Italian energy startup Magaldi wants to use the thermal properties of the sand to give effect to the turbine. Anyone who ever went on a hot beach knows how quickly it heats up in the sun.
The Italian company Magaldi uses this property to gather sunlight in new ways. Their system is Solar Thermo Electric Magaldi (STEM) in Milazzo, Sicily, uses an array of 786 heliostats, each with an area of seven square meters, which reflect sunlight onto a large mirror. It, in turn, focuses the light on the tank, filled with 270 tons of quartz sand.
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— In fact, STEM is similar to the boiler, but it works on the sand and the Sun, explained research engineer at Magaldi Gennaro Somma.
On earth, sunlight warms only the top layers of sand. However, inside the tank STEM is compressed air blown through the group of nozzles that constantly shifts the sand. This makes it easier to heat it to high temperatures and to improve the ability to transfer heat.
When the sand reaches temperatures of up to 650 degrees, it passes heat to water flowing through pipes, turning it into hot steam, a temperature of about 500 degrees, which puts pressure on the turbine for energy production. Each module STEM has an output of 2 megawatts. Ordinary small power plant will consist of 10 modules, which together will be able to produce 21.5 MW. Module Milazzo, which was introduced in June 2016, is the first of its kind — Magaldi plans to build 29 more units by October 2017.
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The main advantage of sand is that it can retain heat longer and to maintain a stable energy production. But there is a downside – such a solar thermal power plant occupies a large area.
Milazzo is located on 22,500 square metres, equivalent to three football fields. That's why Somma says that such technology is the best option for deserts such as Chile and Australia. published