WO2016046689A1

WO2016046689A1 - Submerged hydraulic air compressor with flowing water column with water suction pump

Info

Publication number: WO2016046689A1
Application number: PCT/IB2015/057032
Authority: WO
Inventors: Bruno Cossu
Original assignee: Bruno Cossu
Priority date: 2014-09-25
Filing date: 2015-09-14
Publication date: 2016-03-31
Also published as: EP3198138A1

Abstract

The invention relates to a plant - in the basic version thereof, a monobloc machine, fully submerged in the water of the sea or river area where the current energy is to be exploited - designed for producing compressed air through a water flowing column hydraulic compressor, joined or connected to a Venturi water suction pump. The hydraulic compressor basically consists of a motor tube, immersed in the water in vertical position, the lower end whereof opens into a hermetically closed tank, inside which pressure is kept at a value lower than that of the water column above it. For producing compressed air, the plant uses as motor fluid the water overlying the mouth of the motor-tube which (due to the position/pressure energy possessed) flows, through the same, into the tank, forming a water column which, as it descends, increasingly compresses the air at atmospheric pressure flowed by suction inside the motor-tube; in order to achieve the transfer of the water that has made the compression outside the plant, a Venturi tube, which is integral to or is otherwise connected with the tank and which acts as water suction pump for the water collected on the bottom of the same, due to the vacuum caused in the restricted section thereof by the flow of sea or river current which, given the kinetic energy, constantly flows therethrough.

Description

SUBMERGED HYDRAULIC AIR COMPRESSOR WITH FLOWING WATER COLUMN WITH WATER SUCTION PUMP

Description

Foreword

A) As is known, over the past decades, the exploitation of renewable energy sources has become increasingly important as a result of the increasing energy requirements of the world population and the need to reduce dependence on fossil fuels, both because they will run out and because they are a heavy source of pollution. Within these, particular importance has the energy obtainable from sea and major river currents, since it is widely available and almost inexhaustible.

B) Currently, the exploitation of such energy is achieved, above all, with the installation of submerged turbines (both with vertical and horizontal axis) connected to an electric generator or other devices (especially oscillating), designed to use the kinetic energy of the current to directly obtain the conversion of such mechanical energy into electrical energy.

C) A feature and a common limitation of such systems is that:

CI) the same, as a rule, can only use the kinetic energy of currents that have a speed greater than 1 meter per second, as for lower speeds the construction/maintenance/operating cost of the water generator is not cost-effective;

C2) in most cases, they can pick up/use only the energy of the current impinging the water generator (in the case of the turbine, the blades of the same) in the specific place where this is immersed;

C3) the plant (turbine and electric generator) consists of multiple solid components in motion (due to the low speed of the current there is, inter alia, the need to use gear boxes which multiply the number of revolutions of drive shaft), so frequent adjustment, maintenance and repair works are inevitable; C4) not only the turbine (or other device which picks up the energy of the current) but also the electrical system are immersed in water. This involves not only high costs of construction (to ensure, inter alia, full waterproofing of the water generator) but also for repair and maintenance, given the need to move them outside whenever an intervention is required.

Therefore, their yield in terms of costs and benefits is actually very low.

Dl) Conversely, the plant object of the present invention:

D.l.l) consists of very few elements which are sturdy, of simple construction and installation and extremely low cost (in the monobloc version: a motor-tube, a Venturi tube, a tank and two conduits, one for the intake of air at atmospheric pressure, the other for the supply of compressed air to the use/storage point; in the version with Venturi water suction pump separate from the hydraulic compressor there is only an extra connection conduit between the two machines);

D.1.2) all the elements that make up the plant are static machines. Accordingly, since there is no solid member in motion, the adjustment, maintenance and more in general management costs of the plant are almost non-existent and therefore, its life is basically intended to coincide with that of the materials with which its components have been built.

D2) Once installed, the plant operates automatically (irrespective of the current direction therethrough) without any need for intervention by external operators and produces compressed air in a substantially uninterrupted manner.

D3) Provided that the Venturi has a sufficiently large diameter, the plant can also use currents with very low speed.

