It costs a lot of money to build a road … even more if you want to add wires to power the streetlights from the grid. Urban Green Energy (UGE) has a solution: an off-the-grid streetlight.
Each UGE light consists of two highly-efficient LED bulbs, two solar panels, a vertical axis helical wind turbine, and a 150Ah battery. One LED bulb produces over 3100 lumens of light while using 56W of electricity. (By comparison, you would need two 100W incandescent bulbs or one 70W high-pressure sodium lamp for the same light output.) Each solar panel generates 235 Watts (peak) and the wind turbine generates 200W at a wind speed of 12 m/s (about 27 MPH). That’s a pretty high wind speed, especially considering its low latitude. But keep in mind that on a busy highway there’s a lot of turbulent wind generated by the traffic.
Just running some conservative numbers, let’s say you can achieve a somewhat consistent 6 m/s wind. Wind power operates on the inverse-cube law, so cutting the wind velocity in half reduces the power by a factor of 8. That 200W turbine is generating a paltry 25W at this speed. If that occurs for 10 hours per day, we can generate 250 watt-hours of energy each day.
With a solar resource estimate of 4 Peak Sun Hours (PSH), each solar panel would generate 940 Watt-hours per day, so the pair gives 1880 Watt-hours per day. Combined with the wind resource, the system can generate roughly 2 kWh per day. A 56W bulb running 12 hours per day uses 672 Wh/day. Two bulbs requires 1344 Wh. This leaves around 700 Wh available to charge the batteries.
The math works out; the lights will be on when you need them. But I think the helical wind turbine serves more of an aesthetic purpose than anything else. With the above numbers, the turbine generates 12% of this system’s total energy. Based on my calculations, the system would work perfectly well without the turbine. But hey, it looks nice, doesn’t it?
Image and video: Urban Green Energy