A Techno-Economic Investigation on Insulating Glass Solar Thermal Flat-Plate Collectors for District Heating Systems in Europe
The large-scale integration of solar thermal collector arrays into district heating networks has emerged as a global trend with the objective of decarbonising heating supply. To accelerate the expansion of this renewable heating technology, it is advantageous to achieve significantly lower heat generation costs compared to fossil fuel-based alternatives. However, over the past decades, this has not been the case when considering the long-term averages. Furthermore, the subsidisation undertaken to compete with fossil-based heating systems and the financial risks associated with high upfront investment demonstrates the need to enhance cost-effectiveness. This study investigates the techno-economic performance of novel insulating glass flat-plate collectors compared to market-available collector types for European solar district heating systems. These collectors combine insulating glass unit manufacturing technology with the design principles of conventional flat-plate solar thermal collectors. While the concept was introduced more than a decade ago, the focus was on domestic use rather than large-scale applications. This thesis presents a novel design created specifically for this application. However, its performance and economic viability in large-scale district heating applications have not yet been thoroughly assessed. The aim of this thesis is to address this gap through a combination of theoretical and experimental analyses both on component level and system level. A literature review was conducted to identify previous research findings in the field, followed by numerical modelling and optimisation of the collectors. Experimental investigations include the production of prototypes, thermal performance measurements, and durability assessments. In addition, key system-level performance indicators were evaluated, and a techno-economic analysis was carried out to compare the potential heat generation costs of the novel collectors with conventional systems. The findings indicate that the novel insulating glass solar collectors exhibit competitive performance, demonstrating a relative efficiency increase of 10% in comparison to the average of conventional collectors. However, at the system level, this advantage is partially offset by additional hydraulic connections and increased thermal capacity, leading to an overall annual performance increase of 6.5%. Economic analyses reveal that the specific total costs of insulating glass collector systems are approximately 10% higher, mainly due to increased hydraulic costs. Consequently, the levelised cost of heat is 1.4 €/(MWh) or 2.6% higher than that of conventional systems. However, definitive conclusions regarding the superiority of either system could not be drawn due to the absence of economic reference data. The overall heat generation costs of the novel system were found to be comparable to those of conventional technologies, thereby demonstrating its viability for large-scale solar district heating applications. In addition, the possibility of further optimisation in terms of collector design, system hydraulics, and mounting system was identified, which suggests a promising outlook for large-scale solar district heating applications.
Networked Digital Library of Theses and Dissertations