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19 pages, 627 KiB

Open AccessArticle

The Energy Trade-Offs of Transitioning to a Locally Sourced Water Supply Portfolio in the City of Los Angeles

by Angineh Zohrabian and Kelly T. Sanders

Energies 2020, 13(21), 5589; https://doi.org/10.3390/en13215589 - 26 Oct 2020

Cited by 8 | Viewed by 2688

Predicting the energy needs of future water systems is important for coordinating long-term energy and water management plans, as both systems are interrelated. We use the case study of the Los Angeles City’s Department of Water and Power (LADWP), located in a densely [...] Read more.

Predicting the energy needs of future water systems is important for coordinating long-term energy and water management plans, as both systems are interrelated. We use the case study of the Los Angeles City’s Department of Water and Power (LADWP), located in a densely populated, environmentally progressive, and water-poor region, to highlight the trade-offs and tensions that can occur in balancing priorities related to reliable water supply, energy demand for water and greenhouse gas emissions. The city is on its path to achieving higher fractions of local water supplies through the expansion of conservation, water recycling and stormwater capture to replace supply from imported water. We analyze scenarios to simulate a set of future local water supply adoption pathways under average and dry weather conditions, across business as usual and decarbonized grid scenarios. Our results demonstrate that an aggressive local water supply expansion could impact the geospatial distribution of electricity demand for water services, which could place a greater burden on LADWP’s electricity system over the next two decades, although the total energy consumed for the utility’s water supply might not be significantly changed. A decomposition analysis of the major factors driving electricity demand suggests that in most scenarios, a structural change in LADWP’s portfolio of water supply sources affects the electricity demanded for water more than increases in population or water conservation. Full article

(This article belongs to the Special Issue Energy-Water Nexus)

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15 pages, 2345 KiB

Open AccessArticle

Demand-Response Application in Wastewater Treatment Plants Using Compressed Air Storage System: A Modelling Approach

by Mattia Cottes, Matia Mainardis, Daniele Goi and Patrizia Simeoni

Energies 2020, 13(18), 4780; https://doi.org/10.3390/en13184780 - 14 Sep 2020

Cited by 22 | Viewed by 3213

Abstract

Wastewater treatment plants (WWTPs) are known to be one of the most energy-intensive industrial sectors. In this work, demand response was applied to the biological phase of wastewater treatment to reduce plant electricity cost, considering that the daily peak in flowrate typically coincides [...] Read more.

Wastewater treatment plants (WWTPs) are known to be one of the most energy-intensive industrial sectors. In this work, demand response was applied to the biological phase of wastewater treatment to reduce plant electricity cost, considering that the daily peak in flowrate typically coincides with the maximum electricity price. Compressed air storage system, composed of a compressor and an air storage tank, was proposed to allow energy cost reduction. A multi-objective modelling approach was applied by analyzing different scenarios (with and without anaerobic digestion, AD), considering both plant characteristics (in terms of treated flowrate and influent chemical oxygen demand, COD, concentration) and storage system properties (volume, air pressure), together with the current Italian market economic conditions. The results highlight that air tank volume has a strong positive influence on the obtainable economic savings, with a less significant impact held by air pressure, COD concentration and flowrate. In addition, biogas exploitation from AD led to an improvement in economic indices. The developed model is highly flexible and can be applied to different WWTPs and market conditions. Full article

(This article belongs to the Special Issue Energy-Water Nexus)

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18 pages, 2016 KiB

Open AccessArticle

Membrane Capacitive Deionization for Cooling Water Intake Reduction in Thermal Power Plants: Lab to Pilot Scale Evaluation

by Wim De Schepper, Christophe Vanschepdael, Han Huynh and Joost Helsen

Energies 2020, 13(6), 1305; https://doi.org/10.3390/en13061305 - 11 Mar 2020

Cited by 3 | Viewed by 2841

Abstract

Cooling of thermal power stations requires large amounts of surface water and contributes to the increasing pressure on water resources. Water use efficiency of recirculating cooling towers (CT) is often kept low to prevent scaling. Partial desalination of CT feed water with membrane [...] Read more.

Cooling of thermal power stations requires large amounts of surface water and contributes to the increasing pressure on water resources. Water use efficiency of recirculating cooling towers (CT) is often kept low to prevent scaling. Partial desalination of CT feed water with membrane capacitive deionization (MDCI) can improve water quality but also results in additional water loss. A response surface methodology is presented in which optimal process conditions of the MCDI-CT system are determined in view of water use efficiency and cost. Maximal water use efficiency at minimal cost is found for high adsorption current (2.5 A) and short adsorption time (900 s). Estimated cost for MCDI to realize maximal MCDI-CT water use efficiency is relatively high (2.0–3.1 € m⁻³_evap), which limits applicability to plants facing high intake water costs or water uptake limitations. MCDI-CT pilot tests show that water use efficiency strongly depends on CT operational pH. To allow comparison among pilot test runs, simulation software is used to recalculate CaCO₃ scaling and acid dosage for equal operational pH. Comparison at equal pH shows that MCDI technology allows a clear reduction of CT water consumption (74%–80%) and acid dosage (63%–80%) at pH 8.5. Full article

