Energy-Efficient Motor Retrofit Analysis in a Thermal Power Plant: A Case Study

Energy-Efficient Motor Retrofit Analysis in a Thermal Power Plant: A Case Study

Sandeep Singh

‌M.Tech Scholar, Department of Electrical Engineering, MRSPTU Bathinda

Sarbjeet Kaur Bath

Professor, Department of Electrical Engineering, GZSCCET MRSPTU Bathinda

Abstract

This paper presents energy-efficient motors retrofit analysis for low-tension (LT) auxiliary motors at the Lehra Mohabbat Thermal Power Plant (LMTPP), Punjab, India. The study focuses on considering the replacement of aging motors of class IE1 with the class IE4 motors of ABB, in the boiler and clarifier feed pump systems. An audit of motor inventory is conducted to assess their rated powers, load factors, and operational hours. Using nameplate data and catalog values, the analysis has been done to evaluate energy and cost savings and to estimate a simple payback period (SPP). The proposed replacements demonstrate an efficiency improvement between 46%, with estimated energy savings of 562,413 kWh/year and associated annual cost savings exceeding

‌39.09 lakh. CO emission reduction of approximately 461 metric tons/year is projected based on national grid emission factors. The results indicate that transition to IE4 motors is technically feasible, economically justifiable, and environmentally beneficial, particularly in high-duty-cycle systems such as thermal power plant auxiliaries.

Keywords

‌Energy-efficient motors, IE1 motors, IE4 motors, Thermal power plant, Simple payback period (SPP), CO emissions, Motor retrofitting

1. INTRODUCTION

   Electric motors account for a significant portion of industrial electricity consumption worldwide, with estimates indicating over 60% of total industrial energy use attributed to motor-driven systems [1]. In India, thermal power plants rely heavily on low-tension (LT) motors for critical auxiliary operations such as feedwater pumping, fuel handling, flue gas management, and chemical dosing. Many of these motors, especially those commissioned during the 1990s, are based on IE1 efficiency standards or are rewound multiple times, resulting in deteriorated efficiency and increased energy losses.

   To address these challenges, national and international agencies such as the Bureau of Energy Efficiency (BEE), the Central Electricity Authority (CEA), and the International Electrotechnical Commission (IEC) have advocated the adoption of higher efficiency motor classes (IE2, IE3, and IE4) as per IS 12615 and IEC 60034-30-1 [2, 3]. Among these, IE4-class motors represent the highest efficiency segment currently available for industrial deployment. Replacing legacy motors with IE4 alternatives offers a viable pathway to reduce energy consumption, operational costs, and carbon emissions in industrial applications.

   This paper focuses on a real-world case study conducted at the Lehra Mohabbat Thermal Power Plant (LMTPP) in Punjab, India. Stage 1 of the plant, commissioned in 199798, has been selected for motor retrofit analysis, specifically targeting the boiler section and clarifier feed pump system. The study aims to quantify the technical, economic, and environmental impact of replacing aging IE1 motors with

   ABB-manufactured IE4 motors. Key performance metrics such as annual energy and hence cost savings, CO emission reduction and simple payback period (SPP) were calculated using field data and motor catalog specifications.

   The methodology and findings presented in this paper serve as a model framework for similar retrofit interventions in power plants and other energy-intensive sectors.

2. METHODOLOGY

   This study employed a structured four-phase methodology to evaluate the energy-saving potential of retrofitting aging IE1 motors with IE4 motors in a thermal power plant environment. The approach combined field data collection, catalog-based motor selection, and economic analysis using the Simple Payback Period (SPP) model.

   1. Motor Inventory and Data Collection

      The first step involved identifying and documenting the LT motors currently installed in the boiler and clarifier feed pump systems of Stage 1 at the Lehra Mohabbat Thermal Power Plant (LMTPP), Punjab. A total of 207 motors were analyzed, comprising of 167 motors in the boiler section and 40 motors in the clarifier feed system. For each motor, the following parameters were recorded:

      • Rated power (kW)

      • Rated speed (RPM)

      • Rated voltage and current

      • Duty hours (estimated from operational logs)

      • Nameplate efficiency (if available)

      • Number of times the rewinding of motors done (where known)

        This data was cross-referenced with site maintenance records and operator inputs to ensure accuracy.

