ELECTRICITY
AND ENERGY EFFICIENT
SAVE MONEY, USE MORE COPPER
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EFFICIENT
MOTORS
MAXIMUM SAVINGS
Did
you know that copper’s
high conductivity makes it possible to build
high-efficiency motors that make the best use
of energy at any load rate?
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A
motor inevitably loses energy during the process of converting power
into mechanical work. These losses may be grouped into two categories:
constant losses and load rate variation losses. The former comprise
losses originated by friction in the bearings, longer use of cooling
fans, or, simply, by the loss in the steel core. On the other hand,
losses generated by load rate variation are related to the motor windings’
electric resistance.
The
majority of motors run rather efficiently when they operate at full
load; however, their performance does vary when they have to work
ranging between 100% and 50% load. High-efficiency motors
have been designed to solve this problem and they can render significant
energy savings at any load rate.
Likewise,
due to their design, high-efficiency motors generate
less waste heat and require less energy for cooling purposes (only
small fans are required). The aforesaid results in double savings
and the incidental benefit from a significantly quieter operation.
Furthermore,
high-efficiency motor frames--even though their center height, shaft,
flange diameter and fastening holes are similar to those of conventional
motors--are different because they are longer at the non-drive end
and thus they can accommodate the windings and the core in a more
efficient manner.
In
order to reduce constant as well as load rate variation generated
losses, the use of energy-efficient motors should be specified at
the design stage of any project.
Effect
of Energy Efficiency on Operating Costs and Payback:
Example
One
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A
LARGE, 200 HP, 1800 RPM (460 volts) MOTOR OPERATING
ALMOST CONTINOUSLY IN AN INDUSTRIAL ENVIROMENT AT
FULL LOAD. DUTY CYCLE: 8,000 HOURS PER YEAR
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Standard
Motor
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High-Efficiency
Motor
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Efficiency
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92.4%
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96.2%
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Outout
Power (0.7457 kw/hp)
|
149.1
kW
|
149.1
kW
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Input
Power
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161.4
kW
|
155.0
kW
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Loss
at 100% Load
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12.3
kW
|
5.9
kW
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Power
Savings
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6.4
kW
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Incremental
Motor Cost
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$2,608
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Energy
Savings at 100% Load
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51,200
kWh per year
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Dollar
Savings at $0.040 per kWh.
Payback
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$2,048
per year
1
year 3 months
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Dollar
Savings at $0.074 per kWh.
Payback
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$3,789
per year
8
months
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Savings
are permanent. Once the investment is paid back, savings continue
over the full life of the motor.
Example
Two
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EVEN
FOR MUCH SMALLER, AND THEREFORE LESS EFFICIENT,
5HP, 1800 rpm (460 volts) INDUSTRIAL MOTOR RUNNING
ABOUT HALF TIME (4,00 HOURS PER YEAR) THE PAYBACK
IS SHORT.
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Standard
Motor
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High-Efficiency
Motor
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Efficiency
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84.0%
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89.5
%
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Output
Power
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3.73
kW
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3.73kW
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Input
Power
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4.44
kW
|
4.17
kW
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Loss
at 100% Load
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0.71
kW
|
0.44
kW
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Power
Savings
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0.27
kW
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Incremental
Motor Cost
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$94.80
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Energy
Savings at 100% Load
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1,080
kWh per year
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Dollar
Savings at $0.040 per kWh.
Payback
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$43.20
per year
2
years 2 months
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Dollar
Savings at $0.074 per kWh.
Payback
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$79.92
per year
1
year 2 months
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Source:
Copper Development Association Inc. (Asociación de Desarrollo delCobre
). The aforementioned tariffs correspond to July 1996 (Electric Tariffs
Commission). The average exange rate used is S/. 2.45 per US$ 1.
