Design and Testing of a Solar Torrefaction Unit to Produce Charcoal

Abstract

With increasing crude oil prices, fuels like kerosene and cooking gas have become unaffordable for many ordinary people in developing countries. For millions of Africans who need heat energy to cook their food, biomass like wood remains the easiest and cheapest source of fuel. Charcoal remains the most popular choice compared to wood since it can cook food much faster with very little smoke. Torrefaction of biomass is a mild form of pyrolysis at temperatures typically between 200℃ and 300℃ to produce charcoal. Torrefaction changes biomass properties to provide a much better fuel quality for combustion applications. A simple parabolic trough solar collector to produce charcoal by torrefaction process using solar energy has been designed from first principles. The device was fabricated and various locally available wood species were tested. The yield was found to be 21% to 35% with a production time of 90 minutes. The paper details the design procedure and the test results.