According to Pike Research, marine renewable-energy resources are poised for major growth over the next five years and could collectively capture as much as 10 or even 15 percent of the global electricity market by 2030. There is so much potential in marine renewable resources that the federal budget for 2011 includes $40.5 million in new funding in research and development, an increase of $10.5 million over the previous year. The budget includes marine and hydrokinetic (MHK) system testing, MHK device and component design and development, and some feasibility studies for capacity and efficiency upgrades at conventional and nonpowered dams.
So, isn’t electricity generated by water a mature technology that electrical contractors have been involved in for decades? Actually, that is now considered “traditional” hydropower, such as dams and turbines in rivers. This new, renewable and global MHK industry consists of, according to the Department of Energy (DOE), energy-extraction technologies that use the motion of waves; the currents of tides, oceans and rivers; and the thermal gradients present in equatorial oceans. The DOE believes MHK technologies have significant potential to contribute future supplies of clean, cost-effective, renewable energy. In its March 2007 Assessment of Waterpower Potential and Development Needs, the Electric Power Research Institute (EPRI) indicated that MHK power (exclusive of ocean thermal-energy resources) could provide an additional 23,000 megawatts (MW) of capacity by 2025 and nearly 100,000 MW by 2050. More recently, collaborating authors from the University of Washington, the Virginia Tech Advanced Research Institute and EPRI refined earlier estimates and, in 2009, concluded that MHK resources could conservatively yield a total of 51,000 MW of extractable energy. That is the equivalent of 34 conventional coal-fired power plants. That’s a lot of power and a lot of new generating and transmission facilities for electrical contractors to work on.
Wave energy currently represents the largest sector of the national and global MHK industry, according to the DOE. Essentially a derivative of solar energy, wave energy, once created, is steady, predictable and measurable, according to Bill Staby, founder and CEO of Resolute Marine Energy Inc., Boston, an early stage technology company.
There are currently five different ways to harvest wave energy being tested:
• Attenuators, which capture wave energy from the relative motion of their jointed parts as the wave passes along them
• Point absorbers, which capture energy through mechanical motion as they rise and fall with the waves
• Oscillating wave surge converters, which derive power from the back and forth movement of wave surges
• Oscillating water columns, which channel waves into partially submerged hollow chambers and force pressurized air through turbines at high velocities
• Overtopping devices, which funnel waves over the top of the structure into an elevated reservoir and then through a turbine
The technologies designed to capture energy from moving ocean, tidal or river currents represent a smaller sector of the MHK industry but can be considered more mature than wave-energy technologies because of the mechanical similarities the hydrokinetic turbines share with wind turbines.
Generally, current--based technologies can be divided into three categories:
• Axial or horizontal axis turbines, which typically consist of three or more blades mounted on a horizontal shaft that are lifted by the current flow and turn a rotor to drive a mechanical generator
• Cross flow turbines, which have two or three blades mounted along a vertical shaft and are designed to extract multidirectional flows without the need to orient to the flow’s direction
• Reciprocating devices that generate electricity through an oscillating motion caused by the lift and drag forces of the water stream
“The foremost advantage of ocean energy is a potential for costs that are competitive or lower than that of other renewable technologies,” said Roger Bedard, former EPRI ocean energy leader.
EPRI studies indicate that the higher power density of MHK resources result in smaller and stronger energy conversion machines that are lower in capital cost than other renewable technologies.
“The remoteness and, at times, hostility of the ocean environment results in higher deployment, operation and maintenance costs. On balance, however, the cost of electricity is still comparable or lower than that of other renewable technologies,” he said.
Permitting the future
As of July 2009, the Federal Energy Regulatory Commission (FERC) had issued 146 preliminary permits for hydrokinetic generation projects with a total project generation capacity of more than 9,000 MW. Preliminary permits allow feasibility studies but not permanent or large-scale installations. Development of MHK projects has already reached the early commercial stage in other countries, particularly Portugal, Great Britain, Ireland and Scotland. For research and development projects in the United States, the areas known to have good wave energy potential include most of the continental West Coast, Hawaii and Alaska. Good sites exist in the Puget Sound and San Francisco for tidal energy projects, and for river hydrokinetic energy, the Mississippi, Missouri and Yukon rivers hold promising potential.
