diff --git a/joss.07928/10.21105.joss.07928.crossref.xml b/joss.07928/10.21105.joss.07928.crossref.xml new file mode 100644 index 0000000000..4be4198ccb --- /dev/null +++ b/joss.07928/10.21105.joss.07928.crossref.xml @@ -0,0 +1,250 @@ + + + + 20260305155400-928ef11dce536094bcf4af632055eec97744386b + 20260305155400 + + JOSS Admin + admin@theoj.org + + The Open Journal + + + + + Journal of Open Source Software + JOSS + 2475-9066 + + 10.21105/joss + https://joss.theoj.org + + + + + 03 + 2026 + + + 11 + + 119 + + + + SunPeek: Open-Source Tool for Performance Analytics of Solar Thermal Plants + + + + Philip + Ohnewein + + AEE – Institute for Sustainable Technologies, Austria + + https://orcid.org/0000-0002-1682-3883 + + + Marnoch + Hamilton-Jones + + AEE – Institute for Sustainable Technologies, Austria + + https://orcid.org/0000-0002-2725-6773 + + + Lukas + Emberger + + SOLID Solar Energy Systems GmbH, Austria + + https://orcid.org/0000-0003-2871-1114 + + + Daniel + Tschopp + + AEE – Institute for Sustainable Technologies, Austria + University of Innsbruck, Unit for Energy Efficient Buildings, Austria + + https://orcid.org/0000-0002-6285-981X + + + Peter + Zauner + + AEE – Institute for Sustainable Technologies, Austria + + https://orcid.org/0000-0001-9553-6905 + + + Jonathan Cazco + Gonzalez + + AEE – Institute for Sustainable Technologies, Austria + + https://orcid.org/0000-0001-8033-9351 + + + Maria + Moser + + SOLID Solar Energy Systems GmbH, Austria + + https://orcid.org/0000-0002-0139-9266 + + + Hannes + Poier + + SOLID Solar Energy Systems GmbH, Austria + + https://orcid.org/0000-0003-0959-9964 + + + Christopher + Albert + + Graz University of Technology, Institute for Theoretical Physics – Computational Physics, Austria + + https://orcid.org/0000-0003-4773-416X + + + Léo + Bonal + + V-Research GmbH, Austria + + https://orcid.org/0009-0004-8096-5423 + + + + 03 + 05 + 2026 + + + 7928 + + + 10.21105/joss.07928 + + + http://creativecommons.org/licenses/by/4.0/ + http://creativecommons.org/licenses/by/4.0/ + http://creativecommons.org/licenses/by/4.0/ + + + + Software archive + 10.5281/zenodo.18861353 + + + GitHub review issue + https://github.com/openjournals/joss-reviews/issues/7928 + + + + 10.21105/joss.07928 + https://joss.theoj.org/papers/10.21105/joss.07928 + + + https://joss.theoj.org/papers/10.21105/joss.07928.pdf + + + + + + One year of high-precision operational data including measurement uncertainties from a large-scale solar thermal collector array with flat plate collectors, located in Graz, Austria + Tschopp + Data in Brief + 48 + 10.1016/j.dib.2023.109224 + 2023 + Tschopp, D., Ohnewein, P., Stelzer, R., Feierl, L., Hamilton-Jones, M., Moser, M., & Holter, C. (2023). One year of high-precision operational data including measurement uncertainties from a large-scale solar thermal collector array with flat plate collectors, located in Graz, Austria. Data in Brief, 48, 109224. https://doi.org/10.1016/j.dib.2023.109224 + + + ISO 24194 Solar energy — Collector fields — Check of performance + 2022 + ISO 24194 Solar energy — Collector fields — Check of performance. (2022). [Standard]. International Organization for Standardization. + + + ISO 9806 Solar energy — Solar thermal collectors — Test methods + 2025 + ISO 9806 Solar energy — Solar thermal collectors — Test methods. (2025). [Standard]. International Organization for Standardization. + + + Dynamic Collector Array Test (D-CAT). Final report FFG project 848766 - MeQuSo. Development of methods for quality assessment of large-scale solar thermal plants under real operating conditions. + Ohnewein + 10.5281/zenodo.7615252 + 2020 + Ohnewein, P., Tschopp, D., Hausner, R., & Doll, W. (2020). Dynamic Collector Array Test (D-CAT). Final report FFG project 848766 - MeQuSo. Development of methods for quality assessment of large-scale solar thermal plants under real operating conditions. AEE INTEC. https://doi.org/10.5281/zenodo.7615252 + + + Large-scale solar thermal systems in leading countries: A review and comparative study of Denmark, China, Germany and Austria + Tschopp + Applied Energy + 270 + 10.1016/j.apenergy.2020.114997 + 2020 + Tschopp, D., Tian, Z., Berberich, M., Fan, J., Perers, B., & Furbo, S. (2020). Large-scale solar thermal systems in leading countries: A review and comparative study of Denmark, China, Germany and Austria. Applied Energy, 