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Meeting Transmission 

Challenges in the Rocky 

Mountain Region

Jeff Hein

June 21, 2011

NREL/PR-5500-52000

Western Renewable Energy Zones

Composite photo created by NREL
Presentation Outline

• WREZ Vision;

• Chronology;

• WREZ Initiative Overview;

• Generation and Transmission Model;

• Lessons Learned;

• Future Activities.

National Renewable Energy Laboratory 
WREZ Vision

• Western Governors’ Association and U.S. 

Department of Energy initiated effort to develop 

renewable energy resources and reduce GHG 

emissions.

• Develop a high level “screening tool” to identify 

potential projects that allows industry stakeholders to 

analyze and compare economics of multiple projects.

• Find the high quality, developable renewable 

resource zones (based on NREL data).

• Assume incremental transmission expansion to bring 

generation to load.

• Identify the areas where there are impediments.

National Renewable Energy Laboratory 
• U. S. Utilities Must Install More Renewable Energy Generation

Nine western states have adopted targets for the percent of all electricity 

generation that must come from renewable energy: 

1. Arizona 15% by 2025

2. California 33% by 2020

3. Colorado 30% by 2020

4. Montana 15% by 2015

5. Nevada 20% by 2015

6. New Mexico 20% by 2020

7. Oregon 25% by 2025

8. Utah 20% by 2025 

9. Washington 15% by 2020

WREZ: Why was it developed? 

*Note: British Columbia is seeking renewables for all new generation.

• Western states work together to develop most economical resources 

National Renewable Energy Laboratory 
WREZ Chronology of Events

• 2005-2006 Western Governors’ Association Clean 

and Diversified Energy Initiative;

• 2007 - WREZ Concept Emerges (based largely on 

TX Competitive Renewable Energy Zones effort);

• 2008 – DOE WREZ Grant to WGA;

• 2009 – Transmission Planning FOA funds;

• 2010 – WREZ findings incorporated into 

interconnection-wide transmission planning (WECC).
WREZ Four Phases

• Phase 1: Identify renewable energy zones (REZs), 

estimate quantity of REZ resources, estimate busbar 

cost of REZ resources;

• Phase 2: Develop modeling tool to estimate delivered 

cost of energy from any REZ to any major load center 

in the West; submit scenarios to WECC for detailed 

study; 

• Phase 3: Identify zones of common interest to 

multiple LSEs (foster regional renewable generation 

and transmission projects);

• Phase 4: Institution-building, address transmission 

siting and cost allocation issues.
WREZ Phase 1

• Include all states and provinces in the Western 

Interconnection

• “Filters” applied to eliminate certain land types (national 

parks, urban areas, etc.)

• Areas identified represented large resources, smaller 

areas still show potential for smaller local loads.

– Wind Class Threshold

– Solar DNI Threshold 

• Standard economic assumptions

• Capital cost of each technology

• Capacity factor

• Operation and maintenance costs

• Estimate typical annual production (MWh) - each technology at each 

quality level.
National Renewable Energy Laboratory 

Western Renewable Energy Zones Initiative (WREZ)
Renewable Energy Zones

• A zone has no real boundary. Grid lines do not limit 

development. They are for the analytical purpose of 

estimating resources and deciding how large to build 

the transmission system.

• A hub is the center of a zone. It represents a 

transmission substation where the zone’s resources 

are collected and get onto the grid.

• All of the resources in the vicinity of the hub that 

passed screening are used to estimate the capacity 

available at the hub.
WREZ Phase 2

• Create Generation and Transmission Model 

(GTM) 

• Calculates cost of delivered energy from 54 

zones to 20 load centers in WECC.

• High level “screening tool” that performs a 

simplified economic analysis for quick project 

comparison.

• Easy-to-use spreadsheet downloadable from 

web.

• Anybody can download and use – LSEs, PUCs, 

Industry Stakeholders – and yes your dog.
WECC Load Centers – GTM Screenshot

National Renewable Energy Laboratory 
Resource Selection

National Renewable Energy Laboratory 

• Build resource portfolio 

– Unlimited resources from 5 Zones or less

– Resource energy profile exists and can be viewed (as shown)

– Select zone, then resource
Custom Resource Design – User Defined

• Users can enter custom resources at either generation point or load point.

• Multiple renewable technologies available.

National Renewable Energy Laboratory 
Custom Resource Design – Conventional Generation

• Users can enter custom conventional resources at either generation point 

or load point.

