SUPERCONDUCTING MAGNETIC ENERGY STORAGE

SYSTEM

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PRESENTED BY:ROSHNI ABHISIKA Regd.No :1241019016EICE ‘A’

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INTRODUCTION

RENEWABLE energy sources will have a key role in supplying energy in the future.

There are several issues regarding large scale integration of new renewable into the

power system. One of the problems is the security of supply. These energy sources will

provide energy, or not provide, independent of the demand. The output power can also

have relatively large variations within a short time span. A solution to this problem is the

concept of energy storage, and there are several different concepts. There are devices

which can store large amounts of energy, but do not react so fast. In the other end there

are fast acting devices which store smaller amounts of energy. Superconducting

Magnetic Energy Storage (SMES) is placed in this group.

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SMES SYSTEM• Superconducting Magnetic Energy Storage (SMES) is an energy storage system that stores energy in the form of dc electricity by passing current through the superconductor and stores the energy in the form of a dc magnetic field. [2]

• The conductor for carrying the current operates at cryogenic temperature where it becomes superconductor and thus has virtually no resistive losses as it produces the magnetic field.

• The magnetic field is created by flow of direct current through the coil.

• SMES systems are highly efficient; the efficiency is greater than 98%.

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Components of SMES system Superconducting coil with the magnet

The power conditioning system (PCS)

The cryogenic system

The control unit

FIG NO:1Image courtesy: google image

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SMES SYSTEM

FIG NO:2Image courtesy: ref [3]

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Superconducting Coil Main part of a SMES system

Most superconducting coils are wound using conductors which are comprised of many

fine filaments of a niobium-titanium (NbTi) alloy embedded in a copper matrix. [1]

The Size of the coil depends

upon the energy storage require-

ment .

FIG NO:3Image courtesy: google image

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Power Conditioning SystemThe power conditioning system uses an  inverter/ rectifier to

transform alternating current (AC) power to direct current or

convert DC back to AC power.

An ac/dc PCS is used for two purposes:

• One is to convert electric energy from dc to ac.

• The other is to charge and discharge the coil.

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Cryogenic UnitThe SMES coil must be maintained at a temperature sufficiently low to maintain a superconducting state. Commercial SMES temperature is about 4.5 K.

It uses helium as the coolant or liquid nitrogen.

The refrigerator consists of one or more compressors called a “cold-box”. It affect the overall efficiency and cost of SMES system.

FIG NO:4Image courtesy : ref [2]

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Control system Establishes a link between power demands from the grid and power flow to and from the SMES coil. [3]

Receives dispatch signals from the power grid and status of the coil.

Maintains system safety and sends system status information to the operator.

Modern systems are tied to the internet to provide remote observation and control.

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OPERATION OF SMES There are three different modes of operations of the SMES coil :-

• Charging mode• Stand-by/ freewheeling mode• Discharging mode

ASSUMPTIONS

GTO is in ON state means that the duty cycle of that GTO is 1. GTO is in OFF state means that the duty cycle of that GTO is 0

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CHARGING MODEGTO2 is always in the ON state. In charging mode GTO1 is also in the ON state.When SMES is charging,

Vsmes is the voltage across SMES coil D is the duty cycle V dc is the voltage across the dc link capacitor

It takes about 3 sec to charge the coil to its rated current capacity. The current rises through the SMES coil and the voltage across the SMES is captured.

Vsmes = D * VDC

FIG NO:5Image courtesy:ref [1]

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FREEWHEELING MODEThis is the second mode of operation.Here the current circulates in a closed loop. In this mode, any one of the GTO’s is OFF.There is no significant amount of loss here, as the current through the SMES coil is circulating in a closed loop.

Hence, current remains fairly constant in this mode of operations

FIG NO:6Image courtesy: ref[1]

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DISCHARGING MODEThe current in the SMES coil discharges into the dc link capacitor in this

mode of operation.GTO2 is always OFF.Duty cycle of GTO1 can be varied as per the discharge rates.The voltage relationship between SMES coil and the dc link capacitor during this mode is:-

-Vsmes = (1-D) * VDC

FIG NO:7Image courtesy: ref[1]

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APPLICATIONS OF SMESPaper industryMotor vehicle assemblyPetrochemical RefineriesChemical & pharmaceutical Companies

FIG NO:8Image courtesy: google image

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Advantages of SMES SMES systems have the ability of fast response.

They can switch from charge to discharge state (vice versa) within seconds.

The absence of moving parts and high efficiency are some additional advantages.

It can be deployed in places where other technologies such as battery system or compressed air are not feasible.

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Common ChallengesMain drawback of the SMES technology is the need of large amount power

to keep the coil at low temperature, combined with the high overall cost for the employment of such unit.

To achieve commercially useful levels of storage, around 1 GW.h a SMES installation would need a loop of around 100 miles (160 km).

Another problem is the infrastructure required for an installation.

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Market Analysis It has been estimated that, the total cost to the US businesses of the lost

productivity is a staggering $15-30 billion per year. It is estimated that, over 100 MW of SMES units are now operating in

worldwide.The global market for SMES is projected to reach US$64 million by 2020.At the larger scale, the projected development of a 100 MWh load leveling

system could be implemented during 2020-30.

FIG NO

:9Im

age courtesy: ref[2]

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CONCLUSIONWith the advancement in the science of superconductor technology , cost of

installation of the SMES system is eventually going to be comparable to that of

the existing storage technologies.

Hence, it will promote this system which is capable of discharging larger amount

of energy for short period of time thus helping with dynamic performance.

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REFERENCES[1] D.S.Padimiti, B.H. Choudhury, “Super conducting magnetic energy storage system for improved dynamic system performance,” IEEE Trans. Power. del. Vol.25, no.3, pp.1816-1827, Jun.2010.

[2] Z. Wang, Z. Zou, Yang Zheng, “Design and control of a photovoltaic energy and SMES hybrid with current source grid inverter,” IEEE Trans. Appl. supercond. Vol.2, no.3, pp.254-253, Jun.2013.

[3] R.M. Vamsee, D.S. Bankar, “Control of system under normal grid condition,” IEEE Trans. Power. electron. Vol.22, no.2, pp.587-594, mar.2011.

[4] C.A. Luongo, “Superconducting storage systems: An overview,” IEEE Transaction on magnetics, Vol.32, Issue4, Part 1,pp. 2214-2223, Jul.1996.

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