Energy Audit-seminar.doc (Size: 189 KB / Downloads: 323)
Energy Audit means the verification, monitoring and analysis of use of energy including submission of technical report containing recommendations for improving energy efficiency with cost benefit analysis and an action plan to reduce energy consumption. Energy audit is an important process to be carried out for energy conservation. In energy conservation, the thrust is given on the saving of energy while carrying out the required work. Some amount of energy is always required to carry out the required work which may be associated with inherent losses which cannot be eliminated. For example, in case of an induction motor, to operate it is necessary to pass the current through its winding with generates an alternating flux. This flux is responsible for an iron loss in the machine. The current causes the copper loss and since it is necessary to operate the motor, these losses cannot be eliminated. However, there are some additional losses such as bearing, fictional losses etc which are inherent, that can be reduced. These types of losses and their amount can be located using the technique of energy audit. The reduction of the losses located in energy audit, is done in energy conservation.
The periodical energy audit offer but in the complex plant or equipment is helpful for its condition assessment that is whether replacement of some components in the system is required or whether there is necessary to carry out a particular type of maintenance. For example, if the quantity of fuel required by the boiler to generate same quantity of steam increases, it indicates that the water tubes are having salt deposits from inside, due to which the rate of heat transfer has been reduced, due to low thermal conductivity of salt. If the tubes are not cleaned then there are chances of busting of the tubes due to overheating. The type of indication is possible only if frequent energy audit is carried out.
The energy audit also helps in calculating the cost of energy required to manufacture a product. This helps in calculating the total cost of the product. And the conservation can suggest how this cost can be reduced by suggesting alternative methods or by reducing various losses in the system.
Need for Energy Conservation:-
1) Increase of cost of Energy :-
The cost of energy involves following two factors:
a) Fixed cost.
b) Running cost.
Fixed cost depends on the MW capacity and installed capacity of the power station. This cost is fixed and it cannot be reduced.
Running cost depends on cost of fuel used for the production of energy. Cost of fuel is increasing day by day so the running cost is increasing. Thus energy consumption has to be controlled which is done by using alternative methods which consume less fuel. These alternative methods are suggested by carrying out energy audit. So the energy conservation suggests an economic and efficient method for performing certain processes.
2) Reduction of cost of product :-
The cost of product involves raw material cost, labor cost, energy cost and overheads. The raw material and labor cost cannot be reduced as it is constant. But the cost of energy and overheads can be reduced by energy conservation.
In todayâ„¢s world of competition, to enter into the international market your product must have quality and also its cost must be low. So with the help of energy conservation, the cost of energy can be reduced which will reduce the cost of the product and it will compete in the international market.
3) Pollution :-
Burning of coal, natural gas, crude oil, etc leads to pollution and increase in content of CO2 in air. Also other residuals of burning such as ash, heavy water from nuclear power plants etc cause land, water and air pollution which are hazardous to human life.
If this pollution is reduced, it directly reduces the amount of natural energy sources being burnt which reduces the amount of these sources being used and hence saves their reserves on earth.
4) Reduction of natural energy sources :-
Due to industrialization the usage of natural energy sources such as coal, crude oil, natural gas has increased heavily in the last four decades. These being conventional energy sources have a finite end. Studies made show that coal by 2050 will be a history on earth. So the conservation of such energy sources is very important.
Industries use coal, natural gas, crude oil for heating purpose. Electricity is also used for heating purpose. In this process millions of tones of natural energy sources are used. If non-conventional energy sources such as solar energy, geothermal energy are used, the reserves of natural energy sources can be saved as their usage decreases hence the rate at which they are being used today decrease.
If this goal is achieved a large amount of natural resources can be saved and can be kept safe from being exhausted as they are limited on earth.
Energy Conservation Potential in the Various Sectors in India:-
The Energy Conservation Act has specified certain energy intensive industries as Designated Consumers, which would have to comply with energy consumption norms and energy audits, etc., by accredited energy auditors, as per the specified manner and time intervals. The industrial sector in India is a major energy user, accounting for 48% of the commercial energy consumption. The energy saving potential in this sector is estimated to be 25% of the total consumption, the maximum as compared to any other sector. On a conservative estimate, this saving potential in India is equivalent to creating nearly 25,000 MW of new generation capacity! The Energy Conservation Act seeks to realize this energy saving potential, of which only a small fraction has been realized so far.
India has a very high level of energy consumption relative to its GDP (gross domestic product), even though the country's overall consumption is very low. The table below gives the potential for energy conservation in various sectors.
Sector Conservation Potential (%)
Industrial Sector Upto 25
Agricultural Sector Upto 30
Transport Sector Upto 20
Domestic Sector Upto 20
Commercial Sector Upto 30
Energy Conservation Potential in Maharashtra:-
a) Industrial Sector:-
Maharashtra is a leading industrial state in India with around 28678 factories registered. The industrial sector consumed 18363.1 million units, which is 38.69% of the total generated electrical energy in Maharashtra; in 2000-2001 (total generation was 47464 million units).
