GREENING THE GRID

GRID INTEGRATION STUDIES: ADVANCING CLEAN ENERGY 

PLANNING AND DEPLOYMENT

Integrating significant variable renewable 

energy (VRE) into the grid requires an evolution 

in power system planning and operation. 

To plan for this evolution, power system 

stakeholders can undertake grid integration 

studies. A grid integration study is an 

analytical framework for evaluating a power 

system with high levels of VRE resources, 

such as solar and wind. A grid integration 

study simulates the operation of the power 

system under different future VRE penetration 

scenarios, identifies reliability constraints, 

and determines the relative cost of actions to 

integrate VRE. Grid integration studies focus at 

the system level, providing policymakers, power 

system operators, and regulators with insights 

about the impacts and solutions associated 

with achieving higher shares of wind and solar 

power in the electricity mix. Example questions 

a grid integration study can answer include:

• What are the tradeoffs among new sites for 

VRE generation and/or transmission to meet 

future demand and achieve VRE targets?

• How will different VRE penetration scenarios 

impact power system operations, emissions, 

and costs? 

• What institutional or operational actions and 

investments are needed to achieve a certain 

VRE penetration target, and what are the 

relative costs of those actions?

• How will different renewable energy 

scenarios impact grid stability following a 

disturbance?

TYPES OF GRID INTEGRATION STUDIES

Grid integration studies fall into three general categories: capacity expansion, production cost, and 

power flow studies, as summarized in Table 1. The choice of which study to implement depends on 

the questions that are most applicable to a power system’s context and priorities.

Capacity Expansion Study Electricity Production Cost Study Power Flow Study

Objective Identify where, when, how much, 

and what types of infrastructure 

(generation and/or transmission) 

would achieve VRE targets at least 

cost, taking into consideration 

factors such as new policies, 

technological advancement, fuel 

prices, and demand projections

Assess the impacts of one or more 

VRE penetration scenarios on bulk 

power scheduling and economic 

dispatch

Test the ability of 

a power system to 

respond to a real-time 

disturbance such as an 

unplanned generator 

or transmission line 

outage 

Simulation 

Horizon

Long term (e.g., 20-50 years) One future year, typically modeled 

at hourly or sub-hourly dispatch 

intervals

Seconds to minutes, 

corresponding to 

periods of system stress

Example 

Outputs

Cost-effective locations for VRE 

and conventional generation 

siting, optimal transmission system 

upgrades and expansion, systemwide capital costs, and economic 

development indicators associated 

with different VRE penetrations and 

configurations

VRE curtailment levels, 

generator ramps and plant load 

factors, reserve requirements, 

emissions and fuel consumption, 

transmission constraints, and 

operational costs associated 

with different VRE scenarios and 

flexibility options; identification 

of periods of high stress to inform 

subsequent testing via power flow 

studies

System recovery time, 

(i.e., magnitude and 

duration of frequency 

deviation following 

a disturbance); 

fault tolerance, 

voltage stability, and 

contingency response; 

mitigation strategies; 

reliability check for 

production cost 

scenarios

Case Study Renewable Energy Futures 

analyzed the extent to which 

renewable energy technologies 

commercially available today can 

meet the electricity demands 

of the continental United States 

through 2030, focusing on an 80% 

renewable energy generation 

scenario [1]

India, Mexico, and the Philippines 

are conducting production cost 

studies to evaluate different 

renewable energy targets and 

identify opportunities to facilitate 

cost-effective wind and solar 

generation (results forthcoming)

Western Wind and Solar 

Integration Study (Phase 

3) used power flow 

analysis to evaluate 

how high penetrations 

of wind and solar 

would impact the 

transient stability and 

frequency response 

of the U.S. Western 

Interconnection [2]

THE ROLE OF A TECHNICAL 

REVIEW COMMITTEE 

A grid integration study that engages a 

broad array of stakeholders contributes to 

robust, credible, and actionable planning 

that reflects industry and policymaker 

concerns. A technical review committee

(TRC) is one mechanism to facilitate 

productive stakeholder engagement in a 

grid integration study. Composed of power 

system policymakers, regulators, operators, 

VRE and conventional plant owners, utilities, 

environmental and public advocates, 

technical experts, and other organizations, 

the TRC provides rigorous peer-review and 

expert input at multiple points throughout 

the execution of a grid integration study. 

The TRC’s roles include determining the 

study objectives and assumptions, defining 

scenarios, reviewing the modeling team’s 

methods and data sources, interpreting and 

validating results, and linking study results 

with policy and regulatory processes. 

While the members of a TRC may not be 

involved in day-to-day modeling and 

analysis, they provide guidance for the core 

modeling team, whose responsibilities 

include assembling and validating input 

data, constructing models, analyzing and 

verifying results, and compiling technical 

documentation to communicate findings. 

The modeling team is typically comprised 

of staff from power system operators, 

energy agencies, and other stakeholders 

with technical expertise in power systems 

or electrical engineering, power flow 

modeling, power system operations, and the 

mechanisms that drive electricity markets.

Table 1: This table summarizes three types of grid integration studies, each addressing 

different questions about the impacts of integrating wind and solar power to the grid. The 

outputs of a grid integration study inform the design and implementation of power system 

policies, regulations, and operations. 
GRID INTEGRATION STUDIES: ADVANCING CLEAN ENERGY PLANNING AND DEPLOYMENT

Greening the Grid provides technical 

assistance to energy system planners, 

regulators, and grid operators to overcome 

challenges associated with integrating 

variable renewable energy into the grid.

