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Energy Efficiency in Electrical Systems


2012 IEEE International Conference on Power Electronics, Drives and Energy Systems December16-19, 2012, Bengaluru, India

Energy Efficiency in Electrical Systems
D. Maheswaran
Larsen & Toubro Limited, Chennai, India dmaheswaran@lntecc.com V. Rangaraj raaj@lntecc.com
Abstract—Mitigating climate change and achieving stabilization of greenhouse gas atmospheric concentrations – the objective of the United Nations Framework Convention on Climate Change (UNFCCC) – will require deep reductions in global Energyrelated Carbon Dioxide (CO2) emissions. G-8 leaders called for a 50% reduction in greenhouse gas (GHG) emissions before 2050 to avoid the most serious consequences of climate change. Meeting this goal requires transforming the way energy is produced, delivered, and consumed across all sectors of the economy and regions of the world. Energy efficiency offers seemingly glittering promises to allsavings for consumers and utilities, profits for shareholders, improvements in industrial productivity, enhanced international competitiveness and reduced environmental impacts. As global energy demand continues to grow, actions to increase energy efficiency will be essential. The technical opportunities are myriad and potential savings real, but consumers and utilities have so far been slow to invest in the most cost-effective, energyefficient technologies available. The energy efficiency of buildings, electric equipment, and appliances in use falls far short of what is technically attainable. Energy analysts have attributed this efficiency gap to a variety of market, institutional and technical constraints. Electric utility energy efficiency techniques have great potential to narrow this gap and achieve significant energy savings. This paper provides some of the recent trends in energy efficiency technologies that have been successful and also used widely worldwide. They are: 1) 2) 3) 4) 5) 6) 7) Energy efficient motors Soft starters with energy saver Variable speed drives Energy efficient transformers Electronic ballast Occupancy sensors & Energy efficient lighting controls Energy efficient Lamps

K. K. Jembu Kailas
kkjk@lntecc.com W. Adithya Kumar aadi@lntecc.com
identified large energy efficiency potentials in electric motors and motor systems with many saving options showing very short payback times and high cost-effectiveness. Furthermore, almost all electricity in India is generated by rotating electrical generators, and approximately half of that generated is used to drive electrical motors. Hence, efficiency improvements with electrical machines can have a very large impact on energy consumption. The key challenges to increased efficiency in systems driven by electrical machines lie in three areas: a. To extend the application areas of variable-speed electric drives through reduction of power electronic and control costs b. Secondly, to integrate the drive and the driven load to maximize system efficiency c. Finally, to increase the efficiency of the electrical machine. Lighting is a large and rapidly growing source of energy demand and greenhouse gas emissions. At the same time the savings potential of lighting energy is high, even with the current technology, and there are new energy efficient lighting technologies coming onto the market. Currently, more than 33 billion lamps operate worldwide, consuming more than 2650 TWh of energy annually, which is approximately 19% of the global electricity consumption. The introduction of more energy efficient lighting products and procedures can at the same time provide better living and working environments and also contribute in a cost-effective manner to the global reduction of energy consumption and greenhouse gas emissions Keywords—Energy Efficiency;Energy efficient motors;variable speed drives;energy efficient lighting controls.

I.

INTRODUCTION

This paper presents Case Studies of various energy efficient techniques used in a Steel Plant resulting in considerable Electrical energy savings varying from 10-15%. Electric motors drive both core industrial processes, like presses or roll mills, and auxiliary systems, like compressed air generation, ventilation or water pumping. They are utilized throughout all industrial branches, though the main applications vary. With only some exceptions, electric motors are the main source for the provision of mechanical energy in industry. In recent years, many studies

Energy efficiency refers to the physical performance of specific end uses or energy services such as lighting, heating, cooling, and motor drive. Greater energy efficiency is achieved by replacing, upgrading, or maintaining existing equipment to reduce the amount of energy needed. Energy efficiency is usually measured by the output quantity per unit of energy input (miles per gallon or lumens per watt, for example). Because energy is one of several factors of production (labor, capital, and materials are others), energy efficiency improvements contribute to greater energy productivity and economic efficiency.

