Cultural heritage objects made of wood can be preserved under waterlogged conditions for many years, where decay is slowed down and the wood structure is more or less completely filled with water. Depending on the degree of degradation, finds may collapse and shrink when they are allowed to dry in an uncontrolled manner after excavation, leading to total loss of the object and its information. Conservation measures are taken to prevent damage of objects and dimensional stability is an important criterion. In this study, structured-light 3D scanning and micro-computed tomography were used to analyse the dimensional stability of wood after conservation, as well as its long-term stability. 83 samples from a reference collection established between 2008 and 2011 allowed this comparative study of the most common conservation methods at that time. The effects of conservation methods using alcohol-ether resin, melamine-formaldehyde (Kauramin 800®), lactitol/trehalose, saccharose, and silicone oil on dimensional stability were investigated. In addition, different polyethylene glycol (PEG) treatments with subsequent freeze-drying were also investigated: one-stage with PEG 2000, two-stage with PEG 400 and PEG 4000 and three-stage with PEG 400, PEG 1500 and PEG 4000. The data received from analyses of both volume and surface gave detailed information about the success of each conservation method. Attempts were made to quantify the damage patterns, specifically shrinkage, collapse, and cracks. While PEG and freeze-drying, alcohol-ether-resin, as well as the Kauramin 800® method gave the best results, analysis also highlighted the failures of each method.
District heating and cooling (DHC), when combined with waste or renewable energy sources, is an environmentally sound alternative to individual heating and cooling systems in buildings. In this work, the theoretical energy and economic performances of a DHC network complemented by compression heat pump and sewage heat exchanger are assessed through dynamic, year-round energy simulations. The proposed system comprises also a water storage and a PV plant. The study stems from the operational experience on a DHC network in Budapest, in which a new sewage heat recovery system is in place and provided the experimental base for assessing main operational parameters of the sewage heat exchanger, like effectiveness, parasitic energy consumption and impact of cleaning. The energy and economic potential is explored for a commercial district in Italy. It is found that the overall seasonal COP and EER are 3.10 and 3.64, while the seasonal COP and EER of the heat pump alone achieve 3.74 and 4.03, respectively. The economic feasibility is investigated by means of the levelized cost of heating and cooling (LCOHC). With an overall LCOHC between 79.1 and 89.9 €/MWh, the proposed system can be an attractive solution with respect to individual heat pumps.
Impressive wooden objects from past cultures can last for centuries or millennia in waterlogged soil. The aim of conservation is to bring the more or less degraded waterlogged archaeological wooden (WAW) finds to a stable state without altering the wood structure through shrinkage, collapse, and deformation. In this study, the most used methods in the conservation practice, such as the alcohol-ether resin method, conservation with the melamine formaldehyde resin Kauramin 800, a mixture of lactitol and trehalose, saccharose, silicone oil, and three different conservation methods with polyethylene glycol followed by freeze-drying were tested. The effects of the conservation agents on the structure of archaeological pine were investigated using optical light microscopy (reflected light microscopy, RLM), scanning electron microscopy (SEM), and X-ray computed tomography (XCT). Through the examinations, most conservation agents could be identified in the structure and their impact on conservation could be analyzed. In particular, it was possible to trace the incorporation of the conservation agents in the lumen, which was influenced by factors, such as wood anatomy, degree of degradation, and drying process. Differences in the mode of action of the conservation processes could also be identified in the composition of the cell wall tracheids.
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