CEATI Hydropower Conference, Tucson, AZ – March 2019 CEATI Hydropower Conference, Tucson, AZ

March 19-20, 2019

Hydropower Value and Opportunities 

in Future Grid States

Presenter:

Michael Ingram

National Renewable Energy Laboratory, Golden, CO, USA

•1
CEATI Hydropower Conference, Tucson, AZ – March 2019

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Agenda

• Project Objectives

• Relevant Power System Metrics

– Stability

– Reliability

– Ancillary Service

– Flexibility

– Economics.

• Hydropower Analysis Studies

• Recommended Future Works.
CEATI Hydropower Conference, Tucson, AZ – March 2019

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Project Objectives

• Infer the value of hydropower based on the impacts and 

requirements identified in the literature review and Grid 

Modernization Laboratory Consortium renewable integration 

studies.

• Analyze the modeled characteristics of hydropower for 

dispatchable and nondispatchable capacity services.
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Stability: Frequency Response

Lacking natural inertia, power systems with large amounts of 

inverter-based technologies might introduce several stabilityrelated issues.

System frequency response to a generator outage

Nadir Nominal Level Frequency

AGC

Droop 

Control

ROCOF

Inertia 

Response

Under Frequency Load Shedding Threshold
CEATI Hydropower Conference, Tucson, AZ – March 2019

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Stability: Transient Stability

High levels of renewable energy might alter transient stability:

• Impact on angle/speed swing bus behavior due to reduced inertia 

• Different power flow patterns (e.g., possible bidirectional flows).

Example response of a substation after an outage event
CEATI Hydropower Conference, Tucson, AZ – March 2019

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Reliability: Black Start

An important reliability consideration for a power system is its ability to be 

restored after a large-scale unplanned outage. Black start requires the ability 

to energize that generation locally without access to external power sources 

(e.g., the grid).

Type of Generator Startup Power [%]

Nuclear 7–8

Thermal 7–8

Gas Turbine 1.5–2

Hydro 0.5–1

The black start of a power 

system can be generally 

categorized into three steps:

• Prepare/plan.

• Re-energize the system 

gradually. 

• Reconnect customers. Summary of black-start energy requirements by generation type

Source: Kulkarni, A.M.. “Power System Restoration,” NPTEL lecture.
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Reliability: Reactive Power Support

• Power systems with large amounts of inverter-based 

technologies might introduce several stability-related issues, 

including maintaining stability-compliant voltage levels.

• Reactive power support is considered an essential reliability 

service.

• Hydropower plants equipped with “traditional” wind turbine 

machines, such as doubly-fed induction generators and selfexcited induction generators, could help fulfill system reactive 

power requirements, and they improve the ability to restore 

system voltage levels in response to disturbances.
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Ancillary Services: Operating Reserves

Operating Reserve

Regulating Reserve Following Reserve Contingency Reserve Ramping Reserve

Manual

(Part of Optimal 

Dispatch)

Instantaneous Automatic

(Within Optimal 

Dispatch)

Nonevent Event

Primary

Secondary

Tertiary

Secondary

Tertiary

Non-Instantaneous

Classification of different types of generic operating reserves

Source: Ela, E., M. Milligan, and B. Kirby. 2011. Operating Reserves and Variable Generation

(NREL/TP-5500-51978). Golden, CO: National Renewable Energy Laboratory, August.
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Ancillary Services

The following table summarizes the percentage contributed to the total 

operating reserve requirement per generation type under high VGs.

Type High Higher 

Baseload Higher VG

Hydropower 32% 32% 32%

Storage 19% 18% 18%

Gas CC 13% 9% 11%

CSP 12% 16% 12%

Wind and PV 11% 13% 14%

Other thermal 8% 7% 7%

Gas CT 3% 3% 4%

Demand Response 2% 2% 2%

Hydropower resources 

can serve up to nearly 

one-third of the 

system operating 

reserve requirements.

Fraction of reserves procured by technology type per high future renewable penetration scenario

Source: Brinkman, Gregory. 2015. Renewable Electricity Futures: Operational Analysis of the Western Interconnection at Very High 

Renewable Penetrations (NREL/TP-6A20-64467). Golden, CO: National Renewable Energy Laboratory, September. 
CEATI Hydropower Conference, Tucson, AZ – March 2019

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Flexibility

The CAISO Duck Chart Source: CAISO 2013

As the solar 

penetration 

increases, 

the net load 

profile 

becomes 

increasingly 

like a “duck” 

shape.

The “duck curve” demonstrates the need for flexibility.
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Economics

An insightful understanding of hydropower costs and economic 

value is required to understand its future role in the U.S. power 

grid.

• Cost:

– Capital and “fuel” costs

– Fixed and variable operation and maintenance costs

– Levelized cost of energy (LCOE).

