Available online at www.sciencedirect.com ScienceDirect Procedia Engineering 162 ( 2016 ) 503 – 510 International Conference on Efficient & Sustainable Water Systems Management toward Worth Living Development, 2nd EWaS 2016 Pressure management and energy recovery capabilities using PATs Menelaos Patelisa, Vasilis Kanakoudisa,*, Konstantinos Gonelasa aDepartment of Civil Engineering University of Thessaly, Pedion Areos, Volos, GR 38334, Greece Abstract Hydro-turbines are widely used in small water energy production plants in order to turn water kinetic energy to electricity. PATs (Pumps working As Turbines) are micro-turbines (small sized compared to the usual ones) working on “reverse mode” compared to the usual pumps. Installation of a PAT aims to produce energy along with managing/keeping the downstream pressure to a desired level. PRVs (Pressure Reducing Valves) are used to decrease pressure aiming to reduce water losses linked to this extra pressure potential available. The current study focuses on the possibility to replace a PRV with a PAT in a real water distribution network checking its ability to reduce pressure to acceptable levels as well as produce significant amount of energy. The water distribution system of Kozani city (in Northern Greece) is used as the case study network. Various operating scenarios regarding the exact location of the PAT were checked in the network’s calibrated hydraulic model with interesting results. ©© 2016 2016 The The Authors. Authors. Published Published by Elsevierby Elsevier Ltd. Ltd.This is an open access article under the CC BY-NC-ND license (Peer-reviewhttp://creativecommons.org/licenses/by-nc-nd/4.0/ under responsibility of the organizing). committee of the EWaS2 International Conference on Efficient & Sustainable Peer-reviewWater Systems under Management responsibility towardof the organizing Worth Living committee Development. of the EWaS2 International Conference on Efficient & Sustainable Water Systems Management toward Worth Living Development Keywords: PATs; PRVs; water losses 1. Introduction Hydro-turbines are widely used in small water energy production plants in order to turn water kinetic energy to electricity. Pumps working as Turbines (PATs) are micro-turbines (small sized) working on “reverse mode” compared to the usual pumps. They are being installed to recover a significant part of the available kinetic/flow energy inside a * Corresponding author. Tel.: +30 24210 74156; fax: +30 24210 74135 E-mail address: [email protected] 1877-7058 © 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of the EWaS2 International Conference on Efficient & Sustainable Water Systems Management toward Worth Living Development doi: 10.1016/j.proeng.2016.11.094 504 Menelaos Patelis et al. / Procedia Engineering 162 ( 2016 ) 503 – 510 pipe and convert this energy to electricity [1]. Produced electricity can be either high or low voltage (produced power usually varies from 1 to 200 KW). Electric energy can be used to cover part of the energy needs of the Water Distribution Network (WDN) itself, or can be sold to bring revenues to the water utility in charge. PATs are pumps that contribute to a self-sufficient network as far as energy is concerned. Energy prices rise significantly nowadays and concern about environmental safety is growing too. New renewable energy sources (RES) are required as an alternative to fossil fuels as mankind’s energy needs rapidly rise. PATs are such an alternative RES and offer solution to the energy efficiency concern of water utilities. Although it is hard to detect and measure excessive energy and pressure potentials, after thorough studies and cross-checks, suitable places for energy production in WDSs can be spotted. PATs are reliable producers of renewable energy [2]. Installation of a PAT in a water distribution network must comply with all its operational restraints. An additional great advantage of a PAT is its ability to reduce the downstream pressure, even close to zero. With certain modifications and operation patterns, some types of PATs are capable of maintaining a desired level of pressure control (such modifications have mechanical character and determine energy production as well as pressure management of a PAT but they do not consist research topic for this article). In case of PATs controlling the downstream pressure, energy produced is reduced, thus benefits achieved are increased. Mechanical equipment and operation mode of a PAT, demand high dedication as a wrongly selected PAT can bring discouraging results. Pressure Management (PM), which is usually the best way to reduce the Non-Revenue Water (NRW) level in a water distribution network, is achieved mainly by forming (dividing the network into several) District Metered Areas (DMAs) followed by Pressure Reducing Valves (PRVs) installation in several DMAs’ entering points. PATs are introduced as another option to perform Pressure Management as well as recover “green