A proper model for the regulating strategy of the system is needed to predict the distribution of gains and losses via the Solar Window. The complexity and interrelations between the different functions is a challenge for the modelling, which needs to integrate the spatial surrounding. A detailed model could be of much use for a regulation of an automated system for best performance and comfort.

The level of automation for the system is object for further studies. A range of products with different standard, from fully manual to fully automatic, is a likely development. It is however of importance that the control-function can be overridden manually at all times due to direct response from the user.

Performance of the system has been analysed separately for passive gains, active thermal gains and PV electricity yield. According to the proposed regulating schedule, passive gains are estimated to 210 kWh/m2 annually. However, it is not examined how much of this is usable. The performance of the fully concentrated PV/T absorber is estimated to 79 kWh/m2 of electricity, and at least 155 kWh/m2 of heat for domestic hot water. Following the proposed regulating schedule, these figures might be reduced. For a more accurate and integrated analysis, long-term outside measurements will be made for the full window prototype with PV/T absorbers.

Cost estimations are dependent on where the system border is drawn, since the system also is the building envelope. For comparison with conventional solar energy systems, it might be fair to withdraw the window and sunshade cost if the same is done for the building material the conventional collector replaces. Production cost for the Solar Window excluding the glazing is estimated to approximately €250/m2, but more thorough calculations need to be made.

Acknowledgements

This work was supported by the Swedish Energy Agency and Formas, the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning.