# Freshwater & renewable energy storage for drought striken regions? Areas for integrated pumped hydro reverse osmosis (IPHRO) system identified

• Combined energy and water system could provide for millions: Analysis shows system could economically bring fresh water and renewable energy storage to drought-stricken coastal regions worldwide. Introduction by Kelley Travers | MIT Energy Initiative, 18 April 2017.  Full copy of the article is available at the link and below the overview.

The team’s analysis determined that in Southern California, all power and water needs can actually be met for 28 million people. An IPHRO system could be located in the mountains along the California coast or in Tijuana, Mexico, and would additionally provide long-term construction and renewable energy jobs for tens of thousands of people. Findings show that to build this system, the cost would be between $5,000 and$10,000 per person served. This would cover the cost of all elements of the system — including the renewable energy sources, the hydropower system, and the reverse osmosis system — to provide each person with all necessary renewable electric power and fresh water.

MIT students are part of a joint team of American, Israeli, and Jordanian students who worked together to study possible integrated pumped hydro reverse osmosis (IPHRO) system site locations around the world.

An integrated pumped hydro reverse osmosis (IPHRO) system produces both freshwater and electric power from renewable energy sources, such as solar power and wind power, by combining a pumped hydro energy storage system with a reverse osmosis desalination plant

Many highly populated coastal regions around the globe suffer from severe drought conditions. In an effort to deliver fresh water to these regions, while also considering how to produce the water efficiently using clean-energy resources, a team of researchers from MIT and the University of Hawaii has created a detailed analysis of a symbiotic system that combines a pumped hydropower energy storage system and reverse osmosis desalination plant that can meet both of these needs in one large-scale engineering project.

The researchers, who have shared their findings in a paper published in Sustainable Energy Technologies and Assessments, say this kind of combined system could ultimately lead to cost savings, revenues, and job opportunities.

The basic idea to use a hydropower system to also support a reverse osmosis desalination plant was first proposed two decades ago by Professor Masahiro Murakami of Kochi University of Technology, but was never developed in detail.

“Back then, renewables were too expensive and oil was too cheap,” says the paper’s co-author Alexander Slocum, the Pappalardo Professor of Mechanical Engineering at MIT. “There was not the extreme need and sense of urgency that there is now with climate change, increasing populations and waves of refugees fleeing drought and war-torn regions.”

Recognizing the potential of the concept now, Slocum and his co-authors — Maha Haji, Sasan Ghaemsaidi, and Marco Ferrara of MIT; and A Zachary Trimble of the University of Hawaii — developed a detailed engineering, geographic, and economic model to explore the size and costs of the system and enable further analysis to evaluate its feasibility at any given site around the world.

Typically, energy and water systems are considered separately, but combining the two has the potential to increase efficiency and reduce capital costs. Termed an “integrated pumped hydro reverse osmosis (IPHRO) system,” this approach uses a lined reservoir placed in high mountains near a coastal region to store sea water, which is pumped up using excess power from renewable energy sources or nuclear power stations. When energy is needed by the electric grid, water flows downhill to generate hydroelectric power. With a reservoir elevation greater than 500 meters, the pressure is great enough to also supply a reverse osmosis plant, eliminating the need for separate pumps. An additional benefit is that the amount of water typically used to generate power is about 20 times the amount needed for creating fresh water. That means the brine outflow from the reverse osmosis plant can be greatly diluted by the water flowing through the hydroelectric turbines before it discharges back into the ocean, which reduces reverse osmosis outflow system costs.

As part of their research, Slocum’s team developed an algorithm that calculates a location’s distance from the ocean and mountain height to explore areas around the world where IPHRO systems could be installed. Additionally, the team has identified possible IPHRO system locations with potential for providing power and water — based on the U.S. average of generating 50 kilowatt-hours of energy and 500 liters of fresh water per day — to serve 1 million people. In this scenario, a reservoir at 500 meters high would only need to be one square kilometer in size and 30 meters deep.

The team’s analysis determined that in Southern California, all power and water needs can actually be met for 28 million people. An IPHRO system could be located in the mountains along the California coast or in Tijuana, Mexico, and would additionally provide long-term construction and renewable energy jobs for tens of thousands of people. Findings show that to build this system, the cost would be between $5,000 and$10,000 per person served. This would cover the cost of all elements of the system — including the renewable energy sources, the hydropower system, and the reverse osmosis system — to provide each person with all necessary renewable electric power and fresh water.

Working with colleagues in Israel and Jordan under the auspices of the MIT International Science and Technology Initiatives (MISTI) program, the team has studied possible sites in the Middle East in detail, as abundant fresh water and continuous renewable energy could help bring stability to the region. An IPHRO system could potentially form the foundation for stable economic growth, providing local jobs and trade opportunities and, as hypothesized in Slocum’s article, IPHRO systems could possibly help mitigate migration issues as a direct result of these opportunities.

“Considering the cost per refugee in Europe is about 25,000 euros per year and it takes several years for a refugee to be assimilated, an IPHRO system that is built in the Middle East to anchor a new community and trading partner for the European Union might be a very good option for the world to consider,” Slocum says. “If we create a sustainable system that provides clean power, water, and jobs for people, then people will create new opportunities for themselves where they actually want to live, and the world can become a much nicer place.”

This work is available as an open access article on ScienceDirect, thanks to a grant by the S.D. Bechtel Jr. Foundation through the MIT Energy Initiative, which also supported the class from which this material originated. The class has also been partially supported by MISTI and the cooperative agreement between the Masdar Institute of Science and Technology and MIT.