270, 114997. https://doi.org/10.1016/j.apenergy.2020.114997 + + + Solar engineering of thermal processes, photovoltaics and wind, 5th edition + Duffie + 10.1002/9781119540328 + 978-1-119-54028-1 + 2020 + Duffie, J. A., Beckman, W. A., & Blair, N. (2020). Solar engineering of thermal processes, photovoltaics and wind, 5th edition. John Wiley & Sons. https://doi.org/10.1002/9781119540328 + + + Guide to ISO 24194:2022 Power Check - procedure for checking the power performance of solar thermal collector fields + 10.5281/zenodo.16954914 + 2025 + Tschopp, D., Ohnewein, P., Mehnert, S., & Emberger, L. (Eds.). (2025). Guide to ISO 24194:2022 Power Check - procedure for checking the power performance of solar thermal collector fields [Report RB2 from IEA SHC Task 68]. https://doi.org/10.5281/zenodo.16954914 + + + SunPeek open-source software for ISO 24194 performance assessment and monitoring of large-scale solar thermal plants + Tschopp + International Sustainable Energy Conference - Proceedings + 1 + 10.52825/isec.v1i.1248 + 2976-2030 + 2024 + Tschopp, D., Ohnewein, P., Hamilton-Jones, M., Zauner, P., Feierl, L., Moser, M., Zellinger, M., Kloibhofer, C., Koren, M., Mehnert, S., Duret, A., Jobard, X., Pauletta, S., Giovannetti, F., & Schiebler, B. (2024). SunPeek open-source software for ISO 24194 performance assessment and monitoring of large-scale solar thermal plants. International Sustainable Energy Conference - Proceedings, 1. https://doi.org/10.52825/isec.v1i.1248 + + + Digital tools for solar thermal plant monitoring. A handbook for plant operators and associated stakeholders. Version 1.0 (june 2024) + Tschopp + 10.5281/zenodo.12523699 + 2024 + Tschopp, D., Ohnewein, P., Feierl, L., & Hamilton-Jones, M. (2024). Digital tools for solar thermal plant monitoring. A handbook for plant operators and associated stakeholders. Version 1.0 (june 2024). DIH Süd. https://doi.org/10.5281/zenodo.12523699 + + + Pvlib python: 2023 project update + Anderson + Journal of Open Source Software + 92 + 8 + 10.21105/joss.05994 + 2023 + Anderson, K. S., Hansen, C. W., Holmgren, W. F., Jensen, A. R., Mikofski, M. A., & Driesse, A. (2023). Pvlib python: 2023 project update. Journal of Open Source Software, 8(92), 5994. https://doi.org/10.21105/joss.05994 + + + + + + diff --git a/joss.07928/10.21105.joss.07928.pdf b/joss.07928/10.21105.joss.07928.pdf new file mode 100644 index 0000000000..47d7b98b28 Binary files /dev/null and b/joss.07928/10.21105.joss.07928.pdf differ diff --git a/joss.07928/paper.jats/10.21105.joss.07928.jats b/joss.07928/paper.jats/10.21105.joss.07928.jats new file mode 100644 index 0000000000..c97609f5d5 --- /dev/null +++ b/joss.07928/paper.jats/10.21105.joss.07928.jats @@ -0,0 +1,640 @@ + + +
+ + + + +Journal of Open Source Software +JOSS + +2475-9066 + +Open Journals + + + +7928 +10.21105/joss.07928 + +SunPeek: Open-Source Tool for Performance Analytics of +Solar Thermal Plants + + + +https://orcid.org/0000-0002-1682-3883 + +Ohnewein +Philip + + +* + + +https://orcid.org/0000-0002-2725-6773 + +Hamilton-Jones +Marnoch + + + + +https://orcid.org/0000-0003-2871-1114 + +Emberger +Lukas + + + + +https://orcid.org/0000-0002-6285-981X + +Tschopp +Daniel + + + + + +https://orcid.org/0000-0001-9553-6905 + +Zauner +Peter + + + + +https://orcid.org/0000-0001-8033-9351 + +Gonzalez +Jonathan Cazco + + + + +https://orcid.org/0000-0002-0139-9266 + +Moser +Maria + + + + +https://orcid.org/0000-0003-0959-9964 + +Poier +Hannes + + + + +https://orcid.org/0000-0003-4773-416X + +Albert +Christopher + + + + +https://orcid.org/0009-0004-8096-5423 + +Bonal +Léo + + + + + +AEE – Institute for Sustainable Technologies, +Austria + + + + +SOLID Solar Energy Systems GmbH, Austria + + + + +University of Innsbruck, Unit for Energy Efficient +Buildings, Austria + + + + +Graz University of Technology, Institute for Theoretical +Physics – Computational Physics, Austria + + + + +V-Research GmbH, Austria + + + + +* E-mail: + +11 +119 +7928 + +Authors of papers retain copyright and release the +work under a Creative Commons Attribution 4.0 International License (CC +BY 4.0) +2026 +The article authors + +Authors of papers retain copyright and release the work under +a Creative Commons Attribution 4.0 International License (CC BY +4.0) + + + +python +solar energy +solar thermal +renewable heat +performance assessment + + + + + + + Summary +

