WO2018138606A1

WO2018138606A1 - Convective motions thermoelectric converter

Info

Publication number: WO2018138606A1
Application number: PCT/IB2018/050315
Authority: WO
Inventors: Luigi Sanna
Original assignee: Luigi Sanna
Priority date: 2017-01-27
Filing date: 2018-01-18
Publication date: 2018-08-02
Also published as: EP3574210B1; IT201700008792A1; EP3574210A1

Abstract

The convective motions thermoelectric converter (1) comprises a tubular conduit (101) having a substantially circular section, looped back on itself to form a circuit comprising four segments (2, 3, 4, 5), of which two vertical segments (3, 5) which are substantially vertical and have substantially equal height, and two horizontal segments (2, 4), of which an upper horizontal segment (2) and a lower horizontal segment (4) which are substantially horizontal, containing a fluid (31, 32) inside comprising at least one of a gas (32) and a liquid (31) and a gas-liquid mixture, the fluid (31, 32) being heated in one of the vertical segments (3, 5) and cooled in the other of the vertical segments (3, 5) in order to create, between the fluid contained in a vertical segment and the fluid contained in the other vertical segment, a difference in temperature generating, in the fluid (31, 32) contained in the tubular conduit (101), convective motions usable for the production of electricity, the flow of the convective motions being intercepted by one or more turbines (14) connected to one or more alternators or dynamo.

Description

CONVECTIVE MOTIONS THERMOELECTRIC CONVERTER

Technical Field

The present invention relates to a convective motions thermoelectric converter which is able to produce electricity by exploiting the difference in temperature between two fluids.

Background Art

At the present state of the art, it can be determined that few inventions exist able to convert into electricity reduced temperature differences between two fluids in the range of 20°-30°C, and among these is OTEC technology.

OTEC technology, which is the acronym of Ocean Thermal Energy Conversion, also known as thalasso thermal energy, appeared at the end of the 19th century but many technological developments only occurred after the great energy crisis of the early- 1970s.

This technology allows the conversion of heat into mechanical energy (intended to be used to produce electricity) starting from two thermal sources, among which, for this technology, a temperature difference of about 20°C is required. The thermal sources with such characteristics usually utilized consist of the water of the tropical ocean, located approximately between a latitude of 15° north and 15° south: more precisely, the hot water of the surface layer is used, at a depth of about 100 meters, which can reach 29°C, and the cold water at a depth of about 1000 meters, which can even reach 5°C.

The conversion of heat into electricity is carried out using either an intermediate fluid or seawater directly.

In the first case, a liquid with low boiling point (such as ammonia, freon and other organic fluids) is made to pass into the evaporator in gaseous state and is put into contact, through heat exchangers, with the hot water (25°-30°C) of the oceanic surface: it expands by creating an increase in pressure which enables a turbine, coupled with an alternator, to rotate and produce electricity, then returns to the liquid phase in the condenser, where it is put into contact, through other heat exchangers, with cold water (5°-6°C) pumped from the sea depths and, by means of a circulation pump, is sent back to the evaporator. In the second case, the hot water on the surface evaporates in a vacuum chamber producing steam, at low pressure and high volume, which subsequently causes the movement of a large turbine, which is coupled to an alternator, and then returns to the liquid phase in the condenser, where it is put into contact, by means of heat exchangers, with the cold water pumped from the sea depths. A hybrid OTEC also exists in which the water is first evaporated, as in the second mentioned case, and then steam is used to evaporate the liquid at a low boiling point, as in the first mentioned case.

The efficiency of this technology is very low, currently between 2% and 6%, and can achieve a maximum theoretical efficiency of 7%, but nevertheless, the fact that this energy source is inexhaustible makes this technology very promising, so it is subject to huge economic investments worldwide.

However, numerous problems exist which hinder the spread of this technology.

First of all, the fact that the environmental conditions under which it operates are found only in the tropics limits the spread of OTEC technology to this geographical area.

Then there is the problem of the size of the plant because large machinery and a considerable mass of fluid for heat exchange are needed inasmuch as:

- the turbines operate at low pressures and to achieve a suitable power level, they must have large dimensions, from 4 m in diameter to 50 m and more;

- less than 0.5 per cent of the incoming warm seawater is evaporated, so to obtain enough steam to operate a large turbine at low pressure, large quantities of water - many tonnes per second - have to be pumped;

- the pipes must be huge, both in terms of length, inasmuch as at least one must reach almost 1000 meters, and width, which can be even more than two meters.

There are also other problems, for example achieving very low pressures to facilitate the boiling of the water at temperatures of 25-30°C involves considerable technical difficulties and, moreover, involves the development from the water of dissolved gases such as oxygen and nitrogen, which are not condensable and which must be continuously removed.

Furthermore, when working at low pressures, the system must be tightly sealed to prevent excessive pressure losses.

