Design and implementation of sensor systems for control of a closed-loop life support system

The sensing and controlling needs for a Closed-Loop Life Support System (CLLSS) were investigated. The sensing needs were identified in five particular areas and the requirements were defined for workable sensors. The specific areas of interest were atmosphere and temperature, nutrient delivery, plant health, plant propagation and support, and solids processing. The investigation of atmosphere and temperature control focused on the temperature distribution within the growth chamber as well as the possibility for sensing other parameters such as gas concentration, pressure, and humidity. The sensing needs were studied for monitoring the solution level in a porous membrane material along with the requirements for measuring the mass flow rate in the delivery system. The causes and symptoms of plant disease were examined and the various techniques for sensing these health indicators were explored. The study of sensing needs for plant propagation and support focused on monitoring seed viability and measuring seed moisture content as well as defining the requirements for drying and storing the seeds. The areas of harvesting, food processing, and resource recycling, were covered with a main focus on the sensing possibilities for regulating the recycling process

Piezoelectric vibration energy harvesting from airflow in HVAC (Heating Ventilation and Air Conditioning) systems

This study focuses on the design and wind tunnel testing of a high efficiency Energy Harvesting device, based on piezoelectric materials, with possible applications for the sustainability of smart buildings, structures and infrastructures. The development of the device was supported by ESA (the European Space Agency) under a program for the space technology transfer in the period 2014-2016. The EH device harvests the airflow inside Heating, Ventilation and Air Conditioning (HVAC) systems, using a piezoelectric component and an appropriate customizable aerodynamic appendix or fin that takes advantage of specific airflow phenomena (vortex shedding and galloping), and can be implemented for optimizing the energy consumption inside buildings. Focus is given on several relevant aspects of wind tunnel testing: different configurations for the piezoelectric bender (rectangular, cylindrical and T-shaped) are tested and compared, and the effective energy harvesting potential of a working prototype device is assessed

Feasibility study on application of microwave radiometry to monitor contamination level on insulator materials

This paper introduces a novel method for monitoring contamination levels on high voltage insulators based on microwave radiometry. Present contamination monitoring solutions for high voltage insulators are only effective in predicting flashover risk when the contamination layer has been wetted by rain, fog or condensation. The challenge comes where the pollution occurs during a dry period prior to a weather change. Under these conditions, flashover can often occur within a short time period after wetting and is not predicted by measurements taken in the dry period. The microwave radiometer system described in this paper measures energy emitted from the contamination layer and could provide a safe, reliable, contactless monitoring method that is effective under dry conditions. The relationship between equivalent salt deposit density and radiometer output is described using a theoretical model and experimentally verified using a specially designed X-band radiometer. Results demonstrate that the output from the radiometer is able to clearly distinguish between different levels of contamination on insulator materials under dry conditions. This novel contamination monitoring method could potentially provide advance warning of the future failure of wet insulators in climates where insulators can experience dry conditions for extended periods

Testing of hydrogen sensor based on organic materials

Práce je zaměřena na problematiku bezpečnostních vodíkových senzorů. Základní principy a teorie vodíkových senzorů je rozebrána v první části práce. Je navržena metodologie testování organických vodíkových senzorů vyvinutých a vyrobených na Fakultě Chemické Vysokého Učení Technického v Brně. Nejslibnější organický material byl testován. V závěrečné části byl navržen teplotní regulátor pro použití s keramickou senzorovou platformou.This thesis is focused on topic of safety hydrogen sensors. Theory of hydrogen sensors and main sensor principles are discussed. Methodology for testing of organic hydrogen sensors developed and fabricated at the Faculty of Chemistry of Brno University of Technology is outlined. A set of tests is done for the most promising organic material. Also, temperature regulator for ceramic sensor platform is designed.

