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GREENING THE GRID -
CHALLENGES IN INDIAN POWER SECTOR
- Sudip Nag , GM(OS) , NTPC
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Presentation Outline
Action for mitigation of Air & Water Pollution
New Environment Norms – Issues
Renewable Integration and Its Impact
Flexible Operation and Damage Mitigation
Way Forward
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Action for mitigation of Air & Water Pollution
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Global Warming
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In continuing efforts to safeguard the environment and reduce emissions from power sector, India
has made the following commitments in COP 21:
India intends to reduce the emissions intensity of its GDP by 33 to 35 % by 2030 from 2005 level.
To achieve about 40 percent cumulative electric power installed capacity from non-fossil fuel based
energy resources by 2030 with the help of transfer of technology and low cost international finance.
Introducing new, more efficient and cleaner technologies in thermal power generation.
Further, to reduce emissions from Thermal Power Stations, Ministry of Environment, Forest and
Climate Change has also issued new environmental norms in December 2015 regarding
Suspended Particulate matter (SPM), SOx, NOx, Mercury.
Norms for specific water consumption by Thermal Power Stations have also been notified to
conserve water.
INDIA AIMING EMISSION REDUCTION IN POWER SECTOR
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Change in Environment Norms
Old Norms New Norms
All emission are in mg/ Nm³Installed before
31.12.2003
Installed after 01.01.2004 & up
to 31.12.2016
To be installed
from 01.01.2017
Unit Size All < 500 MW > 500 MW < 500 MW > 500 MW All
SO2
Dispersion
through Chimney600 200 600 200 100
NOx No Norms 600 300 100
SPM 100 100 50 30
Mercury No Norms -- 0.03 0.03 0.03
ESPDe-NOx FGD STACKBOILER
• All plants with once through cooling shall install Cooling Tower And achieve spec water consumption max 3.5M3/MWhr• New plants to be installed after 01.01..2017 shall meets max specific water consumption limit 2.5M3/MWhr And achieve Zero water discharged
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SUSPENDED PARTICULATE MATTER (SPM)
Retro-fitting of additional fields in ESP/ replacement of ESP etc. required to achieve the proposed norms in existing
plants.
There may be space constraints in modification in ESP area in the existing plants. A capacity of around 60 GW (302
Units) may have such space problems while retrofitting equipment to meet revised environmental norms
SULPHUR DIOXIDE (SOx)
FGD system would need to be installed to meet the amended norms regarding SOx control for all categories of existing
plants as well as plants under construction.
Units of less than 500 MW size and some older 500 MW units face layout problems for installation of FGD system due
to non-availability of space.
A capacity of around 90 GW (151 units) of existing plants and 72 GW (73 units) of plants under construction would
require installation of FGD plant.
MAJOR TECHNICAL ISSUES FOR THERMAL PLANTS
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OXIDES OF NITROGEN (NOx)
The proposed standards of 600 mg/Nm3 (302 existing units) would require
modification of the combustion process using low NOx burners
The proposed standards of 300 mg/Nm3 and 100 mg/Nm3 would require
installation of de-nitrification systems like Selective Catalytic Reduction(SCR)
systems
Lay –out issues for installation of DeNOx system in the existing units.
The globally available SCR system for NOx control are not proven for Indian
coal having high ash contents
A capacity of around 120 GW (279 units) of existing plants and 72 GW (73
units) of under construction plants may require installation of SCR systems to
meet new norms.
MAJOR TECHNICAL ISSUES FOR THERMAL PLANTS
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Time Line for implementation of new Environmental Norms
Issues
Retrofitting of many units in the country will be required
There are various issues for implementation like space constraint, relocation of existing
facilities etc.
Overall implementation time for FGD would be around 32 months for one unit. Further,
subsequent units at a interval of 6 months subject to availability of shut down .
Availability of sufficient number of vendors specially for critical bought out items for such
huge capacity.
Huge fund flow in short duration.
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Chimney Height Stipulation
Issues
Tall stacks were stipulated to control the ground level concentration of SO2 and NOx
pollutants though wider dispersion when there was no stack emission standard. Now with
stringent limits of PM, SO2 & NOx Emission, Chimney height stipulation may be relaxed.
Shut down time for Chimney liner will be around 4-6 month. Further, in multiple flue it will be
more.
The longer shut down of 4-6 months for change of liner/ coating in existing chimneys may
be avoided by constructing a new chimney of 150 m height along with FGD Plant.
Separate Chimney of 150 height will give flexibility in layout and avoid long shut down.
