Solar Rich and Water Poor: The Case for Solar Desalination in El Paso, Texas

Abstract

Desalination is an increasingly important water source for the sunny, arid city of El Paso, Texas. As the city’s population grows, El Paso Water, the city’s water utility, has had to drill deeper into the Hueco Bolson aquifer, a primary water source for El Paso. This deeper drilling into the Hueco Bolson, however, has yielded progressively more saline water. In response, El Paso Water and administrators from Fort Bliss jointly constructed a reverse osmosis desalination plant to protect the Hueco Bolson’s freshwater supplies and expand the city’s water sources. Reverse osmosis water desalination, however, is an expensive, energy-intensive process currently dependent on carbon-heavy fossil fuels. Solar energy, however, is an abundant, carbon-free energy source that could potentially reduce the energy costs and carbon footprint of the reverse osmosis desalination process. We hypothesize that building a solar microgrid that supplies El Paso’s desalination plant with energy in tandem with the regional grid will reduce the plant’s energy expenditures in the long term compared to solely buying energy from the regional grid. We used the Hybrid Optimization for Multiple Energy Resources (HOMER) model created by the National Renewable Energy Laboratory. The results suggest that a solar microgrid whose modules use one axis tracker could reduce the plant’s energy expenses. Key Words: desalination, solar energy, water resources.

对阳光充足且乾燥的德州城市艾尔帕索而言，咸水澹化逐渐成为重要的水资源。随着该城的人口增长，艾尔帕索水利单位这个该城的水利事业，必须更深地鑽探胡科博尔森地下蓄水层此一艾尔帕索最主要的水资源来源。此般对胡科博尔森进行更深的鑽探，却逐渐导致更多的咸水。为了因应此问题，艾尔帕索水利单位与布里斯堡的行政人员一同建筑了逆渗透的咸水澹化厂，以保护胡科博尔森的乾淨水源供给，并扩张该城的水资源。但逆渗透咸水澹化却是昂贵且高度消耗能源的过程，目前并依赖排放大量碳的石化燃料。太阳能却是充裕且无碳的能源来源，并有潜力降低逆渗透咸水澹化过程的能源耗费与碳足迹。我们假设，在区域电网之后建立为艾尔帕索咸水澹化厂提供能源的太阳能微电网，相较于仅从区域电网购买能源，将会降低该厂长远的能源花费。我们运用国家可再生能源实验室创造的多重能源资源混合优化模型（HOMER）。研究结果显示，组件运用单向轴追踪器的太阳能微电网，能够降低该厂的能源消耗。 关键词：咸水澹化，太阳能，水资源。

La desalinización es una fuente de agua cada día más importante para la ciudad soleada y árida de El Paso, Texas. A medida que la población de la ciudad crece, El Paso Water, la empresa del servicio hídrico, ha tenido que perforar más hondo en el acuífero del Hueco Bolsón, la fuente de abastecimiento primaria de agua para El Paso. Este barrenado a mayor profundidad en el Hueco Bolsón, sin embargo, rinde agua cada vez más salobre. En respuesta, El Paso Water y los administradores de Fort Bliss, en compañía, construyeron una planta desalinizadora por ósmosis inversa para proteger el suministro de agua dulce del Hueco Bolsón y expandir las fuentes hídricas de la ciudad. El agua de desalinización por ósmosis inversa, sin embargo, es un proceso costoso y energéticamente intensivo que actualmente depende de combustibles fósiles, fuertemente cargados de carbono. Sin embargo, la energía solar es una fuente energética abundante y libre de carbono que potencialmente podría reducir los costos de energía y la huella del carbono en el proceso de desalinización por ósmosis inversa. Nuestra hipótesis es que al construir una microcuadrícula solar que abastezca la planta de desalinización de El Paso con la energía en tándem, con la cuadrícula regional, a largo plazo reducirá los gastos de energía de la planta, comparando esto con solamente comprar energía de la cuadrícula regional. Usamos la Optimización Híbrida del modelo para Múltiples Recursos Energéticos (HOMER) creado por el Laboratorio Nacional de Energía Renovable. Los resultados sugieren que una microcuadrícula solar cuyos módulos usen un eje rastreador podría reducir los costos por energía en la planta.

Palabras clave:

• desalinización
• energía solar
• recursos hídricos

Acknowledgments

We sincerely thank Manuel Perez of El Paso Water for providing the KBH plant’s energy data that made our HOMER analysis possible, as well as his insight on the KBH plant’s energy consumption portfolio. We also sincerely thank Art Ruiz of El Paso Water for providing his insight into the KBH plant’s operations and plans for the future. We thank the anonymous reviewer for providing helpful comments and suggestions. We also thank Dr. Bill Hargrove of the University of Texas at El Paso for connecting us with the personnel at El Paso Water and Dr. David Eaton of the University of Texas at Austin for his useful feedback on our research approaches.

Notes

Notes

1 We selected twenty-five years as the comparison timeline because the typical useful life of PV solar modules is twenty-five years (Rodriguez and Amaratunga 2008; Pingel et al. 2009).

2 Art Ruiz, the KBH plant superintendent, stated that the plant currently receives all of its electricity from the regional grid (personal communication 4 August 2016).

3 This is the city of El Paso’s water utility and administrator of the KBH plant (El Paso Water 2018b).

4 The University of Texas Institutional Review Board (personal communication 2 June 2016) determined that this research did not require their oversight.

5 These data were graciously provided by Manuel Perez, El Paso Water’s Energy Management Coordinator; they show the amount of energy the plant consumed and the price paid for that energy (personal communication 3 February 2017).

6 Single-axis trackers adjust to the sun’s position on either a horizontal plane or a vertical one; dual-axis trackers maintain a perpendicular position relative to the sun throughout the day (Argeseanu, Ritchie, and Leban 2010).

Additional information

Funding

Our research was supported in part by the Robert E. Veselka Endowed Fellowship for Graduate Research Travel from the University of Texas at Austin Department of Geography and the Environment, the E. D. Farmer International Fellowship of the University of Texas at Austin Teresa Lozano Long Institute of Latin American Studies Mexican Center, and the University of Texas at Austin College of Liberal Arts Thematic Diversity Recruitment Fellowship. Our research was also partially made possible by the C. B. Smith Sr. Centennial Chair in U.S.–Mexico Relations of the University of Texas at Austin.

Notes on contributors

William Delgado

WILLIAM DELGADO is a PhD student in the Department of Geography and the Environment at the University of Texas at Austin, Austin, TX 78712. E-mail: [email protected]. His research interests include economic and policy issues surrounding the energy–water nexus in arid, transboundary regions of the world. His regions of interest include the U.S.–Mexico border region and the Middle East.

Timothy Beach

TIMOTHY BEACH holds the C. B. Smith Sr. Centennial Chair in the Department of Geography and the Environment at the University of Texas at Austin, Austin, TX 78712. E-mail: [email protected]. He studies long-term environmental change (soils, geomor-phology, and geoarchaeology) in Mesoamerica, the Mediterranean, and worldwide.

Sheryl Luzzadder-Beach

SHERYL LUZZADDER-BEACH is a Professor and C. B. Smith Sr. Fellow in U.S.–Mexico Relations in the Department of Geography and the Environment at the University of Texas at Austin, Austin, TX 78712. E-mail: [email protected]. Her research interests include water resources, groundwater quality, spatial statistics, and Mesoamerica.