SunPeek is an open-source software designed to automate the + performance evaluation of solar thermal plants, focusing on + large-scale installations. Addressing both researchers and plant + operators, SunPeek provides a practical framework for operational + performance analysis. SunPeek computes expected solar thermal output + using models based on ISO 24194 and automates data ingestion and + cleaning, performance modeling and data analysis, result + visualization, and report generation. SunPeek emerged from + collaboration between research institutes and industry partners + (Tschopp, + Ohnewein, Hamilton-Jones, et al., 2024; + Tschopp + et al., 2025). To our knowledge, it provides the first + open-source implementation of the ISO 24194 Power Check + (ISO + 24194 Solar energy — Collector + fields — Check of performance, 2022), + a standardized methodology for evaluating the power performance of + solar thermal collector fields. SunPeek also integrates an open + dataset, comprising a full year of measurement data from a real-world, + large-scale solar plant, as described in a journal article + (Tschopp + et al., 2023).

+
+ + Availability +

Designed as a containerized web application, SunPeek includes a web + interface and a Python backend with a REST API, and a few auxiliary + repositories. The Python backend comprises approximately 27,500 lines + of code with 96.3% test coverage, while the JavaScript-based web + interface adds around 7,950 lines (both including tests, excluding + blank lines and comments). All + SunPeek + repositories are accessible via GitLab. Docker containers + are available on + DockerHub, + and there is a + public + demo server. The backend is also available as a standalone + Python package, listed on + PyPI. + SunPeek is a + NumFOCUS + affiliated project and is managed by a Steering Committee, + as detailed in the + governance + repository. + Community + guidelines outline how to contribute to SunPeek, and + detailed + documentation + is available.