#### Alexander H. Slocuma, , Maha N. Hajia, , A Zachary Trimbleb, , , Marco Ferrarac, , Sasan J. Ghaemsaidia,  https://doi.org/10.1016/j.seta.2016.09.003Get rights and content Under a Creative Commons license

Abstract

Ideal head height for pumped hydro energy storage/generation systems and reverse osmosis desalination plants coincide (500–700 m). Many drought stricken coastal regions have nearby mountains of sufficient elevation to support upper reservoirs at this ideal head height. A good symbiotic match might thus be realized by co-locating a pumped hydro plant with a reverse osmosis desalination plant, which we call an Integrated Pumped Hydro Reverse Osmosis (IPHRO) system. Combining systems reduces capital investment, such as pump costs, and solves the desalination brine disposal challenge since 10–20 times more water is required to generate one person’s power needs than to generate their fresh water needs, so brine outflow can be diluted by the turbine output water reducing costs of diffusing outflow pipes. This paper describes an algorithm that weights distance from the ocean and mountain height to explore where around the world such IPHRO systems might be located. Design equations are presented to preliminarily explore the size and cost of an IPHRO system and enable first order site feasibility assessment. An example is given for providing power and water for one million people with an IPRHO system in southern California. Analysis and consideration of other sites is included in a supplementary document.

• Renewable energy storage;
• Desalination;
• Pumped hydro;
• Drought

#### 1. Introduction

Many coastal regions, such as those in California, have severe drought conditions [1]. Reverse osmosis (RO) desalination plants can be built to generate fresh water, but require electricity from the grid that if generated by fossil fuels may exacerbate climate change and worsen droughts [2]. Meanwhile, drought in the Middle East creates humanitarian crises and is politically destabilizing with dire consequences [3]. Governments in the region are beginning to focus on managing their abundant energy supplies, with an eye towards solar and wind energy, meanwhile they also need to produce fresh water.

Rather than consider energy and water systems separately, cost savings might be obtained by combining systems. For example, combining pumped hydro energy storage (PH) with RO desalination. Furthermore, additional cost savings and revenues can be realized by combining other harvest activities such as offshore wind turbines and aquaculture [4], or energy storage [5], or extracting uranium from seawater [6] ;  [7].

Water management, including desalination, and renewable energy strategies might be best considered together; however large scale use of renewables requires utility-scale electricity storage as a key element [8] ;  [9]. Currently pumped storage hydro accounts for 95% of global grid storage capacity [10], but may incur significant evaporative water losses depending on local temperatures and humidity. Most pumped storage hydro utilizes large lakes, and if a small dedicated deep lake was used that was almost completely cycled every day, evaporation could be minimized with the use of floating cover elements [11]; [12] ;  [13] which are commercially available as hexagonal elements made from recycled plastic (e.g., http://www.awtti.com/hexprotect_cover.php).

For islands, or regions without a strong grid, RO systems can be economically operated by an intermittent renewable energy supply [14] ;  [15]. Large scale energy storage to enable continuous operation would be economically more efficient in terms of capital recovery and reduced membrane costs. This was demonstrated with a system that utilizes wind power combined with flywheels and batteries that enabled an RO system to run continuously in the Canary Islands [16].

Desalination, however, also creates brine. Brine disposal into the ocean is common in many parts of the world with the use of long (and costly) diffusing outflow pipes, but may be a contentious issue in some areas such as Hawaii and the Gulf of Aqab. An alternate strategy would be disposal of the brine by evaporation, with recovery of salt and minerals as a byproduct [17] ;  [18]. In the current proposal we show that if excess renewable power is stored in a high reservoir, the water needed for power generations is >10X more than for freshwater generation, and thus the brine can be combined with the water for power generation so it is automatically diluted, thus saving brine outflow pipe disposal or evaporative pond costs.

Hydropower plants have been in operation for centuries, and pumped hydropower plants have been in operation for decades where an upper reservoir works in conjunction with a lower reservoir to store energy or produce power using a pump/turbine. Many pumped storage hydro facilities have been designed to receive power from nuclear energy systems operating at night so the reactor can run 24/7 at full power thus during peak demand the system essentially provides twice the power that the reactor alone can. Hydropower plants can last for tens of thousands of cycles (essentially decades, and even then can be cost effectively rebuilt). Additionally an important feature of pumped hydro that is often taken for granted is its ability to stabilize a grid and/or to restart a large grid that has suffered a blackout1. Furthermore, like any other energy storage system, pumped hydro plants also enable intermittent renewable energy machines, such as wind turbines and PV solar power panels, to function as baseload power systems.

While there are many freshwater pumped hydro plants in operation, it is often difficult to cite a new plant because of geography, population pressure, and scarcity of fresh water in many locations. The oceans, however, represent an essentially infinite lower reservoir in coastal locations where there are nearby mountains. Only one pumped seawater hydro plant currently exists, a 30 MW unit in Japan, which is supplied with excess power from the grid [19] ;  [20], and it has been successfully operating for many years. An earlier seawater pumped hydro storage was to be built in Egypt [21]. Currently, a 300 MW pumped seawater hydro system powered entirely by solar PV is under tender in Chile, but no significant RO is currently planned [22]. Several alternatives were also proposed in the 1980s which also were to include RO plants coupled to a renewable energy system [23]. The Red Sea Dead Sea project has been around for decades and recently a detailed study showed it was economical to closely couple the desalination system with the pumped storage hydroelectric system where the brine output from the RO system was pumped uphill to a holding lake where it was released through a power turbine when needed with outflow to the dead sea [24]. In the 1990s a combined pumped hydro and RO system was proposed for the Aqaba Jordan region [25] ;  [26] but perhaps not enough detail was available to convince the region at the time that it should develop such a system.