978-1-4673-4508-8/12/$31.00 ?2012 IEEE

Efficient use of electricity and changes in the electric power sector will play a vital role in any strategy for achieving a more energy-efficient society. If the threat of global climate change prompts concerted action to reduce carbon emissions, maximizing energy efficiency will be an imperative and a major overhaul of how energy services are provided and paid for will be required on a more accelerated schedule. Utilities & others have consistently found that there are numerous cost-effective opportunities to use electricity more efficiently and to avoid the costs and pollution associated with new plant construction and still have the same energy services, they are:? ? ? ? ? Improvements in the building services. Improvements in the efficiency of electric equipment. Lighting improvements. Net efficiency gains from shifting energy sources from fossil fuels to electricity (electrification). Optimization of electricity use through better energy management control systems, shifts in time of use, and consumer behavior and preference changes.
Fig.2 shows major countries emitting CO2 in 2012

One third of the CO2 emissions in India are due to Electricity generation & Heat as shown in Fig.3

A. Present Scenario in India Demand for power in India has been increasing due to the rising population, growing economy, and changing lifestyles with Coal having the major capacity and major contribution on CO2 emission as shown in Fig.1.

Fig.3 CO2 emissions – Sources in India

B. National Electrical Policy By the end of 2012,Indian National Electricity Policy (2005) aims:
Fig.1 Break-up of installed generation capacity.

? ? ? ? ? ? ?

Per capita availability 1000 units Installed capacity over 200,000 MW Spinning reserves 5% Minimum lifeline consumption of one unit per household per day Inter-regional transmission capacity 37,000 MW Energy efficiency/conservation savings about 15% Quality and reliable power supply.

With the ever increasing demand for power, CO2 emissions are following the increasing trend. As per the statistics taken in September-2012, India alone contributes 6% of the total CO2 emissions in world with Europe, USA & China topping the list as shown in Fig.2.

II.

ENERGY EFFICIENT TECHNOLOGIES IN ELECTRICAL SYSTEMS

As global energy demand continues to grow, actions to increase energy efficiency will be essential. The technical opportunities are myriad and potential savings real, but consumers and utilities have so far been slow to invest in the most cost-effective, energy-efficient technologies available. The energy efficiency of buildings, electric equipment, and appliances in use falls far short of what is technically attainable. Energy analysts have attributed this efficiency gap to a variety of market, institutional and technical constraints. Electric utility energy efficiency techniques have great potential to narrow this gap and achieve significant energy savings. This paper provides some of the recent trends in energy efficiency technologies that have been successful and also used widely worldwide. They are:

This paper provides a detailed study considering a lower bound of 0.75 kW and an upper bound of 200 kW into account the standard power sizes and the new proposed International Electro technical Commission (IEC) 60034 ? 30 efficiency classification standard on motor efficiency as shown in Fig.5.

Fig. 5 Efficiency classes for four?pole motors of standard IE3, IE2 and IE1 classes, and the new IE4 class

IE3 & IE4 Motors have high efficiency at any ambient temperature. Hence these are costly than IE2 Motors. The materials cost of the motor is increased by a few percent. While trying to reduce copper losses, we end up increasing core loss. Hence the starting current of motor is high (approx. 9.24 times including IS tolerance), which increases fault levels and in turn cable size. However these disadvantages are overcome as the payback period for the customer can be as little as six months for a continuously loaded motor. Thus energy-efficient electric motors reduce energy losses through improved design, better materials, and improved manufacturing techniques. Replacing a motor may be justifiable solely on the electricity cost savings derived from an energy-efficient replacement. This is true if the motor runs continuously, power rates are high, the motor is oversized for the application, or its nominal efficiency has been reduced by damage or previous rewinds. Economical benefits and energy savings are illustrated through a Case Study in Chapter-III of this paper. B. Soft Starter with energy savers When starting, AC Induction motor develops more torque than is required at full speed. This stress is transferred to the mechanical transmission system resulting in excessive wear and premature failure of chains, belts, gears, mechanical seals, etc. Additionally, rapid acceleration also has a massive impact on electricity supply charges with high inrush currents drawing +600% of the normal run current. Soft starter provides a reliable and economical solution to these problems by delivering a controlled release of power to the motor, thereby providing smooth, step less acceleration and deceleration. Motor life will be extended as damage to windings and bearings is reduced.

Fig. 4 Energy Efficient Technologies

A. Energy Efficient Motors It is estimated that Electrical Motor-Driven Systems account for between 43% and 46% of all global electricity consumption.

