What exactly is a ‘Smart’ Grid?
There is a lot of talk on how smart grids are needed to solve intermittency in power generation introduced by renewable sources of energy. But what does a smart grid mean?
An excellent paper from Carnegie Mellon University titled The Many Meanings of Smart Grid sums up the different aspects.
At the level of the customer:
1) Meters that can be read automatically without sending someone to read it once a month. This saves cost and eliminates errors in meter reading.
2) Time-of-day and time-of-use meters: Time-of-day meters charge different rates at different times during the day (This is because demand is higher during certain periods than others). Time-of-use meters are real-time meters which reflect spot prices of electricity. Both technologies are intended to reduce peak loads so as to ensure that less generation and transmission capacity is needed.
3) Meters which communicate to the consumer through a display providing information about the current rate of electricity use and the price. This promotes energy conservation and a reduced demand during times of peak prices.
4) Load management: Meters that are intelligent enough to avoid turning on appliances during times of high prices of electricity. For example, scheduling your washing machine to operate at night, when prices are typically the lowest.
At the level of the distribution system:
1) Distribution system automation: Most distribution systems have a tree like structure known as Distribution Feeders . This means that if the main feeder is damaged due to lightning, the entire network goes down. A smart grid would, however, be able to route power through an alternate feeder to avoid disruptions.
2) Selective load control: Today, if there is an emergency (storm, terrorist attack, etc.) and the demand outstrips supply, then entire sections of the distribution network will have to be disconnected to reduce the demand. With a smart grid, this can be better managed to ensure that critical services like fire services, hospitals and police stations remain functional.
3) Managing distributed generation and islanding: Distributed energy sources (from renewable energy for example) that supply power to a certain geographical area should be given the flexibility to cut themselves off from the main grid in case of an emergency. The current set up does not allow this.
At the transmission system:
1) Measurements and monitoring: Smart grids allow for better monitoring of the entire system thanks to the host of sensors and computing integrated with the transmission system. This can promote efficiency, avert breakdowns and reduce the time taken to detect a problem.
2) Routing of power: Routing of power follows the laws of physics and not economics. Sometimes power flows where it is not wanted which leads to a waste. Smart grids can deal with better routing of power through advanced switching devices.
3) Distributed and autonomous control Today s grid is controlled centrally. Research shows that this may not be the most efficient manner to deal with emergency situations due to the differences in grid requirements in different areas (known as grid topology). Smart grids will allow decentralization of control.
As India s policy makers strive to establish standards for smart grids , there is a need for an understanding of the definition of Smart Grids which would serve as the foundation in bringing different stakeholders to a common platform.
[The paper can be downloaded from: http://wpweb2.tepper.cmu.edu/ceic/pdfs_other/Smart_Grid_July_09.pdf]