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This paper analyzes the impact of water and emission limitations on expansion planning of thermal power plants (TPPs), in Iran. TPPs need considerable amount of water for their cooling system. In Iran, water crisis of recent years has made it impossible to operate existing steam power plants in some areas, during summer season. This paper considers water availability and cost in generation expansion planning (GEP) of Iran. There are different types of water resources such as rivers, dams, treated wastewater, seawater, seawater transmission line, saline groundwater, and groundwater. Considering available capacity of water resources in each area and sorting their extraction cost in ascending order, some water consumption cost curves are derived. For this purpose, data of about 200 water resources located in different regions of Iran are analyzed. Provided GEP model includes a 15-years planning horizon and analyzes several scenarios of water availability. Although, in low water price scenarios, air temperature and height above sea level have more impact on placement of TPPs, it is different for high water price scenarios. Also, the effect of emission-related policies on GEP decisions is analyzed by considering various fuel types of TPPs, penalties for emissions, and global restrictions on greenhouse gas production. • Proposes an optimization model for generation expansion planning (GEP) that considers environmental constraints. • Analyzes the availability and price of different water resources in Iran and their effects on GEP decisions. • Examines the impact of temperature and height above sea level, on the siting of thermal power plants in Iran. • Considers decarbonization policies in the expansion planning of power plants in Iran. [ABSTRACT FROM AUTHOR]

Both energy and water are important resources for human and should be investigated in an integrated way. The paper examines the implications of improving energy efficiency for water resources to contribute to the understanding of energy-water nexus. The paper first develops a mathematical model to link energy efficiency and water withdrawals and consumption. Using the model and the UK energy and water data, the paper then investigates the implications of improving energy efficiency of thermal power technology for freshwater, tidal and sea water in the UK. Results show that when the energy efficiency increases averagely by 10%, the total water withdrawals decrease by 1.65 × 10 6 Megaliter (ML) per year, and the total water consumption reduces by 2.89 × 10 4 ML per year. The saved freshwater withdrawals account for 0.43% of total public water supply in England and Wales in 2013, and could support 138,462 households. The water resources have different sensitivity to the improvement of energy efficiency. The sea water withdrawals are the most sensitive to the improvement of energy efficiency, followed by tidal sea water withdrawals and freshwater withdrawals. Results provide significant informative implications for energy-water nexus, and suggests that it is time to consider improving energy efficiency to address the emerging energy and water challenges. [ABSTRACT FROM AUTHOR]

The energy sector of Morocco relies mainly on imported fossil fuels. The expensive import bills associated with fossils, as well as the global drive for greenhouse gas (GHG) emission reduction, have compelled the country to consider the utilization of renewable energy resources such as hydro, wind, and solar for energy generation. Power generation from wind and solar is highly intermittent hence require storage systems to guarantee supply security. Considering the abundant nature of sheep rearing in Morocco, power generation from sheep dung through anaerobic digestion (AD) can serve as an alternative power generation source to alleviate the intermittent situations of wind and solar since biomass supply for AD is not affected by the weather. Therefore, this paper evaluates the capability of hybrid power generation, using AD of sheep dung, wind, and solar in two selected areas of the Fez-Meknes region in Morocco. A mixed-integer linear programming model was implemented in A Mathematical Programming Language (AMPL) using a linear solver of CPLEX. The results of the analysis indicated that only standalone wind generation and hybrid wind/PV/biogas generation are able to meet the total load demand of the two study locations. The hybrid generation resulted in a total carbon emission of 349.30 and 3871.60 g/year at a cost of 13,088.38 and 145,394.13 $/year for Tazouta and Fez respectively in supplying the whole load of the study locations, whiles the standalone wind generator resulted in a total carbon emission of 274 and 2603 g/year at a total cost of 23,352 and 239,500 $/year for satisfying the electric load of these two regions respectively. The results shows that, hybrid solar/wind/PV is the most ideal for supplying power to the two study locations in terms of cost and load satisfaction, while the wind is the most ideal in terms of load satisfaction and carbon emissions. • Sheep dung potential for generating electric power in rural areas of Fez-Meknes. • Wind, solar and biogas electricity generation in water-stressed areas of Morocco. • Hybrid renewable energy generation. [ABSTRACT FROM AUTHOR]

