• Energy Research
• natural sciences close
• Indian Institutes of Technology close

Abstract It is usual to extract hot water from a storage tank, using displacement by cold water from the mains; this causes the temperature of the outgoing hot water to decrease with time. In order to alleviate this undesirable feature a number of tanks in series may be employed. In this communication the effect of number of tanks on the outlet temperature of hot water, has been analytically investigated; it has been assumed that the only heat exchange, taking place in the tanks is on account of flow of water. The considerations in this analysis are similar to those made by Rabinovich and Fert [1] and Rabinovich [2], for a system of tanks in a solar collector loop without any outflow of water. Thus the analysis is best applicable when hot water is extracted at a fast rate, so that the gain or loss of heat by other mechanisms is negligible, compared to that due to the flow of water. The analysis should also be applicable to shallow solar ponds, Sodha et al. [3], and built in storage water heaters, Sodha et al. [4].

Abstract A simple transient analysis of the conventional mud chullah of single pot seat has been presented. The effects of various parameters, namely pressure and non-pressure pot, use of insulation in walls and basement of the chullah, heat capacity of pot-water, burning rate of wood, and heat losses from the combustion gas, have been incorporated in the analysis. Keeping in view the outcomes of this analysis, some interesting recommendations have been made to make the mud chullah more efficient.

Abstract The curves have been predicted for horizontal, as well as tilted collectors and for different gap spacings. These curves can easily be used for evaluating the effects of design changes in solar flat-plate collectors.

Abstract This paper presents a transient analysis of a one-pass double-pipe heat exchanger, coupled to a flat-plate solar collector, in both co-current and counter-current modes of flow. Explicit expressions for the temperatures of the fluid streams have been developed as a function of time and space co-ordinates under the two modes of flow.

AbstractThe development of pseudocapacitive materials for energy‐oriented applications has stimulated considerable interest in recent years due to their high energy‐storing capacity with high power outputs. Nevertheless, the utilization of nanosized active materials in batteries leads to fast redox kinetics due to the improved surface area and short diffusion pathways, which shifts their electrochemical signatures from battery‐like to the pseudocapacitive‐like behavior. As a result, it becomes challenging to distinguish “pseudocapacitive” and “battery” materials. Such misconceptions have further impacted on the final device configurations. This Review is an earnest effort to clarify the confusion between the battery and pseudocapacitive materials by providing their true meanings and correct performance metrics. A method to distinguish battery‐type and pseudocapacitive materials using the electrochemical signatures and quantitative kinetics analysis is outlined. Taking solid‐state supercapacitors (SSCs, only polymer gel electrolytes) as an example, the distinction between asymmetric and hybrid supercapacitors is discussed. The state‐of‐the‐art progress in the engineering of active materials is summarized, which will guide for the development of real‐pseudocapacitive energy storage systems.

This Paper presents a new approach for the optimal sizing and siting of substations and network routing problem. The solution approach proposed is a nolinear programming approach. The problem has been formulated as a Quadratic Mixed Integer programming (QMIP) problem in terms of the fixed costs of the substations and lines and the present worth of the energy loss costs of the line segments. The solution to this QMIP problem is obtained in two stages. In the first stage the quadratic programming problem is solved following the procedure developed by Wolfe using simplex method and treating all the variables as continuous variables. In the second stage, a procedure has been suggested to integerize the values of the integer variables. The proposed method is validated using a numerical example.

Abstract Thin film solar cells with ITO/ZnO/P3HT:PCM:CTSe NCs/Ag structure were fabricated employing a fast and cost-effective procedure using blended solution of P3HT:PCBM:CTSe NCs deposited by spin casting, followed by thermal annealing steps. The CTSe NCs are prepared via solvothermal method. An inverted architecture of device with structure ITO/ZnO/P3HT: PCBM:CTSe NCs/Ag have been fabricated with different concentration of CTSe NCs in poly(3-hexyle thiophene) (P3HT): [6,6]phenyl-C61-butyric-acid-methyl-ester (PCBM) matrix. The effect of CTSe NCs on the performance of hybrid solar cell with optimized blend ratio of P3HT:PCBM and CTSe NCs has been investigated for optimum power conversion. The charge carrier extraction and recombination at the interface of donor-acceptor material were studied using Electrochemical impedance spectroscopy (EIS) under dark condition. EIS study has demonstrated that the charge transfer rate was higher for the device having optimized wt% of CTSe NCs (10 wt%) in P3HT:PCBM active layer. A significant improvement in the device performances was observed on incorporation of CTSe NCs. The device exhibited open circuit voltage (Voc) of 0.475 V, short circuit current density (Jsc) of 6.95 mA/cm2, fill factor (FF) of 0.41 and power conversion efficiency (PCE) of 1.35%.

Abstract Low grade high ash coals with difficult physical washability characteristics require chemical cleaning techniques such as solvent extraction to obtain super clean coal with lower ash contents. Kedla, an Indian low grade coal has ash content around 44%–50% and there is a need to maximize its solvent extraction yield so as to make this power grade coal industrially useful. This paper highlights the use of definitive screening design and response surface methodology to extract the maximum organic matter from Kedla coal using ethylenediammine (EDA) and N-methyl pyrollidone (NMP) as solvents under mild atmospheric pressure conditions. The coal was pre-treated with acetic acid before extractions were carried out. The parameters such as the acid pre-treatment time, acid concentration, particle size, the co-solvent concentration and the solvent concentration were optimized in this paper. With this design of experiments technique about 40% of the organic matter with minimal ash (less than 2%) content was rendered extractable unlike the already postulated designer solvent system—e, N system (i.e. NMP containing small amount of EDA) that uses coal to solvent ratio as 1:17 (wt/vol) and coal to co-solvent ratio as 1:1(wt/vol) thus only giving 19% extraction yield. Therefore, the present design of experiments technique helps in conserving the number of experiments for process intensification.

Abstract Based on available correlations relations are found for the local maxima's and minima's in heat transfer as the gap spacing is varied in flat plate solar collectors. These relations can shorten the task of selecting an optimum gap. A criterion is proposed for evaluating the use of alternate mediums in the enclosed space. It is shown that the use of heavy gases such as Argon can result in a 34 per cent reduction in heat losses. Nusselt number correlations of a single gap are extended to a two-cover system. It is found that by using two-covers there is an overall saving of more than 50 per cent in convection losses. It is also found that heat transfer rates in the laminar and turbulent regions are relatively insensitive to the internal spacing of the covers but reduces on changing from the mid-way position in the initial regime. A new type of two cover system is proposed in which the upper space is partially evacuated and it is shown that heat losses can be reduced by 85 per cent on a one-tenth reduction of pressure. Design relations for calculating cover spacings and heat transfer coefficients in this system are derived.