Management and Organisation of Electricity Use Electrical System Optimisation Belgrade November 2003

Chapter 6 Management and optimisation of electricity use Part I 2 Electrical System Optimisation Content Electrical system otimisation Electricity Tariffs Power Factor Load Management Low Loss Transformers Conclusions Electric motors

Chapter 6 Management and optimisation of electricity use Part I 3 Electrical System Optimisation Electricity Tariffs - Common tariffs General Purpose Tariff Usually is applied to smaller customers, supplied at low voltage. May be  General purpose tariff  General purpose night tariff Service capacity surcharge Usually is applied to customers supplied at 10kV or higher voltages Seasonal tariffs Additionally to day and night tariffs some utilities apply season demand reduction incentives

Chapter 6 Management and optimisation of electricity use Part I 4 Electrical System Optimisation Electricity Tariffs - Common tariffs Maximum Demand Tariff Usually consists of the following components  Demand (kW) - based on “maximum demand” measured  Energy (kWh) - based on the amount of electricity used, the time of the day it is used and the “maximum demand”  Power factor surcharge - when the power factor falls below a specified level

Chapter 6 Management and optimisation of electricity use Part I 5 Electrical System Optimisation Electricity Tariffs - Ways to reduce bills  Reduce consumption by implementing energy efficiency measures  Eliminate Lower Power factor surcharge costs  Transfer load from the day to the night period to reduce both kWh and demand costs  Manage load to minimise maximum demand  Make use of season demand reduction incentives.

Chapter 6 Management and optimisation of electricity use Part I 6 Electrical System Optimisation Power factor

Chapter 6 Management and optimisation of electricity use Part I 7 incoming feeder from meshed power system Principle of power factor correction employing low voltage power capacitors Electrical System Optimisation Power factor

Chapter 6 Management and optimisation of electricity use Part I 8 l The less reactive power a plant consumes, the higher its power factor is, the lower are the power costs of the plant l The transmission costs are less l Updating of distribution system can be avoided Electrical System Optimisation Power factor

Chapter 6 Management and optimisation of electricity use Part I 9 Electrical System Optimisation Power factor

Chapter 6 Management and optimisation of electricity use Part I 10 Electrical System Optimisation Power factor

Chapter 6 Management and optimisation of electricity use Part I 11 l Individual compensation is economic only for large loads with constant power requirements and high duty factor l Centralised compensation is advantageous where u a large number of small loads exists u the loads have varying power requirements u the load have different duty factors Electrical System Optimisation Power factor

Chapter 6 Management and optimisation of electricity use Part I 12 Before Plant power factor 0.7 maximum demand 75 kVA average electrical energy consumption kWh/month Electrical System Optimisation Power factor - Example (Cigarette factory) After Plant power factor 0.95 maximum demand 350 kVA average electrical energy consumption kWh/month Correction - 264kVAr automatic capacitor bank Investment Cost - 4,202 EURO

Chapter 6 Management and optimisation of electricity use Part I 13 l Investment Cost 4,202 EURO l Savings achieved in 1993 was 1, 786 Euro due reduction of maximum demand from 475 to 375 kVAr l Payback Period at 1993 tariffs was 2 years and 4 months Electrical System Optimisation Power factor - Example

Chapter 6 Management and optimisation of electricity use Part I 14 Load scheduling refers to the scheduling of energy loads to maximise benefits through increasing usage at times of cheap energy and vice versa Electrical System Optimisation Load Management Methods of load scheduling : l Production Planning l Alternative fuels and/or plant l Limited overproduction l Pumped storage l Combined heat and power (CHP) and l the simplest SWITCH OFF SOMETHING!

Chapter 6 Management and optimisation of electricity use Part I 15 Electrical System Optimisation Low Loss Transformers  Approximately 3% of all energy generated in industrial countries is used up in magnetising distribution transformers  Amorphous metal transformers (AMT) use 60% to 70% less energy than most efficient silicon steel core transformers  BUT AMT are more expensive than conventional units  The benefits of AMT are extended to reduced pollution of the environment

Chapter 6 Management and optimisation of electricity use Part I 16 Electric Motors Electric motors account for approximately 85% of industrial electricity consumption. Methods of improving motive power efficiency include  Good Housekeeping  Load scheduling  Drive system efficiency  Energy efficient technologies

Chapter 6 Management and optimisation of electricity use Part I 17 Electric Motors Good Housekeeping Switch off all plant that is running unnecessarily using manual timer interlock or load monitoring controls Motors should be sized correctly for their application

Chapter 6 Management and optimisation of electricity use Part I 18 Electric Motors Drive System Efficiency In any drive system the electric motor itself is usually the most efficient element. It may be more effective to improve overall efficiency by examining the complete drive system and its operating patterns

Chapter 6 Management and optimisation of electricity use Part I 19 Electric Motors Energy Efficient Motors EE motors have better quality steel laminations and more active material (steel and copper) to reduce losses, especially the constant losses. EE Motors are more efficient than standard motors at all loads. The savings reach a maximum at about 70% full load - the load at which most industrial motors operate.

Chapter 6 Management and optimisation of electricity use Part I 20 Electric Motors Energy Efficient Motors Comparison of Full Load Efficiencies of Standard and EE 4-Pole Motors

Chapter 6 Management and optimisation of electricity use Part I 21 Electric Motors Energy Efficient Motors Four improvements that contribute to energy efficiency Longer core lengths of low-loss steel laminations ( reduces flux densities and hence iron losses) Maximum utilisation of copper slots and ‘generous’ conductor sizes in the stator and rotor ( reduces copper losses ) Careful selection of slot numbers and tooth/slot geometry ( minimizes stray losses ) Generates less heat so cooling fan size can be reduced ( less wasted power )

Chapter 6 Management and optimisation of electricity use Part I 22 Electric Motors Energy Efficient Motors In comparison with standard motors EE motors are typically 2-5% more efficient (depending on size and loading) have better power factor higher thermal overload margin lower maintenance less sensitive to voltage variations less noisy

Chapter 6 Management and optimisation of electricity use Part I 23 Electric Motors Energy Efficient Motors - Installation Opportunities Energy saving alone do not justify the replacement of existing motors. Always ask motor suppliers to provide efficiency profiles with quotations EE is an option  for new installations  when replacing a burnt-out motor  for duties involving long running hours at high load

Chapter 6 Management and optimisation of electricity use Part I 24 Electric Motors Energy Efficient Motors - Typical Costs

Chapter 6 Management and optimisation of electricity use Part I 25 Electrical System Optimisation Conclusions Main electricity savings are to be found in:  ensuring that the power factor of the site’s loads are above 0.9  ensuring that the supply capacity paid for is no greater than the site needs  ensuring that the load is optimised  minimising the losses in the sites’ transformers  regular scheduled lighting maintenance programme  using high efficiency motors