According to experts, 25% saving potential exists in the industrial sector (the range varying from 8% to 10% in iron and steel refineries, etc., to 25% in pulp and paper) and accordingly 4590 million units can be saved. This can avoid 720 MW thermal power capacity additions (at 70% PLF). This does not include further saving that are possible through major technology changes. This potential could be realized through measures whose capital and life-cycle costs are less than that needed to generate equivalent amounts of energy supply.
Almost 5% to 10% of the potential saving can be realized by adopting no-cost housekeeping measures. A substantial portion of the balance potential can be realized with retrofitting or minor process / technology improvement measures. The payback periods for such measures range from a few months to less than 3-4 years.
b) Domestic Sector:-
The domestic sector consumes 23.54% of the total electricity generated and consumed in Maharashtra, with major end-users as lights, fans, refrigerators, air-conditioners, water heaters, etc. During 2000-2001, the domestic sector consumed 11171.9 million units and it is observed that this consumption is growing very fast. According to experts 20% saving potential exists in this sector. By taking energy conservation steps, it will be possible to save about 2234.38 million units. This will avoid 350.49 MW thermal power capacity addition (at 70% PLF).
In the domestic sector, replacing bulbs with energy efficient tube lights or CFLs can bring about significant power saving. It is estimated that when a bulb is replaced by CFL, the saving of Rs.1200 per bulb in energy costs could result over the lifetime of the CFL. Offices, commercial and industrial establishments could achieve greater saving by switching over to more efficient fluorescent tubes and CFLs. If we replace
all the conventional bulbs with CFLs in phases, we can shave off around 1200 MW from the peak load. If we replace electrical ballast of our tubes lights with electronic ballast, around 900MW peak load can be shaved off.
Solar water heating systems are extremely competitive in comparison to electrical water heating applications, when the total energy costs over the life of the system are accounted for. Although the initial cost of solar water heaters is higher than that of conventional water heaters, the fuel is free. If all households, government buildings, hotels, etc. adopt solar water heating systems, 500 MW can be shaved off from the peak load. MEDA has already initiated a proposal to make this mandatory, in a phased manner.
c) Commercial Sector:-
The commercial sector consumed 4105.5 million units of electricity in 2000-2001. This is 8.65% of total electricity generated in Maharashtra. According to experts, there is an energy-saving potential of around 30%. By adopting energy conservation methods, we will be able to save around 1231.65 million units. This will save 193.2 MW capacity addition. It could further increase to 50%, provided upcoming buildings adopt solar passive architecture and incorporate energy efficient features in their construction.
Thus, with properly planned implementation of energy conservation measures in the next 10 to 12 years, Maharashtra could save about 3000 MW of power during peak load, in the above sectors alone. Besides, efficiency improvements in agricultural sector, reduction of transmission losses in high-tension lines, etc., could further increase the potential for saving. MEDA would soon be holding a seminar to prepare a State-wide action plan for energy conservation for the next 12 years.
Energy Conservation Act-2001:-
This act has provided the Bureau of Energy Efficiency (BEE) with the following powers:-
(a) recommend to the Central Government the norms for processes and energy consumption standards required to be notified under clause (a) of section 14 ;
(b) recommend to the Central Government the particulars required tobe displayed on label on equipment or on appliances and manner of their display under clause (d) of section 14;
© recommend to the Central Government for notifying any user or class of users of energy as a designated consumer under clause (e) of section 14;
(d) take suitable steps to prescribe guidelines for energy conservation building codes under clause (p) of section 14;
(e) take all measures necessary to create awareness and disseminate information for efficient use of energy and its conservation;
(f) arrange and organize training of personnel and specialists in the techniques for efficient use of energy and its conservation;
(g) strengthen consultancy services in the field of energy conservation;
(h) promote research and development in the field of energy conservation;
(i) develop testing and certification procedure and promote testing facilities for certification and testing for energy consumption of equipment and appliances;
(j) formulate and facilitate implementation of pilot projects and demonstration projects for promotion of efficient use of energy and its conservation;
(k) promote use of energy efficient processes, equipment, devices and systems;
(l) promote innovative financing of energy efficiency projects;
(m) give financial assistance to institutions for promoting efficient use of energy and its conservation;
(n) levy fee, as may be determined by regulations, for services provided for promoting efficient use of energy and its conservation;
(o) maintain a list of accredited energy auditors as may be specified by regulations;
(p) specify, by regulations, qualifications for the accredited energy auditors;
(q) specify, by regulations, the manner and intervals of time in which the energy audit shall be conducted ;
® specify, by regulations, certification procedures for energy managers to be designated or appointed by designated consumers;
(s) prepare educational curriculum on efficient use of energy and its conservation for educational institutions, boards, universities or autonomous bodies and coordinate with them for inclusion of such curriculum in their syllabus;
(t) implement international co-operation programmes relating to efficient use of energy and its conservation as may be assigned to it by the Central Government;
Potential for Energy Conservation in Various Processes:-
Energy conservation in the following area of the industries can be done effectively:-
i. Bagasse is a byproduct of sugar cane that is used as fuel in boilers to produce process steam. The consumption of bagasse depends upon the pressure at which steam is produced in boiler. Co-generation projects with higher boiler pressure results in low computation of bagasse, resulting in increased operating days.
