WO2013017901A1

WO2013017901A1 - System and method for producing electrical energy

Info

Publication number: WO2013017901A1
Application number: PCT/HU2012/000051
Authority: WO
Inventors: János KOÓS; K. Attila SZALÓKY
Original assignee: IMK GREENPOWER KFT
Current assignee: IMK GREENPOWER KFT
Priority date: 2011-08-02
Filing date: 2012-06-15
Publication date: 2013-02-07
Anticipated expiration: 2014-02-02

Abstract

The invention is an electric power generating system, comprising an energy cell (26) having an inner space, the energy cell (26) comprising an anode and a cathode arranged in the inner space with a spacing suitable for receiving an electrolyte liquid, an inlet (24) leading the electrolyte liquid into the inner space and an outlet (31) draining the electrolyte liquid from the inner space, and the system further comprises a receiving container (21) connected to the outlet (31), a buffer tank (18) connected to the inlet (24) and suitable for temporary storage of the electrolyte liquid to be led into the energy cell (26), a flow-through regulating valve (22) regulating the admission of the electrolyte liquid from the buffer tank (18) into the energy cell (26) and a control means controlling the flow-through regulating valve (22) in accordance with the load of the electric power generating system. Furthermore, the invention relates to a method for generating electric power by applying said system. (Fig. 1)

Description

SYSTEM AND METHOD FOR GENERATING ELECTRIC POWER

TECHNICAL FIELD

The invention relates to an electric power generating system and a method for generating electric power.

BACKGROUND ART

A large volume of seawater and wastewater is available on the Earth. The treatment and appropriate disposal of wastewater require substantial resources and investments. Because of the huge saltwater and wastewater reserves, there are numerous known solutions to utilise these media for generating energy.

In Norway, such an experimental osmotic power plant is in service, where fresh water and saltwater are fed through a special membrane to generate electric power. This experimental power plant was set up by the Statkraft company. The power plant is able to generate an output of 2 to 4 kW only, on a two thousand square meter membrane surface, which is roughly sufficient to power a coffee maker. The apparatus is used to test the future applicability of this technology. The basic principle of running this experimental power plant is that through the membrane separating the fresh water from the saltwater, thanks to the osmotic pressure, water flows from the fresh water side to the saltwater side, which generates an overpressure on the saltwater side for driving a power generating turbine. The company running the equipment envisages starting to build a commercial scale osmotic power plant of 25 MW output in 2015, which will be able to meet the energy demand of about 30 thousand households, and it will have a membrane of a football stadium size. A precondition of starting commercial scale power production is increasing the energy generating efficiency of the membrane from the current 1 W/m² to 5 W/m², which would raise the costs of osmotic power generation to the average level of renewable energy sources.

When research started in the late 1990's, the efficiency indicator was only 0.01 W/m². The most advanced technology known today enables the generating of a 2 to 3 W/m² output. After running the system in, it is planned to replace the currently applied membrane by the most advanced model in the experimental equipment. The NASA (National Aeronautics and Space Administration) has also contributed to the developing of a membrane suitable for generating power. The NASA is primarily interested in the osmosis membrane technology to be able to recycle water in space stations.

Generating power on the basis of the osmosis principle as described above is only possible at places where fresh water flows into the sea. The osmosis power generating capacity in Europe can be estimated to be 180 terawatt-hours annually, which is about 5% of the total energy consumption. The commissioning and installation cost of osmotic power plants is extremely high because of the membrane applied. Other technologies based on reverse electrodialysis and osmosis are also known.

A saltwater or urine refillable battery called MetalCell is also known, which is a technologically more advanced version of the so-called Baghdad battery used in the ancient times. This battery has been developed for military applications and actually functions as a small emergency battery, which is suitable for supplying power to a portable computer for a few hours. It can be refilled with saltwater, but its lifetime is limited because the magnesium applied in the battery deteriorates. In a dry condition it can be stored for an unlimited period of time, therefore it is advisable to fill it up only immediately prior to application. The development of the battery was not aimed at generating a higher amount of energy; its technical dimensions are limited and therefore it is not suitable for mains electricity supply.

