Decades of research leaves few contenders
Researchers have been studying wave power
and slowly learning which
concepts work best. There
are now more than
held worldwide related to wave power, although there are very few commercial
wave power generating stations which actually put electricity on the grid.
Todays technology, while quite
is primarily based on one of three designs, each of which have been around
for some time:
Water Column (OWC) - An OWC is a large structure which is
conventionally built on the shoreline. The early designs were monolithic, but
the latest plans call for pre-fabricated units, made of easily-replaceable
sections. The OWC traps the incoming wave, and forces it into a narrow chamber
(pipe). The resulting air pressure above the water in the pipe drives a
Wells Turbines are
designed to allow air to pass through in both directions, while spinning in the
same direction, thus harvesting power from both the incoming pressure, and the
outgoing suction created in the chamber by the wave. While OWC technology is
well tested and fairly reliable, it requires extensive modification of the
shoreline to install the structure, and it is not as efficient as other devices
which harvest wave power offshore - although
of the wave chamber have been encouraging.
The UK has spent the most time and money researching and developing
OWC wave power. Recently the leading producer of OWC devices there was
awarded £2.1m to test a new prototype, in fact. An interesting
hybrid OWC station which is deployed offshore is called the
which produces power for Japan.
Flapper - The "flapper" is one of two primary designs which
are deployed offshore using pontoons or buoys. Flapper devices go under
several different names, Salter Duck, Clam, and others. Typically, these devices
consist of a string of floating pontoons which are shaped a bit like a camshaft.
Each pontoon is essentially a cam, which flaps, or rotates partially, from the
wave passing over it. This flapping effect drives capillary pumps, sending
liquid through a common hose, and eventually to a turbine which converts the
liquid pressure to electricity. These wave-power devices are conventionally
deployed perpendicular to the incoming wave force. Because of that, flappers are
particularly susceptible to heavy seas and storms.
A newer, and very promising innovation on the arrayed pontoon configuration
looks something like a "snake" of pontoons which are deployed parallel to the
wave force. This device, called the
(after the sea-snake), achieves its pumping action via the "slithering" of the
pontoons as the wave passes beneath each section on it's way to the shore. The
Pelamis seems to hold promise, especially as a supplemental power source
for offshore consumers such as oil rigs, but it's potential is
limited by it's pumping capacity and the waves height.
buoy-Pump - the heaving buoy-pump design sets out large buoys offshore
which, through their heaving (bobbing) motion, drive an underwater
piston and pump assembly attached to the buoy via a long cable or rod. As
with the flapper devices, the resulting hydraulic fluid pressure is converted to
electricity. Typically, a large structure
to the ocean floor
(mpeg) houses the piston and pump assembly as well as the converter
There are many variants on the basic buoy-pump design - with differences in the
form and location of the piston, the type of pump, and the size and shape of the
buoy, just to name a few. According to Bellamy and others, the buoy-pump
design seems to hold the most promise for the future of wave power - but the
buoy-pump design is not without its own set problems. Like other offshore
devices, they're subject to bad weather, albeit not to the extent of the
flapper or snake design. They typically also require heavy underwater moorings -
and a lot of "deep water work" to install.
Heaving Buoys - a closer look
As mentioned at the beginning of this article, an American company now
has an implementation of the buoy-pump design that they claim can overcome some
of the difficulties. In fact, the company claims that their device can produce
power in the 3-4 cents/kwh range - that's the threshold price at where wave
power can compete with conventional power prices. Before we take a look at
this new contender, let's have a closer look at how the buoy-pump device
actually works, and find out something about the challenge to make it efficient.
Possibly the most difficult challenge for a buoy-pump wave-power station is
meeting the wave itself. Optimizing a buoy-pump device for various conditions is
a tricky business. A good buoy-pump must be able to accomodate varying wave
height and frequency to effectively and efficiently drive a pump. The buoy must
maximize lift, without exceeding the length of the piston shaft which is driving
the pump beneath. If the wave is too high, the piston must be protected from
excessive lift. Not to mention corrosion and rust.
The piston/pump assemblies are complex as well. They're typically built
with a heavy spring and/or counterweight to return the piston to the "down"
position after being lifted by the wave. The "downstroke" has to be timed as
closely as possible to follow the form of the "back" of the wave, in order to
minimize drag. Theoretically, the piston and its buoy should achieve a state of
resonance. In practice, this is accomplished through the use of various
valving and latching techniques which are also built into the
piston and pump, along with the spring and counterweight.
