Using the calculation tool SCFW, the solar net gain of a solar thermal plant integrated in a district heating network can be calculated. The calculation follows strictly the formulas of ScenoCalc and DIN EN ISO 9806 on the one hand and considers relevant decreasing effects of the whole system on the other hand. These effects contain heat capacity of collectors, heat losses of pipes, fittings and optional storage, antifreeze protection, and heat exchanger. In case of heat exchangers the increasing collector average temperature is more relevant than heat losses. These futher calculations enable to calculate the solar net gain at the point where it is fed into the district heating network. The weather data and the load profile of the district heating network is taken into account in the hourly calculation.
SCFW is implemented in an Excel-Workbook and calculates formulas according to the values the user chooses. There is no check of the values and the user should have knowledge of the solar thermal system. The results of SCFW are first estimations and no complete system design.