In another known solution (J. Woodall, Purdue University), wastewater or saltwater can be turned into purified water while obtaining electric power in the process. Wastewater or saltwater is reacted in a reactor consisting of metal alloys to split it into its components and the generated hydrogen is supplied to a fuel cell. In this fuel cell, the hydrogen reacts with the oxygen of the air and is turned into water again, while generating electricity from the chemical energy. The alloys applied in the reactor are to be selected in a way that the reaction temperature is sufficiently high to generate steam. In this case, the water produced becomes free of bacteria, i.e. the water generated after condensation can be applied as potable water. An alloy consisting of aluminium, gallium, indium and tin is used in the reactor. Without any further activation, this alloy enters into fierce reaction with water, dissociating it into hydrogen and oxygen. The process may be based on wastewater, contaminated groundwater or seawater. As a by-product, mainly aluminium hydroxide is created, which can be found also in nature in various minerals - consequently the disposal of this by-product is not a problem. The reactor to be built would weigh less than 50 kg according to the plans. To generate one litre of potable water or electric power by this method - in comparison with the operating costs of a power plant and a pipeline network built on site - would be extremely favourable. There are also experiments to utilise the energy of waves, and these developments are aimed at using the mechanical and kinetic energy of the sea. However, kinetic energy cannot be regulated, and hence for example in stormy or very calm weather the volume of energy that can be generated varies within a broad range. This approach is similar to the harnessing of wind energy. Because of the heavily corrosive impact and other chemical effects of saltwater and the uncertain availability of wave energy as mentioned above, the development is costly and progress is difficult. Developers have been able to achieve no or only limited operation on a prolonged basis. In US 3,635,764 an energy cell using wastewater as electrolyte is disclosed, and its anode comprises more than 90% magnesium and additionally aluminium and zinc. In the energy cell, the cathode is a so-called air cathode and the energy cell is described to be of household dimensions, with an energy cell volume of about 400 ml. According to the document, the electrolyte is fed into the inner space of the energy cell through an inlet, and then it is kept between the electrodes for a specified period, followed by being drained into a receiving container. The dissolved materials are removed in the receiving container from the drained electrolyte. According to US 3,635,764, the flow rate of the energy cell and the retention time in the energy cell are optimised to make sure that the solids, salts and contaminants dissolved in the electrolyte liquid are removed at as high a proportion as possible from the wastewater. In CA 1 ,324,812 an energy cell using saltwater as electrolyte is disclosed. In the energy cell according to the document, the anode used is made of a material which contains approx. 6% aluminium and 3% zinc in addition to magnesium, and the cathode material contains approx. 20% chrome, 18% nickel and 6% molybdenum. In US 3,012,087 a seawater electrolyte energy cell is disclosed, in which the electrolyte is continuously circulated. The ratio of fresh seawater and the seawater circulated within the system is determined as a function of the output voltage of the energy cell. A circulating energy cell is also disclosed in US 3,629,075. An energy cell designed for treating wastewater is disclosed in WO 01/04061 A1.

In the energy cell disclosed in KR 20030059030, the electrolyte is saltwater with an anode comprising magnesium, aluminium and zinc, and a cathode comprising nickel and titanium oxides.

In CN 154300 A an energy cell using seawater as electrolyte is disclosed, the anode of which is a magnesium alloy. In US 3,766,045 an energy cell using flow-through seawater as electrolyte is disclosed. An energy cell is disclosed in US 5,702,835, which uses sewage sludge compost as electrolyte and has an anode of zinc and a cathode of carbon.

In WO 03/034521 A1 an energy cell is disclosed, in which the anode contains not less than 93% magnesium, 0 to 7% aluminium, 0 to 3% zinc and 0 to 2% manganese. In CN 201317811Y the application of an anode is disclosed which is made of a magnesium-aluminium-zinc alloy. The energy demand of various consumer groups may vary in different periods of the day or it may vary with other periodicity. It is a common disadvantage of prior art systems that none of the known systems is suitable for practically continuous electric power generation in a way that this is adjusted to the emerging consumer requirements.

DESCRIPTION OF THE INVENTION

It is an object of the invention to provide a system and a method for generating electric power, which is free of the disadvantages of prior art solutions.

It is a further object of the present invention to provide a system suitable for generating electricity, which can be controlled in accordance with varying consumer requirements and load, i.e. the electric power produced by the system can be varied for example on the course of the day or in accordance with other schemes - on the basis of consumer requirements. A still further object of the invention is to provide a method for generating power by this system.

In the system and method according to the invention as defined in claim 1 and claim 20, respectively, the volume of liquid introduced into the energy cell per unit of time can be controlled by means of a flow-through regulating valve, thus the rate of passing of the electrolyte liquid through the energy cell can be regulated. In case of a higher consumer load, the flow rate of electrolyte liquid through the energy cell can be increased, thereby raising the amount of generated electric power. Therefore, using the system according to the invention, the electric power generated by the system can be varied in time by means of controlling the flow-through regulating valve.

A further object of the invention is to remove materials from the electrolyte - i.e. from the seawater or wastewater - which would pollute the environment. A further object of the invention is to provide an anode and cathode pair in the energy cell, for which the anode consumption is minimized. An object of the present invention furthermore is to apply an anode and cathode pair having the possible highest electric potential difference, while the environmental pollution caused by them and the investment costs are as low as possible.

BRIEF DESCRIPTION OF DRAWINGS

Preferred embodiments of the invention will now be described by way of example with reference to drawings, in which:

Fig. 1 is a schematic view of an embodiment of the electric power generating system according to the invention;

Fig. 2 is a schematic view of the receiving container applied in an embodiment of the system according to the invention;

Fig. 3 is a schematic view of the energy cell applied in an embodiment of the system according to the invention;

Fig. 4 is a schematic view depicting the connections between the parts of an embodiment of the electric power generating system according to the invention;

Fig. 5 is a block diagram of the control means used in the system according to the invention; and

Fig. 6 is an operational flow chart of the first block of the block diagram shown in Fig. 5.

