We humans have been harnessing the energy in
flowing water for thousands of years. I'm sure we all know what a water wheel looks like, but just
in case anyone's missed it, here's one in action. Very quaint! Today flowing water in one form or
another accounts for about 16% of all electricity generation around the world. According to the
International Hydropower Association, the total installed capacity in 2019 was 1,308 gigawatts,
generating more than 4,300 terawatt hours of electricity. The vast majority of that power comes
from hydroelectric dams on large river systems, which have developed into extremely sophisticated
and efficient engineering marvels. But as we've discovered in previous videos on this
channel, those dams also come with significant environmental impacts upstream and downstream,
as well as greenhouse gas emissions from their construction, and from the reservoirs immediately
behind them. What we haven't been quite so successful at, at least not so far anyway, is
harnessing the almost unimaginable quantity of energy in our oceans. Wave and tidal power
does exist of course, but high costs and limited availability of suitable sites have hampered
progress towards large-scale implementation. That's been changing quite rapidly in recent years
though. New materials and turbine technologies are opening up a wider range of geographical
locations, suggesting the total availability of tidal power may be much higher than previously
assumed, and at a much more competitive cost with a far smaller environmental impact than large
hydroelectric dams. And at the end of April 2021 the world's most powerful tidal turbine, boasting
some pretty ground breaking design features, was launched off the east coast of Scotland. So
could this be the game changer that the tidal energy industry has been looking for? Hello and
welcome to Just Have a Think. One of the biggest criticisms of renewables like wind and solar
is of course the old bugbear of intermittency. That unpredictability is being addressed to a
large extent with modern energy storage solutions, many of which we've looked at on the channel,
but tidal energy has the great advantage of being entirely predictable and reliable, because
it's driven by our orbit around the sun, and more importantly by our planet's
rotation combined with the gravitational pull of our moon's orbit around us. All three of
those dynamics look set to stay pretty regular for several million years to come, so you can
see the appeal of using the tides to generate reliable renewable energy at potentially extremely
large scale. Plus ocean water is more than 800 times denser than air, so in theory you can
generate vastly more energy per unit volume by sinking a turbine under water than
you can from putting one up in the wind. The world's first large-scale tidal power
plant went into operation way back in 1966 at the Rance power station in Brittany in France.
That facility remained the largest in the world right up until 2011 when the Sihwa Lake
Tidal Power Station was built in South Korea. The 10 turbines there have a combined
generating capacity of 254 megawatts. Both those installations are examples of a tidal
barrage, otherwise known as a tidal range device. Essentially they're just dams, very similar to the
type seen on major rivers around the world, but instead of using the flow of a river, they exploit
the change in energy between high and low tides to turn their turbines and generate electricity.
They're very large and relatively expensive. They also have to be constructed in locations
like the mouth of an estuary where they can be permanently anchored to the land on either side.
And they can have similar environmental impacts to hydroelectric river dams. Tidal stream devices,
which you and I know better as tidal turbines, generally have far lower installation costs, much
greater flexibility of location, and are way less impactful on the local environment and ecology.
