Browsing by Keyword "Thermal energy storage (TES)"
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Item Corrosion testing device for in-situ corrosion characterization in operational molten salts storage tanks: A516 Gr70 carbon steel performance under molten salts exposure: A516 Gr70 carbon steel performance under molten salts exposure(2016-12-01) Ruiz-Cabañas, F. Javier; Prieto, Cristina; Osuna, Rafael; Madina, Virginia; Fernández, A. Inés; Cabeza, Luisa F.; MATERIALES PARA CONDICIONES EXTREMASConcentrated solar power (CSP) generation is becoming a very important player within the renewable energy sector thanks to increased introduction of these facilities into the conventional electricity market. CSP plants become dispatchable when integrating thermal energy storage (TES) systems which allow electricity production at any time of the year. Sensible TES using nitrate salts mixtures as storage fluid are the most extended arrangement for commercial CSP facilities. In addition to storage time, dimensions, thermal-mechanical requirements, among others, corrosion compatibility between high temperature nitrate salts, and structural materials is a key factor to take into consideration for the final storage system design. Many scientific contributions have been developed regarding metallic alloys corrosion performance in nitrate salts at laboratory scale. Accordingly, lack of technical background is identified about nitrates corrosion in relevant operation conditions. Therefore, a corrosion testing device (CTD) was designed to evaluate corrosion behavior of structural materials inside high temperature nitrate salts storage tanks in operation. Furthermore, A516 Gr70 carbon steel was evaluated at different exposures times by using the CTD in the TES-PS10 pilot plant. Results reported within this study show the feasibility of the CTD to be used at commercial scale allowing corrosion preventive maintenance practices and materials selection optimization. Moreover, A516 Gr70 carbon steel displayed an excellent corrosion performance after nitrate salts exposure being recommended for long time service under continuous and intermittent exposure to nitrate salts. In addition to low corrosion rates, carbon steel generated protective and well adhered iron oxide layers without significant localized phenomena. Finally, negligible susceptibility to crevice and stress corrosion cracking (SCC) phenomena is showed by carbon steel under test conditions.Item Materials selection for thermal energy storage systems in parabolic trough collector solar facilities using high chloride content nitrate salts(2017-04-01) Ruiz-Cabañas, F. Javier; Prieto, Cristina; Madina, Virginia; Fernández, A. Inés; Cabeza, Luisa F.; MATERIALES PARA CONDICIONES EXTREMASThe increasing role of concentrated solar power (CSP) within the renewable energy portfolio is attributed to the possibility of integrating thermal energy storage (TES) systems. Then, CSP technology has become one of the most interesting clean options to deliver dispatchable power on demand. Nowadays, commercial facilities use high quality solar salts (60%:40% NaNO3 and KNO3 by weight) as storage medium due to the attractive properties of this fluid to be applied under CSP operation conditions. Taking into account that CSP installations are designed with really large TES systems containing tens of thousands of tons, the use of lower quality nitrates salts would reduce the molten salts inventory cost and finally the investment cost of the CSP storage systems at commercial scale. The most important drawback of selecting low quality nitrates salts for high temperature CSP applications is the corrosion impact produced by impurities. Accordingly, chlorides have been identified in the state of the art as the impurity with higher effect over corrosion. This work is focused on A516 Gr70 carbon steel corrosion performance evaluation under high-chlorides content nitrates salts (1.2% and 3% by weight) at 400 °C. In addition, the feasibility of using the proposed low purity mixtures with current CSP facilities materials selection is analyzed. Results reported within this study show the critical effect of chloride content over corrosion mechanism producing lack of adherence between base metal and oxides layers in addition to corrosion products delamination and internal cracking. Then, the use of A516 Gr70 carbon steel is rejected for a long term design under solar salts containing chlorides content in the range 1.2–3% by weight being necessary a higher corrosion resistant materials selection. An improved materials selection focused on higher corrosion resistance alloys is discussed.Item Materials selection of steam-phase change material (PCM) heat exchanger for thermal energy storage systems in direct steam generation facilities(2017-01-01) Ruiz-Cabañas, F. Javier; Jové, Aleix; Prieto, Cristina; Madina, Virginia; Fernández, A. Inés; Cabeza, Luisa F.; MATERIALES PARA CONDICIONES EXTREMASPhase change materials (PCM) is one of the most interesting solutions to be used in thermal energy storage (TES) systems for direct steam generation (DSG) thermosolar facilities. Properties such as high energy density and energy storing/delivery at constant temperature bring PCM based systems in excellent candidates for DSG facility storage units. Accordingly, LiOH-KOH peritectic mixture, with a melting point of 315 °C and an enthalpy change of 535 kJ/kg, has been reported as attractive solution for the saturated storage module in DSG plants. A steam-PCM heat exchanger is the critical component to carry out the thermal transference between both substances. Although materials selection to be applied for steam applications is well known, lack of knowledge is detected in the field of high temperature hydroxides corrosion. Therefore, three metallic materials, A516 Gr70 carbon steel, A316L stainless steel and Inconel 625 Ni-base alloy, have been evaluated to determine their corrosion performance after hydroxides exposure. While A516 Gr70 was discarded for this application due to high corrosion rates, A316L and Inconel 625 displayed good corrosion resistance after 2640 h. Finally, A316L stainless steel was selected as potential candidate for the construction of the steam-PCM heat exchanger considering cost and thermal efficiency optimization.