PAGE 30 Editorials from EE Faculty (Cont.) Environmentally Powered WSN for Air Quality Monitoring Operating in a “Set-and-Forget Scenario” Prof. Farid Touati Professor at the EED Qatar University This work aims at remedying a carry-over weakness in indoor/outdoor air quality (AQ) studies, which are conducted using expensive portable data loggers that allow just short-term and localized snap shots rather than a more conclusive long-term monitoring. The link between poor AQ and several health diseases has been confirmed in different studies [1-5]. The need to have satisfactory air pollutants monitoring systems that can improve reliability and data availability in places where traditional monitoring methods are difficult to establish, has led to the design of numerous autonomous systems able to check indoor and outdoor air qualities. Capillary wireless sensor networks dedicated to AQ monitoring have provided essential information on hazardous air the replacement of hundreds or even thousands of batteries on a regular basis that leads to high costs and practical problems of devices management. This work presents a multiconditions, generating early warnings to prevent danger situation for human health. The arising problem connected to capillary networks is the adoption of environmental energy as primary and/or unique energy source instead of parametric sensor node for AQ monitoring, able to work without battery nor human intervention, harvesting energy from the surrounding environment for perpetual operation. A complete autonomy system has been designed; and tested in lab and under indoor and outdoor environment in Doha and Italy (Technology Readiness Level 5/6; TRL5/6). TECHNOLOGY OVER- VIEW The technology is a wireless, multi-parameter environmental quality monitoring and diagnostics device that does not require batteries or grid power. The maintenance-free device can monitor in realtime a variety of AQ pollutants such as carbon monoxide (CO), nitrogen dioxide (NO2), nitrogen monoxide (NO), chlorine (Cl2), and hydrogen sulfide (H2S). It can also monitor environmental conditions like humidity, temperature, and barometric pressure. The battery-less device is powered by multiple renewable energy harvesting sources including radio frequency (RF), indoor and outdoor photovoltaic cells, thermoelectric, and piezoelectric devices. The proven environmental quality-monitoring device is modular and scalable such that many devices can be networked together in a cloud-based service platform. The GPS module enables sending data from multiple networked devices at different locations simultaneously. Real-time AQ data is collected and sent to an open-data platform that stores and provides open access to the data. Urban pollution mapping is enabled by integration of this system into a municipality, facilitating AQ monitoring and alerts fostering a better quality of life. An example of measurement campaign in Doha is shown in Figure 1. ABOUT THE TECHNOL- OGY How it works? The general structure of the system (i.e. SERENO) is depicted in Figure 2. It has been developed with the aim to reveal the air pollutants adopting low-cost and low-power design in indoor and outdoor scenarios. Different examples of chemical gas transducers can be found in the market. Each gas transducer has different operation principle, size, accuracy and power consumption. With the use of electrochemical technology, these sensors feature both small size and fast response time. Nevertheless, electrochemical sensors offer several advantages for systems that measure the concentration of different toxic gases. They operate with very small currents, making EED NEWSLETTER VOL. 2, ISSUE 1
VOLUME 1, ISSUE 1 PAGE 31 Figure 1 – An example of measurement campaign in the traffic jam in Doha (Qatar). Figure 2 – 3D view of SERENO (PCB top view) where the 6 (version 1, left side) or 4 (version 2, right side) gas sensors are shown. Version 2 features a local display. them appropriate for self-powered wireless nodes. All the sensing elements are gas tailored and show resolutions around one part per million (ppm) meeting International Standards in air monitoring arena (e.g. WHO).. The integration of numerous sensors (i.e., gas sensors, barometric pressure sensor, humidity sensor and temperature sensor) and the wireless data transmission into a single sensing board led to practical problems, especially in terms of energy consumption and energy management. To provide an autonomous source of energy for SERE- NO, one can consider scavenging energy from the environment with the aim to increase the battery longevity-energy stored (rechargeable mode) or go batteryless (set-and-forget scenario). The sources of energy that have been identified and can operate together in concurrent energy recovering functionalities are as follows: A vibration energy harvester Six high-performance thermoelectric generators (TEGs) One RF power source at 900 MHz One indoor thin-film amorphous silicon solar cell Technology Benefits Maintenance-free operation: system operates in a set-andforget mode EED NEWSLETTER VOL. 2, ISSUE 1
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