Artículo Científico / Scientific Paper |
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pISSN: 1390-650X / eISSN: 1390-860X |
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DESIGN OF A TSUNAMI EARLY WARNING SYSTEM FOR ECUADOR BASED ON SATELLITE |
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DISEÑO DE UN SISTEMA DE ALERTA BASADO EN TERMINALES SATELITALES |
Aldair Alarcón Rubio1, Arturo Cadena Torres1, Freddy Villao Quezada1,* |
Abstract |
Resumen |
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The Ecuador earthquake on April 16, 2016, with a moment magnitude of 7.8, generated a small local Tsunami event clearly registered by the DART (Deepocean Assessment and Reporting of Tsunamis) buoy system which took less than 10 minutes to arrive to the coast of Esmeraldas. Ecuador has the risk of a major Tsunami event occurring near to its shore. Under this scenario of a Tsunami event near to Ecuadorian shore, a Tsunami Early Warning System to alert vulnerable coastal cities based on the readings from the Tsunami Buoys located at Ecuadorian waters is mandatory. This paper describes the design of a Tsunami Early Warning System for Ecuadorian Coast based on short-burst satellite terminals installed on Tsunami buoys near the Ecuadorian shore and early warning siren located at coastal cities. The system installed on the Tsunami buoy has access to the BPR (Bottom Pressure Recorder) readings; in case of a Tsunami event registered by the BPR, the system automatically sends a data frame to trigger the early warning siren at the coastal cities. |
El terremoto de Ecuador ocurrido el 16 de abril de 2016, con una magnitud de 7.8, generó un pequeño tsunami local, evento registrado claramente por el sistema de boyas DART (Deep-ocean Assessment and Reporting of Tsunamis), el cual le tomó menos de diez minutos en arribar a las costas de Esmeraldas. Ecuador tiene el riesgo de un tsunami de gran magnitud cerca de su costa. Bajo el escenario de un tsunami cerca de la costa ecuatoriana, un sistema de alerta Temprana de tsunami para alertar a las ciudades costeras vulnerables basado en las lecturas de las boyas de tsunami localizadas en aguas ecuatorianas es mandatorio. Este artículo describe el diseño de un sistema de alerta temprana para la costa ecuatoriana basado en terminales satelitales de ráfaga corta instalados en las boyas de tsunami cerca de la costa ecuatoriana y sirenas de alerta temprana localizadas en ciudades costeras. El sistema propuesto instalado en las boyas de tsunami tiene acceso a las lecturas del BPR (Bottom Pressure Recorder). En caso de un evento de tsunami registrado por el BPR, el sistema automáticamente envía una trama de datos para activar las sirenas de alerta temprana en las ciudades costeras. |
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1,*Facultad de Ingeniería Eléctrica y Computación, ESPOL, Ecuador. Autor para correspondencia : fvillao@espol.edu.ec. http://orcid.org/0000-0002-4371-5562, http://orcid.org/0000-0002-2806-8707, http://orcid.org/0000-0003-4282-4924. |
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The proposed system is based on low cost microcontrollers with open source code and solar panels with ultracapacitors as energy storage unit to ensure high endurance without significant maintenance. Based on the field test results, this design for a fully autonomous early warning Tsunami System turned out as potentially appropriate to protect the population of Ecuadorian coastal cities. |
El sistema propuesto se basa en microcontroladores de bajo costo con código abierto y paneles solares con ultracapacitores como unidad de almacenamiento de energía para asegurar larga duración sin mantenimiento significativo. Basados en las pruebas de campo, este diseño para un sistema de alerta temprana de tsunami totalmente autónomo resultó apropiado para proteger a la población de las ciudades costeras ecuatorianas.
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Figure 2 shows the proposed Tsunami Early Warning System Architecture. The selected satellite terminal was Skywave IDP 690 for marine applications and IDP 680 for land applications. These satellite terminals operated through the Inmarsat satellite network.
2.2. Buoy station
2.2.1. Tsunami buoys in Ecuador.
Ecuador has got two MESEMAR Tsunami Buoys DART II (Deep-ocean Assessment and Reporting of Tsunami) operated by INOCAR. These buoys are located near the Manta and Esmeraldas shores at the coordinates 1°7.8’S, 81°46’W and 0°38.47’N, 81°15.70’W [16]. A deployed buoy by INOCAR at Ecuadorian waters is shown in Figure 3 [17]. The Dart II System is formed by a Bottom Pressure Recorder (BPR) and a surface buoy. The BPR is located at the seafloor, communicated with the surface buoy by an acoustic data link. The surface buoy has a satellite terminal to send data frames to the Tsunami Warning Monitoring Station in approximately real time.