MODES FOR CARRYING OUT THE INVENTION

In Fig. 1 an embodiment of the electric power generating system according to the invention is shown. In this embodiment, the electric power generating system comprises an energy cell 26 having an inner space. The energy cell 26 comprises in the inner space an anode and a cathode arranged with a spacing suitable for receiving an electrolyte liquid, and an inlet 24 leading the electrolyte liquid into the inner space and an outlet 31 draining the electrolyte liquid from the inner space. The inlet 24 and the outlet 31 may be for instance an inlet or outlet opening or an inlet or outlet stub. The system furthermore comprises a receiving container 34 connected to the outlet 31 , a buffer tank 18 connected to the inlet 24 and suitable for temporary storage of the electrolyte liquid to be led into the energy cell 26, a flow-through regulating valve 22 regulating the admission of the electrolyte liquid from the buffer tank 18 to the energy cell 26, and a control means controlling the flow-through regulating valve 22 in accordance with the load of the electric power generating system. Accordingly, due to the use of the flow-through regulating valve 22, the inventive system becomes suitable to meet the energy consumption requirements. In this embodiment, the buffer tank 18 is arranged with respect to the inlet 24 so as to enable gravitational flow of the electrolyte liquid through the inner space of the energy cell 26. It is shown in the figure that the buffer tank 18 is connected to the inlet 24 via a pipe 20 and that the flow-through regulating valve 22 is arranged on the pipe 20. For example, the buffer tank 18 is a spherical watertank, i.e. a water storing tower. It is the function of the buffer tank 18 to accumulate the electrolyte liquid. It is required for the buffer tank 18 to be resistant to corrosive impacts and that it should have a storing part of appropriate size.

In other embodiments, in which the buffer tank is directly connected to the inlet 24, the flow-through regulating valve 22 can also be arranged on the inlet 24. In further embodiments of the system, the flow-through regulating valve may also be arranged between the inlet 31 of the energy cell 24 and the receiving container 34, for example arranged on a pipe 32 connecting the outlet 31 and the receiving container 34. In some embodiments of the system according to the invention, in which the arrangement of the buffer tank with respect to the inlet 24 does not allow the gravitational flow of the electrolyte liquid through the energy cell 26, the feed of the electrolyte liquid from the buffer tank to and through the energy cell 26 necessitates external energy supply. It is a requirement against the pipes applied in the system according to the invention to be resistant against corrosion effects caused by the electrolyte liquid.

The size of energy cells is decisively determined by the volume of energy intended to be generated. The concentration of electrolyte liquid is to be taken into consideration in the energetic dimensioning of the energy cells. In dimensioning the energy cells, the following approximate data are to be taken into consideration: 1 dm² anode and cathode surface is able to provide an output of approx. 0.1 W, when a saline solution of 0.3% concentration is applied as an electrolyte liquid. Furthermore, in the present embodiment, the electric power generating system comprises a source 10 connected via a pipe 16 to the buffer tank 18, and a pump 14 arranged on the pipe 16 for supplying the electrolyte liquid from the source 10 to the buffer tank 18. The operation of the pump 14 is typically intermittent. Due to the intermittent operation, it must well tolerate the increased electric load caused by switching the unit on and off repeatedly, it must resist to corrosive effects and preferably it should have low electric power consumption. It is noted that the energy used by the pump 14 - in the case of a well dimensioned energy cell 26 - is at least one order lower than the volume of energy generated by the energy cell 26. A filter is arranged between the source 10 and the buffer tank 18 to remove solid contaminants from the electrolyte liquid coming from the source 10.

The operation of the energy cell is based on a phenomenon being the basic principle of other batteries. The main point of the operation of batteries is that resulting from the difference of metal potential of the electrodes arranged therein, a low power current can be obtained from the electrolyte held in the space between the electrodes, and the magnitude of this current depends on the quality of the electrolyte.

In selecting the anode or cathode material, it is an important that their material has as high potential difference as possible in a positive or negative direction in relation to the zero hydrogen potential. The electrodes to be described below - the anode and the cathode - shall have a high potential difference in relation to the hydrogen, as the zero potential material. In our experiments, we have found that in case of the present energy cell, preferably a magnesium-aluminium-zinc alloy may be applied to serve as an anode. In order to achieve the best efficiency and the longest lifetime, the material is to be preferably alloyed in a way that it contains 91% to 96% magnesium, 3% to 6% aluminium and 1 % to 3% zinc. In our experiments, the smallest anode degradation was found by the application of an alloy containing 91 % magnesium, 6% aluminium and 3% zinc.

In course of the electricity generating procedure, this anode behaves as a so-called "degradation" anode, as in the course of the chemical reaction, it is able to form a compound with the salts contained in the electrolyte liquid. Therefore, as a result of the anode degradation, the separation of solids in the electrolyte liquid is experienced. The degradation of the anode is largely influenced by the cathode material. We have found in our experiments, that especially the application of the below described two materials as a cathode influences beneficially the degradation of the anode.

For the anode made of a magnesium-aluminium-zinc alloy, preferably a high purity graphite plate is applied as a cathode. This high purity graphite plate preferably has the following features. Its purity is preferably in the range of 95% to 99.8%, consequently it provides the most advantageous characteristics if its contamination is less than 5%. The thickness is preferably in the range of 0.4 to 4 mm, the use of a thicker plate is not necessary and would not be cost efficient either. In order to reach the appropriate strength a thickness of 0.4 mm is to be reached. By the application of the anode consisting of a magnesium-aluminium-zinc alloy, a cathode made of a nickel-titanium alloy may be applied as well. To achieve the best efficiency, the nickel-titanium alloy is to be combined, alloyed with other materials to comprise less than 0.08% carbon, 1.00% silicon, 2.00% manganese, 0.045% phosphorus, 0.015% sulphur, 17.0% to 19.0% chromium, 9.00% to 12.0% nickel and 0.70% titanium of 5XC purity.

