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The Energy Analysis at NREL newsletter highlights the lab's analysts and analysis activities in renewable energy and energy efficiency technologies are having an impact on U.S. energy goals. The newsletter features recent publications and websites, updates to our models and tools, and staff activities. You can subscribe to receive the newsletter monthly by email.

September 2014


PVWatts Updates Interface and Algorithms


The cover of Proceedings of the National Academy of Sciences that features the Harmonization of Initial Estimates of Shale Gas Life Cycle Greenhouse Gas Emissions for Electric Power Generation paper.

On September 8, NREL released an improved version of PVWatts that more accurately reflects PV performance outputs from current systems. Compared with PVWatts Version 1, our new update will predict roughly 7% to 9% greater energy output for a fixed tilt system given similar assumptions. The new results much more closely match measured system performance data, and address concerns that PVWatts Version 1 tended to under-predict PV system performance given the default input assumptions. An updated interface includes changes to handling of losses, inverters, modules, trackers, and sizing.

Nate Blair, Aron Dobos, Jim Vezina, and Rob Eger played significant roles in this upgrade effort.

The popular PVWatts—it is used on average every 40 seconds—is one of numerous models and tools offered or created by NREL to advance understanding of renewable technologies and resources. The NREL-developed HOMER, now distributed and recently updated by HOMER Energy, LLC, has been used by approximately 100,000 people to design and analyze remote off-grid electrical systems in addition to grid-integrated microgrids.


New Report Characterizes Existing Offshore Wind Grid Interconnection Capabilities


Study concludes a three-year collaborative investigation with positive outlooks for U.S.-based offshore wind potential by 2030


A screenshot of the recently updated Laws and Incentives database web page from the State and Local Energy Data website.

The Energy Department has released the first National Offshore Wind Energy Grid Interconnection Study (NOWEGIS), coordinated by experts from ABB, AWS Truepower, Duke Energy, NREL, and the University of Pittsburgh Swanson School of Engineering.

NOWEGIS investigated the key economic and technological factors that will influence the integration of offshore wind energy onto the national grid. NOWEGIS studied the installation of 54 gigawatts (GW) of offshore wind capacity—enough to power nearly 17 million homes—and suggests that the United States has great potential for offshore wind energy resources, and that the appropriate transmission technologies already exist to connect this offshore wind energy to the grid.

Eduardo Ibanez is a lead author of the report, and NREL's Aaron Bloom, Dennis Elliott, Trieu Mai, Michael Heaney, and Lynn Coles served in review and advisory roles on the study.

Read the executive summary and full report.


NREL Analysis and Analysts in the News


"PACE... and the Massachusetts DOER are somewhat fairly similar in their operations. Each program makes use of government support to jump-start the local solar lending market."
—Travis Lowder quoted in an Industry Solar Magazine article titled "Massachusetts Pushes Solar Ownership with Loan Program."

NREL's Eastern Wind Integration and Transmission Study was mentioned in Transmission & Distribution World's article, "Wind Power Can Improve Resiliency of Electrical Grids." Through modeling the country's Eastern Interconnection, the study helped determine that, when equipped with suitable plant controls, wind applications can significantly augment grid resiliency.

The JEDI models were cited in Energy Industry Today's article, "Economic Impacts from Indiana's First 1,000 Megawatts of Wind Power." The scale of the state's available wind resource indicates that wind power infrastructure development has the potential to support millions of dollars of economic activity.

An RE Futures data visualization was featured in Simply Green's article "RMI Blows The Lid Off The 'Baseload Power' Myth." RE Futures investigates how much renewable energy supply can meet the electricity demands of the continental United States over the next several decades.

The Transparent Cost Database was mentioned in a Forbes article, "Which is More Scalable, Nuclear Energy or Wind Energy?" NREL purports a median 40.35% capacity factor for modern wind turbines, and indicates they exceed 50% in the best wind resources.

NREL's LCOE Calculator was mentioned in a Saudi Daily Record article, "Saudi Arabia Could Beat US To Low Cost Solar Punch."

The Energy Information Agency mentioned the Utility Rate Database on OpenEI.org as a helpful source of rate structure information. The citation appeared in the article "Residential electricity prices are rising" in the September 2 issue of EIA's Today in Energy.


Recent Publications


Conference Paper: Representation of the Solar Capacity Value in the ReEDS Capacity Expansion Model (Preprint)
Authors: Ben Sigrin, Patrick Sullivan, Eduardo Ibanez, and Robert Margolis

In this paper, the authors validate treatment of solar photovoltaic (PV) capacity value through use of the Regional Energy Deployment System (ReEDS) capacity expansion model by comparing model results to literature for a range of energy penetration levels. Results from the ReEDS model are found to match up well with both comparisons.


