Abstract:
An embodiment for generating energy from a fluid flow is proposed. A corresponding energy generation system includes energy conversion means, sail means switchable between an active condition for being carried away from the energy conversion means by the fluid flow and a passive condition for minimizing said carrying away, connection means for connecting the sail means to the energy conversion means, the energy conversion means generating said energy when the sail means in the active condition is carried away, return means for returning the sail means in the passive condition towards the energy conversion means, and switching means for switching the sail means to the passive condition and to the active condition in response to a maximum distance and to a minimum distance thereof, respectively, from the energy conversion means. In an embodiment, the sail means includes a pair of sail modules slidable along the connection means, each sail module being individually switchable between the active condition and the passive condition; the switching means then includes stopping means for each sail module, the stopping means being adapted to stop the sliding of the corresponding sail module in the active condition when carried away thereby causing the switching thereof to the passive condition, passive locking means for each sail module, the passive locking means being adapted to lock the corresponding stopped sail module in the passive condition, coupling means for sliding each sail module locked in the passive condition in opposition to the fluid flow to a standing position along the connection means by the other sail module in the active condition when carried away, and active locking means for each sail module, the active locking means being adapted to lock the corresponding sail module in the standing position thereby causing the switching thereof to the active condition after the unlocking from the passive condition.

Description:
PRIORITY CLAIM 
       [0001]    The present application is a national phase application filed pursuant to 35 USC§371 of International Patent Application Serial No. PCT/EP2009/060311, filed Aug. 7, 2009; which further claims the benefit of European Patent Application Serial No. 08425554.6 filed Aug. 8, 2008; European Patent Application Serial No. 09151327.5 filed Jan. 26, 2009; and European Patent Application Serial No. 09153560.9 filed Feb. 25, 2009; all of the foregoing applications are incorporated herein by reference in their entireties. 
     
    
     TECHNICAL FIELD 
       [0002]    An embodiment generally relates to the field of the generation of energy. More specifically, an embodiment relates to the generation of energy from a fluid flow. 
       BACKGROUND 
       [0003]    Different types of energy generation systems (or simply generators) are known in the art for generating energy (for example, of the electrical type) through the transformation of another type of energy; with reference in particular to the generation of energy from renewable energy sources, generators that exploit a fluid flow (for example, the wind) have attained an increasing attention in the last years. 
         [0004]    These (eolic) generators are commonly based on turbines (at horizontal axis), which are mounted atop vertical towers. Alternatively, generators based on parachutes have been proposed—for example, as described in U.S. Pat. No. 3,887,817, U.S. Pat. No. 4,124,182, U.S. Pat. No. 6,555,931, WO-A-2004/044418, and WO-A-2008/034421 (the entire disclosures of which are herein incorporated by reference). 
         [0005]    Generally, these generators are based on a parachute (or a similar element) that may be switched between a closed condition and an open condition (in which it is carried away by the wind or the water); a balloon may also be associated with the parachute, so as to maintain it lifted. The parachute and the balloon are connected to an energy converter at ground through a connection cable. The parachute is alternatively opened and closed. When the parachute is open, it is carried away from the converter by the wind (so as to generate the desired electrical energy); the parachute is then closed, and returned towards the converter (by exploiting a small fraction of the generated electrical energy). 
         [0006]    It is also possible to provide a pair of twin sections (each one including a parachute and a balloon), which are connected to each other by a single connection cable passing through an energy converter of the reciprocating type. In this case, the two parachutes are alternatively opened and closed. When a parachute is open, it is carried away from the converter by the wind (so as to generate the electrical energy); at the same time, it returns the other parachute towards the converter (without any waste of the generated electrical energy). 
         [0007]    The above-described generators have a low environmental impact, and they may be installed practically everywhere; moreover, these generators are simple, reliable and easy to maintain (and then very cost effective). Notwithstanding, the generators based on the parachutes provides a very high yield. Indeed, in this case it is possible to exploit the wind at a relatively high height from the ground. As it is known, the speed of the wind generally increases moving away from the ground; for example, at 800 m above the ground the wind has an average speed of 6-10 m/s for 5,000-7,000 hours a year (against an average speed of 4-5 m/s for 2,000-4,000 hours a year at 80 m above the ground). Since the power of the wind (which is transformed into electrical energy by the converter) depends on the third power (cube) of its speed, it follows that any (even small) increase of the speed of the wind moving away from the ground involves a very high increase of its power. 