Conventionally boilers of 40 bar pressure are in use. Based on the studies carried out in many sugar factories, use of high pressure boilers (60 bars and 100 bars) makes such power projects highly profitable.
ii. Even in heating applications, where boilers are used for producing process steam, the pressure of the boiler can be increased and the some of the steam can be used for power generation from steam turbine as well.
iii. In Dabhol Power Plant, there are two gas turbines and a steam turbine. The flue gases from gas turbines are used in the economizer and the air pre-heaters of the steam turbine.
2. Energy conservation in Oven:-
i. Leakage of heat transfer may occur through the existing thermal insulating material, which may lead to fall in temperature which demands more energy to maintain the required temperature. By replacing the existing material with other having low thermal conductivity will result in decrease in energy consumption.
ii. Heat loss can also be prevented by covering the outer surface with insulation material like jute, tarpoline.
iii. In a system, where temperature control is done using a thermostat, the thermostat may require time to sense the heat. This is called the time lag of the thermostat and some energy wastage occurs since the heating maybe done above the preset point.
This can be done by a Resistance Temperature Detector(RTD) which is small in size and responds to temperature changes within short time i.e. the time lag is small.
iv. The electronic control can supply only the required amount of energy using the phase angle technique.
v. The wall, trays and other mechanical components should be made of aluminium and copper, since they have higher specific heat capacity value than steel.
3. Energy conservation in illumination:-
a) Operational means:-
i. Keep walls and ceilings clean.
ii. Keep luminaries(reflectors) clean.
iii. Open the windows to permit maximum sunlight. Supplement natural light with artificial light and not the vice versa.
iv. Activity sensors maybe used to switch off lights when not required.
b) Constructional means:-
i. Use high efficiency lamps. Replace filament lamps with compact fluorescent lamps (CFL).
ii. Use mercury or sodium vapour lamps which are having high efficiency.
iii. Give bright colour to walls and ceilings.
iv. Avoid wastage of light thereby reducing no. of lamps.
v. Use electronic chokes for fluorescent, mercury and sodium vapour lamps.
vi. Use transparent roofing sheets wherever possible (material maybe acrylic or fiber glass).
vii. Suitable reflectors maybe used so that light can be concentrated on the required plane of illumination.
Â¢ Disadvantages of inductive choke:-
i. It is an inductive circuit, so has a low power factor.
ii. Losses are more so energy consumption is more, around 18-20W.
iii. The cement may destroy as time passes and air enters which reduces pressure in the tube.
Â¢ Advantages of electronic choke:-
i. Can sustain variation in supply (230V +/- 6%).
ii. Losses are less, so energy consumption is less about 0.5 to 1W.
iii. No flickering, the tube light starts instantly.
Generally, the tubes have rating of 40W and the iron chokes consume 18W, so total power consumption equals 58W. If the tubes are replaced by 36W tubes and iron chokes are replaced by electronic chokes which consume 1W, then the total consumption equals 37W.
Â¢ For e.g., the following case might be considered to get an idea of the saving in illumination:
No. of tubes= 44
No. of chokes= 44
Tubes are ON for 20 hours.
Power consumed by 40W tube and iron choke= 58W.
Energy consumed/day= 58 x 20 x 44
Power consumed by 36 tube and the electronic choke= 37W.
Energy consumed/day= 37 x 20 x 44
Energy saved/day= 51.04 â€œ 32.56
Cost of energy saved/day= 18.48 x 5
Cost of 36W tube= Rs.80.
Cost of electronic choke= Rs.300.
Cost of new equipment= 44 (300 + 80)
Payback period= 16720
Payback period â€°Ë† 181 days
4. Energy conservation in ventilation:-
a) Operational means:-
i. Keep the windows open for helping cross ventilation and maintaining the air flow.
ii. Supplement natural ventilation with artificial ventilation.
b) Constructional means:-
i. Use fans having motors of higher efficiency.
ii. Use electronic regulators which have losses of about 0.5-1W as compared to 8-10W of resistance regulator.
