By Peter Jorsal, Product Manager, LOGSTOR
Experience with solar networks Especially Denmark has many years of experience with establishing large-scale solar district heating projects, and therefore has a vast experience with the district heating system for solar panel fields, collecting heat from the sun. In many cases a dearly bought experience. The design of the first district heating systems for solar district heating projects was typically based on the knowhow from traditional district heating in cities both as regards the design of the pipe system as well as the choice of products, like casing joints and components.
The knowhow and attention to the conditions, to which a solar district heating project is exposed, simply were inadequate. This applies to the temperature, but especially to the number of temperature cycles to which district heating pipes are exposed during the service life of the system. The number of temperature cycles taken into account were far from sufficient. The number of temperature cycles in a pipe system for a solar district heating field may be 40 times higher than the number in a conventional district heating system, designed in accordance with the European standards. If this is not taken into account in the design of the system and choice of products, there is a risk of the casing joints peeling off and fatigue failure in T-pieces, bends, and other components. See Fig. 1-5.
Fig. 2 - Moisture spread, stemming from a casing joint, damaged by large movements.
Fig. 1 - Branch, damaged by large movements.
Fig. 3 - Released copper ions from brass valve, causing corrosion of the steel pipe. The damage is on the return pipe. No damage on the flow pipe.
Fig. 4 - Shrink wrap peeled off due to the large number of movements.
Fig. 5 - Dislocated casing joint due to the large number of movements.
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