Ashok Jhunjhunwala, Bhaskar Ramamurthi, Krishna Vasudevan, Lakshmi Narasamma, Uma Rajesh, R. Kumaravel, M. Sairam, Janani Rangarajan, IIT Madras (firstname.lastname@example.org)
Uninterrupted Direct Current (UDC) is first-of-its-kind system which guarantees uninterrupted power supply from the grid even during black-out situations. Designed by Prof Ashok Jhunjhunwala and Prof Bhaskar Ramamurthi, and their team at Indian Institute of Technology-Madras, the system attempts to address three problems:
When demand for power exceeds supply, the power distribution companies (Discom) are forced to cut power in some localities resulting in a “power-cut” or black-out. Power cuts exist in most parts of the country and can be as high as 20 hours a day in some remote locations.
In recent years, it is known that DC (direct current) driven Brushless DC fans and LED lights consume less than half as much power as their AC counterparts. Also, all electronics (TV, PC, cellphones, etc) use low-power DC power, and AC-to-DC convertors used to power/charge these devices are energy inefficient. Yet, energy-efficient alternatives could not be used in the absence of a DC line at homes.
Power from solar panels is known to have reached grid-parity in terms of cost per unit of D.C. power generated. Decentralised use of roof-top solar panels tosupplement grid power would enable home-users to draw significantly less power from the grid during the day-time, and therebyreduce load on the grid during the day-time peak period. However, the additional cost, inefficiency and complexities of DC-AC conversion has prevented any pull from being created for decentralised solar installations. Besides, rooftop solar panel solutions available today provide supplemental power only when grid power is present! This makes them useless during blackouts.
The team at IIT Madras has come up with a technology that addresses all these problems in an innovative manner.The solution involves the following:
A second power-line at 48V DC is installed at homes, which provides limited, but un-interrupted (by black-outs) power to homes. When demand exceeds supply, the Discom instead of cutting power in some localities will get the sub-stations in these localities to continue to supply power, although only a small fraction and at a different voltage. Thus instead of black-out, they would create a “brown-out”. A device (called Uninterrupted DC Power Module or UDPM) at each home will sense this condition and cut-off the low voltage AC power-feed into the home; however, at all times (during normal powercondition as well as duringbrown-out condition) the devicewill provide a limited amount of 48V DC power on the second line. The line will never be interrupted, except when there is maintenance shut-down.
The DC power-line can be used only with DC appliances like DC fans, LED lights and DC adapters/chargers for cell-phones, laptops and TV. The limited amount of uninterrupted DC power supplied is good enough for 2 such lights and fans and a cell phone charger, and when one of the two fans is not used, a 24” LCD / LED TV with set-top box can be powered. The attractive possibility of running these DC appliances un-interrupted with a small amount of DC power creates a market-pull for energy-efficient DC appliances at homes.
If one wants to power more appliances on the DC line, a home user can install a solar panel which directly interfaces with the 48V DC line; a small battery can be integrated to power additional appliances in the evenings. No DC-AC conversion or additional power-conditoning electronics is required. Thus, a pull for decentralised solar panel installation by the home owners is created. The owner can install panels incrementally when there is money available for the investment. Since only panels have to be installed, the cost of DC power generated is no more than the cost of grid-power.
The system has been tested at a few homes at IIT Madras and is now being introduced for proof-of-concept demonstrations in TN, Kerala, Karnataka and AP.
Prof. Bhaskar Ramamurthi, Director, IIT Madras said that “this innovative technology shows how India can not only adopt green solutions, but actually help itself in the process by ensuring assured power to its citizens and a large amount of decentralized solar power generation. This goes against the conventional belief that going green has an associated cost burden that comes in the way of development”.
Prof. Ashok Jhunjhuwala feels that “this technology has the potential to remove the burden of power-cuts from the lives of ordinary people, enabling them to be productive. By incentivising a switch to energy-efficient appliances and roof-top solar panels incrementally, it enables citizens to not only help themselves but also contribute to national well-being by reducing power consumption and generating some of it themselves.”
For more information on IIT Madras: http://www.iitm.ac.in/
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