A great interest has recently arisen for the sustainable supply of energy and fresh water, due to the growing demand from developing countries. Facing this demand by traditional technologies implies evident risks related with the high cost of fossil fuels and their environmental impact. Then, alternative solutions based on the use of renewable sources and innovative technologies must be considered. In this paper a renewable polygeneration system is examined, which includes a solar field based on parabolic trough photovoltaic/thermal collectors, a biomass heater, an absorption chiller and a Multiple Effect Distillation desalination unit. Plant operation under dynamic conditions has been analysed in previous papers; in this paper an exergetic and exergoeconomic analysis is carried out. The exergetic analysis is intended to identify the steps that mostly affect the overall plant exergy efficiency, so as to propose possible improvements. The exergoeconomic cost accounting is aimed at assigning a monetary value to each energy or material flow, thus providing a rational basis for price assignment. Both the exergetic and exergoeconomic analyses are applied to integral values of energy flows, comparing the results obtained in the summer and winter season. Finally, economic viability of the system in different context scenarios is discussed. [ABSTRACT FROM AUTHOR]

The complicated interrelationship between water and energy makes the water-energy dilemma a complex challenge to be tackled, especially considering the tradeoffs among decision-makers at different hierarchical levels and multiple uncertainties derived from climate change, socio-economic development, technical improvement and decision-making preferences. Thus, a water-energy nexus planning framework would be established in this paper to assist optimal decision-making with bi-level programming and multi-uncertainty. By integrating the regional climate model, multiple linear regression, and bi-level interval flexible programming, an integrated prediction optimization model would be developed as the core of the water-energy nexus planning framework. Then it is applied to planning Zhengzhou City over fifteen years. Multiple scenarios based on electricity demand-supply and carbon dioxide emission satisfaction degrees are analyzed leading to the results of (1) compared to the conventional single-level optimization method, the developed model can achieve the hierarchical goals of water saving and economic suitability; (2) renewable energy will be largely developed and its ratio to electricity generation will reach [26.30, 27.51] % under the limited water availability. Overall, the proposed water-energy nexus planning framework can achieve a balanced water-energy dilemma considering bi-level decision-making preferences and multi-uncertainties, which can be applied to planning water-energy nexus systems at a similar scale. • Regional climate model is used for predicting future electricity demands. • The proposed model addresses bi-level and multi-uncertainty. • Water-energy dilemma towards two different hierarchical levels is assessed. • Optimal solutions provide insights for managing similar scale studies. [ABSTRACT FROM AUTHOR]

District heating system (DHS) is a major part of urban energy system. DHS consists of primary and secondary loop. Compared to the primary loop, the secondary loop is closer to the heating user side. The operation control of heating substation and its corresponding secondary loop is a challenging topic. At present, the existing control of secondary loop is a manual and intermittent regulation process of its water supply temperature regardless of the weather condition, leading to either overheating or insufficient heating on the user side. Intelligent operation control of secondary loop has become a major focus of DHS digitalization. This paper proposes a new method of secondary loop operation control via a data-driven approach by dividing the process into two parts: primary loop valve opening (PLVO) prediction and corresponding secondary loop supply temperature (SLST) prediction. The goal is to provide both a time sequence of enhanced valve opening and its expected supply water temperature. Both models are trained with multilayer perceptron (MLP) and extreme gradient boosting (XGBoost) methods with consideration of the impact of input and prediction length. A demo heating substation and its secondary loop in Zhengzhou city are selected to illustrate the effectiveness of this approach. The application results show that the enhanced PLVO strategy proposed in this paper could reduce the supply water temperature deviation from the expected SLST and adapt to the change of ambient conditions. Compared with the existing operation strategy, the proposed approach reduces the supply water temperature deviation from 12.68% to 3.18% in an overheating scenario and from 6.18% to 3.87% in an insufficient heating scenario. It indicates that the proposed PLVO strategy could overcome the issue of overheating and insufficient heating in existing DHS. The results from this study could provide a basis for flexible and energy-saving operation of decentralized heating systems demanding a delicate and dynamic control of its secondary loop. • Secondary loop operation control is critical to district heating systems. • We propose a data-driven approach to control secondary loop supply temperature. • This new control strategy reduces overheating and avoids insufficient heating. [ABSTRACT FROM AUTHOR]

