The energy of the future takes inspiration from the technologies of the past

With the global race towards electrification in full flow, amid data centres, electric cars, heat pumps and smart grids, the solution to one of the thorniest issues in the energy transition could be found in natural elements and materials that humans have been using for millennia: sand, bricks and gravity.
It's a paradox in appearance only, as the challenge is not just to produce more renewable energy, but to store it for when the sun isn’t shining and the wind isn’t blowing, so that it can be used when it’s needed most. According to the International Energy Agency (IEA), storage is one of the preconditions paving the way for a decarbonised electricity system: without flexible, long-term storage capacity, the mass integration of renewables is neither technically not economically sustainable.
At present, lithium-ion batteries are the most widespread type, although they have certain limits: degradation over time, finite cycles, difficulties with recycling, and dependence on critical raw materials concentrated in a few parts of the world. These drawbacks mean that something more resilient will be required for an electricity system designed to last for decades, even centuries. So, even as technology races towards the hyper-digital, this particular search is going back to basics.

Sand that stores up heat
In Finland, the startup Polar Night Energy has developed a “sand battery”. The company fills an enormous silo with common sand which has been heated to as much as over 500 °C using excess electricity. The heat is then stored for weeks or months and released when needed, for example for district heating in cities.
The principle couldn’t be simpler: surplus electrical energy is transformed into heat through resistors, and then stored by the sand thanks to its high thermal capacity and chemical stability. The system subsequently releases the heat upon request. No elements like lithium or cobalt are needed, there is no significant chemical degradation, and storage is made possible thanks simply to a common material available practically everywhere.
So what makes it different from electrochemical batteries? With sand, it's not electricity that’s being stored, but heat. However, with a significant share of Europe's energy consumption going towards heating, far-reaching thermal storage can become a pillar of energy security. A brick or a grain of sand can be heated and cooled for decades without losing capacity. It calls for a different way of thinking: not the planned obsolescence of an electronic device, but the almost-geological durability of the material.

Bricks becoming batteries
Just like sand, bricks — the defining icon of classic construction — are experiencing a second lease of life in the world of energy. In fact, high-temperature thermal storage systems use ceramic or refractory bricks heated up to 1,000 °C using excess renewable electricity. The heat can be reconverted into steam for industrial processes, or back into electricity through thermodynamic cycles. The strength of this system is the longevity of the ceramic materials: as they do not undergo the electrochemical reactions which degrade traditional batteries, they can continue to be used for tens of thousands of cycles. From the point of view of the circular economy, bricks, with their recyclability and lack of critical metals, are a direct response to a systemic question: how to build electrical infrastructure designed not for seasons or market cycles, but for generations.

Gravity as a form of storage
Even simpler again is the technology behind “gravity batteries”. Companies like Energy Vault and Gravitricity are developing systems that store energy by lifting masses (concrete blocks or steel weights) which will later generate electricity when they are lowered.
Dedicated towers are used in some cases, while others repurpose abandoned coal mines, transforming old industrial assets into infrastructure for the transition. The principle is the same as that behind pumped hydroelectric systems, but without the need for reservoirs of water: the force of gravity is harnessed as a mechanical battery.
These systems have the potential to last for decades, with limited maintenance and zero rare materials. They also provide an example of how the energy transition can go hand-in-hand with territorial regeneration.

From Seville oranges to energy waste
An experiment launched in Seville involves making use of the bitter oranges that fall from the city’s trees, which have traditionally posed a problem for disposal: they are transformed into biogas to fuel purification plants and generate electricity. The project is promoted by the local municipal company in collaboration with the university of Seville, combining the circular economy and the production of energy. While it is not currently turning out large volumes in terms of gigawatt-hours, it represents a shift in the paradigm, showing how the electricity system of the future will be more and more integrated with urban, agricultural and industrial flows.

A question for the whole system, not just a single technology
These solutions will not completely replace lithium; rather, they will be used alongside it in a complex technological tapestry. While electrochemical storage remains essential for rapid regulation and electrical mobility, thermal and mechanical solutions offer structural advantages in terms of costs, security and durability when it comes to long-term storage.
According to the scenarios considered by the International Energy Agency, global storage capacity must grow many times over by 2030 in order to support the climate targets. This goal makes technological diversification inevitable. The real challenge, then, will be to integrate these innovations in an increasingly complex, interconnected and digital electricity grid. It will only be possible to achieve the decarbonisation targets by 2030 and by 2050 by developing and strengthening electricity transmission and transport infrastructure, increasing the production of renewable energy, and ensuring that storage systems are adequately widespread: three key factors in supporting the energy transition.