DESIGN AND SIZING OF A DIGESTER COUPLED TO AN AIR SOLAR COLLECTOR - Energy Research Developments: Tidal Energy, Energy Efficiency and Solar Energy - page 148

h :

volumic exchange coefficient (W/m 3 /K)

loss coefficient of the storage (W/m 2 /K)

U :

D: diameter (m)

f :

porosity

ρ :

air density (kg/m 3 )

C : air specific heat (J/kg/K)

p

storage cross section (m 2 ) A:

surface mass flow rate (kg/m 2 /s)

G :

ρ :

stone density (kg/m 3 )

C : stone specific heat capacity (J/kg/K)

pg

k conduction coefficient (W/m 2 /K) :

p

Introduction

Continuous development rests on the conciliation between economic and social
development, the protection of environment and the conservation of the natural resources.
Hence, the contribution of renewable energies is of major interest. It is the case of the biogas.
The objective of this project, which also fits with Algerian national concerns, aims at the
energy autonomy of the populations installed in the rural, agricultural and wedged zones,
characterized by their far distance from distribution networks of conventional energies. The
biomass used must be abundant on the site of the digester. For this purpose, the use of cows'
dungs was retained. Moreover, a complement of substrate must be locally available through
other biomass contributions as livestock dejections, agricultural and kitchen wastes and
domestic worn water. Besides energy and financial advantages and the life improvement of
rural population, environmental impact is not the least. Indeed, in Algeria, the principal
preserved resource would be the forest biomass which constitutes, in rural zone, a privileged
energy source for cooking and heating.
In accordance with first experiments of the bio-methanisation of cows' dungs [1] our
study presents a second phase of our objective, namely:

• the design and sizing of a digester with a floating bell

• the sizing of a low temperature air solar collector for the heating of the digester

Family Digestor

Operating Basis

This family Digester is inspired by an Indian model [2]. It is made up of an underground
waterproof digestion enclosure which offers anaerobic conditions and the retaining of
moisture. It thus allows the bio-methanisation of a fluid biodegradable biomass (animal