         [0008]    However, a problem of the above-mentioned generators is the switching of the parachutes between their opening and the closing conditions. Indeed, these operations may require a relatively high energy, since at least one of them (for opening or closing the parachutes) has to be performed in opposition to the wind. 
         [0009]    For this purpose, it is possible to add driving cables (extending from the converter to each parachute), which are used to drive the opening and the closing of the parachute from the ground. A drawback of the driving cables is their complexity (because of the need of transmitting a high force at a high distance); moreover, the driving cables are prone to malfunctioning—for example, because they may twist with the connection cable. 
         [0010]    Alternatively, it is possible to mount a motor on board of each parachute. However, the motor typically must be relatively powerful, and then heavy (to provide the energy required to open and close the parachute). Therefore, the motor typically cannot be supplied with power locally neither by renewable energy generators—for example, solar panels (since they are typically unable to provide the required energy) nor by batteries (since their endurance is typically too low for practical applications). Conversely, if the motor is supplied remotely from the ground, a corresponding electrical cable extending from the converter to the parachute is required; this electrical cable may be dangerous—for example, in case of spikes or breaks thereof. 
         [0011]    An additional problem of the generators based on two sections is the high risk of twist of the corresponding portions of the connection cable that extends from the converter (with a consequent stopping of their operation). When this happens, it may be necessary to lower the parachutes to ground for disentangle the portions of the connection cable. However, this operation may be very complex and time consuming; moreover, the twist of the portions of the connection cable may bring about damages to the generator. 
       SUMMARY 
       [0012]    In its general terms, an embodiment is based on the idea of exploiting the fluid flow itself for the switching. 
         [0013]    An embodiment proposes an energy generation system for generating energy from a fluid flow. The system includes energy conversion means. The system further includes sail means, which is switchable between an active condition (for being carried away from the energy conversion means by the fluid flow) and a passive condition (for minimizing said carrying away). Connection means is provided for connecting the sail means to the energy conversion means; the energy conversion means generates said energy when the sail means in the active condition is carried away. Return means is instead used for returning the sail means in the passive condition towards the energy conversion means. The system then includes switching means for switching the sail means to the passive condition and to the active condition in response to a maximum distance and to a minimum distance thereof, respectively, from the energy conversion means. In an embodiment, the sail means includes a pair of sail modules that are slidable along the connection means; each sail module is individually switchable between the active condition and the passive condition. The switching means then includes stopping means for each sail module; the stopping means is adapted to stop the sliding of the corresponding sail module in the active condition when carried away, thereby causing the switching thereof to the passive condition. Passive locking means is also provided for each sail module; the passive locking means is adapted to lock the corresponding stopped sail module in the passive condition. The switching means further includes coupling means for sliding each sail module locked in the passive condition in opposition to the fluid flow to a standing position along the connection means by the other sail module in the active condition when carried away. Active locking means is also provided for each sail module; the active locking means is adapted to lock the corresponding sail module in the standing position, thereby causing the switching thereof to the active condition after the unlocking from the passive condition. 
         [0014]    Another embodiment proposes a corresponding method. 
         [0015]    A further embodiment proposes a computer program for performing a method. 
         [0016]    A still further embodiment proposes a corresponding computer program product. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    One or more embodiments, as well as features and the advantages thereof, will be best understood with reference to the following detailed description, given purely by way of a non-restrictive indication, to be read in conjunction with the accompanying drawings (wherein corresponding elements are denoted with equal or similar references and their explanation is not repeated for the sake of brevity). In this respect, it is expressly intended that the figures are not necessary drawn to scale (with some details that may be exaggerated and/or simplified) and that, unless otherwise indicated, they are merely used to conceptually illustrate the structures and procedures described herein. Particularly: 
           [0018]      FIG. 1A-FIG .  1 D illustrate operation of an energy generation system wherein an embodiment may be applied, 
           [0019]      FIG. 2A-FIG .  2 I illustrate an example of operation of an embodiment, 
           [0020]      FIG. 3A-FIG .  3 E shows an exemplary implementation of an embodiment, 
           [0021]      FIG. 4  is a schematic representation of a particular of an energy generation system according to an embodiment, 
           [0022]      FIG. 5A-FIG .  5 D illustrate operation of another energy generation system wherein an embodiment may be used, and 
           [0023]      FIG. 6A-FIG .  6 D illustrate operation of an energy generation system according to an embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    With reference in particular to  FIG. 1A-FIG .  1 D, there is illustrated operation of an energy generation system, or generator,  100  wherein an embodiment may be applied. The generator  100  is used to generate energy (for example, of the electrical type) from the wind; the wind (pictorially represented at the reference  105 ) consists of a flow of air, which is substantially parallel to ground  110  (from the left to the right in the figure). 
