When is energy-intensive desalination a last resort?
One of humankind’s worst tragedies is currently unfolding in the Horn of Africa, and it is caused by the absence of water. Two years of failed rain, and subsequent drought and famine, is responsible for the daily deaths of roughly 2,000 people in Ethiopia, Kenya, and Somalia.
According to the Director of Yale’s Environmental Engineering Program, water scarce countries like these in Africa and the Middle East can achieve greater water security by developing desalination plants. However, as you might have guessed, this conviction does include a rather large caveat.
De-salting the sea
Menachem Elimelech also told PBS that even the most advanced desalination technologies, which are becoming increasingly necessary in countries like Israel, Singapore, and Spain, still use three times as much energy as conventional water treatment.
There are two kinds of desalination technologies at work in the world. The Gulf Countries such as Saudi Arabia and Kuwait, which have been hydrating their citizens with desalinized water for decades, still rely on archaic thermal desalination plants that boil water and condense the resulting steam in order to produce potable water.
This process uses a lot of energy.
But even new technologies such as reverse osmosis, which involves blasting seawater at very high pressure through molecular-sized perforations in a plastic membrane that captures all but 0.05% of the salt pumped through it, is energy intensive.
The most advanced desalination plant requires as much electrical energy to produce 1000 liters of clean water as 30 100 watt lightbulbs left on for an hour. If this doesn’t seem a lot to you, consider this: Israel’s fifth desalination plant along the Mediterranean produces 500 million cubic meters of water every year. A cubic meter is equivalent to 1,000 liters.
That’s a lot of lightbulbs, particularly for Israel, which has very few of its own energy sources with which to power these plants. But even oil-rich nations have to exercise caution.
Hello… global warming.
Arwa recently posted a Carboun infographic that maps the carbon emissions of Middle Eastern countries. It is no coincidence that water scarce Qatar – a major oil and gas hub – has the highest per capita emissions in the world, or that Kuwait and the UAE came in 3rd and 4th given how richly they depend on desalination for their water resources.
Climate change caused by such devastatingly high carbon emissions notwithstanding, though this alone is a serious enough, increasingly pinched oil supplies should inspire managers in the Gulf to seek out more energy efficient technologies. Otherwise, they will become even more expensive than they already are, and eventually, when oil runs out completely, they will cease to exist.
The solar option
Menchem Elimelech from Yale did not mention solar-powered desalination plants in the brief interview published by PBS, but the United Arab Emirates have been testing this new technology as a potential alternative to the current model. In the meantime, the Gulf countries have no choice but to continue burning up electricity for water. But for everyone else, it should be the last resort after water conservation and wastewater reuse.
:: PBS
More on Desalination in the Middle East:
Solar Desalination Tech Tested by Emiratis
Saudi Arabia to Replace Oil with Sun Power for Desalination Plants
Israel Sends Wrong Message About Desalination
image via Lance Cheung
Just so you know… The 3rd World Infrastructure is already at the last resort.. It would be inhumane to millions of people if Desalination Plants were not used… You must care about people, animals and the worlds forests…
Desalination is the only resort.. They will innovate to using other methods that generate power to plants… The Horn Of Africa is Deprived of Clean Water to drink and Farm… Money should be no Object..
It seems to me that even these “archaic thermal desalination plants that boil water” can be given a boost in efficiency and a corresponding reduction in their energy usage and carbon footprint with solar pre-heating. Adding conventional solar panels inline with a simple water-water heat exchanger can preheat the saline feed, so that less energy is needed to bring the heated water to the boiling point and produce the steam….
Simply lining the roofs of the existing facilities with standard glass panels common in the MidEast, and cutting in a few cast-iron exchangers with a couple of valves would be a negligible expense for the operating budgets of facilities burning tons of fossil fuel night and day, and would probably yield break-even times in a matter of months from the fuel savings. This would cost MUCH less than overhauling the plant to some new technology, add useful life to the plant, and in cases where the cooling capacity of the condensers was not being used at maximum, also increase production. (I.e., it would take less time to boil the heated water, and so more steam would come out of the boilers per unit time, and the amount of time to condense the steam to potable water and the capacity of the coolers to take in more steam would be the limiting factor for the increased flow of produced water.)
This is an important piece. In a water-starved Middle East, conservation efforts alone seem unable to provide for basic needs, especially as drought becomes more prevalent due to global change. Energy-efficient technologies that will enable desalination and other approaches to freshwater recovery and conversion must be sought.
One hopes that the scientific talent present in the region will help realize this goal.