Economic feasibility of solar-powered led roadway lighting

The optical efficacy of light emitting diode (LED) has exceeded 72 lm/W in 2006. This implies that energy can be saved about 75%, as compared to mercury lamps widely used in roadway lighting. In some remote areas where the grid power cannot reach, independent solar-powered lighting using high-power LED provides a promising solution. However, the cost of solar photovoltaic device may cause the application of solar-powered LED roadway lighting to be not economically feasible.The present study investigates the design of the solar-powered LED roadway lighting using high-power LED luminaire (100 W) and estimates the installation cost for a 10 km highway with 2 lanes. LED luminaries are installed on both side of the road with staggered arrangement. The pole distance is 30 m. The cost comparison of LED lighting using grid and solar power with the conventional mercury lamps was carried out. It shows that the installation cost is 22 million USD for LED powered by grid power and 26 million USD for solar-powered. The total installation cost of conventional mercury lighting is 18 million USD. The excess cost of LED mainly comes from the cost of LED lamp and solar PV. But, the cost of power generation and electrical transmission line can be greatly reduced since about 75% energy was saved for LED. This permits the use of smaller copper wire and shorter line length for solar-powered system which in turn saves installation cost. The payback time for the excess investment of LED is 2.2 years for LED using grid power and 3.3 years for LED using solar power.