Energy storage is a vital element
in power sector particularly when a country has large volume of Renewable
Energy (RE). Cheap, practical and easily available energy storage systems can
address some of the critical issues associated with RE sources particularly the
Solar PV systems. It will build an atmosphere of confidence in the Utility
working, particularly utilities with large scale RE penetration; reduce the
investment in transmission systems and development of reserve capacity.
Widespread deployment of battery storage would mitigate the intermittency phenomenon associated with solar PV systems. In fact, in some of the countries utilities have mandated that all new PV systems should have energy storage systems to smoothen the power variations. Solar PV systems with battery storage could also help to manage unplanned voltage fluctuations, particularly in areas with high penetration of solar PV systems.
Widespread deployment of battery storage would mitigate the intermittency phenomenon associated with solar PV systems. In fact, in some of the countries utilities have mandated that all new PV systems should have energy storage systems to smoothen the power variations. Solar PV systems with battery storage could also help to manage unplanned voltage fluctuations, particularly in areas with high penetration of solar PV systems.
Figure 1 shows the main components of a simple Roof
top Solar PV system with Battery back up.
Fig.1: Layout of a simple Roof top Solar PV system with Battery back-up
Example of Energy Storage at the Utility end:
Utilities too have promoted Energy Storage systems at their end. Duke Energy has installed a
hybrid energy storage system comprising of battery bank and ultra-capacitor at
its North Carolina based substation (www.technologyreview.com).
In this hybrid storage system, the ultra-capacitor helps the power system
during large but short duration power surges, for example when the Solar output
dips during a cloudy day. Battery bank, as customary, will help to recover during
large duration shortages.
It is expected that the two storage systems along with smart electronic controls will help the power system in mitigating the power shortage over periods ranging from seconds to several hours. This hybrid storage is supposed to provide a more economical solution as compared to each of the storage systems when used separately.
It is expected that the two storage systems along with smart electronic controls will help the power system in mitigating the power shortage over periods ranging from seconds to several hours. This hybrid storage is supposed to provide a more economical solution as compared to each of the storage systems when used separately.
According to officials at Maxwell
Technologies, the ultra-capacitor storage system can completely eliminate the
output fluctuation of less than 30 seconds and provide sufficient smoothening
of fluctuations of up to 5 minutes. In recent years the ultra-capacitor energy
storage systems have become more accepted as high power shock absorbers for
industrial and transportation applications in combination with Lead-acid
batteries or advanced chemical batteries. Ultra-capacitor has high power
capability due to very low internal resistance, wide operating temperature
range of -40oC to 65oC, minimum maintenance, high cycling
ability and reasonable price.
The latest utility scale battery storage technology emerged in the commercial market is the 8 MWh capacity Vanadium Redox Battery bank installed at Everett Sub-station, Washington state, and which is to be commissioned in January 2017. This battery system, compact and concealed in container, is non-flammable and can be discharged upto 100%, i.e. the Depth of Discharge (DoD) can be 100%.
The latest utility scale battery storage technology emerged in the commercial market is the 8 MWh capacity Vanadium Redox Battery bank installed at Everett Sub-station, Washington state, and which is to be commissioned in January 2017. This battery system, compact and concealed in container, is non-flammable and can be discharged upto 100%, i.e. the Depth of Discharge (DoD) can be 100%.
Essence of Energy Storage to End User:
At the end user level the energy
storage system will provide the user with the much needed back up during night
hours when the grid is out. In countries like India the Time-of-Day (TOD)
tariff is not implemented in the residential and commercial sector. I am sure
that in the near future Utilities have to come up with the TOD tariff in these
sectors also. Then in such a case a solar PV system with energy storage will be very beneficial.
TOD tariff is an effective tool to reduce the peak hour kWh shortage. Shifting of some portion of the load to the storage system will be of great relief to the utilities reeling under stress.
TOD tariff is an effective tool to reduce the peak hour kWh shortage. Shifting of some portion of the load to the storage system will be of great relief to the utilities reeling under stress.
Fig 2: A Roof Top Solar PV system with battery back-up.
In some countries, the
feed-in-tariff has been rigorously cut down or eliminated at all. In such a
condition, the pay back periods of solar PV systems are highly dependent on the
percentage of solar energy used for “self-consumption”.
Energy storage systems enable owners of solar PV systems to increase their self-consumption. Although installing energy storage system increases the overall cost of the system and hence the electricity produced, but still it is not as expensive as many would think of. Lithium-ion batteries are considered as the most affordable and dependable energy storage systems. These batteries can discharge bigger burst of power and can eliminate the need of ultra-capacitor but are costly.
"Experts are in the opinion that a solar PV system is worth only if the self-consumption is about 50% or more."
Energy storage systems enable owners of solar PV systems to increase their self-consumption. Although installing energy storage system increases the overall cost of the system and hence the electricity produced, but still it is not as expensive as many would think of. Lithium-ion batteries are considered as the most affordable and dependable energy storage systems. These batteries can discharge bigger burst of power and can eliminate the need of ultra-capacitor but are costly.