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Installation of Cooling tower in all existing units where once through Cooling System provided
Issues
Space constraints for such conversion as it will require large space and in order to create
space, many existing facilities may required to be shifted
Make up water requirement will increase due to more evaporation loss in cooling tower
Such conversion shall result in reduction in around 2% in efficiency thereby increasing the
coal consumption and resulting increase in CO2 emissions.
Installation of cooling tower in one station will necessitate additional make up water system
for some of the station..
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Specific water consumption limit
Issues
Typical water consumption is given on
right
Minimum 2.7 m3/MWhr water is
required without FGD
3.0 m3/MWhr water with FGD will be
required
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SO2 and NOx Emission Implementation for units installed prior to 2003
Issues
Capitalisation of expenditure may be permitted by CERC for units older than 25 years under
“change in law”
Units operational for more than 15 years and remaining life is less than 10 years will be able
to recover the expenditure through tariff
Some units already operational for more than 25 years will continue to deliver cheaper
power for extended period.
Therefore, the units may be permitted to run for minimum 10 years post compliance in order
to recover the cost of environmental compliance
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NOx Emission norms
Issues
Post combustion technologies such as SNCR and SCR may be required for achieving NOx
level of 300 mg/Nm3 for units installed between Dec’2003 – Dec’2016.
These technologies are still not proven for large size furnace and Indian coal
Pilot test for post combustion technologies is underway
Huge quantity of reagent like urea and Ammonia will be required for SNCR for which supply
chain needs to be established
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Gypsum utilization
Issues
Huge quantity around 35 MTPA of gypsum for Indian units (180GW) is expected to be
produced
The limestone available in India may not be suitable for wall board grade gypsum.
Therefore, complete gypsum may not be utilized, and may require additional land for
disposal
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Capex and Opex under Change in law
Issues
Implementation cycle of Environmental norms will require at least 5 yrs time
Capital expenditure for Environment compliance is around 0.8 Crore/MW
Clarity on capitalization and recovery period in general, and units nearing 25 years of
operation in particular is important
With the implementation of New Norms the following may be applicable
Continuous reagent consumption like lime stone, Urea or Ammonia
Auxiliary power consumption will increase around 1.1 to 2.0 %
Additional O&M cost
Shut down period may be considered as deemed availability
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Fund support for implementation of new Environmental Norm
Issues
Huge fund around INR 1.2-1.5 lakh Crore for India will be required for implementation of
new Environmental norms for all plants in a short period
This will severely impact future capacity addition program including renewable capacity for
which we have a high target
The Govt. Of India has recently launched UDAY scheme with an intention to reduce tariff
and also to improve the financial health of DISCOMs. The increase in tariff due to
Environmental norm shall stress the power sector in general and seriously impact the
financial health of DISCOMs.
Fund support from government will ease out tariff burden on DISCOMs.
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Proposed Way forward
Plants having high Station Heat Rate may be phased out. Other plants with better SHR should be allowed
to operate even beyond 25 years, subject to meeting the new environment norms.
Time extension of 5-10 years may be allowed for installation of new Environmental control systems.
Plants retrofitted with systems to comply with new environment norms should be allowed to run for at least
10 years from the date of completion of retrofit, to soften the impact on tariff.
Capitalization of expenditure under change in law may be allowed by CERC for all units which comply with
new environment norms even if they have been operational for more than 25 years.
Shut down period of units should be excluded from the total period for computation of availability for recovery
of fixed costs.
Increase in ECR due to Environment compliance to be excluded for Merit Order determination and early bird
incentive may be introduced to promote faster implementation.
Renewable Integration Plan and its Impact
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RES 58.30, 18%
Gas 25.18, 8%
Diesel0.84 GW
Nuclear 6.78, 2%
Coal193.43
58%
Hydro 44.76, 14%
Total Installed Capacity=310 GW(As on 30.09.2017)
RES
Gas
Diesel
Nuclear
Coal
Hydro
Present Installed Capacity
Small Hydro4.48%
Wind 32.556%
Biomass 8.314%
Solar PV13.1 , 22%
Installed RES=58.30 GW(As on 30.09.2017)
Small hydro
Wind
Biomass
Solar PV
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Renewable Energy in India 2022
Today58.3 GW
2022175 GW
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Variability of Renewable Power
Non variable renewable energy generation refers to sources of electricity that can begenerated at the request of power grid operators or of the plant owner. Since windpower and solar power cannot be controlled by operators, so these are termed as VariableRenewable Energy (VRE) sources.
