Microstructural design of hard coatings

Thermal energy storage (TES) is a technology that stocks thermal energy by heating or cooling a storage medium so that the stored energy can be used at a later time for heating and cooling applications and power generation TES systems are used particularly in buildings and in industrial processes This paper is focused on TES technologies that provide a way of valorizing solar heat and reducing the energy demand of buildings The principles of several energy storage methods and calculation of storage capacities are described Sensible heat storage technologies, including water tank, underground, and packed-bed storage methods, are briefly reviewed Additionally, latent-heat storage systems associated with phase-change materials for use in solar heating/cooling of buildings, solar water heating, heat-pump systems, and concentrating solar power plants as well as thermo-chemical storage are discussed Finally, cool thermal energy storage is also briefly reviewed and outstanding information on the performance and costs of TES systems are included

A Comprehensive Review of Thermal Energy Storage

The building sector is the dominant energy consumer with a total 30% share of the overall energy consumption and accounts for one-third of the greenhouse gas emissions around the world. Moreover, in recent years the energy demands for buildings have increased very rapidly due to increase in the growth rate of population and improvement in living standards of people. Furthermore, fossil fuels will continue to dominate the world's primary energy by 2030. Thus, the increase in energy demand, shortage of fossil fuels and environmental concerns has provided impetus to the development of sustainable building and renewable energy resources. Thermal energy storage is an efficient method for applying to building envelopes to improve the energy efficiency of buildings. This, in turn, reduces the environmental impact related to energy usage. The combination of construction materials and PCM is an efficient way to increase the thermal energy storage capacity of construction elements. Therefore, an extensive review on the incorporation of PCM into construction materials and elements by direct incorporation, immersion, encapsulation, shape-stabilization and form-stable composite PCMs is presented. For the first time, the differentiation between shape-stabilized and form-stable composite PCM has been made. Moreover, various construction materials such as diatomite, expanded perlite and graphite, etc. which are used as supports for form-stable composite PCM along with their worldwide availability are extensively discussed. One of the main aims of this review paper is to focus on the test methods which are used to determine the chemical compatibility, thermal properties, thermal stability and thermal conductivity of the PCM. Hence, the details related to calibration, sample preparation, test cell and analysis of test results are comprehensively covered. Finally, because of the renewed interest in integration of PCM in wallboards and concrete, an up-to-date review with focus on PCM enhanced wallboard and concrete for building applications is added.

Phase change materials integrated in building walls: A state of the art review

Thermal modeling down to great depth, e.g. down to the Mohorovicic discontinuity, requires representative values of thermal conductivity and thermal capacity at an appropriate depth. Often there is a lack of data, especially concerning temperature and pressure dependence of thermal conductivity and thermal capacity, due to missing or questionable data from boreholes. Studies of the temperature and pressure dependence of thermal conductivity and thermal capacity showed that temperature is dominating. Thus measurements on a set of magmatic, metamorphic and sedimentary rocks sampled from different depth levels of the Eastern Alpine crust were used to obtain an estimate of the temperature dependence of both properties––at least for the area of investigation––and to give a review of the temperature dependence of thermal conductivity ( λ ), thermal capacity ( ρ × c p ) and thermal diffusivity ( κ ) for different types of rock. The temperature dependence of thermal conductivity for crystalline (magmatitic and metamorphic) rocks is different to that of sedimentary rocks. Using the approach that the thermal resistivity (1/ λ ) is a linear function of temperature whose slope increases with λ (0), the conductivity at a temperature of 0 °C, two general equations were determined. The equation for crystalline rocks was verified in the temperature range of 0–500 °C and the equation for sedimentary rocks was tested in the temperature range from 0 to 300 °C. A general equation for the temperature dependence of λ for Eastern Alpine rocks can thus be formulated: λ(T)= λ(0) 0.99+T(a−b/λ(0)) with empirical constants and corresponding uncertainties a =0.0030±0.0015 and b =0.0042±0.0006 for crystalline rocks. The constants for corresponding sedimentary rocks are a =0.0034±0.0006 and b =0.0039±0.0014. λ is given in W m −1  K −1 , T in °C. At ambient conditions thermal diffusivity ( κ ) and thermal conductivity ( λ ) for Eastern Alpine crystalline rocks show the relationship: κ=0.45×λ.

