By: Kristine Falck
The state of the globe today puts the world’s future in question. We have a burgeoning population heading on 7.4 billion people, an 80% reliance on fossil fuels, and an imminent fresh-water shortage. By 2035, current estimates predict world energy consumption to increase by 50% as well as world water consumption by over 85% (1). What is also of concern, is the fact that over 90% of current energy producing methods are classified as water intense (1). This is alarming, especially in light of the highly interdependent relation between water and energy. In other words, the world is headed for crisis due to these pinnacle challenges. There is immediate need for a shift towards the renewable-energy sector, in addition to a feasible solution to looming water scarcity.
With both an impending fresh water shortage and energy availability predicament, harnessing the world’s ocean tidal power as a source of both power and water for desalination could prove to be of immense value in the near future. With thousands of miles of shoreline around the world that have constant exposure to unharnessed wave energy, the ocean is an untapped source of clean energy. The total estimated ocean power is about 10,480,000 MW, yet only very small amounts of this estimated power are used (about 8000 MW, mainly in France, Canada, Australia, and the US) (2). Capturing this tidal energy could significantly augment global energy production, and diminish reliance on harmful fossil fuels. Since already some 2.8 billion people—a number that is expected to grow to 3.5 billion in the next decade— worldwide suffer from water scarcity, production of clean water is an imminent problem the world must address (1).
THE FOSSIL FUEL STATUS QUO
Not only are fossil fuels leading our demise in climate change, but they also comprise the largest consumption of the fresh water sector. Currently, the US derives 90% of its electricity from thermoelectric power generation plants (1). This in turn account for a staggering 45% of the U.S.’s total water withdrawals including freshwater sources like lakes and rivers, and saline sources, such as oceans and estuaries (3). The majority of these plants rely on what is called “once-through” cooling technology. Essentially, millions of gallons of water are withdrawn daily, before being dumped back at a higher temperature into whatever body of water they were withdrawn from. In addition, the production and refining process of oil requires lots of water (estimated that the US withdraws 2 billion gallons of water each day to refine nearly 800 million gallons of petroleum products like gasoline) (3). Unfortunately, corn-based ethanol, touted as an eco-friendly alternative fuel, is not water-friendly either; 324 gallons of water use are attributed to the production of a single gallon of ethanol, meaning it uses more than gasoline (which requires 3-6 gallons) (4). In essence, the production of both clean water and energy is an increasingly urgent problem.
The large use of water is particularly concerning because fresh water only comprises a mere 2% of the world’s water supply. These concerns have grown because of recent high profile droughts: California experienced its fifth straight drought year, and even British Columbia, Canada, a region blessed with a natural abundance of fresh water, was confronted with a stage 3 drought, drawing attention to the severity of the issue at hand. What can we do to save our dwindling fresh water supply?
With both an impending fresh water shortage and energy availability predicament, harnessing the world’s ocean tidal power as a source of both power and water for desalination, could prove to be of immense value in the near future. Capturing tidal energy could serve to significantly augment global energy production, and diminish reliance on harmful fossil fuels. Despite its availability, tidal power technology is only currently in usage in Perth, Australia. Yet, it is capable of being installed in other highly turbulent tidal coastlines such as Alaska, Washington, California, British Columbia, Scotland, and the Chilean coast.⁵ The ocean is at our disposal as an untapped beacon of energy, and will serve as an important component to our strategy in addressing our global energy crunch.
Since 98% of the world’s water supply is saltwater, it is evident that the desalination of seawater will become instrumental to fulfilling the world’s water needs (9). As John Lienhard, director of the Center for Clean Water and Clean Energy at MIT said, “As coastal cities grow, the value of seawater desalination is going to increase rapidly, and we will see widespread adoption” (6).
DUAL PURPOSE PLANTS
Combining desalination and tidal power solves these problems, and as like everything else in life, it comes down to its economics. By developing a single integrated facility comprising of both a desalination plant and an energy generation facility, significant monetary benefits could be achieved through integrated planning, shared optimized infrastructure, and lower capital costs. Utilizing the high pressurized water already present in tidal energy plants to desalinate water through reverse osmosis, the costs of desalinating water would drop significantly, as nearly 60% of desalination’s high operating costs is due to the creation of the highly pressurized water (7).