energy” from the water distribution network itself. As the abbreviation PAT (Pump As Turbine) reveals, PATs are turbines that work in a way similar to pumps. This mechanical device has the same operational mode of a pump but instead of consuming energy to boost water, it takes advantage of water flow to produce electricity. As PATs operate similarly to other regular pumps, their implementation does not require many modifications to take place in the network. No specially trained personnel is needed to support and perform maintenance works related to PATs’ operation. Additionally, spare parts for PATs are easy to find in the market. Purchase values and other implementation costs are quite low and in any case comparable to those of regular pumps. The most significant requirement is the existence of a naturally produced energy surplus. There have been many examples of PATs’ implementation around the world during the last two decades [3], [4]. Still, the opportunity to recover energy from a water distribution network is not widely spread and adopted. Most of the PATs installation cases have taken place in the water supply mains of water distribution networks [5], where water is supplied in large diameter pipes from springs or drillings, sometimes covering long distances and starting from high altitudes. Except from a minimum of pressure and flow inside a pipe, the produced energy must have a purpose to exist. Energy production usually takes place near the energy consumption/demand site, otherwise power transmission network is required. PATs unfold great opportunities [6], but thorough study is needed before equipment selection and installation. The complexity of the problem is high and it can easily turn such a promising investment into a failure. In order to implement PATs successfully, water utility managers need to cooperate with experienced researchers and equipment providers. An example of a PAT implementation project in the water distribution network of Kozani city (in Northern Greece) is presented as a case study in this paper. 2. Case study and methodology Kozani city, capital of Kozani County in West Macedonia Region, Greece, is located in the northern part of Aliakmonas river valley. The city lies 710 metres above sea level, 15 Km northwest of the artificial lake Polyfytos, 120 km south-west of the city of Thessaloniki (the second largest Greek city after Athens, the capital city), between Pieria, Vermio, Vourinos and Askio mountains. The population of Kozani municipality exceeds 70,000 people. The consumers being served by the local water utility (named DEYAK) are almost 50,000 people. Its well-designed water distribution network is widely spread covering a huge area (Figure 1), including the entire city and its expansions in more than ten suburbs. The total daily water volume supplied by the water distribution network reaches its peak (22,744m3) on July, while dropping to just 18,584m3 on January. Figure 2 presents the total water volumes (in a 4- months basis following the billing period adopted by DEYAK) produced and consumed (measured) in Kozani in 2009 Menelaos Patelis et al. / Procedia Engineering 162 ( 2016 ) 503 – 510 505 and 2010 [9]. Kozani during winter is being supplied by Ermakia springs (to the north), while during summer by Vathylakkos boreholes (to the south). There are three pressure zones formed: a) a limited higher (BLUE) zone at the north (altitude ranging from +750 to +800); b) a medium (RED) zone in the middle (altitude ranging from +710 to +750); and c) a low (GREEN) zone at the south (altitude ranging from +610 to +710), covering 60% of the total water demand (Figure 1). There are two main water storage tanks and also a tank system supplying only the middle zone. a b Fig. 1. Kozani city WDN: (a) water tanks, pressure zones [8]; (b) DMAs. Fig. 2. Water extracted & consumed in the city of Kozani. The water distribution network of Kozani city was chosen for this study due to the high altitude difference observed in Kozani’s topography. Thus, as already mentioned, the local (municipal) water utility (DEYAK) operates the network by supplying water into three pressure zones. The water distribution network has been further (virtually) divided into several DMAs through studies performed by the authors in the near past. Due to the high altitude difference observed, the network works sufficiently by gravity. There are nodes in the network where the available operating pressure gets as high as 10 atm, causing major problems to the network’s operating status and life expectancy. Also water losses are increased and Non-Revenue Water (NRW) reaches 58% of the System’s Input Volume (SIV) [9]. 506 Menelaos Patelis et al. / Procedia Engineering 162 ( 2016 ) 503 – 510 Virtual formation of the 24 DMAs took place using the network’s hydraulic simulation model that was recently developed. The segmentation of the network was done by “installing” isolation valves in the pipes that define the DMAs’ borders.