IEEE Power & Energy Magazine - January/February 2017 - 41
The adoption of end-use energy and water conservation methods
by the business and residential sectors would reduce imbedded
energy and water requirements.
It has been estimated that an electric energy savings
potential of 5-10% across the U.S. public water supply can
be achieved with advances in pumping and water treatment
process control. Assuming the public water supply currently
uses about 39 billion kWh per year, the potential electric
energy savings associated with advanced SCADA systems
ranges from 2.0 to 3.9 TWh per year. This translates into
electricity savings ranging 5.4-10.9 million kWh per day
across the United States. One such energy-saving technique
is to use a SCADA system for automatically selecting the
best pump combination, reducing system pressure when possible, checking the system efficiency in real time, and then
notifying the operator when changes are required.
The most sophisticated control systems "learn" the characteristics of the distribution system, relying on predictive
modules to assist in scheduling pumping. This option is
extremely valuable in systems where the pump station takes
advantage of time-of-day electric rate schedules.
Efficiency via Water Conservation
Water conservation is an overlooked challenge as an energyefficiency measure in both water treatment and WWT.
Lowering water demand reduces the volume of water drawn
from public water supplies; this, in turn, reduces the energy
required to pump and treat the water supplied to end users.
A lower demand for fresh water also translates directly into a
reduced demand for wastewater transport and treatment and
a corresponding reduction in energy used.
There are two main challenges for water conservation
in water supply and wastewater disposal. On the water supply side, the opportunity lies in detecting and eliminating
leaks in the supply system. On the wastewater side, inflow
and infiltration lead to significant increases in flow to the
treatment facility, particularly during rain events. The additional volume of inflow water combines with wastewater
effluent and increases the amount of wastewater that must be
pumped and treated.
Reducing Demand for Water in End Uses
Considerable opportunities exist for reducing fresh water
demand for landscape irrigation. Based on U.S. Environmental Protection Agency and U.S. Bureau of Reclamation
data, the potential savings from advanced irrigation controls in residential and commercial applications is estimated
to be 1.5-3% of total electricity use in the public water supply. At a current electricity use rate of 39,000 million kWh
per year, this equates to potential savings of 0.5-1.2 TWh
january/february 2017
per year in the public water supply. While this is not a small
number, the nature of the savings through numerous, small
actions makes the impact of this measure extremely challenging to measure.
Providing timely information on usage patterns has
proven to be an effective way to increase awareness and
transform consumer behavior in both the energy and
water industries. There is a substantial opportunity to
modify consumer behavior and detect leaks by providing
a greater degree of visibility into use patterns. An example is energy savings due to reducing hot-water demands
with low-flow devices.
Energy Recovery and Generation
A new and growing trend in the water and wastewater industry is the emphasis on recovering energy whenever possible.
In water treatment, the focus is on recovering some of the
pumping energy through the use of energy-recovery devices
in the distribution system. In WWT, the emphasis is on biological treatments combined with opportunities in capturing
energy in the wastewater itself. These include cogeneration
using digester biogas and the recovery of excess line pressure
to produce electricity (microhydro).
Advanced Technologies in Water
Treatment for Energy Efficiency
There are significant growth opportunities in advanced
technologies in water treatment and WWT spurred mainly
by drivers associated with water scarcity and the need to
meet stricter discharge limits. However, many of these processes-including, for example, reverse osmosis for desalination, advanced ionization for micro-pollutant removal,
and membrane bioreactors-are expected to continue to
be highly energy intensive. Some emerging developments
to address this problem include forward osmosis or membrane distillation using low-grade waste heat. Another
significant opportunity is to couple desalination with
renewable-energy systems. Energy efficiency can also be
improved through the integration of space-conditioning
and water-heating systems. For residential and commercial building applications, newer systems are under development that use waste heat from outdoor air-conditioning
compressor units to heat water. Research is underway to
determine the overall efficiency of such systems. This
technology is fairly mature in the industrial sector, where
heat pumps are used recover heat from industrial processes
to heat-process water.
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Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - January/February 2017
IEEE Power & Energy Magazine - January/February 2017 - Cover1
IEEE Power & Energy Magazine - January/February 2017 - Cover2
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IEEE Power & Energy Magazine - January/February 2017 - Cover3
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