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Staff Biographies

Learn more about the expertise and technical skills of NREL's concentrating solar power research team and staff by reading our short biographies:

Photo of Victor Castillo

Victor Castillo—Research Technician IV

A.S. Electronics Engineering Technology, ITT Technical Institute

Victor joined NREL in 2011. He designs, fabricates, and assembles prototype test facilities. Victor primarily works with the Concentrated Solar Power group but also works with several other research groups, including Commercial and Residential Buildings, Advanced Optical Materials, and Biofuels.

Victor is also responsible for material testing using the three Ultra Accelerated Weathering Systems located on the NREL mesa top testing facility.

Before coming to NREL, he spent several years in the research and development of fuel cell technology.

Contact information:, 303-384-7476

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Photo of Greg Glatzmaier

Greg Glatzmaier—Senior Engineer II

Ph.D. Chemical Engineering, University of Colorado
B.A. Chemistry, St. Johns University

Greg originally joined NREL in 1987 and worked in the Solar Thermal Program until 1997. During this time, he demonstrated a new concentrating solar technology and initiated a multiyear collaboration with Coors Ceramics Company to develop a high-temperature materials synthesis process. He was awarded three patents for this work.

From 1997 to 2007, Greg operated an R&D small business in which he developed fluid compressor designs and feedback control mechanisms for space applications. This work was funded with several R&D grants from NASA and the U.S. Air Force. He was awarded one patent for this work.

In 2007, Greg rejoined NREL and the Concentrating Solar Power (CSP) team to work on systems analysis, novel heat-transfer fluids, and thermal-storage concepts for CSP technologies. He currently manages the advanced heat-transfer fluids and thermal-storage work at NREL.

Contact information:, 303-384-7470

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Photo of Judith Gomez

Judith Gomez—Engineer IV

Ph.D. Metallurgical and Materials Engineering, Colorado School of Mines
M.S. Materials Engineering, Simon Bolivar University, Venezuela
B.S. Materials Engineering, Simon Bolivar University, Venezuela

Judith joined the Thermal Systems Group in 2010 to work in the field of Concentrating Solar Power (CSP). She is developing coatings to protect containment materials at high temperatures (600°â€“900°C) in molten salts and liquid metal alloys. She is using electrochemical and mass changes techniques to study the degradation behavior of these materials. Judith is also studying new formulations of molten salts and liquid metal alloys as thermal energy storage and advanced heat transfer fluids for CSP systems. She developed a new process in molten-salt electrolysis for which a patent was granted. She holds a volunteer appointment as Research Assistant Professor at Colorado School of Mines, where she serves as an advisor and member on graduate theses committees.

Contact information:, 303-275-4290

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Photo of Matthew Gray

Matthew Gray—Scientist IV

Ph.D. Physics, University of Virginia
B.A. Physics, Carleton College

Matthew joined the Thermal Systems Group at NREL in 2011. He works with the Advanced Optical Materials team to develop improved solar reflectors, solar absorbers and instruments to characterize their performance. The group is interested in developing and benchmarking materials that form part of the low-cost, high-efficiency, and long-lived concentrating solar power plants of the near future. Matthew came to NREL from the photovoltaic industry, where he worked on performance testing, durability, and metrology of flexible copper indium gallium selenide modules. Previously, he worked as a process engineer covering all aspects of high-speed diode laser fabrication, including device design, process development, failure analysis, and performance and lifetime qualification testing. His graduate and postdoctoral work focused on sub-diffraction-limited optical characterization of surface defects in semiconductors and other thin films. Through this work, Matthew has gained expertise in thin-film deposition, material metrology, and optical interactions with surfaces.

Contact information:, 303-275-3917

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Photo of Will Huddleston

Will Huddleston—Undergraduate Intern

B.S. (in progress), Metallurgical and Materials Engineering, Colorado School of Mines

Will joined the Thermal Systems Group in June 2014 as an undergraduate intern. He is a member of the Degradation Mechanisms and Coatings team, primarily studying corrosion behavior of coatings for structural components used for molten salt containment in CSP systems. Before joining NREL, he was involved with electrochemical fuel cell research at the Colorado School of Mines. He is considering the possibility of pursuing a master's degree in materials engineering.

Contact information:, 303-275-3158

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Photo of Katelyn Kessinger

Katelyn Kessinger—Undergraduate Intern

B.S. (in progress) Metallurgical and Materials Engineering, Colorado School of Mines

Katelyn joined the Thermal Systems Group in 2013 to work in the field of Concentrating Solar Power as an undergraduate intern. She is a member of the Advanced Materials team, primarily measuring properties such as the reflectance and transmittance of solar reflectors and absorbers. In 2012, she worked as an intern at the Savannah River National Laboratory, assisting with corrosion and extraction research. She is currently considering the possibility of pursuing a Master's in Materials Science.

