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How Solar Energy Can Save Yemen's Capital

Sanaa, the capital of Yemen, may be the first capital city in the world to run out of water. Due to Yemen's defunct government, water-guzzling addiction to a drug called qat, and lack of conservation practices, Sanaa's 2 million people may become "water refugees" by the year 2025. Furthermore, water shortages compound the country's chronic poverty, malnutrition, and tribal fighting over scarce resources. Solar desalinization combined with more efficient water management can help save Sanaa.

According to legend, the son of the Biblical character Noah created Sanaa on the highest ground he could find after the Great Flood.  Originally built 2,200 meters above sea level to prevent floods, the modern-day capital city of Yemen now faces dehydration.  Eighty percent of the city’s water comes from non-renewable sources in the Sanaa Basin. This percentage will soon fall to zero when the Basin is depleted between 2015 and 2020.  Five years later, Sanaa will completely run out of water.  Some government officials have already contemplated moving the capital to a coastal city like Aden or Mukalla as a last resort.

Yemen’s water shortage is a humanitarian crisis verging on catastrophe.  By 2025, the country’s population is expected to double. This increase will require an additional 4.6 billion cubic meters (m3) of water - about 1.1 billion m3 more than the total amount used now.  The population growth rate (3%), as one of the highest in the world, stretches water resources dangerously thin.  From now until 2025, per capita consumption is predicted to fall from 125 m3 to 62.5 m3 per year. This latter figure is eight times less than the amount of water that the World Health Organization (WHO) recommends to ensure survival (500 m3).

To ensure survival, the capital city needs to “manufacture” new sources of water before the Sanaa Basin becomes the next Arial Sea.  A recent World Bank publication captured the urgency of the Basin’s looming depletion: “in no other country in the world is the capital city of a nation literally going to run out of water in a decade.” The Trans-Mediterranean Renewable Energy Cooperation (TREC) can help Sanaa win the race against water depletion time.  On Yemen’s Red Sea coast, TREC is promoting solar thermal power and desalination plants that produce a combined total of 1 billion m3 of water per year.

The infrastructure would consist of concentrating solar collectors with parabolic trough mirrors.  Sunlight would reflect off these mirrors onto an absorber pipe, in which feed water from the Red Sea would be converted into hot vapor for power generation.  The plants will produce 10,000 GWH of electricity per year - about one-third for desalinating and two-thirds for pumping water. The amount of power generated in these plants alone is equivalent to about one third of Yemen’s total energy consumption and production.

Two different processes, Multi-Effect Desalination (MED) and Reverse Osmosis (RO), would desalinate the water.  MED desalinates water in a multiple boiling process without supplying any additional heat after the first stage.  Steam from a boiler heats a series of tubes, generating energy for evaporating the saline water that they contain.  In the next stage, the vaporized saline water condenses into fresh water product while giving up its heat to evaporate the remaining seawater.

The other process, RO, requires energy for pressuring feed water against a membrane to separate out the solutes.  As portions of the water enter this membrane, the salinity of the unprocessed feed water rises.  The leftover brackish water is discharged in amounts ranging from thirty-five to one hundred percent of the desalinated output.  Excess heat can be stored in tanks containing molten salt so that it can later be used to power steam turbines during prolonged stretches of cloudy days, the nighttime, or when demand peaks.  In addition, heat trapped under the reflective mirrors can be used for horticulture. 

Positive Aspects

Desalination powered by virtually inexhaustible forms of energy like solar is Yemen’s only long-term option.  Oil and natural gas-powered plants are unsustainable.  Yemen’s oil reserves are expected to be depleted around the year 2017, and its gas supply will probably not last much beyond 2040 unless new fields are found.  The country’s need for water, however, will last forever.  Solar desalination secures a long-term water supply for Sanaa because it does not depend on resources that will expire.

Additionally, after solar desalination begins operating, any surplus water can be deposited into the Basin to increase its water table.  By revitalizing the Basin, solar desalination can provide a cushion against occasional gaps between supply and demand for desalinated water.

The total cost of the solar thermal power plants, desalination (MED and RO), and infrastructure (pipeline and pumping) is an estimated US $11 billion.  According to TREC, this amount is equivalent to the world market value of around four percent of Yemen’s oil reserves.  Furthermore, TREC argues that an investment into Sanaa is an investment into a vital technology for the development of the entire MENA (Middle East-North Africa) region.  The positive externalities of solar desalination for the larger region may attract a portion of the required investment.  Solar desalination has a hefty start-up cost, but with a concentrated effort, it may not be entirely prohibitive. 

Negative Aspects

In addition to the solar thermal power and desalination plants, TREC’s blueprint consists of 250 kilometers of steel pipeline and four pumping stations.  There is little reason to trust Yemen’s capacity to safeguard this entire infrastructure on its own.  The central government’s control outside of Sanaa is severely limited, especially in the coastal areas where the plants will be located.  Sea piracy in the region, the bulk of which occurs in the Gulf of Aden, warns of the government’s anemic grasp on the security situation.  Solar desalination gives the already futile security apparatus yet another piece of infrastructure to protect.

Another concern with solar desalination is the estimated price of water to consumers.  Desalination costs will fall to around US $0.7 per m3 after a twenty-year depreciation period. However, before the heavy start-up costs are diffused across time, the price will be as much as US $2 per m3 accounting for pumping and water production costs. Initially, the bankrupted government may have to procure the means to subsidize water priced at US $2, as this amount is double what 15.7 percent of Yemenis earn in one day (est. 1990-2005).Without making this water affordable to consumers, solar desalination is impractical.

TREC’s plans in Sanaa are stalled.  Anwar Sahooly, the Chairman of the Technical Secretariat for Water Supply and Sanitation Sector Reform in Yemen, cited unresolved issues like the high initial cost of water to consumers.  “Solar desalination is merely a good academic exercise,” he stated.

But it remains to be seen that the government can implement the conservation measures that he advocates before Sanaa runs out of water.  Desalination powered by a virtually inexhaustible energy source is an enormous challenge in terms of the costs of infrastructure and making the initial price of water affordable to consumers.  Yemen may have to meet this challenge in order to keep the 2,500-year old city of Sanaa alive.

Thousands of years ago, Yemen was at the forefront of agricultural production and water efficiency practices.  Between 750 and 700 BC, the ancient Kingdom of Saba’a (Sheeba) built the Marib dam in modern day northern Yemen.  The dam succeeded in capturing irrigation water from rainfall for roughly a millennium until it broke down in the sixth century AD.  Once a bastion of water efficiency, there may be a trickle of hope for Yemen to revive its capital city.   

Lead image: Yemen map via Shutterstock

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