Device for generating electric energy from a renewable source

A device for generating electric energy (1) from a renewable source, in particular from wave energy, comprising an oscillating device (2) that can transform the thrust of a natural agent on the first extremity of oscillating device (2) into kinetic energy; a motor unit, operatively connected to a second extremity of the oscillating device in such a way as to receive the kinetic energy transmitted by the oscillating device (2); and an electrical rotating machine operatively connected to the motor unit and suitable for producing electricity when it is set to rotating by the said motor unit.

This invention concerns a device for generating electric energy from a renewable source, in particular suitable for generating energy by exploiting the action of external agents, for example wave energy.

Devices suitable for these applications are characterised mainly by the fact that they guarantee users the possibility of exploiting renewable sources such as wave energy, without the need for mains electricity supply or having to depend on fuels not available in all situations and places, such as petrol, diesel or gas.

The widespread devices for this type of use exploit wave energy in different ways, all with view to starting up a generator for the production of energy.

Some of them are floating tubular structures anchored to the seabed. With the motion of the waves water enters and leaves these structures, activating special turbines.

Other devices are built on coastlines and consist of reinforced concrete structures with a special turbine installed in them.

In these devices the waves penetrate the reinforced concrete structures and compress the air inside which in turn activates the turbine.

However there are disadvantages in installing these devices.

Firstly, the types of devices envisaged for the open sea involve difficult installation and maintenance operations which are not always possible due to weather conditions.

The turbines associated with both offshore and coastal devices must be made of material with, respectively, high and medium levels of resistance to marine corrosion, with a consequent increase in costs.

Coastal devices moreover call for enormous reinforced concrete structures of questionable environmental impact.

Disadvantageously, these devices are of considerable bulk.

Disadvantageously, lastly, these devices are of limited yield and cannot adapt to different wave conditions.

The aim of this invention is to overcome the disadvantages prevailing in the state of the art.

This aim is achieved by an energy generating device according to claim1. The dependent claims describe preferred embodiments.

With reference to the above figures, the reference number1globally indicates a device for wave energy transfer.

According to a general embodiment, the device1comprises an oscillating device2with an extremity suitably profiled to receive the thrust of an external agent, such as a wave, and an opposite extremity which cooperates with a motor unit which is in turn connected to an electric machine.

In other words, the oscillating device is a lever that can transform the energy produced by the thrust of the external agent into kinetic energy suitable for advantageously moving the liquid that supplies a motor unit.

Rotation of said motor unit is then converted into electricity by the associated electric machine.

According to one advantageous embodiment, oscillating device2comprises a thrust lever4, fixed to a support frame40(illustrated inFIGS. 4 and 5) by rotation pin24.

The oscillating device2moreover comprises a scoop8, mounted at an extremity of thrust lever4and suitable for receiving the thrust of an external agent, and a return element9suitable for bringing the oscillating device back to the start stroke position.

The maximum travel of oscillating device2is limited by start stroke arrest20and end stroke arrest21, connected to support frame40.

The scoop8is formed in a substantially concave way with view to efficiently capturing the energy deriving from wave action.

In one embodiment, the oscillating device2is positioned in such a way that in the start stroke working position the concave part of scoop8is substantially positioned towards the direction of progress of the waves. In this case the oscillating device2can capture the action of the wave even when the waves are not very high.

In one further embodiment, the oscillating device2is oriented substantially in a horizontal direction in such a way that in the start stroke working position the concave part of scoop8is substantially parallel to the direction of progress of the waves. In this embodiment, advantageously, the scoop8is replaced by a float (FIG. 4) in such a way that the oscillating device2can function without the use of a return element inasmuch as it can follow the progress of the wave.

In one embodiment, the position of rotation pin24on the axis of thrust lever4is variable depending on the wave force acting on oscillating device2.

In other words, depending on sea conditions, by shifting the rotation pin the leverage ratio of oscillating device2is varied, with consequent variation of force intensity and therefore of the energy transmitted to the motor unit.

Advantageously, oscillating device2can vary in configuration depending on operative conditions, this with view to ensuring a constant yield and to avoiding structural damage in adverse operative conditions.

The return element9facilitates return of thrust lever4to start stroke position and is mounted on thrust lever4in a position opposite to the compression means6.

In an advantageous variant, return element9is a counterweight.