This paper uses the energy hub concept to meet the electricity, heat and water demand of a cement plant. Given the cement plant's high potential for waste heat recovery so the use of recycled waste heat was compared to a state where such waste heat was not used by taking exergy, economic and environmental analyzes into account. The proposed energy hub consists of electricity, heat and desalinated water production equipment. Energy hub is optimized based on the Genetic Algorithm (GA) with the goal of supplying demand, as well as reducing costs and pollutants and increasing the exergy efficiency which ultimately will be selected using the concept of an energy hub at its optimal capacity. By comparing the two energy supplying systems of the current case study and optimal energy hub, results showed that the Total Annual Cost (TAC) level decreased by about 37,000 $/year and exergy efficiency increased by 36%. CO 2 emission will also decrease by about 21,620 tons/year. Moreover, in the energy hub concept, the waste heat recovery and ignoring waste heat scenarios were compared. Results indicate that upon optimization, the average of TAC when waste heat is recovered, is 27% of the condition when waste heat is ignored. • Proposing of the modified energy hub model to analyze economic and environmental performance. • Finding the optimum range of variables based on TAC and exergy efficiency. • Water is incorporated as an energy stream by simultaneously utilizing MED and RO. • The results of optimization are compared to the conventional mode. [ABSTRACT FROM AUTHOR]

Abstract Renewable energy systems (RES) play a key role in sustainable energy supply systems. Due to the volatile nature of RES, storage capacities and demand shifting strategies must be implemented. In remote areas like islands, the water supply sector mainly consisting of desalination plants and wells has a significant impact on the energy system. The objective of this paper is the evaluation of the demand shifting potential within this sector with respect to its robustness against probabilistic influencing variables. Mixed-integer linear programming is used to simulate the optimised dispatch. Compared to the total annual electricity demand of the island, the study shows that up to 2.1% (1.5 GWh) positive and 5.0% (3.6 GWh) negative demand shifting potential can be assumed if only existing plants are used. Utilisation of micro pumped hydro storage can increase these potentials to 5.5% (4.2 GWh) in positive and 10.3% (7.9 GWh) in negative direction. Furthermore, probabilistic solar radiation has no significant influence on the DR potential while for wind power a saturation of the DR potential for higher degrees of self-sufficiency can be found. Nevertheless, the absolute highest degrees of self-sufficiency come along with the utilisation of both photovoltaic (PV) and wind. Highlights • Demand shifting potential through coupling electricity and water supply sector is shown. • A simulation method is presented to allow robust assessment of energy systems. • Probabilistic weather data are used to quantify expected mean and deviation. • Potential can be enlarged by implementation of micro pumped hydro storages using existing infrastructure and pump- as -turbine. • Up to 10% of the total islands electricity demand can be made flexible. [ABSTRACT FROM AUTHOR]

Abstract Solar aided (coal-fired) power generation (SAPG) technology has been approved to be an efficient way to use solar energy for power generation. However, most solar-rich areas are often short of cooling water supply, especially in China. The air-cooled condenser could alleviate this issue effectively for power plants in these areas. In this paper, a solar aided power generation with direct air-cool condenser (SAPG + ACC) plant is studied and optimized to maximize its performance. Due to the addition of solar heat in an SAPG plant, the exhaust steam flow rate leaving the turbine changes, especially in power-boost mode, which affects the turbine exit pressure and deviates the condenser from its designed operating condition. To achieve maximum net power output, the correlation among the optimum (turbine) exit pressure (OEP), the solar heat input and the ambient temperature, is obtained in this study. The annual plant's performances with four proposed operating strategies of the air-cooled condenser are compared and analyzed. The results show that for an SAPG + ACC plant, the operating Strategy.3, i.e. operated with the hourly OEP is the optimal one, resulting the plant has annual solar-to-electricity efficiency (SEE) of 17.82% and its levelized cost of electricity (LCOE) is of 0.09 $/kWh. Highlights • The impacts of the solar input on turbine exit pressure are revealed. • The optimal (turbine) exit pressure value under a certain condition is obtained. • Four proposed operating strategies of the air-cooled condenser are analyzed. • A sample daily operation procedure to demonstrate the operation is shown. [ABSTRACT FROM AUTHOR]

