what is now known as the "Lawson criterion" for fusion. This criterion outlines the ideal temperature, plasma density, and energy confinement time necessary to generate net energy from a fusion plasma, irrespective of its absolute power or volume.

It calculates a factor termed "plasma Q," representing the ratio of fusion power generated to the external power needed to maintain the plasma. A plasma Q equal to 1 signifies a break-even point, while higher values indicate excess energy output. In terms of magnetic confinement, where magnetic fields are utilized to contain a hot plasma, the Joint European Torus, situated in Oxfordshire, UK, achieved a plasma Q of 0.67 during its experiments in 1997.

The International Thermonuclear Experimental Reactor (ITER), presently under construction in Cadarache, France, is targeted for a Q of 10 upon full operational capability in the late 2030s. Fusion industry advancements have surged in recent years, with the Fusion Industry Association revealing in a recent report that private fusion companies amassed nearly $4.5 billion in funding over the past year—a 70% increase from the previous year.

The report suggests that 71% of the 65 surveyed companies anticipate the first fusion plant to generate commercial electricity by the 2030s. However, skepticism persists regarding fusion's imminent viability as a power source. In response, researchers are proposing a framework for determining what is essential to render fusion energy commercially viable in the market.

Although the costs associated with fundamental experiments are relatively straightforward to quantify, estimating the expenses of a fusion reactor presents a more formidable challenge. Andrew Lo, an economist from the Massachusetts Institute of Technology (MIT) and co-author of the new study, acknowledges the difficulty in translating complex scientific and engineering requirements into economic consequences.

"If we don't accomplish this, we won't secure the funding necessary to achieve the impact we aspire to," Lo remarks. The proposed framework consists of ten parameters aimed at gauging the economic viability of a fusion energy power plant. While some of these parameters are rooted in scientific and physical aspects, relating to the energy consumed and produced within a specific plant, others are centered on engineering and economic factors, encompassing plant construction costs, returns on invested capital, the efficiency of converting fusion power into an economic product, and the longevity of components employed in the energy conversion process.

The "economic Q" is determined as the ratio of capital gained to capital expended. MIT nuclear engineer Dennis Whyte, a co-author of the study, emphasizes that achieving a net-positive economic return necessitates an economic Q greater than 1. Whyte, recently appointed CEO of the United Kingdom Atomic Energy Authority, also highlights that the framework parameters are contingent upon the reactor's size and can be scaled to any project or power output.

"A quantitative evaluation framework offers a literal assessment of the economic value associated with making specific design decisions," Whyte asserts. "At this pivotal juncture in fusion development, the absence of such a framework has been glaring, and we have been bereft of this critical tool."