The results are in: 40% energy saved with LED street lights in Kolkata, India

Clare Saxon Ghauri
Reading time: 4 minutes
7 July 2014

NEW DELHI: The results of a LED street lighting pilot in the city of Kolkata, India, have been collected, revealing such compelling energy savings that the local government has decided to make the switch to low carbon lighting across the city. 

India's Kolktata Municipal Corporation has an ambitious plan to replace 300,000 existing street lights in its jurisdiction with LED street lights, based on the findings of a pilot project that proved LED lights perform to very high standards and deliver big energy savings.

Light emitting dioide (LED) technology is now widely accepted as a reliable, high-quality source of low carbon energy. Not only does its unique source of cool white light generate better visibility in night conditions, LED street lights also offer a huge electricity savings potential of around 50% compared to conventional street lighting technology such as metal halide, HPSV or HPMV (high-pressure sodium or mercury vapour) lamps. On top of this, LEDs have an almost five-fold longer life, meaning less maintenance bills. 

These facts were further certified in Kolkata's street light pilot project. Based on meter readings taken of energy consumption by an equal number of LEDs and HPSVs along the pilot stretch, there was an overall electricity saving of 40% due to the LED lights

Krishnan Pallassana, India Director, The Climate Group commented on the results: "The Climate Groups pilot intervention Kolkata has proven it makes sound business sense for any municipality to adopt LED street lighting. It also illustrates an immense business case for corporates and financial institutions to invest in LED street lighting. It is a classic case of improved technology directly contributing to reduced fossil fuel consumption, while enhancing all-round efficiency. Kolkata Municipality's initiative has the potential to catalyze an LED transformation in India, inspiring many other urban bodies. This is a win-win situation for all.”

A total of 110 LED lights and 110 HPSV lamps were installed on the road dividers of the Rash Behari Avenue Connector road, from the end of Bijon Setu to Ruby Crossing, where energy use data from the lights was measured between February and April, 2014.

Performance data of the LED luminaires was also recorded in February and March, on two different locations in the pilot project site, one of which was LEDs and the other baseline HPSV luminaires. Performance was measured through 'lux' levels compared with street lighting standards.

In the case of LED luminaires, an average photopic and scotopic (vision under well-lit and low light conditions) lux level of 56 and 97 respectively was recorded, which is way beyond the recommended lux levels of 30 lux for the type of roads tested. Also, average 'uniformity' and the ratio of minimum to maximum lux levels measured were well above the recommended standards.

While it should be noted HPSV-lit roads also met these required lux levels (with a modest 45), since HPSV is a source of warm light with observed 'correlated color temperature' of 2,300K, the scotopic to photopic lux level is below 1, which is less than ideal for producing high quality light during night hours.

An overall good performance of the LED street lights along with the lower input power requirements, show LEDs should get the 'green light' for scale-up, a result which reinforces The Climate Group's 2012 call for all new street lighting to be LED (or as efficient as) by 2015, and all street lighting the same by 2020.

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