5. Energy conservation in air conditioning:-
a) The heat leakage occurs through the walls of the room. If the thickness of wall is more, the heat leakage is reduced, so while the construction work is in progress the wall thickness can be increased. If the construction is already complete the walls should be covered using wood or fiber glass sheets so as to reduce the thermal conductivity and reduce heat losses.
b) If the air conditioned room is located at the top floor, just below ceiling high heat losses occur since the ceiling is directly exposed to sunlight throughout the day. These losses can be reduced by covering the top slab using thermal insulating material like tarpoline, jute. It is advised to construct a terrace garden on the top of the slab after water-proofing.
c) The quantity of heat to be extracted depends on the volume of the space. So to reduce this volume arrangements like false ceilings are to be done with thermal insulating materials like ceiling tiles or thermocol. Thermocol also provides better illumination due to high reflection and the no. of lamps to be provided in the room also reduces.
d) No sources of heat should be kept in the space to be provided with air conditioning arrangement. Since more quantity of energy than the quantity of heat generated will have to be provided to the compressor. For this reason, filament or hydrogen lamps are not recommended to be used in the space.
e) The heat leakage also occurs through the small gaps of doors and the frame. Proper ceiling should be provided to reduce this loss. A double door arrangement is also recommended to reduce this loss.
f) The frequent opening of the doors can cause the transfer of cold air of the space to the atmosphere and the hot atmospheric air to the air conditioning space. This can be reduced by controlling the operation of door. If the door is to be operated frequently, the double door system is to be used to reduce this loss of heat.
g) The motors are used to drive the fans and compressors. To reduce the input energy, energy efficient motors are recommended to be used having high efficiency.
h) The window glasses or panes should be covered with sun control films which will block IR rays in the sunlight which are responsible for heat generation. These films will permit only visible light rays to enter inside the room.
6. Energy conservation in electric motors:-
a) It is observed that the efficiency of the motor reduces if the output is reduced. This happens because at lower output the constant losses such as iron, windage and bearing friction are predominant over the variable losses (stator and rotor copper losses). The overall efficiency is thus reduced. The maximum efficiency occurs when the variable losses=constant losses and generally the motors are designed to have maximum efficiency at 85-90% of full load. So to reduce the energy loss i.e. to conserve energy it is recommended to run a motor near to its maximum efficiency in between 85-90% of load.
b) It is found that the motor takes higher current if the terminal voltage is higher or lower than the limits of the rated voltage. The terminal voltage should be 415VÃ‚Â±6% or 440VÃ‚Â±6% depending upon the rating o f the motor. When the voltage is low the motor develops low torque (TÃŽÂ±V2) and the speed drops increasing the slip which increases the rotor current in counterpart increases the stator current. For higher voltage, the motor draws more current since I=V/Z. So due to higher or lower voltage the copper losses increase reducing the efficiency. So it is necessary to maintain the voltage across the terminals of the motor within the limits to reduce the losses. This done by adjusting the tap of the distribution transformer which provides power to the motor.
c) Out of the total losses the friction and windage are about 10-15%. These losses can be reduced by properly maintaining the bearings by providing the proper lubrication. The windage losses can be reduced by keeping the ventilation passage clean. To keep the ventilation passage clean the outer body of the machine should also be clean. Due to dust over the surface the heat transfer rate decreases.
d) It is necessary to maintain the voltage across terminals of the motor. This can be done by connecting a capacitor across the motor terminals. The capacitor current, which is leading component to the inductive current component of the motor nullifying partially the inductive current and reducing the total current drawn by the motor. Consequently, reducing the voltage drop in the cables or conductors supplying power to the motor and voltage at terminals maintained constant.
e) Generally, it is seen that motors connected to various equipments are over size i.e. of higher capacity than the driving motor or small size to the load (for e.g., if power requirement is 10HP, the motor is of 15HP or vice versa). The higher capacity motors have more iron loss which being constant loss is unnecessarily reducing the efficiency of the system.
Â¢ For e.g., a motor of the following rating is under loaded, then system efficiency can be improved by replacing it with a motor of lower rating. The calculations for the new motor and its payback period have been done below: -
Output=1H.P. =746W; 3ÃŽÂ¦; 415V; p.f. =0.8; ÃŽÂ· (full load) =85%; I=0.7A.
Efficiency, ÃŽÂ·=output x 100
Input= output x 100= 746 x 100
Input = Ë†Å¡3 x VL x IL x cosÃŽÂ¦
IL = 877.64
Ë†Å¡3 x 415 x 0.8
Losses= input â€œ output
= 877.64 â€œ 746
At full load,
Iron losses= copper losses= 131.64= 65.82W
65.82 = 4.75
(Losses)0.7 = 65.82
(Losses)0.7 = 13.85W
PIN= Ë†Å¡3 x 415 x 0.7 x 0.8
POUT= PIN â€œ losses
= 402.52 â€œ (13.85+65.82)
POUT = 0.43H.P.
If this motor is replaced by 0.5H.P. motor, having ÃŽÂ·= 87%.
Input= 0.5 = 0.57H.P. = 428.735W.
Input of 1H.P. motor= 877.64W.