#### 2. Symbiotic approach: co-location of Pumped Hydro and Reverse Osmosis Systems

Pumped storage hydro facilities are typically operated by power companies, distinct from water companies. Given the lack of freshwater in arid coastal locations, it is logical to consider using the ocean as a lower reservoir and pumping seawater to an upper reservoir to store energy. The electricity produced could then be used by a conventional RO plant. There have been studies on the total cost of desalination, capital and operating costs [27] ;  [28] but detailed breakdown of system element costs are difficult to come by. Total capital costs for brackish water are reported on the order of $2/gallon/day to$4/gallon/day [29] to $1.5/gallon/day to$3/gallon/day [30] ;  [31]. The process equipment costs are about 49% of this total [32]. Consensus appears to be that in order to accurately predict costs for a project, a site specific design study must be undertaken [33] ;  [34].

#### 3. Geographic potential assessment

In order to investigate the applicability of IPHROS in various regions, a geographic information system (GIS) based topographic analysis was performed using shuttle radar topography mission (SRTM) digital elevation models (DEM) from NASA [52]; [53]; [54] ;  [55]. First, 3-arc second (∼90 m) was used to determine the locations of regions that had elevations 500 m. Next, the elevation of each location was divided by the distance to the seacoast, resulting in what is referred to here as the “A-Index”. The higher the A-Index, the greater the potential suitability for IPHROS.

The A-Index is a currently a qualitative measure intended to identify geographical regions that can even be considered, those which meet a minimum height requirement and within regionally acceptable tunneling distance from shore, and colorize the region so as to allow for rapid assessment of an area under scrutinization. It would be analogous to forming an A-list of options (the first place to go looking). The A-Index thus serves as an indicator for a region to identify where the reservoir might be placed. The greater the value of the A-Index, the higher the reservoir, or the closer to the shore a region might be, both factors that can increase the value of a project either by providing greater energy storage potential or lower construction costs. It might be possible in the future to create a more quantitative index.

For the United States, more detailed analysis was conducted using higher resolution 1-arc second (30 m) SRTM DEM from NASA. The potential energy per cycle (reservoir filled and then drawn down) of areas with a high A-Index was determined using the formula

equation(1)

EpotrtρswghLdS,

where ηrt = IPHROS round-trip efficiency (based on typical values found for pumped storage hydroelectric systems), ρsw = seawater density, g = gravity, hL = elevation above sea-level, d and S   are the depth and surface area respectively of the IPHROS reservoir. For the following analysis, ηrt is taken to be 80% and d is estimated to be 30 m. If smaller surface areas are desired for the lake deeper depths can be used. The results of the GIS-based analysis for various sites across the globe are presented in this section, additional sites are presented in Supplementary Materials A.

#### 3.1. Southern California

Southern California is very dry with a very large population, and takes water from the Owen’s valley, so if this water was no longer needed, farming in the valley might flourish [56]; [57] ;  [1]. In southern California, the mountains around Malibu and San Clemente have great promise for IPHRO systems as shown in Fig. 5 Figure options Fig. 6Figure options

Based on the resulting qualitative A-Index (good mountain height within tunneling distance from shore) for areas around Malibu and San Clemente, regions highlighted were selected for further analysis (Fig. 5 ;  Fig. 6). These regions have a total upper reservoir (lake) area potential of approximately 14.7 km2. Assuming these are all developed into IPHROS lakes in which 30 m of water is pumped up and down with each cycle, these regions could provide power and freshwater for about 28 million people. A reservoir depth of 30 m is considered reasonable because it is a depth easily reached by divers if any maintenance is needed, although a smaller area or more people served could be realized with greater depth of draw. As shown in Fig. 2 the amount of seawater needed for desalination is only 4.7% of the total pumped to the lake. If the priority is for more freshwater for piping to interior regions, freshwater for 236 million people could readily be provided by diverting about 37% of the flow to the RO system. This was determined using the minimum allowable turbine diversion to the brine outflow, an ambient seawater salinity of Ssw=3.5%, a desired brine outflow salinity of no more than Sht=4% (in keeping with California guidelines and regulations [58]), a seawater density of ρsw=1027 kg/m3, and a freshwater density of ρfw=1000 kg/m3. Details are provided in the Supplementary Materials A. By comparison, the population of Malibu and San Clemente are 12,645 and 63,522 respectively, while the Greater Los Angeles region is 18.55 million [59].

#### 3.2. Baja California

The cities of Ensenada and Tijuana, 84 km to the north, have a combined population of 1.77 million [60]. The mountains around Ensenada are well-suited for an IPHRO system as shown in Fig. 7 ;  Figure options   Fig. 8Figure options

Following a similar analysis to that done for southern California, regions selected for further analysis are highlighted in Fig. 7 ;  Fig. 8 and detailed in Table 1 ;  Table 2 respectively. These regions represent a total lake area of approximately 31.3 km2 and could provide power and freshwater for about 28.8 million people; hence significant water export, perhaps via a pipeline to Southern California, could be realized.

Table 1.Energy potential of IPRHOS in regions surrounding in Southern California.

Region Head (m) Surface area (km2) Distance from coast (km) A-Index Nearest major city (NMC) Distance to NMC Energy potential (GWh/cycle)
USA-CAM-A 612 2.9 5.2 0.112 Malibu 5.9 119
USA-CAM-B 684 2.2 7.7 0.089 Malibu 8.8 101
USA-CAM-C 528 1.7 4.3 0.123 Malibu 3.3 59
USA-CAM-D 678 0.9 6.9 0.098 Malibu 8 42
USA-CAM-E 518 1.3 2.7 0.192 Malibu 8 44
USA-CAM-F 545 2.4 7.2 0.076 Pacific Palisades 7.9 89
USA-CAS-A 505 0.5 4.1 0.123 San Clemente 14 17
USA-CAS-B 552 2.8 13.3 0.042 San Clemente 20 104

Table 2.Energy potential of IPHROS in regions in Baja California, Mexico.

