Solutions developed

The work proposed aims for a seasonal performance factor of the system (solar and heat pump) of e.g. 6 as compared to 4.5 for the current state of the art. This will be possible by using new materials, components and ICT in an integrative approach for new system concepts where the focus is on the overall system's cost and performance. A systematic approach is used to evaluate new breakthroughs such as e.g. low-cost materials and selective paint for solar collectors that collect solar irradiation as well as ambient heat and PV/T collectors that produce heat as well as electricity. Exergetic optimization of heat pump circuits includes using de-superheating heat exchangers for DHW preparation as a by-product of the more efficient space heating operation, and variable speed controlled compressors for heat pumps that match the collector heat input to the evaporator and/or the demand.

Main results

- Hydraulic integration of the combi-storage and placement of the DHW temperature sensor according to the recommendations that have since been published by HSR SPF.
- Reduction of mixing effects in the storage that were caused by high mass flows of heat pump inlets.
- Reduction of heat losses that were caused by natural circulation through pipings for DHW and cold water supply outside of the storage.
- Correction of storage design that prevented the preheating of DHW by solar in the bottom part of the store.
These improved benchmark systems performed about 20 % better (i.e. 20 % less electric energy use) than their truly installed and tested counterparts. The four systems that were developed within MacSheep had different heat load targets for which they were optimised. Obviously, optimization for a high heat load and high supply temperatures of the heating system can lead to a quite different solution than optimization for low heat loads or low temperature heating systems. When there is not much heat to deliver in the first place, increasing energy efficiency must only be achieved by low cost solutions since the same percentage of electrical savings is much less in absolute terms of electricity cost than for a system with a high heat load. Such considerations also lead to quite different approaches for the four developed systems.