STORAGE

TECHNICAL FIELD

[001] The present invention relates to systems and methods for energy storage, and more specifically, to systems and methods for using pumped fluid energy storage.

BACKGROUND

[002] There is an increasing need for energy storage solutions in the world. Demand increases due to the need to work with natural renewable energy sources. Natural energy sources cannot be scheduled to provide power at the exact time it is needed as they act randomly by natural forces, such as, for example, wind power, solar power, wave and tidal power and the like. Furthermore increasing demands from base-load power stations along with the need for cleaner and more efficient power production lead to increasing demand for energy storage that enables the producers to reduce load fluctuation and run against constant load thus achieving higher efficiency. There is a general need for inexpensive energy storage for most electrical grids. Pumped-hydro energy storage is one of the least expensive long lasting methods of energy storage presently known. Pumped hydro-storage generally entails releasing water from a higher elevation to a lower elevation when the production of electrical power is desired. The released water may be provided to a turbine generator to generate electricity. Conversely, water are pumped back to the higher elevation when the storage of energy is desired.

[003] Existing pumped-hydro energy storage store water and the accumulated energy depends directly on the stored quantity, i.e., total mass, multiplied by the available height difference between the upper elevation and the lower elevation i.e., the potential energy. Considering the fact that water have relatively low specific gravity of 1000Kg/M ³ (i.e., specific gravity of 9800Nt/M ³ ), it may limit the ability of the users to build the desired storage with sufficient volume to only certain places having enough elevation difference and suitable size of vacant area both at the higher and lower elevations. In most cases in consideration, these locations are basins in high remote mountainous regions which may cause energy losses over long electric transmission lines. Furthermore it may require large scale earth moving and construction to accommodate for a technically and economically justified storage. Such facilities may have severe environmental and social impact. Other disadvantages of water pumped-hydro energy storage may be the limited usability during winter in low temperature areas due to freezing, or constant water replenishment may be needed due to evaporation from large surface area in hot dry areas where water are scarce. Changing water height in the reservoir may result in changing hydrostatic pressure on the turbine generator which may affect the efficiency of the turbine generator in producing electrical power thus may require complicated control systems.

[004] Therefore, it would be advantageous to have a high capacity pumped energy storage system and method that do not have or greatly reduce the one or more shortcomings described above.

SUMMARY

[005] In the present invention, novel systems and methods for pumped energy storage are disclosed using colloidal fluid energy storage. Usage of colloidal fluid as an high capacity energy storage medium provide space saving, efficient and economical way for renewable energy manufacturers and power utilities to store excessive electrical energy that is generated during low demand periods, as well as supplement electricity generation capacity for use during times of peak loads. Accordingly, power utilities may make better use of renewable energy systems and may avoid the financial, social, environmental and cost impacts associated with building larger water pumped storage facilities, expensive toxic chemical batteries, new power plants and support infrastructure.

[006] In various embodiments, a pumped colloidal fluid energy storage system includes at least one accumulation storage reservoir located at high elevation that includes an inlet and an outlet and at least one accumulation storage reservoir located at a lower elevation that includes an inlet and outlet. Some embodiments of the invention include fluidly communicating between storage reservoirs, for example by one or more penstocks fitted with at least one apparatus to convert the down flow of colloidal fluid into mechanical or electrical energy and conveying means to deliver the output power to consumers. Embodiments of the invention also include control units, at least one retune pipe fluidly connecting the high and low accumulating storages fitted with at least one pump to return the colloidal fluid from the lower elevation accumulator to the higher elevation accumulator by using access power from external electric power source during low demand hours of the consumers.

[007] In other embodiments, systems and methods for using pumped colloidal fluid energy comprises, determining the power supply capacity of the power generating apparatus and the load demand of a power users via an energy distribution controller. The systems and methods also include detecting the status of the load demand and changing the power output of the generating apparatus by permitting and controlling the flow rate of colloidal fluid from the higher elevation to the lower elevation or by controlling the specific gravity of the colloidal fluid or by controlling both in conjunction. [008] Furthermore, systems and methods for dynamically increasing and controlling the specific energy capacity (i.e. potential energy density per volume unit) and the total stored energy held by the system in the higher elevation accumulator will be disclosed.

[009] The features, functions, and advantages that have been discussed above or will be discussed below can be achieved independently in various embodiments, or may be combined in yet other embodiments, further details of which can be seen with reference to the following description and drawings.

