POWER April 2011 - 48

FUTURE POWER
2. EV testing. A plug-in hybrid electric vehicle
prototype is prepared for testing. Source:
Argonne National Laboratory
tion and Distribution: No Longer Separate
Spheres " ), and some industry watchers
predict that the percentage of demand supplied
by distributed resources is likely to
grow faster than central station generation,
for a number of reasons beyond the scope
of this article. Whatever percentage it supplies,
DG is likely to proliferate in large
part because its benefits typically outweigh
the challenges it introduces, especially
in times of economic and regulatory
uncertainty.
The benefits of adding more DG resources-whether
renewable or not-to a smarter
grid anywhere in the world include these:
PV module and integral line voltage inverter
with comprehensive communications capability
and the ability to improve power quality
and grid reliability through the injection
of VARs and non linear power. Remote
monitoring and control is achieved through
an integrated communications network that
creates an IP-based Smart Grid backbone
when deployed in large scale. " The systems
are said to be " compatible with existing grid
infrastructure " as well as emerging smart
grid technology and can be " remotely upgraded
to leverage future applications and
standards as they emerge. "
Petra Solar says the SunWave system's
price is " comparable to traditional PV technology "
but offers " a measurably better
return when installed behind the fence. " President
and CEO Dr. Shihab Kuran, PhD has
said that the technology is equally suited to
rural areas with lots of poles and urban areas,
where space for siting traditional renewables
is scarce.
In Sept. 2009 the company landed a contract
worth roughly $200 million with New
Jersey's Public Service Electric and Gas Co.
to make units for 200,000 utility and street
light poles in the state's six largest cities and
300 rural and suburban communities in the
utility's service territory. The company said
the project represented " the largest pole-attached
solar installation in the world. "
The company has also received a DOE
Energy Innovator Award and in Sept. 2010
was awarded $2.7 million in the DOE's
Stage III Solar Energy Grid Integration Systems
awards (one of four companies to win
an award).
The Pros and Cons of More DG
Distributed generation resources, of whatever
technology type, sit mostly at the distribution
level, rather than the generation
or transmission levels, though the whole
notion of " levels " would be moot with a
fully realized smart grid (see " Genera48
■
Incremental supply can be added closer to
where it's needed, whether by using rooftop
solar installations, quick-start engines, or
other sources, thereby deferring the larger
expense and regulatory trouble of building
utility-scale/central station generation.
■ DG can be sited where distribution lines
already exist. That's a significant advantage
that small-scale renewables have over
" utility-scale " renewable projects, which
often require new transmission lines.
■ DG improves efficiency by lowering
transmission line losses because the power
travels a shorter distance to its users.
■ DG can alleviate grid congestion (see
" DOE Program Fosters Integration of
Smart Grid and Renewable DG " ).
■ DG often can provide reactive power.
■ Reliability (particularly for customers that
are part of a microgrid or who own smallscale
generation that can be islanded) can
be improved by adding DG.
■ DG, particularly building-mounted PV,
typically requires less water and land than
similar capacity totals provided by central
station plants.
The " cons " of adding more DG to a grid
system fall largely into the categories of asset
control and grid control:
■ Asset control. DG resources will not always
be owned by a utility, and decisions
about adding distributed resources will not
always require utility approval. From the
point of view of a traditional utility looking
only at " lost revenue opportunities "
(rather than at systemwide efficiency and
stability and avoided plant-siting headaches)
that might be a negative. From a
customer standpoint, that could be a positive
feature, as the owner could choose the
type of DG to install.
■ Grid control. The proliferation of generation
sources that are small in scale but potentially
significant in the aggregate, and
whose operation may not be directly under
utility or grid operator control, could add
challenges to grid operation. Or, as the
North American Electric Reliability Corp.
put it (in the one paragraph devoted to DG
in its 137-page December 2010 report on
" Reliability Considerations from the Integration
of Smart Grid " ): " Distributed resources
have the ability to supply isolated
parts of the system during disturbances
and to supplement generation requirements
during large generator failures. At higher
penetration levels, distributed resources
can affect reliability, unless operators have
visibility and the ability to send dispatch
signals to them. Otherwise, balancing and
regulation would be challenging, and overall
bulk power system control, hampered. "
Generation and Distribution: No Longer Separate Spheres
As the North American Electric Reliability
Corp. (NERC) Smart Grid Task Force pointed
out in a March 2010 presentation, the
grid has traditionally been divided into
two separate systems: the generation
(conventional and hydro/bulk power/
transmission system) and the demand/
distribution system. Reliability requirements
and policy have been different for
each system.
Adding substantial nuclear generation
in the 1970s and 80s started to change
the picture. In the 21st century we are
beginning to understand that, as NERC
put it, " The development and successful
integration of [variable generation, distributed
generation, distributed energy
www.powermag.com
storage, demand response, and energy efficiency]
will require the industry to break
down traditional boundaries and take a
holistic view of the system with reliability
at its core. " And the smart grid is at the
center of that reliability picture, according
to NERC, in spite of its raising some
new cybersecurity concerns.
In fact, the NERC report points to security
as another reason for thinking of
the grid more holistically: " The aggregate
impacts of Smart Grid on the distribution
system may impact the reliability of the
bulk power system. Pass-through attacks
from the distribution system may also
present a threat to bulk power system
reliability. "
POWER | April 2011
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POWER April 2011

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