Abstract:
In a method for converting fluctuating energy into a stable energy supply, the fluctuating energy is derived from the group of solar energy, wind power, waves or water currents, this energy being delivered to a first pump being integrated in a pressure circuit for delivering stable energy and the pressure circuit comprising a pressure amplifier with a double-cone device being driven by the liquid flow circulated by the first pump. This allows the stabilization of fluctuating energy to be used e.g. in desalination plants without supplemental storage energy and without reverting to electric current conversion.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention refers to a method for converting a fluctuating and/or erratic energy supply into a stable energy source, according to the introduction of claim  1 . 
     2. Discussion of Related Art 
     Many renewable energy sources manifest both a fluctuating and an erratic energy output. In particular, solar energy, wind power, waves and water currents are dependent both on largely unpredictable climatic conditions and on predictable temporal cycles. The net result is generally a semi-unreliable power Output that does not facilitate and favour its use for many simple applications. In fact, the growth of wind turbine farms is currently limited by the fact that there is an upper limit of some 20% for their power contribution to conventional electrical grids. Beyond this value the grids become seriously disrupted. 
     SUMMARY OF THE INVENTION 
     Departing from this prior art, it is an object of the present invention to propose a method of energy storage without the need for electrical conversion. 
     This object is attained by means of the method of claim  1 . Further advantages and preferred embodiments are defined in the dependent claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be explained in more detail hereinafter with reference to the flow diagram drawings of exemplary embodiments. 
         FIG. 1  shows a first embodiment of a low-pressure liquid feed converter into a high-pressure supply, 
         FIG. 2  shows the converter of  FIG. 1  for a high-pressure compressed air supply, 
         FIG. 3  shows the converter of  FIG. 2  in a sweet water storage filling mode, 
         FIG. 4  shows the converter of  FIG. 2  in a sweet water production mode, and 
         FIG. 5  shows a variation of the converter of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     As mentioned in the introduction, the subject of this invention is the conversion of the erratic and variable energy output of typical renewable energy sources into a stable controllable power supply. According to the invention this can be achieved without the requirement of passing by the electricity production stage (voltaic cells excluded). In all cases the converting and stabilising of any electrical outputs is avoided. Once stable and controllable, the energy may be dosed in a continuous manner so as to permit the economic use of standard equipment. The conversion technique also lends itself to the direct pumping of liquids, gases and the purification of contaminated water. 
     In general, there exist a number of solutions for converting renewable energy sources such as wind, solar, waves and water currents into electrical and/or mechanical outputs. According to the flow diagram of  FIG. 1 , this power is supplied to an unsophisticated circulation pump. This pump is integrated into a pressure circuit that includes a pressure amplifier, which comprises components which are known under the name of DCT (Double-cone Technology) and described inter alia in WO-A-2004/113733 and WO-A-2001/16493, both to the applicant of the present patent. Both applications are, insofar as the double-cone technology, resp. pressure amplifier, is concerned, incorporated as part of the present disclosure. Hereinafter, some examples of methods for storing energy are given. 
     Generally, a double-cone device (DCD) or DCT pressure amplifier comprises two frustroconical sections interconnected by their narrow ends to create an orifice. The entry section provides the entry for the working fluid, the exit section the exit for the mixture of working fluid and sucked-in fluid. At the orifice or in the exit cone, a gap and/or permeable zone constitute the inlet for fluid to be sucked-in. More specifically, conicities of the conical sections, width of orifice etc. are to comply with conditions laid down in the above-mentioned publications in order that a DCD in the strict sense is present. 
     Water Storage 
     Circulation pump  1  is integrated into a pressure circuit  2  and starts up under low load. Fresh or contaminated water, for example salt-water, is fed at low pressure into the pressure circuit through a pressure amplifier  3  comprising the above-mentioned double-cone with an entry cone  4 , an exit cone  5  and a gap chamber with entrance  6 . The energy for it is taken from the flow of liquid (arrows  51 ). This results in three different pressures P 3 , Pi, P 2  as a function of the pumping power available from the circulation pump  1 , whereby P a &lt;P 2 &lt;Pi. 
