Utilization of solar energy in agriculture provides an extraordinary opportunity to promote small scale agro-based industry especially in tropical countries. Innovative solar collectors have opened several fields of applications of solar thermal energy at a medium and medium-high temperature level in post harvest and food processing. Essential oils extraction from herbs is one of the medium temperature agro-based industries. These oils are used in medicinal and pharmaceutical purposes, food and food ingredients, herbal tea, cosmetics, perfumery, aromatherapy, pest, and disease control, dying in textiles, gelling agents, plant growth regulators and paper making (Öztekin & Martinov, 2007). These oils are very expensive and a single ounce of most of the oils has worth thousands of Dollars. In the last decade, these oils remedies have gained enormous popularity in industrialized countries as well particularly in the multi-million-dollar aromatherapy business. Essential oils often extracted from the flowers, leave and roots plants, are an especially good solution to this problem. Out of all extraction methods, the distillation methods have advantages of extracting pure and refine essential oils by evaporating the volatile essence of the plant material (Malle and Schmickl, 2005). At present, there are often large and centralized distillation units mostly located in city areas. Due to their high operating costs, these are unmanageable by farmers or even groups of farmers in most of the developing countries. Further, some essential oils come from extremely delicate flowers and leaves that must be processed soon after harvesting. Thus, for functional, economic and environmental reasons, there is need of an on-farm solar distillation unit.
Various industrial surveys show that up to 24 percent of all industrial heat, directly used in the processes, is at temperatures below 180°C. In several industries, 100 percent process heat requirement is below 180°C which can be supplied economically by evacuated tube collectors and solar concentrators (Garg & Prakash, 2006). A solar distillation system was developed using Scheffler fixed-focus concentrator but it worked effectively only during sunny days (Munir & Hensel, 2009). The degree of reliability desired of a solar process to meet a particular load can be provided by a combination of properly sized collector and an auxiliary energy source. In the most climates, auxiliary energy is needed to provide high reliability and avoid gross over design of the solar system (Duffie & Beckman, 2006). For this purpose, solar distillation system was integrated with biomass energy to operate during adverse climatic conditions. The auxiliary biomass system comprises of a boiler, biomass furnace, and economiser and equipped with all safety mountings and fittings. The boiler operates under natural draught with the help of a chimney for efficient combustion process and can be operated with firewood, bagasse, spent and other biomass material etc. The main object of the work is to utilize solar energy as a primary heat source and the rest is provided by biomass boiler. The steam connection of the biomass boiler is injected into the distiller while bottom of the distiller is always exposed to beam radiations coming from the fixed-focus solar concentrator. The paper presents the development and experimental results of solar distillation system integrated with biomass energy for on-farm extraction of essential oils.
Reference: Munir, A. and O. Hensel (2009). Biomass energy utilization in solar distillation system for essential oils extraction from herbs. International conference for “Biophysical and Socio-economic Frame Conditions for the Sustainable Management of Natural Resources”(Tropentag 2009) on October.