Methodological Approach for the Development of a Simplified Residential Building Energy Estimation in Temperate Climate

Energy ratings and minimum requirements for thermal envelopes and heating and air conditioning systems emerged as tools to minimize energy consumption and greenhouse gas emissions, improve energy e ciency and promote greater transparency with regard to energy use in buildings. In Latin America, not all countries have building energy e ciency regulations, many of them are voluntary and more than 80% of the existing initiatives are simplified methods and are centered in energy demand analysis and the compliance of admissible values for di erent indicators. However, the application of these tools, even when simplified, is reduced. The main objective is the development of a simplified calculation method for the estimation of the energy consumption of multifamily housing buildings. To do this, an energy model was created based on the real use and occupation of a reference building, its thermal envelope and its thermal system’s performance. This model was simulated for 42 locations, characterized by their climatic conditions, whilst also considering the thermal transmittance fulfilment. The correlation between energy consumption and the climatic conditions is the base of the proposed method. The input data are seven climatic characteristics. Due to the sociocultural context of Latin America, the proposed method is estimated to have more possible acceptance and applications than other more complex methods, increasing the rate of buildings with an energy assessment. The results have demonstrated a high reliability in the prediction of the statistical models created, as the determination coe cient (R2) is nearly 1 for cooling and heating consumption

Sensor Systems for Prognostics and Health Management

Prognostics and health management (PHM) is an enabling discipline consisting of technologies and methods to assess the reliability of a product in its actual life cycle conditions to determine the advent of failure and mitigate system risk. Sensor systems are needed for PHM to monitor environmental, operational, and performance-related characteristics. The gathered data can be analyzed to assess product health and predict remaining life. In this paper, the considerations for sensor system selection for PHM applications, including the parameters to be measured, the performance needs, the electrical and physical attributes, reliability, and cost of the sensor system, are discussed. The state-of-the-art sensor systems for PHM and the emerging trends in technologies of sensor systems for PHM are presented

Elaboration and characterization of humidity sensors for environmental monitoring

The water content in surrounding air is an important factor for the well-being of humans and animals, as the level of comfort is determined by a combination of two factors: relative humidity and ambient temperature. Humidity is also an important factor for operating certain equipment such as high-impedance electronic circuits, electrostatic-sensitive components, high-voltage devices, fine mechanisms, etc. Nonetheless, moisture is the ingredient common to most manufactured goods and processed materials. Thus, humidity sensors have been receiving wide attentions since decades. Yet, despite the high request, major advances in these sensors in terms of simple structure, lower cost, better selectivity, durability and reliability are always needed. Throughout the years, a large number of materials based on polymers, composite and ceramics have been tested, due to their own features and specific operating conditions. However, great attention has been paid to ceramic materials due to their chemical inertness which allow them to operate in harsh conditions. Amongst the different studied humidity sensors, impedance-based ones are used most commonly. The operation principle of the impedance sensors is based on the dependence of the impedance (or either capacitance or resistance) of the sensor element recognizing the nature and amount of water molecules on the surface or in the bulk. The resistance or impedance of the resistive-type sensor decreases as the relative humidity (RH)increases. Ions or electrons, or both of them, are the conduction carriers for resistive-type humidity sensors. The common construction of the resistive-type ceramic humidity sensors consists of a ceramic substrate with noble metal interdigitated electrodes coated with humidity sensing ceramic materials, both deposited by screen-print technique [1]. Metal oxides and metal oxide based composites are the most popular materials to be used as resistive sensing elements: TiO2, TiO2–SnO2, TiO2–WO3, TiO2–Cu2O–Na2O, KTaO3//TiO2(bilayered), TiO2/KTaO3 (bilayered), TiO2–K2O–LiZnVO4, Al2O3, AlO(OH), SiO2, WO3, Cr2O3–WO3, SnO2, a noble metal doped SnO2, SnO2: ZrO2 (bilayered), single Sb doped SnO2, K+-dopedSnO2–LiZnVO4, MnO2 –Mn3O4, Li+-doped Fe2O3, Au3+ and Li+ co-doped Fe2O3, Li+, Zn2+ and Au3+ co-doped Fe2O3, NiMoO4–MoO3, Li+-doped NiMoO4–MoO3, CuMoO4–MoO3 and PbMoO4–MoO3 [1]. Spinel-type oxides and composites based on spinel-type oxides are also used for humidity resistive sensing elements: MgAl2O4, Sr2+-doped CoAl2O4, Sr2+-doped BaAl2O4, Sr2+-doped ZnAl2O4, MgFe2O4, MgAl2O4–MgFe2O4, Mg0.8Li0.2Fe2O4, Mg0.9Sn0.1Fe2O4, MgFe2O4–CeO2, MgCr2O4–TiO2, Zn2SnO4–LiZnVO4 and ZnCr2O4–K2CrO4 [1]. Finally, Perovskite-type oxides and composites based on perovskites have been used for humidity sensing elements too: NaH2PO4 doped BaTiO3, MnTiO3, Li+ doped Ca0.35Pb0.65TiO3, BaNbO3, LaFeO3, K+-doped nanocrystalline LaCo0.3Fe0.7O3 (La0.93K0.07Co0.3Fe0.7O3) and Sr-doped SmCrO3 (Sm0.90Sr0.10CrO3) [1]. Preparation techniques can considerably affect the physical, chemical and gas sensing properties of the metal oxide sensors. Developments of new preparative routes, as well as compositional variations, are two perspective approaches for the design of highly sensitive and selective gas sensor materials.Reference: [1] T.A. Blanka, L.P. Eksperiandova, K.N. Belikov, Recent trends of ceramic humidity sensors development: A review. Sensors and Actuators B, 228 (2016) 416–442

