Marios Theristis
Principal Member of the Technical Staff
Principal Member of the Technical Staff
Biography
Marios Theristis leads the PV Performance Modeling and PV O&M Analytics programs at Sandia National Laboratories. His work focuses on PV performance modeling and applying data analytics to improve reliability, assess degradation and optimize O&M. He actively engages stakeholders through the PV Performance and Modeling Collaborative and the PV O&M Analytics Collaborative, leading the independent validation of models and tools, and working to establish best practices that minimize uncertainty and improve transparency across the industry.
Prior to joining Sandia National Laboratories in 2019, he was at the University of Cyprus, Cyprus (2016-2019), the University of Jaén, Spain (2016), Fraunhofer CSE, USA (2015), and NCSR “Demokritos,” Greece (2010-2011). Marios received his Dipl.-Ing. in Electrical and Computer Engineering from Democritus University of Thrace, Greece (2011), and his PhD from Heriot-Watt University, UK (2016).
Publications
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Micheli, L., Muller, M., Theristis, M., Smestad, G.P., Almonacid, F., Fernandez, E.F., & Fernandez, E.F. (2024). Quantifying the impact of inverter clipping on photovoltaic performance and soiling losses. Renewable Energy, 225. https://doi.org/10.1016/j.renene.2024.120317 Publication ID: 124252
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Deville, L., Theristis, M., King, B.H., Chambers, T.L., Stein, J.S., & Stein, J.S. (2024). Open-source photovoltaic model pipeline validation against well-characterized system data. Progress in Photovoltaics: Research and Applications, 32(5), pp. 291-303. https://doi.org/10.1002/pip.3763 Publication ID: 122540
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Dhimish, M., Theristis, M., D’Alessandro, V., & D’Alessandro, V. (2024). Photovoltaic hotspots: A mitigation technique and its thermal cycle. Optik, 300(NA). https://doi.org/10.1016/j.ijleo.2024.171627 Publication ID: 122596
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Micheli, L., Muller, M., Theristis, M., Smestad, G., Almonacid, F., Fernandez, E., & Fernandez, E. (2024). Inverter clipping and its masking effect on PV soiling: truth or myth? [Conference Poster]. https://doi.org/10.2172/2335911 Publication ID: 124432
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Driesse, A., Gallon, J., Kopidakis, N., Theristis, M., Stein, J.S., & Stein, J.S. (2024). Tools and Techniques for Spectral Irradiance Processing and Mismatch Estimation [Conference Poster]. https://doi.org/10.2172/2293598 Publication ID: 122716
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Micheli, L., Theristis, M., Ltalavera, D., Nofuentes, G., Stein, J.S., Almonacid, F., Fernandez, E., & Fernandez, E. (2024). The economics of photovoltaic performance and loss mitigation in electricity spot markets [Conference Poster]. https://doi.org/10.2172/2293595 Publication ID: 122712
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Theristis, M., Anderson, K.S., Ascencio-Vasquez, J., Stein, J.S., & Stein, J.S. (2024). How Climate and Data Quality Impact Photovoltaic Performance Loss Rate Estimations. Solar RRL, 8(2). https://doi.org/10.1002/solr.202300815 Publication ID: 122512
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Theristis, M., Anderson, K.S., Stein, J.S., & Stein, J.S. (2023). How climate and data quality impact photovoltaic performance loss rate estimations [Conference Presenation]. https://doi.org/10.2172/2293594 Publication ID: 122708
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Theristis, M., Riedel-Lyngskaer, N., Stein, J.S., Deville, L., & Deville, L. (2023). Blind photovoltaic modeling intercomparison: A multidimensional data analysis and lessons learned. Progress in Photovoltaics: Research and Applications, 31(11), pp. 1144-1157. https://doi.org/10.1002/pip.3729 Publication ID: 107056
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Theristis, M., Deville, L., Anderson, K.S., Stein, J.S., & Stein, J.S. (2023). 2023 PVPMC blind modeling comparison [Conference Presenation]. https://doi.org/10.2172/2293590 Publication ID: 122696
