SCUOLA SUPERIORE SANTANNA

ELECTRICAL ENERGY GENERATION SYSTEM

The object of the present invention is an electrical energy generation system comprising at least one electrical energy generation device, which has fixing means for fixing to a support structure and first conversion means configured to convert the action of the wind acting on the electrical energy generation device into electrical energy through a triboelectric effect between the first means and the support structure.

The development of technology is leading to an increase in the use of electronic devices to carry out the most diverse activities.

This growing use of electronic devices causes a continuous demand for electrical energy and, for this reason, the search for new sources of electrical energy is becoming fundamentally important.

This aspect is particularly apparent in the field of agriculture and environmental monitoring, in which, for example, for the protection and monitoring of ecosystems, sensor devices are used to detect the conditions of the environment in which they are placed, sensors that require electrical energy for their operation.

There is therefore a need to create energy storage and generation systems that are ecologically sustainable, in order to power the sensors, but at the same time not damage the surrounding environment, possibly integrating into the environment in order to be able to stay there for long periods.

In the state of the art there are devices that exploit the action of the wind to create electrical energy, through a triboelectric effect.

Such systems are preferably provided in combination with plants, so that the rubbing of the devices on the leaves of the plants, rubbing caused by the action of the wind acting on the device itself, generates a concentration of electrical charge that can then be exploited as electrical energy.

Such known systems, however, are particularly affected by the climatic conditions of the surrounding environment, since, in the event of rain and a consequent increase in humidity, the triboelectric effect is less effective.

This aspect is particularly disadvantageous as it causes sudden and unexpected decreases in electrical current, which compromise the proper functioning of electronic devices that need to be powered.

There is therefore a need which is not satisfied by the state of the art to overcome the above-described disadvantages.

The present invention achieves the above objects by realizing a system as described above, wherein the electrical energy generation device comprises second conversion means, configured to convert the action of the raindrops falling on the electrical energy generation device into electrical energy through a triboelectric effect.

The system that is the object of the present invention, therefore, generates electrical energy by simultaneously exploiting both the action of the wind and the action of the rain, in such a way that, in case of rain, a continuous generation of electrical energy is guaranteed.

The system that is the object of the present invention, therefore, compensates for the inefficiency of systems based exclusively on the conversion of the force of the wind through a complementary energy source, which exploits the action of the raindrops that fall on the electrical energy generation device, again through the triboelectric effect.

Therefore, a further source of energy from the environment is used, which provides a significant contribution, since analyses conducted on the system that is the object of the present invention have demonstrated the possibility of powering a dozen LED devices for every single drop of rain that falls on the electrical energy generation device.

A further advantageous aspect of the system that is the object of the present invention is the generation of electrical energy without requiring conventional energy supply devices, such as cables, batteries, photovoltaic cells, which require greater complexity from an installation point of view, but which, above all, use materials that are not ecologically sustainable or ecologically integrable.

In addition, the first and second conversion means, in addition to the generation of electrical energy, can be exploited as sensors aimed at detecting the intensity of the wind and rain acting on the system that is the object of the present invention.

For this reason, the system that is the object of the present invention can provide detection means for detecting the amount of electrical energy generated, which detection means are configured so as to calculate the intensity of the wind and the amount of rain on the basis of the electrical energy generated.

In fact, sensors are made that can detect the amount of rain and the intensity of the wind, but indirectly.

In order to efficiently exploit and convert the mechanical energy of wind and rain, advantageously, the first conversion means and the second conversion means are arranged superimposed on each other, in such a way that the first conversion means are arranged below the second conversion means.

According to a preferred embodiment, the electrical energy generation device belonging to the system that is the object of the present invention is realized as a multi-layer device, i.e. consisting of a plurality of layers, superimposed on each other.

In particular, there are: a base layer of dielectric material capable of developing triboelectric charges following solid/solid contact, a first electrode made of electrically conductive material, a layer of plastic material, an upper layer of dielectric material capable of developing triboelectric charges upon liquid/solid contact, a second electrode made of metallic material.

From what has just been described, it is evident that the electrical energy generation device belonging to the system that is the object of the present invention exploits the triboelectric effect to convert the kinetic energy of wind and rain into electrical energy, in particular to exploit the kinetic energy of wind on the lower layer and the kinetic energy of rain on the upper layer of the device itself.

Furthermore, according to the configuration described above, the contributions of wind and rain can be exploited simultaneously or separately by the same electrical energy generation device.

The layers of electrically conductive material may be made of any of the materials known in the art, such as metals, conductive polymers, ionic conductors, carbon, ceramic conductors or the like.

As will be described below, the layer of plastic material is intended to regulate the mechanical characteristics of the entire electrical energy generation device, such as rigidity, weight and vibrational characteristics, i.e. the response to the action of the wind.

