Training programme on Energy Efficient technologies for climate
change mitigation in Southeast Asia
Electrical Energy Systems
Efficient Technologies for Electrical Energy Systems
and
Concepts of Air conditioning systems applicable to Southeast
Asian countries
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Electrical Power supply system
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Efficiency in transmission and distribution
system
Generation Efficiency 1
Step-up Station 2
EHV Transmission & 3
Station
Efficiency ranges 28-38 % with respect to size of thermal plant, age of
plant and capacity utilization
Step-up to 400 / 800 kV to enable EHV transmission.
Envisaged max. losses 0.5 % or efficiency of 99.5 %
EHV transmission and substations at 400 kV / 800 kV. Envisaged
maximum losses 1.0 % or efficiency of 99 %
HV Transmission &
Station 4
HV transmission & Substations for 220 / 400 kV.
Envisaged maximum losses 2.5 % or efficiency of 97.5 %
Sub-transmission 5
Sub-transmission at 66 / 132 kV
Envisaged maximum losses 4 % or efficiency of 96 %
Distribution Station 6
Step-down to a level of 11 / 33 kV.
Envisaged losses 0.5 % or efficiency of 99.5 %
Primary Distribution 7
Distribution is final link to end user at 11 / 33 kV.
Envisaged losses maximum 5 % of efficiency of 95 %
End user Premises
Cascade efficiency from Generation to end user
= 1  2  3   4  5  6  7
The cascade efficiency in the T&D system from output of the power plant to the end use is 87% (i.e. 0.995 x
0.99 x 0.975 x 0.96 x 0.99.5 x 0.95 = 87%)
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Electricity Billing
The consumer depending on type (i.e.
industrial, commercial, residential, utilities
etc.) pays for:
- Energy Charges for kWh consumed
- PF penalty or PF incentives
- Maximum demand Charges (kVA) registered
– Time of Day (TOD), (peak and non-peak )
– Maximum Demand Penalty
– Metering rent
– Other Penalties etc.
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Power Factor (PF)
In most modern electrical distribution systems, the predominant
loads are resistive and inductive.
1)
Resistive loads are incandescent lighting and resistance
heating.
2)
Inductive loads are A.C. Motors, induction furnaces,
transformers and ballast-type lighting
Inductive loads require two kinds of power:
1)
Active (or working) power to perform the work (motion) and
2)
Reactive power to create and maintain electro-magnetic fields.
3)
The vector sum of the active power and reactive power make up
the total (or apparent) power used. This is the power generated
by the utility for the user to perform a given amount of work.
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Capacitors and Effect on PF
Example : In an industry there is a transformer installed with a rating of 1500 KVA
Transformer loading – 1160/1500 = 78 %
Capacitors totaling 410 kVAr installed
Transformer loading – 913/1500 = 61 %
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Rating of capacitors required
• The utility bill shows an average power factor of 0.72 with an
average KW of 627. How much KVAR is required to improve the
power factor to .95 ?
• STEPS:
Cos F1 = 0.72 , Tan F1 = 0.963
Cos F2 = 0.95 , Tan F2 = 0.329
Kvar required = P ( Tanf1 - Tanf2 )
= 627 (0.964 – 0.329)
= 398 kVAr
• Now that we have determined that capacitors totaling 400 KVAR
must be installed, we must decide where to locate them
• For motors of 50 hp and above, it is best to install power factor
correction capacitors at the motor terminals since distribution
circuit loading is reduced
• Capacitor banks can also be connected at the bus bar for each
motor control centre. This is a compromise to reduce installation
costs
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Advantages of PF correction
• Capacitors can reduce losses by 1- 2% of the total
load

% Loss Reduction = 1 -
PF1 / PF2 
2

x 100
• Reduction in maximum demand
We know that kW = kVA x Cos F
If the maximum demand is 1500 kVA at 0.85 p.f. calculate
the reduction in demand at 0.95 p.f.
Active Power = 1500 x 0.85 = 1275 kW
Maximum demand after PF improvement,
kVA at 0.95 p.f. = 1275/0.95 = 1342 kVA
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Technology : Automatic PF controllers
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Maximum Demand (MD)
•The demand varies from time to time. The demand is measured over
predetermined time interval and averaged out for that interval as shown by
the horizontal dotted line.
•It is important to note that while maximum demand is recorded, it is not the
instantaneous demand drawn, as is often misunderstood, but the time
integrated demand over the predefined recording cycle
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Example of Computing MD
– As example, in an industry, if the drawl of
power over a recording cycle of 30 minutes
is :
– 2500 kVA for 4 minutes
– 3600 kVA for 12 minutes
– 4100 kVA for 6 minutes
– 3800 kVA for 8 minutes
– The MD recorder will be computing MD as:
– (2500x4) +(3600 x 12) + (4100 x 6) + (3800 x 8)
kVA
30
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= 3606.7
Load Management Strategies
• Reschedule loads/Staggering of
motor loads
• Storage of products/in process
material/process utilities like
refrigeration
• Shedding of non essential loads
• Operation of Captive power
generation
• Reactive power compensation
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Technology : MD controller
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Harmonics
• In AC network, flow of current depends upon the voltage applied
and the impedance (resistance to AC) provided by elements like
resistances, reactances of inductive and capacitive nature. As the
value of impedance in above devices is constant, they are called
linear whereby the voltage and current relation is of linear nature.