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manually, and then a Tsunami warning could be issued for the population that lives at coastal cities.
2.2.2. Proposed buoy station hardware.
The buoy station is a self-powered device with the appropriate size and mass to avoid significant displacement of the buoy’s center of mass. The buoy station has a cylindrical shape and can be installed externally, on the mast of the buoy. The hull of the buoy station is made by reinforced UV resistant plastic and has removable bulkheads to access the onboard electronics. The diameter is less than 30 cm and height less than 40 cm. The bulkhead has O-rings and penetrators for underwater environment to ensure hermeticity for the onboard electronics. The onboard electronic is formed by the satellite terminal Skywave IDP 690 and power supply. The proposed architecture can be seen at Figure 4. The terminal Skywave IDP 690 delivers data over the IsatData Pro service using the global Inmarsat constellation [18]. The terminal is inside the buoy station to protect it from sea environment. The IDP 690 has an external RS232 port and four input/output analog or digital pins. The RS232 port can be connected to the CPU of the MESEMAR buoy to have access to the data frame of the BPR. The terminal has an internal microcontroller that manages the resources. This microcontroller is programming by scripts implemented by open source Lua programming language. Also, it is included a framework with the necessary tools for the developers. The firmware for this application will process the data frames from the Tsunami buoy CPU and generates messages to the alert station and monitoring station. The terminal can send messages up to 6400 bytes and receives message up to 10000 bytes. The typical latency is less than 30 s with messages of 100 bytes. The input voltage is between 9 to 32 V. An important characteristic is the “sleep mode” usefully to save energy. The consumed energy depends on directly of the message length and number of messages per day. The buoy station power supply is composed by solar panels and an ultracapacitors stack. The usage of ultracapacitors allows high endurance without maintenance at sea. The size of the ultracapcitors and number is calculated from the necessary energy to transmit and receives a message and the number of message per day. Typically, the weather at Ecuadorian waters is cloudy as can be seen in Figure 3. For this reason, the number of solar panels is calculated to operate with low solar radiation level. This application requires more than the 2.7 V of a typical ultracapacitor, therefore the ultracapacitors are connected in series. An essential part of ensuring long operational life for this configuration is to balance each ultracapcitor to prevent current leakage from causing damage to other ultracapacitor |
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running on a PC process the message and data from the Iridium Transceiver and Xbee transceiver respectively. After the power supply was tested, the components were installed onboard the Buoy Station. The Buoy Station Prototype was deployed at a lake continuously for 30 days, sending and receiving messages through the satellite terminal and Xbee without energy storage problems.
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EVENT or EXERCISE message was sent from the web account, the system sent a data frame to trigger a hypothetical Tsunami Siren trough the Xbee data link. The received data frame is visualized in a Labview application running on the PC. During the day an average rate of 2 message/hour were sent using the Iridium Transceiver. The average voltage level during the 30 days was 17.6 V. During the night, the achieved max number of messages was 87 before the voltage level dropped under the lower limit. After the sunrise, the system toke near 4 hours to get fully charge and start again.
In cloudy days with less than 2 hours of plenty sunlight, the voltage level dropped to 13.4 V. After 30 days, the Buoy Station was disassembled to inspect internal components. Firstly, they were inspected for sings of corrosion and leaking from the bulkhead, there was no evidence of corrosion or leaking. The voltage level of each ultracapacitor was measured to ensure correct operation of the passive balancing circuit. The ultracapacitors have an average voltage of 2.5 V. This was the unique field test. More testing will be carried out at sea. A disadvantage of the Buoy Station Prototype is the material, it is not tested against UV radiation from the sun. Large UV radiation exposure at sea probably could compromise the structural integrity of the device. The passive balancing circuit might not guarantee the ultracapacitor endurance greater than 5 years. It is considering an active balancing circuit with low power consumption.
4. Conclusions.
A Tsunami Early Warning System that can fully autonomously issue an alert to protect the population of coastal cities under the scenario of a local Tsunami event that could arrive in less than 10 minutes was presented. This paper proposed the design of Tsunami Early Warning System for coastal cities based on satellite terminals and ultracapacitors as a storage energy unit powered by a solar panel array to ensure long term deployments without maintenance. Based on the experiments carried out, the proposed project for an early warning Tsunami System turned out as appropriate. |