The future of energy storage

As the use of renewables increases, there is an ever greater need for energy storage systems that can ensure durability and flexibility to the grid. That’s why EGP is trialing new solutions, working on innovation with an open approach.

Energy storage systems are a key feature of the energy transition. “Our goal,” explains Giuseppe Cicerani, Enel Green Power’s Head of BD Generation Integrated Storage, “is to become a decarbonized company, generating energy solely from renewable sources. But renewables, and in particular solar and wind power, depend on natural resources, so they can’t ensure constant production at night or when there isn’t any wind. They also tend to be intermittent because they’re subject to the variability of these resources, so they’re not entirely predictable.”

Ensuring the stability of the electricity system

In order to function effectively, the electricity system must be able to ensure the balance between energy production and consumption at all times, as well as to deal with unexpected events in terms of supply and demand. This requires flexible resources capable of modulating production based on actual energy needs. As renewables progressively replace thermoelectric power stations, we need new solutions that meet flexibility and adequacy requirements. This is exactly what energy storage systems can do, because they’re able to store the surplus energy produced and return it to the system when needed. When combined with renewable energy plants, they can provide a source of energy that is not only clean, but also flexible and reliable.

This is what will soon be happening in Sardinia as the island abandons coal once and for all. At the Capacity Market auction for 2024, held by Terna (the company that operates the electricity transmission grids in Italy), Enel Green Power was awarded approximately 1.1 GW of contracted capacity, which it will honor by installing around 1.6GW/6.6GWh of new capacity in energy storage systems by 2024. Half the capacity will be installed in Sardinia, without recourse to new gas plants and therefore taking a significant step forwards towards the transformation of Sardinia into a green island. In total, Enel Green Power has more than 52GW of BESS projects in development worldwide and more than 2.7GW under construction or in operation.

The role of lithium ion batteries

Currently, in the countries where Enel Green Power operates, wind and solar plants supply energy to the grid predominantly during the day, while at night thermoelectric plants take over. The most commonly used energy storage systems, as Cicerani explains, are lithium batteries that have a very rapid response capacity but offer a relatively limited energy contribution lasting only a few hours. This type of battery is used mainly to provide flexibility services to the grid and to ensure an adequate supply of energy at the most critical times, but they do not store large volumes of energy due to the high unit cost of batteries compared to the value of the energy stored.

In future, with the growing share of surplus energy produced from renewable generation and the decommissioning of thermoelectric power plants, it will be necessary to store large volumes of energy. Whether lithium ion batteries remain the technology of choice will depend on how much the cost per volume of energy stored falls from today’s levels. According to Cicerani, however, it’s very likely that in the near future the market’s energy requirements will lead to larger energy storage systems and, in particular, an increase in storage duration.

This scenario will see the use of new batteries using chemicals other than lithium, as well as non-electrochemical solutions, for example gravitational energy storage systems or those based on compressed gas.

New emerging technologies

These technologies, which in many cases are in the pre-commercial phase of development, already offer the possibility to develop large-scale (multi-MW) demonstration plants to assess performance and reliability. This is precisely the model Enel has adopted: supporting the scale-up and validation of innovative technologies in industrial contexts and real business scenarios. In collaboration with startups and innovative firms, industrial-scale demonstration plants are currently being built based on flow batteries with chemical elements like vanadium and iron, on chemicals based on zinc or evolutions of lithium ion batteries with solid-state electrolyte solutions. Ornella Grassia, Innovation Product Owner at Enel Green Power, explains, “We have four projects under construction on the Spanish islands (the Canaries and Balearics) because there’s a need for longer lasting energy storage systems to facilitate the growing penetration of wind and solar power. We’ve seized the opportunity to develop projects with innovative solutions that will give us an immediate competitive advantage, thanks to the expertise we’ve acquired in terms of solutions that may turn out to be essential in supporting renewables in the very near future.”

For the non-electrochemical solutions, collaborations have been launched with startups that are developing thermal storage plants, like the system that EGP is building with the Israeli startup Brenmiller to boost operational flexibility at the combined cycle plant in Santa Barbara, Italy. There is also the gravitational storage plant developed with Energy Vault in Texas, where the electricity markets are particularly favorable to energy storage systems.

Energy storage and the circular economy

When it comes to innovation and storage, it is essential to identify sustainable solutions and approaches and to adopt circular economy models for the end-of-life management of our assets. “In recent months, a demonstration project has been launched to promote the circularity of the battery production chain that will see the creation in Spain of a plant to recycle the batteries and recover their precious metals,” explains Irene Fastelli, Head of Enel Green Power’s Innovation Factory. Sustainability and circularity are two fundamental levers for the competitiveness of the energy storage production chain and can create business opportunities for local industries.

Within this context, potential synergies between electric mobility and large-scale stationary energy storage are being explored. One such example is the “second life” battery storage facility at the power plant in Melilla, a Spanish enclave on the coast of Morocco, where used Nissan Leaf electric vehicle batteries, which are no longer suitable for powering EVs but still have residual capacity, are deployed to stabilize the local electricity grid. These solutions are still experimental but could make an important contribution to the stability of the electricity system, especially as electric vehicles increasingly penetrate the market.

By trialing these solutions extensively, Enel is at the cutting edge of technological innovation as the first to commercially exploit these technologies and thereby enable the electricity system to function using 100% renewable energy.