Contact information:, 303-384-6419

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Photo of Zhiwen Ma

Zhiwen Ma—Senior Engineer I

Ph.D. Mechanical Engineering, Georgia Institute of Technology
M.S. Thermal Engineering, Tsinghua University
B.S. Thermal Engineering, Tsinghua University

Zhiwen joined the Thermal Systems Group in 2009 to work in the field of Concentrating Solar Power (CSP). His experience includes combustion, fluidization, hydrogen and fuel cells, electronic thermal management and packaging, and gas turbines. He taught in the Department of Engineering Mechanics at Tsinghua University for 3 years, conducted multiphase flow research, and developed pyrometer techniques for measuring gas turbine temperatures. Beginning in 2001, he was a Test and Modeling Engineer in Fuel Cell Energy, and worked on molten carbonate fuel cell performance and life improvement for cost reduction. He was also involved in the Solid State Energy Conversion Alliance program, supporting the testing and modeling of solid-oxide fuel cell stacks and system design.

Zhiwen has published papers and a book chapter, and was awarded two patents in the areas of fuel cells and thermal fluids. Before joining NREL, he worked for GE Aviation on gas turbine flow and heat-transfer design. He works on system analysis, measuring the properties of heat-transfer fluids, and developing thermal-storage concepts for CSP technology.

Contact information:, 303-275-3784

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Photo of Janna Martinek

Janna Martinek—Postdoctoral Researcher

Ph.D. Chemical Engineering, University of Colorado
M.S. Chemical Engineering, University of Colorado
B.S. Chemical Engineering, University of Colorado

Janna Martinek joined the Thermal Systems Group at NREL in 2012 as a postdoctoral researcher. Her work involves developing computational models to evaluate the performance of power tower receiver concepts. For her graduate work, Janna developed models coupling radiative transfer with heat transfer, mass transfer, and chemical reaction kinetics in order to analyze the performance and optimize the geometric configuration of a solar receiver used for high-temperature solar-thermal reaction processes.

Contact information:, 303-275-3779

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Photo of Mark Mehos

Mark Mehos—Thermal Systems Group Manager

M.S. Mechanical Engineering, University of California at Berkeley
B.S. Mechanical Engineering, University of Colorado

Mark joined NREL in 1986 and manages the Thermal Systems R&D group at NREL, which includes the Concentrating Solar Power (CSP) Program. Since 2001, he served as the CSP program manager.

Mark is the leader for the International Energy Agency's SolarPACES "Solar Thermal Electric Power Systems" task, which focuses on the development of international guidelines for modeling and acceptance testing of CSP systems. He has participated on and conducted analysis for several task forces, including New Mexico Governor Richardson's Concentrating Solar Power Task Force, the Solar Task Force for the WGA Clean and Diversified Energy Initiative, and more recently the U.S. Department of Energy's Solar Vision and Renewable Energy Futures studies. He is actively involved in the development of several new grid-integration studies investigating the interaction of CSP systems with thermal energy storage within the western U.S. interconnect.

Contact information:, 303-384-7458

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Photo of Ty Neises

Ty Neises—Engineer II

M.S. Mechanical Engineering, University of Wisconsin-Madison
B.S. Mechanical Engineering, University of Wisconsin-Madison

Ty joined the Thermal Systems group at NREL in 2011. His work focuses on modeling and analyzing the thermal fluid performance of concentrating solar power (CSP) systems and components. His recent work includes researching supercritical carbon dioxide (sCO2) systems for CSP applications and supporting the design of a high-pressure power tower receiver. Ty also develops and supports models for the System Advisor Model.

Contact information:, 303-275-4537

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Photo of Judy C. Netter

Judy C. Netter—Mechanical Engineer III

B.S. Engineering Technology, St. Cloud State University

Judy joined the NREL staff in 1994. Judy is part of the Concentrating Solar (CSP) team and is the primary contact and operator for NREL's High-Flux Solar Furnace, a 10kW solar concentrator. Her expertise involves the design and fabrication of prototype experimental equipment along with the programs and controls. CSP-related projects include the design of experiments and test equipment for characterizing solar collectors, concentrators, and receivers for parabolic troughs, on-sun tests for solar thermochemical reactions (primarily hydrogen production), and recently Solar Power Tower Receiver design. She has also designed multiple secondary concentrators for the Solar Furnace, along with cooling chambers and multiple accelerated weathering chambers for testing the degradation of polymer coatings.

Since joining NREL, Judy has been heavily involved with design and testing in a wide variety of areas, including the condensation of mixed working fluids for geothermal technology; lifetime durability testing of electrochromic windows, thin films, photovoltaic cells, and polymers; thermal management of power electronics as it relates to hybrid vehicles; photocatalysis; and building technologies.

Contact information:, 303-384-6258

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Photo of Teri Spinuzzi

Teri Spinuzzi—Business Support

Teri joined the NREL staff in August 1995. She provides administrative support to the Thermal Systems Group in the Buildings and Thermal Systems Center. Before joining this group, she provided administrative support to the Employment Team in Human Resources, the Deployment Programs Office, and the Technology Transfer Office. Before coming to NREL, Teri provided many years of administrative support to various departments, such as Human Resources, Information Services, and Industrial Hygiene, at the Rocky Flats plant.