Renewable Power
Non Variable RE
Biomass Power
Small Hydro <25 MW
Geothermal
Solar with storage
Hybrid Solar Thermal
Variable RE
Wind Power
Solar Power
Tidal Power
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Peculiarities of Variable Renewable power
Difficulty in load frequency control
Difficulty in scheduling of tertiary reserves
Requirement of enhanced transmission network and its under utilisation
Increase in requirement of ancillary services and hence increased system operation cost
Increase in transmission cost due to all above factors
Lower PLF due to ducking of load curve
High ramping requirement
Two shifting and cycling of plants
Increased forced outage and O&M cost
Equipments life time reduction
Poor heat rate and high Aux. Power
Impact on System Impact on existing Plant
Variability
Uncertainty
Geographically Confined
Low inertia
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Today’s Scenario: Cycling without Renewable Integration
0.66 0.63 0.60 0.57
0.10
0.60
1.10
2012 2013 2015 2016
Historical Peak demand met to installed capacity ratio
In last five years, conventional capacity was added
rapidly but in same proportion electricity demand did not
rise, which caused lower PLF and lower peak to installed
capacity ratio.
It is likely to fall further due to rapid addition of RE.77.5 75.1 73.3 69.9 65.6 65.5 62.3 59.6
0
20
40
60
80
100
Historical All India PLF
All India PLF (%)
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Present Net Demand Curve
Present RE Penetration is 15 %of total installed capacity
Peak ramp rate = 222 MW/min
Duck belly demand to peakdemand ratio is approx. 80%
Many units are running on partload resulting in lower PLF ofconventional units
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Future Net Demand Curve (2021-2022)
Installed capacity ~ 523 GW * Peak hour ramp rate is 247
MW/min. Ramping down rate with sun
rise is highest i.e. 368 MW/min.
Duck belly demand to peakdemand ratio is 61% which willlead to partial loading and twoshifting i.e. cycling of fossilbased power plants and hencelow PLF.
Source: CEA
* Based on Draft NEP projections for 2021-22
Impact on Coal/gas based Plant(Flexible Operation and Damage Mitigation)
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Impact of Cycling on Thermal Plants
What is Cyclic operation ?
• Start up/Shut down (Hot/Warm/Cold)
• On load cycling (LL1,LL2,LL3)
• High frequency load variations (RGMO/AGC)
• Thermal fatigue combined withcreep is the main cause of damage.
• Cyclic load variations within SH/RHtemp. control range may betolerable
• Start/stops are the severest in termsof life consumption
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Components Vulnerable to Cycling
Thick wall components Casting such as turbine valves and casings Turbine Rotor Thick walled vessels MS, CRH, HRH headers (especially Y-piece section)
High temperature component Superheater, Reheater Ties used to support SH, RH tubing Tube to header joints etc. Gas duct work
Corrosion and scaling prone component
Water wall tubing at attachments (wind box, corner tubes, wall box opening , buck stay)Heater tube
Condenser tube Welded joints
Degeneration of insulation due to thermal transients
Generator insulation Transformer insulation Insulation of HV drives (FD, ID, PA fans, mills motor)
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Challenges for Conventional Generation
Technical Challenges:
Cyclic operation / Load Ramping capabilities of machines of different age and technology willpose difficulties in dealing with the impact of RE generation variation.
Frequent variation in loading of machine, would affect the residual life of machine. This maylead to
increase in number of break downs of equipments, tube leakage, line leakages, fatigue, creep etc. with impact on R&M cost of machines.
Part load operation would adversely impact the Heat Rate, SOC and APC. Cheap Gas availability is a key issue in providing high ramping Services from Gas fired plants.
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Challenges for Conventional Generation
Commercial Challenges :
Cost of startup fuels,
Auxiliary power Consumption,
O&M / R&M expenses,
Poor efficiency & heat rate etc.
The above will increase the cost of generation and affect merit order position in the highly
competitive power market.
Mitigating Measures:
Generators need to consider cycling cost of such deployment. Such Services should be
properly priced.
