Note: Descriptions are shown in the official language in which they were submitted.
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Wind Turbine Featuring Recirculation of a Cooling Stream
The invention relates to a wind turbine comprising a tower, a nacelle which is
arranged
on the tower, a power conversion unit which is arranged within the nacelle, a
rotor which
is connected to the power conversion unit and has at least one rotor blade
that is
connected to a hub, and a device which feeds fresh air from outside to a
chamber arranged
in the wind turbine and discharges used air from said chamber to the outside
in order to
cool wind turbine components that are arranged inside the chamber.
To prevent damaging the components of wind turbines, such as the gearbox, the
rotor
bearing, various hydraulic units, the rectifier, the transformer etc. as a
result of excessive
heating, it is requisite to dissipate the power loss of these components.
As is generally known, the power loss occurring in the form of heat is removed
as a rule
by an air stream that is carried in the wind turbine or by cooling liquids
cooled by air in a
heat exchanger that are brought to the corresponding components of the wind
turbine that
give off heat. In the process, fresh air guided into the wind turbine from
outside takes up
the dissipated heat directly at the components giving off the dissipated heat
or at the heat
exchanger elements of a cooling unit and is carried out of the wind turbine as
warm used
air that carries away the dissipated heat from the components or the heat
exchanger.
However in the case of wind turbines in particular in cold climate zones such
as Inner
Mongolia, in Siberia and also in Canada the problem can occur at least at
times that the
fresh air introduced into the wind turbine is at such a low temperature that
various
components of the wind turbine such as generator or the electronics are cooled
down to
such a low temperature critical for the operation of the components of the
wind turbine
that these components can fail or be damaged.
It is therefore generally known to control the inflow of the cold air into the
wind turbine
by means of an rpm controlled fan to prevent a lowering of the temperature
inside the
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wind turbine below a value that is critical for certain components that are
sensitive to
cold.
However it is here in particular problematic that the components that are
sensitive to cold
and those that are sensitive to hot are as a rule arranged together side by
side in the same
chamber or compartment of the wind turbine, e. g. in the tower, in the nacelle
or in the
chamber, and that in the case a flow velocity of the cold air through the
chamber in the
wind turbine is reduced as a result of a reduced fan rpm, sufficient
dissipation of the
dissipated heat from heat sensitive components cannot be ensured adequately.
The object of the invention is therefore to provide a wind turbine that can be
controlled,
using simple means, in particular in cold climate zones such that sufficient
cooling of
heat sensitive wind turbine components is ensured without lowering the room
temperature below temperature values that are critical for cold sensitive wind
turbine
components.
The object is achieved by means of the wind turbine having the features of
Claim 1. The
sub claims specify advantageous designs of the invention.
The basic idea of the invention consists in re-circulating a partial stream of
the fresh air
that has been warmed up by the heat given off by the components of the wind
turbine and
that is conventionally removed completely as used air from the wind turbine,
into the
chamber of the wind turbine so that the inflow of cold fresh air can be
determined by
means of the proportion of used air fed back into the chamber, fresh air and
used air can
be mixed together and a temperature that is critically low for the operation
of the wind
turbine can be avoided and still sufficient cooling is ensured.
The invention is explained in more detail using an exemplary embodiment that
is
illustrated in the drawings and is of particularly preferred design. In the
drawings
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Fig. 1 shows a perspective view of a wind turbine according to the
invention; and
Fig. 2 shows a schematic illustration of the circulating air inside the wind
turbine.
Fig. 1 shows a perspective view of a wind turbine 10 of particularly preferred
design. The
wind turbine 10 exhibits a tower 20, a nacelle 30 which is arranged on the
tower 20 and a
power conversion unit which is arranged (not visible) within the nacelle 30.
The power
conversion unit is connected to a rotor that has, in the example shown, three
rotor blades
50a, 50b, 50c connected to a hub 40, it being of no importance for carrying
out the
invention how many rotor blades are actually provided.
