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. Theplant generates heat for a district heating network via a boiler system (4MW), 1000m2 of solar collectorarrays (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 theplant was noted to be too high. This high temperature limited the solar collectors contribution to thestorage tank to operating temperatures above 60.6°C. Further data analysis, indicated that thedistribution network substations may be contributing to this high return temperature through incorrectsettings or faulty equipment. Four major stations were pinpointed for inspection, Hallberg Rassy boatmanufacturing yard, Strandgärden retirement home, Ellös School and Sjogården hotel. A simplifiedmodel of the plants current operation settings was created in POLYSUN. The network piping wasmodelled as a yearly constant forward (74.6°C) and return (60.6°C) temperature, along with having avariable hourly flowrate of hot water drawoff equating to 344,000m3. These inputs were calculated fromthe logged summer months data and monthly substation data available. The model was comparable withthe summer month’s logged data under hot water being demanded, boiler heat being supplied and solarheat being supplied. Simulations were run to optimize the plant operation. It is recommended toincrease the plants solar collectors to 2000m2, and reduce the return temperature to 50°C, which resultsin an annual 7% fuel saving for the boiler.