According to our experiments, the application of high purity graphite or a nickel- titanium alloy cathode results in the smallest anode degradation. These alloys enable in a cost efficient way to provide an electric power plant by means of the electric power generating system according to the invention.

In the course of the reaction between the anode and the mineral salts, a so-called 'flocculation' is generated, as well as other materials are produced which are dissolved in the electrolyte liquid. Applying an anode comprising mostly magnesium as described above, the 'flocculation' is magnesium oxide - a granular material. This precipitation, by-product has no detrimental effect on the environment, it can be separated and recycled through the application of a precipitator and a filter. When using an anode mostly made of magnesium, as a result of the reaction with the electrolyte liquid, magnesium chloride is generated as another by-product. Magnesium chloride is a water soluble material, and it can be found in large quantities in typical electrolyte liquids. Consequently, the appearance of magnesium chloride as a result of anode degradation is not a negative effect, because with the usual anode degradation this material is not produced in such a large volume that it would represent a load to the environment.

The anode for instance may be of Mg, Al, Zn, Ca, Zr, Cu, In, Si, Ti, B, Ce, or an alloy those of, and it may also comprise carbon; and the cathode may be for instance stainless steel or a material comprising some kind of metal halogen, chloride, bromide, fluoride, iodide, copper chloride, silver chloride or titanium. The material used as a cathode is a reducing agent compound, and the material used as an anode is an oxidising compound. The most important consideration in selecting the materials making up the anode and the cathode is that the compounds generated in the electrolyte liquid should represent the lowest possible contamination risk or danger to the site of application and the environment. In selecting the materials, the other important consideration is the cost efficient replenishing of the materials, with special regard to the anode. Preferably, the electrodes are separately arranged in the cell, and a separator is arranged between each anode and cathode pair. The purpose of separation is to prevent direct contact between the anode and cathode. The direct contact between the anode and cathode would cause a short circuit, as a result of which the operating efficiency of the energy cell would be greatly reduced or in certain cases fully broken off. The separator is preferably designed in a form of a bag, and it is arranged to surround the anode. The so arranged separator retains the particles escaping from the anode, secures to maintain the purity of the electrolyte, and due to its application the anode degrades slower, as the particles of the material making up the anode cannot separate physically from the surface of the anode. By using a bag-shaped separator, the lifetime of the anode is extended. Since a lower volume of solid byproduct leaves the anode, the efficiency of settling and filtering is also enhanced by the application of the bag-shaped separator. In our experiments, we have found that the following materials can be preferably applied as a separator. The separator is preferably made of a pressed honeycomb structure of polyester composite material, the water permeability of which is more than 80%. This material corresponds to a SORIC SF3 material according to an international standard.

The major characteristics of the material are as follows:

Fibre material: PET (Poly(ethylene-terephthalate))

Binding of the mesh surface: concentration above 96%

Relative density: 0.05 g/cm³ to 0.07 g/cm³

Structure: honeycomb structure

Solubility: in water - insolvable

in fat - insolvable Furthermore, the material of the separator may be a polypropylene-based, needle felted, non-woven geotextile with a heat treated surface. This material due to its dense fibre structure, efficiently captures the small particles leaving the anode. The liquid permeability is higher than 80%. For example, the density of the applied material is 100 g/m², and the thickness is between 1 mm and 2 mm.

As a result of the anode degradation detailed above, segregations and solid contaminations may be formed in the electrolyte liquid drained from the energy cell 26. In order to collect these contaminations, the receiving container 34 comprises an inlet 33 leading the electrolyte liquid into its inner space, and an outlet 35 draining the electrolyte liquid from its inner space. Between the inlet 33 and outlet 35 of the receiving container 34 a precipitator is arranged - for instance of cascade and multistage design - for filtering the solid materials from the flowing-through electrolyte liquid, and the outlet 35 of the receiving container 34 is connected to the source 10. In this embodiment, the outlet 35 of the receiving container 34 is connected to the source 10 via a pipe 38 and a pump 36 is arranged on the pipe 38 for forwarding the electrolyte liquid from the receiving container 34 to the source 10. The electrolyte liquid drained gravitationally from the energy cell 26 passes through the precipitator. As a result of the cascade design, the precipitator collects efficiently the solid contaminations from the electrolyte liquid, for example the solids that were got into the electrolyte liquid from the anode.

