IEEE Power & Energy Magazine - January/February 2017 - 36

Today's electric grid has become the integrated energy network,
which requires versatility across power paths and adapting to the
new energy end user, called a prosumer.
Smart grids are characterized by connectivity, flexibility, and resiliency, all of which effectively optimize their
efficiency, reliability, security, economics, and environmental performance. Numerous system integration technologies are emerging today that promote these smart features.
Energy systems integration (ESI)-a multidisciplinary
area ranging from science, engineering, and technology to
policy-making, economics, regulation, and human behavior-is coming to the fore in the planning, design, and operation of the global energy system. ESI seeks to optimize
the energy system and other large-scale infrastructures-in
particular, water-by leveraging synergies across all scales
and pathways.
Evaluating an integrated energy network allows us
to address efficiency with a triple bottom line: financial,
environmental, and social impacts. In other words, the system's optimization will be driven by a primary target with
consideration given to secondary impacts. The primary or
secondary targets might include greenhouse gas emissions,

Ecosystem
Demand

Electric Power

Agricultural

Industrial

Municipal

figure 2. Resource management has become more
intricately integrated, specifically for water and energy
resources. Although not as obvious as energy consumption, water usage covers a variety of applications, from
power generation and industrial and agricultural applications to municipal needs with water treatment/WWT, and
also includes the goal of sustaining of natural ecosystems.
(Image courtesy of the Electric Power Research Institute.)
36

ieee power & energy magazine

power-load profiles, water conservation metrics, and the
population density served, among others. Deciding which
are the primary or secondary targets depends on the driving or pressing factors. Utilities, municipalities, and building
and facility operators may reap the benefits of the integration
of water and energy networks with the triple bottom line.
The examples that follow here demonstrate the emerging
integration of the water network and energy grids, particularly in the WWT part of the water sector and the end-use
part of the electric grid. Specifically, for both the water and
energy sectors, these examples highlight demand response
(DR) opportunities, energy-efficient technologies, and the
important role that reconceptualizing WWT plants can play
as part of future energy systems in terms of virtual storage
and as resource factories.

Demand Response
DR, as defined by the U.S. Federal Energy Regulatory Commission, refers to changes in electric usage by end-use customers "from their normal consumption patterns in response
to changes in the price of electricity over time, or to incentive
payments designed to induce lower electricity use at times of
high wholesale market prices or when system reliability is
jeopardized." This implies the shedding of some loads when
the electric system reaches critical peaks and loads cannot
be served by existing generation plants (Figure 3). Because
water treatment and conveyance require large amounts of
energy, the potential exists for large DR capabilities in these
sectors. Examples of DR implementation include
✔✔ agricultural irrigation DR signaling so that pumps
operate when electricity demand and associated rates
are low
✔✔ pumping to head tanks at off-peak hours
✔✔ off-peak water treatment
✔ ✔ flexible load management and energy storage in
water heaters.
Water treatment and WWT facilities are good candidates
for DR because they are energy intensive. In some cases, a
water storage capability could offer some flexibility in the
operation of certain processes, including pumps and centrifuges. This operational flexibility, in turn, can be leveraged
for DR if properly coordinated, making these facilities ideal
partners for electric utilities seeking to manage electric load
through DR programs. Furthermore, water storage can be
used in conjunction with on-site power generation to provide
greater demand reduction. For example, water storage can
be used to shave power requirements at high electricity load
january/february 2017

Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - January/February 2017