The Pros and Cons of Tidal In-Stream GeneratorsBY: PATRICK SMITH and NICHOLAS ALBANESE

WHAT IS A TIDAL IN-STREAM GENERATOR?

A tidal in-stream generator works very similarly to how a wind turbine works. The spinning apparatus is mounted to a generator which is connected to the seabed. The current flows through the blades of the turbine, creating energy to spin the generator, which converts the energy to electrical energy. The energy is then distributed through a power grid to locations on land. In comparison to wind energy, the density of water is approximately 800 times greater than the density of air which makes tidal energy so powerful. The key to creating a successful tidal power generator relies on specific propeller designs along with accurate electrical conversions within the generator to effectively harness all possible energy in a cost efficient manner.

LOCATIONTidal in stream generators cannot be placed just anywhere. There have to be certain conditions met by the location for the generators to be cost efficient. The turbines are most efficient in a location where currents are fast forced from a large volume (such as an ocean) into a much smaller space. Inlets into bays, areas between islands or other landmasses, entrance points to rivers, and headlands are the most ideal locations. However, just because one of these formations exists does not mean that it is guaranteed to be a location where tidal in stream generators will be efficient.

INNOVATIONSThere are a few major themes to all of the innovations currently being tested. Everyone is trying to make a simple turbine that generates the most amount of electricity with the least amount of environmental impact. Many different companies are testing their own different solutions around the world. Below are some examples of current innovations that are being tested and implemented.

VERDANT POWERVerdant Power is a company based out of New York City that solely deals with tidal energy. Their new Generation 5 axial turbine has made some serious steps in the way of making these turbines more environmentally friendly and efficient. They have stated that they have made innovations like nontoxic paint that will not hurt the environment if it is corroded off, more efficient gearboxes and shaft arrangements, and a better seal from the harsh seawater which proves that this up-and-coming technology can produce large amounts of electricity with little to no impact on the marine environment. FLUMILL

This Norwegian company has made great strides using a cross flow turbine design with significant advances over other versions. Flumill’s new turbine uses a screw made of composite material that will not corrode and is much cheaper than any non-corroding metal counterpart. This polyester will not release any of its plastic into the water, making it just as environmentally friendly as its metal counterparts.

OPEN HYDROOpen Hydro is a British company that believes they have found the most efficient turbine design with the least amount of impact on the environment. They use a flow augmenting design that has an open center with the blades only connected to the tube they sit in. Each turbine has a generator in its ring. Using the power output they received from their prototypes, they have also calculate a possible capitalization of just about $25 billion per year.

POWER OUTPUT AND COSTAt the current output, Nick Yates, an expert in tidal energy, predicts that fifteen percent of the world’s power can be extracted from tidal in-stream generators. Given the increasingly energy dependent world we live in, this amount of energy could be a huge contribution to the solution for depleting fossil fuels sources. Yates predicts that between 500 and 1000 terawatt hours of energy is the maximum amount we can harness from the seas per year. Some examples of tidal instream generators and their power output are listed in the chart above. The cost of developing tidal in-stream turbines was very high when the concept was first implemented. Recent innovation, however, has given companies the opportunity to improve their designs and lower costs of implementation like Triton, a company that develops wind turbines as well as tidal in-stream turbines. They were able to cut the cost of implementation in half.

SUSTAINABILITYThe goal of implementing tidal in-stream generators is to increase energy efficiency in order to cut the cost of electricity while using a renewable source of energy that decreases harmful environmental impacts. The Environmental Protection Agency (EPA) states that sustainability “creates and maintains the conditions under which humans and nature can exist in productive harmony, that permit fulfilling the social, economic and other requirements of present and future generations.” Tidal in-stream generators are designed to co-exist with the marine environment, and therefore will have no interference with the spontaneity of our planet. The energy harnessed by tidal in-stream generators is entirely a product of our environment. There is no need to be concerned about balancing our quality of life with nature. The two will naturally exist in harmony and both quality of life and environmental friendliness will see improvement.