In March, the residents of Cape Town, South Africa were delivered a reprieve from doomsday when city officials announced that “Day Zero,” when the city will be forced to cut off the taps to city residents, had been pushed back and was no longer predicted to occur in 2018.[i] Extreme water conservation measures, including rationing of 50 liters per resident per day—roughly a sixth of the average American’s daily usage—have slowed sinking reservoir levels, but Cape Town’s future is still dependent on getting decent rainfall this winter. Ironically, counting on the rain was one of the primary causes for the current crisis, as city officials in recent years banked on average historical rainfall patterns holding despite warnings of depleted reservoirs and an increasingly unpredictable climate.
Having grown up in southern California, I’m no stranger to drought and alarming predictions of water scarcity, albeit in less dire circumstances. The state’s water supply has been under constant strain for my entire life. Yet I never saw any impact on southern Californians’ lifestyle until I went home to stay with my parents in Orange County in the summer of 2015, a few months into state-mandated water restrictions. The conservation measures were noticeable, but nowhere near as painful as Cape Town’s. Before the situation got desperate, California was bailed out by an unusually wet winter in 2016-2017 that refilled reservoirs across the state and led to a record snowpack in the Sierra Nevada, the main water source for much of the state.
In hindsight, California got lucky. Cape Town’s ongoing battle to forestall “Day Zero” illustrates the outcome California could have gotten—and could still get. The state’s Water Resources Control Board is considering re-imposing restrictions amid signs that California could be slipping back into drought conditions.[ii] As in South Africa, American water management officials can’t bank on past precipitation patterns holding and have to prepare for an increasingly volatile water supply exacerbated by climate change.
Cape Town is currently scrambling to build four desalination plants and a wastewater processing plant as well as drill new water wells as part of a last-ditch effort, but most of those projects are behind schedule and won’t be operational in time to impact the current crisis. One question raised by California and Cape Town is: why is it that our water management strategy in drought-prone regions is so often reactive rather than proactive?
Water supply management in the western United States admittedly presents an intricate dilemma, lying at the intersection of decades of shortsighted public policy, an increasingly unpredictable climate, unfavorable economic incentive structures, and myriad engineering challenges distributed across interstate, state, regional, and municipal levels. It’s a true system of systems problem.
The water supply problem presents a full slate of challenges and there’s no silver bullet to address them all. But there is clearly a need for a diversified water supply portfolio that includes drought-resistant sources that can provide drinking water on a large scale. Desalination—the process of removing salt and minerals from seawater or brackish water—could be among the potential solutions.
Though it is often decried for its significant power consumption and detrimental environmental impacts, desalination may present one of many potential paths forward for arid, climate-challenged states like California or Texas. Desalination has faced stiff resistance to adoption in the United States, which primarily hinges on the higher price consumers have to pay for drinkable water supplied through desalination compared to other fresh water sources like rivers or groundwater.
Desalination at utility-level production is a highly energy-intensive process using current methods. Seawater reverse osmosis, the most commonly used technique in the United States, requires pumping water through several stages of pretreatment before heating it to high temperatures and forcing it through semipermeable membranes at high temperature and pressure to strain out salt and particulates. These energy requirements add up to half or more of the total cost of desalination in most plants. Some consumers are also concerned about the environmental impacts of desalination, like the effect of discharging the highly saline brine byproduct on ocean life and the greenhouse gas emissions from all the required power production.
Obviously, there’s a wide array of barriers to desalination adoption that must be overcome. Yet recent advances in desalination technology show promise for mitigating these concerns while bringing costs down.
As the National Research Council noted in a seminal 2008 report on desalination that holds true to this day:
“Water scarcity in some regions of the United States will certainly intensify over the coming decades, and no one option or set of options is likely to be sufficient to manage this intensifying scarcity. Desalination, using both brackish and seawater sources, is likely to have a niche in the future water management portfolio for the United States.”[iii]
And a niche it should have. Desalination plants could serve as a hedge against a Cape Town-like crisis, staving off a potential Day Zero in the worst-case situation—if American consumers could be convinced that paying a slight premium for drought-resistant water sources to diversify their water supply portfolio is worth it. But that will likely require more cost parity between desalinated water and other water sources as well as minimizing desalination’s environmental impact to assuage public resistance and allow the technology to be accepted as one piece of a larger climate change adaption strategy.
In a bid to increase efficiency and reduce costs, the desalination industry has already shifted toward collocating desalination plants with coastal power plants in an effort to maximize efficiency: the seawater pumped in as cooling water for the power plant is used for desalination since it is already heated part of the way to the high temperatures required for traditional desalination methods, which reduces energy requirements; construction costs can decrease 5-20% as the two plants share seawater intake and discharge facilities; and less electricity is lost in the transfer between plants because the distance is reduced.