In one embodiment, counterweight9is mounted on thrust lever4in an overhanging manner, at a distance from the axis of thrust lever4that varies according to operative conditions.

In other words, on variation of sea conditions and/or variation of the leverage ratio of oscillating device2and/or variation of the width and therefore dimensions of scoop8, with view to rendering more efficient the return of thrust means2to the start stroke position, the return element9is mounted with a greater or lesser overhang according to the specific case.

In one embodiment, the return element9is an elastic element such as a spring.

Advantageously, the rigidity of the elastic element is variable according to operative conditions, with view to improving efficiency of the return of thrust means2to the start stroke position.

In one favoured embodiment, oscillating device2comprises a compression means6, mounted in a position opposite to scoop8and with a thrust surface10, substantially convex.

Said thrust surface10is the surface which, under operational conditions, engages the motor unit to transmit the kinetic energy generated by wave movement.

According to one favoured embodiment, the motor unit comprises a containment lung3, suitable for containing a fluid, for example air, or preferably a liquid, for example mineral oil, a turbine5, operationally hooked up to an electrical rotating machine and set in motion by the fluid under pressure from containment lung3, and a recovery tank7for recovering the fluid that passes through turbine5and for re-injecting it into lung3.

According to an advantageous embodiment, containment lung3is funnel shaped with the inlet section13greater than the outlet14. The extent of this difference determines the capacity of lung3to accelerate the fluid contained therein between inlet13and outlet14.

In other words, the greater difference there is between the sections of inlet13and outlet14, the greater the thrust given by lung3to the fluid it contains.

In yet other words, containment lung3functions as a pressure multiplier.

According to one embodiment, containment lung3comprises a bellows cylinder.

In any case containment lung3is fixed to the support frame in such a way that its inlet13is substantially opposite compression means6of thrust means2.

According to one embodiment, and especially in the case of the funnel conformation, in correspondence to inlet13the containment lung3is delimited by a yielding element15, for example a membrane.

Preferably the said yielding element15is engaged with inlet13in such a way as to ensure a seal and avoid leaks of fluid through the said inlet13.

Outlet14of containment lung3is in fluidic connection with turbine5.

According to one embodiment, at the exit of outlet of containment lung3there is at least one valve system22.

In one favoured embodiment the said valve system22is a unidirectional or non-return valve.

The containment lung3also comprises a lateral area16, for example of a substantially truncated-cone shape in the case of funnel conformation, between inlet13and outlet14.

The said lateral area16comprises an aperture17by means of which containment lung3is in fluidic connection with recovery tank7and in which there is at least one valve system23.

In one favoured embodiment the said valve system23is a runner valve.

In one further embodiment the said valve system23allows the said unidirectional passage of fluid only in the presence, preferably in containment lung3, of suitable operative conditions, for example in terms of pressure.

In other words, in one advantageous embodiment, the opening of valve system23takes place only when, in containment lung3, pressures are reached which substantially approximate to those recorded in appropriate functioning conditions, for example in conditions of start stroke of the device.

In yet other words, when pressure in containment lung3begins to increase, valve system3is in the closed position and does not allow fluid to pass; when the pressure diminishes, valve system3is in the open position and allows fluid to pass into containment lung3.

Containment lung3is in fluidic connection with turbine5by means of turbine inlet conduit18.

Turbine5is operatively connected with an electrical rotating machine, for example a dynamo or alternator, to which it transmits motion for the production of energy.

Turbine5is also in fluidic connection with recovery tank7by means of turbine outlet conduit19.

Recovery tank7is in fluidic connection with containment lung3by means of aperture17.

Recovery tank7is a tank in which the fluid from turbine5is recovered in order to be returned to containment lung3, thus permitting a new refilling.

With reference toFIGS. 1 and 2, the functioning method of this invented device is illustrated below.

Considering the device at the start stroke working position, initially an external agent, for example a wave, exerts a thrust on the concave part of scoop8of oscillating device2.

Due to the thrust exerted on scoop8, the oscillating device2rotates and transmits captured kinetic energy to compression means6.

Thrust surface10of compression means6exerts pressure on membrane15of containment lung3, deforming it and preferably taking it from start stroke configuration15ato end stroke configuration15b.

The gradual deformation of membrane15, from position15ato position15b, induces a gradual increase of pressure in the fluid in containment lung3.