Abstract Chinese district heating systems are transforming to clean heating systems. The excess heat in CHP and industrial plants are expected to play a dominant role in the transformation considering their enormous heating potential. As excess heat sources usually locate distant from heat demand center, efficient transportation technologies are required. In this paper, combine heat and water (CHW) system was proposed for long-distance heat transportation, using water in water supply system as heat carrier. The CHW system gives heat a free ride to urban area, no needing return water pipeline; thus, it can sharply reduce the costs of transportation. According to investigation, the application prospect of CHW was found in Northern China. A CHW system scheme combing seawater desalination system and excess heat heating system was introduced. Furthermore, through a case study in Xiongan new area, the energy efficiency and economic cost were analyzed. The proposed CHW system can provide 1500 MW heating capacity and 100 million m3 annual water supply quantity. The efficiency of heating with the CHW system is equivalent to a heat pump with COP at 6.74, even the transportation distance is over 200 km. The CHW system has significant advantages in long-distance heat transportation. Highlights • Combined heat and water (CHW) system was proposed for long-distance heat transportation. • The CHW system has application prospect in Northern China. • A scheme was designed combining seawater desalination and excess heat heating systems. • The CHW system has significant energy and economic advantages. [ABSTRACT FROM AUTHOR]

Over the past decades, the penetration of renewable energies has been increasing in many countries. Due to the natural intermittency of renewable energy sources, finding the optimal capacity and location of these energy resources is the most important issue in smart sustainable cities. In this regard, a mathematical strategy is proposed in this paper to find the optimal capacity and location of wind turbines and photovoltaic panels to minimize the total operation cost of a water and energy nexus. In addition, to increase the system efficiency and maximize the benefit of renewable energy sources, water desalination units have been implemented in the proposed methodology, and both electric and water networks are optimized together. In order to present a comprehensive model, the technical, environmental, and economic aspects of the problem are taken into account as a mixed-integer linear programming, where, a machine learning approach based on long-short term memory networks has been utilized for uncertainty modeling of the stochastic parameters including wind and solar generation power, electricity load demand, water demand, and electricity price. Finally, to evaluate the efficiency of the proposed method three different scenarios on a water and energy nexus have been studied considering Kuwait data. The numerical results show that by optimal planning of renewable energy sources, the total cost has decreased about $11950 that is verified the effectiveness of the proposed method. • Water and electricity nexus is considered with modeling optimal operation of units. • A techno-economic-environmental effect of different sources has been investigated. • A machine learning based method is proposed for uncertainty modeling. • An optimization framework is proposed to guarantee the global optimum results. [ABSTRACT FROM AUTHOR]

Conventionally, cooling water system is optimized within a single plant. In reality, a set of cooling towers supply water for multiple plants. This paper presents an optimization model for multi-plants cooling water system. Instead of using a set of uniform pumps to transport cooling water, this work proposed a novel multi-loops pump network and an updated main-auxiliary pump network to reduce pumping energy. Distance factors and pipeline layouts are considered owing to the long distance between plants and pump station. Connecting patterns of different pump networks are investigated and corresponding piping costs are treated as optimized variables. Cooler and pump networks, cooling tower and pipeline layouts are optimized simultaneously. The model is formulated as a mixed-integer nonlinear programming (MINLP) problem. The objective is to obtain the cooling water system with minimized total annual cost. Two case studies are used to illustrate the effectiveness of the proposed structure. [ABSTRACT FROM AUTHOR]

Water supply is of vital importance for urban development, so the overall pressure in urban fresh water pipeline is usually very high to ensure consistent water supply throughout the urban area. Currently, pressure reducing valves (PRVs) are widely used to reduce water pressure in the water supply system (WSS) of high rise buildings to avoid water leakage and other danger in Hong Kong. The application of pump as turbine (PAT) appears as an ideal way for water head reduction as well as hydropower generation in water pipelines. In the present paper, the feasibility and performance of PAT used in WSS for electricity generation was investigated. In the research process, a PAT was first selected by empirical equations based on the given working conditions in one typical high rise building. After selection, CFD simulation and laboratory tests were carried out to study the performance of the selected PAT. Both the simulated and measured results show that the selected PAT is feasible for power generation and water head reduction. The comparison between numerical and experimental results indicate that the simulation outcomes could be used for performance prediction of PAT although the deviation exists. A PAT installation and control strategy was designed and tested in the hydraulic test rig, and the results show that the proposed PAT installation and control strategy performed well for avoiding excessive water head reduction at higher flow rates. [ABSTRACT FROM AUTHOR]

