The seriousness of the current drought in California was evident during a recent visit to the Salinas Valley. In fact, it’s believed that ocean water is seeping into the coastal fresh-water aquifers.
Desalination is a working technology used throughout the world to combat the shortage of fresh water. If it works, why aren’t there more desalination plants dotting the California coastline? Because desalination plants are expensive, use an inordinate amount of electricity, and are fraught with environmental concerns.
DeepWater Desal has spent three years looking at the challenges overshadowing desalination plants, and the company believes it has viable answers for every concern. However, the solution is only feasible if the desalination plant is located near Monterey Bay, and the plant partners up with a large data center.
Let’s break down each challenge, and then look at what DeepWater Desal proposes as a solution.
Desalination plants are expensive: Water agencies in Monterey County need more fresh water to meet demands, though none of the agencies are large enough to build a desalination plant on its own. To leverage the scale of a larger, more efficient plant, the water agencies came together to form the Joint Powers Authority. Sharing ownership makes the desalination plant affordable for even the smaller agencies.
Desalination plants need large amounts of electricity: Reverse osmosis, the desalination process, forces high-pressure ocean water through a membrane to remove the impurities; this process requires huge amounts of electricity. DeepWater Desal’s answer is to create a new municipal utility that can buy electricity at wholesale prices. On its website, DeepWater Desal states:
The facility will utilize an electrical power source mix weighted toward low-carbon, renewable energy, and off-peak load operation to minimize costs and favor nighttime wind power resources. As part of its low-carbon strategy, DeepWater Desal has entered a power supply agreement with PV2 Energy, a planned solar farm in the nearby Panoche Valley.
Reduce damage to local marine life: In a circuitous way, reducing damage to marine life is why Monterey Bay was chosen, and the desalination plant-data center union came into being.
The Monterey Bay is well known for its unique submarine canyon that starts close to shore near Moss Landing (shown to the right along with the inlet location, the red dot), the proposed site for the desalination plant. The submarine canyon extends 95 miles into the Pacific Ocean.
Being so deep this close to shore is important. DeepWater Desal explains (the full report):
Because shallow surface waters receive more sunlight than deeper ocean waters, they are warmer and contain more life. By going deeper, a screened, deep water intake pipe can avoid the productive shallow waters and reduce the harmful effects from sucking in tiny sea life.
However, going deeper (100 feet has been proposed) creates a problem. At that depth, the water is too cold for the reverse-osmosis process. Somehow the water temperature must be elevated. The proposed solution is a data center.
Why not use the cold ocean water to cool the data center’s electronics, and then pump the water to the desalination plant? James Hamilton, Vice President and Distinguished Engineer at Amazon Web Services, wrote a blog post about the process: “If the water is first run through the data center cooling heat exchanger, at very little increased pumping losses, the data center now gets cooled for essentially free (just the costs of circulating their cooling plant). And, as an additional upside, the desalination plant gets warmer feed water which can reduce pumping losses by millions of dollars annually. A pretty nice solution.”
For those wondering about using ocean water to cool data centers, Google has already determined how to deal with the corrosive nature of sea water when it converted a paper mill in Hamina, Finland into an ocean water-cooled data center.
How much water?
The estimated output of the plant each year will be 25,000 acre-feet (8,146,285,800 gallons) of potable water. Member agencies will receive water from the desalination plant as far north as Santa Cruz, as far east as Salinas, and as far south as the Monterey Peninsula.
To get an idea of the scope of the project: per annum worldwide, desalination plants convert 1.7 billion acre feet of ocean water into fresh, drinkable water.
Tell us in the article discussion what you think of this solution to help desalinate sea water for California.