         [0025]    For this purpose, the generator  100  includes a base  115 , which is installed on the ground  110 . An energy converter  120  is mounted on the base  115 . A connection cable  125  connects a parachute complex  130  (including a pair of parachutes) to the power converter  120 ; the cable  120  has a length (for example, 1,000-1,200 m) allowing the parachute complex  130  to reach a desired height above the ground  110  (for example, 700-900 m), and it is dimensioned so as to sustain the applied forces (for example, being made of 12 twisted ropes in Dynema SK75, with thermic treatment and polyurethane coating). A balloon complex  135  (for example, including a pair of aerostatic balloons) is associated with the parachute complex  130 , so as to maintain it lifted from the ground  110  even in the absence of the wind  105 . A controller  140  is arranged in the base  115  for controlling operation of the whole generator  100 ; particularly, the controller  140  monitors an extension of the cable  125  from the converter  120 , so as to measure a distance of the sail complex  130  from it. For example, the controller  140  is based on a microprocessor—with a control unit, a RAM being used as a working memory by the control unit, a flash E 2 PROM being used to store information to be preserved even when a power supply is off (particularly, a control program of the controller  140 ), a keypad, and a display. 
         [0026]    In operation according to an embodiment, starting from  FIG. 1A , when the parachute complex  130  is open (for example, with its upper parachute) the wind  105  carries the parachute complex  130  away from the converter  120  (towards the right in the example at issue). In this phase, the cable  125  is extracted from the converter  120  so as to accumulate energy (schematically represented with the lifting of a weight from the ground  110  in the figure); for example, the energy may be accumulated by unwinding the cable  125  from a rotor of an electrical generator (so as to apply a corresponding torque). 
         [0027]    Considering now  FIG. 1B , when the parachute complex  130  reaches a maximum distance from the converter  120  (for example, approximately 800-1,000 m) it is closed, so as to minimize its carrying away by the wind  105 . The energy that was accumulated in the previous phase is now used by the converter  120  for returning the parachute complex  130  towards the converter  120  (schematically represented with the lowering of the weight to the ground  110  in the figure). However, the energy that is wasted for returning the parachute complex  130  towards the converter  120  is only a small fraction of the accumulated energy (since the drag that is opposed by the parachute complex  130  is now very low); therefore, a net result of the above-described two phases provides a surplus of energy that is used by the converter  120  to generate electrical energy. 
         [0028]    Moving to  FIG. 1C , when the parachute complex  130  reaches a minimum distance from the converter  120  it is open again (with its lower parachute now); for example, the minimum distance is equal to approximately 0.3-0.7, for example approximately 0.4-0.6, such as equal to approximately 0.5 times the maximum distance (for example, approximately 400-500 m). The same operations described above are then repeated. Particularly, the parachute complex  130  is carried away by the wind  105 , and the cable  125  is extracted from the converter  120  so as to accumulate energy. 
         [0029]    Likewise, as shown in  FIG. 1D , when the parachute complex  130  reaches the maximum distance it is closed; the energy that was accumulated in the previous phase is again used by the converter  120  for returning the parachute complex  130  towards the converter  120  (in a small fraction) and for generating electrical energy. When the parachute complex  130  reaches the minimum distance again, it is open (with its upper parachute), so as to return the generator  100  to the situation shown in  FIG. 1A  (with the same operations described-above that are repeated continually). 
         [0030]    This structure of the generator  100  (based on a single cable) is very simple and safe. 
         [0031]    In an embodiment, the opening and closing of the parachute complex are performed by exploiting the wind itself. Particularly, an example of operation of an embodiment is illustrated in  FIG. 2A-FIG .  2 I. 
         [0032]    For this purpose, the parachute complex is formed by a downstream parachute  230   d  and an upstream parachute  230   u  (with respect to the wind, flowing from the left to the right in the figure). Likewise, the balloon complex is formed by a downstream balloon  235   d  for the parachute  230   d  (fixed at a free end of the cable  125 ) and an upstream balloon  235   u  for the parachute  230   u  (fixed to the cable  125  between the balloon  235   d  and the converter, not shown to the left of the figure—for example, at 5-10 m from the balloon  235   d ); the parachute  230   u  is arranged upstream the balloon  235   u,  and the parachute  230   d  is arranged upstream the balloon  235   d  (downstream the balloon  235   u ). A latch  240   u  for the parachute  230   u  is arranged upstream the balloon  230   u,  and a latch  240   d  for the parachute  230   d  is arranged upstream the balloon  230   d  (downstream the balloon  235   u )—for example, 5-10 m before the respective balloons  235   u  and  235   d.  The parachute  230   u  and the parachute  230   d  may slide along the cable  125  (between the latch  240   u  and the balloon  235   u  and between the latch  240   d  and the balloon  235   d,  respectively). A coupling mechanism  245  (including a cable with a pulley system) couples the parachutes  230   u  and  230   d.    
