28-08-2014, 12:46 PM
underwater and windmill seminar report
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INTRODUCTION
I just did a Search here for "underwater" and "windmill" and it came up blank, so if this idea really has been posted here using some other verbiage,
Anyway, this Idea should be somewhat obvious in hindsight. We build ordinary windmills to extract useful power from wind energy. We put turbines in rivers (usually accompanied by dams) to extract useful power from downhill water flow. The second is more "energy intensive" than the first, which is why we all know that dams are great sources of electrical power, while electric-generator windmills spent decades in the economic doldrums (return on investment --ROI-- is relatively tiny, and only recently proved viable on a large scale).
Anyway, putting the equivalent of a windmill in a steady ocean current, say the Gulf Stream, should have an automatically-viable ROI that is intermediate between windmills and ordinary hydropower. This is because water is something like a thousand times denser than air, so a volume of flowing water contains a thousand times the energy of an equal volume of equally-flowing air.
Do note that the ocean has different currents at different depths. I once read somewhere that near the seafloor underneath the Gulf Stream is another current going the opposite direction. If true, then we can build towers on the seafloor, just like ordinary windmills, to extract power. Being so deep will protect them from ships, and most sea life is found at other depths, so they won't be bothered. Also, another thing that protects sea life is the fact that underwater windmills will have a SLOW rotation rate, due to that same greater density of water over air. This means we can also put windmills in the rich-life upper ocean currents; animals will have time to dodge the blades. (Some life forms, like barnacles, need to be discouraged; probably everything needs to be coated with Teflon or something even more slippery.)
Consider buoyant windmill modules can be anchored by cables to the bottom. They float up to perhaps fifty meters beneath the surface, in the midst of the ocean current. There they stay and generate power (which flows down those same anchor cables, and then toward shore).
Finally, it may be necessary to build all underwater windmill modules in counter rotating pairs. Again, this is because the water is denser than air; and for every unit of force that tries to rotate the blade, there will be reactive force against the generator assembly, Counter rotating blades will let such forces be canceled.
Tidal currents are being recognized as a resource to be exploited for the sustainable generation of electrical power. The high load factors resulting from the fluid proper- ties and the predictable resource characteristics make marine currents particularly attractive for power generation. These two factors makes electricity generation from marine currents much more appealing when compared to other renewables. Marine current turbine (MCT) installations could also provide base grid power especially if two separate arrays had offset peak flow periods. This characteristic dispels the myth that renewable energy generation is unsuitable on a large scale.
HISTORY
Two British consultants have developed an underwater pump that can irrigate riverside fields without using fuel or causing pollution. The prize-winning turbine is easy to construct and can work continuously
Originally designed to harness the energy of the Nile to irrigate the desert areas of Sudan, the pump has a three-blade rotor that utilizes the energy of moving water, just as a windmill uses wind. The underwater pump can be operated by a single person with little training
Researchers launched the first offshore tidal energy turbine on Monday. The rotor on the English coast uses the power of the tides to generate electricity. Just the beginning: The first "farm" of tidal turbines could spring up off the English coast within years.
Imagine taking a windmill, turning it on its side and sinking it in the ocean. That, in effect, is what engineers have done in the Bristol Channel in England. The aim is to harness the energy the tide produces day in, day out. On Monday, the world's first prototype tidal energy turbine was launched.
The "Sea flow" installation was built into the seabed about one and a half kilometers (one mile) off the Devon coast. Above the surface, only a white and red-striped tower is visible. Beneath, 20 meters down, the single 11-meter long rotor turns up to 17 and a half times a minute at a maximum speed of 12 meters per second, drawing energy from the water's current.
The €6 million ($7 million) project's supporters -- which include the British and German governments and the European Union -- hope that tidal turbines may one day be a further source of energy. Unlike sun and wind energy, tidal energy is reliable, since it's not affected by the weather.
"As long as the earth turns and the moon circles it, this energy is a sure thing," Jochen Bard from ISET, a German solar energy institute involved in the project, told the dpa news agency.
