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 thank you, as always, to the people who make these
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