         [0033]    Starting from  FIG. 2A , the parachute  230   u  is locked to the latch  240   u,  so as to prevent its sliding along the cable  125  and then maintain it open; the parachute  230   d  is instead locked in the closed condition around the balloon  235   d.  In this phase, the wind carries away the parachute  235   u  and then the cable  125  so as to accumulate energy. 
         [0034]    Considering now  FIG. 2B , the parachute  230   u  is unlocked from the latch  240   u;  the wind then makes the parachute  230   u  slide along the cable  125  (towards the right). At the same time, the parachute  230   u  pulls the parachute  230   d  in opposition to the wind through the coupling mechanism  245 , so as to cause its sliding along the cable  125  in the opposite direction (towards the left). 
         [0035]    As shown in  FIG. 2C , when the parachute  230   u  reaches the balloon  235   u , the parachute  230   u  overturns and folds around the balloon  235   u  so as to close. 
         [0036]    Moving to  FIG. 2D , the parachute  230   u  is then locked in the closed condition; at the same time, the parachute  230   d  reaches the latch  245   d  and it is locked thereto. In this phase, the cable  125  may be returned to the power converter, since both the parachutes  230   u  and  230   d  are closed. 
         [0037]    With reference to  FIG. 2E , the parachute  230   d  is unlocked from the closed condition (but remaining locked to the latch  240   d ); as a consequence, the wind overturns the parachute  230   d.    
         [0038]    Therefore, as shown in  FIG. 2F , the parachute  230   d  opens, so as to return the generator to the same situation of  FIG. 2A  with the parachutes  230   d  and  230   u  in opposite conditions (i.e., the parachute  230   d  being open and the parachute  230   u  being closed); as above, the wind carries away the parachute  230   d  and then the cable  125  so as to accumulate energy. 
         [0039]    The same operations are then repeated in a dual manner. Considering in particular  FIG. 2G , the parachute  230   d  is unlocked from the latch  240   d  (so that the wind makes it slide along the cable  125 ). At the same time, the parachute  240   d  pulls the parachute  230   u  in opposition to the wind through the coupling mechanism  245 , so as to cause its sliding along the cable  125  in the opposite direction. 
         [0040]    As shown in  FIG. 2H , when the parachute  230   d  reaches the balloon  235   d , the parachute  230   d  overturns and folds around the balloon  235   d  so as to close. 
         [0041]    Moving to  FIG. 2I , the parachute  230   d  is then locked in the closed condition; at the same time, the parachute  230   u  reaches the latch  240   u  and it is locked thereto. In this phase, the cable  125  may again be returned to the power converter, since both the parachutes  230   u  and  230   d  are closed. The parachute  230   u  is then unlocked from the closed condition (but remaining locked to the latch  240   u ); as a consequence, the wind overturns and opens the parachute  230   u  so as to return the generator  100  to the situation shown in  FIG. 2A  (with the same operations described-above that are repeated continually). 
         [0042]    An embodiment exploits the wind itself both to open each parachute (once it has been unlocked from the corresponding latch after being returned downstream by the other parachute) and to close it (against the corresponding balloon). Therefore, a desired result is achieved without any complex structure (for example, driving cables from the ground or motors on board of the parachutes). 
         [0043]    This strongly simplifies the generator (with a corresponding reduction of its costs); the simplification of the generator also increases its reliability. Moreover, it may be possible to avoid the use of any risky component (such as electrical cables from the converter to the parachutes). 
         [0044]    It is noted that the active actions that are now used to open and close the parachutes (for example, to unlock them from the corresponding latches or from the closed condition) only require a very low energy (since the actual operations of opening and closing the parachutes are instead performed by the wind). Therefore, the corresponding mechanisms that may be installed on board of the parachutes are very simple and light (so that they may be supplied locally—for example, by renewable energy generators or by batteries); moreover, this allows the use of very large parachutes, which may generate a high amount of energy per generator (for example, of the order of some hundreds of megawatts (MW) to some gigawatts (GW)). 
