IEEE Electrification Magazine - March 2015 - 9

The more traditional trunk-andbranch method allows many connections to share one main trunk line but
requires a meter at each end user so
that the energy usage is measured
separately. While this layout approach
benefits from more grid size flexibility
and lower distribution costs, it also
presents a heightened risk of energy
theft and a somewhat more challenging data transfer situation.
To solve the energy theft issue in
trunk-and-branch systems, some monitoring systems regularly reconcile the
total energy generated with the total
energy consumed. If there are discrepancies, the grid operator can investigate
to ensure that users are not bypassing
their in-home meters. To solve the data
transfer challenge, each meter can be
equipped with a subscriber identity
module (SIM) card and global system for
mobile communications (GSM) functionality. Alternatively, the meters may
use power line carriers or a wireless network to communicate information back
to a central point where it can then be
transmitted to the cloud. In general,
connectivity to a GSM network is not an
issue, even in very remote locations.

Payment and Billing
Microgrid developers must also
determine which billing and payment systems to use. Prepay systems
are common since they avoid having
to collect from customers in arrears.
Additionally, customers are able to
easily control how much they spend
and are very comfortable with prepay
systems as they are prevalent in the
mobile phone industry.
One type of prepaid system requires
compatible meters that are activated
by codes. Local agents sell scratch cards
with the codes that the customers
must then send in an short message
service (SMS) to add credit to their
account-similar to prepaid mobile
phone airtime. Another similar system
in use eliminates the scratch cards by
having the local agent send an SMS to
the microgrid developer when a customer pays. The agent receives a

Trunk and Branch

Hub and Spoke

Generation
Point

Figure 2. Trunk-and-branch and hub-and-spoke are two distribution line options for microgrids.

unique code in return that the customer then enters manually into his or her
in-home meter.
More advanced meters integrate
with the very prevalent existing
mobile money platforms. In these
systems, when customers make a
payment, their account balance is
updated and their line turns on automatically, eliminating the need for
any local agents. Meters are the fastest-evolving technology in microgrids,
with new companies regularly entering the market and experimenting
with new approaches.

Other Considerations
Microgrid developers also need to identify suitable sites and ensure that they
are compliant with the local regulators,
who often have strong opinions about
how electricity tariffs should be set. For
all of these reasons, the process of
developing and operating microgrids is
a challenging one that requires comprehensive local knowledge and
experience to navigate.

Energy Kiosks
Energy kiosks operate more like a
retail store than a traditional utility. A
typical energy kiosk serves walk-up
customers and is equipped to
recharge mobile phones, repurposed
automobile batteries, and, in some
cases, dedicated portable battery kits

(PBKs). Energy kiosks bridge the gap
between having no electricity at all and
having wired electricity in a home.
While larger batteries are capable of
lighting a household for over a week,
they require time and sometimes cost
to transport in addition to time spent
waiting for charging to complete.
As with microgrids, a variety of
sources can be used to power an energy kiosk. There are important technical differences, however. Energy kiosks
require energy primarily during business hours, so 24-h service and reliability may not be necessary, although
overnight battery charging is sometimes offered. Whereas microgrids can
be designed to require little on-site
presence, energy kiosks require
customer-facing personnel. This reduces the technical complexity of the
system but increases the organization
complexity, as the staff must be hired,
trained, and managed.
Collecting payments is straightforward since customers can simply pay
cash at the kiosk under pre- or postpay schemes. Payments are generally
not tied to the amount of energy supplied; rather, the assessed fee is based
on battery size or charging time-for
example a flat fee, usually around
US$0.25, is assessed for recharging a
mobile phone regardless of the battery size or initial state of charge.
Although rather unsophisticated, this
IEEE Electrific ation Magazine / march 2 0 1 5

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