Standalone Photovoltaic Direct Pumping in Urban Water Pressurized Networks with Energy Storage in Tanks or Batteries

Abstract

Photovoltaic energy production is nowadays one of the hottest topics in the water industry as this green energy source is becoming more and more workable in countries like Spain, with high values of irradiance. In water pressurized systems supplying urban areas, they distribute energy consumption in pumps throughout the day, and it is not possible to supply electromechanical devices without energy storages such as batteries. Additionally, it is not possible to manage energy demand for water consumption. Researchers and practitioners have proven batteries to be reliable energy storage systems, and are undertaking many efforts to increase their performance, capacity, and useful life. Water pressurized networks incorporate tanks as devices used for accumulating water during low consumption hours while releasing it in peak hours. The compensation tanks work here as a mass and energy source in water pressurized networks supplied with photovoltaic arrays (not electricity grids). This work intends to compare which of these two energy storage systems are better and how to choose between them considering that these two systems involve running the network as a standalone pumping system without being connected to electricity grids. This work also calculates the intermediate results, considering both photovoltaic arrays and electricity grids for supplying electricity to pumping systems. We then analyzed these three cases in a synthetic network (used in earlier research) considering the effect of irradiation and water consumption, as we did not state which should be the most unfavorable month given that higher irradiance coincides with higher water consumption (i.e., during summer). Results show that there is no universal solution as energy consumption depends on the network features and that energy production depends very much on latitude. We based the portfolio of alternatives on investments for purchasing different equipment at present (batteries, pipelines, etc.) based on economic criteria so that the payback period is the indicator used for finding the best alternative, which is the one with the lowest value.

Converting a Water Pressurized Network in a Small Town into a Solar Power Water System

“…We computed the monthly energy consumption and production to confirm December as the most unfavorable month. This month had the lowest ratio between solar radiation and water needs, which coincides with earlier works [71].…”

“…Two options appeared: direct pumping (without head tanks) and indirect water supply (throughout the head tanks). We considered the first in [71], and we analyzed the second cases (indirect supply with head tanks as a guarantee for emergencies) found according to the municipality water precedence. The first peculiarity is apparent considering the number of water resources, whether just one (groundwater, superficial water bodies, desalination, etc.)…”

“…We dealt with the intensity of solar radiation as measured in the climatic station. Many investigations have presented the solar irradiation level as being the lowest in winter and the highest in summer [71,81,82]. As a result, the irradiation values in four months are far below the average value.…”

“…Step 4: Calculation of the number of PV arrays. We calculated the minimum number of solar panels to produce more energy than the energy demanded by the WPN [51,71]. This resulted in a 12 × 1 vector that showed the number of modules for every month (the number of solar PV modules required being the greatest of these values).…”

“…We analyzed alternatives from converting the WPN into a SPWS with energy storage in tanks, and a hybrid solution supplying energy from PV arrays in the irradiance hours and electricity grids. We compared which of these opportunities was better and how to embrace them [71]. Earlier results suggest that no universal solution exists in this problem.…”