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Theristis, M., Anderson, K.S., Ascencio-Vasquez, J., Stein, J.S., & Stein, J.S. (2023). Impact of analytic decision making on photovoltaic degradation rate estimations using synthetic datasets [Conference Presenation]. https://doi.org/10.2172/2293586 Publication ID: 122688
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Deceglie, M.G., Anderson, K., Fregosi, D., Hobbs, W.B., Mikofski, M.A., Theristis, M., Meyers, B.E., & Meyers, B.E. (2023). Perspective: Performance Loss Rate in Photovoltaic Systems. Solar RRL, 7(15). https://doi.org/10.1002/solr.202300196 Publication ID: 106952
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Theristis, M., King, B.H., Chambers, T., Stein, J.S., & Stein, J.S. (2023). Comparison of Open-Source Photovoltaic Performance Models Against Multi-Year Field Data [Conference Presenation]. https://doi.org/10.2172/2293585 Publication ID: 122684
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Livera, A., Tziolis, G., Theristis, M., Stein, J.S., Georghiou, G.E., & Georghiou, G.E. (2023). Estimating the Performance Loss Rate of Photovoltaic Systems Using Time Series Change Point Analysis. Energies, 16(9). https://doi.org/10.3390/en16093724 Publication ID: 106864
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Theristis, M., Anderson, K.S., Stein, J.S., & Stein, J.S. (2023). The 2023 Blind Photovoltaic Modeling Intercomparison [Conference Presenation]. https://doi.org/10.2172/2431290 Publication ID: 128508
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Theristis, M., Stein, J.S., & Stein, J.S. (2023). The 2021 Blind PVPMC Modeling Intercomparison. https://doi.org/10.2172/2293576 Publication ID: 122660
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Stein, J.S., Theristis, M., King, B.H., Chambers, T., & Chambers, T. (2023). Comparison of Open-Source Photovoltaic Performance Models Against Multi-Year Field Data [Conference Presenation]. https://doi.org/10.2172/2293578 Publication ID: 122664
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Theristis, M., Anderson, K.S., Stein, J.S., Hansen, C., Golnas, T., & Golnas, T. (2023). Announcements of model validation comparisons and RF [Conference Presenation]. https://doi.org/10.2172/2293581 Publication ID: 122668
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Driesse, A., Theristis, M., Stein, J.S., & Stein, J.S. (2023). PV module operating conditions and temperature measurements: an open dataset for PV research. https://doi.org/10.2172/2293574 Publication ID: 122652
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Driesse, A., Theristis, M., Stein, J.S., & Stein, J.S. (2023). Global horizontal spectral irradiance and module spectral response measurements: an open dataset for PV research. https://doi.org/10.2172/2293575 Publication ID: 122656
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Theristis, M., Stein, J.S., Deline, C., Jordan, D., Robinson, C., Sekulic, W., Anderberg, A., Colvin, D.J., Walters, J., Seigneur, H., King, B.H., & King, B.H. (2023). Onymous early-life performance degradation analysis of recent photovoltaic module technologies. Progress in Photovoltaics: Research and Applications, 31(2), pp. 149-160. https://doi.org/10.1002/pip.3615 Publication ID: 106560
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Hansen, C., Jones, A.R., Transue, T., Theristis, M., & Theristis, M. (2023). Benchmark Tests for IV Fitting Algorithms [Conference Paper]. Conference Record of the IEEE Photovoltaic Specialists Conference. https://doi.org/10.1109/PVSC48320.2023.10359911 Publication ID: 122680
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Hansen, C., Jones, A.R., Transue, T., Theristis, M., & Theristis, M. (2023). Benchmark Tests for IV Fitting Algorithms [Conference Poster]. Conference Record of the IEEE Photovoltaic Specialists Conference. https://doi.org/10.2172/2293583 Publication ID: 122676
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Micheli, L., Theristis, M., Talavera, D.L., Nofuentes, G., Stein, J.S., Fernandez, E.F., & Fernandez, E.F. (2022). The economic value of photovoltaic performance loss mitigation in electricity spot markets. Renewable Energy, 199, pp. 486-497. https://doi.org/10.1016/j.renene.2022.08.149 Publication ID: 80146
