Hybridization of CSP Plants: Characterization of a Molten Salt Heater for Binary and Ternary Nitrate Salt Mixtures Fueled with Gas/Biogas Heaters

Hybridization of CSP plants with alternative energy sources (fuels) represents a means to improve flexibility of operation, power dispatchability and utilization factor of the plant. New generation CSP plants make use of molten salts as Heat Transfer Fluid (HTF) besides Thermal Energy Storage (TES)...

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Autores principales:	Alberto Giaconia, Irena Balog, Giampaolo Caputo
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	concentrating solar power (CSP) heat transfer fluids molten salt binary and ternary nitrate mixtures hybridization of CSP plants molten salt heater Technology T
Acceso en línea:	https://doaj.org/article/15c8e885f57241d8a32e397d1ceaa607
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spelling	oai:doaj.org-article:15c8e885f57241d8a32e397d1ceaa6072021-11-25T17:27:33ZHybridization of CSP Plants: Characterization of a Molten Salt Heater for Binary and Ternary Nitrate Salt Mixtures Fueled with Gas/Biogas Heaters10.3390/en142276521996-1073https://doaj.org/article/15c8e885f57241d8a32e397d1ceaa6072021-11-01T00:00:00Zhttps://www.mdpi.com/1996-1073/14/22/7652https://doaj.org/toc/1996-1073Hybridization of CSP plants with alternative energy sources (fuels) represents a means to improve flexibility of operation, power dispatchability and utilization factor of the plant. New generation CSP plants make use of molten salts as Heat Transfer Fluid (HTF) besides Thermal Energy Storage (TES) medium. Therefore, proper interfaces should be developed to effectively transfer the heat from the back-up source to the molten salt. This paper presents the results obtained in the experimental validation of an innovative gas-fueled Molten Salt Heater (MSH) prototype. The objective of this research is to validate the MSH design, where the specific properties of molten salts (compared to other HTFs, e.g., thermal oils) have to be taken into account. The developed reduced-scale MSH (90 kW thermal) consists of a heat exchanger with the molten salt flowing inside finned tubes cross-flowed with the hot flue gas generated in an upstream combustion chamber. LPG or a biogas-like mixture has been used as gas fuel. Experimental results have been obtained with two different molten salt mixtures: the “solar salt” binary mixture (NaNO<sub>3</sub>/KNO<sub>3</sub>, 60/40%w) typically used in CSP applications (up to 565 °C) and the ternary mixture known as Hitec XL<sup>®</sup> containing sodium/potassium/calcium nitrates (NaNO<sub>3</sub>/KNO<sub>3</sub>/Ca(NO<sub>3</sub>)<sub>2</sub>, 15/43/42%w) characterized by lower freezing temperatures. Experimental tests have been carried out changing some operative parameters like the flow rate of the molten salt (0.45–0.94 kg/s), the inlet temperatures of the molten salt (303–445 °C) and of the hot gas (596–632 °C). For both molten salt mixtures, it was demonstrated that heat transfer correlations based on the Dittus-Boelter equation allow to predict experimental results with <10% deviation between experimental and theoretical values of the heat transfer coefficient.Alberto GiaconiaIrena BalogGiampaolo CaputoMDPI AGarticleconcentrating solar power (CSP)heat transfer fluidsmolten saltbinary and ternary nitrate mixtureshybridization of CSP plantsmolten salt heaterTechnologyTENEnergies, Vol 14, Iss 7652, p 7652 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	concentrating solar power (CSP) heat transfer fluids molten salt binary and ternary nitrate mixtures hybridization of CSP plants molten salt heater Technology T
spellingShingle	concentrating solar power (CSP) heat transfer fluids molten salt binary and ternary nitrate mixtures hybridization of CSP plants molten salt heater Technology T Alberto Giaconia Irena Balog Giampaolo Caputo Hybridization of CSP Plants: Characterization of a Molten Salt Heater for Binary and Ternary Nitrate Salt Mixtures Fueled with Gas/Biogas Heaters