[0010] For the purpose of the disclosure hereinafter in the descriptions and subsequent claims, wherever "Colloidal fluid" is cited it shall also mean "fluidised particles", meaning finely divided solid particles carried lifted and agitated by a stream of fluid or by virtue of having self- fluidity capabilities or rheological attributes.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Fig. 1 A is a schematic diagram of a pumped colloidal fluid energy storage system with a volumetric flow control and electromechanical apparatus for power generation, in accordance with the embodiments of the invention;

[0012] Fig. IB is a schematic diagram of a pumped colloidal fluid energy storage system with volumetric flow control and hydromagnetic apparatus for power generation, in accordance with embodiments of the invention;

[0013] Fig. 2 is a schematic diagram of a pumped colloidal fluid energy storage with a fluid gravity control in accordance with embodiments of the invention;

[0014] Fig. 3 is a schematic diagram of a pumped colloidal fluid energy storage with fluid gravity control and streams separation in accordance with embodiments of the invention;

[0015] Fig. 4 schematically depicts a system for colloidal fluid energy storage according to embodiments of the present invention;

[0016] Fig. 5 is a schematic illustration of an energy tower in accordance with embodiments of the invention.

[0017] It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements DETAILED DESCRIPTION

[0018] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, modules, units and/or circuits have not been described in detail so as not to obscure the invention.

[0019] Although embodiments of the invention are not limited in this regard, the terms "plurality" and "a plurality" as used herein may include, for example, "multiple" or "two or more". The terms "plurality" or "a plurality" may be used throughout the specification to describe two or more components, devices, elements, units, parameters, or the like. For example, "a plurality of elements" may include two or more elements. Moreover, to simplify the reading and understanding of the disclosures herein wherever the text refer to the components and elements in the singular form it should also be considered as being referred to in the plural form, meaning at least one, unless otherwise specified.

[0020] Systems and methods in accordance with the present disclosure are directed to embodiments of pumped colloidal fluid energy storage. According to embodiments of the invention, energy is accumulated using the high mass density of colloidal fluid to accumulate large amount of potential energy with relatively small occupied volume. Energy accumulation is formed by elevating the colloidal fluid to a high elevation and releasing it through power generating apparatus to a lower elevation.

[0021] In some embodiments of the present invention the colloidal fluid may comprise of, but not limited to, a carrier base fluid, particles of heavy specific gravity materials and surfactant material to form a uniformly dispersion of particles fluid topology and prevent sinking of the heavy particles in the colloidal fluid. Such colloidal fluids are well known in the art and differ from each other by their composition.

[0022] By way of example, colloidal fluid may include kerosene as the base fluid, nanoparticles of magnetite as the heavy particles and oleic acid as the surfactant material mixed in a chemical process. An exemplary colloidal fluid having 80% Kerosene, 15% magnetite particles and 5% Oleic acid may have specific gravity of 1450 Kg/M ³ , which is 75% heavier than the original base fluid. Such an exemplary fluid may allow the system the capability to store 75% more potential energy per volume unit than a system with original base fluid only. Another exemplary, water based colloidal fluid may comprise of 68% water with 25% magnetite particles and 7% surfactant. Such a fluid may have specific gravity of 1990 Kg/M ³ which is 99% heavier than the original water, thus giving such a system the capability to store 99% more potential energy per volume unit. [0023] According to embodiment of the invention, colloidal fluid may be based on any known fluid, such as but not limited to, water, seawater, hydrocarbons, polymer fluids, natural oils, resins, air and gases or any combination thereof. The heavy particles may be of any size, such as but not limited to, single molecules, nanoparticles, micro-size particles, macro size particles or any combination thereof. For example, a typical colloidal fluid may have particles with sizes ranging from 3 to 15 microns. The heavy particles may be made from any of the chemical elements or their compositions thereof. For example, the particles may be made of materials that may be readily found in nature which have advantages such as price and environmental friendliness. Exemplary materials may include, for example, Hematite, Magnetite, Ilmenite and other Ferrite-oxides that are in abundance and suitable for the described embodiments. Other heavy elements and compounds such as but not limited to cooper, brass, bronze, Lead, Tungsten, Tungsten-carbide, Manganese, Chrome, Cobalt and nickel may be used with some advantages due to their high specific gravity and metallic attributes. None-metallic materials such as but not limited to Flint rock, Silica, Basalt, glass, concrete and Quartz may show some advantages in cost and low environmental impact. All of the above mentioned materials or their mixture may be used in certain embodiments of the invention as homogeneous or none homogeneous mixture of particles.

[0024] In addition to space saving attribute the use of colloidal fluid have farther advantages over systems which uses fluids with relatively low specific gravity. It may enable reduction of the required size of both the turbine or fluid motor provided to turn the generator and the pump provided to pump the fluid back to the higher elevation. While the power associated with said apparatuses relate directly to the fluid's specific gravity, their size relate directly to the specific volume. Usage of high specific gravity fluid and bearing in mind that specific volume being the inverse of specific gravity result in smaller operating volume for all apparatuses and communicating conduits. Thus cause savings in infrastructure expenditures, apparatuses cost, installation cost, spare parts cost, ease of maintenance and smaller environmental impact. Farther advantage is the ability to formulate a high specific gravity fluid in accordance with specific conditions, such as but not limited to, subzero temperatures that otherwise prevent the use of water, high temperatures in sun exposed areas that increase water evaporation, flow velocity in the penstock and the ability to plan a working point versus cost to meet any user's needs.

