at windmills in the Big Apple underwater
Imagine a field of windmills generating clean renewable electricity. Now put that field underwater: The blades rotate a bit slower because water is denser than air, fish instead of birds maneuver through and around them, and theyre virtually invisible from shore.
By 2007, Verdant Power hopes to be able to supply power to residents and businesses on Roosevelt Island in New Yorks East River through turbines that will generate electricity by rotating below the surface of the river. The turbine blades will be about 5 meters in diameter atop a unit that is affixed to bedrock below the tidally controlled river. They will rotate at maximum speeds of 32 to 38 rotations per minute. Courtesy of Verdant Power.
Such a system is precisely what a startup energy company has dreamed up and begun testing in the East River in New York City. By 2007, Virginia-based Verdant Power hopes to be able to supply around 10 megawatts of power to the city. Although New York City uses 1,000 times that amount of power, Verdants underwater turbines will be a good start to turning the city green, says Trey Taylor, the companys president.
Any place there is a water current waves, tides, rivers, aqueducts and so on an underwater turbine could be used to produce clean electricity, Taylor says. The East River tidal currents operate at a pretty good speed of 4 knots, he says, so it is a good location to test this new technology.
Several different prototypes of underwater turbines have been developed, including one that looks like a double-helix DNA strand, but Verdant is focusing on one that looks like a submerged propeller stuck on a pole (like a windmill) attached to the river bottom. They have tested blunt-edged rotor blades that are about 3 and 5 meters long, and rotate at a maximum speed of 32 to 38 rotations per minute (rpm). (Traditional hydropower turbines generally rotate around 600 to 700 rpm.) The turbines are also designed to automatically rotate to face the tides as they come in or go out to generate the most possible energy. Furthermore, each individual turbine is designed to operate independently, Taylor says, so if a submerged car or log floats into and damages the rotating blades, a single turbine can be swapped out for maintenance with no loss of power production, whereas when traditional power sources need maintenance, power generation stops.
The turbine field will provide power directly to consumers nearby, rather than going through already overtaxed electricity grids, Taylor says. Based in the eastern channel of the East River that separates Manhattan from Brooklyn and Queens, the projects aim is to generate power for the 10,000 inhabitants on Roosevelt Island. (Most of the rivers commercial boat traffic travels via the western channel, so the project will not affect shipping, Taylor says.)
In September, Verdant will install two turbines into the water that can each produce 35 kilowatts of power. If all goes well, they will install four more turbines on the river bottom in October. Verdant will then monitor fish movement, behavior and any impacts on the environment, as part of an 18-month study involving many partners, including the New York State Department of Environmental Conservation, U.S. Army Corps of Engineers and New York State Energy Research and Development Authority.
The turbine array will be about 24 meters wide for scale, the eastern channel of the East River is 206 meters wide, Taylor says and 91 meters long. The turbines will be spaced about 12 meters apart widthwise and close to 30 meters apart in length, so fish should have plenty of space to roam, while avoiding the turbines, he says. The turbines will be mounted on 0.6-meter-diameter platforms that will be drilled into the bedrock on the river floor. The tops of the turbines, during mean low tide, will be at least 2 meters underwater: From the shoreline, nothing will be visible except buoys bobbing on the water marking the edge of the turbine field.
Each individual turbine will be connected to a land-based control room, Taylor says, so if there is a problem, we can just shut down the turbine. If tests go well, he says, Verdant will file for an operating license from the Federal Energy Regulatory Commission. The eventual goal is a field of 200 to 300 turbines, Taylor says, which would cost around $20 million to get online. A field of this size could save New York the equivalent of 68,000 barrels of oil a year and reduce the annual carbon dioxide emissions by about 33,000 tons, he says.
Our national security is very closely tied to our energy supply, says Sean ONeill, executive director of the Ocean Renewable Energy Coalition in Maryland. Indeed, says his colleague Carolyn Elefant, we can leave no rock unturned in diversifying and finding new energy sources. Ocean-based renewable energy like the Verdant project is just the sort of diversification thats needed, they say.
Elefant cautions, however, that tidal turbines and the other ocean technologies for example, those that capture energy from waves, currents or cooler water at depth are nascent technologies that will take a few years to develop, as did wind energy. In 1978, the price of wind power was 25 cents per kilowatt hour, ONeill says, and now its down to less than 7 cents per kilowatt-hour. We learned a lot from the wind industry, he says.
At 7 to 10 cents per kilowatt-hour, underwater turbine power is already starting out much better. Still, because turbine power is an emerging industry, no one can really pinpoint how much everything is going to cost, Taylor says. Its a question were all trying to figure out together.
