Flexible Operation - Challenges for Thermal Power Plants K B Batra - PowerPoint PPT Presentation

Flexible Operation - Challenges for Thermal Power Plants K B Batra Technical Services, Noida

Total Installed Capacity of India (309244MW) As on 30.11.2016( Source: CEA and MNRE) RES**(MNRE) 15% Nuclear 2% Hydro(Renewable) 14% Coal Oil 61% 0% Gas 8% Coal Gas Oil Hydro(Renewable) Nuclear RES**(MNRE) 16 th Dec 2016 2

BHEL’s Contribution In Indian Power Sector 200000 187802.88 180000 160000 140000 MW CAPACITY 120000 100000 80000 60000 46326.82 43133.43 40000 25282.13 20000 5780 918.89 0 Thermal Nuclear CCPP Diesel Hydro RE All India 187802.88 5780 25282.13 918.89 43133.43 46326.82 BHEL 113264 3340 7560.13 199.42 20149.41 175 TYPE OF POWER PLANTS All India BHEL 16 th Dec 2016 3

Indian Renewable Energy Sector (46326.82 MW) Source: MNRE Waste to Power 0% Solar Power 18% Biomass/Cogneneration 9% Wind Power 62% Small Hydro 11% Wind Power Small Hydro Biomass/Cogneneration Solar Power Waste to Power 16 th Dec 2016 4

Installed RE Capacity Vs. Revised RE Targets A Long Way To Go….. 120000 100000 MW 100000 80000 60000 MW 60000 40000 28279.4 MW 20000 10000 MW 8727.64 MW 5000 MW 4882.33 MW 4323.37 MW 0 Solar Power Wind Power Biomass Small Hydro Installed Capacity (October 2016) Revised Targets(Till 2022) 16 th Dec 2016 5

Share of RE in Future Energy Mix Source: MNRE 16 th Dec 2016 6

Renewable Generation - Challenges  Intermittent and variable  Season and Weather dependent  Location and time of day dependent  Does not match the load demand curve  Wind generation is unpredictable  Solar generation is predictable but non controllable 16 th Dec 2016 7

Integration of Renewable Energy in Grid  Balancing by conventional energy sources (large part of which is thermal) is required  Greater the penetration of RE in Grid greater is the requirement of balancing 16 th Dec 2016 8

Expected All India Duck curve with 20GW Solar Power in Grid 16 th Dec 2016 9

Expectation from Thermal plants  Backing down and cyclic loading  Frequent start/stops may be required  Higher ramping rates during loading and unloading But base load conventional plants are not designed for such cyclic loading. 16 th Dec 2016 10

Start-up of Steam turbines (BHEL make) Start type Outage hours Mean HP Rotor Start-up time temperature (Rolling to full (deg C) load in min. approx) Cold Start 190 hr 150 deg C 255 Warm Start 48 hr 380 deg C 155 Hot Start 8 hr 500 deg C 55 Normal Mode : 2000-2200 starts Slow Mode : 8000 starts Fast Mode : 800 starts 16 th Dec 2016 11

Effect of Load Cycling on Power Plant Components Creep – Slow and continuous deformation of materials due to high temperature exposure even at constant load Thermal Fatigue – Failure of metal when subjected to repeated or fluctuating stresses due to thermal cycling of components Components affected – HP/IP rotors, Blades, Casings, Valves, Header, Y-Piece, T-piece, MS/HRH Pipelines 16 th Dec 2016 12

Life Expenditure of Components Life Time Consumption Fatigue Damage Creep Damage Stress Creep Rupture Strength Operating Steam Operating Type of Mechanical Stress Thermal Stress temperature Stress Material Temperature Steam Pressure Operating Steam Difference inside a inside a thick – thick – walled Pressure walled component component Geometrical Physical properties of a Dimensions of a thick material walled components 16 th Dec 2016 13

Life Expenditure Computation The consumed life of a component is the sum of the life consumed by Creep & Low Cycle Fatigue MINER SUM M C IS INDICATOR OF THE LIFE EXPENDED DUE TO CREEP & MINER SUM M F IS INDICATOR OF THE LIFE EXPENDED DUE TO LOW CYCLE FATIGUE 16 th Dec 2016 14

