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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.

March 2015


New Video Shows How NREL is Redefining What's Possible for Renewable Energy on the Grid


Screen capture of YouTube video.

NREL recently launched a three-minute video showcasing some aspects of the lab's work in energy systems integration and how that work is enabling the power system of the future. Check it out on NREL's YouTube channel. The video shows how NREL is spearheading engineering innovations that will help optimize the entire energy system and the how lab's analysis capabilities complement that engineering work by identifying ways to integrate renewable energy effectively and economically.

"The reason we're doing this work is because we see a future in which there's likely to be a lot of renewable energy, and if we're going to go down this path, we want to be sure that we can integrate it in an effective way—both economically and from a reliability point of view," said Power System Analyst Michael Milligan in the video.


Exploring Potential Power Systems Futures


Two recent papers examine potential future power systems that have greater penetrations of renewable and nuclear energy—Rethinking the Future Grid: Integrated Nuclear Renewable Energy Systems and Power Systems of the Future: A 21st Century Power Partnership Thought Leadership Report.

Rethinking the Future Grid: Integrated Nuclear Renewable Energy Systems explores a future in which nuclear and renewable energy sources are tightly coupled in a manner that better optimizes energy use for the combined electricity, industrial manufacturing, and transportation sectors. This "hybrid system" is capable of apportioning thermal and electrical energy to first meet the grid demand (with appropriate power conversion systems), then utilizing excess thermal and, in some cases, electrical energy to drive a process that results in an additional product.

Power Systems of the Future: A 21st Century Power Partnership Thought Leadership Report addresses key forces driving transformation in the power sector around the world, presents a framework for evaluating decisions regarding extent and pace of change, and defines pathways for transformation. The report was jointly written for the 21st Century Power Partnership by authors from NREL, the Joint Institute for Strategic Energy Analysis (JISEA), and several leading energy organizations around the world.

Power Systems of the Future: A 21st Century Power Partnership Thought Leadership Report
Authors: Owen Zinaman, Mackay Miller, Ali Adil, Doug Arent, Jaquelin Cochran, and Ravi Vora; NREL; Sonia Aggarwal, Energy Innovation: Policy and Technology LLC; Minnesh Bipath, South Africa National Energy Development Institute; Carl Linvill, Regulatory Assistance Project; Ari David and Morgan Bazilian, Columbia University; Richard Kauffman, Office of the Governor, New York; Matt Futch, National Grid; Efraín Villanueva Arcos and José María Valenzuela, Secretaría de Energía (SENER), Mexico; Eric Martinot, Institute for Sustainable Energy Policies; Reji Kumar Pillai, India Smart Grid Forum

Rethinking the Future Grid: Integrated Nuclear Renewable Energy Systems (Preprint)
Authors: S.M. Bragg-Sitton and R. Boardman, INL; Mark Ruth and Owen Zinaman, NREL; C. Forsberg, Massachusetts Institute of Technology


NREL Analysis and Analysts in the News


The 2013 Renewable Energy Data Book was the subject of Energy Weekly's article, "NREL releases the 2013 Renewable Energy Data Book, detailing increases in installed capacity," a Triple Pundit article, an EnergyBiz article, and an Energy Industry Today article. It was also mentioned in the Denver Post's article, "Renewable energy generation made steady gains in 2013," and Retrofit Magazine's article, "NREL Renewable Energy Data Book Provides U.S. and Global Energy Statistics."

The 21st Century Power Partnership paper "Making Coal Flexible: Getting from Baseload to Peaking Plant", originally published by Cornerstone, was reprinted by PennEnergy in January. In addition, the paper is now available in Mandarin.

Banking on Solar: An Analysis of Banking Opportunities in the U.S. Distributed Photovoltaic Market was discussed in a GreenTech Media article and in Triple Pundit's "Solar PV: Own or Lease?" To Own or Lease Solar: Understanding Commercial Retailers' Decisions to Use Alternative Financing Models was mentioned in a Buildings article, "Commercial Solar Systems: Own or Lease?" Both of these reports were discussed in a Materials Today article, "The economics of solar photovoltaic systems."