There is tremendous potential for emerging hydropower technologies, says Mike Bahleda, an energy consultant with Bahleda Management and Consulting in Alexandria, Va., but we in the United States arent doing much to develop it. Grant money is scarce and the federal government has provided few, if any, tax incentives for ocean energy prototype projects. Because few entrepreneurs have the capital to start a project like Verdants turbine project, the government needs to provide research and development funds in addition to production tax credits and incentives. Other-wise, Bahleda says, U.S. companies will move to Europe, where governments are providing funding and support for such projects. The other major impediment to new renewable projects is the cumbersome regulatory process, ONeill says. Verdant, for example, has worked with more than 80 different agencies and organizations to get this project off the ground.
The possibility for doing similar projects across the United States is immense, Taylor says, but the United States is actually the smallest market. The biggest possible market for this type of energy, he says, is developing countries. Turbine systems are relatively inexpensive, and it would be easy, he says, to send a turbine to Brazil, for example, to supply electricity to a small rainforest village.
New York is sort of like our flight at Kitty Hawk there are still a lot of changes on the horizon before you see the final airplane, Taylor says.
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the big chill in Hawaii
For more than 20 years, Joe Van Ryzin has been seeking to exploit a precious natural resource: cold water. His companys pipelines now crisscross waters in several of the worlds oceans and lakes, drawing water from great depths for everything from purified and bottled seawater (now a hot commodity in the Far East) to a medium for growing shellfish. But the seawater application Van Ryzin is most excited to see develop is something everyone can relate to, especially in the summertime providing a clean and renewable source of air conditioning. And his companys sights are now set on Honolulu and the vast seawater along its shores.
Downtown Honolulu will soon draw its air conditioning power from deep seawater located offshore of its famed beaches. Courtesy of Honolulu Seawater Air Conditioning.
Most air conditioning systems circulate cold water that is cooled with refrigeration-based chillers. As homeowners and developers know, generating the electricity to fuel these systems can be quite costly. And with energy costs on the rise, alternative solutions are becoming increasingly popular.
That was also the case in the 1970s and early 1980s when the United States was facing an energy crisis. It was then that Van Ryzins company Makai Ocean Engineering, a small company based in Oahu, was called in to help. The federal government and the state of Hawaii both were interested in developing technology that would extract energy from the difference in temperature between cold deep and warm surface seawater.
So with funds from the state and federal government, Makai built deepwater pipe-lines the first of their kind to pump water to the surface for use at the Natural Energy Laboratory of Hawaii Authority. Ultimately, the facility became a place for anyone who wanted to conduct research experiments using deep seawater, whether for aquaculture or electricity.
The lab used a unique cooling system that was to become the landmark project for Makai and others interested in deepwater cooling. The building has an air conditioning system internally identical to conventional systems, but instead of using chillers to cool the water, cold seawater from the underwater pipelines passes through a heat exchanger that is also in contact with the freshwater from the buildings; the two waters do not mix. After chilling the freshwater, the now slightly warmer seawater returns to the ocean at a shallower depth.
Around the same time the labs cooling system was developed, Purdys Wharf in Halifax, Nova Scotia, came online as the first commercial building to utilize deep seawater for such a system in North America. Several years later in 1995, Stockholm, Sweden, independently developed a municipal deepwater cooling system. And other places started to follow, in some cases calling on Makai after recognizing their own, sometimes fresh, deepwater as a resource such as Toronto, which just launched a municipal cooling system using Lake Ontarios water, and Cornell University in Ithaca, N.Y., whose buildings have been using Cayuga Lakes deepwater for air conditioning since 2000.
The Honolulu project, developed and headed up by Honolulu Seawater Air Conditioning, whose parent company is Market Street Energy based in St. Paul, Minn., will cool the downtown areas buildings through a centralized system that draws on seawater located about half of a kilometer (1,600 feet) deep. Here is this city sitting within a few miles of an infinite source of water thats as cold if not colder than what theyre using [for air conditioning], so it makes sense, Van Ryzin says. The 20,000 to 25,000 tons (1 ton equals 4.7 horsepower or 200 BTU/minute; see box, page 21) of air conditioning circulating through the system will not provide the whole demand for air conditioning for downtown because not all potential customers will sign up immediately, he says. The system, however, will serve an area from the shores of downtown Honolulu to about 1 mile inland.
Cornells project, which saves the university 85 percent on energy purchases, and the seawater project are quite similar, says W.S. Lanny Joyce of the Cornell Lake Source Cooling project (see Geotimes, July 2002). The only difference, he says, is salt. Both systems use noncontact cooling, with a heat exchanger separating the natural body of water from the closed loop thats cooling the building.