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Theristis, M., Stein, J.S., Riedel-Lyngskaer, N., Deville, L., Barrie, D., Campanelli, M., Daxini, R., Driesse, A., Hobbs, W.B., Hodges, H., Ledesma, J.R., Lokhat, I., McCormick, B., Mengbin, B., Micheli, L., Miller, B., Motta, R., Noirault, E., Ovaitt, S., … Zhao, C. (2022). International Photovoltaic Modeling Intercomparison [Slides] [Conference Presenation]. https://doi.org/10.2172/2004810 Publication ID: 118068
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Stein, J.S., Schelhas, L., King, B.H., Nie, W., Romero, R., Crimmins, J., Libby, C., Montgomery, A., Robinson, C., Torrence, C., Theristis, M., Berry, J., Silverman, T.J., Owen-Bellini, M., Repins, I., Sulas-Kern, D., Deceglie, M.G., White, R., Perry, K., … Li, W. (2022). Perovskite PV Accelerator for Commercializing Technology (PACT) [Conference Presenation]. https://doi.org/10.2172/2004782 Publication ID: 117956
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Kumari, M., Theristis, M., Stein, J.S., & Stein, J.S. (2022). Impact of Various Photovoltaic Module Characteristics across Geographic Regions [Conference Presenation]. https://doi.org/10.2172/2004754 Publication ID: 117848
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Theristis, M. (2022). Early-life degradation analysis of PV module technologies exposed in different climates in the US [Conference Presenation]. https://doi.org/10.2172/2004728 Publication ID: 117744
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Micheli, L., Theristis, M., Talavera, D.L., Nofuentes, G., Stein, J.S., Fernandez, E.F., & Fernandez, E.F. (2022). The Economic Value of Photovoltaic Performance Loss Mitigation in Electricity Spot Markets [Conference Poster]. https://doi.org/10.2172/2004685 Publication ID: 117572
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Hansen, C., Johnson, J., Darbali-Zamora, R., Gurule, N., Gonzalez, S., Theristis, M., & Theristis, M. (2022). Modeling Efficiency of Inverters with Multiple Inputs: Test Procedure for Measuring Efficiency [Conference Poster]. https://doi.org/10.2172/2004793 Publication ID: 118000
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Hansen, C., Johnson, J., Darbali-Zamora, R., Gurule, N., Gonzalez, S., Theristis, M., & Theristis, M. (2022). MODELING INVERTERS WITH MULTIPLE INPUTS: TEST PROCEDURE FOR MEASURING EFFICIENCY [Conference Paper]. https://www.osti.gov/biblio/2004840 Publication ID: 118184
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Livera, A., Theristis, M., Micheli, L., Stein, J.S., Georghiou, G.E., & Georghiou, G.E. (2022). Failure diagnosis and trend-based performance losses routines for the detection and classification of incidents in large-scale photovoltaic systems. Progress in Photovoltaics: Research and Applications, 30(8), pp. 921-937. https://doi.org/10.1002/pip.3578 Publication ID: 80745
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Driesse, A., Stein, J.S., Theristis, M., & Theristis, M. (2022). Improving Common PV Module Temperature Models by Incorporating Radiative Losses to the Sky. https://doi.org/10.2172/1884890 Publication ID: 80117
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Kinsey, G.S., Riedel-Lyngskaer, N.C., Miguel, A.A., Boyd, M., Braga, M., Shou, C., Cordero, R.R., Duck, B.C., Fell, C.J., Feron, S., Georghiou, G.E., Habryl, N., John, J.J., Ketjoy, N., Lopez, G., Louwen, A., Maweza, E.L., Mittal, A., Molto, C., … Yamasoe, M.A. (2022). Impact of measured spectrum variation on solar photovoltaic efficiencies worldwide. Renewable Energy, 196, pp. 995-1016. https://doi.org/10.1016/j.renene.2022.07.011 Publication ID: 80020
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Driesse, A., Stein, J.S., Theristis, M., & Theristis, M. (2022). PV Module Operating Temperature Model Equivalence and Parameter Translation [Conference Paper]. https://doi.org/10.1109/PVSC48317.2022.9938895 Publication ID: 113864
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Lunis, P., Silva, B., Theristis, M., Seigneur, H., & Seigneur, H. (2022). Photovoltaic Reliability Performance Model (PVRPM) in Python and the Value of Monitoring [Conference Paper]. https://www.osti.gov/biblio/2003767 Publication ID: 114360