Seawater algae sucked up by the pipes can block the heat exchangers and reduce the life span of the materials, which also undergo great stress from the salt water and are subject to possible corrosion: in other words, rapid degradation can occur of heat exchanger performance.

Suitable liquids for use as motor fluids such as ammonia, ethane, propane and butane are flammable and others, such as fluorocarbons, are harmful to the ozone in the atmosphere.

In the final analysis, since plant and operating costs are very high, in order to obtain electricity at a competitive cost, large-size plants have to be built, therefore with very heavy initial investments.

Nor should we underestimate storms out in the ocean, which could damage the platforms and seriously affect their functioning.

Description of the Invention

The main aim of the present invention is to provide a convective motions thermoelectric converter which allows facilitating the production of energy from the difference in temperature of one or more fluids.

Another object of the present invention is to provide a convective motions thermoelectric converter which allows overcoming the aforementioned drawbacks of the prior art within the scope of a simple, rational, easy, efficient to use and cost-effective solution.

The aforementioned objects are achieved by the present convective motions thermoelectric converter having the characteristics of claim 1.

Brief Description of the Drawings

Other characteristics and advantages of the present invention will become more evident from the descriptions of the following preferred, but not exclusive embodiments of a convective motions thermoelectric converter, illustrated by way of an indicative, but non-limiting example, in the attached drawings in which: Figure 1 shows a schematic view of the general operation of the converter according to the invention;

Figure 2 shows a schematic view of some shape variants of the converter according to the invention;

Figure 3 shows a schematic view of the converter according to the invention, in which an external heat storage tank is shown;

Figure 4 shows a schematic view of the converter according to the invention in which there is a sequential arrangement, one after the other, outside the converter, of heat exchangers of heat pumps;

Figure 5 shows a schematic view of the converter according to the invention in which a pipe connects the apex of a vertical segment with the apex of the other vertical segment and allows only the flow of gas;

Figure 6 shows a schematic view of the converter according to the invention, in which there is a sequential arrangement, one after the other, of heat exchangers of heat pumps outside the converter and the presence of a pipe connecting the apices of two vertical segments and allows only the flow of gas.

Embodiments of the Invention

With particular reference to these illustrations, reference numeral 1 globally indicates a convective motions thermoelectric converter.

According to the invention, the convective motions thermoelectric converter 1 comprises a tubular conduit 101 having a substantially circular section.

Solutions which provide for equivalent sections and similar to the circular section, e.g. ovoid, cannot be ruled out.

The tubular conduit 101 is looped back on itself and forms a circuit comprising four segments 2, 3, 4, 5, of which two vertical segments 3, 5 and two horizontal segments 2, 4 of which an upper horizontal segment 2 and a lower horizontal segment 4.

The vertical segments 3, 5 are substantially vertical and have substantially equal height.

The horizontal segments 2, 4 are substantially horizontal, but solutions cannot be ruled out which provide for curved segments, although they are substantially horizontal.

Usefully, the segments 2, 3, 4, 5 comprise sections of different diameter from segment to segment.

This way, the converter 1 has segments or portions of segments with sections of different diameter from segment to segment.

In particular, the upper horizontal segment 2 comprises a section with a smaller diameter than the sections of the remaining segments 3, 4, 5.

The smaller diameter section, therefore, is located in the upper horizontal segment 2.

The tubular conduit 101 contains a fluid 31, 32 inside.

The fluid 31, 32 comprises at least one of a gas 32, a liquid 31 and a gas-liquid mixture.

The fluid 31, 32 is heated in one of the vertical segments 3, 5 and cooled in the other of the vertical segments 3, 5 in order to create, between the fluid contained in a vertical segment and the fluid contained in the other vertical segment, a difference in temperature generating, in the fluid 31, 32 contained in the tubular conduit 101, convective motions usable for the production of electricity.

The flow of convective motions is in fact intercepted by one or more turbines 14 connected to one or more alternators or dynamos.

Advantageously, the converter comprises heat exchange means 15, 16, 19, adapted to carry heat from the fluid 31, 32 contained in the upper ending part of one of the vertical segments 3, 5, which is cooled, to the fluid 31, 32 contained in the lower ending part of the other of the vertical segments 3, 5, which is heated.

There is therefore heat transport by the fluid 31, 32 contained in the tubular conduit 101 by passing from one segment to the other.

In particular, the heat exchange means 15, 16, 19 comprise at least one heat pump 15 adapted to subtract heat from the fluid 31, 32 contained in the upper ending part of one of the vertical segments 3, 5 for the recovery of heat and heat exchangers 16, 19.

The use of other devices together or as an alternative to the heat pump, e.g. heat exchangers of various types, cannot be ruled out.

