For the simulations daily and weekly load variations for the DHW with hourly resolution were created in order to separate between the ambient temperature dependant SH and independently varying DHW loads. To achieve realistic load profiles, they were created based on measurements from operational plants.

1.1. Measured load profiles

Measured hourly load data was obtained from six plants of various sizes. Measured monthly total loads were obtained from 18 plants of various sizes. It was found that the studied load profiles are basically of the same shape, i. e. mostly SH with a comparatively small summer loads (DHW and partly or mostly distribution losses), lower than 15% of peak load.

1.2. Load profiles for simulation studies

Based on the measured data representative generic load profiles were created. The DHW profile was created based on data when the SH is off or small. As the measured data included only the ambient temperature, no simulations regarding solar irradiation can be made for the same data set. Thus the SH load profile was created by matching visually the simulated to approximate the measured load characteristics while keeping the same peak load and approximate yearly total load. Case 1 represents the majority of the plants. As in the studied plant portfolio all cases except one had low summer load, a

fictive high summer load Case 2 was created by simply scaling up the DHW consumption of Case 1 and reducing the SH load keeping the same peak power. The studied climate data was TMY2 for Jokioinen (Finland), latitude 60.8°.

2. Simulations

SHW win was chosen as simulation tool because of ready and tested system models and it has also been used in a similar project earlier by TUG in Austria [1]. Yearly simulations were done with a sub­hourly resolution.