Page 165 - Hybrid-Renewable Energy Systems in Microgrids

Renewable systems and energy storages for hybrid systems 149

peak demand. Hence, this mismatch of energy may lead to power spillage and losses. Using
ESS, this mismatched energy can be shifted to satisfy the peak demand and level the load
curve. Load curve leveling can also be approached from the consumer side by educating
the consumers on energy efficiency, demand response programs, and energy utilization and
conservation using ESS.
3. Integration of renewable sources in DG: ESS can be used to even out the irregularities in
renewable power. European countries with high solar penetration have been observing a
phenomenon called duck curve in their power curve. It occurs when in the evening entire
solar power goes down and evening peak comes in immediately, and it proved to be chal-
lenging for the grid operators to ramp up generation to increasing demand. Such cases can be
avoided by implementing ESS to level the duck curve. Also as mentioned before, ESS can
effectively even out the variability of renewable power. Storing generated power at times of
low energy demand and then discharging back to the grid enables effective usage of renew-
able power and elimination of backup peaking diesel generators.
4. Power quality support: ESS can also be used to implement power quality improvement like
in low voltage ride through and voltage regulation. The ESS used need to have high power
densities and short response times like flywheels and supercapacitors (SC). They will be
required to keep the power voltage and frequency fluctuations within limits.
5. Smart homes: Residential ESS play a major role in realization of smart homes and energy
sustainable buildings. A smart energy management system will be able to manage the en-
ergy storage and consumption and also provide accurate data on power utilized and sub-
sequent emissions. These will be like perfect benchmarkers for efficient energy usage and
climate control.
6. Electric vehicles: Electric vehicles, both plug in and hybrid varieties, will be a major
game changer in future grid infrastructures. ESS for electric vehicles are being developed
and promoted in a rapid pace and with decline in battery prices, this will be most wel-
come. The entire electric vehicle sector itself can act as a large ESS feeding back power
to the grid when operated with proper planning and scheduling. The significant feature for
an ESS in vehicles is to provide the starting power and competitive mileage. Hence batter-
ies of one or more types can be grouped in the form of hybrid ESS to deliver the required
power/energy [8].
7. Smart grid: Smart grids have become prominent to ensure efficient energy transmission and
distribution from multiple supply points pumping out fluctuating and intermittent power.
Future prosumers like smart houses and electric cars which will act as both producers and
consumers of electricity will be major participants of smart grids to prevent network over-
loads by regulating and controlling the fluctuating powers [9].
8. Long-term storage: Dams and reservoirs have been used to save water for generating power
from olden times. More types of thermal and air storage systems have been conceptualized
recently so as to store electric energy in huge capacities. They prove to bring down the cost
of saving energy and in ensuring storage of energy for longer period of time say from days
to a few months [7].
9. Ancillary services: Ancillary services are those which are needed by the grid operators
to sustain stable and reliable operation of the grid. Frequency regulation, energy arbi-
trage, and load following can also be implemented with ESS. Energy arbitrage involves
reaping of profits by saving energy under low energy demand period and delivering
back at high demand periods. It goes hand in hand with peak shaving concept but fo-
cuses on commercializing the saved energy for maximum profit. ESS needed for these
ancillary services need to be very responsive so that the profit costs could be enough to
justify investments.