Lifetime Performance Assessment of Thermal Systems : Studies on Building, Solar and Disctrict Heating Applications

Abstract: The main questions today concerning thermal systems are their economical and environmental impacts. These entities are generally, at present, assessed on the basis of operation performances of newly installed/designed systems, during an assumed lifetime period. While this is the common way of perceiving thermal systems, performance-over-time will change as an effect of degradation, and not solely of different operation scenarios. How and to what extent is the question that needs assessing in order to evaluate if these changes will jeopardise the intended system performance requirement, hence service life (SL). The lack of knowledge/approaches and tools for assessing durability and performance-over-time of thermal systems complicates the task of incorporating these aspects in engineering. In turn, this pro-active assessment and analysis is in line with today’s performance based directives, laws and regulations; of which the working life is an essential part. The durability of materials, components and systems is not a topic that is an end in itself, but becomes a vital part in a comprehensive perspective as sustainability. The lifetime performance assessment of thermal systems, as presented in this thesis, shows that it is a vital part of the R&D in the quest of sustainable energy/thermal systems and energy use. This thesis gives knowledge to the thermal (energy) system/technology R&D and engineering sector, regarding durability and lifetime performance assessment methodologies; but also to the durability of construction works sector, regarding the needs for assessing lifetime performance of materials and components in relation to system performance. It also presents descriptions of requirements on construction works. Specifically, the studies presented in the thesis show how durability and lifetime performance assessment of thermal systems may be sought, with knowledge on: methodologies, exposure test set-ups, modelling and the attainment and use of adequate tools. The main focus is on performance-over-time modelling, tying material/component degradation to altered thermal performance, thereby attaining performance-over-time assessment tools to be used in order to incorporate these aspects when engineering thermal systems; hence enabling the forecasting of SL. The presented work was predominantly done in association to the EU project ENDOHOUSING. The project developed a solar-assisted heat pump system solution, with heat storage, to provide the thermal energy to meet space heating, cooling and hot water requirements for domestic houses in different regions of the EU. The project constituted the platform for the work presented in this thesis, thereby outlining the main context with studies on durability and lifetime performance of: flat plate solar collectors ground heat sources/storages and interaction with a heat pump system evaluation of the ENDOHOUSING solar-assisted heat pump system The thesis also presents a study of SL prediction and estimation of district heating distribution networks (an additional thermal system application). In this particular context, the Factor Method is proposed as a methodology. The main issue of lifetime performance of thermal systems is how and to what extent performance reduction in individual materials or components influence the overall system performance, as the essence of energy/thermal system sustainability is system performance.