To cool the components arranged in one of the chambers provided in the wind
turbine 10,
e. g. gearbox, bearings, hydraulic units, rectifier, transformer, heat
exchanger etc., the
wind turbine 10 further exhibits a device that guides fresh air from outside
to a chamber
e. g. of the nacelle 30 and carries used air to the outside and that carries
away the
dissipated heat of the wind turbine components 60 arranged in the nacelle 30.
As an
alternative or in addition the wind turbine 10 can have further cooling
devices for the
same chamber or further chambers, e. g. the tower 20 or the hub 40. It is
possible that the
chamber occupies only a part area of the tower 20, of the nacelle 30 or of the
hub 40.
The device that guides fresh air to the chamber from outside and carries away
used air to
the outside can be designed as one or more simple inlet and outlet openings,
it being
possible to additionally provide a fan and various filters.
In the process the air streams of fresh air and used air are guided for
example as follows,
as shown schematically in Fig. 2. Cool fresh air is supplied from the outside
from the
surroundings of the wind turbine 10 to a component 60, e. g. the gearbox, the
generator, a
hydraulic positioning device or a heat exchanger, arranged in the chamber 100
of the
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wind turbine 10, e. g. tower 20, nacelle 30, or hub 40. The fresh air passing
by the
component 60 or flowing through the component 60 takes up the dissipated heat
given off
by the component 60 and is discharged from the inside chamber 100 of the wind
turbine
as used air to the outside surroundings.
5
According to the invention a positioning element 70 is now provided that is
actuated
manually or automatically and that guides a partial stream of the used air,
i.e. a partial
stream of the air carrying the dissipated heat of the component 60 with it,
back into the
chamber 100 of the wind turbine 10.
The positioning element 70 is now preferably designed such that the (volume)
fraction of
the partial stream in the entire used air can be determined, it being possible
for the
fraction of the partial stream to be 100% for example when starting the plant
at low
outside temperatures. At a time when there is no need for cooling, the
circulating used air
in the chamber 100 of the wind turbine 10 prevents fresh air from entering the
chamber
100. During further operation and with further heating up of the components
the fraction
of the partial stream in the entire used air is lowered to a lower value than
100% so that
part of the used air is discharged to the outside and cold fresh air is fed
into the chamber
100 as a result of the negative pressure generated by discharging the used
air. Warm used
air and cold fresh air that enters the chamber 100 then intermix, leading to a
room
temperature favourable for the operation of the plant when the fraction of the
fed-back
used-air partial stream is regulated in a suitable manner.
To this end finally there is also provided a control unit that acts on the
positioning
element 70 and controls the fraction of the partial stream in the entire used
air as a
function of various parameters. For example temperature sensors can be
provided on the
components 60 of the wind turbine that give off dissipated heat and/or in the
chambers
100 of the wind turbine 10, such as tower 20, nacelle 30 or hub 40, the
control unit
guiding the partial stream of the used air or - when providing several
positioning
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elements 70 - several used-air partial streams to the components 60 so that
their
temperature does not drop below a certain limit value.
The temperature limit value can here for example be determined individually
for each
single component, or for several components 60 arranged in an inside chamber
100 can
be that highest temperature value below which it may not fall for a specific
component 60
arranged therein.
In particular in the control unit a table of components 60 can be stored where
the
minimum and/or maximum permissible temperature value is arranged
hierarchically so
that that component 60 whose minimum or maximum permissible temperature value
is
exceeded or below which it falls, determines the fraction of the partial
stream of the used
air in the entire volume of the used air.
In the simplest case the positioning element 70 can be designed as an element
that
determines the cross section of the outlet intended for the used air (and also
of the inlet
provided for the fresh air to avoid too high overpressure in the wind turbine
10). However
the positioning element 70 can also be designed such that a partial volume of
the used air
is divided up into several partial streams while providing corresponding
ducts, and is
admitted to various components 60 of the wind turbine 10 in various fractions.
It is the advantage of the invention that wind turbines can also be operated
in extremely
cold climates without requiring - apart from the heating elements that are
provided as
absolutely necessary anyway - additional structures for heating components 60
of the
wind turbine 10 to prevent the temperature of the components 60 falling below
a critical
limit value during operation. In particular the invention enables a uniform
temperature
control of all critical areas inside the plant in a simple manner.