In the present embodiment, between the inlet 33 and the outlet 35 of the receiving container 34, preferably in the flow path of the electrolyte liquid, after the precipitator, a filter for filtering the solid materials from the flowing electrolyte liquid is also arranged. In other embodiments, the precipitator and the filter, respectively, can be applied by itself, instead of a combination of the two. The filter can be a single filter or a series of filters which let through the many increasingly smaller grain sizes and is (are) arranged in the flow path of the electrolyte liquid. Such an arrangement of the precipitator and a series of filters is advantageous, because in this way by means of the precipitator first the largest grain size solids are filtered, and then by means of the filters letting through the increasingly smaller grain sizes and arranged one after the other, the smaller grain size solids are also filtered and removed from the electrolyte liquid. The solid components may be segregations or other contaminants as well. If the filter is arranged after the precipitator, the filter filters those pollutants which remained in the electrolyte liquid once the electrolyte liquid passed through the precipitator. In other embodiments, the electrolyte liquid - after having passed through the energy cell and having been screened by means of the precipitator and the filter - is let out to the environment through the outlet of the receiving container. If the electrolyte liquid is wastewater, the source 10 is for instance a wastewater reservoir, and if the electrolyte liquid is seawater, then the source 10 is a saltwater reservoir, which may even be the sea. Accordingly, the primary task of the filter is to make sure that during the re-disposal of the exhausted electrolyte liquid into the environment, the eventual contaminants in the electrolyte liquid are blocked from passing into the environment, and also the enrichment of possibly present minerals, salts and metals is hindered at the place of re-disposal in the electrolyte liquid after passing through the energy cell. The materials appearing as pollutants in the electrolyte liquid are mostly present in the nature as well, because most of them were already in the electrolyte liquid when it was taken from the source for the purpose of generating power. Therefore, letting out of these materials into nature would only represent a risk if their concentration was higher than the original one emerged as a result of re-depositing the exhausted electrolyte liquid, because this could upset the equilibrium of eco-flora and eco-fauna. Therefore, preferably the enrichment of concentration is to be avoided. The solid contaminants captured by the precipitator as well as the filter, comprising for instance metal salts, precipitated salt and magnesium salt, are preferably subjected to further processing. The captured solids - partly or fully - are collected in the vessels arranged below the precipitator and the filter, where it is introduced through an aperture designed for this purpose in the receiving container 34. The solid contaminants got into the vessel still comprise a substantial volume of moisture, characteristically 15%. The solid contaminant is removed from the vessel by means of a so-called sludge pump, and then the wet content is further reduced by being processed on pressure filters. The liquid resulting from pressure filtering can be preferably fed back into the system, for example combined with the filtered electrolyte liquid so that the electrolyte liquid drained with the solid contaminants does not cause a loss.

The low moisture content solids captured by pressure filters are stored in so-called cakes. The cakes obtained can be recycled by further processing, for example by using metallurgical procedures. The electrolyte liquid treated in the steps detailed above and returned to the source 10 is mixed with the fluid in the source 10 and when it is so charged, it becomes suitable for re-application, and therefore the system according to the invention practically implements a cycle from the aspect of the liquid applied as an electrolyte liquid. If the source 10 is sufficiently large, for example a sea, then the charging of the electrolyte liquid can be ensured even if the electrolyte liquid is obtained from a place further away from the re-disposal site.

Fig. 2 shows the inner structure of an exemplary receiving container 21 comprising a precipitator 25 and a filter 27. The multi-stage cascade design shown in the figure ensures that the solid contaminants settle from the electrolyte liquid flowing in through an inlet 23 of the receiving container 21 at the points where the pipe system making up the precipitator 25 is curved. The cascade design practically means that U-shaped pipes so-called cascade vats are placed side by side, which are connected at the top. As a result of gravitation, the solid particles will settle at the bottom turning points, consequently at the bottom part of the U-shaped pipes. A filter 27 is arranged at an outlet 29 of the receiving container 21. The more U-shaped pipe components make up the precipitator 25, the better efficiency of the removal of solid contaminants from the electrolyte liquid can be reached. Generally, the fitting of 4 or 5 U-shaped pipes proves sufficient to meet the current environmental regulations.

The operation of the electric power generating system according to the invention is not influenced by environmental and climatic factors, because the freezing point of an electrolyte liquid which is sufficiently saturated with free ions, consequently having an appropriate salt content is well below the freezing point of water. Therefore, the applicability can be very broad, considering the technical installation limits imposed by the distance from the source. Electric terminals 28' and 28" of the anode and cathode of the energy cell 26 are shown in Fig. 1. The energy generated by the electric power generating system can be obtained through the electric terminals 28' and 28". Preferably, an electric power handling means may be connected to the electric terminals 28', 28" so that the voltage appearing on the electric terminals 28' and 28" is transformed to the appropriate level and shape. By applying an electric power handling means, the system according to the invention can be made suitable for feeding power into a high voltage mains system.

The electric terminals 28' and 28" must be arranged with appropriate galvanic connections considering the heavy chemical and corrosive effect of the electrolyte. The material of the electric terminals 28' and 28" and that of the other electric wires applied in the energy cell 26 may not compose a galvanic battery at their joints. In case of this phenomenon this would be detrimental to the efficiency. It is advisable to use an airtight separation between the electric terminals 28' and 28" and the electrolyte liquid.

A valve 39 arranged on a pipe 41 is also shown in Fig. 1 , by means of which the electrolyte liquid can be drained from the whole system without having passed through the energy cell 26. The inlet of the pipe 41 is connected to the pipe 20 and the outlet of the pipe 41 is connected to the pipe 32. Furthermore, in the present embodiment a gas deflector 30 is connected to the inner space of the energy cell 26, in order to remove gases eventually generated in course of the processes taking place in the energy cell 26. In case of using wastewater for the electrolyte liquid, methane gas may be released, which is to be removed.

The electrolyte liquid may be seawater because of its natural salt content. In order to obtain electric power optimally, the electrolyte liquid preferably contains 0.7% to 4.4% dissolved salts, for example sodium, magnesium, chlorine or sulphate or other dissolved minerals, for example phosphor, nitrogen, calcium carbonate or silicon oxide. The salt content may deviate from the specified range, but in case of a salt content below 0.7%, a too high flow rate should be applied in order to ensure appropriate power generation. In case the salt content is much higher than specified, i.e. above approx. 10%, the salt may be crystallised undesirably.