However, as the % loading increases, the % savings decrease. Energy savings are of appreciable quantity only if the time period is more than 5yrs. C. Variable speed drives When discussing energy savings and variable frequency drives (VFD) the attention often focuses on a centrifugal fan or pump application. However, one should not overlook other applications which also have large potential energy savings and energy recovery. Applications involving regeneration, power factor correction, common bus applications or a combination of the three can also quickly achieve a significant reduction in energy use. In variable torque applications, the torque required varies with the square of the speed, and the horsepower required varies with the cube of the speed, resulting in a large reduction of horsepower for even a small reduction in speed. The motor will consume only 12.5% as much energy at 50% speed than at 100% speed as shown in Fig. 6. The following laws illustrate these relationships: ? ? ? Flow is proportional to speed Torque is proportional to (speed)2 Power is proportional to (speed)
3

transformers have increased efficiencies even at low loads 98.5% efficiency at 35% load. E. Electronic Ballast The conventional ballasts make use of the spike caused by sudden physical disruption of current in an inductive circuit to produce the high voltage required for starting the lamp and then rely on reactive voltage drop in the ballast to reduce the voltage applied across the lamp. One of the major advantages of electronic ballast is the enormous energy savings it provides. This is achieved in two ways. The first is its amazingly low internal core loss, quite unlike old fashioned magnetic ballasts. And second is increased light output due to the excitation of the lamp with high frequency. If the period of frequency of excitation is smaller than the light retention time constant for the gas in the lamp, the gas will stay ionized and, therefore, produce light continuously. This phenomenon along with continued persistence of the phosphors at high frequency will improve light output from 8-12%. This is possible only with high frequency electronic ballast F. Occupancy sensors & enery efficient lighting control & Lamps These sensors switch lighting ON when occupancy is detected, and OFF again after a set time period, when no occupancy movement detected. They are designed to override manual switches and to prevent a situation where lighting is left on in unoccupied spaces. With this type of system it is important to incorporate a built-in time delay, since occupants often remain still or quiet for short periods and do not appreciate being plunged into darkness if not constantly moving around. CFL have taken over from incandescent bulbs and the present trend is LED’s which save more energy while providing the same lux levels. Proposed activities: 1. 2. Timer circuits for external locations viz. Coal yard, Coke / Ferrous Stock houses etc are to be provided. Connecting photo sensitive devices to the lighting panels which are operated manually. Reducing operating voltage by adjusting lighting transformer tap( where-ever possible ) Replacement of incandescent lamps by CFL and energy efficient lamps like LED’s. For street lighting applications, implementation of Solar cells & LED’s will result in higher energy saving. To change the timer setting of O&S building Centralized AC so as to switch it OFF earlier during evening peak.

Fig. 6 Power savings using VFD

3. 4. 5.

D. Energy efficient Transformers Most energy loss in dry-type transformers occurs through heat or vibration from the core. The strategy developed to make power available to all by 2012 includes promotion of energy efficient products and its conservation in the country, which is found to be the least cost option to augment the gap between demand and supply. The new amorphous core transformers with high efficiency minimize these losses. The expected reduction in energy loss over conventional (Si Fe core) transformers is roughly around 70%, which is quite significant. By using this amorphous core– with unique physical and magnetic properties- these new types of

6.

III.

CASE STUDY

C. Comparison between Fan and Pump
Parameter Power factor improvement Motor efficiency Reduction Average running time per year Energy saving (MWh/year)
Table. IV Energy Savings with VFD

The following case studies have been performed for a steel plant especially for rolling mills with data collected over a period of 2 years. The following table (Table. I) provides a glimpse energy efficient technologies & suitability along with payback period for equipment where there was scope of energy savings.
Area Motors Energy efficient Technology Energy efficient Motors Soft starters Mill motor Water Pumps Blower pump Lighting VFD VFD VFD Energy efficient control Very Good Very Good Very Good Good 6-8months 6-8months 6-8months 1.5-2yrs Suitability Very Good Payback 1-1.5yrs

FAN (6.6kV) 0.97 96.5% 280kW 5000 hrs. 1400

PUMP (6.6kV) 0.97 97% 219kW 3200 hrs. 700.8

D. Energy Savings with Soft Starters
% Loading 10 20 30 40 50 60 70 % Savings 58 37 20 11 7 4.5 3 2 1.5

Table. I Energy efficient technologies in rolling mills

Energy savings provided here are only for a Fan and Pump. However, the same philosophy has been followed for other motors like conveyors & Mill motors. A. Status without VFD
Parameter Motor Rating Total air flow at full load Flow Fan Speed Current Peak Power Consumption
Table. II Energy without VFD

