Analysis of Flywheel Energy Storage Devices

The provided document is a solved assignment on the analysis of flywheel energy storage devices. It discusses the characteristics and benefits of flywheels, including their ability to store mechanical energy, convert active energy into electrical energy, and provide high power quality due to being DC-based. The document also mentions the variation in energy demand from this type of device, which remains constant, and its potential use in domestic energy supply.

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ELECTRICAL POWER
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Question three
High Voltage Direct Current has some comparison with the High Voltage Alternating Current is
basically done by the use of the advantages and disadvantages as seen in the analysis below;
Advantages of HVDC over HVAC
i. There is reduced cost of transmission since there are only two cables used for
transmission as compared to three or four cables of transmission used in HVAC
ii. Transmission losses are highly reduced since there is no reactive power in HVDC.
iii. Because of high transmission voltage, in the same power the current is less, therefore
the power loss due to I2R is very small (Baggini, 2012).
iv. When there are faults, power levels in HVDC system can be easily be managed
electronically
v. HVAC has skin effect which is lacking in the HVDC
vi. The cost of installation is very small as compared to HVAC since there are only two
cables required for the HVDC
vii. HVDC is preferred in power transmission via cables because it needs no reactive
power and no charging current.
viii. It is possible to connect two AC systems with different frequencies using HVDC
transmission line and this is not possible in HVAC.
Disadvantages of HVDC over HVAC
i. It is very complex to operate and design multi-terminal HVDC system as compared
to AC systems.
ii. Power faults always occur on the inverter output side in the HVDC transmission
system.
iii. It is very difficult and very complex to ground the Dc power transmitted through
HVDC.
iv. There is radio noise which is caused by high-frequency constituents present in DC
transmission systems (Bany, 2012).

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v. There is the high cost of inverting and converting components needed for the HVDC
transmission, therefore, it is uneconomical.
vi. There is high installation cost due to the additional filters needed in various stages of
HVDC transmission systems (Chai, 2012).
vii. The movement of current via the ground in monopole systems can lead to
the electro-corrosion of underground metal installations, especially in
pipelines
Question four
Power quality is in many cases defined as the ability of the electrical grid to supply a very stable
and a clean power flow as a perfect power is constantly present and has a pure noise-free sine
wave shape, and is continually within frequency tolerance and voltage (Baggini, 2012). But in
most cases, there are some power quality parameters. And these power quality parameters
include the following;
i. Harmonic
ii. Reactive power
iii. Flicker
iv. Transients
v. Voltage variation
vi. Oscillation
vii. Network unbalance
These parameters result in excessive losses and disturbances in the power quality.
i. Harmonic
Several supplies of frequency, for example, the fifth harmonic may be about 250 Hz when the
supply frequency is 50 Hz which is caused by power electronic loads like undisputable power
supply (UPS) and variable power supply (Cheesbrough, 2013). The pollution caused by the
harmonic creates extra stress on the network and ensures installation run less efficacy

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(Sengupta, 2012). The pollution due to harmonic is always characterized by the THD (total
harmonic disturbance). And this THD is the same to the ratio of the RMS harmonic content to
the fundamental (Gu, 2016).
THDV = √VRMS2−V 12
V 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1
The equation 1 above can be simplified further to equation 2 as seen below
THDV= √ ∑ K −2 Vk2
V 1
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Historically passive filters are being suggested to help mitigate this pollution of harmonic.
While the active filter which is based on the power electronics mitigation in low voltage uses
(Loughran, 2013). This can be illustrated in the diagram below;
Fig 1: Showing the harmonic pollution (Sengupta, 2012)
As a whole, minor frequency harmonics are highly severe than a higher frequency, since there is
more energy in the lower frequencies than in higher frequency (Lucas, 2012).

