Heat transfer fluids for concentrating solar power systems – A review

Vignarooban, K.; Xu, Xinhai; Arvay, Adam; Hsu, Kuo Chin; Kannan, Arunachala Mada

doi:10.1016/j.apenergy.2015.01.125

Cited by 726 publications

(345 citation statements)

References 57 publications

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“…This binary mixture has a melting point of 220 • C [12]. When the working temperature decreases it starts to crystalize at 238 • C [5], and for this reason inside the system it must be kept in its liquid phase above 238 • C. Salt solidification is a major problem in these systems because it blocks and harms the piping system, and also obstructs the heat flux.…”

Section: Classifications Of Tes Systemsmentioning

confidence: 99%

Techno-Economic Forecasts of Lithium Nitrates for Thermal Storage Systems

et al. 2017

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Thermal energy storage systems (TES) are a key component of concentrated solar power (CSP) plants that generally use a NaNO 3 /KNO 3 mixture also known as solar salt as a thermal storage material. Improvements in TES materials are important to lower CSP costs, increase energy efficiency and competitiveness with other technologies. A novel alternative examined in this paper is the use of salt mixtures with lithium nitrate that help to reduce the salt's melting point and improve thermal capacity. This in turn allows the volume of materials required to be reduced. Based on data for commercial plants and the expected evolution of the lithium market, the technical and economic prospects for this alternative are evaluated considering recent developments of Lithium Nitrates and the uncertain future prices of lithium. Through a levelized cost of energy (LCOE) analysis it is concluded that some of the mixtures could allow a reduction in the costs of CSP plants, improving their competitiveness.

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Section: Classifications Of Tes Systemsmentioning

confidence: 99%

Techno-Economic Forecasts of Lithium Nitrates for Thermal Storage Systems

et al. 2017

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“…But the inherent danger of reactivity with water remains with NaK as well and thus restricts its use in solar CSP applications. It has been experimentally tried in an experimental solar tower in Spain and there was a huge fire reported causing lot of damage to the system [121]. Another eutectic mixture, Lead-Bismuth (44.5-55.5%) having very high boiling point of above 1500°C, owing to its inherent properties of being non-reactive with water and air, is also being applied in R and D stage in CSP application.…”

Section: Molten Metalsmentioning

confidence: 99%

Recent Developments in Heat Transfer Fluids Used for Solar Thermal Energy Applications

Srivastva¹,

Malhotra²,

Sc³

2015

J Fundam Renewable Energy Appl

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Solar thermal collectors are emerging as a prime mode of harnessing the solar radiations for generation of alternate energy. Heat transfer fluids (HTFs) are employed for transferring and utilizing the solar heat collected via solar thermal energy collectors. Solar thermal collectors are commonly categorized into low temperature collectors, medium temperature collectors and high temperature collectors. Low temperature solar collectors use phase changing refrigerants and water as heat transfer fluids. Degrading water quality in certain geographic locations and high freezing point is hampering its suitability and hence use of water-glycol mixtures as well as water-based nano fluids are gaining momentum in low temperature solar collector applications. Hydrocarbons like propane, pentane and butane are also used as refrigerants in many cases. HTFs used in medium temperature solar collectors include water, waterglycol mixtures -the emerging "green glycol" i.e., trimethylene glycol and also a whole range of naturally occurring hydrocarbon oils in various compositions such as aromatic oils, naphthenic oils and paraffinic oils in their increasing order of operating temperatures. In some cases, semi-synthetic heat transfer oils have also been reported to be used. HTFs for high temperature solar collectors are a high priority area and extensive investigations and developments are occurring globally. In this category, wide range of molecules starting from water in direct steam generation, air, synthetic hydrocarbon oils, nanofluid compositions, molten salts, molten metals, dense suspension of solid silicon carbide particles etc., are being explored and employed. Among these, synthetic hydrocarbon oils are used as a fluid of choice in majority of high temperature solar collector applications while other HTFs are being used with varying degree of experimental maturity and commercial viability -for maximizing their benefits and minimizing their disadvantages. Present paper reviews the recent developments taking place in the area of heat transfer fluids for harnessing solar thermal energy. Refrigerants/phase changing materials: These are low boiling point but high heat capacity substances used in the solar collectors to transfer heat in applications like solar space cooling and heating, refrigerators, air conditioning, etc [7]. These materials absorb heat from the solar collectors, produce work either by expanding in a turbo-generator of a vapor compression cycle or by dissociating the refrigerant from its absorbent in a vapor absorption cycle [8]. In some of the relatively high temperature applications, higher boiling point refrigerants are used as indirect heat transfer fluids, wherein the heat collected from the solar collectors is transferred to another fluid like water from where the refrigerants pick-up heat to do the required work in the turbo-generators [9,10]. Recent Developments in Heat Transfer

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“…In 2013, only 4.1 GW of solar thermal plants existed, so it is expected that total capacity will increase dramatically, almost 60 times by 2030, with an estimated annual growth rate of 29%. Most of this growth will be with Solar Power Tower (SPT) systems and the rest with Parabolic Trough Collector plants [7].…”

Section: A Preliminary Estimation Of Future Lithium Based Salt Demandmentioning

confidence: 99%

“…In fact, Chile is preparing to host a new solar thermal power plant with a capacity of 110 MW that will have an advanced storage system enabling it to operate with an 80% capacity factor and to generate electricity for up to 17.5 h without direct solar irradiance [6]. The main storage medium used in CSP plants-Chile is not an exception-is the salt composed by 60% NaNO 3 and 40% KNO 3, also known as "solar salt", which is a liquid at temperatures above its melting point of 222˝C [7]. However, significant research efforts are being undertaken in the world to develop other materials.…”

Section: Introductionmentioning

confidence: 99%

Review of Thermal Materials for CSP Plants and LCOE Evaluation for Performance Improvement using Chilean Strategic Minerals: Lithium Salts and Copper Foams

et al. 2016

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Abstract:The improvement of solar thermal technologies in emerging economies like Chile is particularly attractive because the country is endowed with one of the most consistently high solar potentials, lithium and copper reserves. In recent years, growing interests for lithium based salts and copper foams in application of thermal technologies could change the landscape of Chile transforming its lithium reserves and copper availability into competitive energy produced in the region. This study reviews the technical advantages of using lithium based salts-applied as heat storage media and heat transfer fluid-and copper foam/Phase Change Materials (PCM) alternatives-applied as heat storage media-within tower and parabolic trough Concentrated Solar Power (CSP) plants, and presents a first systematic evaluation of the costs of these alternatives based on real plant data. The methodology applied is based on material data base compilation of price and technical properties, selection of CSP plant and estimation of amount of required material, and analysis of Levelized Cost of Electricity (LCOE). Results confirm that some lithium based salts are effective in reducing the amount of required material and costs for the Thermal Energy Storage (TES) systems for both plant cases, with savings of up to 68% and 4.14% in tons of salts and LCOE, respectively. Copper foam/PCM composites significantly increase thermal conductivity, decreasing the volume of the TES system, but costs of implementation are still higher than traditional options.

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Heat transfer fluids for concentrating solar power systems – A review

Cited by 726 publications

References 57 publications

Techno-Economic Forecasts of Lithium Nitrates for Thermal Storage Systems

Techno-Economic Forecasts of Lithium Nitrates for Thermal Storage Systems

Recent Developments in Heat Transfer Fluids Used for Solar Thermal Energy Applications

Review of Thermal Materials for CSP Plants and LCOE Evaluation for Performance Improvement using Chilean Strategic Minerals: Lithium Salts and Copper Foams

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