TES, an energy storage technology inspired by nature

Stones that store heat, heat that generates steam, steam that expands in a machine that, in turn, generates electricity: this is an energy storage system that’s so simple it’s revolutionary – because instead of using “rare earth” minerals or raw materials that are only present in certain areas of the planet: it simply uses ordinary stones. It’s called TES (Thermal Energy Storage) and it was inaugurated on November 4 at the combined cycle power plant in Santa Barbara in Cavriglia, in Tuscany. This area has a long history of mining and using coal, but today it’s shaping up to be a real energy innovation hub. In fact, our plant is the first in the world to use this technology on a large scale, and it can also be employed as a storage system for renewables. Tuscany – long known as the “home” of geothermal energy – is already one of Italy’s most “virtuous” regions, with more than 50% of its energy self-produced from renewable sources, a fact that Region President Eugenio Giani pointed out during the inauguration ceremony.

Salvatore Bernabei, CEO of Enel Green Power, stressed the key role of energy storage systems in supporting the development of renewables, which underpin the decarbonization process and the electrification of consumption. However, renewables, at least in the case of solar and wind power, are intermittent, given that constant production cannot be ensured at night or when there is no wind. “Flexibility and adequacy are two essential components of an efficient and reliable electricity system and they can be provided in an increasingly efficient way by storage systems,” explained Bernabei. “This trial enables us to validate a family of innovative and sustainable technologies in the segment of long-term storage, enabling the increasing integration of renewables into the grid.” So TES is “a piece of the puzzle that enables us to achieve a world that is decarbonized and more sustainable,” concludes the head of EGP.

TES is a technology that is inspired by nature in its simplicity and is a result of our meeting with the Israeli company Brenmiller Energy in 2018. This achievement is the result of our Group’s tireless pursuit of innovation – thanks to our extensive network of innovation hubs and labs in various countries, including the one in Tel Aviv – and is an important step towards concrete solutions in response to the needs shared by Italy and Israel, such as that of energy, as emphasized by the new Israeli Ambassador to Italy, Alon Bar. Mr. Bar also pointed out that the project has benefited from bilateral Italian-Israeli cooperation in the field of innovation.

An innovative technology to support renewables

“This is an idea that has turned into an industrial-scale project, the first of its kind and the first of its size in the world,” explained Luca Solfaroli Camillocci, Head of Enel Green Power & Thermal Generation Italy.

The system uses a two-phase charge and discharge process. In the charge phase, the steam generated by the Santa Barbara gas-powered plant passes through pipes to heat up rocks positioned in a series of modules. In the discharge phase, the stored heat is released to heat pressurized water and generate steam to produce electricity. The system can store up to around 24 MWh of clean heat at a temperature of around 550°C for at least 5 hours, providing the plant with significant resilience.

Today this technology can be used to provide “green heat” to industrial companies, like those involved in food production or ceramics. But it can also be applied to renewable plants, storing heat that can then generate electricity during the discharge phase. “Thanks to these technologies, we can help the process of decarbonizing in those sectors where it’s not possible to decarbonize directly through electricity, namely those industrial sectors that require heat,” continued Solfaroli Camillocci.

Innovation has led to a significant drop in the cost of energy storage worldwide, with a reduction of around 80% over the past decade. It is precisely our “ability and need for innovation, and our willingness to take risks,” that was praised by Avi Brenmiller, President and CEO of Brenmiller Energy, according to whom “the result has been exceptionally good. In the future, I expect to see a huge expansion of this technology, not only at power plants but also at industrial sites.”

An exercise in freedom and energy independence

TES is just the latest success for the Enel Group’s rigorous and unwavering search for innovative partners, including startups and tech companies, which in Israel has seen the launch of 58 projects out of a total of 1,500 companies analyzed. Projects do not necessarily need to be particularly complex: TES, for example, is “a solution that was striking in its simplicity,” commented Nicola Rossi, Head of Innovation at EGP. “This system is sustainable: it doesn’t degrade over time, it doesn’t use materials that are hard to find, it’s safe because it doesn’t contain reactive materials or moving parts, and it’s competitive and cost-effective compared to other technologies in many applications.”

 TES doesn’t use rare chemical elements or those found only in certain areas of the world – it only uses stones, and it doesn’t create “geopolitical dependence,” commented Ernesto Ciorra, Enel’s Head of Innovability®. In Ciorra’s opinion, “this storage is an exercise in freedom and independence. Innovators don’t stop at the reasons why it’s impossible to do things – they work with passion and determination to find a way of doing them, to create a better world.”