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Nevertheless, high harmonic distortion may result in glitches with control equipment and
communication.
ii. Reactive power
The phase angle which is in between the voltage and current waveform in an alternating Current
system employed to create magnetic field motors which result to lower power factor (Pasko,
2014).
The diagrams below can help to explain the reactive power;
Fig 2: Showing the diagrams of the reactive power as a parameter of power quality (Pasko,
2014).
The ratio between the apparent power and the active power is always known as the displacement
power factor (cos Ѳ) (Martin, 2013). The power factor gives a measure of how effective the
usage of the electrical energy is. When the power factor of installation is lower than the intended
value then a penalty will be imposed by the government (Gu, 2016).
Power factor is calculated through equation 3 below
Power factor = Real power
Appareant power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3

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This power factor is increased by using banks of capacitors which are installed to help
counteract the inductive reactive power.
And this can be illustrated in the diagram below
Fig 3: Showing banks of capacitors. (Pasko, 2014).
By the help of the banks of capacitors, the power factor can be increased to about 0.95
The below diagram illustrates graphically how power factor has been improved from Ѳ1 to Ѳ2
Fig 4: Showing power factor correction. (Pasko, 2014).
Q which is the reactive power can be obtained through the equation 4,

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X= E2
Q . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
And the value of X is obtained by equation 5 below;
Xc = 1
2 πfC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Where Xc is capacitive reactance, f is the frequency, E is the voltage.
iii. Flicker
Flicker is the variation in voltage or voltage fluctuation on the supply network which is due to
variation in luminance of lamps which will then develop the visual phenomenon known as
flicker, hence the name (McMurry, 2015). Repetitive and random changes in the voltage. These
voltage variations are due to mills, welding equipment, shredders and EAF operation (arc
furnaces). Beyond a given threshold it becomes irritating to individuals available in a room
which has the flicker. The extent of irritation grows abruptly with the heft of the fluctuation.
iv. Transients
This is also known as a fast disturbance,
Hasty variation in the sine wave which takes place in both current and voltage waveforms. This
is as a result of switching on components, start and stop of high power devices (Pearce, 2011).
These can differ broadly from two times the usual voltage to some thousand volts and they can
last from less than a μs up to some hundredths of a second. Transients are usually caused by a
quick release of electrical energy stored in a capacitive or an inductive source in the electrical
system, or from an external source like lightning (Sarma, 2013).
•Whilst the period of transients is inconspicuous to a human observer, their impact on quality of
power should still be considerable. This is because just a single lightning strike can lead to a
transient which is large enough to cause havoc to electronic devices.
A transient can be illustrated by the following diagram;

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Fig 4: Showing a diagram of a transient voltage. (Pasko, 2014).
v. Voltage variation
Voltage variations include dips, swells, brownout, and sags. Basically, this is due to line voltage
being higher or lower than the normal voltage for a shorter voltage (Sengupta, 2012).
Usually, the voltage variation is due to switching of the capacitive loads, network faults and
excessive loading. And diagrammatically this can be shown as below;
Fig 5: Showing voltage variations. (Pasko, 2014).

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vi. Oscillation
In some cases this is known as resonance, it is the flow of the electrical energy for instance
between the magnetic field of the inductor and the electric field in the capacitor which results to
the variation of the periodic changing of direction (Simeonov, 2012).
vii. Network unbalance
This is variation in the line voltage, it is usually caused by single-phase load, unbalanced three-
phase loads such as welding components and phase to phase loads. Network unbalance,
specifically in office building uses may lead to excessive voltage unbalance resulting to stress on
other loads which are connected to the same grid resulting to an increase in neutral current and
this will as well makes the neutral to earth to build up (Singh, 2016). This will lead to damage
to direct motor through developing a reverse torque.
Question Five
Electrical power storage is very vital since through electrical storage it is highly possible to use
the electrical energy after sometimes of electrical production. And this will highly help in
reduction of power losses (Wahome, 2012). Some of the electrical energy storage
technologies include the following;
i. BATTERY
Operation of battery

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The battery contains negative cathode of light and porous lead. The lead is
made I this way to promote the prearrangement and degeneration of lead. The
positive anode contains lead oxide. Both anodes are submerged in an electrolytic
prearrangement of sulphuric corrosive and water. In case the cathodes come into
contact with each other through physical development of the battery or through
changes in breadth of the cathodes, an electrical protection, but chemically
penetrable film detaches the two cathodes (Webinars, 2012). This film too evade
electrical shorting via the electrolyte.
The flow of the ions can be illustrated in the figure below;
Fig 6: Showing the flow of ions in a battery (Sarma, 2013)
Power quality
The power quality of the battery is relatively higher since it is basically a DC, therefore, it is not
affected by the parameters like harmonic, reactive power and so forth.
Variation in energy demanded
The variation in energy demanded in the battery is very big since the battery is ranging from
smaller ones to enormous types (Zeng, 2010).