+

SunPeek repositories are released under open licenses: GNU LGPL for + the + backend, + BSD-3-Clause for the + user + interface, CC-BY-SA 4.0 for the + open + dataset. A curated collection of SunPeek-related + publications, including the aforementioned dataset, technical reports, + and peer-reviewed articles, is available on the + SunPeek + Zenodo community.

+
+ + Statement of Need +

Solar thermal collectors convert solar radiation directly into + thermal energy by heating a working fluid circulating through the + collectors. Large-scale solar thermal plants provide heat for + applications such as industries or district heating and represent a + critical technology for the renewable energy transition + (Tschopp + et al., 2020). Assessing the performance of these systems is + inherently complex and has been extensively researched for decades + (Duffie + et al., 2020). Key challenges include the stochastic nature of + operating conditions (e.g., solar irradiance fluctuations, return + temperature oscillations), heat capacity and delay effects caused by + fluid transport, and lack of standardization in measurement setups of + solar thermal plants.

+

Before SunPeek, no open-source tools existed for modeling and + assessing solar thermal plant performance + (Tschopp, + Ohnewein, Feierl, et al., 2024). SunPeek addresses this and + distinguishes itself from commercial tools by combining scientifically + validated, tailored algorithms for solar thermal systems (like the ISO + 24194 Power Check), adaptive performance modeling based on measurement + data from real plant operation (unlike simulation tools), and + automated data processing and analytics. Its modeling framework adapts + to various hydraulic configurations and measurement setups. Serving as + the reference software implementation of the ISO 24194 Power Check + (Tschopp + et al., 2025), SunPeek streamlines methodological advancements + in the field. As illustrated in + [fig:C4_level1], + SunPeek addresses diverse users - technical experts (typically + accessing SunPeek via the Python backend or API) and general users + (via the JavaScript-based web app) - as well as external software and + monitoring systems that integrate via the REST API.

+ +

C4 System Context diagram of the SunPeek software + system.

+ +
+ +

Screenshot of SunPeek’s web user interface: Interactive + display of Power Check + results.

+ +
+
+ + Algorithms and Automation +

SunPeek offers a range of interactive features, including plant + configuration, Power Check analysis (see screenshot in + [fig:web_ui_screenshot]), + automated generation of PDF reports, and CSV export of calculation + results. A fully + documented + REST API enables programmatic access to all configuration + and analysis functionalities, enabling automation of all configuration + and analysis tasks. + [fig:automation_framework] + illustrates the automation framework for executing the Power Check, + including the key steps in modeling, data handling, and visualization. + [fig:C4_level2] + presents an overview of SunPeek’s software architecture, highlighting + the technologies employed and the interactions between core + components.

+

At the core of SunPeek’s performance analysis is the “Power Check” + method, a standardized procedure for evaluating the power performance + of solar thermal collector fields, based on + (ISO + 24194 Solar energy — Collector + fields — Check of performance, 2022). + This method employs a grey-box model that combines measurement data + with physical domain knowledge (e.g., collector efficiency parameters, + collector field geometry) to model the estimated power output during + stable operating intervals. The primary performance metric used in the + Power Check is the ratio of measured-to-estimated power output, + enabling a target-to-actual performance analysis on an absolute scale. + Tracking this metric over time can help identify faults and determine + whether the plant’s measured performance aligns with expectations.

+

The Power Check method factors in measured operating conditions + that influence system performance, such as solar radiation, + temperatures, and shading. This ensures that the Power Check + performance metrics generalize well: they are applicable across + various geographical regions, collector technologies, and weather + conditions. The insights derived from the Power Check can be valuable + for plant operation and maintenance: a drop in the target-to-actual + metric below expected values can indicate issues requiring action, + such as collector cleaning, control adjustments, or general + maintenance.

+

In addition to the standard Power Check, SunPeek features an + “Extended Power Check”, with improved data filtering + (Tschopp, + Ohnewein, Hamilton-Jones, et al., 2024). This enhancement uses + a moving-window method combined with a minimum-noise selection + criterion to improve result accuracy. Beyond Power Check analysis, the + SunPeek platform is designed to accommodate additional performance + analysis methods, including D-CAT (Dynamic Collector Array Test), + discussed in Future Work.

