Waves of energy

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Waves of energy
TIDAL ENERGY | ENERGÍA DE LAS MAREAS
SIEMENS
Waves of energy
The generation of electricity from tidal flows requires robust, proven, available, and cost effective
technology. SeaGen-S 2MW, a Siemens project, is the most advanced, field proven tidal
generation system available. As the pioneer and first mover in tidal the energy sector, MCT have
developed and patented key features, that deliver commercially viable electricity generation.
W
hile solar and wind energy
plants are becoming increasingly widespread as a means of
obtaining green energy, there is one area
that remains unexploited and that has
great potential: energy from the sea.
Waves are caused by the wind blowing
on the open sea for hundreds or thousands of kilometres, transferring energy to
the ocean’s surface. Thanks to recent technological advances, this kind of renewable
energy could soon become a much more
viable option.
Today, renewable energies have become
a fundamental component of energy policy. The European Union (EU) has set itself
the ambitious objective of meeting 20%
of if its energy needs from these kinds of
energy sources by 2020.
Many advances have been made in the
quest for clean energy, which help to combat global warming and the limited supply
of fossil fuels. Energy from the sea is one
of the most efficient and powerful alternatives for obtaining energy from the natural
world. In fact the power of the tides is an
important force that has as yet not been
exploited.
According to the International Energy
Agency, the sea could generate over 93,000
terawatt hours (TWh) of power. The energy
generated by wave power plants all over
Oleadas de energía
Mientras que las plantas solares y eólicas
se están convirtiendo en una forma extendida para la obtención de energía verde,
existe una zona hasta ahora sin explotar
y que tiene un gran potencial: la energía
procedente del mar.
Las olas son el resultado del efecto del
viento soplando a lo largo de cientos o miles de kilómetros en mar abierto, lo que
origina una transferencia de energía hacia
la superficie del océano. Gracias a los recientes avances tecnológicos, este tipo de
energía renovable pronto podría significar
una opción mucho más viable.
Hoy en día, las energías renovables se
han convertido en un componente fundamental de la política energética. La Unión
Europea (UE) se ha marcado el ambicioso objetivo de conseguir que en 2020, el
50
20% del consumo esté basado en este
tipo de fuentes energéticas.
En la búsqueda de fuentes de energía
limpias, que permitan hacer frente al calentamiento global y la escasez de combustibles fósiles, son muchos los avances que
se han conseguido. Una de las alternativas
eficientes y más potentes para obtener
energía del entorno, es la que proviene del
mar. De hecho, la fuerza energética de las
mareas es un importante recurso aún por
explotar.
Según la Agencia Internacional de la
Energía, el mar puede generar más de
93.000 teravatios hora (TWh) de potencia.
En concreto, si nos referimos a la energía
generada por plantas mareomotrices en
todo el mundo se estima que rondan los
800 Teravatios hora (TWh) al año. Esto su-
the world is estimated somewhere around
800 terawatt hours (TWh) per year. This is
the same as almost 25% of the total energy
demand of Germany, and equivalent to 4%
of global consumption. The coastal regions
with the strongest ocean currents, such as
the United Kingdom, Canada, France and
Eastern Asia have great potential for using
this technology.
SeaGen: The world’s first wave
power plant
Wave power has the advantage of being
a perfectly controlled technology, generating large amounts of power in places
with large waves. As water has an energy
pone casi el 25% de la demanda total de
energía alemana y equivale a un 4% del
consumo mundial. Las regiones costeras
con fuertes corrientes marinas como en el
Reino Unido, Canadá, Francia y Asia oriental ofrecen gran potencial para la utilización de esta tecnología.
SeaGen: Primera planta
mareomotriz del mundo
La energía mareomotriz ofrece la ventaja de ser una tecnología perfectamente
controlada y que genera altos niveles de
potencia en emplazamientos con oleaje
elevado. Como la densidad de energía del
agua, en comparación con el viento, es
800 veces mayor, la generación de potencia es mucho más eficiente.
Desde el año 2008, la Bahía de Portaferry en Irlanda del Norte acoge la primera
planta de energía que es impulsada por el
flujo de las mareas y que proporciona electricidad a la red. La planta SeaGen de 1,2
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density 800 times greater than that of air,
it generates power much more efficiently.