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ii. COMPRESSED AIR ENERGY STORAGE
Operation of compressed air energy
The volume of air within the environment liberated from the collector will be
rise to the volume of the discuss discharged times the alter in weight isolated by
the climatic weight (key, 2015). Other than, the recipient weight alter is the
same as the ultimate weight subtract beginning weight and this may be outlined
in the equation below.
Vgas = Vrec ( pf −Pi)
Patm
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
The air after compression is pushed to the supply that is in utmost scenarios is set
down underneath the ground in the frame of the exhausted wells (Lucas, 2012). The
extended discuss ought to be warmed sufficiently so that it'll be capable to rotate
the turbines and consequently produce electrical control. As seen from the
condition PV=mRT, warming of the air will increment the weight of the gas. The
higher weight of the gas will rotate the turbine at a higher speed that is able to
result in the foundation of more electrical control (Martin, 2013).
Power quality
The power quality of the battery is relatively higher since it is basically a DC, therefore, it is not
affected by the parameters like harmonic, reactive power and so forth.
Variation in energy demanded
There is no variation in power demanded from this type of energy storage device, this is because
the energy storage device is almost in the same size not as in the battery (Loughran, 2013).
iii. PUMPED HYDRO-POWER ENERGY STORAGE
Operation of pumped hydro
In pumped hydroelectric power, there is some water which is stored in the reservoir, this water
will then be released through the penstock to the powerhouse at a very high speed. In the
powerhouse, the high-speed water is directed to the water turbines which will then rotate and in

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turn rotates the generators which are coupled with the turbines. This then will result in the
generation of electrical power. The arrangement of it is illustrated in the diagram below
Fig 7: Showing the pumped hydro. (Lucas, 2012)
Power quality
The pumped hydropower is always affected by the parameters which reduce the quality of
power, this is because this energy storage gives an AC power which is affected by the harmonics,
flickers, reactive power among others.
Variation in energy demanded
There is a large variety of power demanded from the pumped hydroelectric power because there
are some microgrids which generate a small amount of electrical power and there are also some
bigger pumped hydro which generates a large amount of electrical energy.
iv. FLYWHEEL
Operation of the flywheel
Flywheel stores energy through the angular momentum of the rotating object of a heavyweight.
The energy in the flywheel is stowed in the form of spinning kinetic energy (Singh, 2016). This
is given by this equation:
E = ½mv2 ………………………………………………………………………………………8

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Fig 9: Showing a flywheel. (Martin, 2013)
The energy will rise in case the esteem of omega (ῳ) and the minute of inactivity
( I) is expanded. The esteem of I can be expanded via finding more quantity on the
external side of the flywheel as more as conceivable. But the quantity included will
as it was being constrained by a few mechanical impediments to guarantee that it
works viably (Simeonov, 2012). The flywheel vitality capacity gadget can be
assigned as mechanical battery since it does not make power but it as it stored
vitality in a frame of active vitality and as it was discharged when it is required. The
flywheel moreover changes over the active vitality into electrical vitality (Singh,
2016). The energy is at that point produced by the turning wheel making this
innovation culminate arrangement for the domestic energy supply. (Zeng, 2010).
Variation in energy demanded
There is no variation in power demanded from this type of energy storage device, this is because
the energy storage device is almost in the same size.
Power quality
The power quality of the battery is relatively higher since it is basically a DC, therefore, it is not
affected by the parameters like harmonic, reactive power and so forth (Pakistan, 2013).

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