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Field Demonstration of a Cost-Optimized Solar Powered Electrodialysis T Reversal Desalination System in Rural India Wei Hea,B,*, Susan Amrosea, Natasha C

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Field Demonstration of a Cost-Optimized Solar Powered Electrodialysis T Reversal Desalination System in Rural India Wei Hea,B,*, Susan Amrosea, Natasha C Desalination 476 (2020) 114217 Contents lists available at ScienceDirect Desalination journal homepage: www.elsevier.com/locate/desal Field demonstration of a cost-optimized solar powered electrodialysis T reversal desalination system in rural India Wei Hea,b,*, Susan Amrosea, Natasha C. Wrighta, Tonio Buonassisia, Ian M. Petersa, Amos G. Winter Va a Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, United States b School of Engineering, University of Warwick, Coventry, United Kingdom ARTICLE INFO ABSTRACT Keywords: This study provides experimental validation of a previously published optimal design theory for photovoltaic Cost-optimized (PV)-powered electrodialysis reversal (EDR) desalination systems. The prior work describes the co-optimization Electrodialysis reversal of PV and EDR subsystems, and flexible operation to accommodate daily and annual solar irradiance variability, Field-test significantly reducing water cost. This study presents the fabrication of a PV-EDR pilot system designed usingthe Photovoltaic co-optimization theory and field testing results from the rural village of Chelluru, India. Testing inthefield enabled observation and evaluation of real-world factors on system performance, resulting in updates to the previous theory to include unaccounted factors that affect costs, including: filling and draining of water tanks, salt and water accumulation in tanks from prior batches, unexpected energy losses due to locally purchased converters, and scaling in the ED stack. Therefore, water cost in the PV-EDR pilot system was updated from previous estimates based on field performance. The estimated capital cost and lifetime cost of the Chelluru system are 34% and 45% lower, respectively, than the corresponding costs if the PV-EDR system was designed using conventional design practice. The theory and experimental insights presented in this paper will enable desalination engineers to better design and optimize PV-EDR systems. 1. Introduction in either less water produced or oversizing on-grid RO plants to ensure a satisfactory amount of product water, which increases water cost. India is experiencing the worst water crisis in its history [1], with Solar photovoltaic (PV)-powered brackish water desalination has one billion people living under severe water scarcity at least one month recently emerged as an alternative for India due to the challenges of of the year [2]. The Indian government projects that the country's de- grid reliability, the abundance of solar energy, decreasing costs of PV mand for water will be twice the available supply by 2030 [1]. Brackish panels, and an increasing awareness of environmental sustain- groundwater with total dissolved solids (TDS) more than 500 mg/L ability [10]. The performance and economic cost of a PV-powered de- underlies 60% of the land in India [3]. These levels are above the Bu- salination system significantly depend on feed water composition, reau of Indian Standards for Drinking Water recommendation [4]. Al- geographic location, and system capacity. Because of the power sys- most 73% of Indian villages use groundwater as their primary drinking tem's capital cost, off-grid desalination systems cost much more than water source [5]. current on-grid systems; for village-scale RO plants commonly used in Currently, reverse osmosis (RO) is widely used in villages across India, the cost of the PV power system is more than the cost of the RO India to desalinate brackish groundwater, powered primarily by grid system itself [8]. A previous investigation [8] of solar PV-powered electricity [6]. These systems are commercially maintained through the brackish water solutions informed by industry, manufacturers, non- sale of drinking water at 2–3 rupee per 12 L (≈ 2.4–3.6 USD/m3)[7,8]. governmental organizations, government agencies, and end users con- However, rural electrification is incomplete and unreliable. In rural cluded that there are several benefits of electrodialysis (ED) over cur- areas with access to grid electricity, only 7% of households with elec- rently installed RO systems for rural India. Compared to RO, ED has tricity report no power outages, 18% report outages of up to four hours lower energy consumption per unit of water produced (75% less at a day, and 20% experience intermittent power supply throughout most desalinating 1000 mg/L and 30% less at desalinating 3000 mg/L), of the day [9]. The poor quality and intermittence of grid power results greater recovery ratio (nearly double that of current village RO ∗ Corresponding author