   2. Selection of Motors for Replacement

      Replacement motors were selected from the ABB IE4 product range. ABBs IE4 motors are compliant with IS 12615:2018 and IEC 60034-30-1, and offer improved performance over legacy IE1 motors. Selection was based on:

      • Power rating equivalence

      • Frame size and mounting compatibility (per IEC 60072)

      • Operational suitability for continuous duty (S1)

      • Environmental protection features (IP55, Class F insulation)

        IE4 motor efficiency values were extracted from ABB's FRSM 66 catalog and consolidated technical brochures [4][5].

   3. Energy and Cost Saving Calculation

      The energy savings obtainable after replacing an IE1 motor with an IE4 motor are estimated using the following formula:

      Energy Saved (kWh/year) = P × LF × (1/_old 1/_new) × H Where:

      P = Rated Power of motor (kW)

      LF = Load factor (0.80 used for estimation) _old = Efficiency of existing IE1 motor _new = Efficiency of proposed IE4 motor H = Annual operating hours

      The corresponding cost saving are calculated using a fixed electricity tariff of 7.00/kWh, the average industrial rate in Punjab.

   4. Economic Feasibility Payback Period

      To assess the economic viability of the retrofit, the Simple Payback Period (SPP) is calculated as: SPP (years) = Initial Investment () / Annual Cost Saving (/year)

      Initial investment included motor procurement costs from ABBs institutional rate list, exclusive of installation costs, which were excluded for conservative estimation.

3. ‌CASE STUDY: LMTPP RETROFIT ANALYSIS

   This case study examines the application of energy-efficient motor retrofitting at Lehra Mohabbat Thermal Power Plant (LMTPP), a coal-based facility located in Bathinda, Punjab, India. The focus is on auxiliary motors in Stage 1, which was commissioned in 199798.

   1. Plant Overview

      The plant consists of multiple stages, with Stage 1 relying heavily on LT motors to drive boiler fans, feedwater pumps, clarifier systems, and other auxiliary machinery. Over two decades of continuous use and multiple rewinding cycles might have led to significant efficiency degradation.

   2. Motor Inventory Analysis

      The audit covered 207 motors: 167 in the boiler section and 40 in the clarifier feed system. Recorded parameters included:

      • Power Rating: 0.75 o 75 kW

      • Speed (RPM)

      • Load factor (assumed 0.80)

      • Operating Hours: 5,000 to 8,000 per year

      • Efficiency deviation estimated from nameplate to actual conditions

   3. IE4 Replacement Strategy

      All motors were mapped to ABBs IE4 series motors based on matching kW, frame size, mounting type, and operating conditions. The goal was to maintain a one-to-one replacement to avoid structural or electrical redesign.

   4. Installation and Integration

      ABB IE4 motors were selected for their:

      • B3 mounting (foot-mounted compatibility)

      • IP55 protection and Class F insulation

      • IEC 60072 standard frame sizes

        This ensured drop-in installation cost without major modifications.

   5. Initial Investment Summary

      As per ABB's FRSM 66 catalogue, the procurement costs were:

      • Boiler Section (167 motors): 39.97 lakh

      • Clarifier Feed Pump Section (40 motors): 20.45 lakh

      • Total Investment: 60.42 lakh

        This investment formed the baseline for evaluating energy savings and payback discussed in the next section.

4. ‌RESULTS AND ANALYSIS

   This section presents the quantifiable outcomes of the motor retrofit analysis, focusing on energy savings, cost benefits, and environmental impact.

   1. Estimation of Energy Savings

      Based on motor audit data and efficiency comparisons between existing IE1 and proposed IE4 motors, the annual energy savings are calculated. The total estimated energy saved across the boiler and clarifier feed systems is:

      • Total Energy Saved: 562,413 kWh/year

   2. Cost Savings and Economic Payback

      Assuming an electricity tariff of 7.00 per kWh, the estimated cost savings are:

      • Annual Cost Savings: 39.09lakh

      • Simple Payback Period (SPP): Ranged from 2.2 to 3.0 years, depending on motor size, runtime, and efficiency differential.

