Integration of renewable energy into the national electricity grid the technical challenges and s (1

Integration of Renewable Energy into the National Electricity Grid Technical Challenges and Solutions Jaquelin Cochran, Ph.D. 16 August 2017 1

Outline • RE integration challenges and need for flexibility • Sources of flexibility • Myths and frequently asked questions about grid integration • Case study: India • Case study: Sri Lanka

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GREENING THE GRID

RE Integration: Challenges and Need for Flexibility

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Grid Operations—A Matter of Balance Supply Supply Components

Demand Components

Conventional Generators

Building End Uses

Renewable Generators

Electric Vehicles

Storage

Storage

Demand

Supply and demand are both variable. The power system keeps these in balance at all times.

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Wind and Solar Add Variability to the Supply Side Load

Net Load

Flexibility: The ability of a power system to respond to change in demand and supply 5

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Integrating Wind and Solar Energy Resources Requires an Evolution in Power System Planning and Operation Renewable energy (RE) is variable, uncertain, and geographically dispersed

‌raising new considerations for grid planning and operations

Replace with Sri Lanka?

1. Balancing requires more flexibility 2. The need for operating reserves can increase 3. More transmission, changes in planning needed 4. Existing thermal assets used less frequently, affecting cost recovery 5. Voltage control, inertia response come at added cost

Source: National Solar Radiation Database (NSRDB)

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GREENING THE GRID

RE Grid Integration: Sources of Flexibility

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Frequently Used Options to Increase Flexibility

Source: Cochran et al. (2014). Flexibility in 21st Century Power Systems.

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Frequently Used Options to Increase Flexibility Low capital cost options, but may require significant changes to the institutional context

• Numerous options for increasing flexibility are available in any power system.

• Flexibility reflects not just physical systems, but also institutional frameworks.

• The cost of flexibility options varies, but institutional changes may be among the least expensive.

Source: Cochran et al. (2014). Flexibility in 21st Century Power Systems.

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Aggregation and Geographic Diversity Can Reduce Variability and Need for Reserves

System Operations

Source: NREL/FS-6A20-63037

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Faster Dispatch Can Reduce Expensive Reserves; Better Alignment with RE Variability Hourly dispatch and interchanges

Source: NREL

System Operations

Sub-hourly dispatch

Dispatch decisions closer to real-time (e.g., intraday scheduling adjustments; short gate closure) reduce uncertainty. Also better alignment with RE forecast confidence.

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RE can be treated like a conventional power plant: removing Services from priority dispatch and requiring grid services from RE Variable RE • RE as a good grid citizen o Visible o Schedulable o Dispatchable o Curtailable o Able to provide ancillary services

• Control technologies for wind and solar are now reflected in PPAs and grid codes • Instead of priority dispatch, address RE financing concerns separate from system operations

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GREENING THE GRID

Myths and Frequently Asked Questions

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Can Grids Support High Levels (>10-20% annually) of Variable RE?

D: MYTHS AND MISPERCEPTIONS

y

Country

%Electricity from Wind

Balancing

42% in in2014 2015 39%

Interconnection, f exible generation (including CHP), and good markets

Portugal

25% 23% in in2013 2015

Interconnection to Spain, gas, hydro, and good market

Spain

19% in in2013 2015 21%

Gas, hydro, and good market

Ireland

23% in in2013 2015 18%

Gasand good market

Denmark

e

ty

Figure 2. Wind penetration levels in select countries. Many countries have already integrated areDenmark: operating variable renewables. high levelsMany of VRE.grids [Sources: Thewith Local.20%–30% (2015). “Danish wind energy hasrecord year.”

The Local Denmark, Science and Technology. January 6, 2015. Others: REN21. Renewables Their demonstrate thatFrance: actions taken to integrate wind and solar are 2014: experiences Global Status Report.

(2014). Paris, REN21] unique to each system, but do follow broad principles. exceed 50%, belying concernsabout Data source: IEA Wind Annual Report for 2015

[4] Milligan, M.; Porter K.; DeMeo, E.; Denholm, P.; Holttinen, H.; Kirby, B.; Miller, N.; Mills, A.;

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Can Variable RE Provide Baseload Power?

Planning that is focused on characteristics needed for flexible operations renders concepts like “baseload” less relevant

Old “Baseload” Paradigm

New Paradigm REN21 2017 15

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Do Individual Renewable Energy Plants Require Backup by Conventional Plants?

• Individual plants do not require backup - Reserves are optimized at system level.

• Wind and solar could increase need for operating reserves.

- But this reserve can usually be provided from other generation that has turned down - This reserve is not a constant amount (depends on what wind/solar are doing) - Many techniques are available to reduce needed reserves.