Since 2008, Portaferry Bay in Northern
Ireland has been home to the first tidal
power plant that provides electricity to the
grid. The 1.2-MW SeaGen plant is sited
just a few hundred metres from the strait
that links the bay to the Irish Sea. Here,
as the tide rises, the water mass advances
over the facility at up to five metres per second, going out six hours later at the same
speed. The energy potential is enormous,
and the advantage is that the tidal currents
are predictable. The lunar calendar can be
used to calculate the speed of the tides on
each day of the week.
The plant produces 20 megawatts of
energy per hour, enough to supply clean
and efficient energy to 1,500 households.
The system has been developed by the
company Marine Current Turbines Ltd.,
which currently belongs to Siemens.
From a technological perspective, SeaGen looks like a wind turbine immersed in
MW está ubicada a unos pocos cientos de
metros del estrecho que une la Bahía con
el Mar de Irlanda. Allí, las masas de agua
avanzan con cada pleamar hasta cinco
metros por segundo sobre el proyecto natural para retirarse seis horas después con
la misma rapidez. Se trata de un potencial
energético enorme y cuenta con la ventaja
de que las corrientes marinas son predecibles. Según el calendario lunar, se puede
calcular la velocidad con la que actúan y el
día de la semana en el que ocurrirán.
La planta produce 20 megavatios de
energía cada hora, suficiente para abastecer a 1.500 hogares de manera limpia y
eficiente. El sistema ha sido desarrollado
por la empresa Marine Current Turbines
Ltd. que, actualmente, pertenece a la empresa Siemens.
Desde el punto de vista tecnológico,
SeaGen se parece a un aerogenerador sumergido en el agua. Se compone de dos
rotores que trabajan de manera similar
a un molino de viento pero que, debido
a la mayor densidad del agua, necesitan
de palas más pequeñas. Para minimizar
los costes de instalación, la estructura de
soporte o travesaño está instalada en una
estructura única.
Con el objetivo de utilizar las corrientes
marinas, las palas del rotor pueden girar
180 grados. Esto significa que el sistema
puede producir electricidad durante 20
horas al día independientemente de las
condiciones climáticas y de los costes de
energía primaria.
Durante el funcionamiento, los rotores se
encuentran tres metros por debajo del nivel
del agua. Pero para permitir un mantenimiento fácil y seguro, la traviesa se puede
elevar por encima del nivel del mar. Gracias
al elevador hidráulico, se ahorran cerca de
100.000 euros en mantenimiento. Es lo que
costaría contratar un barco especial que estuviera en condiciones de hacer emerger las
unidades de 27 toneladas.
El proyecto actual es sólo un punto de
partida. Siemens cree en el potencial de
las plantas de energía mareomotriz y sigue invirtiendo en esta tecnología junto
a sus socios. En este momento, se está
desarrollando una versión mejorada de
SeaGen de 2 MW en la que se utilizan las
sinergias con la división de energía eólica
de Siemens.
En el futuro, muchos componentes de la
planta, entre ellos engranajes y generadores, serán suministrados por unidades de la
compañía que proveen a los proyectos eólicos de la compañía. Además, los rotores
de la central mareomotriz tendrán pronto
tres palas en lugar de dos, en analogía con
los aerogeneradores. Esto permite una
marcha más tranquila de los rotores y las
cargas se distribuyen de manera óptima.
En los próximos años, está previsto que
Escocia y Gales construyan en sus costas
parques similares a SeaGen pero con cuatro y cinco turbinas, respectivamente.
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what it would cost to rent a special vessel
to haul out the 27-tonne units.
These system features have been fieldproven since installation in 2008, of the
commercial scale, SeaGen – S 1.2 MW grid
connected system. By 2012, SeaGen–S had
delivered ten times the amount of electricity to the grid than all other tidal devices
combined. Following MCT’s acquisition by
Siemens, SeaGen-S 2MW is being developed and tested to the highest production
standards, benefitting from Siemens world
class, delivery of renewable energy technology to global utilities. SeaGen-S 2MW
is designed around the principles of; CostEffectiveness, Availability, Proven Engineering and Environmental Responsibility.
