One of the first deployments of direct current (DC) – a form of electricity that was dominant worldwide more than a century ago – was on a U.S. Navy warship named the USS Trenton, commissioned in 1887. The 2 kW 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.
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 for terrestrial microgrid applications).
Like the majority of machines that run on electricity today, most ships run on alternating current (AC), the format of choice throughout the industrialized world. Nevertheless, the U.S. Navy is currently constructing a 78 MW DC ship under its DDG 1000 program. In addition, 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. (ABB 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%.)
ABCs of DC
Whether powering up a ship, data centers, or a cell phone tower, DC power is enjoying a comeback.
The business model that could help accelerate adoption of DC distribution networks such as microgrids is known as the A-B-C Model, which targets developing countries that make up approximately 80% of the world’s population, but consume only 30% of global commercially traded power. This approach, which is being promoted by The World Bank, United Nations, Rockefeller Foundation, and others, takes advantage of the following starting facts: 550 million people out of the estimated 1.4 billion people without power own a cell phone.
The “A” stands for anchor, and in most cases today, that anchor load for remote microgrids running on DC power is green telecom towers. “B” stands for businesses, which are the first customers served by the DC remote microgrid as the network expands. The “C” stands for community, and refers to the DC distribution network microgrid extending out to residents as the final phase of this remote microgrid expansion model.
This A-B-C Model is being implemented today through a variety of pilot projects. 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, since most off-grid cell phone towers run on DC power. These distribution networks are the largest market opportunity today, as evidenced by a recent report entitled Direct Current Distribution Networks by Navigant Research.
DC Telecom/Village Power System Revenue by Region, Conservative Scenario,
World Markets: 2013-2025
(Source: Navigant Research)
If we focus on the conservative scenario, total global capacity for DC distribution networks is expected to reach 2,308 MW by 2025, translating into worldwide vendor revenue approaching $25 million annually. The vast majority of this capacity, surprisingly, will come from DC systems only 1 kW to 2 kW in size in the developing world. In fact, almost 92% of total DC distribution network capacity will come from the green telecom/village power segment largely concentrated in regions such as India and Africa.
Ubiquitous mobile phones are helping to build this growing movement to shift from the current AC-dominated utility grid infrastructure back to the DC-based microgrids that were widespread at the birth of today’s electric utilities.
Tags: DC Networks, Distributed Generation, Microgrids, Renewable Energy, Smart Energy Program
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