[0025] Colloidal fluids by nature may have one or more limitations, e.g., limitation regarding the proportions between the ingredients comprising the fluid. For example, limitations may arise from the nature and attributes of each of the materials, from the way the fluid is formed and from the combined attributes of the mixture. The quantity of heavy particles in the fluid that arises from such limitations may also set an upper limit on the specific gravity of the fluid and thus on its capability to accumulate potential energy. The minimum achievable specific gravity of colloidal fluid may be the specific gravity of the base fluid when the quantity of particles is set to zero. The maximum achievable specific gravity of colloidal fluid may be the sum of each of the fluid's component volume multiplied by its own specific gravity and all divided by the total volume of the fluid. The maximum specific gravity is lower than the specific gravity of the particles themselves and the difference between specific gravity of the colloidal fluid and specific gravity of the particles represents loss of storage energy potential in a given volume and loss of volumetric efficiency. Loss of energy may increase the space occupied by the storage system and may reduce economic viability. Embodiments of the invention may improve the energy storage capacity for a given volume as described herein.

[0026] Reference is made to Fig. 1A, which is a schematic diagram of a pumped colloidal fluid energy storage system with a volumetric flow control and electromechanical apparatus for power generation, in accordance with the embodiments of the invention. A pumped colloidal fluid energy storage system 100, having effective potential energy height H _e f. H _e f being the height difference between center of gravity of stored colloidal fluid 102 and an energy converting apparatus 112 and represents the energy that may be extracted from the system. The system may include a first storage reservoir 101 at a first elevation HI having an inlet and an outlet and a second storage reservoir 103 at a second elevation H2 having an inlet and an outlet. The first elevation HI is higher from elevation H2. The difference between HI and H2 defines the energy input into the system that is used by the pump to raise the fluid. The aforementioned difference should be as close as possible to H _e f in order to minimize losses. At a certain point in time, for example, at a beginning of a power generating or production cycle, referred to herein as a "starting point", reservoir 101 include colloidal fluid 102 while reservoir 103 may be empty. The converting apparatus 112, referred also herein as "a power generating apparatus" may be used for converting fluid flow energy into another form of energy and may be connected between the first storage reservoir 101 and the second storage reservoir 103 and may be located lower than the first elevation HI . Colloidal fluid 102 may include base fluid, surfactant and solid particles with specific gravity higher than that of the base fluid.

[0027] System 100 may include a control center 104 which may control power distribution of system 100 and may be connected via general electric grid 105 to one or more external power elements such as an aggregate of power consumers and manufacturers 106, renewable power sources 107, and the like. At the start of the power generating cycle, control center 104 may get a demand request for power from the external electric grid 105 or receive an indication of power provided by the external power sources. System 100 may further include a controlling computer 110 having dedicated software which may be connected via control lines 109 to control center 104. Control center 104 may signal a main valve 108 via control lines 109 and controlling computer 110, to open and allow colloidal fluid 102 to flow through a penstock 111 to feed a power generating apparatus 112. Penstock 111 may allow fluid transfer connecting between the first storage reservoir 101, the converting apparatus 112 and the second storage reservoir 103. Valve 108 may be located on penstock 111 and may control the colloidal fluid flow from the first storage reservoir 101 via the converting apparatus 112 to the second storage reservoir 103. Power generating apparatus 112 may be any kind of fluid turbine, engine or motor which may produce electrical, mechanical or thermal power. Power generating apparatus 112 may include, for example, a turbine that may be coupled to an electrical generator 113 that produces electrical power and convey it via power lines 114 to control center 104. Control center 104 may control power export to grid 105 and control transfer of the energy converted by converting apparatus 112 to external grid 105. Exhausted fluid may leave power generating apparatus 112 to fill reservoir 103.

[001] According to embodiments of the invention, control center 104 may regulate the flow of colloidal fluid 102 by controlling main valve 108. Control center 104 may compare between the external demanded power or the certain amount of power requested from grid 105 and output power generated by generator 113 or between the external incoming excess power from grid 105 and the energy storage reservoir loading progress, interchangeably. Control center 104 may further monitor fluid levels in the reservoirs, flow rate in the pipes and pressures against power input or against power output and regulate the valves, turbine, pump and other devices accordingly.

[002] When the net power in grid 105, i.e. power consumed by users, is less than the net power produced by all external power producers and renewable energy sources 107, it is an excess power. It is directed by the power distribution and control center 104 via power lines 115 to drive pump 116, to pump the colloidal fluid 102 from reservoir 103 to reservoir 102 through return pipe 117 to be stored until a next power production cycle is started. Control center 104 may receive indication of power provided by an external power source 107 and may control the flow of the received power.

