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Automated Optimization of Solar-Thermal Systems Using Software in a Loop

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Making solar thermal systems less expensive, often results in a lower system efficiency. However, the cost-benefit ratio is relevant from the perspective of the consumer. The complex impact of component-related and system-related design parameters on the economics of a complete system makes the evaluation and economical optimization difficult. Therefore, a complete simulation environment has been developed, which can automatically optimize solar-thermal systems, including collector and system parameters. The main collector module consists of a one-dimensional thermal model that was validated with a commercial solar collector. The efficiency curve and the production cost were calculated as a function of several design and construction parameters. The collector module was linked to the commercial software Polysun®, so that parametric studies can be performed with minimal effort. Optimization problems can be solved by using the Matlab® optimization toolbox. The simulation environment was used for sensitivity studies and optimization problems in order to analyze the impact of collector design-parameters with respect to system cost, system yield and economic values. We will demonstrate how a collector can be optimized and how the ideal system parameters like collector number and storage volume can be easily calculated. Finally, we will show how the optimizer is used for a given system in order to find ideal values for the absorber-sheet thickness and the number of pipes. Due to the holistic approach, the application of this tool set can be used for collector development as well as for system planning.

>> Download PDF (American Journal of Energy Engineering)

First solar hydrogen storage in a private building in Western Switzerland: building energy analysis and schematic design

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Buildings have a great potential to produce their own electricity thanks to affordable photovoltaics and available area roofs and facades. To be self‐sufficient over the year, the electricity converted to hydrogen by electrolysis during the sunny season can be re‐used with the help of fuel cells during the winter season. Self‐sufficiency of the building as well as a drastic carbon emission reduction can be obtained thanks to the introduction of PV systems coupled with Hydrogen seasonal storage. For Solar Hydrogen project, a schematic design phase is mandatory : dimensioning of the PV and storage systems, suggestion of reliable technologies available on the market, needed infrastructures and security. In this article, we introduce the case study of the first private building that will be equipped with solar hydrogen storage in western Switzerland. Dimensioning is performed with the help of the Polysun Simulation software and specific add‐in modules in python.


>> Download PDF (Paper CISBAT 2019 conference)

Vallidation of an Ice Storage Model and its Integration into a Solar-Ice System

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Ice storages allow the storing of solar heat in a compact volume for the later use as source for a heat pump that provides heat for a building. In the paper a novel ice storage with 2 m3 water volume is described which contains heat exchanger plates for extracting the latent heat. Most of the components of the storage are made of stainless steel ensuring a long service life time. We present a detailed numerical model for heat exchanger plates that was implemented into the system simulation software Polysun. The model allows now for the first time to simulate ice storages with heat exchanger plates in Polysun. The accuracy of the modelling approach is evaluated based on lab measurements. The new ice storage model was implemented into a system simulation template in Polysun which was designed according to a field installation. The field installation includes three of the novel ice storages and will be used for the validation of the system template. The system template can be used as a design tool for solar-ice systems.


>> Download PDF (Paper EuroSun 2018)

BIM Use-Case: Model-Based Performance Optimization

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This contribution demonstrates the application of a building information modeling (BIM) use case including solar thermal collectors, photovoltaics (PV) and passive solar heating. It aims to close the performance gap that results from inconsistencies between the individual planning phases. Furthermore, it is shown how the pairing of the building project with a digital twin allows to set up predictive maintenance services and minimize the downtime of heating systems. Simulation software is used to create coupled models of the building and its facilities. For a case of PV combined with a heat pump and passive solar heating, this paper shows how the digital model is continuously and automatically updated as conditions change. With a focus on the building’s energy demand, control parameters are optimized in alignment with the hardware. Thus, the energy demand is kept within the close range of the original estimation throughout the standard planning phases.


>> Download PDF (Paper EuroSun 2018)

Master’s thesis: Development of model-based control applications compliant with IEC 61499 for building energy systems with a focus on photovoltaics

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Political marginal conditions for PV systems, such as feed-in limitations have resulted in the need for intelligent operation strategies. Proprietary solutions available on the market today are costly and intelligent controllers for building energy systems can thus be classified as luxury products. There is a need for generic software based on standards for the control of multi-generator systems. This thesis aims to provide an open source solution that can be used on a variety of inexpensive hardware. Communication libraries that enable co-simulations between IEC 61499 control systems and simulation software (Matlab® and Polysun®) are developed. Using the libraries and simulation tools, models and algorithms are transferred to IEC 61499 control applications with the industry compatible, open source environment 4diac. The applications are then deployed and prepared for use in the field.


>> Download PDF (Master’s thesis)

Teaching Renewable Energy Systems

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Experience in using simulation software for teaching solar energy and heat pump applications are presented at the Eurosun 2016 conference. The authors discuss suitable didactic concepts specifically developed for teaching renewable energy and energy efficiency topics. Two main advantages of applying simulation software in solar education are identified: 1) simulation can provide an understanding of data that is otherwise not accessible (e.g. cumulated operating hours and number of starts of a heat pump depending on control strategy); 2) use of simulation software in teaching have a positive influence on the motivation and attitude of the students. Finally, different international teaching programs are discussed, in which simulation software currently plays a major role. It is analyzed how education programs might have to be adjusted for different cultures and industries.


>> Download PDF (Paper EuroSun 2016)