         [0045]    An exemplary embodiment is shown in  FIG. 3A-FIG .  3 E. 
         [0046]    In detail (see  FIG. 3A ), each parachute  230   d,    230   u  includes a sail  305   d ,  305   u  (for example, of the round type with a diameter of approximately 8-15 m for a balloon  235   d,    235   u  with a diameter of approximately 5-8 m). The sail  305   d,    305   u  is provided with an apical hole  310   d,    310   u,  which allows its sliding along the cable  125 . The apical hole  310   d,    310   u  may be associated with a screw, which rotates the sail  310   d,    305   u  when it slides along the cable  125  (clockwise or counter-clockwise); this increases the drag of the sail  310   d,    305   u  when it is carried away by the wind (for example, by approximately 15-30%), with a corresponding increase of the yield of the generator. 
         [0047]    Suspension lines  315   d,    315   u  (for example, approximately 4-20) extend from a border of the sail  305   d,    305   u  to a collector  320   d,    320   u  (for example, a bush), which may slide along the cable  125  as well. The parachute  230   d,    230   u  is locked to the latch  240   d,    240   u  by locking the collector  320   d,    320   u  thereto; the parachute  230   d,    230   u  is instead locked in the closed condition by locking the collector  320   d,    320   u  to the apical hole  310   d,    310   u.  For this purpose, in an embodiment a ratchet is associated with the latch  240   d,    240   u  and another ratchet is associated with the apical hole  310   d,    310   u.    
         [0048]    In detail, as shown in  FIG. 3B , a generic ratchet  325  (for either the latch or the apical hole) includes a gearwheel  330  that is fixed to the latch or the apical hole. A constraining cable  335  extends between the gearwheel  330  and the collector, generically denoted with the reference  320  (being provided with a spacer projecting laterally from the cable  125 ); the gearwheel  330  is spring biased so as to wind the cable  335  around it (counter-clockwise in the example at issue). The ratchet  325  also includes a pawl  340  (which is likewise fixed to the latch or to the apical hole); the pawl  340  is spring biased to engage the gearwheel  330 , so as to prevent its rotation clockwise, and then the unwinding of the cable  335 . A relay  345  disengages the pawl  340  from the gearwheel  330  in response to a remote unlocking command (received from the controller of the generator). 
         [0049]    Moving to  FIG. 3C , when the collector  320  moves towards the ratchet  325  (because the parachute is pulled towards the latch by the other parachute or because the sail is folded around the balloon by the wind), the cable  335  thus winds around the gearwheel  330  (which rotates counter-clockwise freely). However, after the collector  320  has reached the ratchet  325 , the cable  335  may not unwind (since the pawl  340  prevents the rotation clockwise of the gearwheel  330 ), so that the collector  320  is maintained in this position (i.e., locked to the latch or in the closed condition). 
         [0050]    With reference now to  FIG. 3D , when the relay  345  receives the unlocking command, the pawl  340  disengages from the gearwheel  330 . 
         [0051]    In this condition, as shown in  FIG. 3E , the gearwheel  330  is free to rotate counter-clockwise, so that the collector  320  may move away from the ratchet  325  by unwinding the cable  325  (because the parachute is carried away from the latch or because the sail is carried away from the collector by the wind). 
         [0052]    The proposed implementation only uses a relay  345  to unlock the parachute from the latch (to cause its opening after reaching the balloon) or to unlock the parachute from the closed condition (to cause its opening). Therefore, the relay  345  may be supplied by a simple system that is installed on board of the parachute (for example, a battery, a photo-voltaic generator, or a small dedicated eolic generator). Moreover, the control of the ratchet only involves the sending of simple unlocking commands; therefore, these unlocking commands may be transmitted from the ground—for example, with a wireless connection (so as to avoid the addition of any auxiliary cable). 
         [0053]    With reference now to  FIG. 4 , there is shown a schematic representation of a particular of the generator according to an embodiment. 
         [0054]    In detail, the converter  120  includes a drum  405  for winding the cable  125 . A guide  410  is used to maintain the cable  125  within the drum  405  with a correct slanting. For this purpose, the guide  410  includes a pair of idle rollers  415   a,    415   b  and another pair of idle rollers  420   a,    420   b;  the idle rollers of each pair  415   a,    415   b  and  420   a ,  420   b  are parallel to each other (for example, at approximately 5-10 cm). The idle rollers  415   a,    415   b  are arranged transversally to the idle rollers  420   a,    420   b;  in this way, a passage for the cable  125  is formed between the idle rollers  415   a,    415   b  and between the idle rollers  420   a,    420   b.    
