Is it Worth it? Gargantuan Tools Needed to Make Use of the Sea’s Energy

Wringing electricity from the sea
is no small task. But as firms start to test their wave-energy harvesters in
the open ocean that could be about to change. Heaving water holds 40 times more
energy than air moving at the same speed, and sea states change more slowly
than breezes, making it easier for utilities to predict the availability of
energy. New Scientist reports on developments. Meanwhile, new in-depth analysis
by the Carbon Trust shows the UK’s best marine energy sites could generate electricity
at costs comparable with nuclear and onshore wind.

26 August 2011 by Phil McKenna

New Scientist

An explosion of designs for
harvesting wave energy could make the process competitive at last – and they’re
heading out to the ocean for testing

WRINGING electricity from the sea
is no small task. But as firms start to test their wave-energy harvesters in
the open ocean that could be about to change.

Heaving water holds 40 times more
energy than air moving at the same speed, and sea states change more slowly
than breezes, making it easier for utilities to predict the availability of
energy. Yet the tools needed to make use of the sea’s energy are gargantuan.

Pelamis Wave Power’s wave energy
device, P2, is a case in point. Currently stored at the Leith Docks in
Edinburgh, UK, it uses spools of steel cable several times human height, and
floats that are as big as a car. But this is just window dressing for the
machine itself: a red rig that looks like a 180-metre-long subway train.

Pelamis and Aquamarine Power,
also based in Edinburgh, are the big players in what remains a small industry
of generating energy from waves. Each is now fielding full-scale prototypes
that could make wave energy competitive in terms of cost with other renewable
energy sources, such as offshore wind.

Alongside them are dozens of
smaller competitors, building a menagerie of strange devices that they hope
will leapfrog ahead of existing machines in the race to provide inexpensive
power from the sea. “Wave energy has been talked about for hundreds of
years,” says Neil Kermode, managing director of the European Union-funded
European Marine Energy Centre (EMEC). “Now it’s actually starting to
happen.”

In the UK, the waters around the
Orkney Islands off northern Scotland, home to some of the world’s cruellest
weather, are used as EMEC’s proving grounds, as they offer a stiff test for
wave-energy devices. As Kermode puts it: “This is the playground for the
big boys.”

For all its impressive size, on
the inside the P2 looks more like a data centre than a ship’s hull. Duplicate
server racks, fibre-optic communication systems and emergency power supplies
allow programmers to upload software on the fly without interrupting power
production.

The P2 generates energy when its
large floating tubes, connected by hinged joints, bob in the waves, moving
hydraulic rams that pump high-pressure fluid to drive turbine. And while the
hardware has been upgraded from previous prototypes, it is the algorithm
controlling them that makes the difference. By decreasing resistance in the
rams when waves are small and increasing it when they are larger, the algorithm
maximises energy production in any sea state. As a result, the P2 produces 750
kilowatts of electricity – twice as much as prior prototypes.

“It’s the active control of
these algorithms that allows us to tune the machine to be in resonance
regardless of wave conditions,” says Pelamis engineer Ross Henderson.

Last month, Aquamarine Power
finished the construction of its second full-scale wave power device, the
Oyster 800. This consists of a hinged flap that sticks out of the water and is
pushed shut with each passing wave. When the flap moves, it drives hydraulic
pistons that deliver high-pressure water via a pipeline to an onshore turbine.
With an output of 800 kilowatts, the device is built to be 2.5 times as
powerful as its predecessor (see “The ocean is your oyster”).

“If you can get that sort of
level of performance improvement then the economics suddenly start to look a
lot more favourable,” says Stephen Wyatt, head of technology acceleration
at The Carbon Trust, a UK-government-funded organisation charged with
catalysing a low-carbon economy.

A study published by The Carbon
Trust in July estimated the cost of energy harvested from waves at 43 pence per
kilowatt-hour, or almost three times the cost of offshore wind. To become cost
competitive with other sources of renewable energy, companies will have to find
ways to squeeze more power out of their devices, says Wyatt.

Meanwhile, a host of start-up
companies are heading for EMEC’s “nursery” – a test facility built in
sheltered waters for designs that are not yet ready for the open ocean – each
hoping their device will be the next game changer.

One of the most promising,
according to a three-year study by The Carbon Trust, is Anaconda by Checkmate
Seaenergy, based in Sheerness, UK. This is a snake-like rubber tube filled with
water that floats just below the surface. As waves hit the front of the device
they squeeze the tube, creating a bulge of water that travels along it. When
the bulge reaches the end, the pressurised water drives a turbine.

An 8-metre long prototype has
been tested, but the firm says it will be several years before its full-scale
1-megawatt device, which would be 150 metres long, is ready.

An equally unusual machine, the
1600-tonne Penguin, will soon begin testing at EMEC. Built by Finnish company
Wello, the 500-kilowatt rig has an asymmetrically shaped hull that causes it to
roll, heave and pitch – much like the stilted stride of a penguin – with each
passing wave. The movement spins a flywheel inside the hull, driving a
generator.

