Feature Article

The Death and Rebirth of DC Power

Direct current is replacing AC in microgrids and other setups that maximize the efficiency of lighting, HVAC, and onsite renewables.

August 4, 2016

The DC microgrid at the Tohoku Fukushi University continued to supply heat, hot water, and power to its hospital, nursing care facility, and other buildings in the aftermath of the 2011 earthquake.

Photo: NTT Facilities. License: Public domain.
Most of the energy-efficient equipment we use in our homes and businesses, from lighting to heat pumps to laptops, runs on direct current (DC). Unfortunately, power coming into our buildings from the grid is alternating current (AC) that has to be converted to DC. With each conversion, energy is wasted (see A Surge of Popularity for Efficient DC Power).

Integrating dedicated DC systems into buildings eliminates the need for these AC-to-DC conversions and can save energy and money, reduce carbon emissions, generate useful data, increase resilience, and add design flexibility. It also has massive potential to improve the connectivity of building systems as part of the growing Internet of Things (IoT).

The benefits could be significant and have garnered a lot of press over the last few years. But does the hype match the reality?

Let’s take a look back at the history of power distribution in the U.S.; the rebirth of DC; and the benefits, challenges, and realities of integrating DC power into our buildings today.