The Honolulu project does pose some unique challenges, however. In designing the system, Van Ryzins team has had to find a way to not disturb both the marine and urban environments, and to also protect the pipeline itself. The problem is usually at the shoreline, where youre trying to both protect your pipelines from very large waves, which Honolulu could get with hurricanes, and at the same time, youre trying to protect the reef and the environment and the aesthetics of the area, Van Ryzin says.
To get around the city and the coral, Makai plans to tunnel from a pump station on shore to the shoreline, and then from the shoreline out to a depth of approximately 12 meters (40 feet) in the ocean. The tunnel will take the pipelines under the reef itself, protecting the delicate ecosystem.
Another challenge the Hawaii project faces is that the water at depth is not as cold as it needs to be because of the underwater topography offshore Honolulu. The island [Oahu] drops down and gets deeper, and then it starts going back up again toward Molokai, which is the next island over, Van Ryzin says. So theres a kind of saddle between the island, and Honolulu is located in the mid-part of that saddle. If the project were on another portion of the island, he says, the water would go deeper and would be colder.
As the water is not cold enough on its own, the system will need to include auxiliary chillers to get the naturally 45 degree Fahrenheit water to 43 degrees. The deep seawater will take care of 75 to 80 percent of the cooling load, as opposed to the Cornell project, for example, where Cayuga Lakes cool waters take on 100 percent of the cooling load.
Still, once the Honolulu system is online, which is expected to be in mid-2007, it will reduce energy use by 75 to 85 percent, Van Ryzin says. Thats huge, Joyce says, for an area with such a high cooling load. Every day is the same, with the sunlight the only difference between day and night, so the cooling load is very uniform, he says.
The energy savings for downtown Honolulu, Van Ryzin says, will amount to reducing imported fossil fuels by 145,000 barrels a year, and a reduction in all emissions associated with burning oil, including carbon dioxide. The total estimated cost for the project is $100 million. That cost, Van Ryzin points out, is almost entirely capital. The real payoff is in stable prices for future energy needs, he says. The major attraction of the seawater air conditioning is that you come today and offer them a fixed price for air conditioning needs, and the escalation of that cost is going to be really minimal into the far future.
Joyce, however, also sees the large capital cost as a possible reason why the technology has not been as widespread. Even though its really successful, it has a long payback versus the alternative chillers, which would have been much cheaper to build and involve much less involvement with the community and local natural environment, he says.
Indeed for the now five-year-old Cornell project, the Ithaca community has been outspoken in its concerns about the cooling disturbing the lakes ecosystem. The biggest concern was that returning warmer water to the surface of the lake could fuel algal blooms. The university has been continuously monitoring the lake and, Joyce says, has seen no adverse affects.
For the Honolulu project, bringing nutrients to the surface with the deep seawater is not a major concern, Van Ryzin says, because the Pacific Ocean is so large, and the water will be returning to it in the mixing zone via diffusers. He sees the project as a win-win for everyone. For a community like Honolulu, you can build a seawater air conditioning system that will provide your air conditioning load at costs that are either comparable or slightly less than what youre paying today, and its environmentally friendly, he says. To not do it, I think, is criminal.
Next, Makai plans to try to develop seawater air conditioning in Guam, where the tourism industry has been booming. Because of its far southerly latitude, the climate is a lot warmer and the air conditioning is used at the maximum all the time. And theyve got really great access to deep, cold seawater, just a little over 2 miles offshore, he says, so I am quite optimistic on that.
Lisa M. Pinsker
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greening a museum
The Museum of the Earth in Ithaca, N.Y., educates visitors not only about the history of Earth, but also about how the planet can be used as a source of clean energy. The museums building, completed in 2003, uses a geothermal exchange system that takes advantage of the near-constant temperature of the planet to both heat and cool the nearly half-an-acre structure.
The new Museum of the Earth in Ithaca, N.Y., is a green building, fueled by fluids drawn from deep beneath the planets surface. Courtesy of Paul Warchol.
The museum is part of the growing trend of green building designing and building structures to maximize energy efficiency and minimize environmental impact. The environmental responsibility of green building complements the museums mission, says Bridget Rigas-Gangi, associate director of Cornell Universitys Paleontological Research Institution, which runs the Museum of the Earth. What better way to heat a museum about the Earth, she adds, than with the Earth.
The geothermal system, or geoexchange system, pumps heat-absorbing water through the building and deep into wells beneath the museums plaza. In a process similar to refrigeration, the system draws heat from the building in the summer and carries it about 470 meters (1,550 feet) underground to be absorbed by the bedrock. In the winter, the process is reversed, absorbing and concentrating Earths heat to warm the building.