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Deville, L., Theristis, M., King, B.H., Stein, J.S., & Stein, J.S. (2022). Comparative Analysis of 12 Photovoltaic Performance Models [Conference Poster]. https://doi.org/10.2172/2003342 Publication ID: 112740
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Theristis, M., Pierce, B.G., Stein, J.S., Kumari, M., & Kumari, M. (2022). Geographic Analysis of PV Module Characteristics [Conference Poster]. https://doi.org/10.2172/2003413 Publication ID: 112980
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Kumari, M., Theristis, M., Stein, J.S., & Stein, J.S. (2022). Photovoltaic System Capacity Testing [Conference Presenation]. https://doi.org/10.2172/2003418 Publication ID: 113000
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Lindig, S., Theristis, M., Moser, D., & Moser, D. (2022). Best practices for photovoltaic performance loss rate calculations. Progress in Energy, 4(2). https://doi.org/10.1088/2516-1083/ac655f Publication ID: 80621
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Deville, L., Theristis, M., King, B.H., Stein, J.S., & Stein, J.S. (2022). Comparative Analysis of 12 Photovoltaic Performance Models [Conference Poster]. https://doi.org/10.2172/2002486 Publication ID: 110864
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Silva, B., Lunis, P., Theristis, M., Seigneur, H., & Seigneur, H. (2022). PyPVRPM: Photovoltaic Reliability and Performance Model in Python. Journal of Open Source Software, 7(71). https://doi.org/10.21105/joss.04093 Publication ID: 80578
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Livera, A., Paphitis, G., Theristis, M., Lopez-Lorente, J., Makrides, G., Georghiou, G.E., & Georghiou, G.E. (2022). Photovoltaic System Health-State Architecture for Data-Driven Failure Detection. Solar, 2(1), pp. 81-98. https://doi.org/10.3390/solar2010006 Publication ID: 80579
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Theristis, M. (2022). Early-life module degradation results from the PV system long-term exposure (SLTE) project [Conference Presenation]. https://doi.org/10.2172/2002132 Publication ID: 109504
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Livera, A., Theristis, M., Micheli, L., Fernandez, E.F., Stein, J.S., Georghiou, G.E., & Georghiou, G.E. (2022). Operation and Maintenance Decision Support System for Photovoltaic Systems. IEEE Access, 10, pp. 42481-42496. https://doi.org/10.1109/access.2022.3168140 Publication ID: 80627
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Romero-Fiances, I., Livera, A., Theristis, M., Makrides, G., Stein, J.S., Nofuentes, G., de la Casa, J., Georghiou, G.E., & Georghiou, G.E. (2022). Impact of duration and missing data on the long-term photovoltaic degradation rate estimation. Renewable Energy, 181, pp. 738-748. https://doi.org/10.1016/j.renene.2021.09.078 Publication ID: 75961
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Livera, A., Tziolis, G., Theristis, M., Stein, J.S., Georghiou, G.E., & Georghiou, G.E. (2022). Performance Loss Rate Estimation of Fielded Photovoltaic Systems Based on Statistical Change-Point Techniques [Conference Paper]. SyNERGY MED 2022 – 2nd International Conference on Energy Transition in the Mediterranean Area, Proceedings. https://doi.org/10.1109/SyNERGYMED55767.2022.9941390 Publication ID: 115212
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Kumari, M., Theristis, M., Stein, J.S., & Stein, J.S. (2022). Geographic Analysis for Determining the Value of Different Photovoltaic Performance Factors [Conference Proceeding]. Conference Record of the IEEE Photovoltaic Specialists Conference. https://doi.org/10.1109/PVSC48317.2022.9938745 Publication ID: 113740
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Jones, C.B., Theristis, M., Darbali-Zamora, R., Ropp, M.E., Reno, M.J., & Reno, M.J. (2022). Switch Location Identification for Integrating a Distant Photovoltaic Array Into a Microgrid. IEEE Access, 10, pp. 57902-57913. https://doi.org/10.1109/access.2022.3177143 Publication ID: 80109
