Best Practices Handbook for the Collection and Use of Solar Resource Data for Solar Energy Applications: Second Edition Edited by Manajit Sengupta,1 Aron Habte,1 Christian Gueymard,2 Stefan Wilbert,3 Dave Renné,4 and Thomas Stoffel5 1 National Renewable Energy Laboratory 2 Solar Consulting Services 3 German Aerospace Center (DLR) 4 Dave Renné Renewables, LLC 5 Solar Resource Solutions, LLC This update was prepared in collaboration with the International Energy Agency Solar Heating and Cooling Programme: Task 46 NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency & Renewable Energy Operated by the Alliance for Sustainable Energy, LLC This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications. Technical Report NREL/TP-5D00-68886 December 2017 Contract No. DE-AC36-08GO28308 Best Practices Handbook for the Collection and Use of Solar Resource Data for Solar Energy Applications: Second Edition Edited by Manajit Sengupta,1 Aron Habte,1 Christian Gueymard,2 Stefan Wilbert,3 Dave Renné,4 and Thomas Stoffel5 1 National Renewable Energy Laboratory 2 Solar Consulting Services 3 German Aerospace Center (DLR) 4 Dave Renné Renewables, LLC 5 Solar Resource Solutions, LLC Prepared under Task No. SETP.10304.28.01.10 NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency & Renewable Energy Operated by the Alliance for Sustainable Energy, LLC This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications. National Renewable Energy Laboratory Technical Report 15013 Denver West Parkway NREL/TP-5D00-68886 Golden, CO 80401 December 2017 303-275-3000 • www.nrel.gov Contract No. DE-AC36-08GO28308 NOTICE This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications. Available electronically at SciTech Connect http:/www.osti.gov/scitech Available for a processing fee to U.S. Department of Energy and its contractors, in paper, from: U.S. Department of Energy Office of Scientific and Technical Information P.O. Box 62 Oak Ridge, TN 37831-0062 OSTI http://www.osti.gov Phone: 865.576.8401 Fax: 865.576.5728 Email: [email protected] Available for sale to the public, in paper, from: U.S. Department of Commerce National Technical Information Service 5301 Shawnee Road Alexandria, VA 22312 NTIS http://www.ntis.gov Phone: 800.553.6847 or 703.605.6000 Fax: 703.605.6900 Email: [email protected] Cover Photos by Dennis Schroeder: (left to right) NREL 26173, NREL 18302, NREL 19758, NREL 29642, NREL 19795. NREL prints on paper that contains recycled content. Foreword for the Handbook Designing, financing, and operating successful solar heating, concentrating solar power, and photovoltaic systems requires reliable information about the solar resource available and its variability over time. In the past, seasonal and daily variability has been studied and understood; however, with new solar technologies becoming more important in energy supply grids, small time-scale effects are critical to successful deployment of these important low carbon technologies. A vital part of the bankability of solar projects is to understand the variability of the solar resource so that supply and storage technologies can be optimized. This handbook is the result of 10 years of international collaboration carried out by experts from the International Energy Agency’s (IEA’s) Solar Heating and Cooling (SHC), Solar PACES, and Photovoltaic Power Systems Technology Collaboration Programmes. Under IEA SHC Task 46: Solar Resource Assessment and Forecasting, experts from 11 countries produced information products and best practices on solar energy resources that will greatly benefit project developers and system operators as well as assist policymakers in advancing renewable energy programs worldwide. Meteorologists, mathematicians, solar technology specialists, and other key solar resource experts from around the world joined forces to further our understanding of the sun’s temporal and spatial variability through benchmarking satellite-derived solar resource data and solar forecasts, developing best practices for measuring the solar resource, and conducting research to improve satellite-based algorithms. The results of IEA SHC Task 46 are useful to a wide range of users of solar heating and cooling, photovoltaics, and concentrating solar power systems and of building developers and owners as well as anyone else who needs to understand and predict sunlight for agricultural or other purposes. The earlier edition of the handbook, which was published in 2015, is used worldwide as a reference for each stage of a solar energy project. Since that time, there has been substantial growth in the interest in high-quality “bankable” solar resource data. This revision adds significant new methods so it will be even more useful. This publication is a summary that details the fundamentals of solar resources as well as captures the state of the art. For those wanting more depth, it also provides the references where more detailed information can be found. I would like to acknowledge the leadership of the National Renewable Energy Laboratory and express appreciation to the U.S. Department of Energy for producing the handbook and incorporating results from IEA SHC Task 46. Ken Guthrie Chair, IEA Solar Heating and Cooling Technology Collaboration Programme June 2017 iii This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications. Preface Dave Renné Dave Renné Renewables, LLC As the world looks for carbon-free sources to meet final energy demand associated with heat, electrical power, and transport, energy from the sun stands out as the single most abundant energy resource on earth. Harnessing this energy is the challenge and opportunity for achieving a carbon-free energy supply by the end of this century. Photovoltaics, solar heating and cooling, and concentrating solar power (CSP) are the primary forms of energy applications using sunlight. These solar energy systems use different technologies, collect different fractions of the solar resource, and have different siting requirements and production capabilities. Reliable information about the solar resource is required for every solar energy application. This holds true for small installations on a rooftop as well as for large solar power plants. However, solar resource information is of particular interest for large installations because it requires a substantial investment, sometimes exceeding $1 billion in construction costs. Before such a project is undertaken, the best possible information about the quality and reliability of the fuel source must be made available. That is, project developers need to have reliable data about the solar resource available at specific locations, including historic trends with seasonal, daily, hourly, and (preferably) sub-hourly variability to predict the daily and annual performance of a proposed power plant. Without these data, an accurate financial analysis is not possible. In response to a meeting of prominent CSP developers and stakeholders hosted by the U.S. Department of Energy (DOE) in September 2008, the National Renewable Energy Laboratory (NREL) produced the first edition of a handbook to provide best practices for the use of solar resource data, which was titled Concentrating Solar Power: Best Practices Handbook for the Collection and Use of Solar Resource Data1. The content was based on the experiences of scientists and engineers from industry, academia, and DOE for identifying the sources, quality, and methods for applying solar and meteorological data to CSP projects. During this same time period, the International Energy Agency’s (IEA’s) Solar Heating and Cooling Programme (SHC) was hosting a task on solar resource knowledge management (Task 36, which ran from 2005– 2011) and then a task on solar resource assessment and forecasting (Task 46, which ran from 2011–2016). These tasks brought together the world’s foremost experts in solar energy meteorology. This group of experts felt the need to create a collective document to disseminate the knowledge that was being developed through these tasks. It was decided that combining the efforts of the experts involved in the IEA tasks to build on the information in NREL’s first version of the handbook would provide the best use of resources and deliver a handbook of outstanding quality to users. It was also decided that additional solar technologies, such as photovoltaics, would be incorporated along with additional aspects of energy meteorology that have become extremely important, such as solar forecasting. As a result, a second edition of the handbook, titled Best Practices Handbook for the Collection and Use of Solar Resource Data for Solar Energy Applications, was published by NREL in 2015. This served as an interim deliverable for Task 46, with the intention of producing a second edition as a final deliverable for the task after the task’s conclusion at the end of 2016. The second edition of the handbook is presented here. 1 https://www.nrel.gov/docs/fy10osti/47465.pdf iv This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.