Region Head (m) Surface area (km2) Distance from coast (km) A-Index Nearest major city (NMC) Distance to NMC Energy potential (GWh/cycle)
MEX-ENS-A 886 3.5 15 0.059 Ensenada 9.2 119
MEX-ENS-B 636 2.7 9.6 0.066 Ensenada 7.6 101
MEX-TIJ-A 567 14.5 12.7 0.045 Tijuana 12.8 483
MEX-TIJ-B 542 10.7 8.2 0.066 Tijuana 18.8 388

#### 3.3. Hawaii

The island of Lanai in Hawaii is particularly well suited to an IPHRO system because the population is small but in great need of freshwater and electricity. In addition, single private ownership of most of the island and the desire to develop the island’s resort potential could enable rapid responsible development of an IPHRO system which would then serve as a powerful learning project for the other islands. Fig. 9 depicts the resulting A-Index for the island and highlights regions further detailed in Table 3. From this analysis, it can be seen that the highlighted regions represent a total lake area of approximately 5.8 km2, which, if developed for IPHROS, could provide power and electricity for nearly 5.4 million people. With a population of only 3102 [59], by Fig. 2 only about 3366 m2 of this total lake area must be developed into IPHROS in order to provide the entire island with power and freshwater. However the island of Lanai is also in need of irrigation water for agriculture. Investigation of a hybrid irrigation water and freshwater system are underway.

Fig. 9.  A-Index for topography of the island of Lanai, Hawaii. Regions for potential IPRHOS applications highlighted in white with distance to nearest major city indicated by arrows.

Table 3.Energy potential of IPHROS in regions in Hawaii.

Region Head (m) Surface area (km2) Distance from coast (km) A-Index Nearest major city (NMC) Distance to NMC Energy potential (GWh/cycle)
USA-HIL-A 516 2.3 3.3 0.157 Lanai City 6.6 103
USA-HIL-B 953 1.2 6.0 0.159 Lanai City 5.0 80
USA-HIL-C 552 1.6 2.1 0.268 Lanai City 8.6 59
USA-HIM-A 1300 5.9 7.5 0.173 Kahului 7.6 515
USA-HIM-B 2757 11 11 0.257 Kihei 21 1963
USA-HIO-A 1192 0.65 8.5 0.140 Mililani Town 14 52
USA-HIO-B 650 5.5 4.4 0.148 Honolulu 12 238
USA-HIO-C 714 2.2 7.2 0.099 Honolulu 7.5 106

More populated than Lanai, the island of Maui also faces significant electricity and freshwater demand challenges. The resulting A-Index for the island is shown in Fig. 10 with these areas detailed further in Table 3. The total highlighted regions have a combined lake area of 16.52, which represent power and electricity for 15.2 million people. As in the case of Lanai, the population of Maui is much smaller than the total population potential that could served by all possible IPHROS installations on the island. In fact, to serve the entire population of 144,444 [59], would only require an IPHROS system with a lake area of 0.16 km2. In fact, the existing Auwahi Wind site located on the wind-rich Ulupalakua Ranch on the southeast coast of Maui, is at an elevation with a high A-index. An IPHRO system could thus be added to the wind farm to provide needed energy storage and freshwater for the Hawaiian owned farms in the region which are in great need of freshwater for irrigation.  Fig. 10.  A-Index for topography of the island of Maui, Hawaii. Regions for potential IPRHOS applications highlighted in white with distance to nearest major city indicated by arrows. Figure options

The most populated of the Hawaiian islands, Oahu is faced with even greater electricity and freshwater challenges than Lanai and Maui. The A-Index resulting from geographical analysis of the island are depicted in Fig. 11. Regions highlighted in white were selected for further investigation and the details of the IPHROS viability are listed in Table 3. From this data, there exits approximately 20 km2 that could be developed into IPHROS, providing electricity and power for 18.5 million people. With the population of Oahu about 953,207 [59], only a little over 1 km2 is required to meet the energy and water needs of the resident population.  A-Index for topography of the island of Oahu, Hawaii. Regions for potential IPRHOS applications highlighted in white with distance to nearest major city indicated by arrows. Figure options

#### 3.4. Peru

The region around the city of Lima holds great promise for IPHRO systems. Fig. 12 shows an image of the region and the potential lake area. With a population of nearly 8.5 million people, if all the highlighted regions were developed for IPHROS, they could provide enough power and water for 87 million people. Therefore, only 10% need to be developed to serve the entire population of Lima. Highlighted regions are further detailed in Table 4.

12.  A-Index for topography near Lima, Peru. Regions for potential IPRHOS applications highlighted in white with distance to nearest major city, Lima, indicated by arrows. Figure options

Table 4.Energy potential of IPHROS in regions in Peru.

