Design of a LED-based sensor for monitoring the lower explosion limit of methane

Investigating flexible feeding effects on the biogas quality in full‐scale anaerobic digestion by high resolution, photoacoustic‐based NDIR sensing

“…To enable a test of larger temperature ranges, the system, including the electronics, has been placed in a climatic chamber and the change in signal as a function of temperature has been recorded in the range of 15–45°C. Figure B shows the results revealing a linear dependence of the signal on temperature, which is in accordance with previously obtained results and in contrast to systems employing only semiconductor components, which show exponential dependence on changes in temperature.…”

“…The results presented here do concur to a considerable degree with the readings from a state of the art gas measurement device. The main deviation occurs in the methane channel reading and the timing coincides with extraordinary high concentrations of H 2 S. Cross‐sensitivities towards this latter gas can be ruled out due to the working principle of the photoacoustic sensor setup employed . Likewise, mechanical instabilities are unlikely the cause of this since the adjacent CO 2 channel does not suffer at all.…”

“…(C) Aerial view of the experimental biogas plant at Eningen, Germany. Both digester feed into the secondary fermenter, which is why the measured biogas quality is always a mixture as generated by both digesters and the secondary fermenter previously obtained results [23] and in contrast to systems employing only semiconductor components, which show exponential dependence on changes in temperature.…”

“…Modulation of the light source leads to the exiting soundwave whose amplitude is related to the amount of target gas in the measurement channel. About a decade ago, the first attempt to miniaturize this simple concept did use a micro-electro-mechanical system pressure sensor to gauge the light intensity of a thermal emitter [22], and since then different combinations of various types of broad band light sources and devices for determining the photoacoustic signal have been developed [23][24][25][26][27][28][29][30][31]. While the use of lasers in combination with acoustic resonators in setups of direct photoacoustic spectroscopy allow for ultra-sensitive trace gas detection, the use of such devices outside the laboratory is challenging [32][33][34][35][36].…”

Real‐Time Gas Quality Data for On‐Demand Production of Biogas

“…For CO 2 the resolution is better than 8900 ppm and for CH 4 better than 15 000 ppm. No cross‐sensitivity against water vapor has been observed so far , .…”