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Strategies for Mitigating Flexible Operation Damage
Sliding pressure operation VFD for main cycle and Aux. equipment Stringent water chemistry control
Operation Philosophy
Regular check up of oil guns for light up without delay Reduce start up time by advance preparation
Two shift operating practice
Avoid any such operation which can lead to thermal shock or fatigue like sending cold water in hot economiser
Standby equipments maintained in warm up condition
Avoid wide thermal transients
Natural circulation boilers can be fitted with off load circulating system to eliminate tube to tube temperature difference
Modification for cycling
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Boiler
Steam flow redistribution and metallurgyimprovement in SH/RH
Improvement in selected critical anddegraded expansion joints
Improved material for APH basket making itcapable of operating in wet flue gas region
Automatic pressure control on roll and raceto adjust grinding pressure of mill
Smart soot blowing
Advanced tilt mechanism
Improved automated boiler drains
Introducing ball and tube mills
Flexibilisation : New Design / Modification
Turbine
Turbine heating and electric blankets
Modification to sliding pressure mode
Using Shrink ring on HP inner casing in placeof joint flange bolt Design of HPT
Converting Throttle governing to Nozzlegoverning
Welded rotor design for faster ramp rateand improved startup time
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World Renewable Scenario
*Renewable includes Solar, wind, biomass power and small hydro (<25MW).
(Source : WEC India , Energy Handbook 2016 / IEA 2015 World Energy Outlook)
0% 0%
8% 8% 8%10%
12%
48%
0%
10%
20%
30%
40%
50%
60%
Middle East Russia China United States Japan World India Germany
% In
stal
led
Re
ne
wab
les
Installed Renewable Capacity Percentage Country wise (2015)
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Lessons to learn from Germany
Robust power grids
Flexible operation of coal and nuclear plants (and to a lesser extent gas and
pumped hydro)
Better design of the balancing (ancillary) power markets, to make them more
effective, faster, and open
Better system control software and day-ahead weather forecasting
Modest technical improvements to local-level distribution systems
Exports of power to neighboring countries
With 48% of its installed capacity as RE, Germany has successfully
demonstrated the way to integrate RE into its grid
Although, of late, it has been, experiencing the heat of excessive RE
integration, Success of Germany has been mainly due to:
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Strategy to Improve overall Grid Operation Efficiency
Upgradation of Grid Technology
Upgradation of Grid Protocols
Promote Flexible Demand & Supply
Resource
More and more units should be brought under AGC, so that effective ramp rate requirement onindividual units can be minimised and better load frequency control can be obtained.
Expand Balancing Areas
Power systems, especially those with a high share of RE, require access to sufficient flexibleresources (e.g. gas turbines, hydroelectricity, flexible coal units with AGC etc.) India has 22% oftotal installed capacity of these flexible resources (gas and hydro power).
Scheduling occurs on a day-ahead basis while dispatch occurs on a 15-minute basis. Systemoperations technologies and protocols need to be updated to enable scheduling withautomated incorporation of RE forecasts. This will also lower ancillary service requirements andhence the over all cost to consumer.
Centralized RE forecasting mechanisms need to be tightly integrated with system operations.Advanced decision-making and control systems need to be implemented to enable systemoperators to respond significantly faster to changed grid conditions.
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Market Redesign
For ancillary products– active and reactive power support, frequency regulation, ramp rates, etc.
Time of day metering: In order to promote consumption during RE peaking hours
Incentivizing Storage : Pumped storage, Battery, Molten salt, etc.
Balancing capacity charges for units earmarked for Flexibilisation
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Opportunity loss
Increased breakdown maintenance costs
Loss of useful life
Efficiency loss, increased APC
Environmental costs
Increased chemical, oil and other inputs
Start-up costs
Plant modifications and retrofits
Misc/ unit trips
Market Redesign to ensure security of supply
Additional
CostsMarket Redesign for compensation and
Incentivisation of flexibilisation…….
Reserves Capacity Payment
Negative market price
Pooling
Ancillary services
Peaking Tariff
Impact on Consumers
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The Imperatives
As the all India PLF for dispatchable generation is bound to reduce withrenewable integration, the threshold PLF for fixed cost recovery mayaccordingly be reduced.
Units catering to variable load requirement may be sufficiently compensatedthrough special tariffs.
Cost of VRE is not a true indicator of the cost of electricity to consumerbecause it imposes additional cost on dispatchable generation.
There should be a farsighted policy in picture to ensure the grid stability andreduction of over all system operation cost (grid as well as generating units) inlong run by reducing the extent of cycling on coal based generating stationsas far as possible.
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Conclusion
Large-scale RE has been successfully integrated into gridsworld over
No reported issues due to often talked about PV variability,harmonics, DC current injection, anti-islanding failure orprotection coordination
Energy storage to help in variable generation integration withsignificant RE penetration
Falling prices of PV electricity should not be seen in isolation, itis adding to the cost of conventional electricity (cycling costs,under utilization) and the cost of transmission network
Regulation will have to play a major role in integration of REfor the sake of promoting Green Energy
Sudip Nag
NTPC LTD, Engineering Office Complex
Sector-24 , Noida – 201301, U.P.
Phone
+91 120 2410487