According to one possible embodiment, the base layer provides for the use of silicone elastomers, fluorinated polymers or the like.

Preferably, silicone elastomers are used, as they not only exhibit excellent electrification properties, but have surfaces capable of withstanding high impact forces during operation of the system, without damaging the support structure in contact with the base layer.

Advantageously, the second electrode does not entirely cover the upper layer of dielectric material, but is in the form of a leaf vein, consisting of a longitudinally extending main branch and a plurality of secondary branches extending outwards at the sides of the main branch.

Advantageously, the diameters of the branches of the second electrode have been optimized to obtain the best performance in rainy conditions.

This unique shape ensures that each drop that hits the electrical energy generation device comes into contact with the second electrode, to subsequently flow quickly along the surface dielectric layer, up to the edges of the device, where it falls because the accumulation of liquid would cause a decrease in performance. This feature is particularly relevant in combination with an embodiment variant of the system that is the object of the present invention which provides that the upper layer of dielectric material comprises inert material.

For example, material such as Teflon®, FEP (Fluorinated ethylene propylene), Polytetrafluoroethylene (PTFE) or the like can be provided with highly water-repellent characteristics.

The FEP layer, being hydrophobic, avoids excessive wetting of the device, i.e. of the underlying layers.

According to a further embodiment, it is possible to provide one or more intermediate layers between the base layer and the first electrode and/or between the first electrode and the upper layer, in order to vary the mechanical characteristics of the electrical energy generation device.

For example, it is possible to provide reinforcement layers, aimed at increasing the rigidity of the device and, consequently, to obtain the natural frequency necessary to optimize the collection of wind energy.

According to a possible embodiment, the system comprises a storage device for electrical energy, aimed at accumulating any electrical energy produced and not consumed.

Based on the above description, it is possible to see how the system that is the object of the present invention can be fixed to any support structure, such as for example buildings, roofs, windows or the like, without limiting its functionality.

According to a preferred embodiment, however, the support structure comprises at least one plant, the electrical energy generation device being positioned on a leaf of said plant, with the first conversion means in contact with the surface of said leaf.

As will be evident from the illustration of some exemplary embodiments, the electrical energy generation device is made in the form of an "artificial leaf", which can be installed on plants for the storage and generation of electrical energy using both wind and rain.

Due to its unique configuration, the electrical energy generation device not only does not damage the plant, but works synergistically with it, as part of the process of conversion into electrical energy taking part within the plant itself.

The system that is the object of the present invention therefore exploits the wind-rain-plant combination, which increases the application potential of the system itself, especially in the field of agriculture and environmental monitoring.

According to one embodiment variant, the fixing means consist of at least one housing seat for housing part of the plant.

As will be illustrated below, the unique fixing of the electrical energy generation device to the supporting plant also allows a distance of the device with respect to the leaf to be maintained that allows its performance to be improved and deleterious effects on the plant to be avoided.

The fixing to the plant, moreover, also allows a distance of the device itself from the leaf to be maintained, which allows its performance to be improved by allowing separation after contact, so that the charges generated during the contact between the leaf and the device can be separated and induced in the electrodes.

Subsequently, through the illustration of some exemplary embodiments, a specific form of such a housing seat will be described. However, it is already possible to identify how such a housing seat allows a mechanical fixing of the second electrode to be obtained, thus reducing the risk of detachment of the same from the upper dielectric layer, even in the case of high humidity levels that could deteriorate any bonding material present between the second electrode and the upper dielectric layer, which is the most exposed to the weather.

In fact, according to one possible embodiment, the second electrode is fixed to the upper dielectric layer by means of a transparent and flexible adhesive layer.

Compared with the prior art, this manufacturing process involves only a few steps, inexpensive materials and inexpensive equipment.

Advantageously, the electrical energy generation device is made of materials that do not damage the leaves of the plant used as a support and that are transparent to light, so as to allow photosynthesis of the same.

The system that is the object of the present invention is therefore optimized to be used in synergy with plants for long periods of time, without damaging the leaf or hindering photosynthesis, transpiration, etc.

Based on the description, the system that is the object of the present invention is suitable for operating outdoors and collecting energy from wind and rain.

The electrical energy generation device is thin (<1 mm maximum thickness), light (<3 g maximum weight), flexible and advantageously transparent.

The energy generation device is installed on the leaves of the plants to exploit the movement of the same in the wind, for the production of energy.

The multilayer structure uses a single electrode to harvest energy from both wind and raindrops.

The materials used are mainly inert and do not release toxic substances into the environment. These materials can even be completely biodegradable, so that the electrical energy generation device, after a certain period of time, breaks down together with the leaves of the plants.

