by Dan Lucky

When I was three years old, maybe four, my parents took the family on an outing, a picnic near a pretty ferocious waterfall somewhere up north. We were near the fall but above it, standing beside the water just close enough to get our feet wet, when I dropped my brand new prized water pistol. No problem. I bent over to pick it up. The moment my mother saw me reach down as it floated out away from us, she yanked me by my shirt, nearly pitching me back on the rocks. I was astonished. Now the gun was even farther away and I tried to break loose to get it before it was too late. Dad took over and I was going nowhere. I could not believe it. The gun was moving farther and farther out, picking up speed, rushing now... and then over it went. My best gun, gone. And all because my parents were absurdly protective, or so I thought until years later when it was my turn to protect others. What my parents understood was the incredible and sometimes frightening power of water. Ask a surfer.

Water in motion is energy. Energy which, when captured, has almost limitless potential. Think of it - for thousands of years people have sought to seize the energy of moving water through the use of water wheels, dams, and other means. Today 70% of all the electricity from renewable energy on earth derives from hydropower. On the other hand, hydropower accounts for only 7% of all the electricity generated in the U.S., an energy thirsty nation. Florida has a particular problem. It is the fourth largest state by population and third in energy consumption. Over 80% of the state's fuel comes from oil, gas, and coal and all of it derives from out-of-state. By 2020 it is projected that Florida's energy demand will increase by 30%, and consumption already exceeds generation during peak demand. Ah, but Florida is a peninsula and peninsulas are mostly surrounded by water and the vast potential for power that water promises.

The energy crisis, the overall economic downturn, threats from climate change - all the conditions are right today for realizing the potential of renewable sources of clean energy. Everyone seems to agree that there is no one answer. Aside from the "re-branding" of conventional sources (i.e., oil, gas, coal), one hears mostly about solar and wind, two promising renewables. Their downsides are known: since the wind does not always blow and the sun does not always shine, energy storage and grid connection issues remain. 

Water power, on the other hand, has many advantages. Current thinking surrounds a whole range of new systems and devices that extract energy from the ocean and from tidal currents. The idea is to work with natural systems without altering in any significant way how they function, resulting in clean, green, renewable energy. The process is sustainable because the ocean, the waves, the tides, and the rivers are reliable and predictable natural phenomena.

Hydropower is such a big topic that most of the plans being studied or implemented (thermal, chemical, wave energy, etc.) cannot be explored here. We will limit the discussion to hydrokinetic energy carried by free flowing water, specifically ocean currents and tidal streams, and the conversion of that energy into electricity. Ocean currents provide a reliable, uninterrupted, continuous flow of water. And as long as the earth rotates on its axis in a gravitational system with the moon and the sun, the tide will come in and will go out.

Axial turbines, which are similar in principle (and even in basic appearance) to modern windmill turbines, are among the most common designs for hydrokinetic conversion devices. Enormous quantities of water are moving in free flowing streams which can be intercepted by axial turbines. The flow of water causes the rotary blades to turn and that kinetic energy is transferred to a generator, which produces electricity. Wind energy turbines rely on very long blades and a spin rate sufficient to produce cost-effective electricity. Since water is 832 times as dense as air, underwater turbines can be substantially smaller (say, 20 feet in diameter as opposed to 120 feet) and use low flow velocity in producing energy. All the same, flow velocity and therefore site selection are important because physics tells us that one current moving twice as fast as another current will produce eight times the energy. Arrayed in fields on the sea or river bed, these turbines should, in the judgment of many experts, operate to produce electricity at costs competitive with conventional energy sources. The hydrokinetic systems in use today are prototypes, still in the research and development phase. None have operated commercially for extended periods. Yet, prospects look promising.

And the potential is real. Consider, for example, the Gulf Stream which flows around Florida's southern shore and up the eastern coast about 20 miles offshore. It flows "with a mass transport greater than 30 times the total freshwater river flow of the world - eight billion gallons per minute."  In practical terms, capturing just one-tenth of one percent of the energy available could supply Florida with 35% of the state's electricity needs. (See the Union of Concerned Scientists website; note #8)

The Roosevelt Island Tidal Energy pilot project, installed by Verdant Power in New York City's East River, placed six turbines on the riverbed in 2006 and 2007. The East River has a powerful tidal stream which changes direction on schedule, allowing these generators to supply all the power needed by a supermarket and parking garage adjacent to the site. Verdant is hoping to be able to install approximately 300 up-scaled units to supply more of the city's energy needs. Several other countries are engaged in meaningful pilot projects around the globe.

