True, the field of interested industry observers has been growing. But with the notable exception of Japan, governments have been unengaged. So how is it that global standards are emerging for how we use direct current (DC) electrical power?
Economics are the key driver behind this, and that’s what’s causing the technical barriers to fall.
The technological trends are coming from both sides of the power equation: the sources that generate the power and the loads that use it. DC is the fastest growing sector in both of these areas and the standards-making process has sped up as their connection seeks the path of least resistance in practice.
Not far away from what’s thought of as the 'smart grid' discussion, the same goals are being pursued at the fringes of the grid network at lower cost but with higher efficiency and reliability. This has been made possible by taking the trend of distributed generation to its logical conclusion: optimizing microgrids that surround customers to make efficiency the guiding principle, instead of toiling only under the hub-and-spoke design the grid has used for a hundred years.
This innovation in the architecture of power delivery can get rid of three categories of losses: some of the transmission and distribution losses imposed on sending electricity that now doesn’t need to travel; the “inverter losses” that occur when DC sources likesolarPV are turned into the currency of the grid, which is alternating current or AC; and some “rectifier losses,” the typically large losses that occur when AC is converted back to DC for use in electronic devices that run on DC, which is increasingly common.
Not surprisingly, Japan has taken an early lead, because they are the largest importer of all types of energy amongst the world’s largest economies. In the early 1990s, the communications giant Nippon Telephone and Telegraph (NTT) set out to wring waste from its facility operations. Beginning with what they knew best, they started comparing the operating characteristics of AC and DC systems. Over eight years of research, they found dramatically higher reliability was achieved in the DC domain, and significantly, efficiency was improved, too. This operating voltage for computer server gear was provisionally defined in January of 2010 as 380V DC.
This activity did not happen in a vacuum, however. Industry groups that one way or another depend on semiconductors were working on other applications simultaneously, all over the world.
In 2005, the Electric Power Research Institute (EPRI) began to explore and expand upon interest on the part of the group's utility members and the data center community to investigate and demonstrate the benefits of DC power in IT applications. Named “The DC Power Partners,” an offshoot group designed and built a 2006 installation at a Sun Microsystems campus, with some of my company’s products, as well as products from Intel and others, with the Lawrence Berkeley Labs presiding. 380V DC was the backbone of this installation.
Over that same period, the first grid-connected, solar-assisted air handling system was built for the Town of Hempstead in New York, which took advantage of a 380V DC bus as a handy way to integrate solar PV (itself a semiconductor) into motor drives while avoiding the usual conversion to AC that distributed renewable systems had employed up until that point.
In 2007, Armstrong World Industries began to investigate a radical new idea for a fairly conservative company in its 147th year of existence. Aiming to provide their customers greater flexibility in how lighting fixtures and other devices in the ceiling plane could be managed, they turned to DC -- low voltage DC this time, and operating below the shock hazard level. By employing 24V DC, Armstrong could safely conduct electricity on its steel grid, and send power to wherever the customer might need it in the occupied space. This low-voltage use case has begun to change how architects, designers, electricians and engineers look at power systems for buildings.
Just one year later, a group of companies interested in establishing common standards of connectivity and interoperability joined forces with Armstrong and created the EMerge Alliance, a nonprofit that actively promotes DC standards, so that the broader industry could have a place to go for information and support. My company, Nextek Power Systems, is part of this organization.
The EMerge Alliance has now grown to over 70 members encompassing both the work of the 380V DC and the 24V DC pioneers, both of which are looking a lot more mainstream in the digital economy and are focused increasingly on renewable energy inputs.
Paul Savage is the CEO of Nextek Power Systems and a founder of the EMerge Alliance