Wave-powered desalination pump permitted in Gulf

The Seadog water pump, which captures the energy of waves to turn a generator, will be used on an offshore platform in Texas to test using ocean power to desalinate water.

The waters of the Gulf of Mexico will see a novel offshore platform later this year, one that will use wave power to desalinate water.

Independent Natural Resources, which makes the Seadog water pump, on Wednesday said that it has received a permit for a wave power generation facility off the coast of Freeport, Texas. The company says it's the first to receive a "section 10 permit" from the U.S. Army Corps of Engineers to operate a wave generator in the U.S.

A picture of the planned offshore platform which would have underwater 18 pumps moving water through a water wheel to make electricity. Independent Natural Resources

The facility, which the company hopes to put in the water by the end of the year, will be a platform with 18 wave pumps underneath it. Each pump, which is about seven feet in diameter, will send water up through three water wheels connected to a generator. The electricity from the generator will be used to power a standard reverse osmosis desalination machine.

The wave energy generator is larger than Independent Natural Resource's prototype machines which it installed in 2007 but this new facility is sized to operate at commercial scale in Gulf waters. Rather than sell electricity or water, though, operators will be taking data to measure impact on sea life, the generator's performance, and the cost of operation, said Douglas Sandberg, the vice president of the privately funded company.

The platform will be about 150 feet by 75 feet in area and be 1 mile offshore to take advantage of swells. The pumps themselves will work 25 feet below the surface of the water and be able to generate about 60 kilowatts.

The efficiency of the system in converting wave energy to electrical energy is about 22 percent but can get over 50 percent, Sandberg said. Rather than only convert the energy of an incoming wave, the pump also captures some of the potential energy of air movement in the pump, he explained. The electricity generated on board will be used to power the facility and desalinate 3,000 gallons of water a day for testing, although it's capable of doing 20 times that, according to the company.

Water energy connection
The company chose to work on desalination because the energy costs associated with running desalination plants are very high--as much as 40 percent or 50 percent of operating costs, according to Sandberg. It has set up a subsidiary to bottle water from Seadog pumps from future installations. But the technology can be used for municipal-scale desalination.

"Instead of having to build power plants to do desalination, we can build one facility that produces power, desalinates water, and delivers it, either for agriculture or drinking," he said. "You do have upfront capital cots but you do not have operating power costs."

A prototype of the Seadog pump being installed in the Gulf of Mexico in 2007. Independent Natural Resources

The pump can be used with different types of generators, including a standard water-powered turbine. The company has a permit to operate for four years, during which it hopes to prove that the environmental impact is minimal. In areas with a good wave resource such as Ireland, Sandberg said the Seadog pumps can be competitive with wind power and "in line" with fossil fuel power generation.

Ocean power generators that take advantage of wave motion or currents have potential to produce a significant amount of electricity, but the technology faces a number of challenges. Generally, these machines are put in harsh conditions, making maintenance--and cost--a big concern. Also, there's a long permitting process as data needs to be gathered on the environmental impact.

Still, there are a number of companies and researchers pushing ahead on wave or tidal power. Late last year, Aquamarine Power connected a giant, clamshell-shaped device that pumps water from off the coast of Scotland to a water generator. Last week, the company unveiled its second-generation machine, which it hopes to have installed off the Orkney Islands in mid 2011.

Updated at 11:30 a.m. PT with additional details and clarifications.

 

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