District heating is environmentally-sound, convenient and cheap. It’s even cheaper in the Hagenow public utilities company – with the smart use of a solenoid driven metering pump delta® from ProMinent.
Two become one
In the german region Mecklenburg-Vorpommern, around 30 kilometres to the south west of the state capital Schwerin, over 2,700 homes are supplied with district heating by the Hagenow public utilities company. The total volume was over 14 million kilowatts in 2015. To maintain constant pressure in the district heating system, for over 20 years the Hagenow system used external pressure maintenance controlled by pumps – a popular principle in Germany in almost all district heating systems. Then an electrical engineer had the smart idea of solving pressure maintenance in a different way: First shut down the two installed 1.5 kilowatt pumps, which constantly circulate the compensation water and thus work against the relief valves. Then replace them with a single metering pump which is only actuated when the pressure falls and meters the required volume of water.
- Supply of district heating to over 2,700 households
- The flow temperature of the hot water is 75-90°C, the return temperature is 35-55° C
- Energy generation: around 70 % from renewables (waste heat from electricity generated from biogas); around 30% from natural gas to compensate for downtimes and cope with peak loads
Gentle and smooth metering
This solution has been running successfully for two years now. ProMinent’s solenoid driven metering pump delta® maintains constant pressure in the Hagenow district heating network and has replaced two 1.5 kilowatt pumps. The solenoid-controlled metering pump compensates for falling pressure by gently and smoothly metering the precise amount of water needed into a diaphragm expansion vessel. It is the perfect solution for this application, thanks to the patent-protected power end in the metering pump, in which a distance sensor records how far the diaphragm deflects and transmits the position to a microprocessor. It compares the value during the stroke with the set metering characteristics and calculates the precise amount of energy required for the movement of the diaphragm. Power electronics finally convert the value into current, producing very gentle and perfectly matched suction or pressure strokes.
Significant cost savings
- Move from permanent to demand-driven operation
- Lower power, maintenance and servicing costs
- € 5,000 of energy costs are saved every year by changing over to a pressure maintenance system with a solenoid driven metering pump delta®