During last years, absorption heat transformers have been used widely for boosting low-grade heat sources. In this paper, a novel multi-generation system including an open absorption heat transformer (OAHT), an organic Rankine cycle with Internal Heat Exchanger (ORC-IHE) and an electrolyzer for hydrogen production is proposed and analyzed from both first and second laws of thermodynamics and exergoenvironmental analysis points of view. To assess the cycle's performance, thermodynamic models were developed and a parametric study was carried out. The results indicate that the net power output and the hydrogen production rate will increase by boosting the inlet temperature of the waste heat using OAHT. By the growth of evaporator temperature, exergoenvironmental impact index, exergetic stability factor and exergetic sustainability index is increasing which is advantageous for the environment. [ABSTRACT FROM AUTHOR]

The level of complexity for a district heating network increases with the maturity of the network, and this affects the pattern of the distribution of the hot water from the heat production sites to the end users. The majority of district heating systems are also multi-source networks, typically supported with heat from one main production site and other smaller satellite sites that are activated when required. In general, local energy companies have a lack of knowledge regarding how a meshed network behaves when different production sites are operated. The schedule of heat generation at the different sites is often based on staff experience and some general rules of thumb. In this paper a method for modeling and simulating complex district networks is further developed in order to optimize the total operating costs of a multi-source network, with constraints on the pressure and temperature levels in the user areas and on the heat generation characteristics at each production site. The optimization results show that the usage of the cheapest resources is preferred to a distributed generation of heat, even if some of the pipes may exceed the recommended thermal load capacity. The main site water supply temperature is found to be the lowest allowed by the constraint on the temperature of the water supplied to the end users, since the decrease of the costs associated with the lower thermal losses in the network is not counterbalanced by the increase of those associated with the pumping power of a larger water mass flow rate. [ABSTRACT FROM AUTHOR]

Discriminant coefficient method (DCM) is a traditional method in guiding the cascade reservoirs joint operation, but it cannot be well used directly in the practical application. This paper combined DCM with the cascade reservoirs energy storage operation chart (CRESOC) and proposed a new DCM based drawing model. In addition, three key technologies in the drawing process and one key technology in the practical application were studied emphatically, which can realize the combined utilization of DCM and CRESOC perfectly. In the case study, we took the cascade reservoirs of Li Xianjiang River in southwest China as an instance to study the CRESOC by the proposed drawing model. Compared with the existing single reservoir operation charts, the simulation results show that the CRESOC presents better performance in terms of power generation and assurance rate, especially on the latter, which has a growth of 6.8%. Moreover, in order to eliminate the insufficient of DCM in practical application, the boundary control curves of each reservoir for water storage and water supply were optimized by the proposed optimization technique, and the simulation results show that there is no water abandonment in all the 43 dry seasons after the optimization. [ABSTRACT FROM AUTHOR]

With the increasing emphasis on clean energy, there is growing attention to the use of microturbines or pumps as turbines (PATs) to recover excess hydraulic energy in the water supply system (WSS) of high-rise buildings. In this paper, a micro Francis turbine for WSS in high-rise buildings was presented, and the effects of runner geometric parameters on turbine performance were investigated through computational fluid dynamics (CFD) and lab tests. In the research process, based on the theoretical design results and the numerical optimization of blade exit angle and blade shape, a turbine model was obtained for laboratory testing. The test results show that the Francis turbine has a relatively good performance in both energy generation and water head reduction. In addition, the feasibility of the used runner design method was verified in this special working condition by comparing the experimental performance of turbines with different runner inlet widths. Based on a numerical model that has been validated by experimental results, further optimization for blade thickness and blade number was carried out through CFD simulations. The simulation results show that blade thickness and blade number can affect energy consumption and pressure distribution in the runner and thus affect turbine performance, and there are optimal values to achieve optimal turbine performance. And the optimized model had an output power of 148 W and an efficiency of 21.23% at the design condition. • Effects of blade outlet angle on turbine performance were investigated. • Effects of blade shape on turbine performance were studied. • The feasibility of the designed Francis turbine in the water supply system of high-rise buildings is analyzed. • Effects of blade thickness on turbine performance were investigated. • Effects of blade number on turbine performance were studied. [ABSTRACT FROM AUTHOR]