(This article belongs to the Special Issue Energy-Water Nexus)

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19 pages, 3896 KiB

Open AccessArticle

Evolution of Virtual Water Transfers in China’s Provincial Grids and Its Driving Analysis

by Yiyi Zhang, Shengren Hou, Jiefeng Liu, Hanbo Zheng, Jiaqi Wang and Chaohai Zhang

Energies 2020, 13(2), 328; https://doi.org/10.3390/en13020328 - 09 Jan 2020

Cited by 7 | Viewed by 2147

Abstract

In China, electricity transmission has increased rapidly over the past decades, and a large amount of virtual water is delivered from power generation provinces to load hubs. Understanding the evolution of the virtual water network embodied in electricity transmission is vital for mitigating [...] Read more.

In China, electricity transmission has increased rapidly over the past decades, and a large amount of virtual water is delivered from power generation provinces to load hubs. Understanding the evolution of the virtual water network embodied in electricity transmission is vital for mitigating water scarcity. However, previous studies mainly calculated the virtual water transferred in short periods in low-spatial resolution and failed to reveal driving forces of the evolution of virtual water. To solve this problem, we investigated the historical evolution of the virtual water network and virtual scarce water network embodied in interprovincial electricity transmission between 2005 and 2014. The driving forces of the evolution of virtual (scarce) water networks were analyzed at both national level and provincial level. The results show that the overall virtual water transmission and virtual scarce water transmission increased by five times, and the direction was mainly from southwest and northwest provinces to eastern provinces. Sichuan, Yunnan, and Guizhou played an increasingly important role in virtual water exporting, and northwestern provinces had dominated the virtual scarce water exporting in the decade. At the national level, the increase of virtual water is mainly driven by the change of power generation mix and power transmission. At the provincial level, the increase of virtual water transmission in the largest virtual water exporter (Sichuan) is driven by the power generation mix and the power transmission, between 2005 and 2010, and 2010 and 2014, respectively. Considering the expanding of electricity transmission, the development of hydropower in the southwestern provinces and other renewable energies (solar and wind) in the northeastern provinces would overall mitigate the water scarcity in China. Full article

(This article belongs to the Special Issue Energy-Water Nexus)

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18 pages, 6079 KiB

Open AccessArticle

Experimental Investigation of Copper Mesh Substrate with Selective Wettability to Separate Oil/Water Mixture

by Jia Yuan, Chenyi Cui, Baojin Qi, Jinjia Wei and Mumtaz A. Qaisrani

Energies 2019, 12(23), 4564; https://doi.org/10.3390/en12234564 - 29 Nov 2019

Cited by 3 | Viewed by 2357

Abstract

To solve the problem of low efficiency and poor adaptability during complex oil/water mixtures separation, two types of membranes with superhydrophilicity/underwater-superoleophobicity were successfully fabricated by oxidative reaction and in situ displacement reaction methods. A nanoneedle Cu(OH)₂ structure was generated on the copper [...] Read more.

To solve the problem of low efficiency and poor adaptability during complex oil/water mixtures separation, two types of membranes with superhydrophilicity/underwater-superoleophobicity were successfully fabricated by oxidative reaction and in situ displacement reaction methods. A nanoneedle Cu(OH)₂ structure was generated on the copper mesh substrate by oxidative reaction and feathery micro/nanoscale composite, while Ag structure was constructed at the surface of copper mesh substrate through in-situ replacement, then, membranes with superhydrophilic/underwater-superoleophobic properties were separated. The influence of microstructure, wettability of the surface of prepared membranes and the liquid constituents in the separation experiment were studied and the liquid flux and permeation pressure at the membrane were later experimentally investigated. The experimental results show that separation efficiency of both membranes for separating different oil/water mixtures was above 99.8%. However, the separation efficiency of the Ag-CS (Ag on the copper substrate) membrane was obviously higher than that of the Cu(OH)₂-CS (Cu(OH)₂ on the copper substrate) membrane after 10 instances of separation because of the micro/nanocomposite structures. By comparison, it was found that the Ag-CS membrane showed a relatively higher permeation pressure but lower liquid flux as compared to Cu(OH)₂-CS membrane, due to the influence of microscale structure and the wettability of the surface combined. In addition, the outcome for separating the multicomponent oil/water mixture illustrate that the result of TOC (the Total Organic Carbon) test for the Cu(OH)₂-CS membrane and Ag-CS membrane were 31.2% and 17.7%, respectively, higher than the average of the two oils probably because some oil droplets created due to mutual dissolution passed through the membranes. However, these two fabricated membranes still retained higher separation efficiencies and good adaptability after 10 instances of separation. It was concluded that based on the good performances of the prepared membranes, especially the modified membrane, they have a vast application prospect and can be widely used. Full article

(This article belongs to the Special Issue Energy-Water Nexus)

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12 pages, 2763 KiB

Open AccessArticle

Deformation Effect on Water Transport through Nanotubes

by Ferlin Robinson, Majid Shahbabaei and Daejoong Kim

Energies 2019, 12(23), 4424; https://doi.org/10.3390/en12234424 - 21 Nov 2019

Cited by 8 | Viewed by 2184

Abstract

In this study, we used non-equilibrium molecular dynamics to study the transport of water through deformed (6,6) Carbon Nanotubes (CNTs) and Boron Nitride Nanotubes (BNNTs). The results were then compared with that of the perfect nanotubes. The main aim of this study was [...] Read more.