Ocean power generators, which capture the energy of waves and tidal motion, have the potential to produce a significant amount of electricity. Carnegie Wave Energy in Australia has designed a technology called CETO, which is able to capture nearly 70% of transmitted tidal energy (7). A coal power plant in comparison is a mere 42% efficient (7). This means these combined plants will also be extremely efficient in their energy conversion– another benefit. The leading edge 3MW CETO 5 technology employs three 36-foot wide steel buoys tethered to the ocean floor (7). When a wave crashes and the buoys bob, the seabed pumps are activated, and water is thrust at high pressure through a subterranean pipe to a power station on land (8). The surging water, in turn, spins hydroelectric turbines that activate a generator, and then undergo desalination through reverse osmosis once leaving the generator (8). Because the water is being forced into the power station at such high pressures, it is also able to be desalinated through reverse osmosis, passing through membranes after leaving the generator (8). The efficiency of this system in converting wave energy to electrical energy can reach over 50 percent and is capable of desalinating 50 billion liters of water each year. Other benefits of CETO’s technology includes the fact that buoys can power themselves at a remote location and support a flexible suite of sensors and equipment for maritime security and monitoring off the grid (7).
Carnegie Wave Energy’s CETO 5 technology is a leader of tidal-desalination combined facilities. Their technology is currently in usage in Perth, Australia, and would be capable of being installed in other highly turbulent tidal coastlines (such as Alaska, Washington, California in the United States; British Columbia, Canada; Scotland, and the Chilean coast) (11). These dual-purpose facilities, which utilize tidal power to create energy as well as desalinate water, will prove to be important facilities in the future. By converting ocean wave energy into zero-emission electricity and desalinated water, this integrated facility will indisputably become an economical solution to the world’s imminent water and renewable energy cruses.
Kristine Falck ’20 is a freshman in Straus Hall.
 United Nations Department of Economic and Social Affairs. http://www. un.org/waterforlifedecade/water_and_ energy.shtml. (accessed Oct. 17, 2016).
 United States Geological Survey. http:// water.usgs.gov/watuse/wupt.html. (accessed Oct. 17, 2016).
 James E. McMahon and Sarah K. Price. Water and Energy Interactions. https:// publications.lbl.gov/islandora/object/ ir%3A158840/datastream/PDF/view. (accessed Oct. 17, 2016).
 Environmental Protection Agency. https://www.epa.gov/sites/production/ files/2015-08/documents/420r10006. pdf. (accessed Oct. 17, 2016).
 Harnessing the Power of Waves – Hemispheres Inflight Magazine. (2015). http://www.hemispheresmagazine. com/2015/06/01/harnessing-the-power-of-waves/ (accessed Oct. 17, 2016).
 California Turns to the Pacific Ocean for Water – MIT Technology Review. (2014). http://www.technologyreview. com/featuredstory/533446/desalination-out-of-desperation/. (accessed Oct. 17, 2016).
 Carnegie Wave Energy – CETO Overview. http://www.carnegiewave.com/ ceto-technology/ceto-overview.html. (accessed Oct. 17, 2016).
 Carnegie’s CETO 5 Operational. http:// http://www.wavehub.co.uk/latest-news/carnegies-ceto-5-operational. (accessed Oct. 17, 2016).
 Desalination using renewable energy sources. Retrieved August 2, 2015, from http://www.sciencedirect.com/science/ article/pii/0011916494000980
 How The Power Of Ocean Waves Could Yield Freshwater With Zero Carbon Emissions. (2013). http://thinkprogress.org/climate/2013/08/30/2554091/ ocean-waves-freshwater/. (accessed Oct. 17, 2016).
 Wave-powered desalination pump permitted in Gulf – CNET. http://www. cnet.com/news/wave-powered-desalination-pump-permitted-in-gulf/. (accessed Oct. 17, 2016).