Sioshansi F.P. Smart Grid: Integrating Renewable, Distributed & Efficient Energy
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Figure 8.4
Size of existing microgrid installations.
Future Evolution of Microgrids
Considering the deployments detailed in the previous section,
there is ample evidence that microgrids are being constructed
across a range of sizes, with a diversity of generation,
integration with loads, and interactivity with the grid. That
said, microgrids are not yet the smart-grid stepping stone that
their proponents would suggest.
While the size range of currently installed microgrids
suggests that such systems have a place in a variety of grid
deployments—from remote islanded communities to major
grid-connected urban developments—the reality is that very
few of these systems are operating in any particularly
sophisticated manner.
Very few of the microgrids in Table 8.3 are able to operate in
both islanded and grid-connected modes, likely due to the
complexities (and expense) associated with switching
between these two operating states. As discussed earlier,
managing control of the microgrid when grid connected is
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quite different from managing control of the microgrid when
operating in island mode. Further, at this stage, the fast
switches required to allow smooth transfer between islanded
and grid-connected mode are relatively uncommon and quite
expensive.
Additionally, very few of the microgrids in Table 8.3 have
any particularly sophisticated integration of load with supply
in the microgrid. Where such integration does exist, it is often
relatively simple, with simple load prioritization tables used
to schedule a fixed priority list of loads so that total demand is
matched to total supply. As discussed earlier in this chapter,
for more optimal performance, such systems need to operate
dynamically, respecting the changing priorities of loads. They
will need to forecast future demand and also the future
generation available to meet that demand, and with this
information at hand, proactively plan how to match
generation and supply.
While currently built microgrids have much potential to still
be realized, we can remain positive that the issues raised in
the preceding paragraphs are the subject of a growing amount
of research. That said, while quite sophisticated control
techniques are now being demonstrated, further research is
needed to reduce costs and improve the simplicity of
installation and operation. Ultimately, the sophisticated
microgrid control schemes being demonstrated in the research
space must move from the “bleeding edge” to reliable and
dependable commercial products.
Lastly, aside from improvements internal to microgrid
operation, at this stage there are few examples of electricity
utilities themselves using microgrids as the beneficial asset
they might be. While a number of the microgrid deployments
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in Table 8.3 have had utility involvement, often these are
islanded systems, and the microgrid is not seen by the utility
as a wider macro-grid asset. Although the Utsira microgrid in
Norway [31] and the Ausgrid Smart Grid Smart City project
in Australia [32] are early exemplars of utilities considering
how microgrid could be an asset to wider operations, we need
further detailed results data, and more deployment examples,
before utilities will genuinely see this technology as a true
stepping stone to the smart grid.
Conclusions
While microgrids were once considered a technology limited
to remote area power supplies, they now offer a transitionary
path from the utility grid operations of today to the intelligent,
dynamicm and flexible smart grids of tomorrow. By
aggregating large numbers of generators, loads, and storage
devices together so they appear to the utility grid as a single
controllable asset, microgrids ease the burden of control for
the utility grid, simplifying issues such as the integration of
large numbers of renewable energy devices, or managing
system operation when given a complex multitude of control
devices and constraints.
Microgrids also offer significant benefits to the end-user,
helping to isolate them from utility grid issues, manage
multiple on-site loads and generators, or improve local power
quality. Microgrids are not without their challenges however,
with a variety of issues challenging the early adopters of this
technology, and limiting the number of deployments of this
technology in developed electricity networks.
These challenges are being addressed by a growing number of
researchers and system developers worldwide. While many of
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today's microgrid installations remain relatively simple, there
are a growing number of microgrids being built with an
increasing variety of generation types, integration of load and
generators, and control systems that interact dynamically with
the wider utility grid. These systems are a shining exemplar
of the very near future, where microgrid technologies will be
relied on as our first major stepping-stone towards the grid of
the future.
Acknowledgment
This work was supported by funding from the Australian
government as part of the Asia Pacific Partnership on Clean
Development and Climate.
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Chapter 9. Renewables Integration Through
Direct Load Control and Demand Response
Theodore Hesser and Samir Succar
Chapter Outline
Introduction 209
Integrating Temporally Variable and Geographically
Heterogeneous Resources 211
Demand Response: Past, Present, and Future 213
Ancillary Services 216
Regulation Services 217
Load Following 218
Contingency Reserves 219
Wind Integration Cost 220
Demand Response Resource Topology 221
Demand Response Potential Assessment 224
Wind Integration and Demand Response 228
Conclusions 231
Acronyms 231
References 232
The challenge of effectively integrating renewables sits front and center on the mind of utility
executives, public utility commissioners, and independent system operators Dispatchable demand
response (DR) offers a relatively cheap and fast-acting solution to the reliability concerns posed by
increasing renewable penetrations These reliability concerns will be exacerbated in a few balancing
pools due to heterogeneous distributions of variable energy resources (VERs) Direct load control
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