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Theristis, M., Livera, A., Micheli, L., Ascencio-Vasquez, J., Makrides, G., Georghiou, G.E., Stein, J.S., & Stein, J.S. (2021). Comparative Analysis of Change-Point Techniques for Nonlinear Photovoltaic Performance Degradation Rate Estimations. IEEE Journal of Photovoltaics, 11(6), pp. 1511-1518. https://doi.org/10.1109/jphotov.2021.3112037 Publication ID: 75576
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Theocharides, S., Makrides, G., Theristis, M., Georghiou, G.E., & Georghiou, G.E. (2021). Novel intraday photovoltaic production forecasting algorithm using deep learning ensemble models [Conference Paper]. https://www.osti.gov/biblio/1886762 Publication ID: 75577
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Livera, A., Theristis, M., Stein, J.S., Georghiou, G.E., & Georghiou, G.E. (2021). Failure diagnosis and trend-based performance losses routines for the detection and classification of incidents in large-scale photovoltaic systems [Conference Paper]. https://doi.org/10.1002/pip.3578 Publication ID: 75474
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Livera, A., Theristis, M., Charalambous, A., Stein, J.S., Georghiou, G.E., & Georghiou, G.E. (2021). Decision support system for corrective maintenance in large-scale photovoltaic systems [Conference Paper]. Conference Record of the IEEE Photovoltaic Specialists Conference. https://doi.org/10.1109/PVSC43889.2021.9518796 Publication ID: 78803
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Lindig, S., Moser, D., Curran, A.J., Rath, K., Khalilnejad, A., French, R.H., Herz, M., Muller, B., Makrides, G., Georghiou, G., Livera, A., Richter, M., Ascencio-Vasquez, J., van Iseghem, M., Meftah, M., Jordan, D., van Sark, W., Stein, J.S., Theristis, M., … Luo, W. (2021). International collaboration framework for the calculation of performance loss rates: Data quality, benchmarks, and trends (towards a uniform methodology). Progress in Photovoltaics: Research and Applications, 29(6), pp. 573-602. https://doi.org/10.1002/pip.3397 Publication ID: 103360
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Driesse, A., Theristis, M., Stein, J.S., & Stein, J.S. (2021). A New Photovoltaic Module Efficiency Model for Energy Prediction and Rating. IEEE Journal of Photovoltaics, 11(2), pp. 527-534. https://doi.org/10.1109/jphotov.2020.3045677 Publication ID: 72335
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Micheli, L., Theristis, M., Livera, A., Stein, J.S., Georghiou, G.E., Muller, M., Almonacid, F., Fernandez, E.F., & Fernandez, E.F. (2021). Improved PV Soiling Extraction through the Detection of Cleanings and Change Points. IEEE Journal of Photovoltaics, 11(2), pp. 519-526. https://doi.org/10.1109/jphotov.2020.3043104 Publication ID: 103156
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Theocharides, S., Theristis, M., Makrides, G., Kynigos, M., Spanias, C., Georghiou, G.E., & Georghiou, G.E. (2021). Comparative analysis of machine learning models for day-ahead photovoltaic power production forecasting†. Energies, 14(4). https://doi.org/10.3390/en14041081 Publication ID: 77265
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Livera, A., Theristis, M., Koumpli, E., Theocharides, S., Makrides, G., Sutterlueti, J., Stein, J.S., Georghiou, G.E., & Georghiou, G.E. (2021). Data processing and quality verification for improved photovoltaic performance and reliability analytics. Progress in Photovoltaics: Research and Applications, 29(2), pp. 143-158. https://doi.org/10.1002/pip.3349 Publication ID: 71217
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Theristis, M., Ascencio-Vasquez, J., Stein, J.S., & Stein, J.S. (2021). Geographic and technology factors in photovoltaicperformance degradation rate estimations [Conference Presenation]. https://doi.org/10.2172/1844313 Publication ID: 75512
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Livera, A., Theristis, M., Koumpli, E., Makrides, G., Stein, J.S., Georghiou, G.E., & Georghiou, G.E. (2020). GUIDELINES FOR ENSURING DATA QUALITY FOR PHOTOVOLTAIC SYSTEM PERFORMANCE ASSESSMENT AND MONITORING [Conference Poster]. https://www.osti.gov/biblio/1820258 Publication ID: 74773
