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Oahu, Hawaii

A-Index for topography of the island of Oʻahu, Hawaiʻi. Regions for potential IPHRO applications highlighted in white with distance to nearest major city indicated by arrows.

Many coastal regions across the world have severe drought conditions. The World Health Organization says safety and accessibility of drinking water are major concerns. A group of researchers from the University of Hawaiʻi at Mānoa and MIT says that the generation of clean drinking water and related energy cost savings might both be achieved by co-locating hydro energy storage systems with reverse osmosis desalination plants. They call it an integrated pumped hydro reverse osmosis (IPHRO) system.

UH Mānoa mechanical engineering Assistant Professor A. Zachary Trimble is one of the authors of “Integrated Pumped Hydro Reverse Osmosis systems,” an article about IPHRO published in Sustainable Energy Technologies and Assessments. The report includes specific case studies for Southern California, Baja, Hawaiʻi, Chile, Peru and the Middle East. Among the regions highlighted in the article are the islands of Lānaʻi, Maui and Oʻahu. According to the authors, Oʻahu, with a population of almost 1 million, would require an IPHRO system of about one square kilometer and the report also has suggestions about where to locate such a system.

Schematic of potential IPHRO system

IPHRO aids in Hawaiʻi’s clean energy goals

“As we in Hawaiʻi strive to meet our aggressive clean energy goals, we need to invest in large-scale energy storage projects to smooth and condition the inherent intermittency of renewable energy sources,” Trimble said. “Pumped hydro storage is a proven technology that doesn’t come with the challenge of battery disposal each decade. Additionally, particularly here in Oʻahu, fresh water is a precious, and in some of the islands a dwindling, resource. IPHROs utilize a symbiotic relationship between pumped hydro energy storage and reverse osmosis desalination to simultaneously provide two services Hawaiʻi needs: utility scale energy storage and fresh water.”

Renewable energy to power new system

The IPHRO system works in regions with renewable energy sources such as sun and wind, ocean access and mountains with heights greater than 500 meters that are in close proximity to locations with needs for power and water. According to the researchers, an IPHRO could meet the power and freshwater needs for 28 million people in Southern California. They note that creation of such a system would have to be weighed against the effects of drawing down of reservoirs and the need to burn fossil fuels to create electricity for reverse osmosis plants. They suggest further research could examine how much water would be required to support enough flora to reverse desertification and to help create a self-sustaining local climate.

The report also notes that as IPHRO related systems come online, more workers will be needed to maintain and replace these systems. “Indeed an economy based on renewable energy and desalinated water could be critically important for the near and long term future of human civilization in view of rapid climate change.”

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