For those living in areas without reliable electricity from alternating current, smartening up their homes could be as simple as using a DC microgrid. These types of microgrids minimize transmission losses by covering a smaller area using shorter lines, generating electricity locally, and are more reliable sources of power for these areas.
The benefits of applying DC instead of AC are clear. Homes can have DC circuits that connect rooftop solar units to batteries to charge cellphones and other electronics. Solar energy yields DC power. Also, batteries to store energy from solar cells are charged with DC. The IEEE 1547 suite of standards cover how to connect a DC microgrid to a main electric power system and distributed resources like solar and wind, as well as how to store that energy. Adopting these standards will ultimately help communities get access to inexpensive power and eventually smarter homes, explains Sri Chandrasekaran, the director of standards and technology, based in the IEEE India office, in Bangalore.
“DC microgrids are going to be applicable globally because they will solve problems in countries with similar issues and will also help developed countries use this technology more broadly,” he says.
One of the activities of the IEEE Standards Association (IEEE-SA) Industry Connections program is the Indian Low-Voltage DC Forum, which is exploring the merits of supplying DC microgrids to homes and commercial buildings in India. The program brings together marketplace competitors to build consensus and incubate standards and other shared products and services.
Many areas in India do not receive electricity from the main grid, and those that do experience several hours of blackouts during the day, according to Chandrasekaran, so alternative methods of generating electricity are needed. Micro-utilities that run on DC that use renewable energy technology like solar panels to power nearby homes, businesses, and schools are popping up in Cameroon and Nigeria thanks to IEEE Smart Village, a signature program of the IEEE Foundation. Since development of the micro-utilities began in 2011, the program has supplied electricity to some 50,000 people.
SAVING TIME AND MONEY
Just as smart-home appliances, meters, and other gadgets are anticipated to save consumers and utilities money, DC power is expected to do the same. Most of the appliances and devices inside a home run on DC and conversions from AC to DC need to be performed, which require additional driver hardware. But there’s also energy loss because of these conversions.
“Switch gears, drivers, and such are all favorable to DC implementation,” Chandrasekaran notes. “If you have DC coming directly into your home, you don’t need all that other equipment.”
Going forward, we’ll start to see a hybrid AC/DC type of home, he says.
“AC is not going to vanish anytime soon,” Chandrasekaran notes. “We need to understand how these hybrid systems will work together because the outlets need to differentiate between AC and DC since the two cannot be randomly interchanged. Those technologies are still evolving, and I think they will play a key role not only here in India but also throughout the world.”
That’s because a lot of people in the developed world are becoming what Chandrasekaran calls “prosumers”—consuming electricity but also producing it from, for example, solar panels on their roof. They will buy power from the utility when it’s cheap, and then sell it back when it’s more expensive. To be able to do that, the home has to be able to support both AC and DC current, he says.
That’s why the IEEE Industry Connections Program is working on solid-state transformers, which are two-way transformers that receive AC or DC input and output AC or DC. Today’s transformers are AC to AC or DC to DC.
“Since solid-state transformers are based on solid-state electronics, the form factor will be completely different,” Chandrasekaran says. “We no longer will see the big transformers we have now. The research is getting quite mature and the Industry Connection Program will keep an eye on how this technology is evolving.”
This article is part of our December 2015 special report on smart homes.