Italy to Debut Industrial Sand Battery

Italian firm Magaldi Group, a specialist in ultra-high-temperature material handling, is poised to deploy its first large-scale application of a novel thermal energy storage system that uses a fluidized bed of silica sand. By the end of 2024, the system will be installed at an industrial facility owned by food company IGI in Buccino, Italy.

The Magaldi Green Thermal Energy Storage (MGTES) system is essentially a long-duration energy storage (LDES) solution that can be applied to both power-to-heat and power-to-heat-to-power applications, the company told POWER. The modular “sand battery” stores energy from renewable sources and then releases it in the form of high-temperature steam of between 120C and 400C.

Conceived and developed by Magaldi Group, MGTES uses a sand bed comprising fluidized solid silica sand particles to store energy as sensible heat at “high temperature and high energy density,” Magaldi explained (Figure 1).

Charging, Storage, and Discharge

The system operates in three distinct phases. During the charging phase, electrical heaters powered by renewable energy are used to heat the solid particle bed. Air flowing through the sand bed fluidizes the sand bed, significantly enhancing heat transfer and internal diffusivity. In the storage phase, the fluidization is stopped, allowing the sand to pack at the bottom of the module, absorbing energy and storing it for “days and even weeks,” the company said. “Energy losses are minimized due to the lack of convection and the tank’s insulation, which restricts heat exchange with the exterior of the casing,” it said.

During discharge, the integrated heat exchanger embedded within the fluidized bed of sand particles is reversed to discharge the system. “Activating the fluid bed, accumulated energy is released, by means of in-bed heat exchangers, to the heat transfer fluid—typically superheated steam (up to 600C) or other high temperature fluids required by industrial processes (such as hot air),” it said.

“Thermal losses are limited to less than 2% per day. The stored energy can be directly used in industrial processes or to feed a steam turbine for electricity generation. If used for power-to-power applications, MGTES can provide thermal energy with a “round trip efficiency of over 90%, decreasing down to 35% to 45% when the heat ratio in produced total energy is near to 0% and the generation is completely electric,” it said.

In March 2023, Magaldi signed a strategic agreement with Enel X, a customer solution focused subsidiary of Italian multinational energy company Enel Group, to supply Enel X’s industrial customers with thermal energy (in the form of steam) at desired temperatures and pressures to slash their gas consumption. The project poised to be implemented at IGI—a key supplier of confection-maker Ferrero Group—will involve building a 2.5-MW photovoltaic power plant and an 80-ton MGTES system with a daily storage capacity of 8.6 MWh.

“The plant being constructed at the IGI industrial facility in Buccino is capable of absorbing energy not only from the 2.5 MW photovoltaic plant but also from the grid,” Magaldi noted. “The ability to draw energy from the grid allows the provision of a service to the electrical grid system by selecting low-cost hours to store energy, thereby optimizing the costs of releasing and generating thermal energy (arbitrage).”

According to Magaldi, the technology is modular, and it could be flexibly customized to meet customer requirements for temperature, storage durations, and demand profile. “Energy charging, storage, and energy discharging are independently scalable,” the company said. By varying the mass of solid particles contained in each module, it is possible to configure a thermal storage capacity between 5 MWh and 100 MWh. In addition, “several modules can work in series and/or parallel, matching the required demand up to a gigawatt-hour,” it said.

The advantages of using “green heat”—thermal energy powered by renewables—in industrial processes include the electrification of high-temperature operations. It also enables recovery of industrial waste heat and supports demand response services, and could enhance the flexibility of combined heat and power plants and support carbon-neutral district heating.

MGTES Could Play a Role to Boost Power Plant Flexibility

However, Magaldi also said that the technology could play a substantial role in increasing flexibility in thermoelectric power plants. To keep up with system variability driven by renewable intermittency, coal and gas plants are facing conditions that require frequent cycling, it noted.

“This change can significantly reduce plant performances, damage components, and reduce service life,” it said. “One of the possible applications of the MGTES is its integration into the steam section of existing thermoelectric power plants. In such plants—Rankine cycle or [combined cycle gas turbine]—the MGTES can be used to reduce the minimum load and to offer a backup thermal power to be used when needed.”

When a power plant operates at its minimum load, the MGTES is designed to store a part of the thermal energy produced by the steam generator and “return the stored energy when demand increases and it is profitable to operate the plant normally,” it said. The stored heat essentially becomes “a reserve of available power to produce more steam to feed the power-block, increasing the power at which the plant works.”

—Sonal Patel is a POWER senior editor (@sonalcpatel, @POWERmagazine).