Region Head (m) Surface area (km2) Distance from coast (km) A-Index Nearest major city (NMC) Distance to NMC Energy potential (GWh/cycle)
PER-LIM-A 592 17 2.9 0.203 Lima 38.5 704
PER-LIM-B 574 16 3.2 0.179 Lima 30.5 627
PER-LIM-C 1339 25 1.6 0.078 Lima 31 2214
PER-LIM-D 1184 36 14 0.083 Lima 20.5 2854

#### 3.5. Chile

In Northern Chile, the city of Iquique lies on the Pacific ocean and at the base of a high plateau which makes it an ideal site for an IPHRO system as the region is very dry. Fig. 13 shows an image of the region and the potential lake area. Valhalla Energy already has done nearby site engineering and obtained approval for a pumped hydro energy system approximately 98 km south of Iquequi2, and thus this site could perhaps be the best first application for the IPHRO system anywhere in the world simply because a seawater pumped hydro and renewable energy system is already being planned. Indeed, other water starved regions around the world with IPHRO potential may want to invest in this early project as a means of also gaining rapid insight into the project and the process by which it is executed.  Fig. 13.  A-Index for topography near Iquique, Chile. Regions for potential IPRHOS applications highlighted in white with distance to nearest major city, Iquique, indicated by arrows. Figure options  Again, regions selected for further analysis are highlighted in Fig. 13 and detailed in Table 5. These regions represent a total lake area of approximately 24.3 km2 and could provide power and freshwater for about 22.4 million people. Given that the population of Iquique is only 180,601 [61], this “extra” water could be used to develop farms in the high desert, or for mining operations.

Table 5.Energy potential of IPHROS in regions in Chile.

Region Head (m) Surface area (km2) Distance from coast (km) A-Index Nearest major city (NMC) Distance to NMC Energy potential (GWh/cycle)
CHL-IQU-A 738 9.9 1.3 0.572 Iquique 7.4 483
CHL-IQU-B 981 9.4 7.2 0.136 Iquique 9.0 388
CHL-IQU-C 586 1.2 1.6 0366 Iquique 3.0 208
CHL-IQU-D 893 3.9 2.3 0.388 Iquique 9.5 113

#### 3.6. Middle East

The Middle East has great natural resources of many forms, including a rich history of great civilizations whose citizens accomplished amazing feats of civil engineering. Unfortunately now as in the past, water scarcity has often been a source of contention between peoples. Presently water shortages can be relieved by RO plants, but this currently mostly involves burning hydrocarbons to generate the power required. Fortunately there are many excellent IPHRO system sites in the Middle East as well as the will and means in many countries to plan and create for the future.

#### 3.6.1. Northern Red Sea (Egypt, Israel, and Jordan)

The region around the northern Red Sea along the borders of Egypt, Israel, and Jordan is also a region with large IPHRO potential. The mountains close to the coast of the Red Sea and the great need for freshwater in the bordering countries makes this an ideal site to investigate. Fig. 14 highlights the regions around the cities of Taba in Egypt, Eilat in Israel, and Aqaba in Jordan that have high A-Indices. As can be seen from the figure, for each of the major cities in the region, there are corresponding areas that can be developed for IPHROS. Table 6 summarizes these results.

Fig. 14.  A-Index for topography of regions in the northern Red Sea. Regions for potential IPRHOS applications highlighted in white. The closest city to the regions REDSEA-A, REDSEA-B, and REDSEA-C are Taba in Egypt, Eilat in Israel, and Aqaba in Jordan, respectively. Figure options

Energy potential of IPHROS in regions around the northern Red Sea.

Region Head (m) Surface area (km2) Distance from coast (km) A-Index Nearest major city (NMC) Distance to NMC Energy potential (GWh/cycle)
REDSEA-A 573 12 5.5 0.105 Taba 6.67 13503
REDSEA-B 560 3.8 7.2 0.0.078 Eilat 3.62 4380
REDSEA-C 817 32 8 0.102 Aqaba 5.11 13503

For the case of Taba, Egypt, the region highlighted by REDSEA-A could provide enough power and freshwater for nearly 11 million people, while REDSEA-B could do the same for up to 3.45 million people in Eilat, Israel and REDSEA-C represents the opportunity to provide over 29 million people with power and freshwater in Aqaba, Jordan. It is important to note that the entire population of Israel is only 8 million people and that of Jordan is 7 million people, therefore if only a fraction of the areas highlighted are developed for IPHROS, they still present a great opportunity to provide both power and freshwater to a vast majority of local inhabitants. Given extreme drought in the region and migration of people from war torn regions, IPHRO systems have the potential to employ many and provide power and fresh water to enable formation of new stable centers of civilization along the coasts.

#### 3.6.2. Iran

The population of Iran has its greatest density around Tehran which is close to the Caspian sea, but the region is chronically short of water. Fortunately there is great IPHRO system potential here. This could also help catalyze the renewable energy industry and negate the need for nuclear power plants. This might trigger substantial investment interest from the international community and enable Iran to emerge as a leader in the region for sustainable development.

Iran, one of the founding members of OPEC, has the world’s fourth largest proven crude oil reserves and the second largest proven natural gas reserves. Naturally, oil and gas have played a dominant role in the country’s energy dynamics, though the combination of Iran’s mountainous topography and IPHROS could catalyze development of a long term renewable and sustainable energy industry. Energy consumption in 2012 was roughly 278 billion kWh [62], with forecasts estimating a mean annual growth of 1.8% until 2018 [63].

The Tehran metropolitan area has a population of close to 14 million people, and serves as the nation’s political and economic capital. Over the past two decades, pollution has progressed relatively unchecked, and the air quality of Tehran has reached alarmingly dangerous levels [64]. Furthermore, water scarcity has evolved to be a significant issue for the city, and the nation at large, with disruptions and cuts arising frequently [65]. Essentially, these environmental issues pose a national security problem. In light of these issues, renewable sources of energy may alleviate some of the environmental strains while supplanting carbon-emitting power plants.