         [0055]    In this way, the cable  125  may slant with respect to the ground  110  in whatever direction; moreover, the idle rollers  415   a,    415   b,    420   a  and  420   b  avoid (or at least substantially reduce) any wear of the cable  125  (which would instead be caused by the friction thereof against a fixed guide). 
         [0056]    Moving to  FIG. 5A-FIG .  5 D, there is illustrated operation of another generator (denoted with the reference  500 ) wherein an embodiment may be used. Particularly, the generator  500  includes an energy converter  520  of the reciprocating type (mounted on the same base  115  but with a different controller  540 ); for example, the generator  520  includes a mechanism for converting the movement of a rotor in both directions into a unidirectional rotation that is used to generate electrical energy. In this case, the generator  500  includes two twin sections, each one being formed by a parachute complex  530   a,    530   b  and a balloon complex  535   a,    535   b  as above; in this case, however, a (single) cable  525  connects the parachute complex  530   a  and the parachute complex  530   b  to each other through the converter  520 . 
         [0057]    In operation, starting from  FIG. 5A , when the parachute complex  530   a  is open (with its upper parachute) the wind  105  carries the parachute complex  530   a  away from the converter  520 . In this phase, the cable  525  pulls the other parachute complex  530   b  that is closed towards the converter  520 . However, as above the energy that is wasted for pulling the parachute complex  530   b  towards the converter  120  is only a small fraction of the energy that is produced by the parachute complex  530   a  being carried away by the wind; therefore, a net result of this phase provides a surplus of energy that is used by the converter  520  to generate electrical energy. 
         [0058]    Considering now  FIG. 5B , when the parachute complex  530   a  reaches the maximum distance it is closed; at the same time, the parachute complex  530   b  reaches the minimum distance, so that it is open (with its lower parachute). The two parachute complexes  530   a  and  530   b  then invert their function. Particularly, the wind  105  now carries the parachute complex  530   b  away from the converter  520 , and the cable  525  pulls the parachute complex  530   a  towards the converter  520  (with the resulting surplus of energy that is again used by the converter  520  to generate electrical energy). 
         [0059]    Moving to  FIG. 5C , when the parachute complex  530   b  reaches the maximum distance and the parachute complex  530   a  reaches the minimum distance, the parachute complex  530   b  is closed and the parachute complex  530   a  is open again (with its lower parachute now). The same operations described above are then repeated. Particularly, the parachute complex  530   a  is carried away by the wind  105 , and the cable  525  pulls the parachute complex  530   b  towards the converter  520  (with the resulting surplus of energy that is used by the converter  520  to generate electrical energy). 
         [0060]    Likewise, as shown in  FIG. 5D , when the parachute complex  530   a  reaches the maximum distance and the parachute complex  530   b  reaches the minimum distance, the parachute complex  530   a  is closed and the parachute complex  530   b  is open again (with its upper parachute now); therefore, the parachute complex  530   b  is carried away by the wind  105 , and the cable  525  pulls the other parachute complex  530   a  towards the converter  520  (with the resulting surplus of energy that is used by the converter  520  to generate electrical energy). When the parachute complex  530   b  reaches the maximum distance and the parachute complex  530   a  reaches the minimum distance, the parachute complex  530   b  is closed and the parachute complex  530   a  is open (with its upper parachute), so as to return the generator  500  to the situation shown in  FIG. 5A  (with the same operations described-above that are repeated continually). 
         [0061]    The generator  500  provides a higher energy yield (since it exploits the wind  105  itself to return the parachute complexes  530   a  and  530   b  towards the converter  520 , without any waste of the produced energy). 
         [0062]    With reference now to  FIG. 6A-FIG .  6 D, there is illustrated operation of another generator (denoted with the reference  600 ) according to an embodiment. Particularly, the generator  600  has the same structure as above, with a different base  615  (and a corresponding controller  640 ); particularly, the base  615  is now installed at the ground  110  so as to be free to rotate around a vertical axis. 
         [0063]    Starting from  FIG. 6A , when the parachute complex  530   b  is closed, a terminal portion of the cable  525  associated with it extends substantially in vertical from the converter  520 , because of the buoyancy of the balloon complex  535   b  (being the action of the wind  105  on the balloon complex  535   b  is assumed to be negligible in this example). Instead, when the parachute  530   a  is open (with its lower parachute), a terminal portion of the cable  525  associated with it is slanting from the converter  520  in the direction of the wind  105 , because of its action on the parachute complex  530   a.    
