Abstract
Solar heat in solar thermal combisystems is usually used via a buffer storage. Alternatively, the solar collectors may be connected
directly to the space heating circuit in order to store the heat in the building itself. Such a direct solar integration is investigated within
system simulations for different layouts and heating elements. The operation of these systems requires a control strategy, which distributes
the solar heat optimally between the potential heat sinks leading to the lowest overall energy consumption. This way a solar
fraction may be achieved which is comparable to usual combisystems equipped with a three times larger buffer storage. A prototype
of one of the investigated heating concepts within a single family house proofs the functionality of the system concept and the high solar
yield, particularly at low radiation levels. The direct solar heating increases the solar fraction of combisystems significantly or alternatively
decreases the necessary storage volume considerably if a certain system performance is desired.
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