One of the challenges of communicating science is getting the right balance between enthusiasm and realism. Science can be truly exciting, but it’s easy to overhype something. Too often lazy journalists oversell a science news item, exaggerating prior ignorance and the significance of the new finding. Every discovery is a “breakthrough” and every advance is a “game-changer.”

For technology advances there is a tendency to overestimate short term progress, and the applicability of the new gadget or technique, while glossing over obstacles and downsides. It takes work to find what is truly interesting about a news item, while putting it into proper context.

That is why I am struggling a bit with this current news item, because this technology, if we ever pull it off, would be a true game-changer. It is hard to overestimate the impact that it would have. I am talking about fusion energy. This is not to be confused with cold fusion, which is probably a fantasy, but actual hot fusion, the kind that powers the sun.

MIT researchers announced in an article for Nature that they believe they are 15 years away from a commercial fusion power plant. If true, this is huge news.

A fusion power plant would make energy by forcing together hydrogen atoms (in some form) with so much energy that they fuse together to form helium. The fusion would release a tremendous amount of energy. This is also what happens in a hydrogen fusion bomb. While making a hydrogen bomb is complicated enough, it is relatively easy compared to fusion energy. You only need one uncontrolled moment of high energy to cause the fusion, which then literally explodes.

Fusion energy requires a slow controlled burn. The challenge has been achieving the  temperatures and pressures necessary to cause fusion. The two basic techniques used are magnetic confinement and inertial confinement. The latter uses lasers to quickly force the hydrogen together.

Magnetic confinement is what the MIT team is using. The device is called a Tokamak reactor, which uses a modified torus design to keep a plasma of hydrogen moving around within the magnetic field, never touching the outer walls. A plasma is basically atoms heated to such a degree that they are stripped of their electrons, so a plasma of hydrogen would them be protons, which are positively charged and can be confined by a magnetic field.

Actually researchers are also looking into which isotope of hydrogen is the best, and it seems it may be a certain ratio of deuterium and tritium (1 proton with 1 or 2 neutrons respectively).

In any case, the technological challenge has been getting a magnetic field powerful enough to produce the temperatures and pressure necessary to cause fusion. Further, the entire process has to produce more energy than it consume. Producing the powerful magnetic fields uses a lot of energy, and so the device has to be not just powerful enough, but efficient enough that the energy produced will exceed the massive amount of energy needed to make it run.

The real news is that MIT has attracted $50 million in investment to produce its new design for a tokamak reactor. The breakthrough is the use of new superconducting material that allows for smaller and more efficient magnets. These magnets are more powerful and use less energy, which the MIT team claims will get them past the point of producing more energy than consumed.

All of this sounds perfectly reasonable, and we have been building to this point for decades. There is no theoretical reason why this won’t work. It has always been about the power and efficiency of the magnets, and so any advance there should have a huge impact. There are, of course, lots of other technical details, like the exact fuel, and the shape of the torus – but the magnets are the main factor.

As I said, you can’t really oversell the implications of having a commercially viable fusion power plant that produces usable energy. The fuel is simply hydrogen, which is plentiful. It takes energy to strip the hydrogen from water or another source, but this is small compared to the energy produced by fusion. The waste product is helium, which is actually a useful substance. There is no nuclear waste, and no released carbon or other greenhouse gas. These features would make fusion reactors vastly superior to any other form of mass energy.

This would also be the technological fix to global warming everyone has been hoping for. But there are still two details we need to consider – how long will it take, and how cost effective will it be? These are the things we cannot really know for sure until it happens.

Regarding cost-effectiveness, current estimates (which admittedly include a lot of assumptions) indicate that fusion can be commercially viable. The energy will cost a little more than current fission reactors, but will still be competitive in the market. If we take into consideration the externalized costs of global warming and the health effects from pollution, then fusion becomes even more competitive.

Regarding fission, we have to consider the cost of long-term storage of nuclear waste. Also, we need to consider the implications of producing fissionable waste as a byproduct that can be ultimately converted into weapons-grade material.

Likely the upfront costs of fusion energy will be high, but the long term investment will be worth it.

Perhaps the most difficult variable to predict is how long it will take to have a commercial fusion power plant. The MIT estimate of 15 years is definitely optimistic, and experts disagree on how realistic it is. Fifteen years is long enough in terms of developing technology that essentially it translate into – we have no idea.

Usually such projections assume that everything goes well, all hurdles are overcome, no new hurdles or problems are encountered, and the stars align perfectly. If you double such estimates you are probably closer to the mark.

Still, if we can have working fusion plants in 20-30 years that would be great. But – this probably won’t be soon enough to prevent serious consequences from global warming. We can’t ignore the problem and just wait for our fusion reactors. It will also take time to build fusion plants – it will probably take decades to replace a significant number of coal and gas power plants.

It is perhaps reasonable to guess that by the end of this century we will have a significant fusion energy infrastructure. But we will be way past our carbon budget by then. We will need renewable energy and fission power in the meantime as a bridge to our fusion future.