Ram Chandra

Solar drying systems and their testing procedures: A review

Abstract Solar drying systems of different designs have been reviewed. All components of solar drying systems have been considered. The testing procedures for solar dryers have also been reviewed. An attempt has been made to present the material in a self-consistent manner.

Optimization of solar air heaters of different designs

The optimum flow channel depth and mass flow rate in 10 different designs of solar air heaters have been obtained. The design variations considered are flat absorber type with and without cover glazings; single, double and triple pass etc. It is found that there exists an optimum mass flow rate corresponding to an optimum flow channel depth, for each design considered. The thermal efficiency of each design is then obtained under the optimum conditions. It is found that a single glazing solar air heater operating under double flow configuration gives the best performance.

Optimal mix of renewable energy resources to meet the electrical energy demand in villages of Madhya Pradesh

Abstract Electrification of villages from the main grid leads to large investments and losses, and this forms the basis of decentralized electricity generation. The objective of the present paper is to evolve different strategies in which the electrical energy demand of various villages of Madhya Pradesh (India) is met at minimum cost by utilizing renewable energy resources, thereby making them self-sustainable in their electrical energy needs. The renewable energy technologies considered are biomass based power generation, biogas based power generation and solar photovoltaics. The villages are categorized into five categories on the basis of the resource technology combination capable of meeting their demand at the lowest cost. The demand of villages of category (1) is met by biogas based technology only. The per unit electricity cost (PUEC) of these villages lies between Rs. 4.1 and Rs. 5.7/kW h. For villages of category (2), where demand is met by a combination of biogas and biomass technologies, the PUEC lies in the range Rs. 4.1 to Rs. 5.8/kW h. The PUEC of villages of category (3), where demand is met by biomass based technology only, lies in the range Rs. 4.7 to Rs. 8.2/kW h. The PUEC of villages where demand is met by a combination of biogas, biomass based power generation and PV technology, varies between Rs. 4.7 and Rs. 18.0/kW h (category 4). Category (5) includes those villages that do not have an appreciable amount of biomass or dung, and hence their demand is solely met by PV systems. The PUEC of these villages varies between Rs. 16.1 and Rs. 21.3/kW h. It is found that villages that have good biogas potential correspond to the lowest PUEC. This is sufficient indication for having energy policies in countries, like India, based on bioenergy (biogas and biomass).

Substitution of energy efficient devices for cooking and lighting in rural areas of Madhya Pradesh

Rural areas in many developing countries, including India, have always been ignored in improving the efficiencies of existing lighting and cooking systems, as well as in developing alternatives. This paper presents the economic performance of new and more efficient systems over the existing ones by using Life Cycle Cost (LCC) and Internal Rate of Return (IRR) methods. The analyses have been performed for 10 surveyed blocks of the State of Madhya Pradesh. The results show impressive returns if the recommended energy efficient systems are installed in the state. The results can form policy guidelines for the implementing agencies/Government organizations for rural energy programmes.

Techno-economic analysis of typical dryers.

Abstract Techno-economic analysis of typical dryers with different kinds of energy sources has been carried out. It is found that the plastic collectors of life 5–10 yr are the cheapest among all the energy systems. The conventional collectors of lifetime equal to or more than 20 yr are, however, economical when compared with other fuel systems.

Testing procedures for solar air heaters: A review

There are numerous designs of solar air heaters available in the literature [N. K. Bansal, R. Chandra and M. A. S. Malik, Solar air heaters. In Reviews of Renewable Resources of Energy (Edited by M. S. Sodha, S. S. Mathur and M. A. S. Malik). Wiley Eastern, New Delhi (1984) (Ref. [1]); M. S. Sodha, N. K. Bansal, A. Kumar, P. K. Bansal and M. A. S. Malik, Solar Crop Drying. CRC Press, Cleveland, Ohio (1987) (Ref. [2]). Therefore, there is a need for a repeatable test method independent of outdoor environmental conditions and test location. Various experimental techniques have been described so as to allow the net thermal output of an irradiated solar air heater array to be reproduced indoors. The effect of air leaks has been incorporated into the performance equations. The other well known testing procedures have also been described. A method for generating design data for solar air heaters is described.

Performance comparison of two-pass modified reverse flat-plate collector with conventional flat-plate collectors

Abstract The performance of a modified reverse flat-plate collector with air as working fluid is studied. The results are compared with the corresponding results of a reverse flat-plate collector originally proposed as well as with normal flat-plate collectors operating under single and two pass modes. It is found that much higher fluid temperature can be obtained with the new reverse flat-plate collector.

A study on the performance of a two-absorber reverse flat-plate collector

Abstract The reverse flat-plate collector is a non-concentrating collector. It can collect solar heat at high temperatures which cannot be achieved by conventional non-concentrating collectors. In this paper, the authors have proposed a number of modified versions of the originally proposed reverse flat-plate collector. The new designs are of single, as well as double, absorber type. The thermal performance of these modified reverse flat-plate collectors is compared with that of a single absorber reverse flat-plate collector, as well as with the corresponding normal flat-plate collector. It is found that the new design having two absorbers gives the best thermal performance as compared with other configurations. The analytical models presented in this paper very well describe the experimental results.

Parametric studies on the corrugated solar air heaters with and without cover

A detailed theoretical parametric analysis of a corrugated solar air heater with and without cover has been presented. The optimum flow channel depth, at which the maximum heat is available at the lowest collector cost, has been obtained. The effect of collector parameters and operating conditions is also seen on the collector performance.

Experimental investigations on single-absorber solar air heaters

Abstract Flat, corrugated and vee-corrugated solar air heaters having a single absorber are designed, fabricated and tested. The rear plate in these collectors is replaced by rigid synthetic foam. It is found that the vee-corrugated absorbers give the best performance. The efficiency of the commercially corrugated absorber is about 5% lower than that of the vee-corrugated absorber. Correlations for predicting forced convection heat transfer coefficients for these solar air heaters have been obtained. The analytical model for these air heaters has also been developed.