Desalination

Excellent article on this from the series on California Water Policy at California Globe.

An excerpt.

“On May 12, the California Coastal Commission Board of Directors voted 11-0 to deny the application from Poseidon Water to build a desalination plant in Huntington Beach. Since 1998, Poseidon has spent over $100 million on design and permit work for this plant. At least half of that money was spent on seemingly endless studies and redesigns as the Coastal Commission and other agencies continued to change the requirements. Poseidon’s denial makes it very unlikely another construction contractor will ever attempt to build a large scale desalination plant on the California coast.

“This is a historic mistake. If you’re trying to eliminate water scarcity, desalination is an option you can’t ignore. Desalination has the unique virtue of relying on a literally inexhaustible feedstock, the world’s vast and salty oceans. At an estimated total volume of 1.1 quadrillion acre feet (1.1 billion million acre feet), there will always be enough ocean.

“A balanced appraisal of desalination would acknowledge its potential while also recognizing the absurdity of suggesting it is a panacea. On one hand, desalination can be an indispensable solution to water scarcity. In Israel, for example, five massive desalination plants on the shores of the Mediterranean Sea produce nearly a half-million acre feet of fresh water per year, an amount the nation plans to double by 2030. Israel’s Sorek Desalination Plant, located a few miles south of Tel Aviv, produces 185,000 acre feet of fresh water per year, from a highly automated operation that only occupies about 25 acres. Up to 80 percent of Israel’s municipal water comes from desalination. Thanks to desalination, this nation of nine million people has achieved water abundance and is exporting its surplus water to Jordan.

“On the other hand, just as renewable energy only provides a small fraction of the global energy supply, desalination only constitutes a small fraction of global water supply. Altogether, not quite 20,000 desalination plants worldwide produce less than 50 million acre feet of water per year. That’s an awful lot of water, but it’s less than one percent of global water consumption. To make a dent in the estimated 7,500 million acre feet per year of worldwide water consumption, desalination capacity would have to increase by an order of magnitude, to 500 million acre feet per year. In turn, that achievement would require about 200 gigawatts of continuous power, equivalent to the full output of 100 Hoover Dams.

“The Energy Cost of Desalination is Not Prohibitive

“Then again, as we will see, and for a variety of reasons, the frequently heard assertion that there isn’t enough energy available to spare any more of it for desalination is not true. For starters, 200 gigawatt-years is only 5.98 quadrillion BTUs, and worldwide, total energy production in 2020 was estimated at 528 quadrillion BTUs (or 17,653 gigawatt-years, or 557 exajoules, which is currently the authoritative BP Statistical Review of Global Energy’s energy mega-unit of choice). Therefore, to desalinate 500 million acre feet of water per year would only consume 1.1 percent of current global energy production.

“Taking all of this into account, it’s fair to say that desalination is clearly part of the solution to water scarcity. The potential for a perpetual input of water from desalination plants to tilt the demand and supply equilibrium from one of scarcity to one of abundance should not be underestimated. Israel’s experience is proof of that.

“Here in California, the energy required to desalinate seawater is considered one of the prohibitive obstacles towards wider adoption of the technology. But when the alternative to desalinating seawater is paying the energy cost of pumping it from the Sacramento Delta through nearly 300 miles of aqueducts, then lifting it over the Tehachapi pass, the energy costs become less daunting.

“The following two charts illustrate the amount of energy necessary to deliver water to Southern California’s coastal cities from three differing sources: upgraded local wastewater treatment to indirect potable standards, interbasin transfer via the California Aqueduct, and desalination. Both charts examine the energy required to deliver 1.0 million acre feet of water. The first chart shows how many units of electrical energy are required, the second chart shows how much flow of electricity a power plant would have to generate in order for each system, operating continuously, to deliver one million acre feet in one year.

“The first chart clearly shows that processing wastewater for indirect potable reuse is far more energy efficient than the alternatives. These figures are based on the average, taking into account the power requirements of two treatment plants, the Orange County’s Groundwater Replenishment System (GWRS), along with the wastewater recycling plant which is proposed to be built in the City of Carson in the Los Angeles Basin. According to engineers at GWRS, the plant draws 13 megawatts to treat 103,000 acre feet per year. Information provided by Met on the Carson plant’s design estimated a 30 megawatt draw to treat 168,000 acre feet per year. Based on the average of these two figures, these plants would require 1,309 gigawatt-hours to produce one million acre feet of water.

“By comparison, the figures for desalination are based on the Carlsbad plant which draws 23 megawatts to produce 55,000 acre feet of water per year – not including power to deliver the desalinated water. That equates to 3,529 gigawatt-hours to produce one million acre feet of desalinated seawater.

“As described earlier, the figures for the California Aqueduct were calculated based on adding up the power consumption per unit of water lifted for each of the six pumping stations that start with the Banks pumping plant just south of the Sacramento Delta, and terminate with the Edmonston pumping plant at the base of the Tehachapi Mountains. This titanic transfer of water has an energy cost of 3,448 gigawatt-hours per million acre feet of water delivered, only slightly better than desalination.”

To read the rest, The Abundance Choice, Part 11: The Desalination Option – California Globe