[003] Pipe 117 may be used for fluid transfer connecting between an outlet of the second storage reservoir 103, the pump 1 16 and an inlet of first storage reservoir 101. System 100 may store energy by pumping colloidal fluid 102 into first storage reservoir 101, to release stored energy by releasing colloidal fluid 102 to flow down from first storage reservoir 101 via converting apparatus 112 to produce power and to second storage reservoir 103, and to control the total released energy by adjusting the flow volume and density of the colloidal fluid released from first storage reservoir 101. [004] According to embodiments of the invention, system 100 may include one or more sensors to enhance system controllability by sensing, measuring or detecting one or more parameter related to system 100. For example, sensors may include, but not limited to, upper reservoir level sensor 118 to measure the level, amount or height of fluid 102 inside reservoir 101, lower reservoir level sensor 119 to measure the level, amount or height of fluid 102 inside reservoir 103 flow sensor 120 to measure parameters of the flow in penstock 111 and flow sensor 121 to measure parameters of flow in return pipe 117, pressure sensors 122, 123 to measure parameters of pressure in penstock 111 and return pipe 117, respectively, and power meter 124 to measure the power generated by electrical generator 113. All sensors may be connected to or coupled to controlling computer 110 and may transfer, deliver or transmit the detected parameters related to the state of system 100 to the controlling computer 110. All sensors may detect one or more parameters for enhancing controllability of the control center 104. Other sensors for other parameters required for controlling system 100 may be included in system 100.

[005] It should be clear to a person skilled in the art that system 100 may include other elements that may perform the functionality of the represented elements, for example, in some embodiments of the invention turbine 112, generator 113 and pump 116, may be replaced by a single dual-mode apparatus that may function alternately as either a turbine-generator or a motor-pump. In such embodiments return pipe 117 may be omitted. In some embodiments controlling computer 110 may be coupled to control center 104 while in other embodiments controlling computer 110 may be included in control center 104. Other example of different elements that may be used in embodiments of the invention may include any kind of turbines and pumps, e.g., turbine 112 and pump 116 may be constant speed type or the variable speed type.

[006] Reference is made now to Fig. IB which is a schematic diagram of a pumped colloidal fluid energy storage system with volumetric flow control and hydromagnetic apparatus for power generation, in accordance with embodiments of the invention. System 100B shown in Fig. IB is similar to system 100 described in Fig. 1A with the exception of having the power produced by utilizing a colloidal fluid 102 comprising magnetic, ferromagnetic or paramagnetic particles, or a mixture thereof, flowing through penstock 111 and coils 125 to produce electricity by way of hydromagnetic induction.

[007] Reference is made to Fig. 2 which is a schematic diagram of pumped colloidal fluid energy storage with a fluid gravity control in accordance with embodiments of the invention. Embodiments of the invention which are described in details below may enable getting closer to a theoretical maximum potential energy that may be stored by the particles of a given colloidal fluid, which may comprise of only the particles themselves and the attached surfactant without base fluid. According to embodiments of the invention, a colloidal fluid energy storage system 200 may have maximum energy storage capabilities in a given volume of an upper reservoir and may reduce overall system size and cost per-unit of stored energy. Furthermore, embodiments of the invention include methods for dynamically controlling the specific gravity of the colloidal fluid at any given moment in order to achieve maximum efficiency of the power generating apparatus and pump.

[008] A pumped colloidal fluid energy storage system 200 may include a first elevation reservoir 201 at a first elevation HI having an inlet and an outlet. A volume 202 of reservoir 201 may be sufficient to accumulate all the heavy particles given in the system, covered with surfactant, and some minimal quantity of base fluid. Shown here in the fully loaded state. Reservoir 201 may include or may be coupled to a mixing device 203. Mixing device 203 may agitate, stir or mix the colloidal fluid to assist the flow of the fluid. Reservoir 201 may include or may be coupled to a variable adjustable separation device 204 which may be located at reservoir's 201 outlet and may enable separating the surfactant coated particles from the base fluid to achieve variable mixture, i.e., variable fluid density, in a continues none-destructive way by using, for example, variable filter, cyclone, magnetic field separator, centrifuge and the like. Any other device or method may be used in order to allow separation of surfactant coated particles from the base fluid.

[009] System 200 may include a second reservoir 205 located at a second elevation H2 lower from elevation HI . Reservoir 205 may include an inlet and an outlet and a sufficient volume to accumulate all the fluids and particles in the system. At an initial loaded state, reservoir 205 may be provided with some quantity of particles free base fluid occupying a volume 206 which is preferably smaller than the maximal volume of reservoir 205. Reservoir 205 may include or may be coupled to a mixing apparatus 207 for agitating the fluid.

