Viktoria Martin

Liquid–solid phase equilibrium study of tetradecane and hexadecane binary mixtures as phase change materials (PCMs) for comfort cooling storage

Phase diagrams (equilibrium diagrams) are a convenient way of depicting the concentration-temperature-pressure relationships of a chemical system at equilibrium. They are invaluable to PCMs thermal storage researches and developers. In the present paper, the liquid-solid phase equilibrium of binary mixture system of tetradedcane and hexadecane has been studied. For theoretical evaluation of the thermodynamic equilibrium between the liquid phase and solid phase of tetradecane and hexadecane, several methods were compared: the UNIFAC group-contribution method, the model of Won, and Pedersens model. The temperature-composition phase diagram of the binary system has been obtained by the calculation. The diagram illustrates a binary, isomorphous system with a temperature minimum. Differential scanning calorimetry (DSC) was used to study the phase transformation of the binary system. DSC was run at different ramp rates and results indicate that these mixtures melt and freeze over a temperature range and the temperature range depends on the DSC ramp rate, and in a short mixture concentration interval appears low temperature solid-solid peaks. From the DSC results presented, it is concluded that the behaviour of binary mixtures of n-alkanes is far more complicated than considered in earlier studies. The phase diagram and all information from DSC are very important for designing PCM storage system.

Compact Heat Storage for Solar Heating Systems

Energy and cost efficient solar hot water systems require some sort of integrated storage, with high energy density and high power capacity for charging and discharging being desirable properties of the storage. This paper presents the results and conclusions from the design, and experimental performance evaluation of high capacity thermal energy storage using so-called phase change materials (PCMs) as the storage media. A 140 l 15 kW h storage prototype was designed, built, and experimentally evaluated. The storage tank was directly filled with the PCM having its phase change temperature at 58 degrees C. A tube heat exchanger for charging and discharging with water was submerged in the PCM. Results from the experimental evaluation showed that hot water can be provided with a temperature of 40 degrees C for more than 2 h at an average power of 3 kW. The experimental results also show that it is possible to charge the 140 l storage with close to the theoretically calculated value of 15 kW h. Hence, this is a PCM storage solution with a storage capacity of over 100 kW h/m(3), and an average power capacity during discharging of over 20 kW/m(3). However, it is desirable to increase the heat transfer rate within the prototype. A predesign of using a finned-tube coil instead of an unfinned coil show that by using finned tube, the power capacity for discharging can be at least doubled, if not tripled.

Analysis of heat-driven cooling production coupled to power generation for increased electrical yield

In striving for sustainable energy systems, the development of advanced technologies for combined heat and power generation is a critical factor. In many regions of the world there is a demand for ...

Industrial surplus heat storage in smart cities

Surplus heat generated from industrial sectors amounts to between 20% and 50% of the total industrial energy input. Smart reuse of surplus heat resulted from industrial sectors and power generation ...

Wind Resource Assessment in Europe Using Emergy

In context of increasing use of renewable sources, it is of importance to correctly evaluate the actual sustainability of their implementation. Emergy analysis is one of the possible methods useful for such an assessment. This work aims to demonstrate how the emergy approach can be used to assess the sustainability of wind energy resource in Europe. The Emergy Index of Sustainability (EIS) and the Emergy Yield Ratio (EYR) are used to analyze 90 stations of European regions for three types of wind turbines. To do so, the simplified Chou wind turbine model is used for different set of parameters as: nominal power and size of the wind turbines, and cut-in and cut-out wind speeds. Based on the calculation of the emergy indices, a mapping is proposed to identify the most appropriate locations for an implementation of wind turbines in European regions. The influence of the wind turbine type on the sustainability is also analyzed, in link with the local wind resource. Thus, it is concluded that the emergy sustainability indices are sensitive to the wind turbine design parameters (size, cut-in and cut-out wind speed).

Energy Analysis and Thermoeconomic Assessment of the Closed Greenhouse: The Largest Commercial Solar Building

The closed greenhouse concept has been studied in this paper. The closed greenhouse can be considered as the largest commercial solar building. In principle, it is designed to maximize the utilization of solar energy through seasonal storage. In an ideal fully closed greenhouse, there is not any ventilation window. Therefore, the excess heat must be removed by other means. In order to utilize the excess heat at a later time, long and/or short term thermal storage technology (TES) should be integrated. A developed model has been evaluated due to different situations. The closed greenhouse is compared with conventional greenhouse using a case study respect to the energy analysis. A parameter has been defined in this paper in order to compare performance of the closed greenhouse concept in different conditions. This parameter has been called ESR. Finally a preliminary thermo-economical study has been assessed in order to investigate on feasibility of the closed greenhouse concept.Copyright

Wafer level stress data successfully used as early burn-in predictor

We show that a simple post-stress test can provide a good early reliability indicator. The defect types that have been revealed by this post-stress test are two types of conductive particles on metal levels. This early indicator has been of great value when dealing with potentially contaminated wafers/lots and to evaluate and to prioritize the corrective actions to solve the line issues.