“Ocean current technology is a huge resource, but on the East Coast, it is primarily limited to the Gulf Stream off of Miami,” Bedard said. Basically, he said, the waves are just travelling the wrong way.
The primary mechanism that the DOE uses to support MHK research and development is private and public partnerships, which are essentially cost sharing grants, with technology and project developers.
“Developers are working on everything from researching specific devices or components to supporting utilities or other organizations that are ready to deploy and test systems,” said Alejandro Moreno, program manager for DOE’s Hydro Power Technologies Program.
“Preliminary results indicate MHK to be a substantial resource. The DOE is trying to assess and define that resource, its potential costs and the potential cost reductions of the different technologies,” Moreno said.
Research projects underway
Currently, several projects are underway or planned. The two largest U.S. demonstration projects to date are Hydro Green’s 250 kW capacity Hastings projects in Minnesota and Verdant Power’s 200 kW Roosevelt Island Tidal Energy Project (RITE) in the East River in New York City, which stands as the world’s first grid-connected array of tidal turbines.
Two of the key tidal projects that are hoping to connect to the grid over the next few years are in Washington state’s Puget Sound. The U.S. Navy is managing one and the other is with the Snohomish County Public Utility District in conjunction with OpenHydro, an Irish technology company, to design, build and install up to three marine turbines at a tidal energy pilot plant in Admiralty Inlet, west of Whidbey Island.
Also, Wave Connect, a pilot project by Pacific Gas & Electric, the largest investor-owned utility in the country, will provide wave energy converter manufacturers the opportunity to test their devices on a common site in an effort to determine the most effective technologies for future ocean wave energy projects.
In December 2009, Ocean Power Technologies Inc., Pennington, N.J., launched a wave energy device about a mile offshore the island of Oahu in Hawaii. The device generates up to 40 kilowatts of power from the rise and fall of the waves and, since its deployment, it has been generating power within specifications. And finally, Ocean Renewable Power Co., Portland, Maine, became the first company to generate tidal electricity in the Bay of Fundy without the use of dams in 2008. The company also has MHK technology projects ongoing in Alaska’s Tanana River and Cook Inlet.
Although all these projects demonstrate a great deal of progress in MHK research and development, there are no full scale or marine or hydrokinetic devices in the water that are connected to the grid at this time, Moreno said.
Hydro and MHK
Conventional hydropower generation, which uses elevation differentials to allow falling water to turn turbines, accounts for up to 10 percent of the nation’s supply of electricity. Although integration with MHK technology is an area that has not yet been researched, some suppose that the two could work together. Bedard offered that conventional hydropower, with its ability to generate electricity upon demand, could fill in during those times when tidal forces are slack and not generating electricity or when seas are calm and there is no wave energy to harness.
Another opportunity for the two technologies to work together, according to Greg Allen, director of environmental and engineering services for Alden Research Laboratory, Holden, Mass., is on the downstream side of a dam.
“When appropriately placed on the exit side of a conventional hydro project, a MHK installation could take natural advantage of water exit speeds that are on the order of two meters per second,” Allen said.
Because hydrokinetic power generation does not require the construction of a dam, it may have less impact on the environment. However, the uncertainty about the extent of the environmental impacts and the recognition that impacts will vary with specific technology and site characteristics means the data from demonstration and pilot projects currently in operation are vital in reducing obstacles to further development of the MHK industry and its opportunities for electrical contractors.
With their expertise in conventional power generation and the recent opening of other renewable-energy markets such as solar and wind, electrical contractors are in an excellent position to work in this new realm. According to Staby, electrical contractors’ expertise in designing and installing power conditioning equipment, laying high-voltage cable, and their knowledge of all the electrical work required for a successful power generation project is vital.
“There will be a huge amount of work for those contractors that learn how to operate in a marine environment and that can demonstrate that expertise to the up and coming marine energy project developers,” he said.
BREMER, a freelance writer based in Solomons, Md., contributes frequently to ELECTRICAL CONTRACTOR. She can be reached at 410.394.6966 and firstname.lastname@example.org.