The IPHROS potential of sites near the capital of Tehran is shown in Fig. 15, with further details of highlighted regions in Table 7. The best sites for IPHROS are located over 100 km away from the edge of the city. Nested between the Caspian Sea and the Tehran metropolis lies the Alborz mountain range, running along the coastline for 950 km [66]. Therefore may not be viable sources of direct freshwater via pipelines due to the significant amount of pipe losses across such long distances, although water from the Owens valley in CA has long supplied Los Angeles from similar distances. Recent experience gained by Chinese engineers building a canal from the south of China to the north could perhaps be applied here. Thus it is envisioned that a combination of canals and tunnels could reasonably provide a means to deliver immense amounts of freshwater to the parched interior. Indeed, the combined potential of the regions represents a lake area of approximately 125 km2 and could provide enough electricity for over 115 million people. This far exceeds the population of Tehran, for which IPHROS would require only about 15 km2 of lake area.

Table 7. Energy potential of IPHROS in regions in Iran.
Region Head (m) Surface area (km2) Distance from coast (km) A-Index Nearest major city (NMC) Distance to NMC Energy potential (GWh/cycle)
IRN-TEH-A 778 32 6.4 0.122 Tehran 132 1672
IRN-TEH-B 888 93 4.2 0.211 Tehran 100 5547
IRN-SHI-A 565 245 8.4 0.067 Shiraz 200 9297
IRN-BAN-A 645 75 5.9 0.110 Bandar ’Abbas 128 3240
IRN-BAN-B 730 109 9.3 0.078 Bandar ’Abbas 72 5339

To the south lies the Zagros mountain range spanning the west and south of the country, hugging the northern coast of the Persian Gulf. Several cities derive the entirety of their energy needs from the oil fields of this region; namely, Shiraz and Bushehr. There is tremendous potential in IPHROS sites meeting the energy and economic needs of this region. The well-ordered topography of this region is ideally suited for the development of IPHROS technology, and the close proximity of major city and industrial centers provide a strong consumer base. The oil and natural gas industry can provide further economic motivation for the development of IPHROS as freshwater is needed for processing.

To the south, the IPHROS potential near the city of Shiraz is shown in Fig. 16. The highlighted region, detailed in Table 7, represents a lake area of 245 km2, if fully developed. Again, the distance between the reservoir and city is too great ( 200 km) for the system to directly pump freshwater to Shiraz, however IPHROS in this area could provide electricity for over 225 million people. With a population of approximately 1.5 million [67], a system of only 1.72 km2 of lake area would be required to meet all of the electricity needs of the city. (see Fig. 17).

Fig. 17.  A-Index for topography of region near Bandar ‘Abbas, Iran. Regions for potential IPHROS applications highlighted in white with distance to nearest major city, Bandar ’Abbas, indicated by arrows. Figure options

Farther east, the IPHROS potential near the city of Bandar ’Abbas is depicted in Fig. 16. The highlighted regions, detailed in Table 7, represent a total lake area of 183 km2, if fully developed. As before, with extremely long distances between the reservoir and the city, these regions may not be viable as a direct freshwater supply, however they could provide electricity for over 169 million people. With a population of only 435,000 [67], a system of only 0.46 km2 of lake area would be required to meet all of the electricity needs of the city. The freshwater produced could irrigate farms which can provide produce for local and export consumption.

Given the challenging state of relations between Iran and much of the international community, any opportunity that can potentially build trust and enhance confidence should be considered and studied in detail with a potential fast track demonstration project undertaken to show that we can all really work together to create a better world for all. Joint-ventures of renewable energy projects perhaps can build on the relationships established by current nuclear power discussions between Iran and the P5 + 1. Not only might IPHROS projects engage the educated and talented workforce of Iran, but they could provide the government a means by which to focus national attention on sustainable energy and water production development. Indeed, if the IPHROS technology could be developed as imagined, there would simply be no need for nuclear power plants in the region.

#### 3.6.3. United Arab Emirates

The United Arab Emirates (UAE), led by Khalifa bin Zayed bin Sultan Al Nahyan and other leaders within the UAE, has demonstrated a clear vision to plan for a renewable energy based future. For example, the Masdar Institute was created to develop renewable resource technologies and itself have a zero carbon footprint [68]. The total population of the UAE is about 15 million, with native Emiratis comprising just over 9 million [67]. The mountains west of Masafi have good IPHRO potential as shown in Fig. 18. Indeed given likely great wind energy potential high in the mountains and the vast desert (and mountain) regions available for solar PV plants, the entire country could be powered and watered with renewables, thus obfuscating the need for the full build-out of nuclear power plants that are currently planned [69].

Fig. 18.  A-Index for topography of the eastern United Arab Emirates. Regions for potential IPHROS applications highlighted in white with distance to nearest major city indicated by arrows.  Figure options

The IPHROS potential for the eastern United Arab Emirates is shown in Fig. 18. Further detailed in Table 8, the highlighted regions represent a lake area of nearly 13.5 km2. If fully developed, these regions could provide enough electricity and freshwater for 12.4 million people. If freshwater is the desired output of the system, this area could provide enough water for nearly 104 million people.

Table 8. Energy potential of IPHROS in regions in the United Arab Emirates.
Region Head (m) Surface area (km2) Distance from coast (km) A-Index Nearest major city (NMC) Distance to NMC Energy potential (GWh/cycle)
UAE-ALF-A 529 0.64 2.8 0.186 Khor Fakkan 2.7 23
UAE-ALF-B 619 12.8 8.5 0.073 Fujairah 7.3 533

#### 4. Discussion

Throughout history, as populations have grown to overtake local opportunities, large migrations have resulted. Although the world is finite, wind and solar power in combination with a modernized infrastructure should be able to satisfy most of humanity’s electrical energy needs; thus a new era might be possible where power and fresh water generated by renewables form the foundation for economic growth without the need for extensive migration. For example, local factories can be built to manufacture solar panels for use in energy parks built to supply regional IPHRO systems, while workers build and maintain the IPHRO systems. In some locations the depth change of the pumped hydro system’s storage reservoir can be designed to be small (10 m) providing a means for incorporating aquaculture into the system, which would create more jobs in the community. Residents realize that having more renewable energy generated locally, such as by having solar panels on their rooftops, leads to reliable power for industry and more fresh water and better food.