Portions of an interview with Kristen Ardani were aired during NPR's Top of the News Hour with Jeff Brady on February 9 regarding NREL's report, A State-Level Comparison of Processes and Timelines for Distributed Photovoltaic Interconnection in the United States. The report was also the subject of an article in Renewable Energy Focus and an article in PV Magazine.


Recent Publications


Journal Article: Exploring the market for third-party-owned residential photovoltaic systems: insights from lease and power-purchase agreement contract structures and costs in California
Authors: Carolyn Davidson, Dan Steinberg, and Robert Margolis

Based on a sample of 1,113 contracts for residential PV systems installed in 2010–2012 under the California Solar Initiative, this study evaluates the timing of payments under third-party-owned contracts and how it impacts the total cost of the system to the customer.

Journal Article: Retrofitting Fossil Power Plants for Increased Flexibility
Authors: Nikhil Kumar, Intertek AIM; Sundar Venkataraman, GE Energy Consulting; Debra Lew, Greg Brinkman, David Palchak, and Jaquelin Cochran, NREL

To address increased cycling of coal- and gas-fired power plants, and thus, increased wear-and-tear costs for these units, the authors evaluate the operational and cost/benefits of retrofitting power plants for flexibility using a portfolio of generation resources in North America.

Presentation: Social Acceptance of Wind: A Brief Overview
Author: Eric Lantz

Presented at the AWEA State Wind Energy Forum, this piece addresses concepts and trends in social acceptance of wind energy, outlines recent research findings, and discusses mitigation strategies intended to resolve wind power social acceptance challenges as informed by published research and the experiences of individuals participating the International Energy Agencies Working Group on Social Acceptance of Wind Energy.

Presentation: Wind Power Project Repowering: History, Economics, and Demand
Author: Eric Lantz

This presentation, part of a WindExchange seminar, summarizes a related NREL technical report. It seeks to capture the current status of wind power project repowering in the United States and globally, analyze the economic and financial decision drivers that surround repowering, to quantify the level and timing of demand for new turbine equipment to supply the repowering market.

Conference Paper: A Valuation-Based Framework for Considering Distributed Generation Photovoltaic Tariff Design
Authors: Owen Zinaman, NREL; Naïm Darghouth, LBNL

This paper proposes a series of steps that can be taken while designing a distributed generation photovoltaic tariff, utilizing an integrated cost-benefit analysis (CBA) framework. The authors propose a multi-step progression that aims to promote transparent dialogue on CBA study methodologies and assumptions.

Conference Paper: An Overview of the Biomass Scenario Model
Authors: Steve Peterson, Corey Peck, and Dana Stright, Lexidyne LLC; Emily Newes, Danny Inman, Laura Vimmerstedt, David Hsu, and Brian Bush, NREL

This paper reviews some potential ramifications of U.S. government-enacted biomass incentive programs (including subsidies, fixed capital investment grants, loan guarantees, vehicle choice credits, and corporate average fuel economy standards) in order to support policymakers seeking to develop a policy suite which will foster industry development and/or reduce the financial risk associated with government support of the nascent biofuels industry.

Conference Paper: Assessment of New Approaches in Geothermal Exploration
Decision Making (Preprint)

Authors: Akar Sertaç and Kate Young

The aim of this project and paper is to develop and lay out a methodology for more objective geothermal exploration decision making at a given location. The decision analysis in this approach is based on achieving a minimum internal rate of return (IRR) at each phase of a project.

Conference Paper: Life cycle water use for photovoltaic electricity generation: A review and harmonization of literature estimates
Authors: Jordan Macknick, Syndi Nettles-Anderson, Garvin Heath, and Ariel Miara

The authors provide consolidated estimates of water withdrawal and water consumption requirements for the full life cycle of photovoltaic (PV) systems including component manufacturing, power plant construction, system operation, and decommissioning. Compared to other electricity generating technologies, the total life cycle water use for PV systems is lower than all other technologies except for wind technologies.