ELECTRICAL
COPPER CONDUCTORS
GREATER
EFFICIENCY - GREATER CONDUCTIVITY
When
electricity flows through an electrical conductor, energy is wasted
as heat. Heat losses depend on the conductor’s electric resistance
( R) and on the transmitted current ( I2 ); the formula
I2 R serves to determine the energy wasted. Thus, when
the amount of current that flows through an electrical conductor increases
there will be a greater energy loss in the form of heat.
In
the last years, new insulating materials with greater resistance have
been developed, seeking to fulfill the need to increase the transmission
capacity of electric conductors. These new materials have made it
possible to design conductors that can transmit more current, yet
having the same nominal section; a way to reduce First costs. However,
if we take into consideration the overall cost of the operating system,
the amount of money initially saved is lost due to higher costs generated
by energy loss, as heat, during the life cycle of the installation.
Therefore, placing more importance on the first cost is a
false economy.
A
reduction in the conductors’ resistance as well as energy savings
may be obtained by upsizing electric conductors.
Energy
waste as heat is not the only factor to be taken into consideration;
the cost increase to maintain the operating efficiency of an installation
should be also borne in mind. For instance, if the design of an air
condition plant is based on a first cost criterion, the effort to
lower the ambient temperature will be greater due to the increased
amount of heat caused by energy losses, as heat, from high resistance
conductors.
Then,
it is necessary and important to make the required projections that
include the evaluation of real differential advantages. The responsible
concern for efficient energy use should not be limited to the short
term.
Calculation
of Energy Losses in Conductors
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Characteristics
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Alt.
1
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Alt.
2
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Alt.
3
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Alt.
4
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Distance
(m)
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50
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50
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50
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50
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Power
(kW)
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50
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50
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50
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50
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Current
(A)
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164
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164
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164
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164
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CAI
Cable (mm2)
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25
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35
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50
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70
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Nominal
Section
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C.A.
Resistance (ohm/km)
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0.848
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0.611
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0.452
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0.313
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Power
Loss (kw)
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3.42
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2.47
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1.82
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1.26
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Energy
Loss (kw/h)
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6,840
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4,940
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3,640
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2,520
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167
Hs/month
2,000
Hs/year
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Annual
Losses Cost
Power
- Peak hour ($)
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834.48
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602.88
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444.08
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307.44
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20.32$/
kw-month
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Energy
Peak Hour ($)
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506.16
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365.56
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269.36
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186.48
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7.40c$/
kw/h
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Total
Losses Peak Hour($)
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1340.64
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968.24
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713.44
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493.92
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Anual
Loss Difference - Peak Hour ($)
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372.40
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627.20
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846.72
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Power
- Not Peak Hour ($)
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540.36
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390.26
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287.56
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199.08
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13.21
$/
kw-month
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Energy
- Not Peak Hour ($)
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273.60
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197.60
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145.60
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100.80
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4.00
c$/
kw/h
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Total
Losses - Not Peak Hour ($)
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813.96
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587.86
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433.16
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299.88
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Annual
Loss Difference - Not Peak Hour ($)
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226.10
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380.80
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514.08
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Conductor
Cost Differnce ($)
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133.35
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333.38
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600.08
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Average
Market
Cost
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Payback
-
Peak Hours
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4.30
months
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6.38
months
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8.51
months
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Payback
-
Not
Peak Hours
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7.08
months
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10.5
months
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1
year 2 months
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CAI
copper is based on the IEC standards (International
Electrotechnical Comission)
El
costo de la energía, es el promedio ponderado del costo en el Perú.
Advantages
of Electrical Copper Conductors
-
Copper’s
electrical conductivity is much higher than that
of any other common metal. Consequently, copper conductors of
less diameter than those made of other materials may be used to
transmit the same amount of current. Hence, costs decrease because
the required amount of metal and of insulating and coating materials
is lower and because there is no need for wider conduits.
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Copper
will always be more flexible and easier to install,
compared to any other alternative material that may be offered
as a substitute.
-
Since
copper has excellent corrosion resistance,
joints are easier to make. They do not lose their integrity throughout
their installed life and require little maintenance.
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