In this study, we used non-equilibrium molecular dynamics to study the transport of water through deformed (6,6) Carbon Nanotubes (CNTs) and Boron Nitride Nanotubes (BNNTs). The results were then compared with that of the perfect nanotubes. The main aim of this study was to get a better insight into the deformation effect on water transport through nanotubes rather than directly comparing the CNTs and BNNTs. As the diameters of both types of nanotubes differ from each other for the same chiral value, they are not directly comparable. We carried out our study on deformations such as screw distortion, XY-distortion, and Z-distortion. XY-distortion of value 2 shows a change from single-file water transport to near-Fickian diffusion. The XY-distortions of higher value shows a notable negative effect on water transport when their distortion values get larger. These suggest that the degree of deformation plays a crucial role in water transport through deformed nanotubes. The Z-distortion of 2 showed discontinuous single-file chain formation inside the nanotubes. Similar phenomena are observed in both nanotubes, irrespective of their type, while the magnitudes of their effects vary. Full article

(This article belongs to the Special Issue Energy-Water Nexus)

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22 pages, 5525 KiB

Open AccessArticle

Carbon and Water Footprint of Energy Saving Options for the Air Conditioning of Electric Cabins at Industrial Sites

by Maurizio Santin, Damiana Chinese, Onorio Saro, Alessandra De Angelis and Alberto Zugliano

Energies 2019, 12(19), 3627; https://doi.org/10.3390/en12193627 - 23 Sep 2019

Cited by 5 | Viewed by 3064

Abstract

Modern electric and electronic equipment in energy-intensive industries, including electric steelmaking plants, are often housed in outdoor cabins. In a similar manner as data centres, such installations must be air conditioned to remove excess heat and to avoid damage to electric components. Cooling [...] Read more.

Modern electric and electronic equipment in energy-intensive industries, including electric steelmaking plants, are often housed in outdoor cabins. In a similar manner as data centres, such installations must be air conditioned to remove excess heat and to avoid damage to electric components. Cooling systems generally display a water–energy nexus behaviour, mainly depending on associated heat dissipation systems. Hence, it is desirable to identify configurations achieving both water and energy savings for such installations. This paper compares two alternative energy-saving configurations for air conditioning electric cabins at steelmaking sites—that is, an absorption cooling based system exploiting industrial waste heat, and an airside free-cooling-based system—against the traditional configuration. All systems were combined with either dry coolers or cooling towers for heat dissipation. We calculated water and carbon footprint indicators, primary energy demand and economic indicators by building a TRNSYS simulation model of the systems and applying it to 16 worldwide ASHRAE climate zones. In nearly all conditions, waste-heat recovery-based solutions were found to outperform both the baseline and the proposed free-cooling solution regarding energy demand and carbon footprint. When cooling towers were used, free cooling was a better option in terms water footprint in cold climates. Full article

(This article belongs to the Special Issue Energy-Water Nexus)

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20 pages, 826 KiB

Open AccessDiscussion

The Possible Roles of Wastewater Treatment Plants in Sector Coupling

by Michael Schäfer, Oliver Gretzschel and Heidrun Steinmetz

Energies 2020, 13(8), 2088; https://doi.org/10.3390/en13082088 - 22 Apr 2020

Cited by 20 | Viewed by 3487

Abstract

The development of a power system based on high shares of renewable energy sources puts high demands on power grids and the remaining controllable power generation plants, load management and the storage of energy. To reach climate protection goals and a significant reduction [...] Read more.

The development of a power system based on high shares of renewable energy sources puts high demands on power grids and the remaining controllable power generation plants, load management and the storage of energy. To reach climate protection goals and a significant reduction of CO₂, surplus energies from fluctuating renewables have to be used to defossilize not only the power production sector but the mobility, heat and industry sectors as well, which is called sector coupling. In this article, the role of wastewater treatment plants by means of sector coupling is pictured, discussed and evaluated. The results show significant synergies—for example, using electrical surplus energy to produce hydrogen and oxygen with an electrolyzer to use them for long-term storage and enhancing purification processes on the wastewater treatment plant (WWTP). Furthermore, biofuels and storable methane gas can be produced or integrate the WWTP into a local heating network. An interconnection in many fields of different research sectors are given and show that a practical utilization is possible and reasonable for WWTPs to contribute with sustainable energy concepts to defossilization. Full article

(This article belongs to the Special Issue Energy-Water Nexus)

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