         [0064]    Considering now  FIG. 68 , when the parachute complex  530   a  reaches the maximum distance it is closed. The parachute complex  530   b  instead remains closed. Particularly, in an embodiment the parachute complex  530   b  reaches the converter  520  and it is locked in this position for a while; in this way, it may be possible to perform fast operations on the corresponding section of the generator  600  (for example, to inflate the balloon complex  535   b,  to recharge batteries being used to supply the relays of the ratchets, and the like). 
         [0065]    In this condition (possibly after the unlocking of the parachute complex  530   b  from the converter  520 ), the buoyancy of the balloon complex  535   b  (acting vertically upwards) is completely applied to the cable  525  (arranged in the same direction); conversely, only a component of the (same) buoyancy of the balloon complex  535   a  (again acting vertically upwards) is applied to the cable  525  (slanting thereto), while a remaining component of the buoyancy of the balloon complex  535   a  acts perpendicularly to the cable  525  (towards the converter  520 ). As a consequence, the parachute complex  530   b  lifts, since the upwards force (due to the buoyancy of the balloon complex  535   b ) exceeds the downwards force (due to the component along the cable  525  of the buoyancy of the balloon complex  535   a ); at the same time, the parachute complex  530   a  lowers approaching the converter  520  (because of the component perpendicular to the cable  525  of the buoyancy of the balloon complex  535   a ). 
         [0066]    As shown in  FIG. 6C , the parachute complex  530   b  is open (with its upper parachute) with a delay from the closing of the parachute complex  530   a.  For example, this delay is set to a predefined time interval (such as approximately 10-60 s); alternatively, the delay is defined by a predefined offset above the minimum distance (such as approximately 0.2-0.4 times the minimum distance, or approximately 80-160 m). For example, in this condition the parachute complex  530   b  is at a smaller distance from the converter  520 ; for example, the distance of the parachute complex  530   b  is equal to approximately 0.3-0.7, for example equal to approximately 0.4-0.6, such as equal to approximately 0.5 times the distance of the parachute complex  525   b  (for example, approximately 200-250 m). In this way, it is strongly reduced the risk of any twist between the terminal portions of the cable  525  associated with the two parachute complexes  530   a  and  530   b.    
         [0067]    As soon as the parachute complex  530   b  is open, the action of the wind  105  generates a torque (since it may never be perfectly aligned with the rotation axis of the base  615 ) that rotates the base  615  by approximately 180° around its vertical axis; consequently, as shown in  FIG. 6D , the parachute complex  530   b  passes downstream and the parachute complex  530   a  passes upstream the wind  105 . In this way, the parachute complex  530   b  is carried away by the wind  105  (with the corresponding terminal portion of the cable  525  that slants from the converter  520  in the direction of the wind  105 ); at the same time, the cable  525  pulls the parachute complex  530   a  towards the converter  520  (with the corresponding terminal portion of the cable  525  that moves towards the vertical from the converter  520 ). In this way, the parachute complex currently open is always downstream the wind  105 , while the other parachute complex being closed is upstream (so as to further reduce the risk of any twist between the corresponding terminal portions of the cable  525 ). 
         [0068]    The same operations are then repeated in a dual manner for the other parachutes of each complex  530   a  and  530   b,  until the generator  500  returns to the situation shown in  FIG. 6A  (with the same operations described above that are repeated continually). 
         [0069]    Naturally, in order to satisfy local and specific requirements, a person skilled in the art may apply to the one or more embodiments described above many logical and/or physical modifications and alterations. More specifically, although one or more embodiments have been described with a certain degree of particularity, it should be understood that various omissions, substitutions and changes in the form and details as well as other embodiments are possible. Particularly, an embodiment may even be practiced without the specific details (such as the numerical examples) set forth in the preceding description to provide a more thorough understanding thereof; conversely, well-known features may have been omitted or simplified in order not to obscure the description with unnecessary particulars. Moreover, it is expressly intended that specific elements and/or method steps described in connection with any embodiment of the disclosed solution may be incorporated in any other embodiment as a matter of general design choice. 
         [0070]    For example, similar considerations apply if the generator has a different structure or includes equivalent components (either separate to each other or combined together, in whole or in part). 