Life Expenditure Computation FOR STATIONARY COMPONENTS : M = MC + MF = 1 WARNING POINT FOR ROTATING COMPONENTS : M = M C + MF = 0.5 WARNING POINT Approaching the Warning Point of Effective Miner Sum indicates that the life of the component has reached its limit. 16 th Dec 2016 15

Impact of Cycling on Equipment and Operation  Critical components are subjected to thermal stresses which are cyclic in nature  Higher fatigue rates leading to shorter life of components  Advanced ageing of Generator insulation system due to increased thermal stresses  Efficiency degradation at part loads  More wear and tear of components  Damage to equipment if not replaced/attended in time  Shorter inspection periods  Increased fuel cost due to frequent start-ups  Increased O&M cost 16 th Dec 2016 16

Other Operational Risks  Ventilation in HP and LP Turbine at lower loads  Droplet erosion of LP blades  Excitation of LP blades due to ventilation  Frequent start/stop of major auxiliaries (PA/FD/ID fans, BFP) reduces their reliability  Increased risk for pre-fatigued components 16 th Dec 2016 17

Age of Thermal Power Plants In India (in Years) 43357 MW 45000 40000 35000 > 25years, 29549 MW 30000 MW CAPACITY 25000 22610 MW 20000 15000 8359 MW 7780 MW 10000 5630 MW 5000 0 0-5 years 6-10 years 10-15 years 15-20 years 20-25 years > 25years AGE GROUP

Assumed Load Demand Curve on Thermal Machines 120 100% 100 80 % 80% 80 2%/min 3%/min 60 55% 40 20 0 16 th Dec 2016 19

Impact Assessment of Load Cycling  Impact of cyclic operation on BHEL supplied equipment with assumed load curve has been investigated.  Lower load is limited to 55% of rated and a ramp down rate of 2%/min and ramp up rate of 3%/ min. is considered.  It is assumed that main steam and HRH temperatures are kept constant and Unit is operated in sliding pressure mode. 16 th Dec 2016 20

Cyclic Operation - Findings  Preliminary studies indicate that load backing from 100%-55% load at a ramp rate of 2%-3% per minute will not have significant impact on life consumption of Turbine, Boiler, Generator & ESP.  However this mode of operation will have additional cost in terms of lower efficiency at part loads.  Backing down below 55% load and/or increase in ramp rates will have effect on the fatigue life of the equipment.  Backing down below 55% load will also have other negative impacts on the equipment as discussed earlier and need further investigation in detail. 16 th Dec 2016 20

Mitigating the Effect of Cycling  Additional Condition monitoring systems/ Sensors  Improved design of Boiler and Turbine to allow faster ramping and increased number of cycles  Adaptation of Control System  Low cycling regime for older plants (may require RLA)  Replacement of fatigued/ worn-out components  Shorter inspection period 16 th Dec 2016 22

Condition Monitoring for Flexible operation  Complete operation data is available  Continuous online consumption of life expenditure  Detection of highly stressed parts for inspection  Scheduling of RLA  Exploring the margins available for optimization of operating modes  Online monitoring of Generator components as early warning system 16 th Dec 2016 23

Condition Monitoring Systems  Turbine Stress Controller (TSC)  Boiler Stress Monitoring System (BOSMON)  Blade Vibration Monitoring System (BVMS)  Stator End Winding Vibration Monitoring  Rotor Flux Monitoring  Partial Discharge Monitoring  Additional sensors for health monitoring 16 th Dec 2016 24

Renewables integration - Overall impact Thus increased penetration of renewables will lead to  Increased cost due to cycling resulting in higher tariff from conventional sources  Reduced equipment life and thus earlier replacement of plants 25

Renewables integration - Overall impact Thus increased penetration of renewables will lead to  Increased cost due to cycling resulting in higher tariff from conventional sources  Reduced equipment life and thus earlier replacement of plants  Increased CO emissions, partly offsetting the gains from renewables 16 th Dec 2016 26