D4) All the components that make up the plant are completely submerged (except for the tube which, having to suck air at atmospheric pressure, emerges above the free surface of the water), normally over 30/40/50 meters deep, so the system has no impact on the environment, does not interfere with the navigation needs, is insensitive to storm surges. Moreover, since there are no solid members in motion, it does not disturb the marine environment. D5) Hydraulic compressor and water suction pump need not form a single body but they can be installed separately, even at a great distance from each other and at different depths, which allows a wide range of sites to be used, choosing the most suitable ones;

D6) the hydraulic compressor can be installed also at a great distance from the use/storage place of the compressed air produced;

D7) there are no predetermined limits of size for the hydraulic compressor or for the water suction pump but those imposed by the materials used and by the environment in which they can be installed. This allows, inter alia, setting multiple more water suction pumps to serve a single hydraulic compressor (thus using the energy of large current sections) and vice versa;

D8) The production flow of compressed air is continuous, which enables the immediate use of energy without the need for storage;

D9) the hydraulic compressor yield is very high (around 80%) in that the compression takes place in a substantially isothermal manner.

Description

El) The hydraulic compressor, in its basic version, is a monobloc machine consisting of a tube, with the function of motor tube (as the water column which carries out the compression of air which, at atmospheric pressure, flows by suction to the upper part of the tube, is formed and flows down therein); immersed in a (basically) vertical position in the water in the sea or river area where the current energy is to be exploited; shaped in the upper part thereof as (or connected to) a Venturi tube whose restricted section is in communication with the atmosphere through a (suction) tube which emerges above the free surface of the water; which ends in a hermetically closed tank (which has the function of collecting, above the bottom, the water that flows from the motor tube; in the upper part thereof, the compressed water that at the same time has freed), whose internal pressure is maintained at a value lower than that of the water column above it. The tank is crossed in its lower part, but above the bottom, by the restricted portion of a Venturi tube with which it is integral and communicates by means of holes formed around the surface of said restricted portion of the same.

E.2) Of course, depending on the conformation of the place, location, depth and speed of the current it is possible to separate the actual hydraulic compressor (motor tube and tank) from the water suction pump (Venturi tube), installing them in different places and connecting them with a special conduit intended to essentially perform the function of a discharge pipe.

The Venturi water suction pump, in relation to the conformation of the points, can be installed both at a higher and lower height than that at which the hydraulic compressor is placed. Both the water suction pump and the hydraulic compressor can be anchored either directly on the bottom or on a structure resting on the bottom, or on floating structure.

F) The operating principle is as follows:

Fl) in static conditions, when the hydraulic compressor is immersed in water, for the principle of communicating vessels, all submerged parts are filled by the same and the pressure in each point corresponds to that of the water column above it.

F.2) When, instead, the Venturi water suction pump is crossed by the current water, a vacuum is created in its narrower section in consequence of which:

- the water present in the tank enters by suction through the holes provided around the surface of the restricted section of the Venturi water suction pump, within this and is then dragged outside by the water which - due to the current force - crosses the Venturi water suction pump;

- that present in the motor-tube descends towards the tank, replaces the water that has entered into the Venturi water suction pump and is, therefore, in turn sucked inside the same;

- that above the motor-tube enters into the same and replaces the one that has gone, thus starting a process of continuous circulation of the water from outside the plant to the motor-tube; from the motor-tube to the tank; from the tank to the Venturi water suction pump; from the Venturi water suction pump outside the plant. As a consequence of this process, when the water that enters inside the motor-tube passes through the restricted section of the same, the air at atmospheric pressure,

due to the vacuum existing therein (due to the throttle ratio), is sucked inside the motor-tube and is therefore increasingly compressed by the water which, going down towards the tank, drags it with itself, until it exits the tube and is freed of the water in which it was trapped and collects in the upper part of the tank.

G) The pressure value at which the air is compressed corresponds to that existing in the tank, and therefore:

G. l) in the monobloc version, it is slightly higher than that of the water flowing in the restricted section of the Venturi (which, in turn, is a function of the depth at which the same is immersed; of the speed of the current flowing through it, and of the throttle ratio); G.2) if, instead, the water suction pump is installed higher (table 2, letter A), there will be a pressure in the tank corresponding to the sum of the pressures:

- of the height (h\ table 2) of the water column which, through the discharge pipe (Table 2, letter C) connects the tank with the restricted section of the Venturi tube;

- and that of the water flowing in that section;

G.3) if installed lower (Table 3, letter A), by the difference between the pressures of the water flowing in the restricted section of the Venturi tube and that of the height (h\ Table 3} of the water column that falls into the tubing connecting the bottom of the tank with said restricted section.

In all cases, however, the plant operation and the water circulation speed into the same are affected by the fact that the pressure existing in the tank is lower than that of the water column mixed with air which flows therein. The circulation speed is in turn given by the difference between these two pressures, i.e. by the artificial geodetic head created due to the vacuum caused by the current water circulation in the restricted section of the Venturi tube.