Cost-Effectiveness
Each SeaGen-S 2MW device consists of
twin 1MW powertrains, delivering 2MW
of grid conditioned
electricity to the substation. This configuration reduces the cost per MW by minimising cabling and associated distribution
infrastructure. The pitch-controlled blades
and high efficiency powertrains, extract
the maximum energy from the available
tidal resource.
Specifications
Rotor
• Diameter: 20 m
• Swept area: 628 m2 for
2 rotors
• Rotor speed: 4 –11.5 rpm
• Power regulation: Active
blade pitch regulation
Transmission System
• Gearbox type: Planetary
• Gearbox cooling: Direct
to passing sea water
Mechanical brake
• Type: Hydraulically released
Generator
• Type: Asynchronous
• Nominal power: Rated
to provide 1,000kW into
grid export cable
• Voltage: 690 V
• Cooling system: Direct to
passing sea water
Monitoring system
• SCADA system: Web
based
• Remote control: Full
turbine control
the water. It is made up of two rotors that
work in a similar way to a windmill, but
that – due to the greater density of water
– have smaller blades. In order to minimise
the installation costs, the support structure
or beam is installed on a single structure.
The rotor blades can turn through 180
degrees in order to exploit marine currents. This means the system can produce
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Tower
• Type: Cylindrical tubular
steel
• Hub height: Tailored for
water depth/navigation
constraint issues
Operational data
• Cut-in tidal speed: 1 m/s
• Rated power at: 2.5 m/s
Weights
• Drive trains: 60 tons
• Tower: Site-specific
electricity for 20 hours per day, whatever
the weather conditions and primary energy costs.
While they are operating, the rotors are
three metres below water level. However, in order to simplify maintenance and
make it safer, the beam can be raised above sea level. Its hydraulic lift saves around
€100,000 in maintenance costs. This is
Availability
Building upon 1000’s of generating hours
from SeaGen –S 1.2MW, SeaGen-S 2MW
has matured its engineering for greater
reliability. With its unique raising mechanism allowing low cost and rapid access to
the powertrains, and power conditioning
and control systems in its tower, SeaGen-S
provides unparalleled maintainability and
unbeatable availability.
Proven Engineering
With 3GWh generated by 2012 and the system continuing in 24-7 operation, SeaGenS has proven its’ engineering way beyond
any competing device. Not only is the concept fully demonstrated, but the detailed
engineering design including longer-term
fatigue characteristics are now proven.
Environmental
In addition to producing zero-carbon
electricity, MCT is committed to ensuring
minimal impact on the environment from
installation and operation in sensitive coastal waters. An independent environmental
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monitoring programme was commissioned to study the installation and first three
years of operation of SeaGen 1.2 MW. In
2012 the studies concluded that, with the
mitigation in place, there had been “no
significant environmental impact”.
SeaGen-S 2MW
The SeaGen-S 2MW tidal generation system evolves the highly successful 1.2MW
SeaGen S device that has been operational
in Strangford Lough since 2008. With the
insight and experience gained from this
project, MCT has been able to optimise
the system design to deliver 2MW with
greater availability and at lower cost.
Rotor
The SeaGen S tidal turbine incorporates
twin horizontal axis rotors. The rotors utilise an active blade pitching system which
limit structural forces during high flow conditions. This allows the use of blades that
are highly efficient over the full range of
tidal velocities, from initial cut-in through
to rated flow. Energy capture is further enhanced by variable speed operation which
allows the turbine to operate at its optimum
tip speed ratio (all the way up to up to rated power) and also minimises the dynamic
loads on the transmission system. In summary, the variable speed and active pitch
features allow efficient energy capture over
the full range of tidal velocities and minimise
structural loading, weight and cost.
Blades
The highly efficient rotor blades are constructed from composite materials and
are the most advanced and tested blade
technology used in tidal generation. The
2MW design blades are being verified by
static and dynamic testing, building upon
25,000+ blade operating hours gained
during the 1.2MW SeaGen and SeaFlow
projects .
Rotor hub
The rotor hub houses the blade pitch actuators, slew bearings and automatic greasing system in a compact and easily maintainable configuration.
Blade pitch system
The blade pitch arrangement is used to optimize and regulate power output througenergética
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hout the operating range. The blades can be
feathered to minimize hydrodynamic loads
during extreme wave or tidal conditions.