The said increase of pressure causes closure of valve system23, forcing the fluid through outlet14.

The fluid, having passed through outlet14, passes through unidirectional valve22and, by way of a turbine inlet conduit, is conveyed to the blades of turbine5.

The fluid then acts on the blades of turbine5, making them rotate.

The said blades, rotating, start up the electrical machine, operatively connected to the turbine, which thus produces electricity.

Preferably the fluid, having complete its function of thrust on the turbine blades, leaves the turbine and is conveyed to recovery tank7by way of the turbine outlet conduit19.

When the wave thrust is over, the oscillating device2, with the aid of return element9, returns towards the start stroke position until it contacts start stroke arrest20.

During the return stroke of oscillating device2, in other words when the thrust is over, the pressure in containment lung3decreases, returning to values substantially close to those recorded in the start stroke condition.

The said diminution of pressure causes opening of valve system23with subsequent outflow of fluid from recovery tank7to containment lung3, permitting a refilling thereof.

The device, having returned to the start stroke configuration, is activated by another wave and repeats the cycle.

According to an advantageous variation of embodiment, the motor unit described above comprises an expansion tank30, operatively connected with the turbine and positioned, for example, between outlet14and the said turbine5, but in any case after non return valve22.

The said expansion tank30collects a part of the fluid compressed during the initial phase of functioning, which is to say during the phase in which the oscillating device compresses the fluid in the containment lung and then releases it during the subsequent phase of decompression, i.e. during the phase in which the oscillating device, with thrust exhausted, tends to return to the initial configuration.

The said released fluid is conveyed to the turbine and has an energy such as to permit its motion.

Advantageously, the expansion tank ensures continual functioning of the turbine and therefore of the electrical rotating machine.

It should be underscored that use of the containment lung results in obtaining a multiplication of the pressure of the fluid which supplies the turbine, and therefore the transfer of a considerable quantity of energy without the use of mechanical parts which would create problems of wear and in any case involve heavy weights, bulk and high costs, including installation and maintenance.

According to one further embodiment, the motor unit, instead of being started through compression of a fluid, draws its motion from oscillating device2by means of a mechanical gear, for example a rack which in turn engages a toothed wheel, for example a pinion, connected to the electrical rotating machine.

At each complete stroke of oscillating device2, i.e. from start stroke to subsequent return, the rack associated with the said oscillating device moves with rectilinear alternated motion followed by alternated rotation of the pinion which in turn starts up the electrical rotating machine.

Advantageously, the electrical rotating machine in this case comprises an alternator.

Also advantageously, the motor unit comprising rack and pinion ensures continual functioning of the electrical rotating machine. In other words, the electrical rotating machine is set in rotation at every travel of oscillating device2, so it doesn't undergo periods of inactivity such as for example during the return phase of oscillating device2to the start stroke condition.

FIG. 3illustrates a device50according to the invention, in one preferred embodiment. In this figure the parts common to previously described embodiments are indicated with the same numerical references.

In device50the motor unit comprises a special hydraulic cylinder in the form of double section thrust cylinder52, illustrated in greater detail inFIGS. 6-8. Cylinder52comprises a sleeve54, a piston56and a rod58which, when the cylinder is in the configuration of intake of the working fluid, exits the cylinder sleeve completely. Lever4is operatively connected to the free extremity of rod58in such a way that the oscillatory motion of lever4brings about an axial shifting of rod and therefore of piston56. With view to obtaining high pressures of the working fluid within cylinder52, even with waves of limited force, since for reasons of structural toughness a small cylinder could not be employed, a large size two stages cylinder was designed, that is, having a piston56in two sections, one of thrust or movement and one of pumping, or force, with a reduced section.

In greater detail, piston56has a first thrust section60on which lever4acts by means of rod58, the section being substantially equal to that of the cylinder. On the opposite side, i.e. facing from the part opposite to rod58, the piston has a core62which extends substantially for the whole length of cylinder52and defines, with the internal surface of sleeve54, a very narrow annular cavity64for containment of the working fluid. In other words, annular cavity64is the containment lung of device50. So, the ring that defines this cavity constitutes the actual force section66, far smaller than thrust section60.

Therefore, thrust section60, due to its greater size, receives only modest pressure from the lever; its sole function is to acquire thrust and transmit it to force section66which is the actual pumping section.