Power saved= 877.64 â€œ 428.735
Power saved= 0.448kW
Energy saved/day= 0.448 x 23.5*
Cost of energy saved/day= 10.52 x 5
Cost of 0.5H.P. motor= Rs.2880
Payback period= (2880 â€œ 432) Â¦..(Scrap value- 15% of cost of new machine.)
payback periodâ€°Ë† 47 days.
Â¢ A simulation in MATLAB can be used to prove the increase in efficiency: -
i. Following is the model of a 3kW motor driving a load torque of 2Nm.
The Display gives input power to the motor=278.3W
The Display1, gives rotor speed (Ãâ€°) in rad/s, armature current, field current and the motor torque, giving Ãâ€°=112.3rad/s and the T=1.989Nm .
Thus the output power= Ãâ€°T=112.3*1.989
Thus the efficiency=223.3647*100=80.26%
ii. Following is the model of a 1.5kW motor driving the same load torque of 2Nm.
Ãâ€°=187.3rad/s and T=4.76Nm
Thus output power= Ãâ€°T=187.3*4.76
Thus the efficiency=891.548*100=87.92%
f) Nowadays, in market energy efficient motors are available which have their efficiency about 87%. The size of motor is higher than the normal size motors by 15-20% and the cost is also high. However the higher cost is recovered due to low losses and therefore less energy is consumed over a period of six to eight months.
g) Automatic star-delta converters are available. In this, a CT is provided in one of the phases which sense the current taken by the motor in delta connection. If the current taken is less than 1/3rd of the rated current then the windings automatically get connected in star. The voltage across the windings, in star, is less than 1/3rd of delta. Due to this, the iron losses in motor are reduced causing substantial saving of the energy if the motor is operating for a longer time.
The changing of connections from star to delta and vice versa is done using contactors. A suitable time delay circuit is provided to ensure that the reduction in current is for longer time and not for a short duration.
7. Energy conservation in transmission and distribution sector: -
a) Energy loss occurs in transmission and distribution of electrical energy. This loss is due to the resistance of the conductors of the transmission lines and the square of the current flowing through it.
The resistance of the conductor can be decreased by increasing the cross-sectional area of the conductor. This increases the cost of the conductor and the economic analysis whether the additional cost compensates for reduction in the losses is to be done. For AC transmission and distribution lines, instead of a solid conductor, stranded or bundled conductors can reduce the effective resistance. Since due to skin effect, the resistance of solid conductor is more than that of bunch of small conductors of equivalent cross-sectional area.
b) In case of very long transmission lines, the capacitance of line is important which increases receiving end voltage increasing the load current. This can be controlled by providing reactors at suitable position. There will be minimum losses when the power factor is unity for transmission lines and suitable adjustment of reactors and capacitors connected across lines is to be done to achieve it.
c) In transmission and distribution system, the conductors are joined at no. of places and care is to be taken to see that the contacts are tight to keep the contact resistance as minimum as possible. The equipments in which opening and closing of contacts takes place as in case of circuit breakers. It should be ensured that when the contacts are in closed position adequate contact pressure is applied on the conducting part so as to reduce the contact resistance and the possible energy loss i.e. I2R which appears in the form of heat. Since the value of current is high a small increase in the value of resistance can increase the losses substantially.
d) In case of distribution system, the losses in the distribution transformer form the major part. Since the transformer is a static device, it is having high efficiency around 92-98% depending on its rating. For higher rating, the efficiency is high. However if the efficiency is improved by 1% there is going to be substantial energy saving since the transformers are ON for 24hrs/day and 365days/year. Fr e.g., a 1000kVA transformer operating at unity power factor and with 98% efficiency will have a loss of 20kW. If the efficiency is improved by 0.5%, the losses will be 15kW and the daily saving of energy will be 5*24=120kWh costing around Rs.600/day and the annual saving will be around Rs.2,20,000.
i. As it is known the major losses in transformer are copper losses due to the resistance of the conductor. The resistance can be decreased by lowering the current density i.e. by increasing the cross-sectional area of conductor. However to reduce the skin effect, the winding carrying more current (LV winding) is wound with bundled conductors in which the no. of conductors insulated from each other are connected in parallel to form required cross-sectional area. Since the conductors are located in the magnetic field generated by their own current or by other turns, eddy current loss takes place in them. To reduce these losses, nowadays instead of rectangular bar conductors the winding is done by copper sheets of thickness 0.5-1micron. This arrangement not only reduces the eddy current loss in the conductor but also increases the mechanical strength at short circuit. However this arrangement increases the area required by the winding and hence the area
of window increases. The quantity of copper also increases by 5-10% depending on the size of the transformer.