In July of this year, as part of the economic stimulus package, the U.S. Treasury and Energy departments announced guidelines offering $3 billion in government funds to provide direct payments to companies developing renewable energy projects. The grants are intended to help meet the goal of doubling U.S. renewable energy production over the next three years and to stimulate job creation. Significantly, as well, in March of this year the Federal Energy Regulatory Commission (FERC) and the Department of the Interior clarified lines of authority, procedures, and permitting regulations concerning the operation of renewable energy projects in offshore waters. For the first time, private companies will now be able to profit from offshore renewable energy.

In the public sector, Florida Atlantic University's Center for Ocean Energy Technology (COET) has benefited from State funding ($5 million in 2006 and $8.75 million in 2008) and a federal grant ($1.2 million in 2009) in developing a National Open Ocean Energy Laboratory that will conduct research and test turbines placed in the Gulf Stream.  Recently, FAU scientists deployed sophisticated equipment off the eastern coast to measure water velocity throughout the water column.

In the private sector, a new company by the name of Hydro Alternative Energy,Inc. (HAE) has been in the planning stages for years awaiting the day when private businesses could become part of the offshore alternative energy revolution its founders anticipate. The company, based in Boca Raton, Florida, recognizes that the state of the technology is still in the research and development phase, but it is determined to become a leader in "harnessing the world's most powerful clean energy." HAE has joined with Parametric Solutions,Inc., out of Jupiter, Florida, an engineering and industrial design firm. The emphasis is on hydrokinetic energy, making use of free flow stream turbines configured to take advantage of tidal currents. In May of 2009 the company announced plans for deploying 250-kilowatt turbines off the coast of a small key in the Florida Keys. When completed, the hydropower system will supply the island with all its electricity. HAE's ultimate goal for the region is to supply the whole of the Florida Keys with power, eventually arraying turbines in the Gulf Stream farther up the Florida coast. The company has its eye on potential sites in the Caribbean as well.

A point of understandable concern is whether or not hydrokinetic systems, such as underwater turbines, are environmentally safe and friendly to fish and other marine life. A lot more research is needed in areas such as the impact on aquatic animal movements and migrations, seabed damage, shoreline disruption, turbine fouling, and the like. A worry to many is just what the effect of these systems might be on fishing, commercial and recreational. Again, there is no real experience to fall back on, but if anecdotal information matters, the fishing community seems sympathetic to the concept of deriving clean energy from the sea in a relatively unobtrusive manner. The risk to fish from free flow turbine blade encounters seems low, judging from what evidence is out there. The blades turn at comparatively low revolutions per minute, consistent with the flow of the current. Fish are not forced into a dangerous environment (as is sometimes the experience with dammed rivers, barrages, and the like). 

It is too early in the process of research and development to say with certainty what the effects on the environment will be in the long run. Every energy generation system is going to impact the environment. Looking at the trade-offs, the current consensus seems to be that hydrokinetic systems can deliver a big plus for the environment. Naturally flowing water in tidal streams and ocean currents is truly a remarkable energy source. Undersea turbines can be designed and maintained not to permit pollutants, and the energy produced will not contribute to global climate change. Turbines are intended to conform to natural water flows with a minimum of impact on habitat. They can be designed to be out of sight at the surface, pleasing boaters and coastal citizens. The conclusions of a recent study on marine energy development potential seem valid: "Given proper care in design, deployment, operation, and maintenance, ocean wave and kinetic stream energy could be two of the most environmentally benign electricity generation technologies yet developed." (See Marine Energy: How Much Development Potential Is There? - Renewable Energy World)

When astronauts first looked back at planet Earth, they remarked in awe about the beauty of the blue planet that we inhabit - 71% of its surface covered in water. How splendid it would be if, at a time of some considerable stress to that planet and the people on it, the power of water played an important role in returning the balance of nature.    

REFERENCES:

The Union of Concerned Scientists, How Hydrokinetic Energy Works | Union of Concerned Scientists  

Roger J. Bedard, Mirko Previsic, and Brian L. Polagye, Marine Energy: How Much Development Potential Is There? - Renewable Energy World

Florida Atlantic University COET website:  FAU Center for Ocean Energy Technology and a related BLOG by Ken Miller in the Palm Beach Post.com:  FAU Begins First Phase of Gulf Stream Energy Project | Extra Credit

The Hydro Alternative Energy, Inc., website:   Clean Power | Hydro Alternative Energy

For government funding of renewable energy:  ttp://www.hydroworld.com/index/display/article-display/3802238872/s-articles/s-hrhrw/s-News/s-u_s_-renewables_cash.html

For the agreement between Interior and FERC: 

http://www.oceanenergycouncil.com/index.php/Worldwide-Ocean-Energy-News/Interior-and-FERC-Announce-Agreement-on-Offshore-Renewable-Energy-Development.html

Peter Asmus,

Hydrokinetic Technologies: Will the U.S. Lose Ocean Energy to Europe? | CleanTechies Blog - CleanTechies.com