Scheffler Concentrator Research Articles

Development of hybrid solar distillation system for essential oil extraction

Use of solar energy for cooking and steam generation is quite common around the world. However, use of solar energy for extraction of essential oils from medicinal and aromatic plants has recently been explored and its effects are still largely unknown. The current study is about essential oil extraction using a newly designed solar distillation system. The devised system consists of a primary reflector (Scheffler concentrator), steam receiver, distillation still, condenser and a florentine flask to enable extraction of essential oils from biomass. An auxiliary biomass system was also coupled with the distillation unit to complement the system during adverse weather conditions or seasonal climatic conditions throughout a typical year. The experimental results show that the concentration of essential oils from fresh Eucalyptus leaves (Camaldulensis) and Peppermint leaves (Mentha peperita L.) were 0.59% w/w and 0.40% w/w, respectively. Essential oil from Pinus (Roxburghii) was extracted using a biomass boiler yielding 0.31% w/w of essential oil. GC-MS analysis confirmed the presence of Eucalyptol (50.9%), Menthol (93.0%) and α-Pinene (70.9%) as the major compounds in Eucalyptus, Peppermint and Pinus, respectively. In summary, solar-based distillation has proven to be a cost effective way of extracting essential oils from medicinal plans and herbs.

Income generation of rural community by using solar distillation system

Processing of different herbs by distillation technique was one of the agro-based industries which lie in medium temperature range (60-280 oC). This study has been carried out for essential oils extraction using solar distillation system as well as to perform the quality analysis of eucalyptus leaves (comaldulensis) essential oils using GC MS analysis for income generation of rural community. The solar distillation system consists of a primary reflector (10 m2 Scheffler concentrator), a secondary reflector, distillation still, condenser and Florentine flasks. Results have shown that the essential oil from 10 kg fresh eucalyptus leaves (comaldulensis) for different experiments were extracted to be 29.7, 30, 28.2, 29.9 and 30.2 ml. GC MS analysis shows that eucalyptol (C10H16O) was identified as the most dominant compound of eucalyptus leaves (comaldulensis) essential oil (50.91%). This is the great opportunity of small scale farmer to on-farm solar industry for income generation of rural community. Keywords: Scheffler concentrator, Solar distillation system, Essential oil, GC-MS analysis, Income generation.

An experimental study on energy and exergy performance of a cavity receiver for solar parabolic dish concentrator

In this paper, an experimental study is carried out to investigate the thermal performance of a conical frustum cavity receiver for a 16 m2 Scheffler concentrator, using energy and exergy analyses. The experiment is conducted with heat transfer fluid having a flow rate of 2.5 litres per minute (LPM) under an average beam radiation of 608.17 W/m2. The average thermal energy efficiency of the receiver is found to be 57.39% with a peak value of 66.75%. The receiver could attain a very low overall heat loss factor of about 0.027 kW/K. The overall system efficiency of the solar collector is 69.47%. The average exergy efficiency of the receiver is found to be 5.88% with a peak value of 10.35%. A peak exergy factor of 0.152 is obtained for the receiver. Experiments are also conducted with flow rates of 1, 1.5 and 2 LPM in addition to the flow rate of 2.5 LPM and the receiver showed better performance for 2.5 LPM.

Opto–geometric performance of fixed-focus solar concentrators

In this paper, the opto–geometric performance of fixed-focus solar concentrators (FFSCs), namely, the high temperature concentrator (HTC), the Scheffler concentrator and the Scheffler-type solar concentrator (STSC), is analysed. The goal of this study is to determine the behaviours of FFSCs as a function of their dimensions and to compare the results to the results of parabolic dish (PD) solar concentrators. An algorithm based on opto–geometric models of these concentrators was developed, and numerical calculations were performed for each type in a range of thermal power of 1–50kW.The numerical results indicate that FFSCs require a reflector with a diameter 45% larger than the diameter of a PD concentrator and increase the diameter of the solar image at the receiver by 350% compared with a PD concentrator. The increase in the diameter of the solar image by the fixed receiver in the FFSC produces a lower concentration. For thermal demands of less than 10kW, FFSCs do not have significantly large dimensions. The proposed algorithm can be employed to evaluate the potential use of FFSCs and an FFSC instead of a PD concentrator because of the operational advantages of the fixed receivers of the different types.

Effect of micro-level and macro-level factors on adoption potential of solar concentrators for medium temperature thermal applications

Solar concentrators can be used for medium temperature (80–250°C) thermal applications for replacement of fossil fuels. The acceptance of any technology is driven by both the technical features and the economic benefits. Economic benefits are also governed by the performance and the investment requirement. A model is developed for estimation of market acceptance of a solar concentrator based on economics. This model is illustrated for two commercially offered solar concentrators in India, namely, fixed focus 16m2 Scheffler concentrator and moving focus 160m2 ARUN concentrator with Fresnel arrangement of reflectors. Payback periods for the two concentrators are estimated for the same operating conditions and acceptance of each is estimated. The effect of government support on acceptance is also studied. The adoption potential of Scheffler solar concentrator is 8% under present conditions which can be improved to 38% with government support while for ARUN, it can be improved from 1% to 11% with government support. The model can be used to identify the effect of government support and conventional fuel costs on the potential adoption of any solar concentrator. In the model, micro-level technology factors and macro-level market effects and trends are considered for evaluation of the adoption potential of a solar concentrator type.

Design principle and calculations of a Scheffler fixed focus concentrator for medium temperature applications

Scheffler fixed focus concentrators are successfully used for medium temperature applications in different parts of the world. These concentrators are taken as lateral sections of paraboloids and provide fixed focus away from the path of incident beam radiations throughout the year. The paper presents a complete description about the design principle and construction details of an 8 m 2 surface area Scheffler concentrator. The first part of the paper presents the mathematical calculations to design the reflector parabola curve and reflector elliptical frame with respect to equinox (solar declination = 0) by selecting a specific lateral part of a paraboloid. Crossbar equations and their ellipses, arc lengths and their radii are also calculated to form the required lateral section of the paraboloid. Thereafter, the seasonal parabola equations are calculated for two extreme positions of summer and winter in the northern hemisphere (standing reflectors). The slopes of the parabola equations for equinox (solar declination = 0), summer (solar declination = +23.5) and winter (solar declination = −23.5) for the Scheffler reflector (8 m 2 surface area) are calculated to be 0.17, 0.28, and 0.13 respectively. The y-intercepts of the parabola equations for equinox, summer and winter are calculated as 0, 0.54, and −0.53 respectively. By comparing with the equinox parabola curve, the summer parabola is found to be smaller in size and uses the top part of the parabola curve while the winter parabola is bigger in size and uses the lower part of the parabola curve to give the fixed focus. For this purpose, the reflector assembly is composed of flexible crossbars and a frame to induce the required change of the parabola curves with the changing solar declination. The paper also presents the calculation procedure of seasonal parabola equations for standing reflectors in the southern hemisphere as well as for laying reflectors in the northern and southern hemispheres. Highly reflective aluminium sheets are used on the crossbar profiles to complete the concentrator. The reflector is installed at the required site by setting its axis of rotation at an angle equal to the latitude of the site. For daily tracking, these concentrators rotate along an axis parallel to the polar axis of the earth at an angular velocity of one revolution per day with the help of simpler and cheaper self-tracking devices. For seasonal tracking, the reflector rotates at half the solar declination angle with the help of a telescopic clamp mechanism. The design procedure is simple, flexible and does not need any special computational setup, thus offering the prospect of potential application in domestic as well as industrial configurations.