description	Hybridization of CSP plants with alternative energy sources (fuels) represents a means to improve flexibility of operation, power dispatchability and utilization factor of the plant. New generation CSP plants make use of molten salts as Heat Transfer Fluid (HTF) besides Thermal Energy Storage (TES) medium. Therefore, proper interfaces should be developed to effectively transfer the heat from the back-up source to the molten salt. This paper presents the results obtained in the experimental validation of an innovative gas-fueled Molten Salt Heater (MSH) prototype. The objective of this research is to validate the MSH design, where the specific properties of molten salts (compared to other HTFs, e.g., thermal oils) have to be taken into account. The developed reduced-scale MSH (90 kW thermal) consists of a heat exchanger with the molten salt flowing inside finned tubes cross-flowed with the hot flue gas generated in an upstream combustion chamber. LPG or a biogas-like mixture has been used as gas fuel. Experimental results have been obtained with two different molten salt mixtures: the “solar salt” binary mixture (NaNO<sub>3</sub>/KNO<sub>3</sub>, 60/40%w) typically used in CSP applications (up to 565 °C) and the ternary mixture known as Hitec XL<sup>®</sup> containing sodium/potassium/calcium nitrates (NaNO<sub>3</sub>/KNO<sub>3</sub>/Ca(NO<sub>3</sub>)<sub>2</sub>, 15/43/42%w) characterized by lower freezing temperatures. Experimental tests have been carried out changing some operative parameters like the flow rate of the molten salt (0.45–0.94 kg/s), the inlet temperatures of the molten salt (303–445 °C) and of the hot gas (596–632 °C). For both molten salt mixtures, it was demonstrated that heat transfer correlations based on the Dittus-Boelter equation allow to predict experimental results with <10% deviation between experimental and theoretical values of the heat transfer coefficient.
format	article
author	Alberto Giaconia Irena Balog Giampaolo Caputo
author_facet	Alberto Giaconia Irena Balog Giampaolo Caputo
author_sort	Alberto Giaconia
title	Hybridization of CSP Plants: Characterization of a Molten Salt Heater for Binary and Ternary Nitrate Salt Mixtures Fueled with Gas/Biogas Heaters
title_short	Hybridization of CSP Plants: Characterization of a Molten Salt Heater for Binary and Ternary Nitrate Salt Mixtures Fueled with Gas/Biogas Heaters
title_full	Hybridization of CSP Plants: Characterization of a Molten Salt Heater for Binary and Ternary Nitrate Salt Mixtures Fueled with Gas/Biogas Heaters
title_fullStr	Hybridization of CSP Plants: Characterization of a Molten Salt Heater for Binary and Ternary Nitrate Salt Mixtures Fueled with Gas/Biogas Heaters
title_full_unstemmed	Hybridization of CSP Plants: Characterization of a Molten Salt Heater for Binary and Ternary Nitrate Salt Mixtures Fueled with Gas/Biogas Heaters
title_sort	hybridization of csp plants: characterization of a molten salt heater for binary and ternary nitrate salt mixtures fueled with gas/biogas heaters
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/15c8e885f57241d8a32e397d1ceaa607
work_keys_str_mv	AT albertogiaconia hybridizationofcspplantscharacterizationofamoltensaltheaterforbinaryandternarynitratesaltmixturesfueledwithgasbiogasheaters AT irenabalog hybridizationofcspplantscharacterizationofamoltensaltheaterforbinaryandternarynitratesaltmixturesfueledwithgasbiogasheaters AT giampaolocaputo hybridizationofcspplantscharacterizationofamoltensaltheaterforbinaryandternarynitratesaltmixturesfueledwithgasbiogasheaters
_version_	1718412332522012672

Hybridization of CSP Plants: Characterization of a Molten Salt Heater for Binary and Ternary Nitrate Salt Mixtures Fueled with Gas/Biogas Heaters

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