More than 300 million people in rural communities in India have no access to electricity—greater than the entire U.S. population. In winter 2011 Value Development Initiatives (VDI), in collaboration with D-Lab, began phase one of a solar microgrid project: designing and installing a 40-home microgrid in a rural Indian village. However, the system is far from optimal—little testing was done on the LED units before deployment, so more efficient devices may be available. In addition, the current system is unable to meet demand for a service perhaps as large as lighting itself in off grid communities—mobile phone charging.
A small centralized charging system has already been added to the system, but only has the capacity to charge 10 phones per day—far less than the number of phones in the village—and risks long term damage to the grid’s batteries. In-home charging, however, would free people from constant trips to other towns to charge their phones, and could potentially be much more profitable. The amount of power supplied to each house is miniscule—1.5 watts for 6 hours a day. By further optimizing the voltage supplied to the LEDs, we were able to design a circuit which can charge a cell phone in less than 6 hours while keeping one LED on, and provides an additional LED when a cell phone is not being charged—all using same power as the current design. The additional up front cost of this upgrade is estimated to be about $6 when deployed in volume. We estimate an extra $1.50 could be charged per month for this service, making the payback period about 4 months.
As a further improvement, VDI was interested in whether there were LED units on the market that were a better fit for the system. To answer this question, we quantitatively tested five LED units available in India for brightness (lux) and efficacy, then performed qualitative user testing, including evaluation of light color, and usefulness for reading and tasks. Our initial results showed that using the current LED, adding a third module in series resulted in a lower overall power draw and significantly increase light output.
Furthermore, results showed that one LED model (LBMNW4)drew 1/3 the power of the installed LED and cost 1/3 the;price, yet users showed no preference between the two. This could potentially allow for significant cost savings by reducing the size of the solar panel and batteries, or by allowing as many as 9 LEDs per house, including 3 during cell phone charging. Here is a two minute video that gives you an idea about the project.