Usefully, with a heat pump or other methods, heat is removed from the fluid contained in the upper ending part of the vertical segment 3 and this heat is transferred to the fluid contained in the lower ending part of the vertical segment 5, e.g. of another convective motions thermoelectric converter.

The fluid 31, 32 used in the tubular conduit 101 can be of different types.

In a first case, the fluid 31, 32 comprises a liquid 31 which in turn comprises salts able to increase the weight and density of the liquid 31 itself.

By way of example, the liquid 31 may be of the type of distilled water, and the salts of the type of sodium chloride, or other substances, which dissolve in the liquid and make it denser and heavier.

In a second case, the fluid 31, 32 contained in the tubular conduit 101 of the converter comprises a liquid 31 having a boiling point which is intermediate between the temperature reached in one of the vertical segments 3, 5 in which the fluid is hotter and the temperature reached in the other one of the vertical segments 3, 5 in which the fluid is colder.

In a third case, the fluid 31, 32 comprises a liquid 31 and at least one or more gases 32 subjected to high pressure by their addition to the liquid itself to form a gas-liquid mixture. By way of example, the liquid 31 is of the distilled water type, and the gases 32 are of the air or nitrogen or carbon dioxide or other gas type. The gases 32 are added to the liquid 31 by subjecting the gases themselves to high pressure, with a compressor or other devices, so that these gases are made soluble, mixed or dissolved in the liquid 31.

By so doing, the tubular conduit 101 of the converter contains a gas-liquid mixture 31, 32 in which the gas 32 has high pressure.

Advantageously, the converter 1 comprises a pipe 13 which connects the apex of one of the vertical segments 3, 5 to the apex of the other of the vertical segments 3, 5.

The pipe 13 passes over the upper horizontal segment 2, does not contain the gas-liquid mixture, but only contains the gas 32.

In fact, at its ending parts it has a semi-permeable membrane, for simplicity not shown in the figures, which separates the gas 32 present in the pipe 13 from the gas-liquid mixture 31, 32 which is present in the vertical segments 3, 5.

The pipe 13 is adapted to carry gas from the gas-liquid mixture 31, 32, which is at the higher temperature and is present in one of the vertical segments 3, 5, to the gas-liquid mixture 31, 32 which is at the lower temperature and is present in the other of said vertical segments 3, 5.

Usefully, the pipe 13 is equipped with a pump, for simplicity not shown in the illustrations, having a compressor adapted to push and compress the gas 32 so as to create a vacuum on the surface of the gas-liquid mixture 31, 32 at higher temperature and an overpressure on the surface of the gas-liquid mixture 31, 32 at lower temperature.

Usefully, the converter 1 comprises second heat exchange means 20, 21, 24, 41 associated with the first heat exchange means 15, 16, 19 comprising:

- at least one heat pump 20;

- a heat exchanger 21 associated with one of the vertical segments 3, 5;

- a heat exchanger 24 immersed in an external fluid 23; and

- a fan 41 adapted to direct a flow of said external fluid 23.

The heat exchanger 19 is immersed in the external fluid 23, with the heat exchanger 24 and the heat exchanger 19 which are placed in sequence to intercept the flow for heat exchange between the external fluid 23 and the fluid 31, 32.

If we use heat pumps, if in the external fluid 23 we place in sequence, one after the other, the two external heat exchangers 19, 24, and if, with the fan 41 or other methods, we generate a flow of external fluid 23 in such a way that this fluid outside the converter passes through the heat exchanger 19 and then passes through the other heat exchanger 24, then we have a heat exchange between the external fluid 23 and the fluid 31, 32 inside the converter in this way: first of all, when the external fluid 23 passes through the heat exchanger 19, the external fluid 23 is cooled, because a heat pump conveys the heat of the external fluid 23 to the lower ending part of the vertical segment 5 of the converter 1, where it heats the fluid 31, 32 (liquid) which is located inside the converter, and subsequently, when the external fluid 23 passes through the heat exchanger 24, the external fluid 23 is heated, because another heat pump conveys the heat from the upper ending part of the other vertical segment 3 of the converter, where the fluid 31, 32 cools inside the converter, towards the external fluid 23 and which has been cooled by the heat exchanger 19.

Some embodiments of the converter 1 are described here below in detail.

The converter 1 is composed of a tubular conduit looped back on itself to form a circuit, with circular section or section equivalent to circular, consisting of four segments, i.e. the upper horizontal segment 2, a vertical segment 3, the lower horizontal segment 4 and the other vertical segment 5, containing inside it a fluid, which may be either a gas 32 or a liquid 31 or a gas-liquid mixture.

At the lower ending part 6 of a vertical segment 5, we identify the sector (Fig. 4, 5 and 6) of the circuit in which the fluid receives heat and is therefore heated. At the upper ending part 10 of the other vertical segment 3, we identify the sector (Fig. 4, 5 and 6) of the circuit in which the fluid transfers heat and is therefore cooled.