In the water distribution network (WDN), there could be considerable potential for power production due to water pressure surplus and head difference inside the water pipes. In WDNs, excess pressure energy inside water pipelines is usually dissipated by pressure reduction valves (PRVs), which can be harnessed by the installation of micro-hydropower (MHP) systems without interfering in the water supply process. MHP systems can be substituted with conventional PRVs for both pressure reduction and energy production. This paper develops a modeling framework to demonstrate the feasibility of using unexploited energy in WDN, adjusted by PRVs, and its potential application in empowering water pumps. In this regard, a case study, considering information of a regional WDN in Teheran city, is designed and modeled in EPANET to estimate the output power from PRVs and to propose plausible options for implementing MHP technologies based on hydraulic model calculations. The results showed that for the studied city network the potential power generated by the extraction of excess energy in RPVs is 168.21 kW, which can provide on average 42.3% of the power consumed by the pumps used in the network. • Energy recovery from replacing PRVs with MHPs in the WDN. • The model of the network is designed by EPANET to estimate the power based on the hydraulic model calculations. • Investigating the effects of hydraulic parameters such as flow and pressure fluctuations in the generated power. [ABSTRACT FROM AUTHOR]

The centrifugal pump is one of the most widely used types of power machinery in the water resource utilization and chemical industries. Its energy consumption cost accounts for a large proportion of its total economic cost. In this paper, an energy consumption improvement method for centrifugal pump is proposed by referring to the bionic structure to reduce the energy loss of the centrifugal pump. Four types of impellers with different types of sinusoidal tubercle trailing edges (STTE) are designed. Experiment and numerical simulation are combined to explore the beneficial effects of STTEs. Experimental research shows that this structural change will not affect the performance of the pump. On this basis, the entropy generation rate analysis method was introduced, and the numerical calculation results were analyzed to explore the internal influence of the STTE on the energy loss characteristics of the centrifugal pump. Results show that the use of STTEs can adjust the proportion of energy loss of each component in a centrifugal pump and effectively reduce the overall energy loss. Quantitative research indicated that the STTE3 has the optimal effect of reducing energy consumption. The use of STTE3 can reduce the total energy consumption by more than 5% at all flow rate conditions and reach a peak of 16.95% under 1.2 times nominal flow rate conditions. Thus, the bionic structure optimization method to improve the internal energy loss characteristics of centrifugal pumps will be beneficial and can provide a certain degree of reference for the hydraulic design of centrifugal pumps. [Display omitted] • An energy consumption improvement method based on bionic design is proposed. • Impellers with different sinusoidal tubercle trailing edges are designed. • Entropy production theory is introduced as the evaluation index. • The STTE is expected to reduce energy consumption by more than 10%. [ABSTRACT FROM AUTHOR]

This paper describes the integration of the pico turbines in the drinking water network of the city of Las Palmas de Gran Canaria (Spain). World's drinking water supply companies need updates his infrastructure and technology to turn existing networks into smart water networks, to preserve people's health by ensuring the potability of water for human consumption. The essential parameters for water quality (such as chlorine level, pH, turbidity and others) can be easily measured using sensors inserted in the pipes and in the storage and distribution tanks. Access to this information in real time and immediate action is essential to ensure the health of the people who access this vital element. It is therefore essential to increase the number of sensors and the analysis of the data they provide in order to detect anomalies, correct them and anticipate their consequences. Some of the objectives are the correct measurement of meters to detect leaks and anomalous consumption, saving water and energy, avoiding water and air pollution, achieving efficient supply to the consumer and achieving profitable, efficient and environmentally sustainable urban hydraulic systems. All systems require power, the pico turbines inserted in the network can supply power without affecting the normal operation of the network. Pico turbines are highly efficient, low cost and easy to install systems, but they are not widely used. The case exposed in this city could be replicated in many urban systems, it is novel that there is no literature of massive applications, existing a wide capacity of implantation and development of this technology. When it seems that the locations for the installation of hydroelectric plants have been exhausted, it is time to commit to the development of this mature technology on the micro-scale of the infrastructures already created, the novelty is to continue discovering those places where there is untapped energy potential. There is capacity to grow in very small hydroelectric systems with immediate profitability. The researchers in this article describe the first phase of an investigation that has gone hand in hand with its validation and actual exploitation. The aim is for managers not to forget this technology, which has a very wide growth field to satisfy the small demand for distributed energy in water networks of all types. The authors hope that the results of the research carried out will motivate other technicians to apply the energy potential of their water networks for the self-sufficiency of their control, remote control, chemical dosage and water analysis systems. The applications they carry out will be immediately profitable. [Display omitted] • Pico turbines allow the self-sufficiency of many points of control of the Drinking Water Network. • It is possible to use pico turbines to reduce the energy consumption of many installations. • Network operator dissipates excess energy to prevent damage. Now is proposed how use that energy. • The pico turbines technology is more than mature, but not sufficiently disclosed. • This technology is cheap, very profitable and reduces CO 2 emissions. [ABSTRACT FROM AUTHOR]

