The analysis of the dynamic processes in section 5 shows that there is no unique value of an effective capacity that well describes all the relevant processes. Furthermore, none of the existing procedures for the determination of the capacity is suitable for all the processes. The capacity resulting from the calculation or the J.2 procedure only poorly describes fast fluctuations of irradiance. On the other hand, dynamic effects that are caused by fluctuations of the fluid inlet temperature are strongly overestimated by the J.3 procedure.

So which determination procedure is best suited for describing realistic collector operation?

As long as one-node models are used, a compromise is needed. For this, it is important to find out for which of the mentioned dynamic processes the collector gain depends on the effective capacity. A determination procedure is only well suited if it well describes those processes where the capacity strongly influences the daily or yearly collector gains. The correct modelling of other processes is less important.2