The second stage of cylinder52, containing the working fluid, has a very small pumping section, so when it is subjected to the thrust produced by the first stage it gives the fluid a high pressure, equal to the pressure acting on the first stage of the cylinder multiplied by the ratio between the piston's two thrust sections.

Cavity64is in fluidic communication with the connection pipe to hydraulic motor5by means of outlet channel70and with the pipe from recovery tank7by means of fluid inlet channel72, said channels being created in the cylinder head opposite to the one crossed by rod58.

Thanks to the special hydraulic cylinder (pressure multiplier)52described above, it was found that in simulating a wave with a power of 8 kW, a period of 4 s and a height of 27 cm, the device is capable of delivering electrical power of around 3.5-4 kW, with a yield therefore equal to about 40%.

Machine yield can reach higher values (70-75%) with higher waves (54 cm)

According to one favoured embodiment, the device according to the invention can supply energy not only in the thrust phase of oscillating device2but also in the return phase of the said organ by exploiting the action of counterweight9. To this end, with reference toFIGS. 3-5, lever4acts alternatively on two opposite fluid containment lungs, in the examples illustrated advantageously comprising pressure multiplier cylinders52.

For example, in an advantageous embodiment, oscillating device4is operatively connected to the rods56of two pressure multipliers52, opposed in such a way as to act alternatively on the said pressure multipliers. In particular, when the device undergoes the thrust of a wave it acts in compression on the working fluid contained in one cylinder52and in intake of fluid into the opposite cylinder; when the device is in return phase, the two cylinders52work with one on intake and the opposite on compression.

Preferably each containment lung3of the working fluid is associated with its own turbine5and its own circuit of turbine supply and fluid recovery.

In order to act in compression on the working fluid also in the return phase of the oscillating device, the action of counterweight9on that organ must have a suitable intensity. To this end, with reference toFIG. 3, counterweight9is movable along a portion of substantially horizontal extremity4′ of lever4, opposite the profiled extremity8on which the waves act, in such a way as to be positioned as much as possible “overhanging” the lever4, in order to increase the arm of the lever.

In one embodiment, counterweight9is movable in function of wave power. In greater detail, if the waves have a limited power and therefore height, counterweight9is shifted from the farthest extremity in such a way as to carry out only the return action. In this case the device generates energy only in the thrust phase, and only one containment lung3works in fluid compression.

If however the waves are of appropriate power and height, for example greater than a certain pre-established threshold, counterweight9is shifted, for example automatically, towards the farthest extremity of lever4until it balances the two thrust and return movements and therefore the two pumping forces. In this case the second pressure multiplier is also activated.

According to one embodiment, shifting of the counterweight is commanded automatically by a control unit, for example when oscillating device4comes into contact with end of stroke arrests20,21.

FIGS. 4 and 5illustrate a device100according to the invention in a embodiment wherein oscillating device4has a prevalent horizontal extension, i.e. parallel to the sea. In this figure, the common or equivalent parts with regard to previously described embodiments are indicated with the same numerical references.

In this case, the extremity of oscillating device4on which the waves act carries a float108. Advantageously, float108is built with a special form that exploits racing yacht construction technology, giving it considerable floatability even under high weight stresses.

The oscillating device4oscillates around pin24and its oscillation is limited by lower and upper arrests120and121.

According to one favoured embodiment, the oscillating device4is operatively connected to rods56of two opposed pressure multiplier cylinders52, of the type described above, in such a way as to permit pumping of the working fluid in both the wave thrust phase—therefore in the rising phase of float108—and in the falling phase of the float. In this case the two special cylinders are set vertically. For example, the extremities of the two rods56are linked by transversal pin180which engages a slot182in the extremity of lever4opposite the float.

According to one favoured embodiment, a sliding guide190for mobile counterweight9extends along lever4. For example, this counterweight runs along guide190moved by worm screw192activated by a motor apparatus (not shown).

Advantageously, the motor apparatus is commanded by a control unit, for example when the oscillating device4comes into contact with end stroke arrests120,121.

It should be pointed out that in the absence of counterweight9, i.e. in the neutral phase, lever4is raised in function of wave force, but in the absence of the latter the lever is lowered by the force of its own weight alone. This force would be insufficient for compressing the working fluid in the descent phase. But by increasing lever weight more force could be obtained in this phase. However, the applied weight contrasts the rising phase, reducing wave height and therefore the stroke of the lever.

