IEEE Electrification Magazine - June 2016 - 6

VIeWPOInT

Diesel generators are often found
in the developing world, but they have
negative economic, health, and environmental impacts. Negative economic impacts of diesel electric generation include the fact that businesses and wealthy homeowners typically
operate a diesel generator to supply
electricity at as much as US$1/kWh
(life-cycle cost). Recent advancements
in systems engineering, software,
power electronics, materials science,
and energy storage combine to enable
clean, quiet, affordable, and reliable dc
electric systems. Such systems are
capable of delivering high end-to-end
efficiency, with more than 99.999%
availability at less than US$0.20/kWh,
and can be rapidly set up anywhere in
the developing world. Applying highefficiency buck converters to convert
and regulate dc voltages, high-efficiency lithium titanate oxide (LTO)
batteries for electric storage, low-cost
solar photovoltaic panels, and select

dc products minimize power conversion losses and enable highly efficient operation. Depending on the
system configuration and layout,
resistive losses (e.g., line losses) may
be greater than cumulative losses
due to power conversion and
storage. Another advantage of this
architecture is that it enables a
solid-state power system configuration that ensures reliability, durability, and portability.

Military Operations
Military forward operating bases in
conflict zones present unique electrification challenges for which dc
microgrid architecture is ideally suited and can be rapidly deployed. A
number of dc solutions are being
used for such operations. Integrated
systems based on a simplified architecture can be assembled in hardened seismic-rated enclosures to
facilitate a portable, containerized

power system. Solar and small wind
generation coupled to LTO battery
storage can provide a dc grid anywhere that a ship, truck, or helicopter can reach. Pos-En, of the FREEDM
Systems Center at North Carolina
State University, and Schneider Electric, supported by the U.S. Trade and
Development Agency, have developed a containerized modular electric generator (MEG) capable of delivering up to 180-kW peak output at
380 Vdc with 45-kWh onboard LTO
storage and onboard dc generation.
Schneider is currently developing a
commercial version of the MEG.
Electric power systems for military applications must meet federal
building standards, National Electric
Code (NEC) standards, and applicable
military specifications (MILSPEC)
standards. A MILSPEC-compliant version of the MEG has not yet been
designed, but it is feasible. Missioncritical military assets (e.g., ships, aircraft, weapons, and forward operating bases) require compliance with
extreme MILSPEC standards. A number of MILSPEC standards are applicable to dc grids, with a baseline of
MIL-STD-810, that define environmental requirements impacting the
grid system, component selection,
and overall design. For example, certain (but not all) MILSPEC-compliant
electronics must operate properly
within the temperature range of
-55 °C to 125 °C. Certain aspects of
MILSPEC dc system design requirements may be classified.
A MEG can be transported using a
Skycrane (Figure 2) to a forward operating base. The MEG would include all
needed equipment, tools, and supplies to operate for an extended period without refueling and could be
disconnected, moved, and reinstalled
at another location in a few hours by
minimally trained personnel.

Telecommunications
The telecommunications industry
has always used dc, and with the
explosion in mobile, there is a need

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