The first intelligent person moved a rock away from a fire at some point in the dawn of humanity to stay warm and created the thermal battery.

More than a million years later, as humanity struggles to move away from fossil fuels to avoid climate collapse, this simple idea began to return to the conscience of contemporaries, and the hot rocks are still hotter than ever, both literally and figuratively.

Standing next to a small, building-sized thermal battery, inventor Andrew Bonik claimed that the rocks inside the battery box had heated to 1,600 degrees Celsius, or almost 3,000 degrees Fahrenheit. This temperature exceeds the point at which steel melts.

Hot rocks are an important source of energy because they are not heated by tons of coal or gas but by thousands of photovoltaic solar panels that surround the prototype west of Fresno, California.

If Bonik and his startup “Antora Energy” succeed, they will be a part of the trillion-dollar new energy storage sector, which is based on the sun or wind to heat rocks enough to power the biggest factories in the world.

Bonik is surprised by those who mock the simplicity of his project, but he confirms at the same time that the reason for the project’s success is its simplicity.

His passion for clean energy began when he decided to repair photovoltaic cells in the garage of his house. He then dropped out of Stanford University to pursue his passion for building solar power plants.

When he returned to get his degree, he realized that while the sun and wind are very useful as sources for charging batteries in cars and homes, there is a more pressing need to use clean energy in everything, from baby food to steel. Because the demand for energy in factories is often 24/7, heavy industries have not yet been able to take advantage of the decreasing prices of renewable energy sources.

Bonik says that most of the time, electricity in the wholesale market is free and sometimes even negative because there is so much solar power installed now. We are seeing the same thing in other states with wind. The problem is that you can’t shut down your factory when the sun goes down, disappears behind a cloud, or the wind stops blowing.

While the word “battery” refers to the chemical type found in cars and electronics, hot rocks can store many times more energy than lithium batteries, due to an innovation dating back to 1800. This innovation is known as “copper” hearths, which are huge towers made of stacked bricks that absorb the heat from the heating furnace until it reaches about 3000 degrees Celsius and provide 100 megawatts of power for 20 minutes.

This process can be repeated 24 times a day for 30 years. Antora is one of the start-ups that is trying different types of rocks in isolated boxes or melted salt to reach higher efficiency.

While it’s true that graphite was once the object of fascination for all, Bonik points out that carbon can carry a lot of heat and is readily available, cheap, and used to melt steel and aluminum.

According to Bonik, the primary feature of earlier ovens that was lacking was a means of releasing heat; nevertheless, as technology advanced, carbon was given holes and cavities to let light pass through and glow. Additionally, some insulated doors with adjustable glass to let light in were added. This light will be employed in the future to produce heat that penetrates the steel and cement sectors in addition to producing steam.

At first, Antora was able to secure financing totaling 80 million dollars from several investors, including Bill Gates. Rondo, another business in the Arabian Gulf that is seen as the primary rival, employs thermal bricks, which are far lighter than carbon but do not produce energy at the same density. More money was raised by Rondo than by Antora, and the company has already manufactured its first energy battery for a commercial application—a California ethanol plant.

John O’Donnell, CEO of Rondo, said in a statement quoted by CNN that the company has implemented an innovation that allows the bricks to be heated directly by infrared rays and invisible light from the heating elements. He added that independent parties have provided him with engineering reports stating that these things will last for 100 years.

In a related context, Tesla expected recently that the free-carbon world will need 240 terawatt-hours of stored energy, which is more than 340 times the amount of storage generated with lithium-ion batteries in the past year of 2022.

O’Donnell expects that more than half of this new capacity will come in the form of thermal batteries because the raw materials are easily available.

By powering their factories with the largest possible number of batteries they need, manufacturers will not have to join waiting lists for years for connecting and upgrading networks.

O’Donnell says that if you are an adventurous capitalist, the new technologies will be great and exciting, and bad if you are a banker. Bankers and infrastructure managers are the ones who like this category of technology. It is not exciting, but a good thing.

Jesse Jenkins, a professor of engineering at Princeton University, says that both companies store energy and heat. Jenkins thinks that this technology, like hydrogen, plays a flexible role. He, however, sees that this technology stores energy for the long term, so he is more optimistic about it.

Jenkins, a specialized scientific expert in energy systems, is working as a consultant for Rondo, and he says that hot rocks have a clear advantage over chemical batteries that can store energy, not heat.

Jenkins told CNN that if you can do both, you can control cost curves and scale advantages in larger industrial sectors, while some of the most active electrochemical battery companies are going through a moment of success or failure.

It is worth mentioning that both the CEOs of Antora and Rondo companies participated in the COP28 climate summit in Dubai. Although some saw that the outcomes were less committed than they should have been regarding fossil fuels, the two men returned from the summit more enthusiastic about producing new ideas and innovations in the field of clean energy.