If the fluid contained inside the converter 1 (Fig. 1, 2 and 3) is heated at the lower ending part 6 of a vertical segment 5 and is cooled at the upper ending part 10 of the other vertical segment 3 after a certain time interval all the fluid contained in a vertical segment 5 will have higher temperature and therefore lower density and thus lower weight than the weight of the fluid contained in the other vertical segment 3 while all the fluid contained in a vertical segment 3 will have lower temperature and therefore higher density thus greater weight than the weight of the fluid contained in the other vertical segment 5.

Then the fluid contained inside the converter 1 does not remain still but in the vertical segment 5 in which it is at higher temperature it moves upwards, in the upper horizontal segment 2 it moves from the upper ending part of the vertical segment 5 in which it is at higher temperature to the upper ending part of the other vertical segment 3 in which it is at lower temperature, in the vertical segment 3 in which it is at lower temperature it moves downwards and finally in the lower horizontal segment 4 it moves from the lower ending part of the other vertical segment 3 in which it is at lower temperature to the lower ending part of the other vertical segment 5 in which it is at higher temperature.

These convective motions, i.e. the fluid current, persist as long as we heat the fluid at the lower ending part 6 of a vertical segment 5 and cool the fluid at the upper ending part 10 of the other vertical segment 3 and the fluid present in a vertical segment 5 remains hotter, and therefore lighter, than the fluid in the other vertical segment 3: if we interrupt heating at the lower ending part 6 of a vertical segment 5 and cooling at the upper ending part 10 of the other vertical segment 3 the temperature difference between the fluids contained in the vertical segments 3 and 5 gradually decreases, the fluid slows down and then, when the temperature is the same again at all points of the fluid present inside the converter 1, it stops.

The greater the temperature difference between the fluids contained in the two vertical segments 3 and 5, the greater the difference in density and therefore in weight between these fluids: consequently, the higher the speed will be of the fluid inside the converter 1.

If one or more turbines 14 are placed in any one point inside the circuit of the converter 1 , which intercept the flow of the convective motions of the fluid and each turbine 14 is connected to a device, such as a dynamo or an alternator, which converts mechanical work into electricity, it is possible to produce electricity in a quantity proportional to the speed reached by the fluid inside the converter 1.

The walls of the converter 1 must be made of thermally insulating materials in order not to conduct the heat of the fluid contained inside to the outside.

The heating or the cooling of the fluid contained inside the convective motions thermoelectric converter 1 can be obtained in various ways.

One solution is to have pipes, where cold water or other cold fluids flow, pass in the upper ending part 10 of a vertical segment 3, and have pipes, where hot water or other hot fluids flow, pass in the lower ending part 6 of the other vertical segment 5.

Another solution still is to use heat pumps. In this last solution (fig. 5) a heat pump 15 heats the fluid of the converter 1 at the lower ending part 6 of a vertical segment 5, in which the internal heat exchanger 16 of the heat pump 15 is immersed, displacing the heat coming from a liquid or gaseous fluid 18, external to the converter 1, to the lower ending part 6 of a vertical segment 5: the external fluid 18 is at higher temperature than that of the fluid contained in the lower ending part 6 of the vertical segment 5 and the external heat exchanger 19 of the heat pump 15 is immersed in the external fluid 18.

At the same time (Fig. 5) another heat pump 20 cools the fluid of the converter 1 at the upper ending part 10 of the other vertical segment 3, in which the internal heat exchanger 21 of the heat pump 20 is immersed, displacing the heat from the upper ending part 10 of the vertical segment 3 to a liquid or gaseous fluid 23, external to the converter 1: the external fluid 23 is at a temperature below that of the fluid contained in the upper ending part 10 of the vertical segment 3 and in the external fluid 23 is immersed the external heat exchanger 24 of the heat pump 20.

Among the shape variants to the circuit of the converter 1 there may be: the upper horizontal segment 2 may be not completely horizontal but inclined (Fig. 2), may be not rectilinear but curved (Figure 2), the vertical segments 3 and 5 may be of different heights (Fig. 2), the connection between the upper horizontal segment 2 and the vertical segments 3 and 5 may be vertical (Fig. 3) or horizontal (Fig. 4).

Among the variants to the basic operating diagram of the converter 1 there is that (Fig. 1) the speed of the fluid contained inside the converter 1 can be modified by the presence of segments or portions of segment of the circuit of the converter 1 having sections of different diameter.

In fact, since the flow rate of the fluid is constant in each section of the circuit of the converter 1, the speed of the fluid contained inside it will be higher in those sections of the circuit which have a smaller diameter, while the speed of the fluid will be lower in those sections of the circuit which have a larger diameter: in the smaller diameter section, the turbine 14 will be preferably located which, connected to an alternator or a dynamo, will produce electricity. In the event of the fluid contained in the converter 1 being a liquid 31, if the diameter of the section of the upper horizontal segment 2 is the smallest of the diameters of all the segments, in the upper horizontal segment 2 we can obtain a speed of the liquid 31 little affected by the limit represented by the force of gravity.