The recently opened Carlsbad Desalination Plant in San Diego County, a great example of a collocated desal plant and now the largest in the nation supplying 50 million gallons (190,000 cubic meters) of drinkable water per day, is considered state of the art by American desalination standards. Yet it also illustrates the enduring challenges to desalination’s acceptance and competitiveness in the United States. The plant is considered relatively efficient in its energy usage and produces water at fairly competitive prices, but it still draws power from the local grid, which is sourced from 70% nonrenewable energy. On top of that, it was built on the site of the 1950s-era, natural-gas burning Encina Power Station, which the county has been trying to shut down. The poor optics helped fuel a slew of criticism and lawsuits against the plant, even though Poseidon Water, the operator, purchased carbon emissions offsets and undertook reforesting programs. Lingering bitterness over Carlsbad has held up development of other desal plants in Southern California.
The American desalination industry would do well to learn from the examples of oil-rich Saudi Arabia and the United Arab Emirates, which ironically are both global leaders in renewable energy-powered desalination. Saudi Arabia’s Al Khafji plant became the world’s first operational, large-scale, solar-powered desalination plant when it came online in November 2017. It features a 15-megawatt panel array using polycrystalline solar cells, which produce enough electricity to support the plant’s desalination of 60,000 cubic meters of water per day although not enough to also serve as a power source for the surrounding community. But the whole project is valued at $130 million, well under the Carlsbad plant’s $1 billion total construction price tag. Saudi Arabia got a third of the production capacity but at 1/8 of the capital cost, in addition to shedding the stigma against burning fossil fuels.
Though critics have charged that the operating costs of solar-powered desal are prohibitively expensive, an ambitious effort underway in Abu Dhabi suggests that solar-powered desalination is becoming increasingly competitive. The Masdar project, bankrolled largely by the UAE’s sovereign wealth fund, aims to create an entire carbon net-zero, self-sufficient city for 50,000 residents. Though the overall effort has run into setbacks and the revelation that being completely net-zero isn’t feasible, a solar-powered desalination pilot program under the effort has shown strong potential for scaling up to help supply the city.[iv] Capitalizing on cheaper and more efficient solar cells would make this project quite affordable—cutting the price of water from solar-powered desalination in half by 2050.[v]
In the United States, such high-risk ventures are less practical without government support. But the federal funding picture changed drastically in FY 2018. The Department of Energy issued a funding opportunity announcement in September 2017 and expects to start making grants totaling $15 million in this fiscal year to support solar-powered desalination research, especially for research into integrating solar desalination systems.[vi] That’s a relatively massive shift by U.S. federal funding standards as the Department of the Interior’s Bureau of Reclamation—historically the largest federal funder of desalination research—expects to grant just $1.2 million under its desalination research program for FY18.[vii] Desalination companies and researchers should seek to leverage this bow wave to reinvigorate renewable energy desalination research in the U.S. and propagate this interest in “clean” desalination. Other barriers remain to making solar-powered reverse osmosis desalination competitive and operating it on a large-scale—such as how to efficiently store solar energy at nighttime when the desal plant still has to run—but those will likely prove surmountable in the face of technological advances.
If American water management officials were to derive any lesson learned from the Cape Town water crisis, it should be that we cannot rely solely on the methods that helped us cope with past droughts and that adapting to future droughts driven by an increasingly erratic climate will require bold, innovative strategic planning that can attract federal research support and overcome public resistance. Integrating renewable energy production with desalination represents exactly that kind of thinking.
Written by Maclyn Senear firstname.lastname@example.org
[i] David McKenzie and Brent Swails, “Day Zero deferred, but Cape Town’s water crisis is far from over”, CNN, March 9, 2018, https://www.cnn.com/2018/03/09/africa/cape-town-day-zero-crisis-intl/index.html
[ii] Associated Press, “Could California drought restrictions slash water rights? Some think so,” CBS News, Feb. 21, 2018, https://www.cbsnews.com/news/could-california-drought-restrictions-slash-water-rights-some-think-so/
[iii] National Research Council, 2008, Desalination: A National Perspective, Washington, DC: The National Academies Press, https://doi.org/10.17226/12184
[iv] “Renewable Energy Water Desalination Programme,” Masdar, 2018, http://www.masdar.ae/assets/downloads/content/3588/desalination_report-2018.pdf
[v] Richard Martin, “To make fresh water without warming the planet, countries eye solar power,” MIT Technology Review, May 12, 2016, https://www.technologyreview.com/s/601419/to-make-fresh-water-without-warming-the-planet-countries-eye-solar-power/
[vi] “Funding Opportunity Announcement: Solar Desalination,” Department of Energy, Solar Technologies Office, DE-FOA-0001778, Sept. 27, 2017, https://www.energy.gov/eere/solar/funding-opportunity-announcement-solar-desalination
[vii]“Desalination and Water Purification Program for Fiscal Year 2018,” U.S. Department of the Interior, Bureau of Reclamation Research and Development Office, Funding Opportunity Announcement No. BOR-DO-18-F002, Feb. 2018