What is the fusion energy gain factor?

So how much progress have we made towards using fusion to generate electricity? Here, we introduce the concept of the fusion energy gain factor, normally written as (Q). (Q) is the ratio of power generated via fusion to externally provided heating power.

(Q=1) denotes scientific breakeven. Every bit of energy we produced would need to be pushed back into the plasma to keep it hot enough for fusion to take place. At (Q=1), the reaction is not really self-sustaining as we will never be able to capture all of the energy from fusion with perfect efficiency and push it back into the plasma. This is why we call it ‘scientific’ breakeven. It is a really important step along the journey, but it does not lead to a functioning reactor for energy production.

A commercially viable fusion reactor must have (Q) much bigger than 1. We need plenty of additional energy output to allow for losses and inefficiencies so that we can both keep the plasma burning and produce large amounts of electricity to deliver to the grid.

(Q=infty) corresponds to ignition, meaning no external heating power needs to be applied to maintain fusion conditions. This occurs when the energy deposited by helium nuclei produced in the fusion reaction alone is sufficient to keep the plasma at fusion conditions. We would still need to keep the plasma confined using external fields, we just don’t need to keep topping up the energy to keep things going.

Now that you have heard more about our journey towards fusion are you optimistic that we will be able to provide commercial fusion power in the future?