One aspect of the invention therefore regards adjustment of lever weight in function of various wave conditions, especially different wave strengths and heights. The technical solution adopted envisages positioning counterweight9in correspondence to the pin of the lever, i.e. in a non-influencing position in a situation of low wave force. In this case lever4pumps only on one cylinder52, the lower one. On increase of the waves in force and height, for example when contact is detected between the lever and the lower end stroke arrest, the counterweight is automatically commanded to shift towards the water, increasing lever weight, until it balances pumping forces and stroke in the two phases of rising and descent. In this way the upper cylinder is also activated and both movements of the lever are exploited even in the case of very high and powerful waves.

FIGS. 9 and 10show the device in a further, particularly advantageous embodiment, globally denoted by reference numeral200, essentially resulting from the vertical oscillating lever device4(with the scoop8) inFIGS. 1-3, with the horizontal oscillating lever device4′ (with the float108) inFIGS. 4 and 5. In said figures, the elements common to the aforesaid embodiments are indicated by the same reference numerals.

According to a general embodiment of the device200, the oscillating organ of said device comprises a lever extending essentially horizontally4′ carrying, towards the sea, a float108′, able to receive a vertical thrust from the waves. Behind the float, towards the fulcrum24of the horizontal lever4′ is another lever4″, extending essentially vertically, having a lower extremity8of a concave shape (like a scoop) able to receive the thrust of the sea waves acting essentially in a horizontal direction, said levers4′ and4″ being positioned so that when the thrust of the wave ceases in a vertical direction on the first lever4′ (with float108′) the thrust of the wave in a horizontal direction commences on the second lever4″ (with scoop8), and vice versa.

More in detail, the device200essentially has the same structure as the device100with a horizontal lever4′, with the main difference that to said lever4′, preferably towards the float108′, a lever4″ terminating in a concave extremity8, for example scoop-shaped, is hinged so as to freely oscillate. Such lever4″ with scoop8acts as a vertical oscillating lever able to receive the thrust of the wave acting in a horizontal direction, as described in relation to the devices1and50.

The oscillatory movement of the vertical oscillating lever4″ is transmitted to a motor unit, in the same way as described above.

Advantageously, for example, a hydraulic cylinder210is hinged at one extremity to the horizontal lever4′ and at the other to the vertical lever4″, preferably near the scoop8. This way the oscillation of the vertical lever4″ between an essentially vertical rest position and an end stroke position inclined backwards in relation to the oncoming waves causes the movement of the piston of said hydraulic cylinder210.

Before describing the functioning of this device200, it is worth remembering that as sea waves approach the coast they increase in height and decrease in length. The mass of water which they are composed of therefore acquires a considerable and powerful horizontal thrust. The device200is designed to fully exploit the energy produced by the waves, especially near the coast, in that by combining the action of the horizontal lever with float with the action of the vertical lever with scoop, it can exploit both movements of the wave, vertical and horizontal, effectively capturing all the available energy and transferring the energy acquired to the motor unit continuously, at constant power. In turn, the motor unit is therefore able to continuously run the electricity generator unit.

Starting from the situation illustrated inFIG. 11(a), in which the float108′ has just passed the belly of the wave and the scoop8skims the surface of the water, the wave reaches the float108′ and raises it the entire height of the wave, that is until it reaches the crest (FIG. 11(e)).

In this phase, the upward movement of the float108′ makes the horizontal lever4′ oscillate which, in turn, activates the pressure multiplier52. The oil pumped at high pressure by the pressure multiplier runs through the hydraulic circuit and powers the turbine5connected to the generator which thus produces electricity.

In this phase of the float108′ rising, the scoop8is also raised above the surface of the water and thus is irrelevant.

When the active thrust effect of the wave on the float108′ has ceased, the horizontal lever4′, following the float, descends following the course of the wave (FIGS. 11(f)-11(l)).

The descent phase of the horizontal lever4′ causes the insertion of the scoop8in the wave, keeping it immersed until the float begins to rise again.

Throughout this descent phase of the float108′, the scoop8, being at least partially immersed in the water, undergoes the thrust of the waves and is able to power the hydraulic cylinder210, which pumps oil under pressure to the motor unit.

