Coming from a Sicilian family, I know very well the heat of Sicilian sandy beaches. A memory of my childhood is the burning feet when walking on the sand: for going from your sunbed to the shore for a bit of freshness, you had to run very quickly. At the time, I never thought that the sand could be used to store energy just like a battery...
This is what the Magaldi Group managed to do. Founded in 1929 in Italy, the Magaldi Group is the world’s leading manufacturer of steel belt conveyors to handle hot, abrasive and heavy materials in extreme conditions in coal-fired power plants, foundries, steel mills, cement plants, etc. They operate in three main business areas: Power, Industry and Renewable Energy.
Last June, the first Solar Thermo Electric Magaldi (STEM) industrial plant started its operations in San Filippo del Mela in Sicily. Developed by the Magaldi Group in cooperation with the Federico II University of Naples and some institutes of the National Research Council, this is the first innovative Concentrating Solar Power (CSP) technology that uses sand as thermal energy storage: it collects solar energy and converts it into thermal energy to be stored and extracted when needed.
The solar energy is captured through a field of heliostats, concentrated on a secondary reflector (beam down) and focused into a receiver at ground level. The receiver is fluidised sand at an operating temperature of 550-650° C and it is used to transfer and store the solar thermal energy. In this way, the thermal energy stored can be released when required.
The STEM technology can be combined with photovoltaic plants to guarantee continuity of production: during the day, the electric power can be produced by the photovoltaic plant from the sunlight; but the sunlight also feeds the STEM auxiliaries that store the solar energy in fluidised sand. The sand works effectively as a thermal energy storage and can be used during the night for steam or power generation. For this reason, this technology is particularly suitable in remote sites without grid connection to cover energy needs like desalinisation of water, air conditioning and production of industrial steam.
Compared to existing CSP technologies, STEM introduces two main innovative elements. First of all, it allows flexibility in the configuration, power and capability of the generation system that therefore can follow better the demand of power. Furthermore, it can store solar energy and deliver it when needed, like a battery.
Another important aspect is that the STEM technology is environmentally friendly. It doesn’t produce poisonous emissions (even in case of failures) and it doesn’t use cooling water or chemicals. It uses just eco-friendly materials: glass for heliostats, steel for structures and sand for thermal storage. This means that at the end of its working life, all materials can be recycled. Moreover, regarding the landscape, it has less visual impact than other CSP tower systems: the height of a STEM plant is up to 22m, while traditional CSP tower systems can exceeds 100m.
In this respect, the STEM technology could be considered a step forward towards a world where the energy is potentially produced completely in a sustainable way. In the past years, a lot of progress has been done in the area of renewable energy to reduce CO2 emissions. Many natural resources are available to us and many of these are available in huge quantities. More research about new ways of developing energy is something that policy makers could encourage to better take advantage of what is easily accessible from nature and less polluting.