The salt and mineral content of the electrolyte liquid determines the free ion content of the electrolyte liquid. Therefore, in the flow path of the electrolyte liquid a potential measuring device (not shown) is arranged for measuring the potential difference of the electrolyte liquid in its flow path, and furthermore in the flow path of the electrolyte liquid between the potential measuring device and the inlet 24 an additive-feeder is arranged for regulating the salt and mineral content and thus the free ion content of the electrolyte liquid in accordance with the potential difference thereof. The additive- feeder is preferably designed as a container, into which the electrolyte liquid is fed from the source, and in the container the appropriate additive is mixed with the electrolyte liquid. Following the addition the electrolyte liquid is supplied from this container into the buffer tank by means of a pump, for example with the pump 14 in Fig. 1. The potential measuring device and the additive-feeder may also be arranged between the buffer tank and the energy cell, in the flow path of the electrolyte liquid.

Seawater represents the lowest cost electrolyte liquid, because in case of electric power generating systems installed on seashores, seawater is available practically in an unlimited volume. The dissolved salt content of seawater makes it suitable for application in the system as an electrolyte liquid. In addition to the materials listed, all pollutant containing liquids can be applied as an electrolyte liquid in the electric power generating system according to the invention, on condition it contains an appropriate amount of free ions or the free ion content of which can be appropriately enriched by additives, thus an electric charge can be removed therefrom. From such an aspect, communal wastewater or other industrial wastewater is suitable for application as an electrolyte liquid, but it must be subjected to an enhanced filtering procedure prior to introducing into the electric power generating system, and the free ion content is to be examined, and if necessary, other additives are to be added.

Fig. 3 shows the inner structure of an exemplary energy cell 58, in sectional view. The electrolyte liquid is introduced into an inner space 60 of the energy cell 58 via an inlet 40. The flow path of the electrolyte liquid is shown by arrows in the figure. In the energy cell 58 a plurality of anodes 50 and for each anode 50 a cathode 48 is arranged, and between each pair of anode 50 and cathode 48 a separator 52 is arranged. The separator 52 is shown schematically, and preferably it is designed in a bag shape surrounding each of the anodes 50, respectively. According to Fig. 3, the electrolyte liquid flows towards the outlet 42 through the inner space 60 of the energy cell 58 divided by the anodes 50, cathodes 48 and separators 52. In the space divided by the anodes 50, cathodes 48 and separators 52 turbulences and circulations may arise, which increase the retention time of the electrolyte liquid in the inner space 60, thereby facilitating the reaction of free ions with the anode 50 and the cathode 48 in the highest possible rate. Accordingly, by the presence of turbulences, the electrolyte liquid is exhausted in a larger extent, thus its free ion content is reduced in larger extent. The forming of turbulences and circulations may also be facilitated by the fact that when the electrolyte liquid reacts with the anode 50 and the cathode 48, respectively, the free ion content of upper layers of the electrolyte liquid is lower, and the specific weight of the electrolyte liquid varies in the space between the electrodes. If the electrolyte liquid is gravitationally introduced from the buffer tank into the energy cell 54, then the electrolyte liquid leaves the outlet 42 in accordance with the weight of the liquid column from the buffer tank, consequently the weight of the liquid column forces the electrolyte liquid through the energy cell 54. If the system does not operate gravitationally, external energy is to be applied. Fig. 3 shows that the anodes 50 and the cathodes 48 are connected at connection points 54 to electric terminals 56' and 56", respectively. The outlet 42 branches off, i.e. to a pipe 44 and to a gas deflector 46. The outlet 42 is connected to a receiving container through the pipe 44.

Fig. 4 shows an operating scheme of an embodiment of the system according to the invention. Fig. 4 shows the connections between the various units forming the system. The electrolyte liquid passes through the components of the system as follows. The electrolyte liquid is supplied from a source 62 of the electrolyte liquid by means of a pump 64 into a buffer tank 66. From the buffer tank 66, the electrolyte liquid is supplied to an energy cell 70 via a flow-through regulating valve 68. After flowing through the energy cell 70, the electrolyte liquid is fed across a precipitator 72 and a filter 74 or through a system of filters as described above. By means of the precipitator 72 and the filter 74 the electrolyte liquid is separated into filtered-out materials 78 and filtered electrolyte liquid 82. In this embodiment, the filtered electrolyte liquid 82, which no longer contains materials polluting environment 84, is disposed to the environment 84. Finally, the filtered-out materials 78 are prepared for recycling 80.

Fig. 4 shows that a control means 76 is connected to the pump 64 supplying the electrolyte liquid from the source 62 into the buffer tank 66, further connected to the buffer tank 66, to the flow-through regulating valve 68, to the energy cell 70, to the precipitator 72 and to the filter 74. In this embodiment, the control means 76 regulates the operation of these units. The operation of the control means 76 is described below. Furthermore, the figure shows that an electric power handling means 86 is connected to the energy cell 70, and it is responsible for converting the energy obtained from the energy cell 70, so that the obtained energy becomes suitable for feeding into a high voltage mains 88.

In a further embodiment the electric power generating system according to the invention comprises a plurality of energy cells. In this case, to the inlet of each energy cell a buffer tank is connected, and furthermore it comprises flow-through regulating valves regulating the admission of the electrolyte liquid from each buffer tank to the associated energy cell, and each flow-through regulating valve is controlled by a common control means. If multiple energy cells are applied, the energy cells must be insulated from each other.