It is specified that the section of the upper horizontal segment 2 may have uniform section (Fig. 1 and 3) or may have further narrowing in its path (Fig. 4, 5 and 6).

The speed of the liquid 31 contained in the upper horizontal segment 2 in fact depends on the flow rate which the liquid has in the sections of the other three segments and this speed (fig. 1 and 3) is proportionate to the product of the speed of the fluid in the lower horizontal segment 4 multiplied by the ratio between the surface of the section of the lower horizontal segment 4 and the surface of the section of the upper horizontal segment 2 (or the surface of the portion of the upper horizontal segment 2 with smallest diameter if the upper horizontal segment 2 has portions with different diameters, Fig. 4, 5 and 6). Among the variants to the basic operating diagram of the converter 1 there is the possibility (Fig. 1 and 2) to increase the temperature difference between the fluid contained in a vertical segment 3 and the fluid contained in the other vertical segment 5 displacing part of the heat by means of a heat pump 27 from the fluid contained in the upper ending part 10 of a vertical segment 3, which is cooled by the internal heat exchanger 28, to the fluid contained in the lower ending part 6 of the other vertical segment 5, which is heated by the other internal heat exchanger 29.

Among the variants to the basic operating diagram of the converter 1, since by cooling the fluid at the upper ending part 10 of a vertical segment 3 heat is displaced from the inside to the outside of the converter 1 and therefore it is dispersed in the external environment, there is the possibility (Fig. 2), instead of dispersing this heat in the external environment, to introduce it into another converter 1 by means of a heat pump 30 and its internal heat exchangers 22 and 17, which transfers heat from the upper ending part 10 of a vertical segment 3 of a converter 1 to the lower ending part 6 of a vertical segment 5 of another converter 1 and then optionally the heat extracted from the upper ending part 10 of a vertical segment 3 of the second converter 1 can be introduced into the lower ending part 6 of a vertical segment 5 of a third converter 1 and so on: a large number of secondary converters 1 can be added as long as the temperature of the internal fluid of the lower ending part 6 of a vertical segment 5 of the first converter 1 is higher than that of the internal fluid of the upper ending part 10 of a vertical segment 3 of the last converter 1.

Among the variants to the basic operating diagram of the converter 1 there is the possibility that if the fluid contained inside the converter 1 consists of a liquid 31 it is possible to increase the difference in weight between the columns of liquid 31 which is contained in the two vertical segments 3 and 5 by adding to the liquid 31 salts, such as e.g. sodium chloride or potassium chloride, or other substances which, by dissolving in the liquid 31, give such liquid 31 higher density and therefore make it heavier.

Among the variants to the basic operating diagram of the converter 1 there is that (Figures 1 and 5) if the fluid contained inside the converter 1 consists of a mixture of liquid 31 and gas 32, a mixed liquid-gas fluid is obtained which behaves differently than what happens if the fluid consists only of gas 32 or only of liquid 31.

After the converter 1 has been filled with liquid 31, for example, but not exclusively, with distilled water, gas 32 is introduced at high-pressure into the liquid 31, for example, but not exclusively, air or nitrogen or carbon dioxide. The gas 32 can be injected at high pressure with a needle connected to a compressor, through the valve 33, which prevents the return flow of the gas 32 and of the liquid 31, or tablets can be introduced into the converter 1 which, by dissolving in the liquid 31, release the gas 32.

The gas 32 under pressure, since there is no more free space, is forced to mix or dissolve in the liquid 31 forming a gas-liquid mixture and when there are variations in temperature the liquid 31 and the gas 32 behave differently. When the gas-liquid mixture is heated in a vertical segment 5, both the liquid 31 and the gas 32, subjected to heating, will increase the movement of their molecules and thus increase their volume but the increase in volume of the gas 32 will be greater than the increase in volume of the liquid 31.

At microscopic level, the gas 32, dilating to a greater extent than the expansion of the liquid 31, also occupies part of the space that would have been occupied by the liquid 31 and therefore, per unit of volume in proportion, there is more gas 32 and less liquid 31 so, with the same temperature increase, the decrease in density of the gas-liquid mixture is greater than the decrease in density that would have occurred if there had only been liquid 31 in the converter 1.

When the gas-liquid mixture is cooled in the other vertical segment 3 the opposite phenomenon will occur: both the liquid 31 and the gas 32, subjected to cooling, will decrease the movement of their molecules and therefore will decrease their volume, but the decrease in volume of gas 32 will be greater than the decrease in volume of liquid 31.

