What if we used black holes as a source of energy?

This is a question that theoretical physicists have been asking for some time, and the findings from a new study show that, theoretically, it would be possible to use black holes as galactic power banks.

Can black holes be used as actual batteries and, therefore, to generate electricity? That is the question that Zhan-Feng Mai and Run-Qiu Yang, researchers at the physics department of Tianjin University (China) addressed and attempted to answer, at least theoretically, in a paper published in the scientific journal Physical Review D, in November 2023.

The mathematical equations yield the conclusion that yes, it is theoretically possible to consider harnessing the gravitational force of a certain type of black hole to generate electricity. In practice, however, this prospect is a long way off at best. Not least because we do not yet know whether black holes of the right size for such applications actually exist, or are only a figment of physicists’ theory.

Primordial black holes

Black holes tend to be divided into three categories according to their mass: supermassive, intermediate-mass and so-called “stellar-mass”, which are formed when a star whose mass is at least 20 times that of the Sun collapses. Scientists also theorize that there is a fourth category, of so-called primordial black holes, whose existence has not yet been proved.

The theory is that primordial black holes formed in the first instants after the birth of the universe as we know it, from pockets of extremely hot and dense material. Then, as the cosmos steadily expanded and cooled, the conditions necessary for forming black holes this way ended.

If they do exist, primordial black holes are small compared to the other three types of black holes. This is precisely why they may have ‘evaporated’ over time due to a (also hypothetical) quantum process known as Hawking radiation, which would, so to speak, consume smaller black holes faster. However, larger primordial black holes may still exist somewhere in the universe, waiting to be found and perhaps used to produce energy.

Black holes as nuclear reactors

In fact, by Mai and Yang’s calculations, based on their size, primordial black holes could act, at least theoretically, as nuclear reactors from which electric energy could be obtained. Specifically, black holes the size of a single atom, with a mass ranging from 1015-1018 kilograms, could be used for this purpose. By way of comparison, Sagittarius A*, a supermassive black hole in our galaxy, weighs 4 million solar masses, or about 2×1030 kilograms.

The option proposed by the two researchers, based on the results of complex equations, would be to ‘recharge’ this kind of black holes with alpha particles, obtained from radioactive decay, which would then be transformed into positrons, the antiparticles of electrons. According to the results of the study, in a best-case scenario it would be possible to recover the equivalent of 25% of the mass of the particles used to fuel the primordial black hole in the form of energy.

Not bad at all, considering that the percentage efficiency of today’s photovoltaic panels is around the same on average. Having said that, the primordial black holes will first have to be found (assuming they exist) and then a whole raft of challenges emerges that at present seem almost insurmountable from a technical standpoint.

A few years ago, the physicist Roger Penrose discovered that energy can be stolen from rotating black holes, which have a surrounding region of space time called the ergosphere that is dragged along by their rotation. Furthermore, astrophysicists at the International Centre for Radio Astronomy Research (ICRAR) in Australia have analysed the energy emissions from a wormhole growing in the M83 galaxy and found that it releases a large amount of energy through the wind and jets it generates.

Science and research do their bit by paving the way for new questions or new approaches to a given topic. And finding a way to obtain energy from black holes is a topic that has kept theoretical physicists awake at night for some time now. The future will tell whether their theories hold water and, in the meantime, it is worth watching out on the opportunities it unlocks.

Energy consumption worldwide with a forecast until 2050, by energy source

Source: statista