Fig. 5 shows the operations regulated by the control means. A block 90 of the control means regulates the pump used for filling up the buffer tank, i.e. it regulates the filling up of the buffer tank, its block 92 controls the flow-through regulating valve, and its block 94 monitors the load of the electric power generating system.

Fig. 6 schematically shows the tasks supervised by the block 90. The block 90 checks the filling level of the buffer tank. If the level of the buffer tank does not reach a minimum level, for example a filling level 19' according to Fig. 1 , the pump filling up the buffer tank from the source starts. If the level of the buffer tank is above a filling level 19" shown in Fig. 1 , the pump is idle. With a predetermined periodicity, the block 90 checks the level of the buffer tank. If the pump has already started to fill up the buffer tank to the minimum level, the process proceeds to a block 96, which examines with a predetermined periodicity whether the level of the buffer tank reaches the requested level. In the latter case the control means stops the pump, otherwise the pump is kept in operation. The above described operation of the block 90 of the control means ensures that an appropriate volume of electrolyte liquid is available in the buffer tank. The filling up of the buffer tank can be completed in other ways as well. Replenishing the content of the buffer tank can be continuously carried out in various embodiments for example from an appropriately arranged source, even in gravitational way. In this case, the control means monitors the overflow of the buffer tank only.

On basis of the data received from the block 94, the block 92 controls the passing through by means of the flow-through regulating valve. If the monitored data provided by the block 94 shows, that the energy generated by the energy cell - even when transformed by an energy handling means - is insufficient to meet the needs of electric power consumers or the generated energy is more than needed, this is indicated by the block 94 for the block 92. According to the data monitored, the block 92 sets the flow-through regulating valve to a smaller or larger flow-through than the prevailing condition, to make sure that less or more energy is needed than the energy generated at the prevailing energy generating level, in accordance with the load of the system. The block 94 checks whether as a result of the regulation performed by the block 92 the generated energy has been set to an appropriate level, and if further adjustment is needed, this is indicated for the block 92.

The function of the control means in course of the operation of the system is to coordinate the operation of the components, setting and controlling their operating parameters, performing the appropriate adjustments, in case of necessity providing intervention and performing the necessary steps in case of emergency.

As described above, in certain embodiments of the electric power generating system according to the invention, the system comprises a plurality of energy cells and for each energy cell separate buffer tanks, pumps for filling the buffer tank and flow- through regulating valves. In such embodiments, after having checked and adjusted the filling level of the buffer tanks, the control means controls each pump independently, in order to make sure that the filling level of each buffer tank is appropriate. However, in such embodiments, each flow-through regulating valves are monitored and controlled by a common block, because the energy generated by all of the energy cells must fulfil the needs imposed by consumers using the system. Consequently, in these embodiments the control means regulates the flow-through regulating valves harmonized with the block monitoring the loading of the system. Preferably, the system according to the invention can be a fixed, but also a mobile system. The latter type preferably can be applied especially in the case of environmental catastrophes, when the treatment of wastewater is not solved and an appropriate energy supply is not ensured. In this case, an appropriate dimensioned local energy supply can be provided by means of the system according to the invention.

Some embodiments of the invention relate to a method for generating electric power. In the method according to the invention, the electric power generating system according to the invention is applied, and in course of the method the following steps are cyclically repeated:

- electrolyte liquid is supplied into the buffer tank, and

- by regulating the flow-through regulating valve by the control means the electrolyte liquid in the buffer tank is made to flow through the energy cell.

In course of the method, the buffer tank is preferably filled up from a source by means of a pump. Furthermore in the course of the method, after flowing through the energy cell, the electrolyte liquid is preferably led to the source by letting it through a precipitator and/or filter arranged between the inlet and outlet of a receiving container. In each embodiment of the method, the electrolyte liquid is fed from the outlet of the receiving container to the source by means of a pump.

In course of the method, preferably the potential difference of the electrolyte liquid is measured in the flow path of the electrolyte liquid by means of a potential measuring device and the free ion content of the electrolyte liquid is regulated in accordance with the potential difference of the electrolyte liquid by means of an additive-feeder arranged in the flow path of the electrolyte liquid between the potential measuring device and the inlet of the energy cell.

The invention is, of course, not limited to the preferred embodiments described in details above, but further versions, modifications and developments are possible within the scope of protection defined by the claims.

Claims

1. An electric power generating system, comprising:

an energy cell (26, 58, 70) having an inner space (60), the energy cell (26, 58, 70) comprising

a) an anode (50) and a cathode (48) arranged in the inner space (60) with a spacing suitable for receiving an electrolyte liquid,

b) an inlet (24, 40) leading the electrolyte liquid into the inner space (60) and

c) an outlet (31 , 42) draining the electrolyte liquid from the inner space (60), and the system further comprises

a receiving container (21 , 34) connected to the outlet (31 , 42),

c h a r a c t e r i s e d by comprising

- a buffer tank (18, 66) connected to the inlet (24, 40) and suitable for temporary storage of the electrolyte liquid to be led into the energy cell (26, 58, 70),

- a flow-through regulating valve (22, 68) regulating the admission of the electrolyte liquid from the buffer tank (18, 66) into the energy cell (26, 58, 70) and

- a control means (76) controlling the flow-through regulating valve (22, 68) in accordance with the load of the electric power generating system.