Renewable Energy
We can divide renewable energy sources into two main categories: traditional renewable energy sources like biomass and large hydropower installations, and the "new renewable energy sources" like solar energy, wind energy, geothermal energy, etc. Renewable energy sources provide 18% of overall world energy (2006), but most of this energy is energy from traditional use of biomass for cooking and heating - 13 of 18%. In large hydropower installations is another three percent. So, when we exclude conventional biomass and large hydropower installations it is easy to calculate that so called "new renewable energy sources" produce only 2.4% of overall world energy. 1.3% are water heating solutions, 0.8% are different power generation methods, and 0.3% are biofuels. In the future this portion should be significantly increased because the availability of non-renewable sources is decreasing with time, and their damaging influence has significantly increased in the last couple of decades. Sun delivers 15 thousand times more energy to Earth than humanity really needs in this stage, but despite this some people on Earth are still freezing. This fact shows us that we should exploit renewable sources much more and that we do not have to worry about the energy after fossil fuels cease to exist. Development of renewable energy sources (especially from wind, water, sun and biomass) is important because a couple of reasons:
• Renewable energy sources have major role in decreasing of emissions of the carbon dioxide (CO2) into atmosphere.
• Increased proportion of renewable energy sources enhances energetic viability of the energy system. It also helps to enhance energy delivery security by decreasing dependency on importing energetic raw materials and electrical energy.
• It is expected that renewable energy sources will become economically competitive to conventional energy sources in middle till longer period
SOLAR ENERGY
Solar energy is the energy derived from the sun through the form of solar radiation. Solar powered electrical generation relies on photovoltaic and heat engines. A partial list of other solar applications includes space heating and cooling through solar architecture, day lighting, solar hot water, solar cooking, and high temperature process heat for industrial purposes.
Solar technologies are broadly characterized as either passive solar or active solar depending on the way they capture, convert and distribute solar energy. Active solar techniques include the use of photovoltaic panels and solar thermal collectors to harness the energy. Passive solar techniques include orienting a building to the Sun, selecting materials with favorable thermal mass or light dispersing properties, and designing spaces that naturally circulate air.
BIO MASS
Biomass (plant material) is a renewable energy source because the energy it contains comes from the sun. Through the process of photosynthesis, plants capture the sun's energy. When the plants are burnt, they release the sun's energy they contain. In this way, biomass functions as a sort of natural battery for storing solar energy. As long as biomass is produced sustainably, with only as much used as is grown, the battery will last indefinitely.
In general there are two main approaches to using plants for energy production: growing plants specifically for energy use (known as first and third-generation biomass), and using the residues (known as second-generation biomass) from plants that are used for other things. See bio based economy. The best approaches vary from region to region according to climate, soils and geography.
TIDAL ENERGY
Tidal power is a consequence of Sun's and Moon's gravity forces. For now, there is no major commercial exploitation of this energy, despite of its big potential. This energy can be gained in places where sea changes are extremely emphasized (for instance some places have difference between high tide and low tide bigger then 10 meters). The principle is quite simple and very similar to the one of the water power plant. On the entrance to some gulf, escarpment is built and when the level of the water rises, water leaks across the turbine in to a gulf. When gulf is filled with the water escarpment is sealed and after the level of the water falls the same principle is being used to direct water out of the gulf. In more simple case water leaks through turbines in only one direction, and in this case turbines are less complicated (unilateral, not bilateral). The biggest problems of this use of energy are vicissitude of tidal power (wait the sufficient level of the water to rise enough, or to fall enough) and small number of places suitable for using this energy source. The most famous power plant is the one on the river Rance delta in France (picture) built in 1960 and still functional. Russia has build small power plant near city of Murmansk, Canada in gulf Fundy, China small number of them, but neither of this countries has made any significant progress. Alternative method of use relates to the location of power plants in sea ravines where due to a canalizing tidal wave, its energy increases, and underwater turbines similar as the ones of the wind power plants would be used as the generator machinery. Energy of the sea currents is also planned to be used in the same way, but this technology is still in very early phase
UNDERWATER WINDMILL
DEFINITION
Tidal stream turbines are often described as underwater windmills. They are driven by the kinetic energy of moving water in a similar way that wind turbines use moving air. The generator is placed into a marine current that typically results when water being moved by tidal forces comes up against, or moves around, an obstacle or through a constriction such as a passage between two masses of land. There are sufficient numbers of such fast-flowing underwater currents around the world to make this form of marine renewable energy worth pursuing. In figure 1, the areas between the coasts of Ireland and Scotland that are colored magenta would merit the application of tidal current capturing systems. Harnessing the marine currents could also help fulfill the Climate Change Committee’s recent request in 2010 that calls for an almost complete.
decarburization of the UK’s electricity supply by 2030. In their report, Future Marine Energy, published in 2006, the Carbon Trust estimated that tidal stream energy could meet 5% of the UK’s electrical energy needs, reducing the country’s dependence upon carbon intensive imported fossil fuels. Other studies have predicted that tidal generators could produce up to 10% of the UK’s electrical energy needs. A point not lost on the UK government and the devolved administrations who see the industrial growth opportunities that tidal and wave energy could offer. Tidal flows have the advantage of being as predictable as the tides that cause them; both in terms of timing and in judging their maximum velocity. This long-term predictability helps greatly in electricity generation, enabling more efficient grid management and thus reducing the total amount of power that needs to be generated.
