Was Edison Right About Direct Current (DC) Microgrids?
The fledgling electric utility companies that emerged after Thomas Edison opened his small Pearl Street, New York City power station in 1882 originally focused on direct current (DC) microgrids. Edison envisioned that the electric utility industry would involve small firms generating DC power for individual businesses through these DC distribution networks. By 1886, Edison’s firm had installed 58 DC microgrids and some 500 isolated DC lighting plants in the United States, Russia, Chile, and Australia.
Shortly thereafter, the first DC ship developed by the U.S. Navy also began operation in 1887. The 2 kilowatt ship used electricity for lighting instead of the common practice of oil lamps. This may have been the first electric ship in the world, though that is a topic of considerable debate, and the U.S. Navy is currently constructing a 78 MW DC ship under its DDG 1000 program. One could also consider this antique DC ship a microgrid, since it was not interconnected to any grid. A similar argument is used today by Boeing, which refers to satellites powered by solar photovoltaic (PV) panels as remote DC microgrids (and whose expertise is now being applied by the company for terrestrial microgrid applications.)
Over the course of the early 20th century, isolated DC microgrids offered by competing entrepreneurs gave way to a monopoly system featuring centralized power plants owned by utilities. But the world has changed over the past 100 years. Interest in DC solutions for land, water and space applications is growing. The largest markets today existing in the developing world to power up ubiquitous cell phones and provide basic lighting services for the rural poor where utilities are virtually nonexistent.
Large technology players like ABB have been selling high-voltage DC transmission systems for about 5 decades; the company now also offers a variety of DC-based products relevant to more distributed systems, such as data center microgrids. (The company has also put forward an innovative design for next generation DC ships that can create efficiency savings of 20% and space and weight savings of 30%). Emerson Network Power, which specializes in power conversion, also offer technologies designed to optimize DC power solutions. Then there are smaller startups like Nextek Power, which possesses U.S. patents on DC power distribution optimization platforms enabling bidirectional power flows, offering a direct coupling technology that displaces the need for DC-AC inverters for microgrids and nanogrids interconnecting to the larger utility AC grid, an application ideal for net zero energy buildings.
The one area that offers the clearest prospect for industrialized economies to advance technology in the developing world is in the growing movement to shift from the current AC‑dominated utility grid infrastructure back to the DC-based microgrids that were widespread at the birthing of today’s electric utilities. These systems would subsequently pave the way for state-of-the-art DC microgrids in the developing world that could be networked together to optimize regional energy provision, initially anchored by green telecom towers. By far, these distribution networks are the largest market opportunity today.