It should be noted that inFIGS. 9-11, the float108′ is a spherical or semi-spherical shape so as not to obstruct the scoop when the two parts are adjacent.

According to one advantageous embodiment, the hydraulic cylinder210has the same pumping section and the same stroke as the pressure multiplier and the relative hydraulic circuit is connected to that of the pressure multiplier52joined to the horizontal lever4′, so as to share at least the turbine5and the collection tank7. This way, the oil pumped into the circuit by the hydraulic cylinder210has the same pressure and flow characteristics as the oil pumped by the pressure multiplier thus keeping the rotation of the generator and electric power produced, constant and continuous.

It is therefore possible, by fully balancing the active phases of the lever with float and the lever with scoop, to constantly and continuatively produce electric power.

It is worth noting that a pressure multiplier does not need to be joined to the vertical lever4″ in that said lever4″ has to sustain much less strain than the horizontal lever4′, so that a traditional cylinder structure is sufficient to withstand the strain it is subjected to.

Surprisingly, the combined device therefore makes it possible to capture practically all the kinetic energy of the waves along the coast transforming it into electricity, the only losses being those associated with the normal reduction in efficiency of any transformation cycle.

It is worth noting that, thanks to the possibility of exploiting the oscillation of the vertical lever4″ during the descent phase of the float108′, in the combined device200, use of the upper pressure multiplier52could be avoided52. It is possible however that in certain sea conditions, the float, so as to better exploit the power of the waves, may need a load to sink it into the wave itself. By adjusting the position of the mobile counter weight it is possible to apply the necessary load to the float. In this case it would be advantageous to exploit the load applied to the float in the descent phase of the said float too. Consequently in this event, the use of the two pressure multipliers52(lower and upper) would be useful.

It is worth noting that the mobile counter weight9may also be used by shifting it to the extremity opposite the float and/or scoop, to raise these parts so as to extract them from the waves and prevent the device from getting damaged in the case of fierce storms.

It is also worth noting that, in the case of use of the device in deep waters, for example on oil platforms, the two single implementation systems (vertical lever only or horizontal lever only) are in any case efficient.

In brief, the device for generating electricity from waves according to the invention comprises a lever4immersed in the waves, oriented in a substantially horizontal or vertical manner which, due to the effect of the waves, moves like a pendulum, acting as a pumping agent for the movement of the fluid contained in at least one hydraulic cylinder. The fluid, pumped by the oscillating lever, is forced into a hydraulic circuit and, through a pressure multiplier, is conveyed to a hydraulic motor that powers an electricity generator.

In practice, the force of the waves is translated directly into pressure on the working fluid; wave height and frequency act on the delivery of the fluid.

On this question it should be noted that through acting on lever ratio, i.e. on the ratio of the power arm (on which the wave acts) and the resistance arm (on which the fluid pressure multiplier or containment lung acts), the fluid compression force and the extent of lever movement can be varied in such a way as to achieve the correct compromise, for example in function of the environmental conditions in which the device is employed.

The technical solution regarding use of a mobile counterweight further means that the device can be adapted to wave conditions in such a way as to obtain maximum yield in all situations, even with waves as high as twice the stroke of the pressure multiplier.

Innovatively, this invention produces electricity by means of an oscillating device which, set moving by waves, transmits kinetic energy to a motor unit which in turn exploits the said kinetic energy to set in motion an electrical rotating machine hooked up, for example, to an alternator or a dynamo.

Again innovatively, the device uses turbines to produce electricity but avoids their contact with seawater.

Advantageously, the device in this invention allows the use of turbines constructed in materials that are non-resistant or only slightly resistant to marine corrosion, thus reducing costs.

Advantageously the device allows the use of ordinary turbines, in other words not special ones such as are used offshore or in coastal devices, exploiting waves for the compression of air.

Advantageously the device is to be installed on the coast, with simplified installation and maintenance interventions.

Advantageously the device produces energy from renewable sources, thus respecting the environment.

Advantageously the device can supply energy in isolated places.

Advantageously the device is of limited bulk so it can be used aboard vessels, on offshore rigs and anywhere else offering the possibility of exploiting wave energy.

Clearly, a skilled person, in order to meet contingent and specific needs, could make modifications to the device described above, yet without going beyond the scope of protection as defined in the following claims.