• Multiple technologies available.

National Renewable Energy Laboratory 
Resource Portfolio

• Shows specifics of resource portfolio.

• Graphic representation of energy profile, capacity, and annual energy.

• Specific resources can be removed from portfolio (enter 0 for Cap (MW). 

National Renewable Energy Laboratory 
Identify Incremental Transmission Path(s): REZ(s) to Load

National Renewable Energy Laboratory 

• Select Point-to-Point or Multi-Area Transmission Path(s).

• User may define the route for each resource(s)

Point-to-Point

Multiple-Area

User defined 

Route: Select 

”Click” on 

Segments

Select Resource(s)

Save Route
Selected Transmission Route(s) Design

• Highlighted line segments shown.

• Line segment characteristics can be changed – all blue fields.

• Transmission costs combined with resource portfolio costs to estimate 

project cost.

National Renewable Energy Laboratory 
Project Results – Generation Resource & Transmission 

• Supply curve shows levelized cost of electricity to load from portfolio ($/MWh):

– Detailed resource cost;

– Detailed transmission cost.

National Renewable Energy Laboratory 
Regional Transmission Scenarios

• Zone hubs and their supply curves went into a 

conceptual delivered cost model:

– Excel-based;

– Populated with busbar costs from Phase 1, but 

may be customized to capture user-defined 

projects or scenarios;

– Delivered costs estimated on the basis of 

user-selected load hub and user-selected REZ 

hub;

– Available to load-serving entities and 

regulators to test scenarios.
Western Renewable Energy Zones

•WREZ on the Western 

Governors’ web site:

http://www.westgov.org/wga/ 

initiatives/wrez/

•GIS portal for WREZ 

maintained by NREL:

•http://mercator.nrel.gov/wrez/

– Login “wrez”

– Password “guest”
WREZ Phases 1 & 2 Lessons Learned / Impediments 

• Transmission is the biggest obstacle to installing large 

amounts of new renewable energy generation.

• Wildlife sensitivity analysis did not get developed 

adequately, and is an impediment. Accordingly, this issue 

is not in the Phase 1 report.

• Wildlife issues can overwhelm renewable energy potential.

• The WREZ took on significant importance to developers 

and others.

• In the end, the policies of the individual states can drive 

project outcomes.

National Renewable Energy Laboratory 
WREZ Phase 3 – Identify Zones of Common Interest

• Multiple LSEs may benefit from the same regional 

transmission and REZ(s) project.

• LSE and PUC interviews are completed:

– Regulatory Assistance Project;

– NREL/LBNL.

• Initial finding – local resources sufficient to meet 

RPS requirements.

• Funding under FOA 68, Area of Interest 2, 2010.

National Renewable Energy Laboratory 
WREZ Phase 4 – Fostering Interstate Cooperation

• Develop environment for regional interstate transmission 

and REZ(s) projects. 

• Address policy and regulatory obstacles to interstate 

transmission projects, such as: 

– Siting

• Federal lands, protected lands, sensitive lands, etc.

– Cost allocation

• Energy recipient(s)

• Reliability beneficiary(s)

National Renewable Energy Laboratory 
WREZ General Lessons Learned:

• Most LSEs and states prefer to use in-state/local renewable 

resources due to transmission timing and state economic 

benefits. 

• States with energy export potential want to see G&T 

projects developed in order to bring the resource to market. 

• Disturbed lands with valuable renewable resources should 

be a priority.

• Renewable resources will increase if:

– They are economical or required:

• Greenhouse gas emissions;

• Renewable portfolio standards;

• Price signals;

• Technology breakthrough.

National Renewable Energy Laboratory 
WREZ Continuing Efforts:

• Update wildlife and water issues into the 

generation data. 

• Improve the WREZ model:

– Improved GTM functionality;

– Improved annotation;

– Updated/Improved data (e.g., replacing 50-m wind data 

w/ 80 m).

• Improved DG integration.

• Outreach to LSEs and states.

National Renewable Energy Laboratory 
WREZ Additional Information:

• Data, Presentations, and Reports

– Website at: 

http://www.westgov.org/wga/initiatives/wrez/ind

ex.htm

• Questions?

– Email: jeff.hein@nrel.gov

– 303-384-7090

National Renewable Energy Laboratory 
National Renewable Energy Laboratory Innovation for Our Energy Future

Questions / Comments