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WP3 - Collectors (Deliverable 3.1)

The full report is confidential and will not be distributed to the public. However, a brief summary of the contents are given here.

New breakthroughs for materials and design are focused from the point of view of reducing the cost of the collectors as well as from the point of view of resistance and lifetime for the operation in solar and heat pump systems where the collector can be operated below the dew point of the ambient air. Polymeric materials reveal a large cost reduction potential for low temperature collectors. Aluminium is regarded as a low cost metal for absorber production but is more prone to degradation than e.g. stainless steel or copper if it is wetted due to collector operation as a source for the heat pump. The possible use of roofing and cladding materials as solar absorbers is outlined. A review of the present status in the field of selective coatings and their weather resistance has been carried out. Thickness insensitive selective paints may be an interesting alternative to thin layers on metal where the stability of the metal surface under condensing conditions is a concern.

Solar air collectors still offer a high investigation potential in the field of design optimization, enhanced ventilation for ambient heat collection or combination with PCM or liquid absorbers. Optimization of solar liquid collectors seems to be further advanced. The focus here lies in cost reduction, adaption to the operation below dew point and in the hybridization for the efficient and reliable use of solar heat with ambient heat to be used for the heat pump, possibly in combination with a reduction of stagnation temperatures.

For the combination with heat pumps, the application of hybrid photovoltaic/thermal (PV/T) collectors is of particular interest since both heat and electricity from the PV/T may be used by the heat pump and the heating system. Developments and breakthroughs in the field of PV/T absorber construction and collector design (air, liquid, glazed, unglazed) have been reviewed. Available mathematical models for PV/T collectors have been reported.

The cross-cutting issue of building envelope integration of solar collectors is reminded in several chapters from the point of architectural aspects (enhancing market penetration), replacement of the envelope construction with a heat source (cost savings) and synergy effects (lowering losses from collectors).

Seven breakthroughs have been selected for further evaluated in phase 2 of the MacSheep project, where energy savings potential and costs are evaluated. An outline has been provided how these breakthroughs will be evaluated within the project by the different participants.


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