Potential Uses for Wave-Powered Water Pumps
Several years ago, an Australian company explored the potential of installing wave powered water pumps offshore from the Australian coast. The wave action was intended to activate the pumps that would pump seawater through a tube to water turbines that drove electrical generators located along the coast.
Another application involved the pumps pushing seawater into coastal storage reservoirs located several meters above sea level. During the morning and evening when there was peak demand for electric power, seawater was to flow from the reservoirs and through turbines that drove electrical generators.
The Australian technology was to be anchored to the seafloor with a buoy floating on the surface and activing a pump located under it - except that the market had little interest in an offshore technology that would require frequent maintenance.
In the U.K., Pelamis also developed a mechanical serpent that was a pump that floated on the sea surface. Waves would activate the technology and pump liquid that flowed through a turbine and activated electrical generating technology - except that the market had little interest in a complicated technology that floated offshore.
A professor of engineering in Ireland developed a much simpler technology in the form of a large-diameter hollow tube that could be installed at strategic locations along a wave battered coast. While one end of the tube was partially submerged, the other end extended upward to high elevation at a coastal mountain, with an air turbine and electrical generator at the top. A massive volume of seawater from an incoming wave would enter the tube and push air through the turbine to generate electric power. The receding seawater would pull air downward through the turbine and drive it.
While the Irish technology involves an easily accessible air turbine and electrical generator, it has the propensity to generate electric power during times when there is little or no market demand for power. The high cost of energy storage technology such as batteries presented an obstacle that reduce large-scale market acceptance of the Irish technology.
However, there may be potential to revive the water tube technology as a wave-activated coastal pump that could transfer seawater into a coastal reservoir that could be filled when there is little demand for electric power.
There may be scope to combine the Irish coastal water tube with a much older technology that has been applied at small waterfalls along rivers. The classical ram pump is a sealed tube that may be installed onto a coastal seawater energy tube. It houses a pair of one-way valves or flaps that enables it to pump water to high elevation, as is long proven along rivers. The basis of ram pump operation is a “hammer blow” effect caused by flowing water that enters the pump, to compress air at the top of the tube.
For a large volume of water flowing across a drop in elevation of two feet, a ram pump can push about 10 percent of that water volume to an elevation of over 20 feet. When waves approach the coast, the rise of the seafloor slows the leading edge of each incoming wave and increasing wave height. There may be scope for each coastal tube ton include a pair of ram pumps, one to capture a portion of the incoming wave and the other to capture energy from the receding stream of seawater, with both pumps pushing seawater into storage reservoirs.
Many tourist districts around the world include water fountains that entertain visitors during the hours after sunset, with special lighting effects to enhance the display of the fountains. The Irish coastal water tube showed that seawater pushed by wave energy would accelerate to higher velocity inside a tube of gently decreasing diameter or decreasing cross-sectional area. If the tube is placed horizontally offshore on the sea surface and includes an upward facing outlet, a fountain of wave-propelled seawater could spout from the outlet at high velocity to high elevation and provide entertainment to a viewing audience of tourists.
A compound arrangement of tubes that is free from moving parts could greatly increase the velocity of seawater that enters the tube that will generate the fountain, to produce a spectacular upward surge of seawater. At some locations, the fountain outlet may be located at the center of a pool at a beach where frolicking tourists would be treated to frequent showers of seawater.
The tube technology developed to produce ocean wave-propelled fountains could form the basis of future wave technology that would transfer seawater into coastal reservoirs, even into coastal canals.
Seawater propelled to higher elevation about sea level has a variety of coastal applications that includes peak hour generation of electric power, coastal swimming pools, coastal fish hatcheries and fish farms as well as canals for small pleasure craft such as gondola’s and row boats at a coastal tourist resort.
The offshore wave powered tube technology would assure a regular exchange of seawater that would be essential for all such applications. Developers of future coastal tourist districts could borrow from the precedent of Venice, Italy to build a district that includes small navigable canals.
While using the energy of waves to pump seawater to higher elevation has future application in the electrical generation sector, the tourist sector may provide viable application for such technology to assure the quality of water in and attractiveness of coastal swimming pools, coastal canal zones and coastal water-theme amusement parks. The wave-powered water pumping technology would be especially attractive to operate offshore seawater fountains that would enhance the attractiveness of some coastal tourist areas. It may be more lucrative to develop such pumping technology for applications that are outside of the power generation sector.
The opinions expressed herein are the author's and not necessarily those of The Maritime Executive.