Page 353 - Renewable Energy Devices and System with Simulations in MATLAB and ANSYS

340 Renewable Energy Devices and Systems with Simulations in MATLAB and ANSYS ®
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Load leveling and peak shaving are possible by following the load profile and controlling EESs to match
the required energy. EESs can also provide spinning reserve and backup power supply, which could be
utilized in sudden events, such as momentary outages or ride-through transients.

13.6.2 Energy Time Shifting
Typically, there is a mismatch between the generation of energy and the demand in peak hours. Time
shifting of energy delivery is a unique benefit from ESSs, which enables the utilities to absorb excess
energy in off-peak hours by charging the ESS and release it during peak hours of high demand by dis-
charging the storage. Functional and economical benefits, related to different higher on-peak and lower
off-peak tariffs, can be achieved in this manner. Without ESSs, the traditional approach is to provide
additional and costly generation capacity able to cover up to the maximum possible load demand.
The arbitrage over time or the time-shifting technique can also be used for renewable energy
generation plants, in which case the harvested energy can be stored during off-peak demand and
made available during peak time.

13.6.3 Capacity Credit
Capacity credit for ESSs allows electrical utilities to defer the installation and upgrade for exis-
tent generation or transmission infrastructures. Since expansions for power plants, power lines, and
transformers, which may be required in order to meet expected demand, are very time-consuming
and costly, electrical utilities can take the advantage of the extra capacity provided by ESSs in order
to satisfy the demand and reduce the load shedding caused by an inability of the electrical utility to
provide adequate capacity.

13.6.4 Renewable Energy Integration
Due to the intermittent nature of renewable energy sources, which are highly affected by geological,
time, and weather conditions, their output power may fluctuate unpredictably and may not meet the
quality required in order to directly connect to the electrical grid. In this case, ESSs can provide smooth-
ening services, such that the intermittent output power from renewable energy sources is adjusted, and
fluctuations mitigated, as schematically illustrated in Figures 13.28 and 13.29 [96, 97].

Wind output
power Output
power

PM or AC/DC DC/AC
induction converter converter
generator
Utility
transformer Utility grid
Energy storage
output power DC/DC Energy
converter storage

FIGURE 13.28 Block diagram of a wind turbine with battery integrated at turbine level. (Based on the con-
cept proposed in Esmaili, A. and Nasiri, A., Proceedings of IEEE Energy Conversion Congress and Exposition
(ECCE), pp. 3735–3740, 2012.)