Electrical signals from the plant tissue can be used to detect the plant's exposure to wind and its hydration.

Finally, the system that is the object of the present invention allows the use of the signals coming from the collection of energy from wind and rain for the assessment of weather conditions and to use them for the monitoring of the environment.

These and other features and advantages of the present invention will become clearer from the following disclosure of some embodiment examples illustrated in the accompanying drawings, wherein:

Figure 1 shows a schematic diagram of a possible embodiment of the electrical energy generation device belonging to the system that is the object of the present invention; Figures 2a and 2b show two views of a possible embodiment of the system that is the object of the present invention.

Figures 3a to 3c show a schematic diagram designed to illustrate the generation of electrical energy through the conversion of wind power;

Figures 4a to 4d show a schematic diagram designed to illustrate the generation of electrical energy through the conversion of falling raindrops.

It is specified that the figures attached to the present patent application show only some possible embodiments of the electrical energy generation system that is the object of the present invention, to better understand its described advantages and features.

These embodiments are therefore to be understood as purely illustrative and not limiting to the inventive concept of the present invention, namely that of realizing a system that allows both the energy of the wind and falling raindrops to be converted into electrical energy, using common materials, the assembly of which requires simple procedures to be performed, with limited costs.

The electrical energy generation system that is the object of the present invention comprises at least one electrical energy generation device 1 , which has fixing means for fixing to a support structure, first conversion means configured to convert the action of the wind acting on the electrical energy generation device into electrical energy through a triboelectric effect, and second conversion means configured to convert the action of the raindrops falling on the electrical energy generation device into electrical energy through a triboelectric effect.

As will be described later, the triboelectric effect generates a concentration of positive and negative charges, for the formation of a potential difference that is exploited by special circuits connected with the energy generation device 1 , for the generation of an electrical current.

With particular reference to Figure 1 , a possible embodiment of the device 1 is illustrated, consisting of a multilayer structure.

In particular, a base layer 11 of dielectric material is provided, capable of developing triboelectric charges upon solid/solid contact. The layer 11 consists of a silicone elastomer with a thickness between 100 and 500 pm.

A layer 12 comprising a first transparent electrode consisting of conductive ceramic material, in particular ITO (Indium Tin Oxide), is then deposited on the layer 11 .

The electrode 12 consists of a continuous layer of conductive material about 50 pm thick.

Above the layer 12 there is a layer 13 of PET (Polyethylene Terephthalate) material, of thickness comprised between 50 and 300 pm.

Above the PET layer 13 is provided a thin upper layer 15 of dielectric material.

The layer 15 consists of a film of FEP (fluorinated ethylene propylene) with a thickness of 10 to 150 pm.

The layer 15 is preferably applied onto the layer 13 through a layer 14 of adhesive material.

The last layer, layer 16, consists of a second electrode, preferably made of the same material as the layer 12, which is fixed to the layer 15.

It is clear how the layer 11 and the layer 12 can constitute the first conversion means, while the layers 12, 15 and 16 can constitute the second conversion means.

Unlike the electrode of the layer 12, the electrode of the layer 16 consists of a "discontinuous" layer, in the shape of a leaf vein.

Such a shape is clearly illustrated in Figure 2b, in which it is evident that the leaf vein consists of a main branch 160 extending longitudinally and a plurality of secondary branches 161 , 162 extending to the sides of the main branch 160 towards the outside of the device 1 .

Still with reference to Figures 1 to 2b, the device 1 takes the form of an "artificial leaf", which has an end part 10 having a housing seat 100 adapted to allow the fixing of the device 1 to a support structure.

Preferably, as illustrated in Figure 2a, the support structure consists of a plant, which has at least one leaf 2 on which the device 1 is rested. The terminal part 10 therefore has two housing seats 100 arranged opposite to each other with respect to the longitudinal axis of the device 1 , so that one or the other housing seat 100 can accommodate the pistil of the leaf 2, so as to fix the device 1 to the leaf 2, allowing a relative movement between the device 1 and the leaf 2, for example in case of wind acting on the plant.

As described above, the device 1 can be produced by a simple and inexpensive process.

In particular, the layers 11 (silicone elastomer), 12 (electrode of ITO conductive material) and 15 (FEP - fluorinated ethylene propylene) are cut according to the desired shape and size with a laser cutter or with scissors. One side of the layer 12 is coated with bonding material, and the silicone elastomer layer 11 is fixed thereon. At this point, another sheet of ITO electrically conductive material is cut for the generation of the layer 16, following a branched pattern and adapting to the shape and dimensions of the previously cut layers.

Small windows are then obtained near the edge of the layer 15 to provide a mechanical fixing of the layer 16.