With such devices arriving with
increasing frequency, it’s too early to tell which technology will win out in
the end. “That is part of the excitement,” Kermode says. “It may
be something completely new or variations on something we have already
seen.”

Source: www.newscientist.com

11 July 2011

Major three-year Carbon Trust
marine energy R&D programme sets course for future growth

New in-depth analysis published
today by the Carbon Trust shows the UK’s best marine energy sites could
generate electricity at costs comparable with nuclear and onshore wind1.  With continued and targeted innovation this
could be as soon as 2025, once cost reductions from deploying the first
gigawatt of energy devices have kicked-in.
In the future marine energy could provide a fifth of the UK’s
electricity needs.

Through its Marine Energy
Accelerator programme, the Carbon Trust has established that the costs for the
first wave and tidal energy farms will be around 30-40p/Kwh which is high,
relative to today’s more established low carbon technologies, such as offshore
wind.  These costs are broadly as
expected given the early stage of the technologies’ development.  Importantly the report concludes how with
continued and targeted innovation aggressive reductions in costs can be
achieved in the next ten years.  The
report also quantifies the amount of energy that can realistically be tapped
and sets out the actions now needed to set the industry on a path to commercial
success.

The analysis shows that wave
energy could generate 50 Terra Watt hours (TWh) of electricity per year,
equivalent to 13% of the UK’s power needs, and tidal stream 20.6 TWh per year
or 5% of UK power needs.  Between them
wave and tidal stream could generate more electricity than 12 large coal-fired
power stations.  The fast flowing tides
of the deeper areas of the Pentland Firth between the Scottish mainland and the
Orkneys alone could ultimately generate almost one third of all tidal stream
energy (6 TWh/year) and at an equivalent cost to nuclear and onshore wind.

Technology innovation will be
vital to tackle the harsher conditions which are encountered in the deeper
areas of the Pentland Firth.  With
targeted innovation energy generation costs for both wave and tidal stream
technologies could reduce to an average of 15 pence per kilowatt hour by 2025 -
equivalent to today’s cost of offshore wind energy.

The £3.5m Marine Energy
Accelerator has already driven innovation in key areas including device
deployment and mooring.  Just one of
these innovations, developed with Pelamis Wave Power, has projected savings of
£15m a year by 2020 through faster installation and connection of the device in
rougher weather conditions.

Benj Sykes, Director of
Innovations at Carbon Trust, said:

“Marine energy is one of the UK’s
most exciting green growth sectors and one where we have a real lead.  Wave and tidal stream could provide a fifth
of our electricity needs and be a major ‘made in Britain’ success.  The key players must now pull together to
tackle the next set of challenges and innovate to drive down costs.  Our Marine Energy Accelerator, working with
key industry players and Government, has shown that savings of tens of millions
of pounds are possible.”

Separate Carbon Trust analysis
has shown that the UK could capture just under a quarter of the global marine
energy market.  Equivalent to up to £76bn
to the UK economy by 2050, this growing sector could also generate over 68,000
UK jobs.

The latest analysis from the
Marine Energy Accelerator highlighted the following key areas for action:

Targeted innovation is needed to
drive cost reduction and de-risk the industry.
Project developers should engage in non-competitive R&D efforts to
tackle challenges and costs associated with array deployment, foundations and
electrical connections.

Government needs to provide a
stable revenue support framework and legislative backing through Strategic
Environmental Assessments to streamline the planning process for wave and tidal
energy farms.

Utilities and project developers
must continue to be more heavily involved in the industry which will generate
wider investor confidence.

Supply chain partners should look
to invest now to create market-leading positions.

Plans for grid connections to
areas of marine energy need to be expanded, specifically for the Pentland
Firth.

By working with device developers
and other key players, the Marine Energy Accelerator has successfully driven
forward innovation in the following areas to speed cost reductions:

Optimising the design of tidal
turbine blades which might otherwise be significantly over-engineered

Developing nylon (instead of
steel) ropes and gravity bag anchors for mooring devices

Developing novel ‘linear generators’
which would replace hydraulics meaning fewer moving parts and less maintenance

Developing new techniques to
enable the generating equipment in floating wave devices to be disconnected
from the main structure

Developing a unique technology
for connecting and disconnecting the Pelamis P2 from its mooring enabling
maintenance in rougher seas

Taking forward the engineering
and commercial development of two ‘next generation’ concepts (Minesto’s Deep
Green tidal energy device and Checkmate Sea Energy’s Anaconda wave energy
device) which hold potential for game changing reductions in the cost of
energy.

British companies such as
Pelamis, Aquamarine Power and Marine Current Turbines are leading the way in
deploying their technologies in UK waters, with six out of the eight full scale
prototypes in the world being installed here.
Almost half of Europe’s wave resources and over a quarter of its tidal
energy resources are to be found off the British coastline.

Source: www.carbontrust.co.uk