IEEE Electrification Magazine - June 2016 - 40

Figure 4. The 98%-efficiency modular dc-dc converter components
being developed for dc microgrids.

projects. Committees are working on standards specifically focused on dc systems and including clarifications and
rules related to dc systems in present standards to help
local inspectors understand the differences between dc
and ac systems and give them the tools to identify which
safety cautions should be required in dc systems.
As greater standardization is achieved and a larger
variety of dc loads become available, hybrid systems combining ac and dc loads and generators will allow early
implementation of dc microgrids. Some hybrid microgrids
can be implemented with the dc bus as the backbone of
the system where the power and energy management is
executed, while ac loads and classical ac generators are
integrated using inverters and rectifiers. Although this
system has disadvantages with respect to an optimized dc
microgrid using higher-efficiency dc loads, it enables the
verification of control concepts and provides data about
installation, maintenance, reliability, and performance
that would validate economic models used to attract additional investment and customers.
This effort is starting to show results, with more attention on and additional financing of dc microgrid projects.
The California Energy Commission announced in 2015 the
funding of a demonstration project led by Robert Bosch
LLC to implement a dc microgrid at a Honda distribution
center. In March of 2016, the Canadian Federal Government announced the financing of a dc microgrid demonstration project led by ARDA Power Inc. at an industrial
plant in Ontario, Canada. Since energy storage is the centerpiece of microgrids, battery companies are getting an
increasing number of requests from developers to integrate their storage units directly with a dc bus and to execute microgrid-management functions embedded in the
energy-storage controls.

Road to Commercialization of dc Microgrids
To reach extended global use of a technology, in addition
to the usefulness of the innovation, several other conditions have to be met. These include a cost that matches
the market value of the proposition, mature off-the-shelf
components, a minimum project-specific engineering and

I E E E E l e c t r i f i c ati o n M agaz ine / j un e 2016

approval effort, and easy installation and maintenance.
Despite the early efforts for standardization and cooperation, dc microgrid demonstration projects will use a diversity of bus voltages and custom components. Solutions
will be improvised to solve technical and compliance
issues and many of these solutions will not be designed
with immediate market expansion in mind. As more demonstration projects are built and interest grows in the
market, components and procedures will naturally evolve
toward standardized requirements.
Although demonstration and early adapters of
microgrids will benefit from incentives and philanthropists, to achieve extended use of dc microgrids, the cost
has to be competitive with other alternatives. To reach
cost-competitive system hardware, all the components
required in the installation have to be optimized for cost.
The solar industry has reached a cost level that makes it
competitive, but optimization and larger volumes are necessary in other dc-specific components (loads, protections,
hardware, etc.). A significant effort in the generation of
safety standards for dc installations and dc components is
necessary, and this effort will be fed by results and experiences from demonstration projects. With safety standards
in place, the components in a microgrid would be able to
reach a level of standardization and manufacturability
that would allow multiple manufacturers to compete for
the market based on quality and price. As the volumes
increase, more cost-efficient manufacturing procedures
and lower-cost materials may push classical electrical
components operating on dc toward the cost targets, turning them into commodities.
The energy storage is the most critical and immature
element in a microgrid. Battery technologies are evolving quickly, moving toward the performance levels
required for durable and economical microgrids. However, massive cost reductions in energy-storage technologies are necessary to shift the microgrid concept from a
niche market to a mass market. The cost reduction cannot be at the expense of performance, as microgrids will
have to compete with traditional power sources in durability and reliability. Improvements in performance and
cost of lithium-ion batteries, as well as incoming technologies that are a better fit for the deep cycles required
in microgrids (such as flow batteries), provide hope that
in short time, a competitive cost of energy storage will
be reached.
Residential and commercial ac electrical installations,
including loads such as heating, cooling, and lighting, are
installed and maintained by electrical contractors and
approved for safety using simple and low-cost procedures.
The same model will be necessary in dc systems to make
them cost effective. Regulated training of electricians has
to be implemented, and guidelines and recommended
practices have to be written and followed. In parallel,
system standardization, off-the-shelf components, and
mature regulatory standards will lead to simplified

Table of Contents for the Digital Edition of IEEE Electrification Magazine - June 2016