H) The plant basically consists of: H 1) A motor-tube

It is the tube (table 1, letter A), substantially a suitably elongated Venturi tube, within which - due to the water that coming down from the upper part thereof towards the tank passes through it without interruption - the compression process of air at atmospheric pressure which, via a suitable (suction) tube - table 1, letter B - flows into its restricted section, takes place.

The motor-tube is immersed in a (basically) vertical position in the water of the site where it is installed and its ends, upper (table 1, letter C) and lower (table 1, letter D), respectively serve as inlet (or feeding) and outlet (or outflow) mouth of the water that must carry out/has carried out the compression.

The upper part thereof is shaped as (or connected to) a Venturi tube; the throttle ratio is determined - taking into account the depth at which the pipe is installed and must work (i.e., the pressure of the water column above its feeding mouth - in such a way that the water that passes through the restricted section is always in depression (this in order to allow air at atmospheric pressure to flow therein by suction). The tube mouth is protected by a mesh (table 1, letter E) which prevents foreign objects from entering therein.

The lower end of the tube opens into the upper part of a hermetically sealed tank (table 1, letter F) in which the separation of the compressed air from the water that has carried out the compression; the collection of the latter on the bottom of the tank; the diffusion of the compressed air in the environment above, take place.

At a suitable distance from the outflow mouth of the tube, and opposite thereto is a plate (table 1, letter G) - joined to the tube through special brackets - against which the water coming out of the same is forced to slam so as to favor the separation of the compressed air from the water in which it was trapped.

The length of the motor tube is independent of the height of the water column above the outflow mouth (in the tank), with respect to which the pipe can be considerably shorter, but in any case respecting, on the one hand - taking into account the diameter and the throttle ratio (which, depending on the depth at which the pipe is immersed, can also be very high) - the dimensions imposed by the conformation of a Venturi tube, on the other hand, the need to lengthen the descending section of said pipe by a suitable length (usually corresponding to half of the entire Venturi tube) to facilitate the compression process. As regards the diameter, there are no predetermined limits to its size but those imposed by the capacity of the water suction pump, or arrays of water suction pumps serving the hydraulic compressor, to transfer outside the plant the water that, in relation to the diameter of the tube and to the speed of the water flowing therein, flows into the tank in the time unit.

As regards the materials and the constructive details, they are selected and determined taking into account both the particular environment (usually marine) in which the plant is installed, and the particular mechanical stresses to which it may be subjected and which in the restricted section of the motor tube (when the same is immersed many tens of meters deep) may also be of significant magnitude, considered that the pressure therein must always and in any case be lower than the atmospheric.

H2) A suction tube

It the conduit (table 1 letter B), normally vertical, connecting the restricted section of the motor-tube with the atmosphere, emerging above the water surface above the plant, so as to allow a constant air intake when the plant is in operation. Its upper end is maintained above the surface by a floating body to which it is joined, it is normally made of flexible material (table 1, letter H).

H 3) A tank

It is the hermetically closed chamber (table 1, letter F) in which the motor tube leads and where the following take place: the separation of the compressed air from the water that has carried out the compression; the collection of such water above the bottom of the tank; and the diffusion of the compressed air to the environment above. A supply conduit (table 1, letter I) connects the upper part of the tank, where the compressed air collects, with the place where the same will be used or stored.

In the monobloc version, the tank is crossed in its lower part and above the bottom by the restricted part of the Venturi suction pump - (table 1, letter L) which, therefore, has its support bases in the tank walls themselves.

The restricted section of the Venturi tube is fully immersed in the water that collects on the bottom of the tank; several holes are formed all around its surface (table 1, letter M) through which the water in which it is immersed is sucked inside and then transferred outside the plant.

In the variants with water suction pump separate from the hydraulic compressor (tables 2 and 3, letter A), the lower part of the tank (tables 2 and 3, letter B) is connected with the restricted section of the same via a suitable pipe/conduit (table 2 and 3, letter C) which serves as drain pipe for the water collected on the bottom.

The pressure existing in the tank is that indicated at point G.

Both in the monobloc version and in the other versions, the tank normally also has the function of being the anchoring point of the hydraulic compressor either directly on the bottom of the sea (or river, if sufficiently deep) or on a special structure resting on the bottom. For this reason, it is made with heavy material, e.g. concrete. The shape of the tank can be the most varied (normally domed), in any case suitable for enabling the separation of compressed air from the water and the collection of the same in the upper part of the tank.