• Economic value

– Power markets

– Environmental markets.
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Relevant Power System Metrics

Reliability

• Black start

• Reactive power support

Ancillary Service

• Operating reserves

Flexibility

• “Duck” curve

Economics

• Operational costs

• Value

Stability

• Frequency response

• Transient stability
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Scope of Hydropower Analysis Studies

• Renewables Integration Study

Annual generation from 2000 to 2038 Source: EIA Electricity Database

Case Names/

Energy (TWh)

2024-Year 10% Case 2038-Year 30% Case 2038-Year 40% Case

Wind 370.5 954.4 1,495.1

Solar 102.1 433.8 384.5

Conventional Hydro 621.4 653.1 654.9

PSH 169.6 169.6 169.6

Total Energy 4,571.9 4,921.8 4,924.2

Penetration 10.34% 28.21% 38.17%
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Objectives

– Interconnections Seam Study Capacity Review

Regional conventional hydro capacity in SEAMS study

Case 

Names/ 

Capacity 

(GW)

Hydropower Vision 2024-Year 10% 

Case

2038-Year 

30% Case

2038-Year 

40% Case 2015 2050 : 

scenario #1

2050 : 

scenario #2

CHa 79.99 85.27 92.99

84.55

(158.21 b)

84.55

(158.21 b)

84.55

(158.21 b)

PSH 21.60 22.08 57.60 19.37 19.37 19.37

Total 101.59 107.35 150.59

103.92

(177.58 b)

103.92

(177.58 b)

103.92

(177.58 b)
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Limits of Hydropower Analysis Studies

Reliability

• Data are not available

Ancillary Service

• Data are not available

Flexibility

• Statistical analysis on 

conventional 

hydropower and PSH 

operations.

Economics

• Operational costs and 

emission payment (data 

are not available)

• Revenue is based on 

regional prices.

Stability

• Data are not available
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Examples: Model vs. Actual

First week of March at Glen Canyon Dam and Blue Mesa
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Seasonal Flexibility Analysis in 40% Case

Average hourly hydropower and PSH generation, electricity load, and net load by season in SERC and MISO
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Interval-day Flexibility Analysis in 40% Case

PSH energy shifting in SERC and MISO
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Observations: Analysis of Hydropower studies

• The flexibility of hydropower is an important value to help integrate high 

penetration levels of variable generation into the system. 

– Figures of average seasonal flexibility show that conventional 

hydropower and pumped storage hydropower (PSH) follow the net 

load well in the model.

• Load following, variable generation balancing, and energy shifting are 

three ways to see the value PSH provides.

– Generally, PSH shifts energy from off-peak hours to peak hours 

according to market price. 

• Analysis shows that when the variable generation penetration levels 

increase, the hydropower generation profile changes. 
CEATI Hydropower Conference, Tucson, AZ – March 2019

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Observations: Analysis of Hydropower studies

• Hydropower provides not only flexibility but also reserves and economics 

to the system as the variable generation penetration levels increase. 

Flexible hydropower can follow load. 

– Spinning reserves is the only reserves in this modeling. 

• There are two different hydropower operation patterns in PLEXOS:

– Fixed: it follows a historical hourly pattern.

– Optimized: we give the model a max generation, min generation, and 

max production constraint for a time period (usually 1 month) and then 

let the model decide the most optimal way to dispatch the dam based 

on those constraints. 
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Recommended Future Works

• Due to the above-mentioned limitations and observations, there are three 

main future works to complete a comprehensive hydropower analysis:

– Short-term modeling: 

» Flexible Energy Scheduling Tool for Integrating Variable 

Generation (FESTIV)

» Multi-area Frequency Response Integration Tool (MAFRIT).

– Sensitivity analysis with long-term modeling:

» Expansion planning modeling in PLEXOS.

– Water resources capital and “fuel” cost modeling:

» System perspectives (water capital and “fuel” cost)

» Resource perspectives (locational marginal pricing [LMP]).
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Recommended Future Works

• These recommended future works should consider the following research 

questions:

– Is hydropower increasingly in demand, too much or too little?

» New installed capacity could be considered in sensitivity analysis 

(e.g., Hydropower Vision forecast).

» Introduce emerging technologies such as ternary in short-term 

modeling.

– Is it operated differently in these future studies?

» For example, FERC Order 755 requires power system operators to 

compensate hydropower for quick response times. To consider the 

potential benefits to hydropower, future studies should employ 

LMPs instead of general regional prices.
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Recommended Future Works

– Is it operated differently in these future studies? (cont.)

» Additionally, there are pronounced trends of high inertia units 

retiring and not being replaced in kind; short-term modeling is 

needed to analyze the physical response (inertia and governor 

responses) and long-term modeling to incorporate different 

operational constraints.

– Do the same trends affect hydropower as every other fuel type? 

» Prior PLEXOS-based studies do not include “fuel” cost for 

hydropower.
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Q & A

Michael.Ingram@nrel.gov

NREL/PR-5D00-73309

This work was authored by the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, LLC, for the U.S. Department of Energy (DOE) 

under Contract No. DE-AC36-08GO28308. Funding provided by U.S. Department of Energy Office of Energy Efficiency and Renewable Energy Water Power 

Technologies Office. The views expressed in the article do not necessarily represent the views of the DOE or the U.S. Government. The U.S. Government retains 

and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license 

to publish or reproduce the published form of this work, or allow others to do so, for U.S. Government purposes.