Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE credits
This study was conducted to investigate operational problems of a larger solar thermal plant (> 100m²) supporting
domestic hot water (DHW) preparation. Already at the beginning of the 15 years of operation effective solar gains
fell beyond the T-SOL pre-simulated figures. In addition to that collectors were found leaking after 10 years. The
aim of the study was also to determine the causes for damaged collectors and to deliver improvement suggestions
if applicable. The solution was approached by a set of different methods. Literature review and analysis of plans,
notes and documents of the plant were accompanied by measurements and (re)-calculations and site visits.
Problems in different sectors of the plant were found. In the secondary circuit, the pump action of the heat
exchange station was permanent instead of a recommended on demand action. In terms of the DHW preparation
the lower DHW store sensor was placed in DHW circulation pipe instead of inside the store. In the primary circuit
the size of the expansion vessel was designed to small. The conception of the solar circuit and the application of
safety valving were not appropriate in terms of a partial evaporation system. Essential temperature differences
among collector cases could be attributed to incorrect assigned sensor characteristics in the system control panel.
Therefore the solar pump was not regulated well, which led to stagnation and overheating. The boiling of solar
fluid caused the safety valves to blow off and might have led to a loss of the fluids frost protection characteristics.
During the study, it was asserted that the system design as much as its implementation and maintenance (regularity
and intensity) were insufficient and led to irreversible plant damage. Different system improvements depending on
effort can be concluded from that. One example would be the adaption of layout of the existing system to the
requirements of a partial evaporation system whereas the number of collectors remains the same. Amongst others
the complete replacement of the plant is discussed.
2015.