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Molten Salt Loop 2.0: key element for the new solar thermal energy plants.

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Cleaner and cheaper concentrated solar power plants

EU-funded researchers have developed molten salt loop technology for concentrated solar power (CSP) plants to make them more cost efficient and environmentally friendly.

Energy

Flora, soil, groundwater, surface water and air quality can be affected by leaks or emissions of synthetic oil used as heat transfer fluid (HTF) in current CSP plants. Furthermore, such plants are often designed to use water for cooling at the back-end of the thermal cycle. These water requirements can result in difficulties in arid areas, like the Middle East and north Africa. The EU-funded MSLOOP 2.0 project addressed these challenges, developing a cost-effective solar field for CSP parabolic trough power plants using optimised ternary molten salts as HTF with an innovative hybridisation system (HYSOL). “The aim is a new commercial solar thermal plant solution, with a reduction in the energy cost, where stable and dispatchable electricity will be generated through a disruptive and more sustainable hybrid plant concept,” says the project coordinator.

Prototype Developed

Researchers first designed and developed the ternary molten salts’ additives and a real-time measuring system to determine the composition of the three combined salts during the operation and the heat collector elements needed for the optimal operation of the plant. “We investigated the collector structural analysis, the operation modes of the prototype, the solar field auxiliary systems needed to provide reliability to the operation and the water consumption reduction,” the project coordinator explains. Following the manufacture of the prototype, project partners established the individual parameters according to the new operation modes, and the results of simulations and operation models were updated and validated. Accredited bodies issued certification for the heat collector element and the tests carried out in the prototype. Once validated, the technology was scaled up from the prototype to the commercial scale, and four case studies were selected according to market analysis and the possibilities offered by the molten salt loop. “This involved a 12 MW plant in Sicily (Italy), the same location including HYSOL, and an 80 MW plant in Northern Cape (South Africa) with and without HYSOL,” notes the project coordinator.

A cheaper, greener alternative

These designs allowed the dimensioning and evaluation of capital expenditures and operating expenses, which combined with energy production, levelised the cost of energy and stability of energy supply and enabled the consortium to compare MSLOOP 2,0 with alternative technologies. Other important aspects of the technology analysed during this test phase included life-cycle analysis of the molten salts and comparison with alternative HTFs, identification of the critical equipment, material degradation, required maintenance, and health and safety issues. The project’s main results include technical developments such as molten salts additives, monitoring systems, solar field auxiliary systems, operation, production, financial models and heat collector elements optimised to perform under the parameters of MSLOOP 2.0 According to the project coordinator: “These ensure reliability to achieve a technological readiness level that is sufficient for deployment at the commercial stage.” The systems developed, the experience gained during the commissioning and the tests performed on the prototype are all proof for investors and developers of the viability of the new technologies. “MSLOOP 2.0 will thus offer a new solution in future CSP tenders by providing a cost-competitive technology with a high level of flexibility in the energy supply and with no environmental drawbacks,” the project coordinator points out.

Keywords

MSLOOP 2.0, CSP, solar field, HYSOL, energy supply, concentrated solar power, molten salt loop, heat transfer fluid, parabolic trough power plant, hybridisation system

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