A ₹20,000 Solar Box That Keeps Nilgai Out and Insects In

Farmers in western Rajasthan's arid and semi-arid belt fight a strange double front: insects that damage crops directly, and wild animals — nilgai, wild boar, stray cattle — that raid fields for food. The conventional response to each problem looks nothing alike. Insects usually get chemical pesticide, with all the cost, resistance, and environmental downsides that come with repeated spraying. Animal intrusion usually gets fencing, noise-makers, or in the worst cases, direct conflict — expensive, labor-intensive, or both.

A team at Agriculture University Jodhpur's College of Technology & Agricultural Engineering asked a simple design question: could one small, solar-powered box handle both problems at once, without chemicals, without grid electricity, and without harming the animals it's meant to deter?

The device splits into two subsystems sharing one solar power supply. The insect side uses three types of LED — ultraviolet (365-395 nm), blue (450-470 nm), and white — timed to switch on automatically at sunset, since different insect species are drawn to different wavelengths. Insects that approach the light contact a surrounding electrified mesh carrying a low current at 800-1200 volts, enough to neutralize them without a flame or chemical involved; the mesh sits above a cyclone separator that collects the dead insects for easy disposal.

The animal side works on an entirely different principle: rather than running continuously, a passive infrared (PIR) sensor watches a 5-7 metre radius and only activates a pair of ultrasonic speakers — emitting sound above 20 kHz, inaudible to humans — when it actually detects movement. That matters twice over: it saves battery power, and it avoids animals simply habituating to a constant background noise the way they eventually tune out a scarecrow or a continuously-running alarm.

The team ran the assembled device for 30 days at the university's instructional farm, logging insects trapped per night, species mix, animal intrusion events, power draw, and battery voltage — a real operating test, not a lab simulation. Two comparisons mattered most: multi-spectral light against single-wavelength traps for insects, and the ultrasonic system switched on versus off for animal intrusions.

The results were clear on both fronts. Combining all three light wavelengths trapped an average of 465 insects per night — 32 to 45% more than any single-color light alone, with UV as the strongest individual performer at 320 per night, followed by blue (210) and white (180). That gap matters practically: it means a multi-spectral trap catches meaningfully more pests per unit than the simpler, single-bulb traps already in some use.

On the animal side, weekly intrusion events dropped from an average of 10-12 without the system to just 2-3 with it running — roughly a 75% reduction. Because the ultrasonic system only fires when motion is actually detected, animals encounter it as an unpredictable deterrent tied to their own approach, rather than a fixed, learnable pattern they can eventually ignore.

The full unit — solar panel, battery, charge controller, LEDs, electrified mesh, ultrasonic speakers, and sensors — cost around ₹20,000 to build, covering roughly 1 to 1.5 acres per unit. Daily solar generation of 160-180 Wh comfortably outpaced the 110-130 Wh needed to run everything, leaving 1-2 days of battery backup even through cloudy stretches. On the numbers reported, the system pays for itself in about 15 months and then keeps running essentially free — no electricity bill, no recurring pesticide purchases, minimal maintenance beyond keeping the mesh and sensors clean.