An electrical grid is not a single entity but an aggregate of
multiple networks and multiple power generation companies with multiple
operators employing varying levels of communication and coordination,
most of which is manually controlled. Smart grids increase the
connectivity, automation and coordination between these suppliers,
consumers and networks that perform either long distance transmission or local distribution tasks.
- Transmission networks move electricity in bulk over medium to long distances, are actively managed, and generally operate from 345kV to 800kV over AC and DC lines.
- Local networks traditionally moved power in one direction, "distributing" the bulk power to consumers and businesses via lines operating at 132kV and lower.
This paradigm is changing as businesses and homes begin generating
more wind and solar electricity, enabling them to sell surplus energy
back to their utilities. Modernization is necessary for energy
consumption efficiency, real time management of power flows and to
provide the bi-directional metering
needed to compensate local producers of power. Although transmission
networks are already controlled in real time, many in the US and
European countries are antiquated[26] by world standards, and unable to handle modern challenges such as those posed by the intermittent nature of alternative electricity generation, or continental scale bulk energy transmission.
Modernizes both transmission and distribution
A smart grid is an umbrella term that covers modernization of both the transmission and distribution
grids. The modernization is directed at a disparate set of goals
including facilitating greater competition between providers, enabling
greater use of variable energy sources, establishing the automation and
monitoring capabilities needed for bulk transmission at cross continent
distances, and enabling the use of market forces to drive energy
conservation.
Many smart grid features readily apparent to consumers such as smart meters
serve the energy efficiency goal. The approach is to make it possible
for energy suppliers to charge variable electric rates so that charges
would reflect the large differences in cost of generating electricity
during peak or off peak periods. Such capabilities allow load control switches to control large energy consuming devices such as water heaters so that they consume electricity when it is cheaper to produce.
Peak curtailment/leveling and time of use pricing
To reduce demand during the high cost peak usage periods,
communications and metering technologies inform smart devices in the
home and business when energy demand is high and track how much
electricity is used and when it is used. It also gives utility companies
the ability to reduce consumption by communicating to devices directly
in order to prevent system overloads. An example would be a utility
reducing the usage of a group of electric vehicle charging stations. To
motivate them to cut back use and perform what is called peak curtailment or peak leveling,
prices of electricity are increased during high demand periods, and
decreased during low demand periods. It is thought that consumers and
businesses will tend to consume less during high demand periods if it is
possible for consumers and consumer devices to be aware of the high
price premium for using electricity at peak periods. This could mean
making trade-offs such as cooking dinner at 9 pm instead of 5 pm. When
businesses and consumers see a direct economic benefit of using energy
at off-peak times become more energy efficient, the theory is that they
will include energy cost of operation into their consumer device and
building construction decisions. See Time of day metering and demand response.
According to proponents of smart grid plans, this will reduce the amount of spinning reserve that electric utilities have to keep on stand-by, as the load curve will level itself through a combination of "invisible hand"
free-market capitalism and central control of a large number of devices
by power management services that pay consumers a portion of the peak
power saved by turning their devices off.
Platform for advanced services
As with other industries, use of robust two-way communications,
advanced sensors, and distributed computing technology will improve the
efficiency, reliability and safety of power delivery and use. It also
opens up the potential for entirely new services or improvements on
existing ones, such as fire monitoring and alarms that can shut off
power, make phone calls to emergency services, etc.
US and UK savings estimates and concerns
One United States Department of Energy
study calculated that internal modernization of US grids with smart
grid capabilities would save between 46 and 117 billion dollars over the
next 20 years.
As well as these industrial modernization benefits, smart grid features
could expand energy efficiency beyond the grid into the home by
coordinating low priority home devices such as water heaters so that
their use of power takes advantage of the most desirable energy sources.
Smart grids can also coordinate the production of power from large
numbers of small power producers such as owners of rooftop solar
panels — an arrangement that would otherwise prove problematic for power
systems operators at local utilities.
One important question is whether consumers will act in response to
market signals. In the UK, where consumers have had a choice of supply
company from which to purchase electricity since 1998, almost half have
stayed with their existing supplier, despite the fact that there are
significant differences in the prices offered by a given electricity
supplier. Where consumers switch an estimated 27-38% of consumers are
worse off as a result.
Another concern is that the cost of telecommunications to fully
support smart grids may be prohibitive. A less expensive communication
mechanism is proposed using a form of "dynamic demand management"
where devices shave peaks by shifting their loads in reaction to grid
frequency. Grid frequency could be used to communicate load information
without the need of an additional telecommunication network, but it
would not support economic bargaining or quantification of
contributions.
Although there are specific and proven smart grid technologies in use, smart grid is an aggregate term for a set of related technologies on which a specification
is generally agreed, rather than a name for a specific technology. Some
of the benefits of such a modernized electricity network include the
ability to reduce power consumption at the consumer side during peak
hours, called demand side management; enabling grid connection of distributed generation power (with photovoltaic arrays, small wind turbines, micro hydro, or even combined heat power generators in buildings); incorporating grid energy storage for distributed generation load balancing; and eliminating or containing failures such as widespread power grid cascading failures. The increased efficiency and reliability of the smart grid is expected to save consumers money and help reduce CO2 emissions.
Problem definition
The major driving forces to modernize current power grids can be divided in four, general categories.
- Increasing reliability, efficiency and safety of the power grid.
- Enabling decentralized power generation so homes can be both an energy client and supplier (provide consumers with an interactive tool to manage energy usage, as net metering).
- Flexibility of power consumption at the clients side to allow supplier selection (enables distributed generation, solar, wind, biomass).
- Increase GDP by creating more new, green-collar energy jobs related to renewable energy industry manufacturing, plug-in electric vehicles, solar panel and wind turbine generation, energy conservation construction.
Smart grid functions
Before examining particular technologies, a proposal can be
understood in terms of what it is being required to do. The governments
and utilities funding development of grid modernization have defined the
functions required for smart grids. According to the United States Department of Energy's Modern Grid Initiative report, a modern smart grid must:
- Be able to heal itself
- Motivate consumers to actively participate in operations of the grid
- Resist attack
- Provide higher quality power that will save money wasted from outages
- Accommodate all generation and storage options
- Enable electricity markets to flourish
- Run more efficiently
- Enable higher penetration of intermittent power generation source
- (Source :Wikipedia)