ii. The iron losses occur in yoke and core limbs. This can be reduced by increasing the cross-sectional area of yoke and limbs thereby reducing the flux density. Generally for limb the flux density is about 1.5-1.7 Wb/m2 and for yoke it is 1.2-1.5 Wb/m2. The iron losses i.e. eddy current losses and hysterisis losses increase with the flux density and for 1.5Wb/m2, the general values are 1.5-2W/kg for dynamo grade steel, 0.8-1.5W/kg for CRNGO and it is 0.5-1W/kg for CRGO steel having thickness of 0.5mm. If the thickness is reduced then the core losses get reduced. By using CRGO steel of thickness 0.35mm the losses are around 0.3-0.5W/kg.
iii. These losses can be further minimized by using the core of amorphous material. The material is having a glass-like or amorphous structure. Thins strips of material are prepared, insulated and used in the transformers. This material is having high resistivity reducing the eddy current losses. The typical iron loss of 0.2W/kg and there is a substantial reduction of iron loss about 40% of the losses than CRGO. This transformer is called as the amorphous core transformer. The cost of this transformer is 25% high however the payback period is 6-8 months after which substantial saving occurs.
e) In case of distribution system, the fuses are the components in which continuous energy loss occurs. In industries like TATA motors, more than 5000 HRC fuses are used which are continuously ON causing great energy loss i.e. if a fuse is consuming 2W power the total loss for 24hrs is 240kWh. This loss can be reduced by replacing the fuses with the ones consuming 0.8-1W, thereby reducing the energy loss to 120kWh. These fuses cost about 35% higher but the payback period for higher cost is about 40-60days after which continuous saving occurs.
f) If the distribution is done using cables, the conductor loss can be reduced by using copper cable in place of aluminium, since the cables are ON for 24hrs, the additional cost is recovered in short time.
Procedure for energy audit:-
1) The first step is to draw the plan of the establishment indicating various equipments consuming energy. The transmission or distributor conductors consuming energy continuously are also to be shown on the diagram. The position of doors and windows are also to be shown on the diagram. Since it is helpful to access the availability of natural light and ventilation. The plan for each floor has to be drawn for a multi storied building.
2) The next step is to carry a walking energy audit. In this type of energy audit, a team of experts or senior engineers take a walk through the area whose energy audit is to be carried out. While taking the round, it may be possible to locate some places, where the wastage of energy can be seen or it may be possible to get an idea about energy saving. Some of the situations are as under :
a) Leakage of water from water taps: The water in overhead tanks is pumped using pumps which require energy. The stoppage of water leakage can save the energy in pumping and also the cost of water wastage.
b) Leakage of compressed air: In industries compressed air is used to perform various operations. Compressor is used to generate compressed air and it is driven by an electric motor. Stoppage of compressed air leakage can save the energy required to drive the compressor.
c) Lamps and fans operating without any occupant in the room: Since energy is required to operate lamps and fans there is wastage of energy if no person is in the room, at this situation.
d) Dirty transparent roofing and window panes: If the transparent roofing and window panes are also clean, there may not be a requirement of artificial lighting and energy can be saved.
e) Closed windows: If the windows are open then sufficient natural ventilation is achieved and the fans may be switched off.
f) Equipments kept on, without operation being carried out: In such cases the equipments consume constant losses for which the industry has to pay so the equipments like welding transformers should not be switched on if the welding work is not carried out; since the primary of the transformer is energized the iron losses occur.
g) The heat loss through the walls of the oven can be saved by sensing the temperature by keeping the hand on the outer chamber.
The above type of study is carried out at various times, various days and various shifts. To understand the operational losses like opening the doors of the oven or the air conditioned room. The observations are to be drawn at various times each day for five to seven days.
It is possible to locate the places of reducing energy losses from 5% to 7% by this method.
3) Detailed energy audit study: In this step, the detailed analysis of energy consumption pattern of equipments is carried out. This is called as ABC analysis. After locating the various energy consuming equipments in the plant, a chart is prepared indicating the type of equipments and their ratings. The equipments are divided in three categories :
A. Equipments consuming about 60 % to 70 % of total energy.
B. Equipments consuming about 20 % to 35 % of total energy.
C. Equipments consuming about 5 % to 15 % of total energy.
In A category, the major operating equipments like large compressors, pumps and machines which are continuously on, or ovens are involved. In B type equipments, small motors like grinders or drilling machines or welding transformers, which are intermittently operated are involved, and in C type the lighting and ventilation equipments are involved. So to achieve major energy saving thrust is to be given for reduction in energy consumption of type equipments, first.
4) In the next step data collection is done. The data regarding the on time of equipments per day and whether the equipments were fully loaded or not is collected. The data regarding energy input is collected by connecting various recorders and energy meters. If it is not possible to connect the meters by disconnecting the equipments and if the recording equipment is not available the current of the equipment is measured using a tong tester. After fixed interval of time and the status for that interval is assumed to be maintained. For example: If the recording time is 30 minutes and the recording is same for two successive readings, the equipment is assumed to be on for 1 hour. The data regarding the temperature and flow is to be collected using thermometers and flow meters.
