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. 4
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. 11
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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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