Influence of temperature on thermal conductivity, thermal capacity and thermal diffusivity for different types of rock

The prerequisite for widespread use of hydrogen as an energy carrier is the development of new materials that can safely store it at high gravimetric and volumetric densities. Metal borohydrides M(BH4)n (n is the valence of metal M), in particular, have high hydrogen density, and are therefore regarded as one such potential hydrogen storage material. For fuel cell vehicles, the goal for on-board storage systems is to achieve reversible store at high density but moderate temperature and hydrogen pressure. To this end, a large amount of effort has been devoted to improvements in their thermodynamic and kinetic aspects. This review provides an overview of recent research activity on various M(BH4)n, with a focus on the fundamental dehydrogenation and rehydrogenation properties and on providing guidance for material design in terms of tailoring thermodynamics and promoting kinetics for hydrogen storage.

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Recent Progress in Metal Borohydrides for Hydrogen Storage

1 Introduction.- 2 Types of Differential Scanning Calorimeters and Modes of Operation.- 3 Theoretical Fundamentals of Differential Scanning Calorimeters.- 4 Calibration of Differential Scanning Calorimeters.- 5 DSC Curves and Further Evaluation.- 6 Applications of Differential Scanning Calorimetry.- 7 Evaluation of the Performance of a Differential Scanning Calorimeter.- Appendix 1.- Appendix 2.- References.

Differential scanning calorimetry

The authors provide the newcomer and the experienced practitioner with a comprehensive insight into important DSC methods, including a presentation of the theoretical basis of DSC calorimeters. Emphasis is placed upon instrumentation, underlying measurement principles, metrologically correct calibrations, factors influencing the measurement process and the exact interpretation of the results. The information provided in this text should enable the reader to apply DSC methods successfully and to measure correctly thermodynamic values.

Differential Scanning Calorimetry: An Introduction for Practitioners

The output signal from a DSC, the heat flow rate as a function of temperature, and any derived quantity, such as the heat of transformation or reaction or any change of the heat capacity of the sample, may be used to solve many different problems The work required to evaluate the measured curve may differ greatly from one case to another This will become clear from the following text Sometimes the required information can be obtained from only a qualitative evaluation of the DSC curve But most of the examples described in this section demand precise measurements and critical, very often special, evaluation procedures of the measured curve In every case the basis of reliable results is a careful calibration of the DSC (see Chapter 4) As a rule the separately measured zeroline (see Sect 51) has to be subtracted from the measured curve before evaluation In every case, the relationship between uncertainties in the measurements and the quantities to be determined must always be borne in mind

Applications of Differential Scanning Calorimetry

In all DSCs, a temperature difference ...T — given as a voltage — is the original measurement signal. In almost all instruments a heat flow rate Φ m (differential heat flow rate) is internally assigned to ...T (cf. Chapt. 2). Independent of whether the user obtains ...T or Φ m from the respective DSC, knowledge of the functional relation between the measured signal (...T, Φ m) and the quantity searched for (the real heat flow rate Φ r consumed/produced by the sample) is important for 


the time-related assignment of Φ r to ...T or Φ m (investigation into the kinetics of a reaction),


the determination of partial heats of reaction,


the evaluation and assessment of the influences of operating parameters and properties of the measuring system with regard to this relation,


the estimate of the overall uncertainty of measurement.

Theoretical Fundamentals of Differential Scanning Calorimeters

A Scanning Calorimeter measures heat flow rates in dependence of temperature or time. Modern DSCs are nowadays always connected with a data acquisition system and a powerful computer (PC). This allows one to present the measured data online on a monitor in form of a curve. Normally the heat flow rate versus the program temperature (or time) is plotted, but it is also possible to calculate other quantities from the originally measured values and draw the respective graphs on the screen as well. Modern computer techniques make it possible to do even complicated evaluations of the just measured values in the background while the measurement runs.

H.-J. Flammersheim

Papers

Differential scanning calorimetry

Differential Scanning Calorimetry: An Introduction for Practitioners

Applications of Differential Scanning Calorimetry

Theoretical Fundamentals of Differential Scanning Calorimeters

DSC Curves and Further Evaluations