   3. CO Emission Reduction

      Using the Central Electricity Authority (CEA) emission factor of 0.82 kg CO/kWh, the carbon emissions avoided through reduced energy use were calculated:

      • CO Avoided = 562,413kWh × 0.82 kg CO/kWh = 461,179 kg/year ( 461 metric tons)

   4. Maintenance and Reliability Benefits

      In addition to energy and cost savings, IE4 motors are expected to reduce maintenance frequency and improve system reliability. Key advantages include:

      • Reduced rewinding and breakdowns

      • Sealed bearings and better insulation (Class F)

      • Improved thermal and mechanical stability

        These operational benefits further strengthen the case for retrofit adoption in thermal power plant auxiliaries.

5. ‌CONCLUSION AND FUTURE WORK‌

   This section concludes the study and outlines directions for future research and plant-wide implementation.

   1. Conclusion

      This study evaluated the technical, economic, and environmental feasibility of retrofitting aging IE1 motors with energy-efficient IE4 motors at Lehra Mohabbat Thermal Power Plant (LMTPP), Punjab. The case study focused on the boiler and clarifier feed pump systems, analyzing a total of 207 motors.

      Key outcomes include:

      • Estimated energy savings: 562,413 kWh/year

      • Annual cost savings: 39.09 lakh

      • CO emission reduction: 461 metric tons/year

      • Payback period: 2.23.0 years

        These findings affirm that retrofitting with IE4 motors is a viable and impactful energy efficiency strategy.

   2. Future Work

      Although the results are promising, several opportunities for further improvement exist:

      • Expand the analysis to cover the entire LT motor inventory, including coal handling and water treatment systems

      • Use portable data loggers to capture real-time power, current, and load variations

      • Explore the integration of Variable Frequency Drives (VFDs) for load-varying motors

      • Consider Life Cycle Cost Analysis (LCCA) to incorporate depreciation and maintenance escalation

      • Develop a predictive maintenance framework using thermal sensors and energy meters for IE4 motors These steps would improve the accuracy of energy audits and support larger-scale motor optimization programs.

‌REFERENCES

1. Bureau of Energy Efficiency, 'Energy Efficiency in Electrical Utilities,' BEE Guidebook, 2021.

2. Bureau of Indian Standards, IS 12615:2018 Energy Efficient Induction Motors Three Phase Squirrel Cage Specification, 4th Rev., New Delhi, India.

3. International Electrotechnical Commission, IEC 60034-30-1:2014 Efficiency Classes of Line-Operated AC Motors.

4. ABB, 'High Efficiency IE4 Motor Catalogue Consolidated Edition,' ABB India Ltd., 2023.

5. ABB, 'FRSM 66 Price List and Efficiency Data Sheet,' ABB Authorized Dealer, Punjab Region, 2023.

6. Central Electricity Authority, CO Baseline Database for the Indian Power Sector, Version 19, Govt. of India, New Delhi, 2023. [Online]. Available: https://cea.nic.in

‌AUTHOR PROFILE

Sandeep Singh is currently pursuing a part-time Master of Technology (M.Tech) degree in Power Systems from Maharaja Ranjit Singh Punjab Technical University (MRSPTU), Bathinda, Punjab, India. He completed his Bachelor of Engineering (B.E.) in Electrical Engineering from Thapar University, Patiala, as part of the 20112015 batch. He is presently working as a Lecturer in a Polytechnic College under the Punjab State Board of Technical Education. His research interests include energy efficiency and management, applications of energy-efficient motors, and the study of thermal power plant auxiliaries.

CO-AUTHORS PROFILE

Dr. S. K. Bath is currently employed as a professor in Maharaja Ranjit Singh Punjab Technical University (MRSPTU), Bathinda, Punjab, India. She got her PhD degree in Electrical Engg. from Punjab Technical University (presently IKGPTU) Jalandhar in 2009. Her research interests include Electric Power Dispatch Studies, Power System Optimization, Renewable and Hybrid Electrical Power Systems, Energy efficiency and management. She has over 30 years of teaching experience. She has authored over 80 research publications in International and National Conferences, out of which over 40 are in International Journals. She has co-authored one book chapter in an international book. She has also reviewed many research papers for international journals.

‌Appendix A: Motor Inventory Data‌

Appendix A1: Boiler Section Motor Inventory

Annual Saving () per unit piece

‌Appendix A2: Clarifier Feed Pump Motor Inventory‌‌‌