Is direct current making a comeback?

On August 6, 1890, William Kemmler, an illiterate German convict, died as a 1,000-volt AC current shot through his body. Little did Kemmler know that what made him the first human being to be executed by electrocution was actually the result of rivalry between two American electric companies — GE and Westinghouse.

Kemmler had become a pawn in the corporate ‘war of currents’ which centred around the type of current being pushed for commercial use — alternating current (AC) or direct current (DC).

The man who was responsible for putting Kemmler in the electric chair was a proponent of DC and financially and politically supported ‘electric chair execution’ to discredit AC. He is a man we all know as Thomas Alva Edison.

Edison lost the war, despite killing Kemmler and several animals to demonstrate the dangers of AC (though DC is equally dangerous), which continued to prevail.

Now, DC is making a comeback, even at low-voltage levels. Its resurgence is significant because DC-based devices consume less power.

The recent formation of a ‘Low Voltage DC Forum’ under the aegis of the Institute of Electrical and Electronic Engineers is one sign of its resurgence.

Trends
Of late, two mega trends are evident in the field of electricity. First, changing lifestyles are skewing consumption towards DC, as most devices we use today work on direct current — mobile phones, laptops and desktops, flat-screen TVs — and come with devices that convert AC to DC.

Second, the energy-saving drive has spawned DC devices. Two examples of this are ‘brushless DC’ motors and LED lights.

A DC-motor-based ceiling fan consumes 60 per cent less electricity, and while a 60-watt incandescent bulb consumes 3,285 units of electricity, an LED lamp that gives same light needs only 329 units. 

Kameswara Rao, Executive Director-Energy & Utilities, PwC, says that as the society develops, goes digital, smart and green, a spurt in the number of DC applications is inevitable.

So, how can direct current be supplied when generation is almost entirely AC?

Votaries of DC have two answers to this. First, DC generation will grow, thanks mainly to solar energy. Today, new commercial buildings and residential blocks are mandated to have rooftop solar plants. In future, solar is expected to become the norm. Upcoming industrial estates could have solar farms and their own DC microgrids. Millions of remote villages in India could be powered with solar-microgrid combo, and people living there will need DC appliances.

Second, if you convert AC into DC at one central point rather than at each device, you save power.

Electronic companies are said to be working on DC-based appliances. Philips, for example, sees a DC comeback. “We strongly believe that DC has a future within a scope of mini or microgrid. More the electronic loads depend on DC and more the energy generation from solar, DC will have a significant role to play,” says M Geetha, Director-Research Engineering Solutions, Philips.

Philips makes LED lamps, but the “production of other appliances depends on the way the ecosystem progress,” she said. LG, Samsung, Panasonic, Videocon and Bajaj Electricals did not respond to Business Line’s mails. 

uneconomical
However, Lalit Goel of Nanyang Technological University, Singapore, notes that it is uneconomical and difficult to build a new DC grid to replace the existing AC infrastructure.

However, he says DC hybrids can be easily implemented in new buildings. DC and AC systems co-existing in harmony due to advanced power electronic techniques will provide more green and high quality energy with the highest efficiency, he says.