Environmental Engineering Reference
In-Depth Information
From the substation, electricity is distributed locally within a community to individual
buildings and homes. The voltage is generally further reduced at the point of use to the
standard voltage of that region, which varies in different countries (with most customers
getting 110-20 V in the United States and 220-40 V in Europe) and with electricity
use requirements. Electricity losses from transmission and distribution are estimated to
efficiency by decreasing losses in transmission and distribution is high.
The use of electricity varies among different kinds of electricity consumers: industrial,
commercial, or residential (
Chapter 4
details different types of consumers). Demand for
electricity varies over time, over the course of a day, seasonally, and annually. It is driven
by consumer behavior, weather, and larger economic trends. In a typical 24-hour period,
electricity demand peaks in the afternoon and early evening hours and is at its lowest in the
middle of the night. Seasonal variation in electricity use is dependent on variability in the
type of heating and cooling requirements of different building in different places. In many
buildings, air conditioning during the summer makes this the most energy-intensive time
of year. In the United States, Canada, and most EU countries, overall annual electricity
demand has not been rapidly growing but has been relatively stable, although how energy
is used is shifting. In general consumers are using more energy in appliances, electronics,
and lighting than they did twenty years ago, powering more devices, including computers,
electric toothbrushes, and smartphones.
3.2.4 Challenges Within Legacy Systems
One of the major limitations resulting in inefficiencies in legacy systems is the challenge
of storing electricity. It is currently very expensive to store electricity; large, expensive
batteries limit the feasibility of storing significant amounts of electricity. Given this limited
capacity for electricity storage, electricity systems need to be managed and controlled to
constantly strive for real-time balancing of electricity generation and electricity demand.
To ensure reliability, electricity systems assume a certain level of redundancy, and they are
managed with a goal of supply capacity exceeding demand at all times. These capacity
margins range from 10 to 20 percent. Electricity generation must match electricity use.
If and when demand exceeds supply, rolling brownouts or disruptive power outages can
occur. Power outages can trigger many different kinds of local disruptions, but they
can also sometimes lead to systemwide destabilization that can result in larger regional
blackouts. The Northeast United States blackout of 2003 is an example of systemwide
destabilization triggered by a localized area of demand exceeding supply. When operators
did not redistribute power as needed after an alarm system in an Ohio control room failed
to notify them of a localized disruption, cascading systemwide impacts ensued, causing
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