Bench notes · LoRa · Solar

A forest sensor that smells bushfires before they flame

Imagine a sensor the size of a TV remote, strapped to a tree, that can smell a bushfire while it's still smouldering. It runs on a solar cell the size of a sticky note and reports over LoRa. That's Dryad's Silvanet, and with bushfire season starting it's one of the cleverest uses of LoRa and solar I've seen.

Why it's clever

• Smell beats sight. Cameras and satellites wait for smoke or heat. Silvanet picks up the hydrogen and carbon monoxide a fire gives off while it's still smouldering, often within the first hour.
• No batteries. A 6 × 6 cm panel charges supercapacitors, so there's no lithium to add fuel in a forest. Dryad rates it for 10–15 years without maintenance.
• LoRa all the way. Sensors talk LoRaWAN (AU915 in Australia) to solar mesh gateways, about 100 sensors per gateway.

The catch

One sensor covers about a hectare, so a 100 km² forest needs around 10,000 of them. That makes it a tool for high-value edges like towns, plantations and power-line corridors, not the whole Mount Lofty Ranges. The detection claims also come from Dryad itself, so independent Australian field results will be the real test.

The best bit for makers: the BME688 at its heart is a hobby part, and a solar LoRa air-quality node in MicroPython is coming up next.