Abstract:
Flexible pipe liner harvests energy from pressure fluctuations of a fluid in a pipe and converts it to electricity to power local sensors or other equipment. Pipe may be a pipeline for carrying water, sewage, or oil; or may be an open-ended segment suspended in a body of water. Pipe liner also serves to reinforce or repair a pipeline and is constructed of conventional materials.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to production of electricity and more particularly to production of electricity from pressure fluctuation in an enclosed fluid. 
     BACKGROUND OF THE INVENTION 
     A potential source of energy that has not been well utilized to date is harvesting of waste kinetic energy. An example of a good use of otherwise wasted energy is regenerative braking systems used in hybrid cars. Regenerative brakes transform the kinetic energy of the car into electricity that is stored in the battery. 
     Another potential type of waste energy is the kinetic energy of moving or pressurized fluids, in either a man-made or natural system. 
     Many attempts have been made to harvest electricity from the deformation of various flexible or stretchy membranes in contact with a moving or pressurized fluid, such as auto tires, a rubbery tube that is stretched by ocean waves, or leaf-like ribbons that undulate in a river. Piezoelectric material is in some manner attached to the flexible membrane to convert the bending or stretching motions directly into electricity. 
     For example, Adamson et al. in U.S. Pat. No. 7,429,801, issued Sep. 30, 2008, teach the use of commercially available piezoelectric fiber composite material in some detail. 
     Other attempts to generate electricity from the kinetic energy of moving water first convert the complex motions of the water into a simpler type of motion, such as that of a waterwheel, a piston, or an oscillating (but not stretchable) membrane. Then the rotary or linear motion is converted into electrical energy. 
     Auto tires produce only tiny amounts of electricity, such as enough to transmit data from an internal air pressure sensor. This is a useful, but very limited application. Other systems in the patent literature for generating larger amounts of electricity with stretchy membranes require dedicated, rugged apparatus fabricated from special materials. This also limits their usefulness because of the high costs of fabrication, permitting, and installation. 
     At least one pilot scale turbine has been placed in a municipal water main. This appears useful in certain cases where the water has far more energy than it needs to arrive at its ultimate destination, such as when water has been pumped over mountains then flows down by gravity. In the more typical case of water pressurized by a pump for the purpose of causing it to flow in a relatively level pipe, any apparatus that impedes the flow is probably not beneficial. 
     There is still a need for systems to harvest waste kinetic energy, such that from moving water, that do not impede the flow of the water. In the case of pumped water or other fluid, it is especially vital that energy is not actually “stolen” from the pump. There is further a need for energy harvesting systems that use conventional materials and construction techniques. 
     SUMMARY OF THE INVENTION 
     The present invention is an apparatus for creating electricity by converting pressure fluctuations in flowing fluids, such as the undesired pulses called “water hammer,” into useful electrical current. The system generally includes a rigid pipe through which water or other liquid flows, flexible carbon fiber composite sheets lining the inner surface of the pipe, an isolator sheet between adjacent pairs of carbon sheets, and conductor elements to collect and conduct the generated electricity. 
     The pipe may be a water main conducting drinking or irrigation water, a sewage pipe, a pipeline for dumping treated industrial waste, a pipeline for petroleum or liquefied gas, or similar man-made pipe. The pipe may alternatively be an open-ended segment of pipe, such as a hollow cylindrical shell made from concrete or steel, that is submerged in a body of water, such as a river, waterfall, or ocean current. 
     The carbon fiber composite sheets are typically attached to the inner surface in multiple layers, which may be separated by isolator, i.e. dielectric, layers. 
     This laminated liner responds both to radial forces (substantially normal to the longitudinal axis of the pipe) and shear forces. A typical source of radial force is the periodic rapid fluctuation in pressure known as water hammer. Shear forces largely result from turbulence and friction. A benefit of the present invention is that the flexible liner damps the high pressure pulses so that damage to the interior of the pipe is decreased. 
     The present invention has a cost advantage over previous attempts to scavenge power from moving fluids by building special devices to place in a fluid. Existing large concrete or iron pipelines are commonly lined to repair damage to the pipeline and extend the useful life. The method and apparatus of the present invention can be easily adapted such that the liner also serves this repair function. By applying the energy conversion system to a pipeline already in need of repair lining, much of the expense of installing the energy conversion system is thus “paid for” by the needed repair process. A further advantage is that materials and automated equipment already developed for pipe repair can be employed in the practice of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic representation of the present invention, showing the energy conversion apparatus of the present invention attached to a section of conventional pipe. 
         FIG. 2  is a partial sectional view, with vertical axis exaggerated, of the apparatus and pipe of  FIG. 1  taken along line  2 - 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows the energy conversion apparatus  10  of the present invention, connected to a section of a conventional pipe  100  for conveying fluid such as pressurized drinking water. 
