Flowing water carries more than 800 times as much energy as a
comparable volume of air, which makes water power an appealing method
for producing electricity. Even before the advent of electricity, water
mills were some of the earliest systems that went beyond human- or
animal-power to do work. In the electrical age, hydropower has typically
been associated with big dams and correspondingly large
infrastructures. Capturing the power of enormous volumes of water behind
a dam allows hydropower stations to produce billions of killowatt-hours
of electricity annually, comparable to other base load power plants.
But like other base load plants, there is also a strong downside to big
dams that makes them less than environmentally preferable. However, new
hydrodynamic systems are coming along that draw power from moving water
and are able to produce energy with far less environmental impact.
While pent up artificial lakes are easy to turn into massive power
plants, the environmental devastation that comes from the flooding of
millions of acres of land, and the disruption of the ecosystem of the
river make large-scale hydropower a second-class form of green power, at
best. From a carbon perspective, hydropower is certainly preferable to
burning fossil fuels. But the associated damages caused by building
large-scale hydropower plants — including turning flowing water into
lakes and blocking the migration of fish — is such that new dams for
generating electrical power are mostly off the table.There are
alternatives to creating an enormous lake in order to constantly feed
the turbines.
Small-scale turbines that can sit in flowing bodies of water and generate electricity could now be poised to bring
a new face to hydropower. These turbines are greener since they don’t
require the blockage of waterways and the destruction and flooding of
land in order to be able to produce power. Hydrodynamic power works with
the energy in moving water, rather than closing off waterways to build
up huge reserves of potential energy stored in the water held behind
giant dams. Developmental systems from several companies are now
exploring the production of more modest amounts of power, but with far
lower cost and with much less environmental destruction than that from
the creation of dammed hydropower. Companies such as Hydrovolts Inc.,
Free Flow Power and Verdant Power have different systems to make use of
this power, which they are testing in different parts of the country.
There are also researchers who are working on other systems that can
potentially take advantage of more energy available in slower moving
water.
The federal government in the United States has identified this as an
as-yet untapped source of power. The existing water infrastructure of
the American West offers a great deal of hydropower potential, with the
greatest amount found in the states of Colorado, Oregon and Wyoming. A
study by the U.S. Department of the Interior’s Bureau of Reclamation
found that 1.5 million megawatt-hours of renewable energy could be generated
through hydropower without needing to construct new — and
environmentally questionable — large-scale dams. Instead, existing
waterways and reservoirs can be used to provide electricity in addition
to serving water needs of the region. (For comparison, the Hoover Dam
power station produces about 4 million megawatt-hours
of electricity annually. Think of this as another one-third of a Hoover
Dam spread out through the existing water infrastructure.)
Aqueducts and canals represent an available source of power for
additional electrical generation. Particularly in the western U.S.,
where water management is carried out through an extensive
infrastructure of constructed canals and waterways, it may be possible
to provide power for tens of thousands of additional homes. Existing
dams that were built for water management rather than for power
generation may be able to be tapped for power production as well,
through the installation of smaller scale equipment that can efficiently
and cost-effectively produce power from dams that may have previously
been thought too small to be useful for power generation.
To make use of this hydrodynamic power, small, in-line turbines can be installed that generate electricity from the flow of water
through aqueducts and canals. The turbine sits directly in the
waterway, without a dam, which means that the negative impacts to the
environment, as well as the infrastructure costs to install this
equipment, are greatly reduced.
Because these waterways already constrict the flow of water moving through them, a greater proportion of the energy from the water
flow can be captured with this equipment. In a canal, where most of the
water flow must go through the turbine, the efficiency can be as high
as 60 percent. Depending on the size of the waterway and the flow rate
of the water moving through it, turbines can provide electrical output
ranging from 1.5 kW to 30 kW. Because many of these waterways have
continuous flows of water moving through them, they are well suited to
provide additional, continuous power generation for the grid.
The Bureau of Reclamation has over 47,000 miles of canals, laterals,
drains, pipelines and tunnels. To find places with hydropower potential,
the government study identified those locations where there was at
least a 5-foot drop and where the waterway was in operation for at least
four months out of the year and where the power generation potential
was at least 50 kW (based upon flow rate of canal and the drop height).
