Journal ArticleDOI
Latent heat storage above 120°C for applications in the industrial process heat sector and solar power generation
Rainer Tamme,Thomas Bauer,Jochen Buschle,Doerte Laing,Hans Müller-Steinhagen,Wolf-Dieter Steinmann +5 more
TLDR
In this paper, phase change materials (PCMs) are used for thermal storage in the temperature range of 120-300 °C for solar thermal power generation and high temperature process heat.Abstract:
This paper is focussed on thermal storage technologies using phase change materials (PCMs) in the temperature range of 120-300 °C for solar thermal power generation and high temperature process heat. As state-of-the-art reference system a steam accumulator is described, which typically has a volume-specific thermal energy density of 20-30 kWh/m³. Regarding efficiency, a fundamental demand on thermal storage is the minimization of temperature differences between working fluid and storage medium. This requires isothermal storage systems for processes using water/steam. An obvious solution is, therefore, the application of PCMs.
The selection of the PCMs depends strongly on the operation conditions of the respective application. At present, the main emphasis is directed to alkali metal nitrates and nitrites and their mixtures. For example, the eutectic mixture of the binary system KNO3-NaNO3 has been identified as an excellent system to be used for processes using saturated steam at around 25 bar. At around 5 bar the ternary system KNO3-NaNO2-NaNO3, commonly used as heat transfer fluid, can also be used as a PCM. To overcome the low thermal conductivity of the salt systems, approaches of increased surfaces area and increased thermal conductivity using expanded graphite (EG) have been investigated. Using EG/PCM-composites the effective thermal conductivity can be increased from below 0.5 W/(mK) to 3-20 W/(mK).
Three design concepts have been developed. In the macro-encapsulated design, the PCM is enclosed in metal tubes, giving a short distance for heat transfer and increasing the heat transfer area. In the second design, the heat exchanger tubes are embedded in EG/PCM-composite storage material. The third design option uses graphite foils arranged perpendicularly onto the heat exchanger tubes and a suitable salt system filled in between. The upgrade of existing steam accumulators using these PCM concepts is also proposed.read more
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Book ChapterDOI
Heat Exchange Analysis on Latent Heat Thermal Energy Storage Systems Using Molten Salts and Nanoparticles as Phase Change Materials
Adio Miliozzi,Raffaele Liberatore,Daniele Nicolini,ManilaChieruzzi,Elisabetta Veca,Tommaso Crescenzi,Luigi Torre +6 more
TL;DR: In this paper, three methods are proposed to improve the heat exchange between heat transfer fluid and PCM, experimentally analyzed: conductivity system enhancements; convective flows promotion in liquid phase; and improvement of PCM thermal properties including small amounts of nanoparticles.
Journal ArticleDOI
Molecular patterns in the thermophysical properties of pyridinium ionic liquids as phase change materials for energy storage in the intermittent temperature range
TL;DR: In this paper , a family of pyridinium ionic liquids and their thermophysical properties were investigated for phase change materials, and the most promising results in terms of PCM application, and one of the best among all pyridine structural isomers reported thus far, were obtained for 2-hydroxypyrinium methanesulfonate [2-OHpyH][CH 3 SO 3 ] (T m = 433 K and Δ H f = 190 J g −1 ).
Journal ArticleDOI
Impact of Geometry on a Thermal-Energy Storage Finned Tube during the Discharging Process
TL;DR: In this article , the authors focused on the modeling of latent heat thermal energy storage systems and compared three different latent heat TES configurations during the discharging process to evaluate the most efficient in terms of maximum average discharging power.
Chapter 5: Thermal energy storage materials and systems
TL;DR: In this paper, a broad overview of thermal energy storage (TES) materials and technologies is given, with a focus on high temperature applications in the area of concentrated solar power (CSP) generation.
References
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ReportDOI
Physical properties data compilations relevant to energy storage. ii: molten salts: data on single and multi-component salt systems
TL;DR: In this article, the authors provided selected data with value judgements for an additional set of 107 salt systems of interest as candidate materials for thermal energy storage sub-systems, for electrochemical energy storage systems, and in electrochemical aluminum production.
Journal ArticleDOI
Buffer storage for direct steam generation
Wolf-Dieter Steinmann,Markus Eck +1 more
TL;DR: In this article, the authors use steam accumulators for compensation of fast transients in insolation for solarthermal systems using steam as working medium and integrate latent heat storage material to increase the storage capacity.