+ +

SunPeek automation framework for executing the Power + Check and other analysis methods. Customizable modules (white boxes) + include data handling, modeling, and + visualization.

+ +
+

[fig:automation_framework] + illustrates SunPeek’s framework for automating performance evaluations + of solar thermal plants, after an initial plant configuration step. + Automation concepts include:

+ + +

Collector parameterization: SunPeek supports + collector efficiency parameters derived from the widely used QDT + (quasi-dynamic test) of + (ISO + 9806 Solar energy — Solar + thermal collectors — Test methods, + 2025). Parameters from various testing procedures (e.g., + earlier versions of ISO 9806, steady-state tests, and different + incidence angle modifier models) are also accepted and + automatically converted as needed. The tool includes + pre-configured collectors and allows users to define custom + collectors. Development of an automated interface to the extensive + Solar + Keymark collector database is currently ongoing.

+
+ +

Robust data quality checks: SunPeek validates + plant configurations and time series data for consistency and + compatibility with the chosen analysis methods. These built-in + checks eliminate the need for data preprocessing using external + tools.

+
+ +

Heat transfer fluids: SunPeek uses + CoolProp + to compute fluid properties if required for the performance + calculations (e.g., temperature- and concentration-dependent + density and heat capacity). The software comes with pre-defined + heat transfer fluids commonly used in solar thermal plants.

+
+ +

Collector field mounting types: SunPeek + supports fixed-mounted and single-axis tracking collector fields, + covering two main mounting configurations in large-scale solar + thermal plants.

+
+ +

Virtual sensors: Virtual sensors derive + unmeasured quantities (e.g., solar position, collector field + shading, or fluid properties), enabling or enhancing modeling. + Virtual sensors are computed from measured sensor data and + parameters, accommodating the diverse and non-standardized + measurement setups found in solar thermal plants. SunPeek uses + pvlib + (Anderson + et al., 2023) for solar position and angle of incidence + calculations, incidence angle modifiers, shading fraction + estimation, and single-axis tracking geometry and shading.

+
+ +

Unit awareness: All physical parameters and + measurement data in SunPeek are encoded as unit-aware quantities, + leveraging the + pint + and + pandas + libraries. This ensures consistent and reliable handling of units + across all calculations and analyses.

+
+
+ +

C4 container diagram of the SunPeek software + system.

+ +
+
+ + Usage and Community +

The + IEA + SHC Task 68 Guide to the Power Check + (Tschopp + et al., 2025) documents use cases and successful deployments of + SunPeek in large-scale solar plants. The development team maintains + active collaboration with the solar thermal community, including both + industry and academia, and with the technical committee ISO/TC 180/SC4 + responsible for developing the ISO 24194 standard. As the reference + implementation of ISO 24194, SunPeek has helped identify important + shortcomings and ambiguities in the standard, encouraging + collaboration among researchers, industry partners, and technical + committees. The SunPeek implementation, proposed method enhancements + and directions for future work, are comprehensively described in + (Tschopp + et al., 2025). A curated collection of SunPeek-related + publications is hosted on + Zenodo.

+
+ + Future Work +

We are integrating D-CAT (Dynamic Collector Array Test), a dynamic + performance analysis method that extends the ISO 9806 collector model + by incorporating transport effects in collector fields. It could be + used for fault diagnostics and solar energy yield assessment, relevant + for the financial performance of a solar plant. The D-CAT method has + been developed through several research projects; see + (Ohnewein + et al., 2020) for additional background. The implementation is + being developed in a + SunPeek + fork and is planned to be merged with the main project + later.

+

Other planned developments include enhancements to the Power Check + method, as outlined in + (Tschopp + et al., 2025), and implementation of the Annual Yield Check, + defined in a new revision of ISO 24194 targeted for 2026. Longer-term + goals are summarized in the + project + roadmap and include several key features: integrating an + automatic interface with the + Solar + Keymark collectors database, adding data integration with + common SCADA systems, and developing a cloud-based SunPeek solution to + enable software-as-a-service (SaaS) offerings.