[0010] A penstock 208 having a main valve 209 is used to convey the colloidal fluid flow from the upper separation device 204 to a turbine 210 which turns a generator 211 to produce, for example, electrical power. Other fluid motors or hydromagnetic induction apparatus may be utilized. The power generated by generator 211 may be conveyed to a distribution and control center 216 via power lines 217 and from there to the external grid 218. Distribution and control center 216 may include one or more computers having dedicated software to perform comparison between the external demanded for power, received from grid 218 and the output power generated by generator 211 or between the external incoming net excess power received from external power grid 218 and the energy storage progress of system 200, interchangeably and monitoring fluid levels in the reservoirs, flow rate in the pipes and pressures against power input or against power output and regulate the valves, turbine, pump and other devices accordingly. [0011] During power production the exhausted fluid is discharged from turbine 210 to a lower elevation reservoir 205. Also provided at the lower elevation H2 at reservoir's 205 outlet is a separation device 212 capable of separating the surfactant coated particles from the base fluid to achieve variable per-demand mixture, i.e., variable fluid density, in a continues none-destructive way, by using, for example, variable filter, cyclone, magnetic field separator, centrifuge and the like. A pump 213 is provided at the lower elevation H2 to restore fluid to the upper elevation reservoir 201. At times when the grid's 218 net power i.e. power produced by renewable energy sources 215 and all external power producers less power consumed by users 214 or is an excess power, it is directed by the power distribution and control center 216 via power lines 219 to drive pump 213 that pumps fluid from the lower elevation H2 to the upper elevation HI through return pipe 220.

[0012] The system is further provided with a control computer 221 having dedicated software, which controls the operation of all apparatuses in the system by receiving input and acting on instructions to store or discharge required amount of energy given by the distribution and control center 216 and by analyzing input signals from sensors such as but not limited to, pressure sensor 222, flow meter 223, densitometer 224, return pipe flow meter 225 upper reservoir level sensor 226, lower reservoir level sensor 227, return pressure sensor 228 and power meter 229, processing said information and adjusting the operational apparatuses operation accordingly.

[0013] Colloidal fluids may have a limiting saturation value of particles quantity within the base fluid which result in loss of potential energy storage capacity within a given storage volume. In order to maximize the accumulated mass of heavy particles at the higher elevation reservoir 201, embodiment of the invention may include separation and remixing of the base fluid and surfactant coated particles at certain stages of the work cycle.

[0014] Prior to first start and commissioning of system 200 operation it may be loaded by providing saturated colloidal fluid that will be pumped to fill upper reservoir 201 to its the maximum capacity 202 and the remaining saturated colloidal fluid will be provided at the lower reservoir 205 occupying volume 206. Subsequently opening valve 209 and operating the upper separator 204 regulated to keep the particles locked in the upper reservoir 201 allowing only the base fluid to flow down penstock 208 and operate turbine 210 to produce power which may be diverted to grid 218 or used within system 200. The base fluid which may have some residual particles will reach lower reservoir 205 and dilute the fluid which is already there.

[0015] Concurrently lower separator 212 may be left open for restriction free flow and pump 213 activated to pump the diluted fluid to the upper level reservoir. System loading stage will continue until all the heavy particles will accumulate in the upper reservoir with some base fluid 202, ready for immediate release and power generation. The remaining base fluid 206 which may have some residual particles will be in the lower reservoir. All apparatuses will be then stopped and valve 209 closed. The system is ready for power production. Such configuration may have the maximum high specific gravity mass stored in the defined volume of the upper reservoir and thus have the maximum possible stored potential energy. The base fluid may be used as conveying medium; therefore it may circulate in system 200 from upper reservoir 201 to lower reservoir 205 and back more times than the particles.

[0016] According to embodiments of the invention, the stage performed prior to energy production stage, may be performed once before initialization of system 200 and may include providing upper reservoir 201 with as much particles as technically possible. It should be clear to a person skilled in the art that the process of loading upper reservoir 201 to its the maximum capacity 202 with saturated colloidal fluid may be performed in any way, process or method, for example, by providing saturated colloidal fluid to reservoir 205 and pumping it up to reservoir 201 as described herein, by providing saturated colloidal fluid directly to upper reservoir 201 by external means such as trucks or the like. At times of power demand by consumers or users 214 of the external grid 218, directed by the power distribution and control center 216 the control computer 221 may open valve 209 and adjust upper separator 204 to allow flow of colloidal fluid having adequate proportion of base fluid and particles, i.e., releasing fluid with specific gravity suitable to create the requested power. It flows through penstock 208 to turn the power generating turbine 210 and generator 211 to produce power which will be sent to the grid 218. Concurrently and continuously, pump 213 will be operated to pump only base fluid, separated by separator 212, to the upper reservoir 201 and enable continues mixing the fluid and particles at reservoir 201 by mixing device 203 and flow from the upper reservoir. Controlling of power production rate according to changing demand can be done by dynamically adjusting the volume of particles mixed with the base fluid from zero to the saturation value in separator 204. Further control may be provided by controlling valve 209 that may be proportionally adjusted to regulate the flow volume that may reach turbine 210 in order to allow a specific amount of power production.

