Experiments showed that by means of a standard electronically controlled pump, type UPE 2000 from Grundfos it is possible to control the flow rate in a solar collector loop in such a way that the flow rate is strongly influenced by the temperature of the solar collector fluid passing the pump. The flow rate is increasing for increasing temperature.The flow rate at the high temperature level is typically 70 % greater than the flow rate at the low temperature level.Further, the energy consumption for the electronically controlled pump in a solar heating system will be somewhat smaller than the energy consumption of a normal ciculation pump in the solar heating system.Calculations showed that the highest thermal performances for small SDHW systems based on mantle tanks with constant volume flow rates in the solar collector loops are achieved if the flow rate is situated in the interval from 0.2 to 0.3 l/min. per m^2 solar collector for combi tank systems and in the interval from 0.3 to 0.4 l/min. per m^2 solar collector for preheating systems. Further, calculations showed that by means of an advanced control strategy for the flow rate - for instance if the flow rate is directly proportional to the temperature difference between the solar collector and the bottom of the mantle - an increase of about 1% of the thermal performance is possible.Finally, calculations showed that the highest thermal performance for large SDHW systems with constant volume flow rates in the solar collector loops are achieved if the flow rates in the solar collector loops are between 0.15 and 0.2 l/min. per m^2 solar collector. Also for large systems an increase of about 1% is possible by means of an advanced control strategy for the flow rate.Most likely, better control strategies than the investigated control strategies can be found. However, it is unlikely that significant thermal increases can be achieved by means of advanced control strategies.
|Title of host publication||EuroSun´96. 10. Internationales Sonnenforu. Proceedings|
|Place of Publication||MÜNCHEN|
|Publisher||DGS Sonnenenergie Verlags|
|Publication status||Published - 1996|
|Event||EuroSun 1996 - Freiburg, Germany|
Duration: 16 Sep 1996 → 19 Sep 1996
|Period||16/09/1996 → 19/09/1996|