A reservoir designed to have a small depth change will necessarily have a relatively large surface area and thus higher evaporation losses. In any case, in hot dry regions reservoir surface coverings might be warranted. A simple and effective method for example is to use floating empty food transport containers not reusable for food transport [70]; [71]; [72] ;  [11].

The system adds additional advantages in the form of increased grid stability that need to be further researched and developed including: increasing the spinning reserves; offering additional operating reserves like primary, secondary and tertiary grid frequency controls; possibility of continuous control of reactive power in the grid (e.g in synchronous condenser mode w/o active power supply); and improving conventional thermal power plants utilization (i.e. they can run as base load resulting in higher efficiency). The majority of pumped hydro systems have black start capability even in the event of a grid outage, i.e. they can be brought very quickly into operation from stand still and without any external power supply. In addition to their black start capability, pumped hydro is able to provide system services in the further process of grid restoration. While grid restoration is in progress, further generators and controllable consumers are connected under control so that individual stable partial grids (isolated networks) can be established for a start. But once grid frequency and line voltage have returned to within tolerances, a major part of the consumers go online again uncontrolled. This results in considerable load variations that are difficult to predict while the grid is being restored. When partial grids are reconnected to each other, there will also be sharp jumps in load. Pumped hydro can easily balance these variations because they are able to follow steep power gradients, have short response times and feature motor-generators with a high rotating mass inertia. This ensures stable behavior over the entire output range, from no load to full load.

A further symbiotic potential is found as the system is designed and built: the engineering, economic, and environmental analysis conducted should be well documented and used to form the basis for classroom lessons in local schools so students can experience the power of collaborative, deterministic and creative thought. Hands-on learning can include students “Facing the Sun” to design, build, install, and operate solar panels and compete to see which teams can collect the most energy in a year, and which teams’ systems continue to operate year after year. Real time active problem solving of challenges that arise will not only be invaluable from an education perspective, the students might suggest great solutions. [73].

The pieces of the puzzle now can be seen to come together to form a picture of an efficient system that in addition to storing energy and generating power and fresh water may also offer other opportunities for researchers to consider:

1. Excess power from renewable energy machines flows to a seaside PH system.

(a) Saltwater is pumped up into an upper lined reservoir in adjacent mountains.

(i) The often changed “fresh” seawater can support aquaculture with less use of medicines to keep fish disease free.

(ii) Floating solar panels can reduce evaporation losses and generate additional power. If not solar panels, recycled materials can be used to limit evaporation losses.

A. Fish tend to eat at twilight and hence might grow faster if the lake is partially covered [74].

2. When power is needed, seawater flows down from the reservoir. A portion of the flow is diverted to the RO plant.

(a) Power is generated by the turbine.

(b) Fresh water is produced to meet population needs.

(c) Utilities are provided an additional resource to stabilize the grid.

(d) Typically 5% of the water initially pumped uphill to the reservoir will leave the system as brine which then exits the RO plant at 90% of the input pressure and can flow through a turbine to also generate electricity

(e) Total system outflow, can be discharged directly into the ocean because the brine from the RO plant will be diluted by the seawater output from the main power generation turbine.

(i) Before exiting to the sea, the water could flow past adsorption polymers for harvesting uranium.

#### 5. Conclusions

The intent of the current paper has been to show that large-scale energy storage and fresh water production are readily realizable in many dry coastal heavily populated regions of the world. Significant further focused regional study is required to address issues such as transportation costs of solar and/or wind energy from nearby suitable sites, and fresh water transportation to large populated regions; and then compare other alternatives that might exist such as distributed PV with residential battery storage systems and conventional RO desalination plants. A detailed site specific analysis will be required to obtain an accurate LCOE as well as delivered cost of fresh water.

In this paper, a symbiotic system for producing both freshwater and electric power from solar and wind resources were presented with a generic example of economically meeting the needs for one million people. Site specific case studies for Southern California, Baja, Hawaii, Chile, Peru, and the Middle East are investigated. In Southern California the power and freshwater needs for 28 million people could be realized. Significant employment opportunities resulting from building and maintaining the system can also be realized, as well as economic growth when a region can offer reliable power and freshwater supplies.

On the other hand, the environmental trade-off of creating IPHROS lakes in the region must be weighed against the effects of drought and further drawing down reservoirs, as well as burning fossil fuels to create electricity for RO plants. Weighing in on the decision to build IPHRO systems, further research could examine how much water would be required to support enough flora to reverse desertification and help create a self-sustaining local climate, such as occurs in the (perhaps soon to be?) former Amazon rain forest.