The State of the Art in Fuel Cell Condition Monitoring and Maintenance

Fuel cell vehicles are considered to be a viable solution to problems such as carbon emissions and fuel shortages for road transport. Proton Exchange Membrane (PEM) Fuel Cells are mainly used in this purpose because they can run at low temperatures and have a simple structure. Yet to make this technology commercially viable, there are still many hurdles to overcome. Apart from the high cost of fuel cell systems, high maintenance costs and short lifecycle are two main issues need to be addressed. The main purpose of this paper is to review the issues affecting the reliability and lifespan of fuel cells and present the state of the art in fuel cell condition monitoring and maintenance. The Structure of PEM fuel cell is introduced and examples of its application in a variety of applications are presented. The fault modes including membrane flooding/drying, fuel/gas starvation, physical defects of membrane, and catalyst poisoning are listed and assessed for their impact. Then the relationship between causes, faults, symptoms and long term implications of fault conditions are summarized. Finally the state of the art in PEM fuel cell condition monitoring and maintenance is reviewed and conclusions are drawn regarding suggested maintenance strategies and the optimal structure for an integrated, cost effective condition monitoring and maintenance management system

Fluidic hydrogen detector production prototype development

A hydrogen gas sensor that can replace catalytic combustion sensors used to detect leaks in the liquid hydrogen transfer systems at Kennedy Space Center was developed. A fluidic sensor concept, based on the principle that the frequency of a fluidic oscillator is proportional to the square root of the molecular weight of its operating fluid, was utilized. To minimize sensitivity to pressure and temperature fluctuations, and to make the sensor specific for hydrogen, two oscillators are used. One oscillator operates on sample gas containing hydrogen, while the other operates on sample gas with the hydrogen converted to steam. The conversion is accomplished with a small catalytic converter. The frequency difference is taken, and the hydrogen concentration computed with a simple digital processing circuit. The output from the sensor is an analog signal proportional to hydrogen content. The sensor is shown to be accurate and insensitive to severe environmental disturbances. It is also specific for hydrogen, even with large helium concentrations in the sample gas

Examination of silver-graphite lithographically printed resistive strain sensors

This paper reports the design and manufacture of three differing types of resistive strain sensitive structures fabricated using the Conductive Lithographic Film (CLF) printing process. The structures, utilising two inks prepared with silver and graphite particulates as the conductive phase, have been analysed to determine electrical and mechanical properties with respect to strain, temperature and humidity when deposited on four alternative substrate materials (GlossArt, PolyArt, Teslin and Melinex)