Contact information:, 303-384-7425

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Photo of Robert Tirawat

Robert Tirawat—Research Technician III

M.S. (in progress) Material Science, Colorado School of Mines
B.S. Electrical Engineering Technology, Metropolitan State College

Robert joined NREL in 2008 as a student intern for the Advanced Materials team. He has since graduated and was hired as a research technician. Robert helps to develop low-cost, high-performance, high-reliability systems that use concentrated sunlight to generate power. Recently, Robert has been involved developing a high-efficiency solar selective absorber and anti-corrosion coatings.

Contact information:, 303-384-6360

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Photo of Craig Turchi

Craig S. Turchi—Senior Engineer II

Ph.D. Chemical Engineering, North Carolina State University
B.S. Chemical Engineering, Texas A&M University

Craig originally joined NREL in 1990 working in the Solar Industrial Program on the detoxification of hazardous waste with solar ultraviolet light. He returned to NREL in 2008 after spending 10 years as a principal investigator and program leader with ADA Technologies, a technology development company in Littleton, Colorado. While at ADA, Craig served as a principal investigator for projects with the U.S. Environmental Protection Agency, National Institutes of Health, U.S. Department of Defense, U.S. Department of Energy, Electric Power Research Institute, and several private companies. As part of NREL's Thermal Systems team, Craig helps to develop and assess heat-transfer fluids, thermal-storage systems, and power conversion and integrated system concepts. Craig has contributed as task leader for the Concentrating Solar Power Program's Market Transformation activities, which includes technology-enabling issues such as solar resource assessment, cost estimation, land use, environmental impact, and grid integration and transmission.

Contact information:, 303-384-7565

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Photo of Michael Wagner

Michael Wagner—Engineer III

M.S. Mechanical Engineering, University of Wisconsin–Madison
B.S. Mechanical Engineering, University of Wisconsin–Madison

Mike joined the Concentrating Solar Power group at NREL in 2009. His work at NREL includes thermal systems modeling and predictive performance analysis of concentrating solar and power generation systems. Mike has developed several performance models for NREL's System Advisor Model software, including modeling tools for Linear Fresnel, Power Tower, and Parabolic Trough technologies. He is also the developer of a Power Tower layout and optimization tool called SolarPILOT that combines analytical and stochastic methods to define and optically characterize Power Tower solar fields. Mike leads the research and development of a high-temperature solar receiver for super-critical carbon dioxide applications, and he provides expertise in time series analysis of transient and coupled systems, optical and thermal system characterization, computational fluid dynamics, algorithmic optimization, and engineering software development. Before joining NREL, Mike worked as a graduate research assistant at University of Wisconsin–Madison Solar Energy Lab, where he developed an optimization/design tool and detailed transient system component models for power tower technology.

Contact information:, 303-384-7430

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Photo of Tim Wendelin

Tim Wendelin—Senior Engineer II

M.S. Physics, Colorado School of Mines
B.S. Physics Engineering, Colorado School of Mines

Tim began at the Solar Energy Research Institute as a student intern in 1981. He worked primarily on thermoelectric devices in the Materials Research group. Ultimately he became involved with thin-film research as applied to reflective surfaces. He completed his graduate thesis in this field. Tim accepted a regular full-time position at SERI in 1984, working in the Thermal Systems group and has become an expert in optical/thermal modeling and testing of concentrating solar power (CSP) optical systems. He has written or cowritten numerous papers on various aspects of CSP technology and holds three patents and two software copyrights.

Tim has developed a variety of optical and thermal test instruments that characterize the performance of various solar concentrator designs. In addition to instrumentation design, he also developed an optical modeling code, SolTrace, filling a gap in the tool set used by industry to design solar concentrating systems. These instruments and the optical modeling tool have been used extensively at NREL and by industry to further the deployment and operation of CSP technology. He has also served as the technical project manager for several projects at the Solar Technology Acceleration Center, including a 1.25-MW Thermal Energy Storage Test Facility. Tim continues to support optical technology development, optical testing of solar concentrating systems, CSP materials characterization, and CSP systems modeling.

Contact information:, 303-384-7475

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Photo of Guangdong Zhu

Guangdong Zhu—Mechanical Engineer IV

Ph.D. Mechanical Engineering, University of New Mexico
M.S. Thermal Engineering, Xi'an Jiaotong University
B.S. Thermal Engineering, Northeast China Institute of Electric Power Engineering

Guangdong joined the Thermal Systems Group at NREL in 2010 and is working on research and development of Concentrating Solar Power (CSP) technologies. He serves as the primary operator of the Solar Industrial Mesa Test Area, where optical-efficiency testing for parabolic trough collectors is performed. He is also involved in optical and thermal modeling and economic analysis of solar concentrating systems.

Guangdong has an extensive background in power generation systems, heat-transfer processes, and fluid mechanics. He is also well versed in stress analysis, efficient computing, numerical modeling, and related experimental validation. He has written or cowritten peer-reviewed papers, reports, and presentations in the areas of multiphase flow, power generation systems, and solar thermal power.

Contact information:, 303-275-4497

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