IEC_Elctrical Energy Storage.pdf

Some utilities generation cost can be reduced by

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some utilities generation cost can be reduced by storing electricity at off-peak times, for example at night, and discharging it at peak times. If the gap in demand between peak and off-peak is large, the benefit of storing electricity becomes even larger. Using storage to decrease the gap between daytime and night-time may allow generation output to become flatter, which leads to an improvement in operating efficiency and cost reduction in fuel. For these reasons many utilities have constructed pumped hydro, and have recently begun installing large-scale batteries at substations. 2) Power quality A basic service that must be provided by power utilities is to keep supply power voltage and frequency within tolerance, which they can do by adjusting supply to changing demand. Frequency is controlled by adjusting the output of power generators; EES can provide frequency control functions. Voltage is generally controlled by taps of transformers, and reactive power with phase modifiers. EES located at the end of a heavily loaded line may improve voltage drops by discharging electricity and reduce voltage rises by charging electricity. 0,1 s 1 s 15 s 1 min 15 min 1 h 8 h 1 / month 1 / day 12 / day 30 / h 30 / min 5 / sec Duration Number of uses Electricity supply reserve Timeshift Primary Regulation Power Quality Figure 1-3 – Different uses of electrical energy storage in grids, depending on the frequency and duration of use [eus06]
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S E C T I O N 1 The roles of electrical energy storage technologies in electricity use 16 3) Making more efficient use of the network In a power network, congestion may occur when transmission/distribution lines cannot be reinforced in time to meet increasing power demand. In this case, large-scale batteries installed at appropriate substations may mitigate the congestion and thus help utilities to postpone or suspend the reinforcement of the network. 4) Isolated grids Where a utility company supplies electricity within a small, isolated power network, for example on an island, the power output from small-capacity generators such as diesel and renewable energy must match the power demand. By installing EES the utility can supply stable power to consumers. 5) Emergency power supply for protection and control equipment A reliable power supply for protection and control is very important in power utilities. Many batteries are used as an emergency power supply in case of outage. 1.4.2 The roles from the viewpoint of consumers 1) Time shifting/cost savings Power utilities may set time-varying electricity prices, a lower price at night and a higher one during the day, to give consumers an incentive to flatten electricity load. Consumers may then reduce their electricity costs by using EES to reduce peak power needed from the grid during the day and to buy the needed electricity at off- peak times.
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