Influence of the gas composition on the efficiency of ammonia stripping of biogas digestate

AbstractImpact of strip gas composition on side stream ammonia stripping, a technology aiming at the reduction of high ammonia levels in anaerobic reactors, was investigated. Evaluation of the effect of oxygen contact during air stripping showed a distinct, though lower than perceived, inhibition of anaerobic microflora. To circumvent, the feasibility and possible constraints of biogas and flue gas as alternatives in side stream stripping were studied. Experiments, with ammonia bicarbonate model solution and digestate, were conducted. It was demonstrated that the stripping performance is negatively correlated to the CO2 level in the strip gas with a progressive performance loss towards higher concentrations. In contrast to biogas with its high CO2 content, the efficiency reduction observed for flue gas was significantly less pronounced. The later provides the additional benefit that its high thermal energy can be re-utilized in the stripping unit and it is therefore considered a viable alternative for air

Methods for Response and Recovery Time Measurement of Hydrogen Sensors

Widespread use of hydrogen in the transport sector requires that associated safety issues be addressed and safety sensors will play an important role in doing so. These sensors must satisfy certain requirements in order to ensure that they can reliably and accurately alert to the presence of hydrogen - such performance standards are currently being laid in place. Our sensor testing facility has been constructed for the purpose of testing hydrogen sensors under various conditions. We have previously assessed the performance of a range of sensor technologies in terms of accuracy, measuring range, cross-sensitivity and dependence on ambient parameters. The work presented here aims at the development of a reliable method for evaluating sensor response t(90) and recovery times t(10). A number of methods have been tested, principally the "flow-through" and "diffusion-box" methods described in the draft ISO standard: ISO DIS 26142. The principal difficulty with these methods is in producing an instantaneous change in the test atmosphere. Our efforts have been directed at developing a method that both gives reproducible results and minimizes this changeover time. We report the optimum conditions found for the flow-through method, as well as improved variations of the diffusion-box method. These methods have then been used to test response and recovery times of a number of sensor technologies as a function of hydrogen concentration.JRC.DDG.F.2-Cleaner energ

Performance Testing of a MOSFET Sensor

The use of safety sensors, which can reliably and accurately alert to the presence of hydrogen, will be an essential element in the transition to a hydrogen economy, and the satisfactory performance of such sensors must be assured. Our dedicated sensor testing facility has been constructed for the purpose of testing hydrogen sensors under a wide variety of conditions. We have previously established a test protocol for assessing the performance of such sensors, taking into account the range of conditions likely to be encountered in their service lifetime, as well as the stated requirements of car manufacturers. We have also previously assessed the performance of a range of sensor technologies. The work presented here is the result of tests carried out on a commercially available sensor based on MOSFET technology. MOSFET (Metal Oxide Semiconductor Field-Effect Transistor) devices are so called because they consist of field-effect transistors composed of a metal layer, an insulator layer (usually an oxide) and a semiconductor layer. Our measurements include accuracy of response, measuring range, cross sensitivity to CO, detection limit and the influence of ambient temperature, pressure and relative humidity. The results of these tests are presented here, and compared with those acquired for other sensor types, as a means of assessing the performance of this type of technology in the detection of hydrogen for safety applications.JRC.DDG.F.2-Cleaner energ

Photovoltaic single cell energy harvesting

Jsou popsány možnosti využití fotovoltaických článků v uspořádání single-cell pro Energy Harvesting (EH) na velmi nízké energetické úrovni. Pokud není účinnost nejdůležitějším parametrem, může být single-cell uspořádání cenově výhodné v mnoha aplikacích. Srovnání vlastností příslušných technologií ukazuje, že pro zamýšlené použití jsou nejvhodnější tenkovrstvé anorganické fotovoltaické články. Je velmi důležité zvážit provozní podmínky, v nichž budou fotovoltaické články pracovat, a přizpůsobit tyto podmínky jejich výběru. Vzhledem k velmi malé ploše článku potřebné pro konvertory nízké energie není cena fotovoltaického článku významnou položkou v celkových nákladech na EH převodník. Pro toto použití byl navržen jednoduchý a spolehlivý převodník DC-DC s nízkou cenou.This work was supported by project no. FEKT-S-14-2300 “A new types of electronic circuits and sensors for specific applications”.The paper describes the possibilities of Energy Harvesting (EH) using photovoltaic single cell energy harvesting. When the efficiency is not the most important parameter single-cell can be cost-effective in many applications. Comparison of the properties of respective technologies shows that for intended application there are most advantageous inorganic thin film cells. It is very important to consider the operating conditions in which EH will work and adapt these conditions to the selection of the photovoltaic cell. Because of very small area of the cell needed for the low energy EH converters the price of the photovoltaic cell is not an important item in the total cost of an EH converter. Simple and reliable low price JFET driven DC to DC converter was designed for this application