Anyone who’s seen the Drunk History about the War of Currents knows Nikola Tesla was the electric Jesus who helped bring alternating current (AC) to the world, much to the chagrin of direct current (DC) proponent Thomas Edison. At the time of the Chicago World’s Fair in 1893, DC was the standard, but George Westinghouse started to win bids based on Tesla’s current, including one to power the world’s fair. Eventually, AC overtook DC because it was easier to transfer from the power station to the home, but DC power is what is used in many electronics in the home.
“It’s not meant to showcase what already exists. It’s really about what’s next.”
Laptops, solar cells, LED bulbs, and electric vehicles all run on DC power. When your computer’s charger gets hot, it’s giving off wasted energy as it converts AC to DC. But a small, 399-square-foot home in Detroit doesn’t need to do any converting. Run by NextEnergy, a nonprofit organization, the NextHome is a DC-connected house that’s a “living laboratory” for a variety of smart-home and energy technology.
“We have AC and DC running through the walls and through its wall plugs to add flexibility to the type of power that can be delivered to the loads inside the house, whether it’s your laptop or the TV or potentially the refrigerator,” Wayne Snyder, NextEnergy’s IT program manager, told Digital Trends when we toured the home. A power-distribution system from NextTech steps down the high voltage DC to a 24-volt level that gets delivered to the wiring. “The intent is to make the system safer to use, there’s less work that a licensed electrician has to do, there’s more flexibility,” says Snyder. “It’s not meant to showcase what already exists. It’s really about what’s next.”
The one-level, three-room building sits in the nonprofit’s parking lot. Outside the home, painted spring green, are two electric vehicle charging stations. One supplies both AC and DC power.
“Depending on what the vehicle battery management system is capable of supporting, we can charge faster or slower, AC or DC, so it adds flexibility to the future electric vehicle and hybrid electrical vehicle cars that we test and demonstrate out here,” says Snyder.
The DC charging gun uses a communication language for smart-grid applications, Smart Energy Profile 2.0. That means it can talk back and forth with the house, relaying messages about when to start and stop charging. If there was a grid outage, for example, the house could actually draw energy from the car’s battery. If cloudy weather meant the solar panels were providing little energy, the house could put the car’s charging on pause until sunnier skies prevailed. While the AC/DC charger isn’t open to the public, the other electric vehicle charger is.
Up top, the solar panels might actually be making too much energy — more than the house can use. Often, homeowners sell that surplus back to the power company, but the DC home can take it and store it in the Bosch storage system, with no extra conversion step. That’s one reason NextEnergy wanted to build the NextHome: AC must be converted to store it.
There are 16 channels in the DC power-distribution system, each providing up to 100 watts of power, primarily for low-powered devices. A single channel could light three bulbs, for example. But not everything runs on DC, at least, not yet. “It’s not going to power a stove or refrigerator,” says Snyder. The home still has AC for those appliances, but Bosch is working with NextEnergy to retrofit the fridge it supplied to accept DC current.