As a result, especially in more recent years, far more investment and development has been
focused on tidal turbines than tidal barrages. But unlike wind turbines where the classic
three-bladed design has been fairly widely accepted as the most efficient configuration,
especially at larger scale, there are still lots of different designs for tidal turbines, all vying
for supremacy in what is still a relatively young but potentially very lucrative industry. This
latest design is called the O2 tidal turbine. It's the product of 15 years of continuous development
from an Orkney-based engineering company called Orbital Marine Power. It was built at the
Forth Port quayside facility in Dundee Scotland and towed out on the 22nd of April, arriving two
days later at an interim commissioning location at Deer Sound, where it will undergo final testing
and tow trials before being taken to its final location at the European Marine Energy Centre,
or EMEC, in the Fall of Warness, in Orkney. In a recent BBC interview, Orbital's chief
executive Andrew Scott pointed out that Orkney was an ideal location to host the new turbine,
not just because that's where the company's headquarters are located, but also because Orkney
sits in some of the strongest currents in the world with sea conditions that can get fairly
ferocious. And that makes it an ideal location to test and develop these sorts of technologies,
which will ultimately have to stand the test of time in some of the most unforgiving environments
on earth. It's not the first machine from orbital to arrive at EMEC either. Two previous versions
have been tested there. The most recent of which was a full-scale prototype called the SR-2000,
which was put through its paces between 2016 and 2018. That trial delivered record-breaking
results as well as vital test data and operational experience that laid the groundwork for
this latest commercial scale evolution of the design concept. When it's fully operational
the O2 turbine will have a generating capacity of 2 megawatts - enough to power about 2 000
homes. The structure is made up of a 680 ton floating hull measuring 72 meters or 236 feet in
length. That's about the same size as a jumbo jet. Inside the hull is all the electrical equipment
to power the various systems, and attached to the sides of the hull are two 18 meter long pivoting
arms, each one supporting a 20 meter rotor with a sweep of 600 square meters. The whole thing is
held down to the seabed with a four-point mooring system using some pretty serious chains -
each one capable of suspending more than 50 double-decker buses. According to Orbital,
about 50% of the power available in the water column comes from the top third, and the currents
in Orkney can get up to four meters per second, so those rotors are well placed to capture
the full force of that tide to generate power. One of the smart innovations with this
system is that the pitch of the blades can be reversed between tides so they can rotate
whichever way the water is flowing. Electricity is transferred from the turbine via a dynamic
cable to the seabed and then through a static cable to the local onshore electricity network.
And thanks to another piece of very clever design, the rotor support arms can be lifted out of the
water in a sort of gull wing motion by a hydraulic actuated linkage system that makes the whole thing
much easier to tow using relatively small and inexpensive tug boats. And it also minimizes the
complication and cost of maintenance and repair. In fact that low cost simplicity was one of the
key objectives of the project. According to Scott, as a very rough comparison, if the cost of any
given maintenance job onshore is, say, one dollar then that same job could cost more like a hundred
dollars in an offshore location at the surface and perhaps as much as ten thousand dollars at the
bottom of the seabed. So investing in a very sophisticated hydraulic hinge system actually
makes good business sense in the long run. It's probably a bit of a stretch to refer to a
680 ton superstructure as a plug and play system, but there really is not much
more to the installation than towing the rig to site, connecting up the chains
and electrical cable and pressing the go button. There's none of the huge civil engineering works
or CO2 hungry concrete support structure or dams that you get with tidal barrages.
Orbital are now moving full steam ahead on the commercialization of the design, and
they're seeking market support to enable them to build and install multiple units right around the
UK coastline and potentially beyond that as well. Just like any other sustainable technology, tidal
power on its own can't solve all the problems we face as a result of the climate emergency, but
turbines like these could play a very important role in complementing existing wind and solar
installations as part of the overall strategy to help the UK to achieve its commitment to reach
net zero no later than 2050. Eighty percent of the materials are UK sourced and there'll be an
obvious boost to local employment through the long term operation of the turbines which means as well
as seizing an opportunity to become a world leader in tidal technology Orbital will also be playing
their part in supporting the UK's green recovery. And just last week the Perpetuus tidal energy
center on the Isle of Wight, which is right at the other end of the United Kingdom, announced
that they've now gained offshore consents to place tidal turbines in their surrounding waters and
they've signed an agreement with Orbital as part of a target deployment of 15 megawatts of tidal
power by 2025. That's potentially enough to run 14,000 homes. On the global stage there's
an estimated capacity of about 100 gigawatts available for tidal energy harvesting.
That's enough to power 80 million homes. If that potential was fully deployed then Orbital
reckon it represents an investment in equipment and services of about 430 billion dollars, not
to mention the raft of jobs around the world that the infrastructure would create. Now, as
I mentioned earlier, I should make clear that other flavours of tidal turbine are of course
available! But orbital look like they've solved a great many of the problems that have beset
previous attempts at large-scale tidal turbines, and this O2 floating rig may just have set
a new benchmark for marine power generation. If you've got views on tidal power in general,
or if you work in the industry or maybe even have direct experience working on this project, then
I'd love to hear from you in the comments section below. That's it for this week though. A big
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