+
+ + Acknowledgements +

SunPeek development was partially funded by the Austrian Research + Promotion Agency (grant no. FO999887648, FO999890460, FO999908366), + Austrian Federal Ministry of Labour and Economy (grant no. + SP-2024-02), and the European Commission (grant no. 101136140 and + 101235027). The authors acknowledge and thank all contributors to the + project, with special recognition to Michael Zellinger, Christian + Kloibhofer, Alexander Thür, Wolfgang Streicher and Martin Koren.

+
+ + + + + + + + TschoppDaniel + OhneweinPhilip + StelzerRoman + FeierlLukas + Hamilton-JonesMarnoch + MoserMaria + HolterChristian + + One year of high-precision operational data including measurement uncertainties from a large-scale solar thermal collector array with flat plate collectors, located in Graz, Austria + Data in Brief + 2023 + 48 + 10.1016/j.dib.2023.109224 + 109224 + + + + + + ISO 24194 Solar energy — Collector fields — Check of performance + International Organization for Standardization + Geneva + 2022 + + + + + ISO 9806 Solar energy — Solar thermal collectors — Test methods + International Organization for Standardization + Geneva + 2025 + + + + + + OhneweinPhilip + TschoppDaniel + HausnerRobert + DollWerner + + Dynamic Collector Array Test (D-CAT). Final report FFG project 848766 - MeQuSo. Development of methods for quality assessment of large-scale solar thermal plants under real operating conditions. + AEE INTEC + Gleisdorf + 2020 + 10.5281/zenodo.7615252 + + + + + + TschoppDaniel + TianZhiyong + BerberichMagdalena + FanJianhua + PerersBengt + FurboSimon + + Large-scale solar thermal systems in leading countries: A review and comparative study of Denmark, China, Germany and Austria + Applied Energy + 202007 + 20200604 + 270 + https://linkinghub.elsevier.com/retrieve/pii/S0306261920305092 + 10.1016/j.apenergy.2020.114997 + 114997 + + + + + + + DuffieJohn A. + BeckmanWilliam A. + BlairNathan + + Solar engineering of thermal processes, photovoltaics and wind, 5th edition + John Wiley & Sons + 2020 + 978-1-119-54028-1 + 10.1002/9781119540328 + + + + + Guide to ISO 24194:2022 Power Check - procedure for checking the power performance of solar thermal collector fields + + TschoppDaniel + OhneweinPhilip + MehnertStefan + EmbergerLukas + + 2025 + 10.5281/zenodo.16954914 + + + + + + TschoppDaniel + OhneweinPhilip + Hamilton-JonesMarnoch + ZaunerPeter + FeierlLukas + MoserMaria + ZellingerMichael + KloibhoferChristian + KorenMartin + MehnertStefan + DuretAlexis + JobardXavier + PaulettaStefano + GiovannettiFederico + SchieblerBert + + SunPeek open-source software for ISO 24194 performance assessment and monitoring of large-scale solar thermal plants + International Sustainable Energy Conference - Proceedings + 20240424 + 20240614 + 1 + 2976-2030 + https://www.tib-op.org/ojs/index.php/isec/article/view/1248 + 10.52825/isec.v1i.1248 + + + + + + TschoppDaniel + OhneweinPhilip + FeierlLukas + Hamilton-JonesMarnoch + + Digital tools for solar thermal plant monitoring. A handbook for plant operators and associated stakeholders. Version 1.0 (june 2024) + DIH Süd + Graz + 2024 + 20240626 + 10.5281/zenodo.12523699 + + + + + + AndersonKevin S. + HansenClifford W. + HolmgrenWilliam F. + JensenAdam R. + MikofskiMark A. + DriesseAnton + + Pvlib python: 2023 project update + Journal of Open Source Software + The Open Journal + 2023 + 8 + 92 + https://doi.org/10.21105/joss.05994 + 10.21105/joss.05994 + 5994 + + + + + +
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