Measurement FAN (6.6kV) 1760 650TPH 600RPM 182A 1760kW PUMP (6.6kV) 775 10000m3/hr 560RPM 88A 775kW

80 90
Table. V %Energy Savings with Soft Starters

E. Energy Savings with energy efficient Transformers In this case study we considered a iron-steel industry with average electricity loading of 60 MW. About 30 MW of the loading is used at higher voltages (mainly high-voltage motors) and are therefore not distributed by distribution transformers. The electricity consumption is relatively constant during 24 hours a day, 7 days a week. The transformer rating is between 630 kVA and 4000 kVA. There are about 20 transformers. 10 transformers (50%) are 1250 kVA; 25% of the transformers 1600 kVA and 25% other ratings. Almost all transformers are dry-type transformers because of problems in the past with PCB in oil. Most of the transformers have been replaced with Amorphous Core transformers. We evaluated the energy saving between the normal dry-transformers and the amorphous core dry type transformers for the ratings 1250 and 1600 kVA compared with the actual present transformers. If the life cycle of the already existing dry type transformers is exceeded, amorphous core transformer with high efficiency and low losses can replace these existing dry type transformers.

B. Running with VFD
Parameter Motor Rating Total air flow at full load Flow Fan Speed Current Peak Power Consumption
Table. III Status with VFD

Measurement FAN (6.6kV) 1760 650TPH 580RPM 145A 1480kW PUMP (6.6kV) 775 10000m3/hr 490RPM 45A 556kW

Transformer

Unit

Dry type transformer 1250 2400 13568 71241 28,5

Amorphous Core Dry type transformer 1250 2200 11712 62618 25,0

Difference

rating no-load loss load loss Annual losses CO2 emission @ 0,4 kg/kWh Pay back (years)

kVA W W kWh/ a ton/a

-200 -1856 -8623 -3,5 2.5

The intent of this paper is to bring out the salient energy efficient technologies prevailing today. This should not be considered as a guideline for the energy saving for electrical systems. Depending upon the system requirement and usage, the appropriate and most suitable energy efficient methodology can be adopted which doesn’t affect the system performance. REFERENCES
[1] Intergovernmental Panel on Climate Change (IPCC). 2001. IPCC Special Report on the Regional Impacts of Climate Change: An Assessment of Vulnerability. Walters, D. 1999a. Energy Efficient Motors – Saving Money or Costing the Earth? Part 1. IEE Power Engineering Journal, 25–30, February. B. Roisin, M. Bodart, A. Deneyer, P. D’Herdt, Lighting energy savings in offices using different control systems and their real consumption, Energy and Buildings; 40 (2008); p. 514-523. M. Wilson, Saving on Energy, Using lighting efficiently can have a big impact on the bottom line, Chain Store Age; Aug 2008; 84, 8; p.114.

[2] [3]

Table. VI Energy Savings with Energy efficient Transformer

F. Energy efficient lighting controls, Ballasts & Lamps The Combination of Occupancy Sensors & lighting controls resulted in a saving of 27,275kWh per year.
No. Lamps Original system After implement ation of above 1524 1524 of Wattage (kW) 42.786 40.057 kWhr (1day) 213.93 100.285 Annual kWhr 51,344 24,068

[4]

Table. VII Savings with Sensors, efficient lighting Control

The Combination of Occupancy Sensors & New Fittings (energy efficient lamps) resulted in a saving of 38274.9kWh per year with a payback period of 4 years.
No. Lamps Original system After implement ation of above 482 446 of Wattage (kW) 21.584 21.486 kWhr (1day) 213.93 200.285 Annual kWhr 69,173.8 30,898.9

Table. VIII Savings with sensors, energy efficient lamps

IV.

CONCLUSION

India targets 9 – 10% economic growth rate in a sustainable manner over next 10-15 years. Over last 10-15 years, private investments are being encouraged, particularly in petroleum, natural gas and power. While India is fully committed to develop and expand its energy markets, it is equally committed to ensure environmental safeguards. Using latest cost effective technologies in all the energy segments forms an important part of policy and strategy.


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