The research engine used in this work was a Honda Nova Sonic.
It is a single-cylinder, gasoline engine with overhead camshaft.
Bore and stroke are 58 and 47 mm, respectively. The displacement
volume is 125 cm3. The combustion chamber is cylindrical in shape
with the compression ratio of 11:1. The four-stroke, naturally aspirated,
water-cooled, spark ignition engine is a popular motorcycle
engine model in Thailand. Since the biogas is used as a source of
energy in place of gasoline, the engine must be modified to accommodate
the use of biogas [15]. Consequently, the carburetor is replaced
with a gas–air mixer also known as a venturi mixer. Biogas
is supplied through a plastic pipe and mixed with inlet air in the
mixer. Change in airflow quantity and velocity causes a change
in pressure at the channel contraction which in turn affects a
change in flow of biogas to join and mix with the main airflow in
the required proportion, prior to intake into the engine cylinder.
Pollution free, abundant and relatively cheap. Biogas from anaerobic
digestion of animal manure waste is one of the most promising
options. Biogas production process for energy, fertiliser supplement
and sanitation has made a significant impact for livestock
production business and rural development. Biogas technology
has been successfully developed and widely disseminated in Thailand
[10]. Rural households use biogas for cooking. Many farms
utilise it for heat, shaft power and electricity [11]. Alternatively,
biogas powered refrigeration systems may be conveniently
adopted by agro-based rural areas for air and water cooling, as
well as food and vaccine preservation. Some works included those
by Siddiqui [12] in which optimum combined cooling and heating
performance of a biogas powered absorption refrigeration system
was presented. The use of biogas from waste water treatment
was proposed by Castro Villela and Silveira [13] to be utilised
as fuel to power absorption and vapour compression refrigeration
systems for cold water production. For a compact refrigeration
system module in remote localities, an automotive air-conditioning
system may provide a suitable solution because of its availability
at relatively low cost, and simplicity to use, maintenance
and repair. So far, number of studies concerning this system is
rather limited [14].
It is clear from the survey of available literature that there has
been a modest amount of work reported on biogas engine driven
cooling system for rural use. In this paper, attempt has been made
to adopt biogas engine to drive the vapour-compression automotive
air-conditioning system. Experimental tests were carried out to
investigate performance of the modular refrigeration module.