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Author

Harald Mehling

Bio: Harald Mehling is an academic researcher. The author has contributed to research in topics: Thermal energy storage & Phase-change material. The author has an hindex of 24, co-authored 38 publications receiving 6955 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, a review of the history of thermal energy storage with solid-liquid phase change has been carried out and three aspects have been the focus of this review: materials, heat transfer and applications.

4,019 citations

Book
10 Oct 2008
TL;DR: In this article, the basic thermodynamics of thermal energy storage and solid-liquid phase change materials have been studied in the context of latent heat storages and their integration into systems.
Abstract: Basic thermodynamics of thermal energy storage.- Solid-liquid phase change materials.- Determination of physical and technical properties.- Heat transfer basics.- Design of latent heat storages.- Integration of active storages into systems.- Applications in transport and storage containers.- Applications for the human body.- Applications for heating and cooling in buildings.

746 citations

Journal ArticleDOI
TL;DR: In this paper, phase change materials (PCM) are used in free cooling systems to store outdoors coolness during the night, to supply indoors cooling during the day, and an installation that allows testing the performance of PCMs in such systems was designed and constructed.
Abstract: In this paper, the application of phase change materials (PCM) in free-cooling systems is studied. Free-cooling is understood as a means to store outdoors coolness during the night, to supply indoors cooling during the day. The use of PCMs is suitable because of the small temperature difference between day indoors and night outdoors. An installation that allows testing the performance of PCMs in such systems was designed and constructed. The main influence parameters like ratio of energy/volume in the encapsulates, load/unload rate of the storage, and cost of the installation were determined, and experiments were performed following the design of experiments strategy. The statistical analysis showed that the effects with significant influence in the solidification process are the thickness of the encapsulation, the inlet temperature of the air, the air flow, and the interaction thickness×temperature. For the melting process the same holds, but the inlet air temperature had a higher influence than the thickness of the encapsulation. With the empirical model developed in this work, a real free-cooling system was designed and economically evaluated.

324 citations

Journal ArticleDOI
TL;DR: In this article, three methods to enhance the heat transfer in a cold storage working with water/ice as PCM are compared: addition of stainless steel pieces, copper pieces and a new PCM-graphite composite material.

262 citations

Journal ArticleDOI
TL;DR: In this article, the enthalpy change of phase change materials (PCMs) is measured with high precision using differential scanning calorimetry (DSC) and T-history method.
Abstract: Phase change materials (PCMs) are thermal storage materials with a high storage density for small temperature range applications. In the design of latent heat storage systems, the enthalpy change of the PCM has to be known as a function of temperature with high precision. During dynamic measurements, the sample is not in thermal equilibrium, and therefore the measured value is not the equilibrium value. The influence of non-equilibrium on the measurement results can be quantified by doing measurements during heating and cooling with any measurement instrument. Measurements carried out by differential scanning calorimetry (DSC) and by the T-history method are presented and discussed. To characterize encapsulated PCM objects, measurements on the whole objects should be carried out. A measurement setup for this purpose is also presented. The obtained precision meets typical application requirements, and good agreement between results obtained with the different methods is demonstrated.

260 citations


Cited by
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Journal ArticleDOI
24 Jun 2011-Science
TL;DR: This work synthesized a porous carbon with a Brunauer-Emmett-Teller surface area, a high electrical conductivity, and a low oxygen and hydrogen content that has high values of gravimetric capacitance and energy density with organic and ionic liquid electrolytes.
Abstract: Supercapacitors, also called ultracapacitors or electrochemical capacitors, store electrical charge on high-surface-area conducting materials. Their widespread use is limited by their low energy storage density and relatively high effective series resistance. Using chemical activation of exfoliated graphite oxide, we synthesized a porous carbon with a Brunauer-Emmett-Teller surface area of up to 3100 square meters per gram, a high electrical conductivity, and a low oxygen and hydrogen content. This sp 2 -bonded carbon has a continuous three-dimensional network of highly curved, atom-thick walls that form primarily 0.6- to 5-nanometer-width pores. Two-electrode supercapacitor cells constructed with this carbon yielded high values of gravimetric capacitance and energy density with organic and ionic liquid electrolytes. The processes used to make this carbon are readily scalable to industrial levels.

5,486 citations

Journal ArticleDOI
TL;DR: In this paper, a review of the history of thermal energy storage with solid-liquid phase change has been carried out and three aspects have been the focus of this review: materials, heat transfer and applications.

4,019 citations

Journal ArticleDOI
TL;DR: In this paper, a review of the phase change materials (PCM) and their application in energy storage is presented, where the main advantages of encapsulation are providing large heat transfer area, reduction of the PCMs reactivity towards the outside environment and controlling the changes in volume of the storage materials as phase change occurs.

2,636 citations

Journal ArticleDOI
TL;DR: In this paper, the phase change problem has been formulated using pure conduction approach but the problem has moved to a different level of complexity with added convection in the melt being accounted for, which makes it difficult for comparison to be made to assess the suitability of PCMs to particular applications.
Abstract: This paper reviews the development of latent heat thermal energy storage systems studied detailing various phase change materials (PCMs) investigated over the last three decades, the heat transfer and enhancement techniques employed in PCMs to effectively charge and discharge latent heat energy and the formulation of the phase change problem. It also examines the geometry and configurations of PCM containers and a series of numerical and experimental tests undertaken to assess the effects of parameters such as the inlet temperature and the mass flow rate of the heat transfer fluid (HTF). It is concluded that most of the phase change problems have been carried out at temperature ranges between 0 °C and 60 °C suitable for domestic heating applications. In terms of problem formulation, the common approach has been the use of enthalpy formulation. Heat transfer in the phase change problem was previously formulated using pure conduction approach but the problem has moved to a different level of complexity with added convection in the melt being accounted for. There is no standard method (such as British Standards or EU standards) developed to test for PCMs, making it difficult for comparison to be made to assess the suitability of PCMs to particular applications. A unified platform such as British Standards, EU standards needs to be developed to ensure same or similar procedure and analysis (performance curves) to allow comparison and knowledge gained from one test to be applied to another.

1,630 citations

Journal ArticleDOI
TL;DR: In this article, the authors summarized previous works on latent thermal energy storage in building applications, covering PCMs, the impregnation methods, current building applications and their thermal performance analyses, as well as numerical simulation of buildings with PCMs.

1,569 citations