At a microscopic level, the gas 32, contracting to a greater extent than the liquid 31 does, allows the liquid 31 to also occupy part of the space that would have been occupied by the gas 32 and therefore per unit of volume proportionally there is less gas 32 and more liquid 31 so that, the decrease in temperature being equal, the increase in density of the gas-liquid mixture is greater than the increase in density that would occur if in the converter 1 there was only liquid 31.

The advantage of using the gas-liquid mixture is that, when the difference in temperature between the gas-liquid mixture contained in the two vertical segments 3 and 5 is equal, differences in density and therefore in weight will be obtained which are greater than what would happen if, in the converter 1, instead of the gas-liquid mixture, there were only the liquid 31 or only the gas 32.

Among the variants to the basic operating diagram of the thermoelectric converter 1 is that if the fluid contained inside the thermoelectric converter 1 consists of a liquid 31 or a mixture of liquid 31 and gas 32 it is possible to further increase the difference in weight between the columns of fluid contained in the two vertical segments 3 and 5 by adding substances to such fluid, for example, but not exclusively, ammonia, which have a boiling point comprised between the temperature that the fluid achieves in a vertical segment 3 wherein the fluid, which is colder, drops, and wherein such substances are in liquid state, and the temperature which the fluid achieves in the other vertical segment 5 wherein the fluid, which is hotter, rises, and wherein such substances are in the gaseous state.

Among the variants to the basic operating diagram of the converter 1 there is that (Figures 1, 5 and 6) in the case of the fluid contained inside the thermoelectric converter 1 consisting of a gas-liquid mixture at high pressure, it is possible to introduce the presence of a pipe 13 which connects the apex of a vertical segment 3 with the apex of the other vertical segment 5, passes at a higher level, i.e. above, compared to the horizontal upper segment 2, does not contain a gas-liquid mixture but contains only gas 32 and conveys to the surface of the gas-liquid mixture at lower temperature present in a vertical segment 3 the gas which evaporates from the surface of the gas-liquid mixture at higher temperature present in the other vertical segment 5.

The start and end of this pipe 13 as well as the upper ending part (Figures 5 and 6) of the column of gas-liquid mixture contained in the two vertical segments 3 and 5 can be closed by a semi-permeable membrane 11 which allows the flow of the gas 32 only and not of the liquid 31 so as to prevent the liquid 31 from entering the pipe 13 placed above the upper horizontal segment 2 and in which only gas is meant to flow.

The pipe 13 connecting (Figures 5 and 6) the apex of the two vertical segments 3 and 5 may be provided, at any point in its path, with a pump 12 provided with a compressor which pushes the gas from the apex of the vertical segment 5 which contains the gas-liquid mixture at higher temperature to the apex of the vertical segment 3 which contains the gas-liquid mixture at lower temperature. This pump 12 with compressor (Figures 5 and 6) allows reducing the pressure of the gas 32 on the surface of the gas-liquid mixture at higher temperature present in a vertical segment 5, thus facilitating the outflow of the gas 32 from the gas-liquid mixture at higher temperature, and simultaneously allows increasing the pressure of the gas 32 on the surface of the gas-liquid mixture at lower temperature present in the other vertical segment 3, thus facilitating the solubility of the gas 32 in the gas-liquid mixture at lower temperature.

To facilitate (Fig. 5) the solubility of the gas 32 in the gas-liquid mixture at lower temperature present in a vertical segment 3, the gas 32 can be cooled with a heat pump 9, which cools the gas 32 with the internal heat exchanger 8 immersed in the gas 32 and conveys the heat from the gas 32 to the external fluid 23 by means of the external heat exchanger 7.

Among the variants to the basic operating diagram of the converter 1 (fig. 4 and 6) there is the possibility of exploiting the cooling of the fluid 18 outside the converter 1 produced by a heat pump 15 through its external heat exchanger 19 by placing the two external heat exchangers 19 and 24 of the converter 1 in sequence inside a closed container on the four lateral sides and having them crossed by the flow of external fluid 18 which, pushed by the fan 41 or other means, first crosses an external heat exchanger 19 and then the other external heat exchanger 24.

In fact, this arrangement allows a heat pump 20, by means of its internal heat exchangers 21, which is immersed in the fluid of the upper ending part 10 of a vertical segment of the converter 1, and external heat exchanger 24, which is immersed in the external fluid 23 (which in this case is made up of the external fluid 18 which has been cooled), to cool the fluid of the upper ending part 10 of a vertical segment 3 by exploiting the cooling of the fluid 18 outside the converter 1 implemented by another heat pump 15, by means of its internal heat exchanger 16 and external heat exchanger 19 which are inside and outside respectively the converter 1, which heat pump 15 has displaced heat from the fluid 18 outside the converter 1 to the internal fluid of the lower ending part 6 of the other vertical segment 5 of the converter 1 , sector in which the internal fluid is heated.