The buoy pump system is typically deployed about a kilometer offshore, but is
naturally dependent on observation and testing to determine the best location.
Depth is an important factor, as well as the undersea
geology. The most common designs have their pump, piston, and generator
workings located in a structure which is moored directly to the sea bottom, with
the buoy attached via cable or rod. Depth is therefore an important factor for
maintenance, as well as initial installation costs. Naturally, a deployment
location also must be closed off to shipping and recreational boating, although
the buoys are typically grouped within a specific (limited) area.
Building a better wave trap
So, that's all very nice, but what about the grand allusion at the beginning of
the article? Has someone really built a better wave-trap? I'm still leaning
towards a definite "maybe" on that question, but let's have a closer look.
Ocean Power Technologies
(OPT) was founded in 1994 by
an electrical engineer from Australia. Taylor and co-founder Joseph
Burns worked with US Navy during the late 80's, to develop piezoelectric streamers,
which collect energy passively from the wave's motion. During the early 90's,
they turned their focus to buoy-pump devices. But they weren't the only ones
who were looking hard at buoy-pumps at that time. In Norway, for example, at
Wave Power Research Division of the
Norwegian University of Science and Technology (NTNU), a good deal of
research was reaching the "note" stage. The scientists there
were considering things like
phase control and optimum oscillation, and discussing the necessity for
predicting oncoming wave amplitudes to help optimize
the piston stroke as early as 1993. The buoy-pump concept was definitely
catching on during the 90's, but the technology needed to catch up.
Since then, according to Taylor, he and his company have striven to design a
system which "could compete straight on economics against fossil fuel in an
international market." The buoy-pump device which they're now selling as part
of that system is called the Power Buoy. It's a "smart buoy", says
Taylor, which purports to avoid many of the previously mentioned obstacles
faced by buoy-pump systems, via a few key design innovations:
piston/pump workings are built into the buoy itself, which means better control
and optimization of their workings, and less deep-water work for deployment and
upkeep. Only the generator is deployed underwater with the Power Buoy system.
The generator is driven by hydraulic fluid pumped down from an array of Power
Buoys. It sends DC current to shore, where it's finally converted and put on
- Innovative moorings - the Power Buoy has optimized moorings so that,
when a storm surge rolls in, the buoy "lays down" near the bottom, avoiding the
heaviest seas. The Power Buoy is deployed almost completely underwater,
displaying only a small warning bell/light and air-hose above the surface. It
can adjust it's buoyancy automatically, to be able to "run deep" in heavy
- Computerized control - the buoyancy and piston workings are controlled by a
computerized controller which is built into each buoy. This allows for realtime
monitoring and adjustments of the system, as well as functionality to predict
the approaching "next" wave. This prediction of the oncoming wave helps the
Power Buoy to approach true resonance with each wave, and harvest maximum power.
- The Power Buoy also utilizes the piezoelectric streamers mentioned
previously to harvest additional power. While it's unclear how
much additional power these devices contribute, they do optimize the potential
of the base design.
Testing the Power Buoy
With the backing of the US Navy, OPT tested it's system on the shores of New
Jersey where the company is based. That test, which utilized a scaled-down
prototype version of their current device, seems to have been a success. The
device produced reliable power which powered an underwater Navy research sub.
More importantly perhaps, the original test of the Power Buoy proved that it
could withstand very heavy seas - in the fall of 1998 Hurricane Bonnie pounded
their demo unit pretty hard, and it stood up well. According to Taylor,
"The ocean's a tough environment, people who have tried to
use wave energy before have all failed. We hold the world record for a system
that works in the ocean."
With the success of the demo unit behind them, during the middle of 2001, OPT
announced that the Navy had decided to fund, to the tune of $4.5m, the testing
of the Power Buoy system in a large scale deployment
off of the coast of Hawaii. Ostensibly, this test was to produce 1 megawatt of
power, although that number has since been reduced. In Hawaii, like lots of
other places, there's a significant power crunch due to lack of new generating
plants, but there's also significant resistance to another conventional plant,
making the Power Buoy an attractive alternative.
As mentioned, the
Office of Naval Research
is funding the test, with the intent of eventually handing over the
production and maintenance of the station to the local power company. Updates
on this test, unfortunately, have not been forthcoming from OPT.
