Impact of Small Weather Data Time Steps on the Simulation of Solar and Heat Pump Systems
Abstract
For the simulation of solar thermal systems mainly hourly based weather data are used today. The question arises whether short term fluctuations of e.g. solar irradiation that may be present in measured weather data with smaller time resolution has an impact on the result of solar thermal system simulations. To study the influence of weather data time resolutions, different systems that combine solar collectors and heat pumps were simulated twice in TRNSYS17. One time with a weather data time resolution of six minutes, and one time with hourly averaged weather data from the same source of measured weather data from Zurich (Switzerland). Starting with a reference solar and heat pump system simulation, single parameters of the system were varied (e.g. collector area, thermal capacity, specific mass flow rates through the collector loop) in order to analyse the dependency of the difference between small time resolution and hourly weather data simulations. In general, the influence of weather data time resolution was higher when using stratifying charging in the thermal energy storage, for large collector areas, and for large specific mass flow through the collector field. The difference of seasonal performance factor, electricity consumption, and solar collector yields were about ±1.2 % at maximum when hourly averaged weather data was used instead of six minute profiles.