[0017] During power production phase, operating pump 213 may require power, however, the actual power loss of system 200 according to embodiments of the invention may be only due to the electromechanical efficiency of system 200. As it is the difference between the energy generated by base liquid mass while flowing down penstock 208 and operating turbine 210 and generator 211 on one side and the energy required to pump up fluid by pump 213 on the other side. For example, the efficiency of such pumped hydro systems commonly may be around eighty percent; the energy lost is only twenty percent of the base fluid mass flow. Bearing in mind that the particles have much greater specific gravity then the base fluid which typically may range from three to fifteen times heavier, the total energy capacity may be significantly higher than by storing saturated colloidal fluid and using it to produce power without controlling the amount of particles in the fluid. Other embodiments of the invention may achieve further reduction in wasted energy by using base fluids having low specific gravity such as but not limited to, oils, hydrocarbon derivatives, compressed air or gas and gels.

[0018] It will be appreciated that great advantages arise from controlling the flow of energy by controlling the density of the fluid and not by controlling the volumetric flow. It may greatly simplify the structure and control of both the turbine and the pump and reduce problems created by cavitation and other variable volume flow related phenomena. Thus may further simplify and reduce their construction, maintenance and associated cost.

[0019] It will be also appreciated that a system that gives the operator the choice of controlling power production either by specific mass control and or by volume control further enhances the system range of operational states in conjunction with the fast changing power demands and transients typical to the external power grid.

[0020] Reference is made to Fig. 3 which is a schematic diagram of pumped colloidal fluid energy storage with fluid gravity control and streams separation in accordance with embodiments of the invention. A system 300 may include a first elevation reservoir 301 at elevation HI having an inlet and an outlet and having a volume 302 sufficient to accumulate all the slurry of heavy particles covered with surfactant in the system. Although embodiments of the invention are not limited in this regard, the term "slurry" as used herein may include particles which are condensed such as it behaves like mud, slurry or a wet pile of grains. Shown here full, it is referred to a fully loaded state of system 300. Reservoir 301 may include a mixing apparatus 303 for agitating the slurry and a variable adjustable dosing apparatus 304 located at an exit of reservoir 301 coupled to or connected the outlet of reservoir 301. Dosing apparatus 304 may be capable of dosing surfactant coated particles into base fluid stream flowing in a collecting pipe 305, to achieve variable per-demand mixture, i.e., variable fluid density, in a continues way. Dosing apparatus 304 may be, but not limited to, variable speed rotating valve, pump, cyclone, magnetic field valve and the like.

[0021] According to embodiments of the invention system 300 may include, at the higher elevation HI, a variable adjustable separation device 306 capable of separating the surfactant coated particles slurry from the base fluid in a continues none-destructive way, such as but not limited to, variable filter, cyclone, magnetic field separator, centrifuge and the like. System 300 may further include a base fluid compensation reservoir 307 located at higher elevation HI adjacent to reservoir 301, having an inlet and an outlet Compensation reservoir 307 may receive flow of particles-free base fluid and discharge it through valve 309 to collecting pipe 305. Monitoring the flow rate in pipe 305 is flow metering device 310. The compensation reservoir's storage volume 308 is designed to compensate for start, stop, thermal and transient effects which due to latency in reaction times of some of the system's components may be subject to volumetric flow discrepancies between unit 306 output and pipe 305 throughput. In addition when system 300 stops reservoir's storage volume 308 may maintain sufficient fluid for next cycle's start.

[0022] The mixed colloidal fluid coming out of collecting pipe 305 may flow down through a main valve 321 and penstock 322 to turn turbine 323 and its generator 324. Fluid motor or hydromagnetic induction apparatus can also alternatively be utilized. The produced power is conveyed by electrical conduits 325 to the main power distribution and control unit 326 and diverted to the external grid 327 or to operate pump 331. The power distribution and control unit 326 using computers having dedicated software, perform comparison between the external demanded power and output power from generator 324 or between the external incoming excess power and the energy storage progress, interchangeably and monitoring fluid levels in the reservoirs, flow rate in the pipes and pressures against power input or against power output and regulate the valves, turbine, pump and other devices accordingly. The exhausted fluid is discharged to a separator 316 at a second elevation H2.

[0023] At the lower elevation H2 provided are reservoir 31 1 having an inlet and an outlet and having sufficient volume 312 to accumulate slurry of all the heavy particles covered with surfactant in the system. Shown here empty as the system is in the fully loaded ready state. A mixing apparatus 313 for agitating the slurry may be connected to or include in reservoir 311. Also provided at the exit of reservoir 311 is a variable adjustable dosing apparatus 314 capable of dosing the surfactant coated particles into the base fluid stream flowing in pipe 315, to achieve variable per-demand mixture, i.e., variable fluid density, in a continues way. Said dosing apparatus may be but not limited to, variable speed rotating valve, pump, cyclone, magnetic field valve and the like.

[0024] Also provided at elevation H2 is a variable adjustable separation device 316 capable of separating the surfactant coated particles slurry from the base fluid in a continues none- destructive way, such as but not limited to, variable filter, cyclone, magnetic field separator, centrifuge and the like. A base fluid compensation reservoir 317 located at elevation H2 may be located adjacent to reservoir 311. Compensation reservoir 317 may include an inlet and an outlet and may receive flow of particles-free base fluid and may discharge it through valve 319 to pipe 315. Monitoring the flow rate in pipe 315 may be performed by a flow metering device 320. The reservoir's storage volume 318 is designed to compensate for start, stop, thermal and transients effects which due to latency in reaction times of some of the system's components may be subject to volumetric flow discrepancies between unit 306 output and pipe 305 throughput. In addition when system 300 stops reservoir's storage volume 308 may maintain sufficient fluid for next cycle's start.