• Wind and solar can also provide reserves; in both directions when curtailed

Photo from iStock 72283000

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GREENING THE GRID

Case study: Highlights from Recent India RE Grid Integration Study http://www.nrel.gov/india-grid-integration

Lessons from India’s RE Grid Integration Study

Prepared by:

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Grid Integration Studies: Our Purpose

• If India develops 100 GW of solar and 60 GW of wind energy, how would the system operate in 2022? • What can policy makers do to lower the cost of operating this system and better integrate RE? o

Note: Fixed costs considered as sunk cost 20

Methodology Overview

Build an operations model of today’s power system

For future year, forecast load and necessary capacity to meet load

Simulate power system operations in the future year

Greening the Grid uses the PLEXOS production cost model 21

Modeling features • High-resolution wind and solar resource data (both forecasts and actuals) o o

Wind: 5-minute weather profiles for each 3 x 3 km2 area Solar: 1-hour weather profiles for each 10 x 10 km2 area, including impact of aerosols

• Unique properties for each generator • CEA/CTU projections of properties and locations of new lines and power plants for 2022 • Enforced state-to-state transmission flows • Interregional transmission limits that adhere to reliability standards 22

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India’s Power System in 2022—Achieving System Balance Every 15 Minutes (Mac version of video)

• Insert video clip from visualization: https://maps.nrel.gov/IndiaGTG

https://maps.nrel.gov/IndiaGTG 23

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Annual impacts: 175 GW RE can meet 22% of India’s annual electricity demand with minimal RE curtailment

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Daily impacts: Existing flexibility in the coaldominated system can manage RE variability

Load

Net Load

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Retiring 46 GW of coal (20% of coal capacity) may not negatively affect operations Change in coal plant load factors after 46 GW of coal plants are retired

46 GW coal (205 units) operate very little in a high-RE future A system with 175 GW of RE could support some combination of higher demand growth or retirements of generation

Each dot represents one unit

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Strategies for better operation can reduce the cost of RE integration and reduce curtailment Coordinated operations across states

Lower technical minimums for coal plants

RE curtailment

Cost savings

State Scheduling and dispatch

As operated in 2014

70% Technical minimum

INR 6300 crore annually

3.5%

Regional

55%

Scheduling and dispatch

Technical minimum

1.4%

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Priority Takeaways India’s power system has significant latent physical flexibility to integrate 175 GW RE with existing plans Harnessing this flexibility is the key challenge. Need appropriate regulations, markets, incentives...

For example, consider ways at the state level to compensate coal plants for operating flexibly Additional planning could identify optimal locations for new RE and associated interand intrastate transmission

Source: NREL PIX 19498 28

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GREENING THE GRID

Case study: VRE Integration Support to Sri Lankan Power System

Scope of RE Integration Study

Component 1: Dynamic analysis: Impact of solar variability on CEB power system stability Component 2: Short term dispatch modelling

(Highlights are from Component 2)

Development of scenarios

Scenario Medium Dry Wet No VRE

Total Hydro generation over 4 year period (GWh) 24,500 21,100 26,300 24,500

VRE capacity Demand growth Pumped storage plan projections Based on CEB Based on CEB Based on CEB No future VRE

7% 7% 7% 7%

No No No No

7,000

30,000

6,000

25,000

5,000

20,000

4,000

15,000

3,000

10,000

2,000

5,000

1,000 0

0 Dry

Medium

Wet

2016

2017

2018

2019

2020

4 Year Average

4 Year Total

Total Hydro Production (GW)

Hydro Production (GWh)

Hydro Production (GWh)

Summary of results NCRE VRE CO2 penetration (%) curtailment (% emissions Scenario (solar, wind, of total wind (million mini-hydro and and solar tons) biomass) penetration)

CO2 emissions Total system Average savings Average Total system operational costs cost of compared to system wide operative savings compared electricity "no VRE" CO2 emissions costs ($ to "no VRE production scenario (gr/kWh) billion) scenario" ($ ($/MWh) (million tons) billion)

Medium

17.9%

0.0%

33.72

1.84

527.1

2.75

0.37

43.21

Dry

17.9%

0.0%

34.63

0.94

540.5

2.94

0.19

45.99

Wet

17.9%

0.0%

31.96

3.61

499.0

2.39

0.73

37.56

No VRE

9.3%

0.0%

35.57

554.7

3.12

48.83

The results focus on three main areas: • On VRE curtailment: The Sri Lankan grid can effectively absorb the amount of RE that has been proposed so far up to 2020 • On emissions: Integration of around 720MW of new solar and wind generation help reduce emissions by 1.84 million tons by the same year. The average emissions intensity of the grid over the same period will reduce by ~5% • On operational costs: Integration of around 720MW of new wind and solar will reduce system-wide total operative costs by $370 million over the 2017-2020 period

Conclusions • A short-term analysis was performed to identify if the capacity of RE proposed by CEB in the least-cost plan can be effectively absorbed by the Sri Lankan system • The analysis included the development of scenarios to study the effect of hydrology resource on RE penetration levels • The results show that the Sri Lankan grid can effectively absorb the whole amount of RE without having to curtail any amount of VRE generation independently of hydrological conditions • Integration of around 720MW solar and wind capacity have both environmental and economic benefits over the whole system over the 2017-2020 period. Depending on hydrology: • Total CO2 emissions will be reduced by 0.94-3.61 million tons • System wide operational costs with be reduced by $190-730 million

Contact and Additional Information Jaquelin Cochran Ph.D. National Renewable Energy Laboratory Email: Jaquelin.Cochran@nrel.gov

Greening the Grid greeningthegrid.org

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