Main shaft and bearing
The main shaft is forged in alloy steel and
is hollow for the
transfer of power and signals to the blade pitching system via slip rings.
Gearbox
The efficient and lightweight planetary
gearbox allows a very compact and light
power train to be realised. This simplifies
maintenance operations and support logistics as well as reducing overall structural weight and cost. The intermediary and
high speed stages are normal helical stages
arranged with an offset of the high-speed
shaft, allowing the passage of power and
control cables to the pitch systems. The
gearbox is equipped with large capacity filtering systems that ensure optimum
operating conditions and up to 12 months
of operation between filter changes. The
gearbox is fully sealed and is cooled by the
tidal flow.
Generator
The generator is a fully-enclosed asynchronous machine with squirrel-cage
rotor, which does not require slip rings
and is very robust. In addition to variable
speed operation, the use of frequency
converters enables the generator to achieve high part-load efficiency, allowing the
turbine to achieve high system efficiency
across the range of tidal flow velocities.
The generator is cooled naturally by the
water flow.
Mechanical brake
The system incorporates a hydraulically
realised brake which serves as a parking
brake for crossbeam lifting and maintenance operations, and is also used to ensure safe shut-down under some theoretical
fault conditions.
Controller
The turbine utilises a standard wind turbine control system provided by a leading
supplier. The controller is compatible with
turbine safety requirements, is selfdiagnosing and includes a keyboard and display
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tidal energy | energía de las mareas
for easy status readout and adjustment
of settings. The system allows; remote
interrogation, the reset of turbine alarms
and provides comprehensive data logging
functionality.
Power conversion
The power conversion system allows the
rotor to operate at optimal speed over the
range of tidal velocities (from initial cutin to rated power) whilst supplying grid
compatible electrical power at a frequency
and voltage to match the local distribution
network. The power conversion system is
a modular arrangement for easy maintenance. The frequency converter output
is interfaced to the grid via an onboard
transformer, protection switch and standard grid protection relay. Each SeaGen
device is a
self-contained power station, requiring
minimal onshore infrastructure and permitting multiple machines to use a common subsea cable.
Grid compliance
The SeaGen system complies with current
grid code requirements and due to the use
of modern frequency converters, can be
adapted to meet emerging standards and
network requirements associated with tidal arrays.
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Operation
The tidal turbine operates automatically,
self-starting when the tide reaches an average speed of about 1 m/s. During operation below rated power, the pitch angle
and rotor speed are adjusted to maximize
the hydrodynamic efficiency. Rated power
is reached at a tidal speed of about 2.5
m/s. At higher tidal speeds the output is
regulated at rated power and rated rotational speed.
Remote control
The tidal turbine is equipped with a web
based SCADA system. This system offers;
remote control, a variety of status views
and useful reports from a standard internet web browser. The status views present;
electrical, mechanical, meteorological and
tidal data, as well as operation, fault and
grid status.
Turbine Condition Monitoring
In addition to the Web SCADA system, the
turbine is equipped with a web-based Turbine Condition Monitoring (TCM) system.
The TCM system carries out precise, continuous, real time, condition diagnostics
on main turbine components. The TCM
system has various alarm levels, from informative through alerting level to turbine
shutdown.
Support Structure
The twin 1MW tidal turbine drive trains are
mounted at each end of a crossbeam which
in turn is supported by a surface piercing
tubular steel tower. The cross beam can be
raised, as required above the sea surface
to maintain the drive trains, avoiding the
cost and delay associated with expensive
marine vessels. MCT can provide support
to array developers to design foundations
to meet local site conditions.
The current project is only a starting
point. Siemens believes in the potential of
wave power plants and is continuing to invest in this technology along with its partners. At the moment it is developing an
improved 2-M version of SeaGen, which
will harness synergies with Siemens’ wind
energy division.
In future, many of the plant’s components, including gears and generators, will
be supplied by company units that currently
supply the firm’s wind power projects. In
addition, the rotors of the wave power
plant will soon have three blades instead of
two, just like wind turbines. This will enable
the rotors to turn much more smoothly, ensuring an optimal load distribution.
Scotland and Wales are expected to build
plants similar plants to SeaGen on their
coasts in coming years, but with four and
five turbines, respectively 7
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