{"id":1631,"date":"2025-09-05T11:42:25","date_gmt":"2025-09-05T09:42:25","guid":{"rendered":"https:\/\/fersisolar.com\/?p=1631"},"modified":"2026-09-17T11:50:16","modified_gmt":"2026-09-17T09:50:16","slug":"solar-heat-for-the-minerals-industry","status":"publish","type":"post","link":"https:\/\/fersisolar.com\/en\/solar-heat-for-the-minerals-industry\/","title":{"rendered":"Solar heat for the minerals industry"},"content":{"rendered":"

The production of gypsum requires a constant heat supply<\/strong> to ensure product quality and process efficiency. Concentrated solar thermal energy<\/strong> with thermal energy storage<\/strong> offers an alternative to gas for industrial processes<\/strong> in the minerals sector. With this technology, it is possible to generate hot air<\/strong> and reach temperatures of up to 400\u00b0C, achieving 78 percent thermal coverage<\/strong> or more at the plant.<\/p>\n

In addition to providing renewable heat for the minerals industry<\/strong>, a concentrated solar system can help avoid energy volatility in industry<\/strong>, as it provides predictable costs with solar energy<\/strong> and a low levelized cost of heat (LCOH<\/strong>). This makes competitive solar heat for factories<\/strong> a viable option for reducing emissions<\/strong> of greenhouse gases and pollutants and improving the sustainability of production.<\/p>\n

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Figure 1: Example of a rotary kiln<\/em><\/p>\n

And how do we decarbonize gypsum production in practice? First, we have to dry gypsum rock, a sedimentary rock composed of calcium sulfate and water. In this specific case, we need hot air at 300\u00b0C and a rotary kiln (Figure 1) to obtain different materials used in construction.<\/p>\n

Heat generation<\/h2>\n

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Figure 2: System schematic<\/em><\/p>\n

As always, we start with heat generation (Figure 2), and for this we use parabolic trough collectors (PTCs). We have already discussed how they work in a previous article (here<\/a><\/span><\/span>), so we will not go over the basics again. Unlike the previous cases described, in this project we need to supply heat at temperatures above 250\u00b0C, the practical limit of pressurized water as a working fluid. To reach this temperature, we use thermal oil designed to operate at up to 425\u00b0C. This silicone-based product has a higher boiling point than water\u2014380\u00b0C at atmospheric pressure. We still need to keep the system under pressure for safety reasons, but at pressures below the 40 bar used in the water system.<\/p>\n

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Figure 3: Parabolic trough collectors<\/em><\/p>\n

Since this project operates at very high temperatures, it is essential to insulate the collector properly to prevent energy losses. The solar collector receiver is a tube onto which the solar rays are focused. As the working fluid passes through this tube, its temperature rises. If the tube is in contact with the atmosphere, some of the concentrated heat escapes through convection; the loss is proportional to the difference between the temperature of the tube and the ambient air.<\/p>\n

In projects where the tube and fluid reach temperatures of 150\u2013170\u00b0C, the tube can be insulated by placing it inside another transparent tube filled with a noble gas such as argon. However, at temperatures above 200\u00b0C, argon cannot provide sufficient insulation, and vacuum insulation technology is required. In Figure 4, the metal tube containing the working fluid is shown in purple; this tube is housed inside another glass tube, with an insulating vacuum between them. This type of receiver is more expensive and less reliable than receivers without insulation, but its use is essential to prevent prohibitive heat losses.<\/p>\n

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Figure 4: Schematic of a vacuum-insulated absorber tube<\/em><\/p>\n

Storage system<\/h2>\n

Once the heat has been generated, it must be stored until it is needed. Thanks to the concrete thermal energy storage system (TES), it is possible to ensure 24\/7 operation and process continuity, even when there is no sunlight. In this case, the thermal battery can supply all the heat required by the kiln for up to 12 hours without needing to be recharged. Due to the high temperatures of the stored heat, the TES is made of concrete. In basic terms, we have a concrete block with integrated pipes (Figure 5). During charging, the working fluid from the solar field flows through these pipes, heating the block. During discharge, the cold fluid enters through the same pipes and is heated by absorbing heat from the block.<\/p>\n

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Figure 5: The ThermalBattery from EnergyNest<\/em><\/p>\n

Unlike a water TES, concrete has lower convection losses; in addition, the system is simple, robust, and economical. However, the concrete formulation must be optimized to achieve the desired properties and maximize performance. Two parameters are key:<\/p>\n