     The circulation pump  1  can be driven by various unstable energy supplies such as wind, sun, water current or waves. Progressively, the circuit pressure builds up without substantially increasing the power requirement of the circulation pump. The water is stored in an elevated storage site  7  and, once the pressure attains a sufficient level, the water is metered out at high pressure through a nonreturn valve  8  and a pressure regulation valve  9 . The pressure P h  is much higher than that of the circulation pump delivery pressure (P 1 -P 2 ) ● As the power input fluctuates, the circuit pressure automatically rises or falls. With a pressure fall, the non-return valves  8  and  10  at the entry shut off the inlet and outlet to the circuit so that the residual circuit pressure is not lost. 
     Normally, on closing the inlet and/or outlet to a pump the action leads to very rapid pump breakdown. In the present circuit, no such situation occurs and all functions remain in a totally safe manner. For the case of surge in the power supply, a larger output is achieved and under extreme circumstances, the circuit pressure will ceiling automatically as dictated by the fluid dynamic behaviour of the static pressure amplifier device  3 . The system is totally self-regulating and does not require any electronics other than that which is dedicated to the specific renewable energy source. 
     Compressed Air Storage 
     According to  FIG. 2  atmospheric air may be compressed using a similar circuit as shown in  FIG. 1 . In this circuit  15 , an extension of the first one, a second pressure amplifier  11  is incorporated for drawing in the atmospheric air AA, the other, 3, having the same function as in the first example, for maintaining the circulating water volume CW. The supply of water is as a rule kept at a low volume by a flow control means, in the simplest case a valve (not shown). 
     The gas is separated from the water in the separator  12  and then passed to a compressed air storage vessel  13  through non-return valve  8 . This compressed air can then be metered out through valve  9  for whatever end application it is required. In the event of severe fluctuations, the non-return valves  8 ,  10  and additionally  14  prevent loss of water and residual pressure from the system. 
     Desalinating Water Using a Fluctuating Power Source 
     The desalination of salt water becomes extremely inefficient and unreliable when using the technique of reverse osmosis (RO) if the feed pressure to the membranes fluctuates. Utilising the compressed air storage technique according to  FIG. 2 , an integrated desalination system may be designed as shown in  FIGS. 3-5 .  FIG. 3  demonstrates the filling mode where a large volume of seawater is brought under pressure simultaneously with the build-up of a compressed air supply. In  FIG. 4 , the water production mode becomes operative, and in  FIG. 5  additional possibilities are shown. 
     According to  FIG. 3 , whilst power is available to circulation pump  1 , pressure will build up in the compressed air storage vessel  13  and at the same time salt water drawn from the source  16  will be deposited in the salt water storage tank  18  (arrow  52 ). The pressure regulating valves  24  and  25  are closed and  26  is open, whereas the non-return valves  8 ,  10 ,  14 , and  20  are open. Regulating valve  25 , however, remains closed until the predetermined working conditions are attained, e.g. pressure in storage vessel  13  or salt water level in storage tank  18 . 
     When the power drops, as depicted in  FIG. 4 , the residual pressure within the pressure circuit  19  will close off the non-return valves  10  and  14 , the pressure in storage vessel  13  causes valves  8  and  20  to close as well, the pressure regulating valves  24  and  25  are open whereas valve  26  is closed. This leaves the compressed air in storage vessel  13  to drive the salt water out of the storage tank  18  and through the reverse osmosis membranes  21 , so producing sweet water  22  and brine  23 . 
     As long as power is available, pressurizing loop  19  will continue to supply pressurized air to storage vessel  13  and/or salt water to salt-water tank  18  through the nonreturn valves  8  resp.  20  depending on the pressure conditions in separator  12  resp. the pressure of the circulating water having passed pressure amplifier  3 . 
     In  FIG. 5  several possible alternate outlets  27 ,  28 ,  29 , and  30  are shown for filling the salt-water storage tank  18 . 
     Rather than allow too many cycle changes between filling and water production, a simple electrical and/or mechanical control system can be added, based on the level of stored water in the storage tank. During periods of maintained power input the arrangement depicted in  FIG. 4  will produce sweet water continuously. 
     From the preceeding description, the one skilled in the art can derive many alterations and modifications of the invention without leaving its scope which is solely defined 
     by the attached claims. Some conceivable modifications are:
         Use of another fluid other than water as the working fluid like gases.   The exits of the storage tank, e.g. of storage site  7 , may be arranged at another location instead of the top, particularly at its bottom.