The wave energy conversion field has been a little slow on the uptake, though it’s not for lack of trying. A couple of years ago the US Department of Energy decided to give it a nudge by asking innovators to focus on the narrow task of water desalination, instead of aiming broadly for the onshore electricity grid. The results are in, and they are…interesting!
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Desalination Without Tears
The renewable energy angle is a critical one for desalination and other operations in the energy-water nexus. Aside from the planet-saving feature of using renewables instead of diesel generators and other fossil fuels to run desalination systems, the ability to scavenge renewable resources on site can overcome the logistical and cost obstacles involved in transporting fuel over long distances.
To date, much of the activity has centered on solar powered desalination, but the Energy Department appears to have spotted an opportunity for wave energy to grab a piece of the pie.
“Renewable, wave energy-powered systems could supply clean water to water-scarce, remote, or island communities that are already particularly vulnerable to the effects of climate change. These easily shipped desalination systems may also prove to be a crucial lifeline to support resilience and recovery in the face of worsening natural disasters,” explains the Energy Department’s Principal Deputy Assistant Secretary for Energy Efficiency and Renewable Energy, Kelly Speakes-Backman.
The race for sustainable desalination systems is also of importance as freshwater resources are critical under threat farther inland, due to over-consumption as well as climate change.
Then there’s the military angle. Desalination systems provide seagoing ships with a steady supply of fresh water at sea. A system that runs on renewable energy would relieve part of the fuel supply burden involved in long voyages.
Why Wave Energy?
For those of you new to the topic, wave energy fans have a lot going for them.
Compared to offshore wind turbines, wave energy conversion devices have a low profile on the water’s surface. They are practically invisible from shore and they reduce collision threats to airborne species.
Wave energy converters also generally don’t require a fixed platform or other elaborate infrastructure, and their relatively small size means that transportation and on-site construction costs can be pared to the bone.
Innovators in the field already have the US Navy and US Marine Corps on their side, both of which are interested in stealthy, transportable devices that can harvest renewable resources at offshore sites.
The energy potential of moving ocean water is also alluring. Back in 2013, the Energy Department took a look at the topic and identified as much as 1,400 terawatt-hours per year in the nation’s wave and tidal energy resources combined.
“One terawatt-hour of electricity is enough to power 85,000 homes, and developing a small fraction of the available wave and tidal energy could allow for millions of American homes to be powered with this clean, reliable form of renewable energy resource,” they explained .
Wave Energy Hitches A Ride
Wave energy converters transfer the kinetic energy of waves into an electrical current, which sounds simple enough, but the devil is in the details when you try to float an electro-mechanical device in saltwater for years on end.
In recent years, the wave conversion field has also been outstripped by a huge burst of activity in the offshore wind turbine area.
The competition from offshore wind farms is not necessarily a deal breaker for wave conversion. Offshore wind farms can provide piggyback opportunities for wave devices, which helps to defray sitting and transmission costs.
The emerging field of floating wind turbines is also giving rise to some new variations, such as a hybrid version that includes solar panels as well as wave devices.
The hybrid approach appears to be the winner. Last week the Energy Department announced the winners of its Wave-to-Water desalination competition, and the overall winner was a wave energy device outfittted with solar panels, developed by the Canadian firm Oneka Technologies.
“Grand prize winner Oneka Technologies’ Oneka Snowflake, the Wave-Powered Watermaker, is a circular, raft-like device that can be assembled without tools, is easily installed, adapts to most ocean conditions, and is designed to produce up to 10,000 liters of clean water per week (enough for about 450 people)—making it ideal for disaster and recovery situations,” enthused the Energy Department.
How Does It Work?
Oneka Technologies is holding its energy harvesting technology close to the vest, but its desalination system is similar to other standard reverse-osmosis systems.
The company emphasizes that its device does not require external solar arrays or other sources. Everything is contained within the buoy, included the solar panels.
“The Oneka desalination system does not require external energy, fuel or solar panels; only waves of decent height for the production of drinking water,” the company explains.
“The all-in-one desalination system, totally included in the buoys, is located a few hundred meters from the coast. It does not need land space (with a desalination plant) as it is the case for all other available solutions,” Oneka adds, re-emphasizing that there is no need to construct an onshore solar array.
The land conservation issue is a key point, considering that coastal land is often ecologically if not already dedicated to other activities including tourism and various other industries as well as residential communities.
More & Better Wave Energy Converters
The Energy Department has ramped up its interest in wave energy in recent years. That includes deploying funds through the agency’s ARPA-E office, which focuses on high risk, high reward projects. Earlier this year, for example, ARPA-E tapped the firm Makai Ocean Engineering of Hawaii to develop a new remote-controlled system aimed at making it easier, and less costly, to tether grid-scale arrays of wave energy converters at sea.
The Wave-to-Water competition focused on close-to-commercialization ventures that have already received interest from private investors and other funding sources.
Oneka walked away with the big prize among the four finalists, scoring points for its tool-free assembly system and ease of installation among other features.
The Energy Department also credited the other three finalists — MarkZero Prototypes, Project 816, and Water Bros. Desalination — with significant design and engineering solutions that provide for adaptability and ease of deployment.
The Project 816 team came up with a device called the Ballast, Buoys, and Borrowing From Archimedes System, which refers to a screw-type system for raising water.
“Their device can be by just two people with common equipment, basic tools, and in a variety of site conditions,” enthused the Energy Department’s National Renewable Energy Laboratory in an article last year, noting that the raft-based system is made with commercial, off-the-shelf components.
Project 816 is a team comprised of engineers and test pilots from Edwards Air Force Base, which may sound weird because Edwards is located in the Mojave Desert. However, it’s all for one and one for all in the energy-water nexus, and seagoing aircraft are part and parcel of the modern military.
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Image (cropped): Desalination system powered by wave energy and solar panels, courtesy of Oneka Technologies.
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