Abstract:A universal pH indicator is used to fabricate a fiber optic ammonia sensor. The advantage of this pH indicator is that it exhibits sensitivity to ammonia over a broad wavelength range. This provides a differential response, with a valley around 500 nm and a peak around 650 nm, which allows us to perform ratiometric measurements. The ratiometric measurements provide not only an enhanced signal, but can also eliminate any external disturbance due to humidity or temperature fluctuations. In addition, the indicator is embedded in a hydrophobic and gas permeable polyurethane film named Tecoflex ® . The film provides additional advantages to the sensor, such as operation in dry environments, efficient transport of the element to be measured to the sensitive area of the sensor, and prevent leakage or detachment of the indicator. The combination of the universal pH indicator and Tecoflex ® film provides a reliable and robust fiber optic ammonia sensor.

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In this work we demonstrate efficient quality control of a variety of gasoline and ethanol (gasohol) blends using a multimode interference (MMI) fiber sensor. The operational principle relies on the fact that the addition of ethanol to the gasohol blend reduces the refractive index (RI) of the gasoline. Since MMI sensors are capable of detecting small RI changes, the ethanol content of the gasohol blend is easily determined by tracking the MMI peak wavelength response. Gasohol blends with ethanol contents ranging from 0% to 50% has been clearly identified using this device, which provides a linear response with a maximum sensitivity of 0.270 nm/% EtOH. The sensor can also distinguish when water incorporated in the blend has exceeded the maximum volume tolerated by the gasohol blend, which is responsible for phase separation of the ethanol and gasoline and could cause serious engine failures. Since the MMI sensor is straightforward to fabricate and does not require any special coating it is a cost effective solution for real time and in-situ monitoring of the quality of gasohol blends.

This contribution presents a methodology for the integration of Li-ion batteries discarded from electric vehicle into a collective self-consumption installation, showing the technical feasibility of such battery second use. In this regard, the state of charge (SOC) estimation is a relevant issue for the energy management of the second-life battery. Therefore, a SOC estimator is proposed in this contribution and tested in field. Moreover, the revealed costs analysis allows an economic comparison between the integration of a discarded battery pack in a second-life application or a remanufacture of these packs, thereby selecting the most suitable cells to build second-life batteries. This is a crucial issue for companies focused on the development of second-life batteries. The results obtained after testing the second-life battery pack in a real installation make it possible to extol the benefits of including this type of batteries in a self-consumption system, reaching a self-consumption ratio of 69 % and reducing by 36 % the maximum power peak demanded from the grid.

In this work, we proposed and demonstrated an efficient optoelectronic system capable to detect 1 gram of salt per liter of water (0.1% salinity) in real time employing optical fiber technology as sensing medium and embedded systems of National Instruments Company to get an accurate instrumentation process. In addition, the sensitivity of this salinity sensor can be enhanced by reducing the diameter of the optical fiber sensor structure ( by employing a controlled tapering process. More specifically, the sensitivity of this device has been raised from 141.933 nm/Refractive Index Unit (RIU) for an un-tapered sensor structure to 352.915 nm/RIU for a tapered sensor structure . In fact, considering that the tapered sensor structure provides an approximately linear response with a maximum sensitivity of 0.6624 nm / % salt, the percentage of salt is easily identified by monitoring the peak wavelength response.