Energy derived from the moon now trickles into an Artic tip of Norway via a novel underwater windmill like device powered by the rhythmic slosh of the tides. The tidal turbine is bolted to the floor of the Kvalsund channel and is connected to the nearby town of Hammerfest’s power grid on September 20th. This is the first time in the world that electricity directly from a tidal current has been feed into a power grid. The gravitational tug of the moon produces a swift tidal current there that cause though the channel at about 8 feet (2.5 meters) per second and spins the 33-foot (10 meters) long blades of the turbine. The blades automatically turn and rotate at a pace of seven revolutions per minute, which is sufficient to produce 700,000 kilowatt hours of non-polluting energy per year- enough to power about 35 Norwegian homes (70 U.S homes).
PRINCIPLES
Underwater turbines operate on the same principles that wind turbines use; a flow of fluid moves a set of blades creating mechanical energy which is then converted to electrical energy. They are equally troublesome for environmentalists, as wind turbines interrupt bird flights just as water turbines can disturb underwater life. One advantage water turbines enjoy over other sources of renewable energy is a predictable tide table.
MCT's ocean energy device works on the same principles as a windmill, where large underwater rotors, shaped like propellers, are driven by the huge mass of flowing water to be found at certain places in the sea. The technology consists of rotors mounted on steel piles (tubular steel columns) set into a socket drilled in the seabed. The rotors are driven by the flow of water in much the same way that windmill rotors are driven by the wind, the main difference being that water is more than 800 times as dense as air, so quite slow velocities in water will generate significant amounts of power. The energy generated, being derived from tides has the added significant advantage of being predictable
Power Generation by Underwater Windmill And Cost
Energy derived from the moon now trickles into an Artic tip of Norway via a novel underwater windmill like device powered by the rhythmic slosh of the tides. The tidal turbine is bolted to the floor of the Kvalsund channel and is connected to the nearby town of Hammerfest’s power grid on September 20th. This is the first time in the world that electricity directly from a tidal current has been feed into a power grid. The gravitational tug of the moon produces a swift tidal current there that cause though the channel at about 8 feet (2.5 meters) per second and spins the 33-foot (10 meters) long blades of the turbine. The blades automatically turn and rotate at a pace of seven revolutions per minute, which is sufficient to produce 700,000 kilowatt hours of non-polluting energy per year- enough to power about 35 Norwegian homes (70 U.S homes
NEXT GENERATION UNDERWATER WINDMILL
Harnessing the vast energy of the UK's coastal tides could become much simpler and cheaper with a new design for the next generation of underwater turbines. The device, unveiled by a team of engineers from Oxford University, re-thinks the way power is generated underwater and the inventors believe it will be more robust, more efficient and cheaper to build and maintain than anything in operation today.
There is an immense potential resource of clean energy from the tidal flows around the UK: conservative estimates suggest there is at least five gigawatts of power, but there could be as much as 15GW, equivalent to 15 million average family homes. Tidal generators can harvest the energy of these moving streams, with the added advantage that the resource is, unlike wind, predictable.
There are only a few underwater turbines in operation today and they all operate like underwater windmills, with their blades turning at right angles to the flow of the water. In contrast, the Oxford team's device is built around a cylindrical rotor, which rolls around its long axis as the tide ebbs and flows. As a result, it can use more of the incoming water than a standard underwater windmill.
At full size, a Transverse Horizontal Axis Water Turbine (Thawt) rotor would be 10m in diameter and 60m long. Connecting two of these together with a generator in the middle could produce around 12MW of power, enough for 12,000 average family homes.
"To do that, you only need three foundations and one generator," said Martin Oldfield, senior research fellow of engineering science at Oxford University. "To do that with a [windmill] would require five foundations and 10 generators
FUTURE DEVELOPMEN
MCT is now concerned not only with ensuring that its SeaGen type device is installed in other locations, but also with the conception of new forms of this technology that are both more powerful (to gain further economies of scale) and viable in shallower and in deeper water than the 20 m to 40 m range that suits the current design. In shallower water the existing twin rotor system would provide too small a swept rotor area to be cost-effective, while deeper water brings concers about taller tower structure cost and strength.