Data collection has to be done by measuring the current through each machine by a tong tester and taking the reading of the energy meter after every half an hour, one hour etc. The readings of energy meter and the calculated energy are compared. If there is any difference it can be concluded whether the energy meter is fast or slow. Also by this data collection, it can be seen whether the machine is fully loaded or partly loaded.
Equipments used for Data Collection:-
1. Energy meter:-
This meter is of mechanical type, operating on induction principle or nowadays electronic types of energy meters are used. The meters are 3ÃŽÂ¦ or 1ÃŽÂ¦, operated and design to carry specific amount of current. If the system current is higher than this value the energy meter is to be connected through C.T. and for system having high voltages, greater than 500V, P.T. is also required for connection with pressure coil. The meters are integrating type and indicate amount of energy used in a specific time. However the instantaneous energy measurement is not possible using an energy meter. The electromechanical types of instruments are having adjustments and so the frequent calibration is necessary. There are some parts like jewel bearing which are having wear and so the error increases if they are not replaced or adjusted. However they are cheaper, for 1ÃŽÂ¦ it is Rs.350. The accuracy of electronic type energy meters is high and is maintained for a longer time. The reading is in the form of digital display. This meter can store a large data. The data can be accessed as per requirement that is the energy for a particular week or day or hour etc. The cost of 1ÃŽÂ¦ meters is about Rs.1200 which is much more costly as compared to electromechanical type.
2. Clamp on ammeter:-
If energy measurement for a particular machine is required it is necessary to remove the connection of the machine and connect the meter between connecting wires and the machine. It may not be possible always to remove the connection for connecting the meter. Since this will require stoppage of the machine, in such a situation clip on type (tong tester) of ammeter is used. It consists of C.T. whose iron core can be split and placed around the wire through which the current is to be measured. This current generates an alternating flux which links to another coil wounded around same core. An e.m.f. is induced in this current due to alternative flux and the e.m.f. which is proportional to the current measured by electronic circuit and is displayed. Electromechanical types of tong testers are also available but they are bulky and their accuracy is less.
3. Recorder: -
These are the instruments which are used to record a particular quantity for specified time. The recorders are of types: - Circular chart, Strip chart.
i. Circular chart: - These are used for a small period, for example, for a shift or for a day. The recorder may not directly record the energy consumed but they can record the indirect energy quantity, for example, the amount of failures and every instant for a day or for a shift.
ii. Strip chart: - These are in the form of long strip on which X-axis is time and Y-axis is quantity to be recorded. The chart is made up of paper on which the ink pen rests and the position of stylus of ink pen varies according to the quantity to be measured. The chart moves with constant speed driven by synchronous motor. The chart is in the form of graph and the area under the graph is the quantity used in specified time. The sudden changes or continuous increase in the energy are longer time is to be studied. Since it may be related with the bad condition of equipment requiring an immediate maintenance. By using suitable transducer for a current and voltage direct recording of electrical energy is possible.
4. Energy-monitor: -
This is an electronic instrument which is to be connected at the entry of the supply point. If the system current is large it is to be connected through current transformer. The energy monitor is similar to electronic energy meter but having additional facilities like maximum demand, power factor, kVA etc. This unit is having large memory and it is possible to store the record for a longer period. Various types of setting available on the meter like audiovisual alarm, if the parameters like maximum demand, power factor crosses the specified limit. This unit has a facility to continuously display the pattern of consumption of particular parameters, like a record of which can be viewed after some time for interpretation of maintenance are repairing of instrument. The instrument operates using a microprocessor and can also be used for the demand side management which is used in energy conservation. The cost of this unit is around Rs.60, 000 to Rs.75, 000.
5. Tri-vector meter: -
This instrument is capable of measuring kWh, kVAh and maximum demand. The maximum demand which is registered continuously for 30 minutes is recorded. It is possible to calculate the power factor from the reading of kWh and kVAh. The instrument is integrating type like an energy meter and instantaneous recording of the quantity is not possible. After taking the reading of maximum demand for a given time span(day or month), the maximum demand pointer is to be reset to zero position from where the maximum demand for the next time span(which is specified for 30 minutes) is recorded. The recording of maximum demand is also important since the part of energy bill for two part tariff is based on the maximum demand. This data of maximum demand is suitable for implementing demand side management used to reduce their demand charges.
6. Instrument used for temperature measurement: -
When the energy is involved in the process it is necessary to measure the temperature to calculate the heat energy loss, during the specific heat of material and the temperature rise, various types of thermometers operating on various principles are used for these purposes. For accuracy up to 1% mercury thermometers are used. There are suitable up to 350Ã‚ÂºC. These meters based on bimetallic principles are used for a temperature up to 500Ã‚ÂºC. However they are having accuracy about 3 to 5%. For a more accurate reading, nowadays thermometers operating on electrical principle I used, for example, RTD or thermocouples. The output of these devices is given an electronic and the amplifying and measuring circuit. The size of these devices is very small and can be located at a longer distance from the indicator where the reading is taken. It is possible to directly connect the instrument to the recorder. For measuring high temperature from long-distance various types of pyrometers are used. They are suitable to locate the heat losses occurring in large boilers or furnaces.