The announcements indicated that the first Power Buoy would be installed by
September of last year, however. And since then, military reporters have
talked up the experiment on their base websites, with the
coming in November of last year. The report seems to allude to positive early
results, even noting that the Power Buoy can produce 100kw of power - but when
I contacted OPT directly to ask about the results, I was sent a polite, but very
uninformative reply. I also contacted the local Hawaiian reporter who
covered the kickoff
in mid-2001, but she hadn't looked in on the progress of the test since her
report. I even dropped a line over to the Navy Research folks who were
responsible for the articles on the base websites, but when they couldn't "find
me in their reporter-database", they summarily ignored me. Ah well.
The Power Buoy is also being tested in Australia. The
in July 2001 states that the station built will generate 10 megawatts, although
that estimate has been sized down somewhat, possibly due to
delays approving deployment sites, but you'll soon
see there's a bigger reason than that. In any case, a
from June 2002 has a really nice
of the full-sized production model Power Buoy, ready to ship out to it's new
home on the Victoria coast near Portland. There's also an Australian oil/power
which has become a significant investor in OPT, and has secured the rights to
sell the Power Buoy in the region, through their
alternative energy subsidiary.
Is this the next wave, then?
As previously mentioned, wave power has great potential. In
some areas (map)
of the world, the ocean wave contains as much as 100kw of potential energy per
linear meter of wave-front. A look at the map also shows that it's generally
more widely dispersed over the world, although it does require coastline, heh.
Researching this article, I was impressed with the possibilities, and especially
with the Power Buoy. Unfortunately, some discrepancies have forced me to
conclude that, at least for the time being, this "breakthrough technology" may
need a few more years before it has a chance of becoming competitive.
Note how, in the
original article from Jan. 2003,
which I tantalizingly linked-to above, the reporter (Linda A. Johnson) states
that, "A total of six (Power Buoys) are to produce a combined 1 megawatt of
power," for the Hawaiian test. That's a much smaller number of buoys than was
at the time the project was announced. Originally, the Hawaii deployment called for 20 Power
Buoys, each producing 50kw of power. Unfortunately, I feel pretty certain that,
the real error in Johnson's report was leaving off a "0". The fact is that to
produce a megawatt of power will require at least 50 Power Buoys.
The problem, it seems, is that the estimates of the power production
capabilities of the Power Buoy are being, um, slightly overestimated. Studying
on the Power Buoy deployment reveals the true capacity of the Power Buoy to be
something in the neighborhood of 20 kilowatts, and not 50, and certainly
not 167, as claimed by Johnson, even in the most recent article.
Since this article was published, the Australian government has taken down their original report which I linked to above, related to the actual (20kw) output of the Power Bouy. However, you can still find the document on the Internet Archive.
Now, that's not to say that OPT's intentions aren't good. The Australian
report also notes that the company is "looking at developing" 100kw Power Buoys
in the future - but, and in spite of Robert's
claim that all of OPT's employees, "feel that they're doing something that may
be important to the world," I'm left slightly non-plussed by their chances.
Again though, their buoy is the clear winner for surviving bad weather, and some
of the design innovations, at least those that haven't already been patented,
will likely be copied, although others will likely be claimed as prior
innovation by non-American interests.
In any case, wave power isn't mentioned at all in the Bush report, and I'd like
to believe that it's got more potential than that, even in the US, where the
coastline doesn't have the wave-power potential that's found in other parts of
the world. The technology, otoh, at least for buoy-pump devices, still needs a
bit of work.
It is as yet rather difficult to find updates regarding progress made on
wave power during 2002, but the summaries and reports for 2001 are
interesting. A few of those are linked below.
- World Energy Council Survey of wave power
technology, as of late 2001. Includes a more complete look at the
Pelamis, as well as an overview by country of the research. (Mentions
Updates a review of Wind, Wave, Tidal and Solar power research from around
- Oceans of Electricity - a good review of the OWC
technology, as of late 2001. Includes coverage and references to the
deployed versions of the Oscillating Water Column technology.
- Scientific Applications
and Research, an organization which is also funded by the US Navy, has
which is interesting because the design has been awarded patents on certain
aspects of the technology. Unclear whether, or if OPT is utilizing any of this
design functionality. What is clear, is that the US Navy has a strong interest
in these devices.
of Edinburgh - Wave Power Group - academic home of some of the pioneers of
wave power technology.