The Supplementary Materials A for this paper investigates additional case studies for IPHRO systems around the world including Brazil, Morocco and China. The A-Index and energy potential for all the regions that have currently been analyzed is summarized in Fig. 19. Many regions in Chile, Hawaii, China, and Iran have an extremely high A-Index. Of the top ten regions, the area around Tehran not only has a high A-Index, but also has a large energy potential. Similarly, studies have been done considering connecting the Red Sea to the Dead Sea which lies about 410 m below sea level, where in one scenario the desalination plant would be collocated with a hydroelectric plant near the Dead Sea so both are fed by the difference in altitude between the dead sea and the oceans [75]. Due to environmental concerns projects have not moved forward; however, creating an IPHRO system in the mountains of Jordan near the Red Sea would be feasible and the brine outflow (or all the plant outflow) could be to the Dead Sea. Areas of Africa are also in need of such systems [76]. Also in the Supplementary Materials A is a high-resolution analysis of the economics of an exemplary project in Southern California using real time power demand information and a wide array of economic factors. The first order analysis indicates feasibility of the approach, but a much more detailed analysis is warranted as part of any significant effort to move forward. Such detailed analysis helps to understand the effect of actual market prices, regulatory obligations, system configuration, capital and operating cost on the project’s technical and financial performance. This detailed analysis shows that although at current prices PV alone has a higher return on investment than an full IPHROS system, if modest (and realistic) price increases occur returns become higher for the full IPHROS system than the PV alone in similar conditions and the rates of return meet the hurdle rate of infrastructure funds.  Fig. 19.  Summary of A-Index and energy potential of all regions investigated in this paper (*) and its supplemental materials (+).  Figure options

With careful planning and execution, large scale energy storage can convert volatile and intermittent energy associated with renewable energy systems into an economical controllable base load generation source with similar quality and availability as provided by thermal generation systems (e.g., coal or gas fired systems). In addition, a IPHRO system can also serve as an effective base load source for fresh water generation via a simplified RO plant to help provide power and water for all, and create whole new economies as envisioned in Fig. 20.  Fig. 20.  IPHROS is more than a “battery” it is full system solution that can supply renewable energy, fresh water, grid stability, and jobs for the region. Figure options

#### 6. Further work and considerations

In the debate over the cost of converting converting to carbon free energy systems verses affordability and jobs, it should be considered that the Gross World Product is on the order of 75 trillion dollars, and at a cost of \$5000/person to provide 1 kW of power and 500 liters of fresh water per day, it would only take 5% of the GWP every year for 10 years to enable 7 billion people to go green, a much better option than all the future wars that may otherwise be fought by displaced people fighting for scare resources.

The decision to build an IPHRO system should depend not only on the LCOE and delivered cost of water as compared to conventional systems, but also on to the long term prognosis for alternatives as regional impacts of climate change create policy uncertainties.

In addition, the development of IPHRO systems is not just about providing renewable energy and freshwater, it is also about creating a societal approach to supplying two of our greatest needs; and since renewable power systems tend to be widely distributed and it will take decades to build all the systems needed, many skilled jobs can be created and sustained. As IPHRO related systems come on line, workers will also be needed to maintain these systems and replace and recycle systems at their end of useful life. The question of IPHRO systems is thus perhaps not ‘does it work?’, but ‘what does it make possible?’ (Adopted from Brian Massumi in the translator’s forward of Deleuze and Guattari’s ‘A Thousand Plateaus’ [77], this philosophy well describes the symbiotic approach to engineering systems design considered here.) 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.

As an example of how an IPHRO system might do far more for a region than just provide renewable energy and fresh water, it is hypothesized here that migration issues might be better addressed by creating opportunities in regions from which migrants come, for example in accordance with the Desertec vision [78]. If a portion of the resources currently allocated to resettling refugees in Europe, as much as 25,000 euros per year per refugee, were used to build IPHRO systems in the Middle East, a new mutually beneficial ecosystem could be created. This could show how we can all do better by putting The World First:

The most important calculations are those that will save nations,

Like building wind plantations, instead of more gas stations,

And seeking new destinations in space, is complicated,

The Earth is worth saving from troubles that we created,

It’s time to double efforts, in land, water and sky,

It’s time to come together, it’s time to solarize,

The answer is blowing in the wind and flowing in the water,

The polar caps are melting, sea levels are on a rise,

Surprised that super storms still haven’t opened our eyes,

Some scientist theorize, and politicians decide,

That man is not at fault, so they gamble with our lives,

Let’s get off the sidelines and show we’re not psychotics,

Insane, awaiting change from the same planned periodic,

Debates with fate at stake, of our consequent generations,

Reversing the complications, requires more impatience,

No time to be wasted, this fight is not symbolic,

A catastrophic plight, or relationship symbiotic…Decide…It’s Time…

Action, no longer passive, too massive to stagnate,

Reaction, we seize the moment, accelerate to create,

With force, remove mobs from desperate situations,

Renewed energy jobs, will lay the foundations,

Question, research, guess, test, analyze with a passion,

Cause building what we create, is the prevalent high fashion,

Our fate’s in our control, so let’s stand hands united,

The only way we’ll fold, is in a world divided

It’s time we all put the World First

Marc Graham and Alexander Slocum (2015)3

Acknowledgements

This work originated from a class that received support from the S.D. Bechtel, Jr. Foundation through the MIT Energy Initiative; and has been supported in part by: the Cooperative Agreement between the Masdar Institute of Science and Technology, Abu Dhabi, UAE and the Massachusetts Institute of Technology, Cambridge, MA, USA, Reference 02/MI/MIT/CP/11/07633/GEN/G/00; the U.S. Department of Energy Office of Nuclear Energy under Contract No. DE- NE0008268, and the National Academies Keck Futures Initiative. The authors are extremely grateful for the detailed comments from the journal reviewers. Mark Allen of Oceanus Power & Water also provided in-depth review of the concept and analysis spreadsheet for which we are very grateful. Dr. Klaus Krueger of Voith Hydro provided insight to hydropower plant siting and configuration considerations and the ability of a hydropower plant to help restart a grid after a blackout.

#### Supplementary data

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