IEEE Electrification Magazine - March 2015 - 8

TEchNOLOGY LEaDErS

many mass-manufactured and readily
available appliances are designed to
Microgrid
* Wired Distribution
operate at this voltage level.
* Trunk-and-Branch or Hub-and-Spoke
Recently, some small microgrid
Layout
developers have explored using low* Low-Voltage ac or dc Transmission
* Can Be Remotely Operated
voltage dc distribution systems. This
eneration
Generation
* Higher Energy Access Tier
strategy can reduce connection costs
Point
while enabling basic functions like
Energy Kiosk
* Energy Transported by Battery
lighting and mobile phone charging
* Mobile Phone, Electronic Device, or
rather than an electricity service comDedicated Portable Battery Kit Recharging
parable to the national grid.
* Operated by Staff
* Low/No Upfront Capital by Customer
With an eye toward scalability,
Generation
* Lower Energy Access Tier
microgrid developers are deploying
Point
systems that can be remotely and
SHS
automatically operated and man* Powered by PV
* Single or Small Number of Households
aged. In addition to providing valuServed
able data on system performance, it
* Lower Energy Access Tier
avoids having to find local employees
with sufficient technical and business
expertise. Cloud-connected meters
Figure 1. Common stand-alone electricity system architectures.
and other data acquisition systems
are used to monitor the microgrid,
collect payments, connect or discondepends heavily on the location and
and batteries, allowing the microgrid
nect customers, and even identify
size of the grid. Hydro turbines are
developer to install less battery and
theft of electricity. Data transmission
one of the lowest-cost options for
solar capacity. This is a useful strateand routing are important considergrids of at least a few hundred kilogy since PV and storage systems
ations in rural microgrids, and they can
watts of capacity in areas that are
without a backup generator need to
even influence the layout of the elecnear suitable rivers. Biomass systems
be sized to accommodate the "worsttricity distribution system.
are capable of producing low-cost
case" days and months, making
Distribution wires are laid in either a
energy and can be sized as small as a
them oversized for a typical day.
traditional trunk-and-branch layout,
few dozen kilowatts, but they require
Alternatively, some microgrids-typiwhich is used on national grids, or a
management of feedstock to ensure
cally those on the scale of hundreds of
hub-and-spoke pattern, as shown in Figconsistent power generation. Managkilowatts-may run dieure 2. Sometimes, a
ing the feedstock adds complexity to
sel generators as their
hybrid of the two is
Sub-Saharan Africa
microgrid projects, which already
prime source of power.
used. The hub-andtend to be quite complicated.
In these systems, PV
spoke pattern allows
has become a hotbed
Wind turbines can be practical for
panels can be integratfor the monitoring of
for new energy
areas with suitable wind resources,
ed into the microgrid
all lines to occur at a
entrepreneurs
although the recent dramatic drop in
without battery storage
central point, which
working in the space
photovoltaic (PV) prices has made PVs a
to displace some of the
has two advantages.
more economical option in most areas.
load on the generators
First, it makes energy
of isolated rural
In general, the solar resources across the
during the day and,
theft difficult because
microgrids, and
entire African continent are very strong.
thus, reduce fuel conall of the power lines
the market potential
An installed kilowatt of PV panels will
sumption.
are monitored at the
is immense.
often yield more than 4 kWh per day. PV
There are several
source. Second, data
systems also have the advantages of
pricing options for
transmission is simple
flexibility in scale and location.
distributing electricibecause the data can
Finally, traditional diesel generaty in microgrids. Most microgrids,
be broadcast from a single point. Howevtors can play an important role in
and all large grids over a few kiloer, hub-and-spoke architecture requires
microgrids, particularly in systems
watts in size, use ac distribution. Wirfar more wire than trunk-and-branch
that involve battery storage. A genering costs are reduced because higher
layouts, driving up the cost. For this reaator can provide standby backup
voltages-typically 220-240 V-can be
son, hub-and-spoke grids tend to be no
power when paired with a PV system
used. Customers also benefit because
more than about 10 kW in capacity.

I E E E E l e c t r i f i cati o n M agaz ine / march 2015

Table of Contents for the Digital Edition of IEEE Electrification Magazine - March 2015