Hydrokinetics literally refers to the process of generating electricity by harnessing the motion of water. It’s nothing new; hydroelectric power plants use this very principle. However, it seems that we’ve picked most of the low-lying hydroelectric fruit, and now the focus shifts to capturing the power in oceans and rivers.
A whole slew of ocean/wave power technologies is being developed, and although they haven’t come to reality just yet, there is a lot of potential – mostly because the ocean is huge, and as long as a technology can be brought to scale, the general consensus is that there is plenty of energy to tap.
River hydrokinetics, on the other hand, seem to have hit some snags. The principle is essentially the same – build some kind of turbine that is pushed by the current of the river. The difference is that they usually produce less power. More importantly, building them is a regulatory nightmare, since companies trying to put them underwater are legally treated as if they were building a hydroelectric dam (which, as you can imagine, is not simple).
Take Hydro Green, a company that just installed the nation’s first hydrokinetic turbine in Minnesota, under the Mississippi River. It works, and it’s green… but it only generates 35 kilowatts. Maybe this was just a prototype; maybe newer models will generate more electricity. But if you are going to have to build more than 40 of these things just to get the same amount of energy coming out of, say, one of GE’s 1.5 MW wind turbines – you have to wonder about the pros and cons.
Verdant Power is another example – they’ve been working on putting turbines like this in the East River of New York City for years. According to a researcher at the Electric Power Research Institute, they have spent more money on permits than they spent on actually building their turbines!
I’m not saying that putting turbines in rivers doesn’t make sense BECAUSE there is red tape. But every idea needs to pass a cost-benefit analysis, and given the various costs of building turbines in slow moving rivers, I wonder whether the ultimate benefits would really outweigh the costs. There may be more to gain from the ocean.
Water, water, everywhere, but hardly a drop moving fast enough to produce electricity?
Existing technologies that harness energy from water can only operate if the current is moving at five or six knots, but most of the world's currents are slower than three knots. Good news! A new cylinder device is able to produce power from a current flowing at less than one knot.
University of Michigan scientists were inspired by the way fish swim to create the cylinder system called Vivace. Water flows around the cylinders creating vortices, which push and pull the cylinders up and down. This energy is then converted into electricity.
The scientists believe that groups of cylinders could be placed in river or sea beds or suspended in the ocean. A field of cylinders covering an area 1km by 1.5km with a current of three knots could power 100,000 homes. Scientists say the technology requires 50 percent less ocean acreage than wave power.
The researchers also say that because the parts move slowly, they are less likely to harm aquatic life than dams or turbines, and their position underwater will keep them from interfering with shipping or being an eyesore.
A prototype is currently being tested in the Detroit River, which has a current of less than two knots. If this technology is successful, it could open up most of the world's water to power generation, which could result in huge gains towards powering the world on renewable energy.
via Daily Telegraph
One of the first rules of the game when it comes to energy is that every time you transfer energy from one form into another, a little bit spills out on the way. It is for this reason that I am generally skeptical when I read about a solar-to-electric-to-biofuel-to-battery-to-whatever technology. That being the case, let’s examine the Searaser:
Designed by British inventor (is that a real profession in Britain? I’ve always wanted to be an inventor...) Alvin Smith, the Searaser is a buoy connected to a piston. The buoy is fixed into place; as a result, it bobs up and down with the waves. As it does, it turns the piston and pumps sea water through an undersea hose. The hose carries the water to a high place (either on land or at sea), where it can fall back down to earth, spinning a turbine in the process.
On the one hand, the device itself seems simple enough and is reportedly on the cheap side. It would not use up any fresh water resources, since all the water travelling through the system would come from the ocean. But if the wave can turn the pistons, why not simply turn a generator underwater? Why go through the trouble of building long hoses and constructing artificial waterfalls?
It is possible that keeping the underwater parts simpler makes for a more robust system; if all the important parts are underwater then when they sink, you are sunk as well. This way, even if one of the buoys breaks down, the important part is still on land. And maybe hoses are cheaper than underwater electric transmission wires. I hope my instincts are wrong; Smith calculates that a sizable fleet of his inventions could power millions of homes.
Ocean Power Technologies and the Navy have joined together to create a small wave farm off the coast of Oahu, Hawaii. The company has installed one of its PowerBuoy units one mile off the Kaneohe Bay Marine Corp Base, with plans to install others in the near future to generate 1MW.
The PowerBuoy will be connected to the Oahu grid and Kaneohe Bay will serve as a test site for the Navy, which is hoping to install these units at bases around the world. This project is part of the Navy's larger goal of reducing their dependence on fuel shipments for power.
Ocean Power Technologies has previously installed PowerBuoy units off the coast of Atlantic City, NJ and Santoña, Spain. The units are only 12 feet in diameter and 55 feet long and can be arranged in arrays that generate hundreds of megawatts. The onboard sensors automatically change settings in response to sea conditions. If the buoy encounter very large waves, it automatically powers down until conditions have settled.
The military is often one of the first users of cutting edge technology, so I'm glad to see that they are also eager to utilize something as promising as wave power.
via Ocean Power Technologies