One manufacturer producing turbines for in-line uses is Hydrovolts, Inc. These are reasonably small pieces of equipment. Turbines for canals and waterways are about the size of a car or small truck. Waterfall turbines can be even smaller, and will still produce a significant amount of power. They are also fairly inexpensive,
with the cost of the smallest portable model starting at just $2,000.
The canal-sized turbines cost from $20,000 to $40,000. While wholesale
electrical rates are not great, since their output will be fairly
consistent, these turbines can potentially repay their investment cost
in just a few years. Initial tests of the Hydrovolts turbine were
carried out in the Roza Canal in Washington State earlier this year.
(Quick back-of-the-napkin math: A turbine
costing $40,000 and generating an average of 25kW over a year of
operation will produce almost 220 MWh of power and earn over $10,000 at a
wholesale electrical rate of $0.05/kWh. That could mean that the
equipment could be paid off in four years.)
Hydrovolts turbine in the Roza Canal in Washington State:
Hydrovolts turbines also can be outfitted with different kinds of
blades, depending on the flow rate of the water. This makes the system
more versatile, and the same equipment can be used in different
locations, with just a change of blades in order to produce the optimal
yield from a given location.
While many of these channels being discussed for use are artificial
waterways used for irrigation, the same technology can be used in open
water rivers and streams with a sufficient flow rate. In those cases,
having the waterway open to fish migration and movement is another
benefit from this technology.
While the Hydrovolts turbines are being developed for very small
waterways, the opposite end of the hydrokinetic power scale is also
being explored with a project set in the world’s largest river. Free
Flow Power is a company that is developing river flow turbines to be
placed along a length of the lower part of the Mississippi River.
The Free Flow Power turbine is a 3-meter diameter multi-bladed
propeller inside a housing that makes it look very much like a large jet
engine. The turbine has a 40 kW rating. The first array of these
turbines will be installed at a total of 25 locations
along the Mississippi River and will provide a total generating
capacity of 3,303 MW. Given the size of the river and the volume of
water that flows through it, there is a great potential for much more
energy production if this technology turns out to be effective and
cost-competitive.
Unlike wind farms, these turbines are out of sight below the surface
of the water. Despite their size, since these turbines will be installed
below the water’s surface, they will present very little obstacle to
navigation, so that the Mississippi will also continue to serve as an
efficient highway for barge traffic moving goods up and down the river.
This project may be just the beginning for harnessing the vast power of
so much water moving through the middle of the country.
Verdant Power has another project that builds on some of the work done for the RITE project. The Cornwall Ontario River Energy Project
(CORE) is installing turbines in the St. Lawrence River near Cornwall,
Ontario to study how the turbines work in a river flow situation.
The turbines Verdant is developing are three-bladed, without an
enclosure, and look quite similar to the now familiar three-bladed wind
turbines, except for their comparatively much smaller size. The Verdant
turbines are larger than those being developed by Free Flow Power; for
the CORE project they are using turbines with a blade diameter of 5
meters and with a generating capacity of 60-80 kilowatts. These
turbines, too, would sit out of the way of surface vessels on the bottom
of the waterway. An animation from Verdant shows what a large-scale farm of these turbines might look like.
Along with these developmental systems, researchers are working on
other low-velocity technologies for hydrokinetic power generation. One
system, being explored by researchers at the University of Michigan
is called VIVACE, which stands for Vortex Induced Vibrations for
Aquatic Clean Energy. VIVACE is especially interesting because it
promises to work with slow moving river flows as slow as 2 knots. Most
river currents in the United States are slower than 3 knots.
The VIVACE system works with horizontal cylinders placed across the flow of the water to create a vortex as the water flows past the cylinder.
“Vortex Induced Vibration (VIV) is an extensively studied phenomenon
where vortices are formed and shed on the downstream side of bluff
bodies (rounded objects) in a fluid current. The vortex shedding
alternates from one side of a body to the other, thereby creating a
pressure imbalance resulting in an oscillatory lift.” This motion of the
cylinder can, in turn, be used to move a magnetic field in order to
produce electricity.