This arrangement in sequence (Fig. 6) can also be used to cool, by means of the internal heat exchanger 8 of a heat pump 9, the gas 32 present at the end of the pipe 13 which connects the apex of the two vertical segments: the external heat exchanger 7 of this heat pump 9 is placed after the external heat exchanger 19 of the heat pump 15 which cools the fluid 18 outside the converter 1.

It has in practice been found that the described invention achieves the intended objects.

Among the advantages of the converter 1 is the possibility (Fig. 3) of preserving heat not to be immediately converted into electricity using an external insulated tank 34 filled with water or with other substances with great thermal capacity with which to periodically exchange heat.

The use of one or more of these tanks 34 allows, for example, exploiting the differences in temperature between day and night to produce electricity.

In the latter case (Fig. 3) during the day two heat pumps are in operation, namely the heat pump 15, which heats the fluid of the lower ending part 6 of a vertical segment 5 by displacing heat from the external fluid 18, where its external heat exchanger 19 is immersed, to the lower ending part 6 of a vertical segment 5, where its internal heat exchanger 16 is immersed, and the heat pump 35 which cools the fluid of the upper ending part 10 of the other vertical segment 3, where its internal heat exchanger 36 is immersed, displacing heat from the upper ending part 10 of this vertical segment 3 to the heat exchanger 37 immersed in the fluid contained inside the tank 34: when the temperature of the fluid contained in the tank 34 and the temperature of the fluid 18 outside the converter 1 become the same, the two heat pumps 15 and 35 switch off.

During the night other two heat pumps are in operation, namely the heat pump 38, which heats the fluid of the lower ending part 6 of a vertical segment 5 of the converter 1 , where its internal heat exchanger 40 is immersed, by displacing heat from the heat exchanger 39, immersed in the fluid contained inside the tank 34, to the lower ending part 6 of a vertical segment 5, and the heat pump 20 which cools the fluid of the upper ending part 10 of the other vertical segment 3 of the converter 1, displacing heat from the upper ending part 10 of the vertical segment 3 to the fluid 23 outside the converter 1, where its external heat exchanger 24 is immersed: when the temperature of the fluid contained in the tank 34 and the temperature of the fluid 23 outside the converter 1 become the same, the two heat pumps 38 and 20 switch off.

The invention thus conceived is susceptible of numerous modifications and variants, all of which being within the scope of the inventive concept.

Furthermore all the details can be replaced by other technically equivalent ones. The materials used, as well as the shapes and the dimensions, may be any according to the requirements without thereby abandoning the scope of protection of the claims.

It has, in practice, been ascertained that the described invention achieves the intended objects and, in particular, the fact is underlined that the convective motions thermoelectric converter provided makes it easier to produce energy starting from the difference in temperature of one or more fluids.

In particular, the fact is underlined that the convective motions thermoelectric converter provided has different characteristics from the known technology mentioned above (OTEC) and overcomes the drawbacks attributable to it, even though it too is based on the use of a fluid the flow of which moves a turbine. The proposed converter consists of a tubular conduit, looped back on itself to form a circuit, with circular section or section equivalent to circular, in which we identify four segments, of which two segments are vertical and two segments, one upper and one lower, are horizontal.

The tubular conduit contains within it a fluid which is heated in a vertical segment and cooled in the other vertical segment so as to create, between the fluid contained in one vertical segment and the fluid contained in the other vertical segment, a temperature difference which generates, in the fluid present in the tubular conduit, convective motions that can be used to produce electricity when the flow of the convective motions is intercepted by one or more turbines connected to one or more alternators or dynamos.

We can first of all observe that in the converter in question the fluids that push the turbine are not expected to change state, i.e., if they are liquids they remain liquid and if they are gaseous they remain gaseous inasmuch as it is based not on changes of liquid- vapor-liquid state but on the creation, inside the device, of convective motions due to temperature differences between two different sectors of the device.

Furthermore, in the preferred embodiment based on the use of a gas-liquid mixture, in some parts of the device there is a single flow path for the gas and for the liquid and in other parts there are two separate flow paths for the gas and for the liquid, both closed with respect to the outside of the device, while in OTEC technology there is a single fluid flow circuit, and in a variant of the technology the flow circuit is not just one only, but is also open.

Finally, for the operation of the device, the gas is only used for its physical characteristics of expansion and contraction according to changes in temperature.

These differences with respect to OTEC technology produce several benefits of the proposed device that we can summarize:

- the device, working in temperature ranges not constrained by fluids that have to change state, can also use temperature ranges other than the range 5°C-30°C, so it can also be used in geographical areas other than the tropical zone and thus have ubiquitous diffusion in the world;

- there is no need to pump sea water because many other fluids can also be used to supply heat, provided they have different temperatures;

- it also works with small fluid masses, unlike OTEC technology which requires huge fluid masses to move the turbine, so it can be small in size;

- it must not necessarily use toxic, flammable or environmentally harmful gases as is the case with OTEC technology.