[0025] At times when grid 327 net power produced by all external power producers 328 or renewable energy sources 329 is an excess power, it is directed by the power distribution and control center 326 via power lines 330 to drive pump 331 that pumps fluid from the lower elevation H2 to the upper elevation HI through return pipe 332. System 300 is further provided with control computer 333 having dedicated software, which controls the operation of all apparatuses in the system by receiving and acting according to instructions to store or discharge a required amount of energy, given by the distribution and control center 326 and by analyzing signals from sensors such as but not limited to, pressure sensors 334, 342, flow meters 310, 320, 335, 337, densitometer 336, upper elevation reservoirs level sensors 338 and 339, lower elevation reservoirs level sensors 340 and 341, and power meter 342, processing said information with a dedicated software and activating the operational apparatuses accordingly.

[0026] In order to maximize mass accumulation of heavy particles at the higher elevation HI, Embodiments of the invention may include separation and remixing of base fluid and surfactant coated particles at certain stages of the work cycle. A stream of base fluid is circulating continuously in system 300 and the heavy surfactant coated particles may be added to it, or removed from it, in predetermined stages of the work cycle. According to the present method, when the system is required to produce energy, valves 309 and 321 are proportionally opened, according to command calculated by computer 333, and base fluid is released to the collecting pipe 305, from there through penstock 322 to turbine 323 which starts rotating and turn the generator 324 to produce electricity.

[0027] Concurrently and continuously valve 319 is opened and pump 331 is operated by external power from grid 327 or by internal power from the generator. It pumps particles free base fluid to the higher elevation HI in order to sustain constant flow in the loop formed by compensation reservoir 307, collecting pipe 305, penstock 322, lower separator 316, lower compensation reservoir 317, pipe 315, pump 331, return pipe 332 and upper separator 306. After the flow has been stabilized and all transient effects have subside, dosing device 304 starts to release measured quantity of heavy particles slurry into the base fluid stream to create colloidal fluid with the desired specific gravity as calculated by control computer 333. The colloidal fluid than flow down penstock 322 and turn turbine 323 to produce the correct amount of power. The exhausted fluid enters the lower separation device 316 that separates the particles slurry into reservoir 311, wherein it will remain until the start of the next energy storage cycle and the base fluid into the lower compensation reservoir 317, from which it continues its journey through the aforementioned loop.

[0028] Some embodiments of the invention may allow very fast control and may start dosing the particles into the base fluid immediately upon starting operation of the system, i.e., without waiting for stabilized flow, in order to achieve very fast ramp-up time of the power production.

[0029] In the beginning of the energy storage phase, some or all of the heavy particles slurry reside in the lower elevation reservoir 317 and needs to be pumped back to the higher elevation HI for storage. The circulation loop of base fluid may be started and the lower dosing device 314 may start to release the particles slurry from reservoir 31 1 into the stream in pipe 315. The dosing is measured to create colloidal mixture with the maximal possible quantify of particles in the base fluid, up to its saturation point according to its attributes. The colloidal fluid is pumped by pump 331 through return pipe 332 to the higher elevation separator 306 that separates the particles slurry into reservoir 301, wherein it will remain stored until the start of the next power production cycle. The base fluid flow into the higher compensation reservoir 307, from which it continues its journey through the aforementioned flow loop.

[0030] Other embodiments of the invention may include mounting the turbine, the generator and the pump on a common single shaft in order to achieve minimum loss of efficiency, smaller footprint and simplification of the apparatuses may be advantageous as they all work simultaneously. It may reduce facility size, initial cost and operational cost.

[0031] In other embodiments of the invention pump 331 may be coupled mechanically or electrically directly, for example, not through grid 327, and/or not through control unit 326, to a renewable source energy provider like, wind turbine, solar power, or wave and tidal power, in order to reduce the number of components and save cost. It will eliminate the need for devices to bring the power output of the renewable source to the standards used in the external grid and will be able to operate directly under the varied conditions often associated with renewable sources output.

[0032] In yet another variation, the system may function as both energy storage and city water tower. By using fresh water as the base fluid and nonhazardous surfactant and particles. Further adding inlet and filtered outlet to the upper compensation reservoir externally connected by pipes to the city water system. It will function normally as any regular water tower.

[0033] Many locations that might need energy storage don't have enough high elevation places with big enough area to construct the required upper elevation storage reservoir. However, there may be an assortment of high places relatively close to each other with different high elevation and with available spaces that if combined together will have the required capacity for the energy storage facility. For example area of several high-rise buildings with different heights, group of hills or mountains with narrow summits or industrial complex with structures of different elevations etc.