Journal Article: Thin-Film Photovoltaic Power Generation Offers Decreasing Greenhouse Gas Emissions and Increasing Environmental Co-benefits in the Long Term
Authors: Joseph Bergesen, University of California- Santa Barbara; Garvin Heath, NREL; Thomas Gibon, Norwegian University of Science and Technology; Sangwon Suh, University of California–Santa Barbara

Using a hybrid life cycle assessment, the authors compare present and projected environmental, human health, and natural resource implications of electricity generated from two common thin-film PV technologies—copper indium gallium selenide (CIGS) and cadmium telluride (CdTe)—in the United States to those of the current U.S. electricity mix. Results show that, compared to the U.S. electricity mix in 2010, both CIGS and CdTe perform at least 90% better in 7 of 12 and at least 50% better in 3 of 12 impact categories, with comparable land use, and increased metal depletion unless BOS recycling is ensured. Technological changes, particularly efficiency increases, contribute to 35%–80% reductions in all impacts by 2030.


Journal Article: Modeling photovoltaic diffusion: an analysis of geospatial datasets
Authors: Carolyn Davidson, Easan Drury, Anthony Lopez, Ryan Elmore, and Robert Margolis

This study links address-level residential PV adoption trends in California with several types of geospatial information—population demographics, housing characteristics, foreclosure rates, solar irradiance, vehicle ownership preferences, and others—to identify which subsets of geospatial information are the best predictors of historical PV adoption. Results suggest that models trained with small subsets of geospatial information may provide similar explanatory power as models using hundreds of geospatial variables, and that a model trained with data from one state may be applicable in another state.


Journal Article: Transitioning to zero freshwater withdrawal in the U.S. for thermoelectric generation
Authors: Vincent Tidwell, Sandia National Laboratories; Jordan Macknick, NREL; Katie Zemlick and Tibebe Woldeyesus, Sandia Staffing Alliance; Jasmine Sanchez, Colorado School of Mines

The authors, through a scoping level analysis, identify the technical tradeoffs and initial cost estimates for retrofitting existing thermoelectric generation to achieve zero freshwater withdrawal and thus reduce drought related vulnerabilities. The authors find that the estimated impact of retrofits on wastewater and brackish water supply is minimal, requiring only a fraction of the available resource.


Journal Article: Energy Systems Integration: An Evolving Energy Paradigm
Authors: Mark Ruth and Benjamin Kroposki

How energy systems integration is implemented presents a key opportunity in optimally utilizing newly developed technologies and reaching our nation's energy goals.


NREL Report: Reference Manual for the System Advisor Model's Wind Power Performance Model
Authors: Janine Freeman and Jennie Jorgenson, NREL; Paul Gilman and Tom Ferguson

This manual describes NREL's System Advisor Model (SAM) wind power performance model, as well as the algorithms it uses. It is intended to supplement the user documentation that comes with the software. SAM calculates the hourly electrical output of a single wind turbine or of a wind farm and it can be coupled to one of the financial models to calculate economic metrics for residential, commercial, or utility-scale wind projects.


NREL Report: Cacao Intensification in Sulawesi: A Green Prosperity Model Project
Authors: Kristi Moriarty, Michael Elchinger, Graham Hill, Jessica Katz, and John Barnett

This study is one of NREL's eight model projects for Millennium Challenge Corporation's (MCC) Compact with Indonesia under Green Prosperity. It evaluates techniques to improve cacao farming in Sulawesi, Indonesia with an emphasis on Farmer Field Schools and Cocoa Development Centers, and estimates the economic viability of cacao farming if smallholders implement techniques to increase yield as well as social and environmental impacts of the project.


Fact Sheet: Banking on Solar: New Opportunities for Lending
Author: Michael Mendelsohn

This fact sheet discusses bank and credit union lending for solar system deployment and how it represents a valuable new opportunity for lenders to expand their consumer and commercial customer relationships, bring on new relationships, and open a new asset class category.


Fact Sheet: India Solar Resource Data: Enhanced Data for Accelerated Deployment
Lead Author: Sarah Booth

Under a bilateral partnership between the United States and India—the U.S.-India Energy Dialogue—NREL has updated Indian solar data and maps using data provided by the Ministry of New and Renewable Energy (MNRE) and the National Institute for Solar Energy (NISE). This fact sheet summarizes the updated maps and data, which help identify high-quality solar energy projects and can help accelerate the deployment of solar energy in India.


Poster: Wind Technology Modeling Within the System Advisor Model (SAM)
Authors: Janine Freeman, Nate Blair, Aron Dobos, and Johnathan Whitmore, NREL; Tom Ferguson and Paul Gilman

This poster provides detail for implementation and the underlying methodology for modeling wind power generation performance in NREL's SAM. The model calculates the value of projects which buy and sell power at retail rates for residential and commercial systems, and also for larger-scale projects which operate through a power purchase agreement (PPA) with a utility. SAM captures complex financing and rate structures, taxes, and incentives.


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The National Renewable Energy Laboratory (NREL) aims to provide credible, objective data and insights that inform policy and investment decisions as energy efficient and renewable energy technologies advance from concept to commercial application. NREL analysis encompasses a broad range of scientific research and reporting activity in support of the U.S. Department of Energy's (DOE) Office of Energy Efficiency and Renewable Energy (EERE), NREL programs and initiatives, and the analysis community.