The operation and economic profitability of modern energy systems is constrained by the availability of renewable energy and water resources. Lower water availability due to climate change, higher demand and increased water consumption for non-energy and energy needs may cause problems in Africa. In most African power systems, hydropower is a dominant renewable energy resource, and interconnection capacities are usually limited or unreliable. This paper describes a new modelling framework for analysing the water-energy nexus in the African Power Pools. This framework includes soft linking between two models: the LISFLOOD model is used to generate hydrological inputs and the Dispa-SET model is used for mid-term hydrothermal coordination and optimal unit commitment and power dispatch over the whole African continent. The results show a good agreement between the model outputs and the historical values, despite data-related limitations. Furthermore, the simulations provide hourly time series of electricity generation at the plant level in a robust way. It appears that some African power pools heavily rely on the availability of freshwater resources, while others are less dependent. In the long term, the dependence of the power system on water resources is likely to increase to meet the increasing electricity demand in Africa. • Robust and highly detailed analysis of water-energy nexus in African power pools. • Open source soft-linking framework between LISFLOOD and Dispa-SET models. • First open-source unit commitment and power dispatch model of African power pools. • A compilation of diverse data sources used for the integrated water-energy modelling. • Examination of current and future electricity situation and potential of power trade. [ABSTRACT FROM AUTHOR]

One of the major concerns in developing high-head water resources, which usually uses Pelton turbines especially in geologically young and fragile mountains, is hydro-abrasive erosion caused by the entrained sediment particles. However, the fundamental analysis of the air-water-sediment flow in Pelton turbines remains largely unexplored. Here, a new Eulerian-Lagrangian (E-L) approach is proposed and applied firstly to simulate the transient air-water-sediment flow in Pelton buckets. An analytical model and a qualitative comparison with the field values were adopted to support the reliability of the proposed approach. Further, a detailed analysis of the instantaneous flow patterns and the particle distributions was conducted for this transient three-phase flow. Interestingly, the findings related to the separation behavior of particles from the fluid streamlines revealed that the particles preferentially accumulated at some regions in the water sheet of the buckets as the separation velocity was different in different regions. The particle separation velocity, however, strongly depends on the bucket curvature, particle positions, and velocity of the water sheet. The present paper demonstrated the ability of the E-L approach to satisfactorily simulate the three-phase flow as well as established the E-L approach as a promising tool for erosion prediction in Pelton buckets. • A Eulerian-Lagrangian approach was developed to simulate the transient sediment-laden flow. • An algorithm was proposed to process collisions between particles and rotating surfaces. • Three zones identified for Pelton turbine buckets based on particle distribution characteristics. • Particle separations for different locations in the buckets were analyzed. [ABSTRACT FROM AUTHOR]

Solving the problem of continuous and stable power supply for the water leakage monitoring equipment is challenging in water supply system. Due to the excess water pressure existing in the water supply pipes, the hydropower inside the pipes becomes an effective renewable energy for supplying power to water leakage monitoring equipment. In this paper, a vertical drag-type runner is integrated into the ball valve to harvest the potential hydropower while regulating the fluid. Numerical investigation of the novel ball valve (referred to as GreenValve) is carried out using the software FLUENT. According to different performance requirements, the best working parameters at the average flow rate of 15.7 × 10−3 m3/s are obtained: when working at the optimal tip speed ratio, the GreenValve performs best within the relative opening range of 25%–39%, in which it can harvest considerable energy (>80 W) with the highest efficiency (>11.5%) while the water head loss is only 4–12 m. For the water supply system, the water head loss due to the impact of energy harvesting by the GreenValve can be used to offset the excess pressure in pipes which can easily cause leakage of the pipe network system. • A novel control valve integrated with runner is investigated to harvest energy while regulating the fluid. • The new valve can not only continuously supply power for the fluid transportation system, but also reduce the leakage. • The performances of three different structures are compared and analyzed. • The spool of the new structure can improve the performance of energy harvesting. • The GreenValve can achieve its shaft power of more than 80 W at the flow rate of 15.7 × 10−3 m3/s. [ABSTRACT FROM AUTHOR]