[0034] Reference is made to Fig. 4 which schematically depicts a system for colloidal fluid energy storage according to embodiments of the present invention. System 400 may comprise a plurality of higher elevation storage reservoirs 401, 402, 403 wherein the components may be as described for upper elevations HI in reference to Fig. 1A or Fig. 2 or Fig. 3, and a centralized facility 422 at the lower elevation where power production and controls may be located as described for lower elevations H2 in reference to Fig. 1A or Fig. 2 or Fig. 3 (all shown here schematically for simplification). Each elevation may have its effective working height Hefl, Hef2, Hef3 that determines the energy potential stored therein. Each of the storage locations may be connected by a feeding penstock 404, 405, 406 to a main penstock 407 that leads the colloidal fluid stream to the inlet of turbine 408 which is coupled to a power generator 409.

[0035] In the exemplary illustration of Fig. 4, for simplicity, only 3 feeding penstock are illustrated, however, it should be understood to a person skilled in the art that the number of feeding penstock may be any suitable number of penstocks, In some embodiments of the invention main penstock 407 may be omitted and each individual feeding penstock may be connected directly to an inlet of turbine 408. A combination of the two variations may also be used.

[0036] The exhausted fluid from turbine 408 may flow to the lower elevation reservoir facility 410 that may contain all the lower elevation equipment as previously disclosed in embodiments hereinabove (not shown in the drawing for simplification). Further provided at the lower elevation is pump 411 that may pump the fluid from lower reservoir 410 back to each upper elevation reservoirs' locations through a main return pipe 412 and diverting valves 413 connected to each of the individual return pipes 414, 415, 416 which are connected to storage reservoirs 401, 402 and 403 respectively. System 400 may comprise a controlling computer 417 running dedicated control management software based on inputs from plurality of control sensors (not shown in the schema for simplification). Also provided is a power distribution and control center 418 connected to the main power grid 419 which connects aggregate of power producers and users 420 including producers of renewable energy 421.

[0037] In the exemplary illustration of Fig. 4, for simplicity, only 3 storage reservoirs are illustrated, however, it should be understood to a person skilled in the art that the number of storage reservoirs may be any suitable number of reservoirs. It should also be understood to a person skilled in the art that the arrangement of storage reservoirs illustrated in Fig. 4 is an exemplary arrangement and any arrangement may be applied, for example, all the reservoirs may be stacked one above the other in a column arrangement. [0038] It is clearly apparent from the embodiments and variations previously disclosed hereinabove that by controlling the specific gravity of the fluid, a single common lower elevation turbine-generator, storage, and pump, may be used without suffering from the operational difficulties associated with operating under different pressures and flow conditions, often associated with common water based pumped hydro systems, that may require expensive equipment and complicated controls. Therefor it is an additional fundamental advantage of the new invention.

[0039] It should be noted that that all or part of the embodiments and variations previously disclosed hereinabove can also be implemented having all its components completely underwater or underground or having it partially underwater or underground. For example having its lower elevation equipment under sea or in a deep mine and keeping the upper storage and its associated devices in an above the surface reservoir structure. In further variation the system may be implemented as above ground standalone towers.

[0040] Reference is made to Fig. 5 which is a schematic illustration of an energy tower in accordance with embodiments of the invention. A multi-functions tower 500 may comprise of a colloidal fluid energy storage system having an upper elevation reservoir 501 having inside its associated apparatuses as described with reference to embodiments of the invention (not shown in the drawing), lower elevation reservoir 502 having inside its associated apparatuses as described with reference to embodiments of the invention (not shown in the drawing) and a supporting structure 503 having sufficient height for accumulation of the required potential energy. Although lower reservoir 502 is shown in the exemplary illustration of Fig. 5 as located below the sea or a ground surface 509, the embodiment is not limited to such placement, and the lower reservoir 502 may be constructed in any surroundings and any position.

[0041] A wind turbine 504 and a solar power device 505 may be mounted externally on tower 500. Solar power devices 505 may be mounted pivotally, to enable both pitch 506 and yaw 507 movements to follow the sun and provide maximum power. The generated power is transferred to the users via a power grid 510.

[0042] In most cases the wind power, solar power and base-load peak power cannot be synchronized with the power demand and may not be easily controlled to achieve maximum efficiency due to unpredictability of the availability of the natural forces. For example, due to its changes according to seasons, changing demand over time etc. By introducing this new integrated arrangement of tower 500, excess power from the different sources may be stored directly at all times and may be distributed at time of demand without complicating the controls or loosing unused power. Further savings on construction cost may be achieved by using the output of the solar power and wind turbine directly to drive the fluid loading pump without converting it first to grid standard voltage or frequency. Another advantage arise from the use of the tall structure of tower 500 to install the solar power system vertically which may save a lot of valuable ground area.

[0043] While the invention has been described with reference to preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will also include all embodiments falling within the scope of the appended claims.