2. A system according to claim 1 , characterised in that in the energy cell (26, 58, 70) a plurality of anodes (50) and for each anode (50) a cathode (48) is arranged.

3. A system according to claim 1 or 2, characterised in that the buffer tank (18, 66) is arranged with respect to the inlet (24, 40) so as to enable a gravitational flow of the electrolyte liquid through the inner space (60) of the energy cell (24, 58, 70).

4. A system according to any of the claims 1 to 3, characterised in that a separator (52) is arranged between the anode (50) and the cathode (48).

5. A system according to claim 4, characterised in that the arranged separator surrounds the anode.

6. A system according to claim 4 or 5, characterised in that the material of the separator (52) is a polyester composite material or a geotextile.

7. A system according to any of the claims 1 to 6, characterised in that the buffer tank (18, 66) is connected to the inlet (24) via a pipe (20), and the flow-through regulating valve (22, 68) is arranged on the pipe (20).

8. A system according to any of the claims 1 to 7, characterised by comprising a source ( 0, 62) connected to the buffer tank (18, 66) and a pump (14, 64) for supplying the electrolyte liquid from the source (10, 62) into the buffer tank (18, 66).

9. A system according to claim 8, characterised in that between the source (10, 62) and the buffer tank (18, 66) a filter is arranged to remove solid contaminants from the electrolyte liquid.

10. A system according to claim 8 or 9, characterised in that the receiving container (21 , 34) comprises an inlet (23, 33) leading the electrolyte liquid into its inner space, and an outlet (29, 35) draining the electrolyte liquid from its inner space, between the inlet (23, 33) and the outlet (29, 35) of the receiving container (21 , 34) a precipitator (25, 72) is arranged for filtering the solid materials from the electrolyte liquid and/or a filter (27, 74) is arranged for filtering the solids from the flowing-through electrolyte liquid, and the outlet (29, 35) of the receiving container (21 , 34) is connected to the source (10, 62) or let out into the environment.

11. A system according to claim 10, characterised in that the outlet (29, 35) of the receiving container (21 , 34) is connected to the source (10, 62) via a pipe (38) and a pump (36) is arranged on the pipe (38) for forwarding the electrolyte liquid from the receiving container (21 , 34) to the source (10, 62).

12. A system according to any of the claims 1 to 11 , characterised in that in the flow path of the electrolyte liquid a potential measuring device is arranged for measuring the potential difference of the electrolyte liquid in its flow path, and between the potential measuring device and the inlet (24, 40) an additive- feeder is arranged for regulating the free ion content of the electrolyte liquid in accordance with the potential difference of the electrolyte liquid.

13. A system according to any of the claims 1 to 12, characterised in that a gas deflector (30, 46) is connected to the inner space (60) of the energy cell (26, 58).

14. A system according to any of the claims 1 to 13, characterised in that the anode (50) contains 91 % to 96% magnesium, 3% to 6% aluminium and 1 % to 3% zinc.

15. A system according to any of the claims 1 to 14, characterised in that the cathode (48) is made of high purity graphite plate.

16. A system according to any of the claims 1 to 14, characterised in that the cathode (48) is made of a nickel-titanium alloy.

17. A system according to any of the claims 1 to 16, characterised in that the electrolyte liquid is seawater or wastewater.

18. A system according to any of the claims 1 to 17, characterised by comprising a plurality of energy cells (26, 58, 70), to the inlet (24, 40) of each energy cell (26, 58, 70) a buffer tank (18, 66) is connected, further it comprises flow- through regulating valves (22, 68) for regulating the admission of the electrolyte liquid from each buffer tank (18, 66) to the associated energy cell (26, 58, 70), and each flow-through regulating valve (22, 68) is controlled by a common control means (76).

19. A system according to any of the claims 1 to 18, characterised in that an electric power handling means (86) transforming the voltage appearing on the electric terminals of the energy cell (70) is connected to the energy cell (70).

20. A method for generating electric power by leading electrolyte liquid through an energy cell (26, 58, 70), c h a r a c t e r i s e d in that the system according to claim 1 is applied in the method, and the method comprises the following steps, cyclically repeated:

- electrolyte liquid is supplied into the buffer tank (18, 66) and

- by regulating the flow-through regulating valve (22, 68) by a control means (76), the electrolyte liquid in the buffer tank (18, 66) is made to flow through the energy cell (26, 58, 70).

21. A method according to claim 20, characterised in that the buffer tank (18, 66) is filled up from a source (10, 62) by means of a pump (14, 64).

22. A method according to claim 21 , characterised in that after flowing through the energy cell (26, 58, 70), the electrolyte liquid is led to the source (10, 62) through a precipitator (25, 72) and/or a filter (27, 74) arranged between an inlet (32, 33) and an outlet (29, 35) of a receiving container (21 , 34).

23. A method according to claim 22, characterised in that the electrolyte liquid is led to the source ( 0, 62) from the outlet (29, 35) of the receiving container (2 , 34) by means of a pump (36).

24. A method according to any of the claims 20 to 23, characterised in that a potential difference of the electrolyte liquid is measured in the flow path of the electrolyte liquid by means of a potential measuring device, and in the flow path of the electrolyte liquid between the potential measuring device and the inlet (24, 40) of the energy cell (26, 58, 70) a free ion content of the electrolyte regulated in accordance with the potential difference of the electrolyte