         [0071]    Particularly, an embodiment may also be applied to generate energy from any other fluid flow (for example, steams or tides of water). Likewise, the fluid flow may be converted to any other type of energy (for example, by compressing a gas). Moreover, similar considerations apply if the parachutes have a different shape (for example, of the square type), of if they are replaced with equivalent means based on generic sails (for example, kites, paragliders, wings, drogues); in any case, the parachutes may be switched between similar active and passive conditions (wherein the carrying away by the wind is generically higher in the active condition than in the passive condition—for example, with a Cx=approximately 0.8-1 and a Cx=approximately 0.1-0.3, respectively). The connections cable (between the parachutes and the convert) may be replaced with an equivalent element (for example, a chain). Likewise, it may be possible to return the parachutes in the closed condition towards the converter with other systems (for example, a biasing spring acting on the drum of the converter, or an auxiliary motor that acts on this drum). Naturally, the above-mentioned values of the minimum distance and maximum distance are merely illustrative, and they should not be interpreted in a limitative manner. 
         [0072]    Even though in the preceding description reference has been made to a specific mechanism for opening and closing the parachutes, nothing prevents applying a same embodiment to equivalent structures; for example, the sails may slide along the cable externally thereto (only through the collector), or the parachutes may lock to the cable directly (without any additional latch). 
         [0073]    A basic implementation of an embodiment without any balloons (or equivalent support elements for the parachutes) is not excluded—for example, in the water. 
         [0074]    It may also be possible to provide a single balloon for each pair of parachutes; moreover, the use of dedicated stopping elements (for causing the closing of the parachutes independently of the balloons) may be practicable. 
         [0075]    In any case, the balloons may have any shape (for example, spherical or elongated), and more generally they may be replaced with any other element capable of self-moving the parachutes away from the converter (for example, sinkers in the water). 
         [0076]    Alternatively, nothing prevents requiring an active command to lock the parachutes in the closed condition and/to along the cable as well. 
         [0077]    Naturally, the ratchets may have any other structure (for example, based on racks instead of the gearwheels), or they may be replaced with equivalent structures. 
         [0078]    Similar considerations apply if the generator is controlled in a different way (for example, by local controllers installed directly on board of the parachutes). 
         [0079]    In an embodiment, the maximum distance and the minimum distance may be detected in another way—for example, by means of altimeters mounted on board of the balloons. 
         [0080]    The proposed guide for the connection cable is not strictly necessary, and it may be omitted in a basic implementation of an embodiment. 
         [0081]    The generator with two sections as well may have a different structure or include equivalent components (for example, the rotatable base). 
         [0082]    Additional or alternatives parameters may be taken into account to trigger the opening of each parachute complex (with a delay from the closing of the other parachute complex); for example, for this purpose it may be possible to measure an altitude of the balloons, a slanting of the connection cable, a force of the wind, and the like. In any case, the above-mentioned values of the delay are merely illustrative, and they should not be interpreted in a limitative manner. In addition, it may also be possible to act on the connection cable (by the converter working as a motor) to facilitate the lifting of the parachute complex to be opened. 
         [0083]    Nothing prevents using a stationary base in the generator with the delayed opening of the parachute complexes as well (for example, with the two sections thereof that are arranged transversally to the wind). 
         [0084]    Vice-versa, it is noted that the delay of the opening of the parachute complexes, as well as the corresponding additional features (for example, the stop of the parachutes at ground, the rotation of the base, and the like) may be suitable to be used (alone or combined with each other) even without the specific mechanism for opening and closing the parachutes (exploiting the wind) of an embodiment. 
         [0085]    Similar considerations apply if the rotation of the parachutes around the connection cable is achieved in a different way (for example, by means of a screw arranged on the collector)—even if this feature is not strictly necessary and it may be omitted in an embodiment. 
         [0086]    An embodiment may lend itself to be implemented with an equivalent method (by using similar steps, removing some steps being non-essential, or adding further optional steps); moreover, the steps may be performed in a different order, concurrently or in an interleaved way (at least in part). 
         [0087]    In addition, the generator may be controlled by any other device (configured through a corresponding program). In any case, the program may take any form suitable to be used by any data processing system or in connection therewith. Moreover, it may be possible to provide the program on any computer-usable medium; the medium may be any element suitable to contain, store, communicate, propagate, or transfer the program (for example, of the electronic, magnetic, optical, electromagnetic, infrared, or semiconductor type). In any case, an embodiment lends itself to be implemented even with a hardware structure (for example, integrated in a chip of semiconductor material), or with a combination of software and hardware. 
         [0088]    From the foregoing it will be appreciated that, although specific embodiments have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the disclosure. Furthermore, where an alternative is disclosed for a particular embodiment, this alternative may also apply to other embodiments even if not specifically stated.