Self-Cooling and Self-Cleaning LED Street Light with Rainwater Harvesting

The problem

High-wattage LED street lamps produce significant thermal load at the diode junction. When the heat sink cannot shed that energy fast enough, the junction temperature rises, accelerating lumen depreciation and shortening the life of the driver electronics. At the same time, outdoor fixtures collect airborne dust, pollen and exhaust residue on the lens. A dirty lampshade scatters the beam and reduces illuminance on the road surface, forcing municipalities to dispatch bucket trucks for manual washing. According to the patent, these two issues—overheating and lens fouling—increase the failure rate of LED street lights and drive up maintenance costs. Conventional air-cooled fins struggle in still, hot summer nights, and connecting a street light to a municipal water supply for active cooling or washing is impractical due to trenching and metering expenses.

The solution

The patent describes an LED street lamp that uses harvested rainwater as both a coolant and a cleaning fluid, eliminating the need for external plumbing.

1. A rainwater collection unit formed by a concave top panel (9a) on the lamp arm (9) catches precipitation and channels it through pipe one (7) into a water storage unit (3) housed inside the lamp post (1).
2. A temperature sensor (12) monitors the LED area. When the reading exceeds a set point, a controller (5) activates a water pump (4) on the storage unit.
3. The pump pushes water through an inlet pipe (16) into a water cooling radiator (14) mounted behind the LED (15) inside the lamp body (11), absorbing heat before the water returns via an outlet pipe (10) to the storage unit.
4. An illuminance sensor (20) measures the light passing through the lampshade (13). When dust causes the reading to drop, the controller commands a three-way valve (8) to redirect the pump’s output through pipe two (19) to a pressurized spray head (17) mounted on a bracket (18), which sprays water onto the lampshade to wash it clean.

Who it is for

• Municipal public works departments managing large street-light fleets in dusty or hot climates where manual washing crews are expensive to dispatch.
• Lighting contractors and EPC firms bidding on smart-city or green-infrastructure projects that reward water-neutral, low-maintenance designs.
• Industrial park and port operators whose high-mast fixtures accumulate heavy particulate and where downtime for lens cleaning disrupts logistics.
• Outdoor lighting brands looking to add a self-maintaining, water-cooled SKU to their catalog without relying on external water hookups.

How it works

The main parts

Operating sequence

1. Rain collection - Precipitation lands on the concave top panel (9a) of the lamp arm and flows down pipe one (7) into the water storage unit (3) inside the pole.
2. Cooling trigger - During operation, the temperature sensor (12) continuously reports the LED junction area temperature to the controller (5). When the value exceeds the programmed threshold, the controller starts the water pump (4).
3. Heat removal - The pump draws water through pipeline three (6) and the three-way valve (8) set to the cooling path, pushing it through the inlet pipe (16) into the water cooling radiator (14). The radiator absorbs heat from the LED (15), and the warmed water exits via the outlet pipe (10) back into the storage unit, forming a closed loop.
4. Cleaning trigger - The illuminance sensor (20) monitors the brightness passing through the lampshade (13). When accumulated dust lowers the reading below a set point, the controller signals the three-way valve (8) to switch positions.
5. Lens wash - With the valve redirected, the pump now forces water through pipe two (19) to the pressurized spray head (17) on the bracket (18). The nozzle sprays a jet across the outer surface of the lampshade, dislodging dust and grime. After a timed interval or once the illuminance sensor confirms restored brightness, the controller shuts off the pump and resets the valve.

Applications

Arid and semi-arid city streets

In regions where rain is infrequent but dust storms coat lenses quickly, the storage tank captures whatever precipitation falls and holds it until the illuminance sensor calls for a wash. This avoids scheduling tanker trucks to rinse fixtures along kilometers of roadway.

High-temperature industrial zones

Steel mills, cement plants and refinery perimeters expose fixtures to extreme ambient heat plus airborne particulate. The water-cooled radiator actively pulls heat away from the LED board during peak afternoon loads, while the spray function removes alkaline or oily dust that passive fins cannot shed.

Coastal and port facilities

Salt-laden air corrodes standard aluminum heat sinks and leaves a crusty film on polycarbonate lenses. Circulating fresh rainwater through the radiator flushes salt deposits internally, and periodic spray washes keep the lens clear without manual scrubbing that risks scratching the cover.

Smart-city pilot corridors

Municipalities deploying connected infrastructure can integrate the controller’s sensor data—temperature readings, pump cycles, illuminance recovery—into a central dashboard. Maintenance teams receive alerts only when the tank is empty or a component fails, rather than following fixed washing schedules.

Highway interchanges and overpasses

Fixtures mounted on tall masts above highway ramps are costly and hazardous to reach with bucket trucks. The self-cleaning loop extends the interval between physical inspections, keeping beam patterns compliant with road-safety standards while traffic flows uninterrupted below.

Where it is less suitable

• Regions with prolonged freezing winters - Standing water in the storage tank, pipes and radiator can freeze and burst unless drain valves or antifreeze loops are engineered into the design.
• Low-wattage residential fixtures - Small porch or pathway lights do not generate enough thermal load to justify a water-cooling circuit or the added weight of a water-filled pole.
• Areas with extremely low annual rainfall - If precipitation never fills the tank, neither the cooling nor the cleaning function can operate without an auxiliary fill port.