H 4) A water suction pump

As already said, it is simply a Venturi tube (table 1, letter L) which can work as a water suction pump as a result of the vacuum created in its restricted section due to the speed of the water which, due to the kinetic energy of the current, passes through it constantly. When the current speed is not sufficient to allow the natural flow inside the Venturi tube of the amount of water required for a profitable use thereof as water suction pump, a circulation pump (table 4 letter a') is installed in the mouth thereof, operated by a coaxial turbine (table 4, letter b') mounted therewith (preferably) at the other end of the Venturi, which uses the kinetic energy of the water flowing all around the Venturi for its operation. If the hydraulic compressor is intended to work by exploiting the sea currents, the Venturi water suction pump will be shaped so as to be able to use the energy of the same, irrespective of the direction of the current flowing through it.

H 5) An outlet tube

This is the conduit (tables 2 and 3, letter C) connecting - when the water suction pump is not integral with the hydraulic compressor - the bottom of the tank with the restricted section of the Venturi tube, so as to allow the suction inside the Venturi tube and the release to the external environment of the water collecting on the bottom of the tank.

H 6) A supply conduit

This is the tube (table 1, letter I) connecting the top of the tank (table 1, letter F) with the place where the compressed air that is constantly produced is used or stored. Of course, if the tube serves multiple hydraulic compressors, it will be divided into as many branches as the same.

The construction material of the tube must be such as to withstand the pressures to which it is subjected.

Claims

A plant for generating compressed air, comprising a submerged hydraulic compressor with flowing water column connected to at least one Venturi water suction pump (TAB. 1, letter L), characterized in that the hydraulic compressor includes:

- at least one motor-tube (TAB. 1, letter A) immersed in a substantially vertical position with respect to the flow of the sea or river water whose current energy is to be exploited, shaped as or connected to, in the upper part (TAB. 1, letter C), a Venturi tube, whose restricted portion is directly connected to a suction tube (TAB. 1, letter B) for the air at atmospheric pressure, the latter having a free end (TAB. 1, letter H) emerging on the water surface and is placed in direct contact with the atmospheric air;

- a tank (TAB. 1, letter F), inside which, in the upper part, at least one tube-motor ends (TAB. 1, letter A); in the lower part, inside the tank (TAB. 1, letter F), the water that has compressed the air upon exiting from said motor-tube (TAB. 1, letter A) is collected; while in the upper part of said tank (TAB. 1, letter F), the produced compressed air is collected;

- the water suction pump (TAB. 1, letter L) consists of a Venturi tube whose restricted portion is placed and connected with the inside of the tank (TAB. 1, letter F), at the flooded lower part of the latter, due to a plurality of holes (TAB. 1, letter M);

said plant further comprising a conduit for supplying the compressed air (TAB. 1, letter I) from the upper part of the tank (TAB. 1, letter F) filled with compressed air towards a storage or use place thereof;

the whole plant for the generation of compressed air being immersed in water except for the free end (TAB. 1, letter H) of the suction tube (TAB. 1, letter B), which is in contact with the atmospheric air.

A plant for generating compressed air according to claim 1, characterized in that at least one Venturi water suction pump (TAB. 2 and 3, letter A) is placed on the outside of the tank (TAB. 2 and 3, letter B) and provided with a tube of appropriate length (TAB. 2 and 3, letter C) placing the bottom of the tank (TAB. 2 and 3, letter B) directly in communication with the restricted portion of the Venturi water suction pump (TAB .

2 and 3, letter A).

3. A plant for generating compressed air according to any of the preceding claims, characterized in that the tank is shaped as a dome.

4. A plant for generating compressed air, according to any of the preceding claims, characterized in that one or more Venturi water suction pumps include a pump which promotes water circulation therein, said pump being installed preferably in the mouth of the water suction pump, driven by a turbine coaxial therewith which uses the kinetic energy of the water of the current flowing all around the Venturi water suction pump for its operation.

5. A plant according to any of the preceding claims, characterized in that the free end of the atmospheric air suction tube (TAB. 1, letter H) emerging from the free surface of the water is kept above said surface by a floating body.

6. A plant according to any of the above claims, characterized in that said the tank is made of heavy material, such as concrete, and rests directly on the bottom of the sea or river, or is supported by - or anchored to - a special support structure.

7. A plant according to any of the preceding claims, characterized in that each mouth of the motor-tube(s) is protected by a mesh (TAB. 1, letter E) which prevents foreign bodies from entering therein.

8. A plant according to any of the preceding claims, characterized in that the lower end (TAB. 1, letter D) of the motor-tube (TAB. 1, letter A), opposite the mouth of the same, has a sheet (TAB. 1, letter G) joined to the motor-tube by means of special brackets, against which the water coming out vertically from the motor-tube is forced to slam, facilitating the separation of the compressed air from the water.