Fresh Water From the Ocean Waves
Desalination and energy efficiency often make uncomfortable bedfellows but in the waters of Western Australia, researchers are working on a device which produces fresh water and electricity at the same time. Mike Proffitt, CEO of developers Renewable Energy Holdings, and technical director Alan Burns told edie about their innovative device.
Most people know Fremantle for its cosmopolitan coffee culture and fast ocean racing yachts. But this port of call for many around-the-world yacht races and temporary home of the holy grail of yachting, the America's Cup, has recently seen the winds shift in favour of the waves.
The energy in ocean waves is estimated to be hundreds of times denser than other forms of renewable energy such as wind or solar. It is also the most consistent with 100 percent availability in many locations, is inexhaustible, and consumes no fuel.
The South West coastline of West Australia has some of the world's most powerful wave activity, providing a yearly average energy flux of 78 kilowatts per metre of wavefront. Large areas of the UK coastline also enjoy high rates of between 60 and 70 kilowatts per metre of wavefront.
While wind and solar are growing at around 30 percent per annum, wave power such as the CETO technology has the potential for faster growth and payback periods competitive with coal or gas-fired base load power plants.
This is without considering the co-generation of fresh water from the wave energy plant via the proven reverse osmosis process. This capability makes wave energy even more attractive.
Why Fremantle Western Australia?
London Alternative Investment Market-listed Renewable Energy Holdings, CEO Mike Proffitt said, Western Australia provided top rate geographical siting for the CETO facility and had the right intellectual and research environment too.
"We have CETO I located in the water a few hundred metres offshore from our research laboratory. It's a beautiful scene, right on the edge of the Indian Ocean with the sun setting over those ocean waves. Fremantle Port Authority leased us the seabed and we got the building so here we are, top flight scientists and engineers and the right location," he said.
Brief history and operation
CETO, named after a sea goddess in Greek mythology, owes it genesis to the 'can do' culture of the offshore oil industry. Developed by Alan Burns, the founder and retiring chairman of oil explorer and producer Hardman Resources, CETO is surprisingly simple and robust - always an advantage when dealing with the vagaries and power of natural forces such as the ocean swells.
At the heart of CETO is a simple, elegant, reliable and robust pumping system, which utilises wave energy to generate high pressure saltwater.
This is then piped ashore to drive off-the-shelf reverse osmosis (RO) units that produce fresh water and Pelton turbines that generate electricity.
CETO is the first wave power converter to sit on the seabed, where it is invisible, safe from storms and ocean forces, and self contained.
Unlike other wave energy technologies that require undersea high voltage grids and costly marine qualified plant, CETO requires only a small diameter steel pipe to carry high-pressure seawater ashore. So in the event something does go wrong, the only spillage is seawater.
Although REH technical director Alan Burns has developed the CETO concept since 1975, detailed design of the project commenced in August 2003 with construction of the unit starting in December of the same year.
It took 12 months to manufacture and install all components and following an extensive three month 'dry testing' phase, the CETO unit was launched to sea on 21 March 2005 at Fremantle. During March and April the CETO unit was kept quayside for further testing, concrete ballasting and the installation of computer software.
During the same period, a contract with Fremantle Port Authority was finalised. This provided a lease agreement for the seabed deployment location and pipeline route to on-shore facilities.
These facilities house the computer equipment required for testing and data collection as well a wave test tank, a Pelton electricity turbine and a reverse osmosis freshwater production unit.
On the 4th of May 2005, CETO was towed out to sea and successfully sunk on to the demarcated area on the seabed. Over the next month, 250 cubic meters of sand was pumped into ballast tanks in order to secure the unit in its position.
Following the completion of sand ballasting, 16 scour mats were placed around the unit. Divers have since reported that the scour mats are effective in preventing erosion around the unit. A one in 40 year storm has since been experienced with no significant influence.
A 125 mm internal diameter water pipeline was connected to the CETO pumps as well as two airlines and a fibre optic cable for control and measurement purposes. The unit was then sealed and the inside pressurised.
The CETO unit then immediately pumped seawater successfully on shore. The underlying principles of CETO were thus proven in the very first hour of it operation.