Although the system was fully operational when it was installed, it has since experienced some failures. We are hoping to have additional well-design modifications that will bring the system back to full capacity, Rigas-Gangi says. It seems that a major problem is that the wells werent designed well for our local bedrock geology; and therefore the system may be fixed with special well-casing adjustments and some equipment replacement.
When at full capacity, the system saves the museum an estimated 90,000 kilowatt-hours annually in electricity over other types of heating systems that could have been installed. In general, geoexchange systems are 50 to 70 percent more efficient than other heating systems and 20 to 40 percent more efficient than air conditioners. Additionally, the electricity the museum uses to run the compressors and exchangers is generated by wind power through the Catch the Wind program at New York State Electric and Gas. The museums objective is to be 100 percent green, Rigas-Gangi says.
In addition to conserving electricity, the museums energy systems may be helping to mitigate climate change, a lesser-known benefit of green building. According to the U.S. Environmental Protection Agency, the advantages of geoexchange systems include not only reduced energy costs but also reduced emissions of greenhouse gases and other pollutants. The institute hopes that the museums system, when fully operational, will prevent up to 67 tons of carbon dioxide from being emitted into the atmosphere each year.
In June 2005, the Pew Center on Global Climate Change called for changes to long-term climate change policy in order to specifically address emissions from the U.S. building and electricity sectors, which account for 50 percent of the nations carbon dioxide emissions.
Many people dont realize it, but buildings, both in their construction and their operation, use as much as 40 percent of our energy resources, says Gwyn Jones, communications services manager for the U.S. Green Building Council in Washington, D.C., a 6,000-member coalition of corporations, builders, universities, government agencies and nonprofit organizations founded in 1993 to promote sustainable design. So if we can minimize their impact, we can make a huge impact on the environment, Jones says.
Since 2000, the council has maintained the Leadership in Energy and Environ-mental Design Green Building Rating System, or LEED, which measures how green a building is. A green building could include the following: choosing a building site that is near public transportation; selecting energy-efficient building materials; installing low-flow toilets to conserve water; using native plants that require less water; and using skylights and motion-sensors on lights to save electricity. Its about treading lightly on the Earth, Jones says. Its a holistic view of how the building interacts with its environment.
And although green building is on the rise, with 231 commercial buildings already LEED-certified and another 2,000 registered for the certification process, there are still challenges. There is a perception that it is more expensive to build a green building, Jones says. However, while first costs may be slightly more, you can actually do a fairly highly rated building under our system and reap incredible returns in future operations. For example, a minimal investment in green design, adding less than 2 percent to a buildings construction costs, could reduce water use by 40 percent, energy use by 30 percent, and divert 50 to 75 percent of construction and demolition waste away from landfills, Jones says.
Green building practices have been credited in recent studies with improving employee performance, attendance and health, mainly by combating poor indoor air quality. Educating the building industry about the benefits of green building is one of the councils main goals. If you build green, it not only benefits the environment, it also benefits the occupants, and it helps the owners bottom line by being more efficient with a lower cost to maintain the infrastructure, Jones says.
Educating the public about environmental choices is also a goal at the Museum of the Earth, where an interpretive exhibit is being developed on the geoexchange system itself, as well as other energy alternatives. The exhibit, expected to open next year, will allow visitors to view the inner workings of the systems mechanics through windows that were part of the buildings original design.
crop in Iowa
Surrounded by acres and acres of farmland, the school district of Eldora and New Providence, Iowa, is harvesting a different kind of crop: wind-generated electricity.
After a principal from one of the districts schools attended a workshop run by the Iowa Energy Center, the districts superintendent Bill Grove (now retired) says he decided it was worth pursuing. Built in 2002, the wind turbine now produces more than 1 million kilowatt-hours a year, enough to supply the school districts energy needs throughout the year and more.
The Eldora-New Providence School District in Iowa built a 750-kilowatt wind turbine on its high school campus, which will eventually pay for itself by providing all the districts energy needs and more. Courtesy of the Eldora-New Providence School District.
It turns out that schools are a very good fit for wind energy, says Keith Kutz of the Iowa Energy Center, which is affiliated with Iowa State University in Ames. School energy loads are concentrated, as they are in session the nine months of the year that happen to coincide with high-wind months, Kutz says, which is different from most industries or homes where the need is spread out more evenly throughout the year.
In addition to eight Iowa school districts that have put up wind towers, farmers in Iowa and elsewhere have leased their land to power companies who have made it a priority to add wind-generated electricity to their portfolios, prompted by state and federal incentives and emissions-free energy. Northwestern Iowa is about to be the site of a 200-plus-tower wind farm, built by MidAmerican Energy, with an expected generating capacity of 350 megawatts.
