Abstract
Already existing man-made infrastructures that create water flow and unused pressure are interesting energy sources to which micro-hydropower plants can be applied. Apart from water supply systems (WSSs), which are widely described in the literature, significant hydropower potential can also be found in district heating systems (DHSs). In this paper, a prototype, a so-called energy-recovery pressure-reducer (ERPR), utilized for a DHS, is presented. It consisted of a pump as a turbine coupled to a permanent magnet synchronous generator (PMSG). The latter was connected to the power grid through the power electronic unit (PEU). The variable-speed operation allowed one to modify the turbine characteristics to match the substation’s hydraulic conditions. The proposed ERPR device could be installed in series to the existing classic pressure reducing valve (PRV) as an independent device that reduces costs and simplifies system installation. The test results of the prototype system located in a substation of Cracow’s DHS are presented. The steady-state curves and regulation characteristics show the prototype’s operating range and efficiency. In this study, the pressure-reducer impact on the electrical and hydraulic systems, and on the environment, were analyzed. The operation tests during the annual heating season revealed an average system’s efficiency of 49%.
Highlights
Micro-hydropower plants (MHPs), whose power output is typically below 100 kW, have gained increasing attention due to their energy recovery capability in existing infrastructures [1]
A potential energy source can be found in any system that comprises water flow and unused pressure, i.e., water networks dealing with drinking water, wastewater, irrigation water, runoff water, as well as cooling and heating systems [2,3]
This paper presents an improved energy-recovery pressure-reducer (ERPR) prototype that was tested in the Cracow district heating systems (DHSs)
Summary
Micro-hydropower plants (MHPs), whose power output is typically below 100 kW, have gained increasing attention due to their energy recovery capability in existing infrastructures [1]. WSSs that are located in lower topographic areas suffer from excess pressure This energy surplus, which is commonly dissipated via pressure-reducing valves (PRVs) [5,6], can be recovered by applying MHPs. The excess pressure is mainly present in transmission pipes and between sub-grids, and inside the network and at the building entrance. The electrical regulation mode employs an inverter ensuring variable rotational speed Another system with hydropower potential is presented by a district heating system (DHS). A prototype device, a so-called energy recovery pressure reducer (ERPR) applying a centrifugal PAT, was designed [22]. The tests indicate some issues that need to be improved, such as high water temperature (bearing, generator cooling) and the ERPR’s operating range (turbine type). Operation during the annual heating season is presented and analyzed
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