FOR MORE INFORMATION

Jennifer Leisch

USAID Office of Global Climate Change 

Tel: +1-202-712-0760

Email: jleisch@usaid.gov

Jaquelin Cochran

National Renewable Energy Laboratory 

Tel: +1-303-275-3766

Email: jaquelin.cochran@nrel.gov

Greening the Grid is supported by the U.S. 

government’s Enhancing Capacity for Low 

Emission Development Strategies (EC-LEDS) 

program, which is managed by the U.S. Agency 

for International Development (USAID) and 

Department of State with support from the 

U.S. Department of Energy, U.S. Environmental 

Protection Agency, U.S. Department of Agriculture, 

and U.S. Forest Service.

greeningthegrid.org | ec-leds.org

NREL/TP-6A20-66504 July 2016 

Written by J. Katz and I. Chernyakhovskiy, 

National Renewable Energy Laboratory

CONDUCTING A GRID 

INTEGRATION STUDY 

Regardless of type, conducting a grid 

integration study involves several iterative 

activities, as illustrated in Figure 1. Collecting 

data on wind and/or solar resources, 

demand, and the characteristics of the 

existing and planned power system is a 

fundamental step that provides modelers 

with the information they need to perform 

the analyses and generate results.1 Scenario 

development articulates the questions of 

greatest interest for the study and should 

be informed by stakeholder input. Typically, 

study scenarios are established in relation to 

a base or business-as-usual case, under which 

policies and operational practices will remain 

relatively unchanged from current practices 

with respect to their treatment of VRE.

Following these foundational actions, 

analysts model the power system under 

different scenarios and perform a variety 

of assessments to appropriately quantify 

costs, reliability, and/or other impacts. 

The development or procurement of an 

appropriate modeling platform (specific to 

capacity expansion, production cost, or power 

flow studies) is an important component 

of this step. The final step is analysis and 

reporting of study results, with the goal of 

providing actionable information to decision 

makers that allows them to translate the 

outputs of a grid integration study into 

effective policy, regulation, and system 

operation. 

Conducting a grid integration study is a 

significant undertaking. The timeframe as 

well as the cost depend on the scope of the 

study, extent of stakeholder engagement, 

data availability, and level of capacity building 

needed to develop modeling expertise. 

Stakeholder engagement throughout 

all phases of a grid integration study will 

help ensure that study assumptions are 

grounded in reality and that the results have 

enough credibility to guide power sector 

transformation [3]. 

FROM STUDY TO ROADMAP

The ultimate goal of a grid integration study is 

to address stakeholder concerns that a power 

system can operate reliably and cost effectively 

under high-VRE scenarios and give decision 

makers the information and confidence they 

need to set and meet ambitious VRE and 

climate change mitigation targets. Based on 

the results of a grid integration study, power 

system planners can prioritize the most costeffective actions to meet their grid integration 

goals, and identify the implementation steps, 

costs, timeframe, and responsible party for 

each action. 

In addition to identifying highest-value 

integration actions, a grid integration study 

will likely raise additional questions that may 

warrant further analysis. Subsequent analyses 

can build on the framework developed for an 

initial study to analyze additional timescales, 

scenarios, and geographic regions or to focus 

on broader energy systems analysis that 

considers the combined impacts of VRE on 

the transmission, distribution, natural gas, and 

transportation systems. With rigorous technical 

oversight and robust stakeholder engagement, 

a grid integration study can serve as a powerful 

long-term tool to guide decision makers in 

planning and implementing well-informed 

renewable energy policies.

REFERENCES

[1] National Renewable Energy Laboratory. 

(2012). Renewable Energy Futures Study. NREL/

TP-6A20-52409.

[2] Miller, N., S. Shao, S. Pajic, and R. D’Aquila. 

(2014). Western Wind and Solar Integration 

Study Phase 3 – Frequency Response and 

Transient Stability. NREL/SR-5D00-62906.

[3] Federal Electricity Regulatory Commission. 

(2016). Staff White Paper on Guidance Principles 

for Clean Power Plan Modeling. Docket No. 

AD16-14-000. 

[4] Holttinen, H., A. Orths, H. Abildgaard, et al. 

(2013). Expert Group Report on Recommended 

Practices (16. Wind Integration Studies). Edited 

by Hannele Holttinen. Technical Report, IEA 

Task 25. 

Create high-quality input data on wind 

and solar proles, electricty demand, and 

power system characteristics

Dene dierent options for the future 

generation eet, transmission network, and 

system operational practices

 Identify impacts of dierent VRE penetration 

scenarios on system reliability and costs, and 

determine cost-eective integration measures

Present results in a way 

that informs decision 

makers

Data Collection

Scenario 

Development

Power System 

Modeling

Analysis and 

Reporting

Stakeholder

Engagement

Figure 1: Several iterative activities are involved in implementing a grid integration study. 

Stakeholder engagement (for example, through a Technical Review Committee) is a crucial 

component throughout each phase of the study. See [4] for a more detailed figure that includes 

decision points and recommended actions for each activity. 

1. See the “Grid Integration Studies: Data Requirements” 

fact sheet for more information about data 

requirements for a grid integration study.