Conference Paper: Procedure for applying IEC-61853 test data to a single diode model
Authors: Aron Dobos and Sara MacAlpine

Presented at the 40th IEEE Photovoltaic Specialists Conference, this paper proposes modified auxiliary diode model equations along with a procedure to automatically calculate the additional model parameters from test data. The extended single diode model indicates that there is potential to reduce average maximum power point prediction error across a wide temperature and irradiance range by about 75% relative to the baseline five parameter model.

Conference Paper: Validation of multiple tools for flat plate photovoltaic modeling
against measured data

Authors: Janine Freeman, Jonathan Whitmore, Nate Blair, and Aron Dobos

In this study, the authors analyze nine photovoltaic systems' performance data and specifications against forecasts from several PV modeling tools and find that, excluding identified outliers, all tools achieve annual errors within ±8% and hourly root mean squared errors less than 7% for all systems. The authors discuss this range of annual error with regard to irradiance data uncertainty and the use of default loss assumptions, and two avenues are proposed to reduce photovoltaic modeling error.

NREL Report: A State-Level Comparison of Processes and Timelines for Distributed Photovoltaic Interconnection in the United States
Authors: Kristen Ardani, Carolyn Davidson, Robert Margolis, and Erin Nobler

The authors present results from an analysis of distributed PV interconnection and deployment processes in the United States. Using data from more than 30,000 residential (up to 10 kilowatts) and small commercial (10-50 kilowatts) PV systems installed from 2012 to 2014, they evaluated the range in project completion timelines nationally (across 87 utilities in 16 states) and in five states with active solar markets (Arizona, California, New Jersey, New York, and Colorado).

NREL Report: Current Status of Concentrator Photovoltaic Technology
Authors: Simon Philipps and Andreas Bett, Fraunhofer Institute for Solar Energy Systems ISE; Kelsey Horowitz and Sarah Kurtz, NREL

Through an overview of all installations larger than 1 MW, information on companies currently active in the CPV field, efficiency data, and estimates of the LCOE in different scenarios, this report notes that progress in concentrator photovoltaic (CPV) has been achieved, including record efficiencies for modules (36.7%) and cells (46%). Further, the technology may have the potential to be cost-competitive on a levelized cost of energy (LCOE) basis in regions of high direct normal irradiance (DNI).

NREL Report: EPA RE-Powering America's Lands: Kansas City Municipal Farm Site—
Biomass Power Analysis

Authors: Randy Hunsberger and Gail Mosey

Through the RE-Powering America's Land initiative, the authors explore the economic and technical feasibility of utilizing biomass at the Kansas City, Missouri, Municipal Farm site, a group of City-owned properties. The study yielded results indicating that none of the technologies reviewed—biomass heat, power, and CHP—are economically viable options for the Municipal Farms site. However, if the site were to be developed around a future central biomass heating or CHP facility, biomass could be a good option for the site.

NREL Report: Modeling Microinverters and DC Power Optimizers in PVWatts
Authors: Sara MacAlpine and Chris Deline

This document summarizes existing published documents to provide uniform, impartial recommendations for how the performance of distributed power electronics in residential and commercial PV systems can be reflected in NREL's PVWatts calculator.

NREL Report: Reference Model 5 (RM5): Oscillating Surge Wave Energy Converter
Authors: Y.-H. Yu, Scott Jenne, and R. Thresher, NREL; A. Copping, S. Geerlofs, and L.A. Hanna, PNNL

This report contributes the fifth in a series describing Marine HydroKinetic Technology reference models under SAND2013-9040: Methodology for Design and Economic Analysis of Marine Energy Conversion (MEC) Technologies. The RM5 report describes an Oscillating Surge Wave Energy Converter (OSWEC) reference model design, building on Reference Models 1-4 contained in the previous report. It includes the design methodology and numerical simulation results which are used to estimate the device capital costs and the annual operation and maintenance costs.

Fact Sheet: NREL's System Advisor Model Simplifies Complex Energy Analysis
Author: Aron Dobos

NREL's System Advisor Model (SAM) can help decision makers analyze cost, performance, and financing of any size grid-connected solar, wind, or geothermal power project. Manufacturers, engineering and consulting firms, research and development firms, utilities, developers, venture capital firms, and international organizations use SAM for end-to-end analysis; it helps them decide whether and how to make investments in renewable energy projects.


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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.