at: Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, United States E-mail address: [email protected] (W. He). https://doi.org/10.1016/j.desal.2019.114217 Received 12 June 2019; Received in revised form 9 November 2019; Accepted 11 November 2019 0011-9164/ © 2019 Elsevier B.V. All rights reserved. W. He, et al. Desalination 476 (2020) 114217 systems), longer membrane lifetime (2–3 times longer), and lower membrane areas) [16-20], investigating system structure [21,22], and sensitivity to chlorine and feed water changes. These factors could utilizing effective optimization algorithms [23]. Another key to the cost contribute to smaller power system size, less groundwater wastage, reduction in this study by the co-optimization is flexible water pro- lower membrane maintenance and replacement cost, and better duction at the operational level that accommodates daily changes in adaptability with a broader range of feed water salinities, likely to re- solar irradiance, with overproduction on sunny days and water buffer sult in a lower water cost in India. storage tanks for long-term energy storage [15]. These cost minimiza- The technical performance and energy consumption of PV-powered tion strategies of using water tanks as a surrogate energy storage to electrodialysis reversal (PV-EDR) desalination has been investigated maximize solar utilization and minimize battery cost are similar to the previously in lab-scale and pilot-scale systems. Ortiz et al. [11] devel- modeling work on a solar-powered RO system for a relatively similar oped a PV-ED model and validated its ability by prototyping a lab-scale system size [24], and integrated desalination systems with pumped batch EDR brackish water desalination system without battery storage hydro energy storage used in much large system size [25-27]. However, in a lab-scale batch system. Gonzalez et al. recently conducted a lab- none of these prior works provided experimental validation of the re- scale investigation of a PV-ED batch system that desalinated brackish ported performance or costs. water from TDS 5500 mg/L to 300 mg /L with a specific energy con- Therefore, given our past work in [15] was theoretical, the present sumption (SEC) of ED desalination of 5.46 kWh/m3 [12]. In 1987, study aims to make this theory relevant to real-world conditions and Adiga et al. built a pilot-scale 1 m3/day PV-powered continuous ED useful for other desalination researchers and commercial engineers. system in the Thar Desert capable of desalinating 5000 mg/L to Importantly, compared to most prior studies that use simulation tools to 1000 mg/L with an SEC of approximately 4 kWh/m3 [13]. In the same investigate system designs and minimize water cost [16-20,24-27], in year, Kuroda et al. [14] designed and constructed a pilot-scale batch this study we evaluated the real-world effects on the theoretically op- mode PV-ED seawater desalination system in Nagasaki, Japan, produ- timized designs by building and testing a community-scale, 6 m3/day cing 2–5 m3 of drinking water at a TDS of 400 mg/L per day. This PV-EDR experimental prototype in the rural village of Chelluru, India. system was designed to align ED power consumption flexibly to the This study elucidates pain points not captured in prior work, describes power supplied by the solar PV system by splitting its operation into updated co-optimization theory to address them and accurately reflect two modes: 1) a high-power mode to partially desalinate the feed water real-world factors, and presents experimental results that substantiate at mid-day, and 2) a low-power mode to desalinate the partially-desa- the accuracy of the theory as well as the cost savings that can be at- linated water to freshwater in the morning and afternoon. tained through PV-EDR co-optimization. These pilot-scale experiments were conducted over thirty years ago. Over the last three decades, PV power systems have become much more 2. The co-optimization of the PV and EDR subsystems prevalent and their costs have substantially decreased. The market conditions of solar PV and desalination significantly alter the optimal The behavior of the PV and EDR subsystems are coupled re- PV-EDR system required to achieve the highest performance at the ciprocally such that components in each subsystem closely interact with lowest capital and operating cost. In addition, due to solar inter- each other to realize the clean energy to clean water conversion. A PV- mittence and water consumption variations, only a combined under- EDR system design using conventional engineering practice – which standing of PV generation and ED desalination processes will enable the follows a serial process of specifying a daily production volume and creation of a holistic model capable of exploiting synergies between operation time, ED stack size, and power subsystem size – is described solar energy intermittence, drinking water demand
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