GREENING THE GRID - CHALLENGES IN INDIAN · PDF filegreening the grid - challenges in indian power sector - sudip nag , gm(os) , ntpc

GREENING THE GRID -

CHALLENGES IN INDIAN POWER SECTOR

- Sudip Nag , GM(OS) , NTPC

Copyright © 2016 NTPC Limited All Rights Reserved. 2

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

Copyright © 2016 Your Company All Rights Reserved. 3

Action for mitigation of Air & Water Pollution


Global Warming



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


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


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


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


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.


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.


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..


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


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


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


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


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


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.


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


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


Renewable Energy in India 2022

Today58.3 GW

2022175 GW


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


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


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 (%)


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


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)


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


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)


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.


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.


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


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


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)


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:


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.


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


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


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.


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

Email

[email protected]

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