| Summary: | Biogas is one of an alternative renewable energy source. Biogas
typically contains methane, carbon dioxide, hydrogen, hydrogen sulfide, water
vapor and silicon polymers. The energy of biogas mostly derived from the
methane and hydrogen. These gas with an LEL concentration about 40000 to
50000 ppm are highly flammable and explosive at standard temperature and
pressure. An instrument with metal oxide based sensor, TGS2611, can be made to
monitor the concentration of biogas up to 25% LEL or 10000 ppm.
Biogas samples from the digester model were used for the instrument
characteristic test. A mixture of water and cow dung was made as raw material
for this digester. Afte characteristic test, the instrument was applied to monitor the
process of biogas formation in two digester at different temperature during eight
days. This monitoring was conducted to determine the performance of the
instruments and the influence of temperature on the formation of biogas. Biogas
concentration in ppm was obtained from the regression of the output resistor (RO)
value recommended by the TGS2611 datasheet.
This research shows that the TGS2611 sensor output voltage has
proportionally changed to the temperature change, with an average value of
12,125 mV/°C at gas sensor A dan 12,875 mV/°C at gas sensor B. The instrument
requires initialization for one minute before start the monitoring process. The
instrument is able to monitor any increase or decrease of the biogas concentration
that occurred more than 10 seconds or 25 seconds, also it�s able to monitor the
biogas concentration above 10000 ppm but with diminishing sensitivity. Digester
with an average temperature of 34,48°C produces biogas faster and higher
concentration than the digester with an average temperature of 26,98°C after 34
hours of monitoring. Output resistance (RO) regression process resulting in biogas
concentration in ppm with an accuracy about 20%, due to the output resistor (RO)
tolerance.
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