In conclusion, compared to the current state of OTEC technology, the convective motions thermoelectric converter described herein makes it possible to produce electricity at reduced costs, to have a simple structure, to be relatively easy to implement in practice, with safe and efficient operation and a relatively affordable cost.

Claims

1) Convective motions thermoelectric converter (1) characterized by the fact that it comprises a tubular conduit (101) having a substantially circular section, looped back on itself to form a circuit comprising four segments (2, 3, 4, 5), of which two vertical segments (3, 5) which are substantially vertical and have substantially equal height, and two horizontal segments (2, 4), of which an upper horizontal segment (2) and a lower horizontal segment (4) which are substantially horizontal, containing a fluid (31, 32) inside comprising at least one of a gas (32) and a liquid (31) and a gas-liquid mixture, said fluid (31, 32) being heated in one of said vertical segments (3, 5) and cooled in the other of said vertical segments (3, 5) in order to create, between said fluid contained in a vertical segment and said fluid contained in the other vertical segment, a difference in temperature generating, in said fluid (31, 32) contained in said tubular conduit (101), convective motions usable for the production of electricity, the flow of said convective motions being intercepted by one or more turbines (14) connected to one or more alternators or dynamo.

2) Converter (1) according to claim 1, characterized by the fact that said segments (2, 3, 4, 5) comprise sections of different diameter from segment to segment.

3) Converter (1) according to one or more of the preceding claims, characterized by the fact that said upper horizontal segment (2) comprises a section with a smaller diameter than the sections of said remaining segments (3, 4, 5).

4) Converter (1) according to one or more of the preceding claims, characterized by the fact that it comprises heat exchange means (15, 16, 19), adapted to carry heat from said fluid (31, 32) contained in the upper ending part of one of said vertical segments (3, 5), which is cooled, to said fluid (31, 32) contained in the lower ending part of the other of said vertical segments (3, 5), which is heated.

5) Converter (1) according to one or more of the preceding claims, characterized by the fact that said heat exchange means (15, 16, 19) comprise at least one heat pump (15) adapted to subtract heat from the fluid (31, 32) contained in the upper ending part of one of said vertical segments (3, 5) for the recovery of said heat and heat exchangers (16, 19).

6) Converter (1) according to one or more of the preceding claims, characterized by the fact that said fluid (31, 32) comprises a liquid (31) comprising salts adapted to increase the weight and density of said liquid (31).

7) Converter (1) according to one or more of the preceding claims, characterized by the fact that said fluid (31, 32) comprises a liquid (31) and at least one or more gases (32) subjected to high pressure by their addition to said liquid (31) to form a gas-liquid mixture.

8) Converter (1) according to one or more of the preceding claims, characterized by the fact that it comprises a pipe (13) which connects the apex of one of said vertical segments (3, 5) to the apex of the other of said vertical segments (3, 5), with said pipe (13) which passes over the upper horizontal segment (2), contains only said gas (32) and at its ending parts it has a semipermeable membrane which separates the gas (32) present in said pipe (13) from the gas-liquid mixture (31, 32) which is present in the vertical segments (3, 5), said pipe (13) being adapted to carry gas from the gas-liquid mixture (31, 32) which is at the higher temperature and is present in one of said vertical segments (3, 5), to the gas-liquid mixture (31, 32) which is at the lower temperature and is present in the other of said vertical segments (3, 5), said pipe (13) being equipped with a pump having a compressor adapted to push and compress said gas so as to create a vacuum on the surface of said gas-liquid mixture (31, 32) at higher temperature and an overpressure on the surface of the gas-liquid mixture (31, 32) at lower temperature.

9) Converter (1) characterized by the fact that the fluid (31, 32) contained in the tubular conduit of the converter comprises a liquid having a boiling point which is intermediate between the temperature reached in one of said vertical segments (3, 5), in which the fluid is hotter, and the temperature reached in the other one of said vertical segments (3, 5) in which the fluid is colder.

10) Converter (1) according to one or more of the preceding claims, characterized by the fact that it comprises second heat exchange means (20, 21, 24, 41) associated with said first heat exchange means (15, 16, 19) comprising:

- at least one heat pump (20);

- a heat exchanger (21) associated with one of said vertical segments (3, 5);

- a heat exchanger (24) immersed in an external fluid (23); and

- a fan (41) adapted to direct a flow of said external fluid (23);

said heat exchanger (19) being immersed in said external fluid (23), with said heat exchanger (24) and said heat exchanger (19) which are placed in sequence to intercept said flow for heat exchange between said external fluid (23) and said fluid (31, 32).