The Maine Tidal Energy Project is being run by the Ocean Renewable Power Company (ORPC) and takes advantage of the tremendous energy being generated by tidal water. One of the first places that was tested and trialled was the Bay of Fundy. The Bay of Fundy is located between eastern Maine and Canada and is notable because more than 100 billion tons of water flows in and out each day.
Importantly, for the success of harnessing tidal energy from the water, the tidal range reaches up to 50 feet. The fact that this great movement of water is predictable, consistent and reliable it means there is a real possibility of producing a constant supply of electricity. It simply requires the development and deployment of devices that can effectively and efficiently capture the power of the moving water.
There are a number of different sites in this region that are extremely conducive to exploring the possibilities of capturing the energy produced by these tides.
ORPC Tidal Devices
The means by which the power of the tidal water is captured is with a Turbine Generator Unit (TGU). The ORPC TGU works using the same principles as a wind turbine with rotating foils that power a central permanent magnet generator. So that the components can resist corrosion they are made with composite materials. They are gearless units and this means they don’t require lubricants and won’t emit anything into the surrounding waters.
The TGUs are built into a few different systems that are designed for specific site types. In each case it is possible to stack the TGUs into groups to form larger modules that are capable of generating more power. They are modular and can be configured depending on the size and shape of the surrounding environment. They can also optionally either be moored to the sea floor or tethered to float them at a prescribed depth.
The three different systems that have been developed to date are:
- RivGen Power System
- TidGen Power System
- OCGen Power System.
The RivGen Power System has been developed to generate electricity in smaller river sites that might power remote communities. This device will work well in shallow water situations and can be grouped by the dozen as the situation dictates. The components of the device are small enough to fit inside a shipping container making it possible to easily transport each one to its operating destination. At this stage each RivGen device has a generating capacity of up to 25kW in a 7.5 foot per second (2.25 meters/second) current.
TidGen Power Systems are designed to operate at depths of 50 to 100 feet. They are designed to be used at shallow tidal sites as well as deeper river sites.When these TGUs have been deployed they can be connected directly to an on-shore substation through a single transmission line. This is a larger and more powerful device than the RivGen and each device has an operating capacity of up to 150 kW.
OCGen Power Systems are the largest systems and have been designed for use in water depths of greater than 80 feet. The ability to stack four TGUs together to form a single power generating module gives it greater scope for scaling up. They can be moored to the sea floor or, alternatively, can be tethered by a line. A single site might be populated with any number of these devices, with anywhere from a few to dozens of them capable of making up a single power system. A module that is composed of four TGUs has a maximum generating capacity of up to 600 kW in a 6-knot current.
Tidal Power Is Being Produced
The pilot project using ORPC’s TidGen has been producing tidal power and sending it to the Bangor Hydro electrical utility grid since September 2012. In this case the device was deployed in Cobscook Bay which is to the west of Eastport. Each individual device is capable of generating up to 150kW in a 6-knot current.
The pilot project has been successful in generating consistent electricity and has been removed for annual maintenance and servicing. The project has provided valuable information to the development team while generating enough electricity to power around 25 homes.
It is expected that a further two devices will be deployed in 2014. From that point ORPC will seek permission to deploy a further 18 turbine generators across two sites in the Eastport region over the next five years. All of this will be contingent upon the pertinent licenses being obtained at both the federal and state level.
Tidal Power To Be Produced in the Western Passage
The aim of the company is to move to the Western Passage where it is hoped that a combination of TidGen and OCGen devices will be deployed in the deeper waters.
The OCGen devices will be tethered to the sea floor which is more likely to be irregular in height. By allowing the devices to hang suspended in the water they can be positioned to optimise the harnessing of the tidal currents. They will also be stacked which will achieve the desired scaling of output for even greater power generation.
One of the potential problems with the proposed Western Passage deployment is that this stretch of water, which lies between the peninsula east of Eastport and Deer Island, Canada is a busy commercial fishing lane as well as an active fishery. It is also known to be populated with whales, dolphins and seals.
A prototype mooring system is being developed by the company and will be tested in Cobscook Bay in 2014.
Through the pilot project it has been demonstrated that the technology is compatible with the marine environment. This is according to John Ferland, vice president of project development. University of Maine scientists continue to be involved in the environmental monitoring that is ongoing.
Ferland has also noted that there has been a positive impact to the Eastport economy as well as surrounding communities. ORPC has been able to draw on the skills available from the community but the economic impact extends beyond that. Five people are employed in Eastport with 18 more at its headquarters in Portland. The operations are also responsible for a further 77 positions in Maine through the business that is being done with vendors and suppliers.
So far, the project has invested more than $21 million into the Maine economy.
This particular project is one of the latest tidal power developments that are going through the testing and proving stages around the world. More details about tidal energy and the projects that have been commissioned using it have been detailed on the Tidal Energy page.