Â¢ Energy flow diagram: -
To carry out energy audit, the energy flow diagram is helpful. The energy flow diagram indicates the energy input to the system and how it has been divided into various parameters that is losses and useful energy. The energy flow diagram is to be drawn for all types of energy input. For example, electricity, oil, coal etc. The diagram is to be drawn on daily basis or weekly basis or monthly basis indicating the input energy and its division into various parameters. The units of energy should be same for all parameters. For example, if the oil is input the energy unit can be kilocalories. If the diagram is to be drawn for a diesel generator set, although the output is electrical units. The energy flow diagram can be drawn for a small section of the factory or for the total factory or for particular equipment.
The energy flow diagram helps in understanding which observations are to be taken by using various instruments. The diagram is to be drawn indicating the input stage, output stage or useful stage and known losses. The actual figures on the diagram can be entered after taking various observations. In some cases the observations may not be possible and the figures can be entered by previous experience and known data.
The figure can be expressed as percentage that is input as 100%. This type of representation gives the analysis of percentage wastage of energy.
The collected data is to be analyzed to calculate the energy wastage and possible savings.
At the first instant, the accuracy of the energy meter is checked by comparing, the calculated energy used considering the on time of equipments and rating with the meter reading. If there is any error in the energy meter it will get detected in this stage.
The next step in data analysis is related with the loading of the equipments like lamps and fans. This step is not important since they operate at their full capacity. However the machine operating on induction motor, it should be seen whether the motors are utilized for at least 80% of the capacity or not. If the induction motor is lightly loaded i.e. below 70% they are having low power factor. The motor consume higher constant losses as compared with the small motors of small capacity. If the motor is under utilized, the saving and energy wastage is possible by replacing the motors with a lower capacity motor. The data is to be analyzed considering the following points:-
1) Energy required in performing a particular work.
2) The actual energy utilized.
3) The energy wastage considering the inherent energy losses.
From the above analysis it may be possible to suggest various means of energy conservation. It may be suggested to relocate the various motors in the plant so that they operate for at least their 80 % capacity. In some cases, new equipments like new motors or electronic chokes are suggested and pay back period can be calculated.
Payback period = cost of additional equipments - scrap cost of existing equipments
Cost of energy saved per day.
The above equation is without considering any depreciation of new equipment.
In case of A type analysis, since the equipments are consuming more amount of energy, the reduction in energy, is possible by studying the process deeply and an alternative method of operation can be suggested, which is energy efficient. For example in case of forging industry, the heating of billets using furnace oil is the place where
major energy consumption occurs. The process can be replaced by heating using induction heating, which is energy efficient. For A type analysis, the understanding of the product and process along with the cost is necessary. In A type of analysis, the capital cost of the new equipment is much higher and the pay back period is about two and a half to three years, if the equipments are having larger rating and are on for a longer time. Distribution transformer is an example of above type of analysis. This analysis basically involves the production process analysis rather than the operating process analysis, and the alternative method with lower energy content is suggested.
For B type of analysis the equipments are medium energy consumers. About 25% to 35% of the energy consumption can be reduced by modifying the operating procedure. The equipments like ovens, welding transformers, grinders etc. also come under this category. To achieve reduction in energy losses, the process is to be studied and the suggestions are to be given. This type of study does not involve very high capital equipments. Some of the suggestions are as under:-
1) Loading of oven with 80 % capacity.
2) Keeping the vent of the oven closed.
3) Not opening the doors of the oven or cold room frequently.
4) Keeping the equipments like welding transformers or grinders off when not in use.
5) Keeping the lamps and fans off when not required.
In this type, the creating of awareness in the operators and public, in general, is important which can be achieved by displaying the posters, to conserve the energy or keeping water taps closed etc. The operators might be given training for efficient operation of the equipments. In some cases the equipments like automatic converters, time switches for lamps and fans or use of activity sensors can be suggested.
The C type analysis is for the equipments consuming about 10 % to 15 % of energy, and mostly the equipments like lamps and fans should be operated only when required. The means of energy conservation for these equipments except computers are simple and they require less capital cost for energy conservation. Although the payback period for these equipments is around 8 to 10 months, the quantity of energy saved is less as compared to A and B type of equipments.
It can be concluded that as it is not economically feasible to increase generation capacity to cater to the complete demand, we have to adopt energy efficient measures. A general appeal can be made to the public to reduce the energy consumption. Also in industries, if not constructional means then at least the operational means should be adopted which do not require capital investment. This will definitely help in reducing the load shedding which is a great problem for the growing economy. And at last it can be obviously stated that ENERGY SAVED AND ENERGY GENERATED.