Performance evaluation of a solar heating plant in Ellös municipality

Abstract

A performance evaluation on a newly built solar heating plant in Ellös municipality was carried out. The plant generates heat for a district heating network via a boiler system (4MW), 1000m2 of solar collector arrays (700kW) and utilises a hot water storage tank (200m3). Logged plant operational data for May, June and July 2011, was analysed for correct system operation. The return network temperature to the plant was noted to be too high. This high temperature limited the solar collectors contribution to the storage tank to operating temperatures above 60.6°C. Further data analysis, indicated that the distribution network substations may be contributing to this high return temperature through incorrect settings or faulty equipment. Four major stations were pinpointed for inspection, Hallberg Rassy boat manufacturing yard, Strandgärden retirement home, Ellös School and Sjogården hotel. A simplified model of the plants current operation settings was created in POLYSUN. The network piping was modelled as a yearly constant forward (74.6°C) and return (60.6°C) temperature, along with having a variable hourly flowrate of hot water drawoff equating to 344,000m3. These inputs were calculated from the logged summer months data and monthly substation data available. The model was comparable with the summer month’s logged data under hot water being demanded, boiler heat being supplied and solar heat being supplied. Simulations were run to optimize the plant operation. It is recommended to increase the plants solar collectors to 2000m2, and reduce the return temperature to 50°C, which results in an annual 7% fuel saving for the boiler.