Solar desalination offers a sustainable solution to growing global water demand due to the geographical coincidence between high solar availability and severe water scarcity. This paper presents a self-sustainable solar desalination system combining a spray-assisted low-temperature desalination system, solar thermal collectors, and heat storage tanks. A mathematical model is firstly developed and validated with laboratory pilot for the proposed large-scale solar-powered desalination system. Afterward, the long-term productivity and energy efficiency of the system is evaluated under the climatic conditions of Makkah, Saudi Arabia. The proposed solar desalination system is able to provide an uninterrupted water supply of 20 kg/day for per square meter solar collector area, and the value can be further increased by optimizing the interactions of the three subsystems, i.e. efficiency of the solar collectors, temperature and heat losses in the storage tank, and energy efficiency of the desalination system. With a collector area of 360 m2, the annual productivity is maximized when the feed flowrate is 1.7 kg/s and the diameter of the heat storage tank is 1.9 m. The desalination cost is estimated to be $1.29/m3, which is much lower than other solar thermal desalination systems. • A solar-driven low-temperature desalination system has been evaluated. • Long-term desalination performance has been predicted using dynamic meteorological data. • The optimal design and operational parameters have been obtained. • The proposed solar desalination is cost-effective compared with other solar desalination processes. [ABSTRACT FROM AUTHOR]

This paper presents a new modeling approach to incorporate operational characteristics of different types of hydropower in long-term power sector models. The existing literature and methods were reviewed, and the mathematical formulation of the developed model is presented. The model is then used to analyze the future power generation mix of Nepal, a country with huge untapped hydro resources, as a case study. The possible power sector development pathway has been assessed through three different electricity demand growth rate scenarios. The optimal deployment of indigenous hydro and renewables is further evaluated by developing zero-emission scenarios as a conceivable policy to strengthen national energy security. The sensitivity analysis of governing parameters and evaluation of simulation results was performed to validate the model. Simulation results for capacity and generation mix along with emission level and total power system costs have been discussed for each scenario. Power dispatch and operation schedule determined as a result of optimization take account of the seasonal variations of river inflow and operational benefits of hydropower. Sensitivity analysis is carried out to examine the impact of construction cost, availability factor and water storage capacity on total cost, capacity requirements and optimal operation of hydropower. • Represented different types of hydropower in dynamic power sector model. • Detailed analysis of the future power generation mix of Nepal. • Optimized the operation schedule and water storage strategy of hydro Pondage run-of-the-river and hydro storage. [ABSTRACT FROM AUTHOR]

This paper explores the potential for using large-scale heat pumps (HPs) to extract energy from Copenhagen's drinking water network and deliver it to its district heating system. The system involves certain losses in terms of additional heat and power consumption for end-use water heating. The net potential for energy extraction was analysed by means of an EPANET model to simulate system-wide temperatures in a piped distribution network. The model was validated against measured data from the network. Heat transfer in service lines was computed analytically and included in the net potential for energy extraction, which was determined to be 21 MW in Copenhagen. Around 38% of the HP source demand was harnessed from the ground. With HP COPs between 2.8 and 3.2, the System COP was only 1.7, thus suggesting that the choice of drinking water as a low-temperature heat source should depend on the available alternatives. Drinking water HPs have the side-benefit of preventing high drinking water temperatures; if operated in the summer they increased the share of supplied water complying with a recommended upper temperature limit of 12 °C from 42% to 81%. • A heat transfer model for water supply networks was validated against measured data. • The undisturbed soil temperature is key to predicting heat transfer correctly. • The potential for drinking water heat pumps in Copenhagen was around 36 MW. • Around 38% of the heat pump source demand is reaped from the ground. • Due to increased end-use energy demand, the system COP was reduced by around 42%. [ABSTRACT FROM AUTHOR]