Wind has always blown across Iowa, but not until the early 1990s did the state decide to subsidize wind power through a series of tax incentives and grant programs under its Department of Natural Resources. The American Wind Energy Association in Washington, D.C., now ranks Iowa third in the United States for total electricity generated by wind, after California and Texas.
On average, the wind blows across the Midwestern state at 21 to 29 kilometers per hour (13 to 18 miles per hour), at 50 meters (about 160 feet) aboveground (the height of a typical 750-kilowatt wind turbine tower), according to data from the Iowa Energy Center. A region with less than 13-mile-per-hour wind speeds may be less cost-effective, says Brian Parsons of the National Renewable Energy Laboratory in Golden, Colo. The difference of 1-mile-per-hour wind speed on an annual basis is huge, he says, because the energy in wind is proportional to the cube of its speed. Double the wind speed, and theoretical potential output goes up by a factor of eight.
Economies of scale also come into play for the size of a turbine and its diameter. The area of the circle described by the blades determines how much energy a turbine can capture; doubling the length of a blade increases the energy collected by a factor of four, Parsons says.
Standing at 50 meters, the Eldora-New Providence wind tower supports a 750-kilowatt generator and blades that are 25 meters (80 feet) long. Giant wind-power towers can be a football-field across in diameter, Parsons says, the biggest of which push the production envelope to 5 megawatts (seven and a half times the power of Eldora-New Providences turbine) and which tend to sit offshore.
Such wind installations in the North Sea already provide energy to Denmark, for example, at 3,000 megawatts or 20 percent of the countrys energy needs, says Steve Taub of Cambridge Energy Research Associates (CERA), in Cambridge, Mass. Denmark, Germany and Spain are market leaders in wind-power manufacturing and use, Taub says. Major companies include Germanys Enercon, Spains Gamesa and the United States General Electric, which is fast becoming a dominant player in the wind energy manufacturing market, Taub says. The markets leading company, Denmarks Vestas-NEG Micon, builds the 750-kilowatt wind turbines chosen by some of the school districts in Iowa.
The not-in-my-backyard principle often makes situating a wind farm difficult, leading to controversy from Wisconsin to Massachusetts, Parsons says. Opponents to a proposed wind farm in Nantucket Sound that could provide several hundred megawatts of electricity, for example, have raised issues about boat safety and fisheries impacts, among other concerns. Some worry about effects on tourism in Marthas Vineyard, where homeowners have protested the aesthetic impact of more than a hundred 128-meter-tall wind towers over 8 kilometers offshore.
The Nantucket project also may threaten shorebirds nearby, particularly terns, says Michael Burger of Audubon New York, in Ithaca. A wind turbine is estimated to kill two birds a year on average, he says, which highlights another issue that has long concerned environmental groups that might normally support such green-power sources. And while more birds die from colliding into glass windows, according to a review of the literature, the effect is cumulative. The more wind turbines we build, the more birds will be killed, Burger says.
One site where bird mortality levels have been particularly high is Californias Altamont Pass, carpeted in older wind turbines that seem to have proven attractive perches to raptors, including golden eagles, and tend to be placed in their flight paths. But new models have reduced the hazard, Burger says, even though future impacts of larger, taller wind turbines remain uncertain, particularly on birds that migrate at night.
A few birds have been killed by the Eldora-New Providence school districts turbine, says Grove, the former superintendent. He also cites other more noticeable downsides, including the noise of the moving blades (which make a sound like woomph, woomph, woomph, he says, audible from school ball fields), the rare possibility of ice forming on the blades during storms and falling, and the flickering effect that comes when sunlight shines through the blades.
Still, these issues are manageable in comparison to the benefits, Grove says. The districts wind generator has been active more than 90 percent of the year for the several years it has been running (94 percent and 96 percent in 2003 and 2004 respectively). At that rate, the turbine almost pays for the loans that purchased it, in electricity savings and excess energy (because it is net-metered, Alliant Energy pays the district for the excess), valued at close to $90,000 a year. Once the turbine pays for itself, the money will go to the district. And in the meantime, the wind project has been an excellent science project for Eldora-New Providence high school science classes.
Nevertheless, says Taub of CERA, in most places, wind power is still a pretty small fraction of energy produced, and even at current growth rates, its going to stay a pretty small fraction in most places. The United States, which uses more than one-quarter of the worlds power produced, has a 750,000-megawatt demand; U.S. wind power production currently totals about 6,750 megawatts. But, Taub adds, even though it costs nothing, the wind doesnt always blow, even in Iowa.
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