Evaluating energy recovery potential in Murcia's water supply system

Resumen

Murcia is the 7th most populated city in Spain. Its water supply system is extensively monitored through alarge number of pressure gauges and flow meters. Murcia’s water supply network is fed from distributionreservoirs at enough elevation to avoid needing pumping stations for most of the city districts. Hydraulicresources have been evaluated throughout the water supply system. Besides the pressure reducing valves,where the assessment is quite straight forward [1], District Metered Areas (DMA) inlets have been evaluated.In these areas despite the hydraulic resources are not as great as in pressure reducing valves locations, theirlocation is quite convenient. Actually, these positions are located inside the city, therefore making easy to usethe produced energy in municipal self consumption or to provide facilities to the citizens.In order to perform such evaluation, a detailed model of the water supply network has been implemented inEPANET parting from a GIS model. The first step of the evaluation has consisted in the optimizing andvalidation of the model. Initially, the model was reviewed by comparing pressure and flow ratemeasurements in the main pipes. Then, an extensive experimental campaign was designed. In that campaignvalves were switched so that each day a set of District Metered Areas (DMA) have just one metered inlet orat the most a very short number of metered inlets, whereas having a set of pressure measurements within theDMA. The obtained data was used to minimize errors in pressure time series, optimising roughness of themain pipes through Levenberg/Marquardt BFGS algorithm using EPANET ToolKit through Epanet-Octave[2]. Important roughness proposed changes tended to be located surrounding particular points, where errorsin the GIS were located (mainly wrong diameter assignement). After patching all the errors the algorithmeased to localise, model errors were mostly below measures uncertainty, and therefore, the model wasconsidered validated.Then, the hydraulic potential at the DMAs inlets has been evaluated by tracking the “instantaneous”minimum pressure and head within each DMA, as well as the flow rate entering the DMA. So that, themaximum head and the range of flow rates is established for the turbine.At the moment, once that all of these potentials have been assessed, a turbine prototype is being designed.