CETO sea trialed for one year
Data collected over the year long trial has been used to develop accurate computer models to determine optimum water pressures under varying wind speeds, direction and sea conditions.
Utilising advanced computational dynamics software used for designing cars and jet airliners, extensive computer modelling has led to the development of a virtual wave tank, which is a useful adjunct to CETO I and its offshore and onshore research facility and test bed.
"This virtual wave tank is one factor that has allowed as to move ahead faster than some players," Mr Burns said.
"Another key issue for us was that we quite shamelessly use a lot of off - the - shelf technology such as sub sea piping and valves from the oil industry and existing top notch Swiss Pelton turbines and reverse osmosis equipment.
"We were not reinventing the wheel, so we were able to focus our efforts on the key system for this form of wave power conversion - a novel, sea water-lubricated, seabed-anchored underwater pump. On CETO I this pump was driven by wave acting on a diaphragm but with CETO II, the pump will be driven by waves acting on a buoy which floats safely just below the water's surface and is connected to the pump by a cable," he said.
The up and down action of the wavefront moves the buoy up and down which drives the pump which in turn forces high pressure saltwater through a pipe 300 metres to shore where the turbine and RO units are based.
CETO II, which is protected by a family of patents, will exhibit a step-change in performance and efficiency compared with CETO I.
CETO II is designed to be deployed in arrays in 20 to 50 metres of water. In this way, the system is very scalable with additional units able to be added at any time.
On the basis of real time data accumulated over 2005-06 from the operation of a CETO I unit located off Fremantle, computer modeling suggests that very promising outputs can be obtained from CETO II units.
The following projections are based on current design parameters, which may change as the project matures and CETO II units would be required to be located at suitable sites - off many areas of the western/southwest UK coastline which is particularly well served by ocean waves or for example off the south west coast of WA.
When producing freshwater and power it is projected that one CETO II unit could produce enough fresh water for up to 3,000 people (about 0.2GL/year), and at the same time enough power for about 40 people. When producing power only it is projected that one CETO II unit could produce enough power for about 100 people (up to 92kW capacity or 0.8GWh/year).
A big advantage of CETO is its ability to produce power or freshwater or a combination of both. The UK, Australia and many other areas now experience water shortages, with water-consuming countries feeling the heat as global warming bites. Sydney is currently planning desalination plants due to water shortages and Perth's plant is due for completion this year.
Perth's desalination plant will produce 45GL/year of freshwater and requires 24MW of electricity to operate.
An array of 225 CETO II units occupying 2.25 hectares of seabed could produce about the same amount of water as the desalination plant.
And there is a big bonus. Not only do the units consumer no power they would generate a surplus of about a third of the power capacity that the traditional desalination plan requires to run.
Eco-friendly to marine life
And it is eco-friendly. In some locations, hyper saline water outfall from desalination plants is shaping up to be a controversial issue, with arguments put that where the water body where discharge occurs is fairly immobile, excess salt concentration in the outfall will be harmful to marine organisms.
CETO is immune from this problem as multiple return pipes from an onshore power and desalination plant, routed back to the wave converter array area, effectively disperse any concentrations of saltier water through wave action and turbulence.
CETO technology, in addition to being greenhouse friendly, does not impact negatively on marine organisms. Indeed the opposite is the case with transects showing that what had previously been a marine desert had actually been transformed, with many plant and animal species provided with a more friendly habitat and thereby attracted to the seabed area surrounding the CETO installation.
Bright future for renewables
Mike Proffitt, chief executive of REH said: "Renewable energy is fast growing in popularity in the face environmental issues, skyrocketing fuel costs and a commitment by governments to encourage alternative energy research and development.
"The current outlook is fantastic for renewables. We envisage that after CETO II, commercial units will be available for deployment within five years. The beauty of these units will be that they will be able to be mass produced and deployed in highly scalable arrays off shore."
REH is surfing the wave of renewable energy with a stake in wind and biofuels. In Germany, the company's 27.9MW Kesfeld wind farm has reached the stage of 'Substantial Completion'. In Wales, REH has completed the acquisition of its Landfill Gas Project, which positions the Company as a ROC trader.
For more information on the CETO device see the REH website at www.reh-plc.com.