A potential solution under consideration and already patented is a buoyant support tethered to the seabed by rigid but hinged struts. This system, which is based on the same rotors, control systems and power-trains as the existing SeaGen, has been labeled SeaGen “U” and is already under development. A 2 MW at 2.4 m/s version with three rotors is planned for installation in the Minas Straits of the Bay of Fundy in Nova Scotia, Canada by 2012-3. Systems rated at over 5 MW with up to six rotors are expected to follow. The wind industry has improved the cost-effectiveness and efficiency of windturbines by gradually enlarging them – a few years ago 1 MW was the norm but today up to 5 MW systems are preferred. There is a similar pressure to develop larger in order to improve their cost-effectiveness and generate electricity more cheaply.
Peter Fraenkel thinks that as with all new technologies, tidal turbines will be initially too expensive to be immediately competitive. They will need to benefit from economies of scale and learning curve effects to get their costs down. As a result he believes this new renewable energy technology market needs government subsidies such as ROCs (Renewable Obligation Certificates) to help finance early stage small projects, and to see the technology through the stage between R&D and full commercial competitiveness. Fraenkel is confident that tidal turbine technology will become competitive reasonably quickly but the first projects will need support to leverage the necessary investment
EFFECT ON ENVIRONMENT
"I think we have invented one of the least offensive energy methods," MCT technical director Peter Fraenkel told Deutsche Welle. He explained that the effect on marine life would be minimal. "Any kind of higher marine mammals is as likely to run into it as a human begin is to walk into a brick wall." Not only do marine creatures mainly move faster than the rotor, water spirals through it in such a way that even jellyfish would be likely to go right through without being harmed.
Greenpeace climate and energy campaigner Robin Oakley told Deutsche Welle he didn't expect negative impacts from Seaflow either. When it comes to environmental impact, "there's a very big positive that has to be taken into account," Oakley said. "You have to weigh the effects carefully, he said. "That can't be allowed to slow down the development of green energy."
It is the first of a kind SeaGen serves as a testbed for tidal power generation. To date, it has not yet had a full year of operation unconstrained by other research considerations. From installation until November 2009 the system could only be operated when two marine mammal observers were on board, and able to look out for seals that might be in danger from the rotors (which rotate at about 14 rpm). Further seal monitoring restraints continued to reduce operation to daylight hours until March 2010, so energy yield was significantly reduced. There is great concern to avoid sanctioning anything that could cause negative environmental impact at the Strangford site. After two years of independent environmental monitoring no sign of a detrimental effect has so far been detected. At the time of writing, seal movements near the turbine still have to be monitored in real time using sonar by an operator onshore who can shut the turbines down within five seconds if they feel a seal might be in danger. It is expected that this requirement may soon also be relaxed as there are no signs yet of seals having so far been harmed. The environmental monitoring programme which will run for five years in total will cost some £2 million by the time it concludes. It has been very useful in terms of environmental data acquisition and giving new insights on the behaviour of seals and other marine wild-life endemic to this environmentally significant location.
CONCLUSION
Ocean energy can play a significant role in our nation’s renewable energy portfolio. With the right support, the ocean energy industry can be competitive internationally. With the right encouragement, ocean renewable energy technologies can help us reduce our reliance on foreign oil – fossil fuels, in general – and provide clean energy alternatives to conventional power generating systems. And with the right public awareness, our coastline communities can use ocean renewables as a springboard for coastal planning that reflects the principles of marine biodiversity.
In conclusion, we believe that the intense and predictable marine current resource offers the possibility of clean energy at a cost that will ultimately be competitive not only with the other renewables, but in the long run we believe we can compete head on with most forms of fossil fuelled power generation at present-day costs. We think that, given appropriate government support to help the technology through its early and immature stages, it can play a significant role in producing clean energy.
Tidal energy has potential to become a viable option for large scale, base load generation in Scotland. Tidal Streams are the most attractive method, having reduced environmental and ecological impacts and being cheaper and quicker installed.
Development of a robust offshore renewables industry can:
• Reduce reliance on foreign oil.
• Rely upon ocean terrain for power generation as opposed to onshore land resources.
• Revitalize shipyards, coastal industrial parks and shuttered naval bases.
• Create jobs in coastal communities.