In this study, an energy, exergy, and environmental (3E) analyses of a plasma-assisted hydrogen production process from microalgae is investigated. Four different microalgal biomass fuels, namely, raw microalgae (RM) and three torrefied microalgal fuels (TM200, TM250, and TM300), are used as the feedstock for steam plasma gasification to generate syngas and hydrogen. The effects of steam-to-biomass (S/B) ratio on the syngas and hydrogen yields, and energy and exergy efficiencies of plasma gasification (η_En,PG, η_Ex,PG) and hydrogen production (η_En,H2, η_Ex,H2) are taken into account. Results show that the optimal S/B ratios of RM, TM200, TM250, and TM300 are 0.354, 0.443, 0.593, and 0.760 respectively, occurring at the carbon boundary points (CBPs), where the maximum values of η_En,PG, η_Ex,PG, η_En,H2, and η_Ex,H2 are also achieved. At CBPs, torrefied microalgae as feedstock lower the η_En,PG, η_Ex,PG, η_En,H2, and η_Ex,H2 because of their improved calorific value after undergoing torrefaction, and the increased plasma energy demand compared to the RM. However, beyond CBPs the torrefied feedstock displays better performance. A comparative life cycle analysis indicates that TM300 exhibits the highest greenhouse gases (GHG) emissions and the lowest net energy ratio (NER), due to the indirect emissions associated with electricity consumption. ... Read more

This paper presents an area- and energy-efficient sensor readout circuit, which can precisely digitize temperature, capacitance and voltage. The three modes use only on-chip references and employ a shared zoom ADC based on SAR and ΔΣ conversion to save die area. Measurements on 24 samples from a single wafer show a temperature inaccuracy of ±0.2 °C (3σ) over the military temperature range (-55°C to 125°C). The voltage sensing shows an inaccuracy of ±0.5%. The sensor also offers 18.7-ENOB capacitance-to-digital conversion, which handles up to 3.8 pF capacitance with a 0.76 pJ/conv.-step energy-efficiency FoM. It occupies 0.33 mm in a 0.16 μm CMOS process and draws 4.6 μA current from a 1.8 V supply. ... Read more