     Pipe  100  defines a hollow inner volume  110 , through which a fluid (not shown) such as drinking water, air, sewage, or petroleum may be conveyed by gravity or by pumping means. Pipe  100  includes an inner surface  101  facing inner volume  110  and an outer surface  102 . The fluid flows generally in the direction of pipe  100 &#39;s longitudinal axis L. 
     Pipe  100  may be of indeterminate length, but is typically composed of pipe segments  115  that are two to ten times as long as their diameter. A pipe segment  115  is typically made from concrete or cast iron, but other materials are suitable. The inner diameter of pipe segment  115  is preferably greater than  12  inches but may be as much as several feet. 
     The elements of energy conversion apparatus  10  are usually attached to an individual pipe segment  115 . If many pipe segments  115  are connected end-to-end to create a long pipe  100 , the elements of energy conversion apparatus  10  of individual pipe segments  115  are also connected together to create a larger apparatus  10 . Energy conversion apparatus  10  may be operated attached to a single pipe segment  115 , although the electrical output naturally increases in proportion to the number of pipe segments  115  connected together. 
       FIG. 2  is a sectional view, cut away and with vertical axis exaggerated for clarity, of apparatus  10  and pipe  100  of  FIG. 1  taken along line  2 - 2 . 
     Apparatus  10  includes pipe liner  11  attached to pipe inner surface  101 . Pipe liner  11  typically includes at least one pair of electricity-producing layers, such as carbon fiber layers  12 ; and an isolator (dielectric) layer  13  between each pair of carbon fiber layers  12 . Isolator layer  13  separates carbon fiber layers  12  both physically and electrically. Layers  12 ,  13  are preferably attached to inner surface  101  and to each other with suitable adhesive (not shown), typically an epoxy resin or a cementitious material such as grout or cement that is not degraded by the fluid conveyed by pipe  100 . The adhesive typically penetrates the entire thickness of the carbon fiber layer and forms a matrix around the fibers. 
     It has been reported (Mingquing Sun, et al.,  Cement and Concrete Research ) that carbon fiber embedded in cementitious material polarizes and creates electricity in response to deformation. Testing of the present invention has borne this out. 
     Apparatus  10  further includes collection means  20  for collecting and conducting the electricity produced by pipe liner  11 . Collection means  20  typically includes collection conductors  21  attached to pipe liner  11  and an output cable  22  that connects collection conductors  21  to some device  50  for receiving the produced electricity. 
     Various types of collection conductors  21  for energy-harvesting installations are known in the art and include conductive fibers embedded in a matrix or woven into a layer and, as illustrated herein, a layer of conductive sheet material  14  such as thin metal foil. In the preferred embodiment illustrated, one pair of carbon fiber layers  12  are sandwiched between two conductor layers  14 . 
     As shown in  FIG. 2 , the outermost layers of liner  11  are two insulator layers  15  that insulate liner  11  electrically and protect it from mechanical damage. 
     In a preferred embodiment, insulator layer  15  and conductor layer  14  are combined in a single sheet of metallized Mylar or the equivalent. Conductor layer  14  is the metallized face of the Mylar and insulator layer  15  is the Mylar base. 
     Next, a first carbon fiber layer  12  is attached over first conductor layer  14  by suitable adhesive means (not shown) such as grout or cement. Carbon fiber layer  12  may consist of a woven or knitted sheet of carbon fiber fabric or it may be created in situ by laying carbon fiber yarns closely together, typically in a helical pattern. Either method of lining pipe  100  may be done manually (in the case of a pipe  100  large enough for a person to enter) or by a machine that travels through pipe  100  either under its own power or by being drawn by a cable. Methods of lining a pipe are well known in the art. 
     If a second, or more, carbon fiber layers  12  are to be installed, an isolator layer  13  is attached over first carbon fiber layer  12 . Isolator layer  13  is composed of a suitable material such as non-metallized Mylar, Teflon, porcelain, mica, or similar non-conductive material. Isolator layer  13  could be sprayed in place, or could be a separate film or panel that is attached over first carbon layer  12 . Isolator layer  13  is attached by a suitable adhesive such as cementitious material or polymeric resin. The choice of insulator material is determined by cost, durability, compatibility with the other materials, and degree of stiffness desired. 
     Electricity that is produced by carbon fiber layers  12  is collected by conductor layers  14 A, B. Collection means  20  may be wires embedded alongside conductor layers  14 , wires soldered or otherwise attached to conductor layers  14 , or similar means as is known in the art. Collection conductors  21  lead the electrical current to output cables  22  and then to a device  50  that uses, stores, or modifies the electrical current. Output cables  22  are shown in  FIG. 2  as connected to both carbon layers  12  of the pair to form a simple circuit with a device  50  that receives the generated electricity for conversion to DC current or for other use or modification. 
     Typically, the electrical current is brought outside of pipe  100  by the passage of output cables  22  through one or more apertures  112  provided in pipe  100  or pipe segment  115 .