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Livera, A., Theristis, M., Koumpli, E., Makrides, G., Stein, J.S., Georghiou, G.E., & Georghiou, G.E. (2020). GUIDELINES FOR ENSURING DATA QUALITY FOR PHOTOVOLTAIC SYSTEM PERFORMANCE ASSESSMENT AND MONITORING [Conference Poster]. https://www.osti.gov/biblio/1820257 Publication ID: 74772
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Theocharides, S., Makrides, G., Theristis, M., Kynigos, M., Georghiou, G.E., & Georghiou, G.E. (2020). Hybrid Modelling of PV Power Generation for Enhanced Forecasting [Conference Poster]. https://www.osti.gov/biblio/1820293 Publication ID: 74816
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Theocharides, S., Makrides, G., Theristis, M., Kynigos, M., Georghiou, G.E., & Georghiou, G.E. (2020). Hybrid Modelling of PV Power Generation for Enhanced Forecasting [Conference Poster]. https://www.osti.gov/biblio/1820277 Publication ID: 74797
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Theristis, M., Ascencio-Vasquez, J., King, B.H., Topic, M., Stein, J.S., & Stein, J.S. (2020). CHALLENGES ASSOCIATED WITH INCONSISTENT PHOTOVOLTAIC DEGRADATION RATE ESTIMATIONS [Conference Poster]. https://www.osti.gov/biblio/1820291 Publication ID: 74814
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Theristis, M., Ascencio-Vasquez, J., King, B.H., Topic, M., Stein, J.S., & Stein, J.S. (2020). CHALLENGES ASSOCIATED WITH INCONSISTENT PHOTOVOLTAIC DEGRADATION RATE ESTIMATIONS [Conference Poster]. https://www.osti.gov/biblio/1820292 Publication ID: 74815
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Theristis, M., Livera, A., Jones, C.B., Makrides, G., Georghiou, G.E., Stein, J.S., & Stein, J.S. (2020). Nonlinear Photovoltaic Degradation Rates: Modeling and Comparison against Conventional Methods. IEEE Journal of Photovoltaics, 10(4), pp. 1112-1118. https://doi.org/10.1109/JPHOTOV.2020.2992432 Publication ID: 73251
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Theocharides, S., Makrides, G., Livera, A., Theristis, M., Kaimakis, P., Georghiou, G.E., & Georghiou, G.E. (2020). Day-ahead photovoltaic power production forecasting methodology based on machine learning and statistical post-processing. Applied Energy, 268(C). https://doi.org/10.1016/j.apenergy.2020.115023 Publication ID: 73307
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Jones, C.B., Theristis, M., Stein, J.S., Hansen, C., & Hansen, C. (2020). Feature Selection of Photovoltaic System Data to Avoid Misclassification of Fault Conditions [Conference Poster]. Conference Record of the IEEE Photovoltaic Specialists Conference. https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85091314100&origin=inward Publication ID: 73720
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Theristis, M., Livera, A., Micheli, L., Jones, C.B., Makrides, G., Georghiou, G.E., Stein, J.S., & Stein, J.S. (2020). Modeling nonlinear photovoltaic degradation rates [Conference Poster]. Conference Record of the IEEE Photovoltaic Specialists Conference. https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85097069779&origin=inward Publication ID: 73706
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Theristis, M. (2020). Modeling nonlinear photovoltaic degradation rates [Conference Poster]. https://www.osti.gov/biblio/1807378 Publication ID: 73725
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Jones, C.B., Theristis, M., Stein, J.S., Hansen, C., & Hansen, C. (2020). Feature Selection of Photovoltaic System Data to Avoid Misclassification of Fault Conditions [Conference Poster]. https://www.osti.gov/biblio/1807374 Publication ID: 73721
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Micheli, L., Theristis, M., Talavera, D.L., Almonacid, F., Stein, J.S., Fernandez, E.F., & Fernandez, E.F. (2020). Photovoltaic cleaning frequency optimization under different degradation rate patterns. Renewable Energy, 166, pp. 136-146. https://doi.org/10.1016/j.renene.2020.11.044 Publication ID: 71779
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Livera, A., Theristis, M., Koumpli, E., Makrides, G., Stein, J.S., Georghiou, G., & Georghiou, G. (2020). Guidelines for ensuring data quality for photovoltaic system performance assessment and monitoring [Conference Poster]. https://www.osti.gov/biblio/1767089 Publication ID: 72689