The layer 15 and the layer 16 can then be glued to the layer 13, as previously described, in turn fixed, on the opposite side, to the layer 12.

Based on the characteristics described so far, it is possible to illustrate the operation of the system that is the object of the present invention, schematically shown in Figures 3a to 4c.

The operating principle underlying the system of the present invention is to use a shared electrode for the collection of charges generated by wind energy and rain, reducing the complexity and materials necessary to assemble the electrical energy generation device 1 , making it lightweight, in order to promote movement in the wind.

In particular, Figures 3a to 3c illustrate the conversion of wind power into electrical energy.

When the wind blows on the multilayer device 1 , fixed on a suitable surface such as the leaf 2 of the plant, the layer 11 vibrates and then comes into contact with the surface and is then triboelectrically charged, as shown in Figure 3a, in which the positive and negative charges of the different layers are shown.

The charges are then induced electrostatically in the electrode of the layer 12, after which the leaf and the device are separated, and can be collected, as illustrated in Figure 3b.

When the device 1 and the surface for contacting the leaf 2 come into contact again, the previously generated current is reversed, as illustrated by the arrows in Figure 3c.

As previously discussed, it is important to note that when the device 1 is installed on the leaf 2, the plant tissue may be connected as an additional electrode and triboelectric layer, so as to increase the power and obtain plant tissue measurements related to tissue hydration status and potential dehydration, so as to obtain signals for detection and monitoring of the plant conditions.

Figures 4a to 4d illustrate the conversion of kinetic energy resulting from falling raindrops into electrical energy.

As previously described, in fact, the system that is the object of the present invention allows collection and conversion of the energy of the raindrops on the upper part of the same device 1 using the same configuration of the electrode in addition to a further electrode placed on the upper part of the device 1 .

In particular, the same electrode, i.e. the layer 12, used for the collection of wind energy acts as an electrode of a capacitor for the collection of the energy from the raindrops falling on the device 1 .

Therefore, not only is the simultaneous collection of wind and rain energy obtained, but also the collection of energy deriving from wind and raindrops separately (when the phenomena occur individually) with the same multilayer structure.

The raindrops impacting the top of the device 1 charge the layer 15 through the triboelectric effect.

The charges on the layer 15 are in electrostatic equilibrium with the charges induced in the electrode of the layer 12, as illustrated in Figure 4a. When the raindrop 4 lands on the upper dielectric layer 15, the drop follows two main mechanisms:

1 ) undergoes charge separation following interaction with charges on the layer 15, Figure 4b,

2) due to its kinetic energy, the raindrop spreads on the surface of the layer 15 and contacts the branched electrode 16, establishing a second electrode of the capacitor with variable surface area depending on the spread of the droplets, Figure 4c.

Together with the electrode of the layer 12 and the dielectric of the layer 15, the electrode of the layer 16 forms a charged capacitor whose charge (i.e. current I in Figures 4a to 4d) depends on the impact of the droplet, the triboelectric surface charges created on the layer 15 and the capacitor formed between the droplet, the layer 16 and the layer 12.

When the droplet shrinks and leaves the surface, the current induced from one electrode to the other due to the contact of the droplet is reversed, see Figure 4d.

Again, as with Figures 3a to 3c, the opportunity to couple the plant tissue as an additional electrode is a feature that can be used to increase the energy output when the device is installed on a plant leaf.

The plant tissue and the dielectric layer 11 then form a second halfelectrode of a triboelectric generator for solid-solid contact electrification, which approximately doubles the charges that can be collected.

Finally, it is specified that the potential difference created by the charges on the various layers is used for the generation of electrical current through special circuits, not illustrated in the figures, which can be made according to any of the methods known to the state of the art.

In fact, the three electrodes (layer 12, layer 16 and plant tissue) can be connected by standard circuits using rectifier diodes to translate the alternating current signal into direct current and to charge a capacitor, or directly to power consumers, such as LEDs, sensors, or the like.

Finally, as anticipated, the electrical signals generated by the wind or rain can be used as indirect sensors to measure the intensity of the wind and the amount of rain acting on the device, information that is particularly useful for environmental monitoring.

While the invention is subject to various modifications and alternative constructions, some preferred embodiments have been shown in the drawings and described in detail.

It should be understood, however, that there is no intention to limit the invention to the specific illustrated embodiment but, on the contrary, the aim is to cover all the modifications, alternative constructions and equivalents falling within the scope of the invention as defined in the claims.

The use of “for example”, “etc.”, “or” refers to non-exclusive nonlimiting alternatives, unless otherwise stated.

The use of “includes” means “includes but is not limited to”, unless otherwise stated. The project from which the present patent application derives has received funding from the European Union's Horizon 2020 research and innovation program, Grant agreement No. 824074.