This machine extracts fresh water and electricity from the ocean using a combination of cold ocean water and wind power. Peak Water; What We're Going To Do About It is a general description of this technology. Cold ocean water is pumped through a heat exchanger in the top of a tower. Ambient air ducted through the tower powers a turbine. Condensed water is extracted from the heat exchanger. This blog will go into more detail about unit size versus quantity of water and electricity produced.
This technology is patented. The numbers talked about here are theoretical but give a sound starting point to what can be expected of the real thing. A small prototype would 1. demonstrate that it works and 2. verify the quantities of water and electricity produced. The purpose of this article is to attract interest in this important step.
The ultimate goal is to have enough of these built and working to get back on track for CO2 emission goals and keep our climate from reaching a tipping point beyond which it will be hard to recover. Also, it is important to remember that the world is currently in a fresh water crisis. Fresh water demands were originally projected to grow by 55% between 2000 and 2050. It seems those predictions are holding true.
Here is a picture of the device for handy reference while I talk about it. Click to enlarge or zoom in.
We'll start at the top and work our way down. Because the wind collector is about 300 feet above the ocean's surface the wind is going to blow about 4 mph more on average. The elbow at the top gathers the wind. It is 200 feet tall and 120 feet wide. With the doors open, the wind-gathering area is about 60,000 sq. feet. This wind is squished into the top of the cylinder which has an area of 11,300 sq. feet. That is a ratio of 5.3 to 1. All that air is being scrunched up and forced down a vertical tube. With that ratio a 22 mph wind should become a category 3 hurricane of 117 mph going down this vertical tower. But it doesn't. There's a lot of frictional losses. Some of the air backs up in the collection cone and spills out around the edges. It's a process that is about 50% efficient. The air going into the top of the cylinder is only going 58 mph. It then goes through the heat exchanger. This is specially designed to allow a large throughput of air with as little friction as possible. Even so, it will reduce the air velocity by about 30%. Our 58 mph becomes 41 mph.
As the air leaves the exchanger it is much cooler (55 degrees F) and denser and begins to accelerate down in a reverse stack affect. As it drops the 200 feet to the wind turbine it gains another 15 mph to hit the turbine at 56 mph. Here's the link to input numbers to calculate the stack effect.
We will now calculate the wind power density at the turbine to find out how much energy we can extract. WPD=1/2 density of air x velocity of air cubed. In this case the wind density works out to 19,309 watts per meter squared. Our turbine area is 11,300 ft sq. That converts to 1,050 square meters. The total watts is 1,050 x 19,309 = 20,274,450 watts or 20.2 MW (megawatts).
The math involved in determining how much water will condense out on the heat exchanger is complex and dependent on a lot of variables. But we can look at how much water is available and a realistic percentage of what we can extract.
We know the open area of the heat exchanger and the velocity of air. The area is 11,300 square feet. The velocity is an average of the inlet 58 mph and the outlet 41 mph which is about 50 mph. That's about 3 billion cubic feet per hour.
There are .0094 pounds of water in a pound of air at 60% humidity. A pound of air at 74 degrees will take up about 13 cubic feet of volume. There are 230 million pounds of air going through the heat exchanger per hour. 230x.0094=2.162 so there are approximately 2.2 million pounds of water going through the exchanger per hour. That's 275,000 gallons of water per hour. Let's say we can get only 20 percent efficiency in removing this water. That's 55,000 gallons per hour times 24 equals 1,320,000 gallons of water per day. That's an average. It's nearly half a billion gallons of water per year. Free. It would provide 170,000 households their average daily consumption of 80 gallons per day. If it were bottled and sold to the public at the average price of $1.21 per gallon it would bring in close to $600,000,000 per year. But let's say only a portion was bottled and the rest pumped into the general water supply so that water brought in just $50,000,000 per year.
How much is our electricity worth? The average residential customer payed about 12.5 cents per kwh (kilowatt hour). We're producing about 200,000,000 kwh per year so that's about $22,300,000 dollars per year.
We now have combined revenues of $72,300,000 per year. How much did it cost to get there? Keep in mind this is a much simpler device than an offshore rig; even simpler than a cruise ship. A cruise ship costs about $2.50 a pound to fabricate. Let's figure we can get this built for $2.25. The unit as described above weighs about 7 million pounds. About $16 million. Transportation and anchorage $5 million. Twenty miles of cable and pipe to transport electricity and water at $1 million per mile = $20 million. Miscellaneous expenses of $2 million. That's a total of $43 million.
$72 million minus $43 million leaves $29 million in profit the first year. Second year it will be $72 million minus $2 million in maintenance. Since there are offshore rigs out there over 40 years old, we can assume our simpler structure has at least a 40 year lifespan. The total revenue is $2.8 billion. And that is just one unit. Imagine 200 units in the Gulf of Mexico, 50 on the east coast of Florida and 150 off the south coast of California. Now we're talking a trillion dollar market in the U.S. alone. Think of the Middle East, India, Pakistan, South America, South Africa, and Australia. Another couple of trillion. Per year.
Now you know what I know. A working prototype to pin down the numbers thrown about here would be a great start. If you or anyone you know might be interested in providing fresh water to our kids and their kids, let me know. Engineering skills and money is all it takes.