• However in real life situation, various devices like diodes, silicon
controlled rectifiers, thyristors, voltage & current reducing
electronic devices, induction & arc furnaces etc. are also deployed
for various requirements and due to their varying impedance
characteristic, these NON LINEAR devices cause distortion in
voltage and current waveforms which is of increasing concern
•
Devices that draw non-sinusoidal currents when a sinusoidal
voltage is applied create harmonics. Frequently these are devices
that convert AC to DC. Some of these devices are listed below:
–
–
–
–
–
Electronic Switching Power Converters
Computers, Uninterruptible power supplies (UPS), Solid-state rectifiers
Electronic process control equipment, PLC’s, etc
Electronic lighting ballasts, including light dimmer
Reduced voltage motor controllers
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Problems due to Harmonics
•
•
•
•
•
•
•
Blinking of Incandescent Lights
Capacitor Failure
Conductor Failure
Flickering of Fluorescent Lights
Fuses Blowing
Motor Failures (overheating)
Transformer Failures
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Technology : Harmonic Filters
• Tuned Harmonic filters consisting of a capacitor
bank and reactor in series are designed and
adopted for suppressing harmonics, by providing
low impedance path for harmonic component. The
Harmonic filters connected suitably near the
equipment generating harmonics help to reduce
THD to acceptable limits.
• Benefits of Harmonic Filters
Improve power factor ratings through harmonic
recombination
Isolate harmonic currents
Minimize equipment problems through THD cancellation
Reduce wasted energy
Minimize current carried in plant cables
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Technology : Soft Starter
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Concepts of AC and chilling systems
• What is a Ton of refrigeration (TR) ?
• The cooling effect produced is quantified as
tons of refrigeration. 1 ton of refrigeration is
equal to 3024 kCal/hr heat rejected
• The plant capacities upto 50 TR are usually
considered as small capacity, 50 – 250 TR as
medium capacity and over 250 TR as large
capacity units.
–Vapor Compression Systems
–Vapor Absorption Systems
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Options for AC and refrigeration systems
• Air Conditioning
–
–
–
–
Air Conditioning (for comfort / machine)
Split air conditioners
Fan coil units in a larger system
Air handling units in a larger system
• Refrigeration
– Small capacity modular units of direct expansion type
similar to domestic refrigerators, small capacity
refrigeration units.
– Centralized chilled water plants with chilled water as a
secondary coolant for temperature range over 50C
typically. Can also be used for ice bank formation.
– Brine plants, which use brines as lower temperature,
secondary coolant, for typically sub zero temperature
applications, which come as modular unit capacities
as well as large centralized plant capacities.
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Cycle of vapor Compression System
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Cycle of vapor Compression System
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Vapor Absorption System
• The absorption chiller is a machine, which produces
chilled water by using heat such as steam, hot water,
gas, oil etc.
• Chilled water is produced by the principle that liquid
(refrigerant), which evaporates at low temperature,
absorbs heat from surrounding when it evaporates.
• Pure water is used as refrigerant and lithium bromide
solution is used as absorbent
• Heat for the vapour absorption refrigeration system can
be provided by waste heat extracted from process,
diesel generator sets etc. Absorption systems require
electricity to run pumps only.
• Depending on the temperature required and the power
cost, it may even by economical to generate heat /
steam to operate the absorption system
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How does VAR system work
1. Boiling point of the water is a function of pressure. At atmospheric
pressure water boils at 100 deg. C. When maintained at high vacuum,
water will boil and subcool itself. The boiling point of the water at
6 mm Hg (abs) is 3.7 deg. C.
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How does VAR system work
2. Lithium Bromide (LiBr) has the property to absorb water due to its
chemical affinity. At higher concentration and lower temperature LiBr
absorbs water vapour (refrigerant vapour) very effectively
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How does VAR system work
3. As Lithium Bromide becomes dilute it loses its capacity to absorb
water vapour. It thus needs to be re-concentrated using a heat
source. Heat source may be Steam or Flue gases or even Hot
water.
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How does VAR system work
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Advantages of VAR system
• Li-Br-water absorption refrigeration systems have a
Coefficient of Performance (COP) in the range of 0.65 0.70 and can provide chilled water at 6.7 oC with a
cooling water temperature of 30 oC.
• Systems capable of providing chilled water at 3 oC are
also available. Ammonia based systems operate at
above atmospheric pressures and are capable of low
temperature operation (below 0oC).
• Absorption machines of capacities in the range of 101500 tons are available.
• Although the initial cost of absorption system is higher
than compression system, operational cost is much
lower-if waste heat is used
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Case Study : VAR - Trigeneration
Simultaneous production of heat, electricity and
chilled water
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Tri-generation - Process
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Components of Tri-generation
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Vapor Absorption Refrigeration
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System Configuration
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For further inquiries Contact
Rajiv.garg@unep.org
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