Silvanet Wildfire Sensors (Gen 2)
Wildfire Sensors monitor the environment (temperature, humidity and air pressure, VOCs) to detect the presence of a smoldering fire during the ultra-early stages of a fire.
Dryad's Silvanet Wildfire Sensors are attached directly to trees to detect environmental air quality within a radius of 80 m to 100 m (260 ft to 320 ft).
These solar powered devices monitor the microclimate of the forest using an internal gas sensor and a Machine Learning model to detect the presence of a smoldering fire within range of the sensor.
Key features
Bosch gas sensor The Wildfire Sensor includes a Bosch gas sensor that combines ultra-low-power Air Quality sensing with a precise gas sensing mode. Carbon monoxide, hydrogen and VOCs (Volatile Organic Compounds) are detected at the ppm level with built-in artificial intelligence (AI) to reliably detect a fire and avoid false positives.
LoRa/LoRaWAN connectivity Connectivity to the Silvanet Network (Mesh and Border Gateways) is provided by a LoRA-integrated radio to send and receive messages via a robust LoRaWAN mesh network within a large forest environment or along rail lines, power lines or any linear areas. This allows the sensors to connect to distributed LoRaWAN-enabled Silvanet Mesh Gateways and Border Gateways.
Solar powered Power is supplied by a built-in solar panel to allow the sensors to run maintenance-free for 10 to 15 years without the need of batteries. As a precaution against the device itself starting a fire, it stores its energy in supercapacitors rather than batteries. This avoids the use of lithium and other toxic materials.
Attached directly to trees It is designed with a sturdy loop that allows the device to be attached directly to trees using treenails (permanent attachment) or with garden wire (temporary use only).
Delivered components
Each shipment of a sensors includes the following components:
Ten Silvanet Wildfire Sensors
Ten treenails and spacers (to keep the sensor away from the tree bark)
Dimensions and weight
The dimensions of the Silvanet Wildfire Sensor are (LxWxH) 19 cm x 9.2 cm x 1.34 cm. It weighs 136 g.
Ingres protection: Ingress protection of the housing is IP67. This means the housing is completely protected against dust and is watertight.
Gas sensor
The Silvanet Wildfire sensor uses the the Bosch gas sensor to monitor the microclimate of the forest. It is a low-energy hydrogen sensor that detects the presence of a smoldering fire over distances of up to 115 m.
This gas sensor detects the presence of Volatile Organic Compounds (VoCs) and Volatile Sulfur Compounds (VSC) and detects these compounds at <20 ppm.
Environmental detection
The gas sensor detects CO (Carbon Monoxide), H2, (Hydrogen) and VOC (Volatile Organic Compounds). It measures the environment's temperature, humidity and air pressure. It also monitors the microclimate of the forest by reading the following environmental values:
Air pressure: pressure in Pa
Humidity: relative humidity
Temperature: temperature in Celsius
Measurement conditions
In the Silvanet sensor, the gas sensor provides measurements under the following conditions:
Air pressure: 300hPa to 11000 hPa
Humidity: 0% to 100%
Temperature: -40°C to 85°C
Power consumption
The Silvanet Widlfire Sensor has very low energy consumption which is provided by its built-in solar panel. As a precaution against the device itself starting a fire, the sensor stores its energy in supercapacitors rather than batteries.
The two key components that consume energy are the gas sensor and the LoRa radio. The gas sensor consumes ~3.9 mA in standard gas scan mode. The radio consumes 7W of energy to operate so it can continue to operate in a shaded location for ~6 hrs.
Power supply
The Silvanet Wildfire Sensor includes a 60 mm x 60 mm solar cell on its front housing. It continuously generates energy during the daytime and recharges the device with sufficient power for the next 24 hours. After sunset, it begins to discharge until sunrise. After sunrise, it begins to recharge to 100% within about an hour.
Each day the solar panel harvests 7 W in the constrained conditions of a forest.
The solar panel provides sufficient energy supply to support continuous operation over a 24hr period while still having enough reserve power to support the powering of the gas sensor and to send a burst of messages when a smoldering fire is detected.
Sufficient ambient light is available in forests to provide sufficient light for the solar panel. Forests are never entirely dark during the day, even with a thick forest canopy.
Idle/active modes
Normally, the Silvanet Wildfire Sensor is in idle mode. Every 60 seconds it enter active mode to read the air quality. Then, every 2 hours it reads the environment, after which it sends a single packet to the Silvanet Cloud Platform via Mesh Gateways and Border Gateways.
These data packets contain normal (non-fire detection) environmental data which includes temperature, pressure and humidity internal values. These values are then displayed in the Site Details section of the Site Management app.
Supercapacitor Energy Storage
The Silvanet Wildfire Sensor uses a set of supercapacitors to store energy for use by the radio, gas sensor and other components. It stores the energy for day-to-day tasks and has a reasonable amount of reserve power to operate the gas sensor and radio module in case a potential fire is detected. As supercapacitors have an expected lifespan of 10 years or more, the sensors are essentially maintenance free. This allows for an expected lifespan of the sensor between 10 and 15 years.
Supercapacitors have a high capacity but a small maximum voltage of 2.7 V so a series of capacitors are loaded to 4 V. Capacitors are fully charged to 5.2 V.
Why use supercapacitors: Power supply is stored in supercapacitors rather than rechargeable batteries as they can potentially ignite. Consequently, using batteries would defeat the purpose of a wildfire detection system.
Calibration
After deployment, the Wildfire Sensor requires 14 days to calibrate. Until then it can generate false-alarms. See Sensor Calibration for details.
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