The turning blades of hydrokinetic turbines are a potential concern,
just as wind turbines are with birds. Part of the reporting being done
with these early projects is to study potential problems with this kind
of equipment. Although its development is lagging behind some of the
other systems, VIVACE may turn out to be a preferable technology because
it has less impact on marine wildlife. The cylinders used in this
system are very slow moving (only about 1 cycle per second), and the
risk of harm to any fish is therefore extremely low.
Hydrokinetic projects are appealing because the power generation is
more constant than some other sustainable systems. Waterway flows can be
more regular and dependable than intermittent sources like wind.
Hydrokinetic power is presently an underutilized resource, but as these
companies develop their technology, it is likely to become another part
of the energy mix.
By Philip Proefrock@REVMODO.com
Hydropower Continues Steady Growth
World hydroelectric power generation has risen steadily by an average
3 percent annually over the past four decades. In 2011, at 3,500
billion kilowatt-hours, hydroelectricity accounted for roughly 16
percent of global electricity generation, almost all produced by the
world’s 45,000-plus large dams. Today hydropower is generated in over
160 countries.
Four
countries dominate the hydropower landscape: China, Brazil, Canada, and
the United States. Together they produce more than half of the world’s
hydroelectricity.
Much
of the world’s recent growth came from China, where hydropower
generation more than tripled from 220 billion kilowatt-hours in 2000 to
720 billion in 2010. In 2011, despite a drop in generation due to
drought, hydropower accounted for 15 percent of China’s total
electricity generation.
Brazil,
the second-largest producer of hydropower worldwide, gets 86 percent of
its electricity from water resources. It is home to an estimated 450
dams, including the Itaipu Dam, which generates more electricity than
any other hydropower facility in the world—-over 92 billion
kilowatt-hours per year.
Approximately 62 percent of Canada’s
electricity is generated from its 475 hydroelectric plants. The
country’s enormous hydropower capacity allows for electricity export;
Canada sells some 50 billion kilowatt-hours to the United States every
year—-enough to power more than 4 million American homes.
Because
most large dams in the United States were built before 1980, the
country’s hydropower capacity has remained relatively stable in recent
decades. The country’s highest capacity dam—-the Grand Coulee Dam on the
Columbia River in Washington State—-was completed in 1942. Today, more
than 7 percent of all U.S. electricity is supplied by hydropower.
Similarly, hydropower in the European Union is relatively mature, with
capacity increasing by less than one percent annually over the last 30
years. In 2011, hydropower supplied 9.5 percent of E.U. electricity
generation.
Among
the world’s largest producers, Norway gets the greatest share of its
electricity from hydropower: a full 95 percent. Other countries that get
the bulk of their electricity from river power include Paraguay (100
percent), Ethiopia (88 percent), and Venezuela (68 percent). A number of
African and small Asian countries also generate virtually all of their
electricity with hydropower, including Bhutan, the Democratic Republic
of the Congo, Lesotho, Mozambique, Nepal, and Zambia.
While
conventional hydropower will continue to grow as dams are completed in
China, Brazil and a scattering of other countries, including Ethiopia,
Malaysia, and Turkey, there exists enormous potential for
non-conventional hydroelectricity generation from tidal and wave
projects, as well as from small in-stream projects that will not require
new dams.
Thus far, few of these hydrokinetic projects have been
realized. France’s La Rance Tidal Barrage, with a 240-megawatt maximum
capacity, was the first large tidal power plant. It began generating
power in 1966, and is still operating today. In South Korea, a
254-megawatt project was completed in August 2011. Now the world’s
largest tidal operation, it has the capacity to provide electricity for
half a million people on the country’s west coast. New Zealand also
recently approved a coastal hydropower project.
Wave power is also
drawing the attention of both engineers and investors. Firms in France,
Scotland, and Sweden, among other countries, are working to capture
this emerging market. Estimates from the World Energy Council indicate
that worldwide, wave energy has the potential to grow to a massive
10,000 gigawatts, more than double the world’s electricity-generating
capacity from all sources today.
For additional data on the world’s energy resources, visit Earth Policy Institute’s Data Center and see the Supporting Data from World on the Edge by Lester R. Brown at www.earth-policy.org.
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