Abstract:
Renewable energy systems extracting energy from natural water flow or wind. The energy systems are configurations of long-stroke open-channel reciprocating engines employing one or two flow engaging elements such as drogue chutes for water flow or airfoils for wind applications tethered to a power drum and useful to generate electricity or to pump water as from wells. A wind energy system using two buoyant airfoils emblazoned with advertising messages is suitable for urban deployment generating electric power and also supporting an advertising revenue stream.

Description:
RELATED U.S. APPLICATION DATA 
     This application is based upon my Provisional application No. 60/234,035, filed on Sep. 20, 2000. 
    
    
     OTHER PUBLICATIONS 
     “Distributed Wind Power Assessment”, February 2001, National Wind Coordinating Committee, Washington D.C. 
     “Ads Put Profit in Wind Power”,  Popular Mechanics , June, 2001, page 20 
     BACKGROUND OF THE INVENTION 
     Wind energy conversion systems, as currently deployed, are horizontal axis turbines mounted atop towers. It has been found that there is some economy of scale as well as other advantages such as lower incidence of avian mortality and less obtrusive acoustic noise output in deploying very large units of 1.5 megawatt or even larger capacities. However, out of necessity, these are usually part of large centralized “wind farms” with dedicated electrical transmission lines. Local construction of turbine blades and towers are almost required because of the difficulty of transporting the physically large sections. Often access roads to remote sites must be built for transporting the turbine and tower sections as well as for the cranes and large rigging equipment required for erection and repairs. Distributed wind power installations must use smaller turbine units which are designed to interface with existing or upgraded distribution networks at lower voltages. The rural environments compatible with distributed wind power often do not have three-phase AC distribution which is a requirement for even modest (eg.—50 kw) units. Needless to say, high population density areas and high buildings in urban environments, while having adequate distribution networks and ready markets, are not a good match to a technology using towers (which also precludes their attachment to existing structures due to large moment loads and vibration). No known wind energy systems are compatible with the direct generation of other forms of secondary revenue streams. 
     In considering extraction of energy from natural water flow such as streams, tidal flow, or river currents, the sequestering of flow behind dams or barriers has traditionally been required. This incurs large outlays of capital, and often substantial environmental impact to man and to marine life. Pressure changes and sharp rotating blades within commonly used hydro turbines are themselves a danger to fish fry. The installations for hydroelectric plants or tidal generating facilities are generally permanent and unmovable fixtures. 
     SUMMARY AND OBJECTS OF THE INVENTION 
     This invention introduces the notion of a long-stroke open-channel reciprocating engine as an alternative to the turbines presently used to extract energy from the flow of water or air. Certain features of this type of reciprocating engine are analogous to other well known reciprocating engines such as steam or internal combustion engines. For example, the functions of pistons, crankshaft, valves, and connecting rods have direct counterparts while the cylinder, a flow confining element, has no counterpart in this “open-channel” engine. The engine of this invention uses drogue chutes to engage water currents or airfoils to engage wind in a manner analogous to pistons. Tethers of strong fibers such as nylon or aramid attach the drogue chutes or airfoils to a periodically reversing power drum which is turned when tether unwinds, not unlike the interaction of connection rods and crankshaft. Since this is a long-stroke engine, the power drum will turn multiple revolutions during one engine stroke. Valves have a direct counterpart in control of the drogue chutes or airfoils as they are purposely switched from a high pull mode (high drag and/or lift) to a low pull mode (low drag and/or lift) or vice-versa at the end of a stroke. As in other engines with a single piston, the most simple version has a single drogue chute or airfoil which extracts mechanical energy from fluid flow as it unwinds tether from the power drum in high pull mode and then must be wound back on the power drum while in low pull mode using parasitic energy; this is a “single-acting” engine which extracts net positive energy over a complete cycle, but only on alternate strokes. Slightly more complex, an engine of this invention using two drogue chutes or airfoils can extract net positive energy from fluid flow on each stroke (ie.—“double-acting”) since one element is always in high-pull mode while the other is in low-pull mode reversing their respective roles at the end of each stroke. The extracted mechanical energy results from the difference in pull forces between the high-pull element unwinding tether from the power drum and the low-pull element being rewound onto the power drum. The parasitic loss is still there, but the power produced is almost continuous except for the brief pause at the end of each stroke during mode switching. 
     For water flow applications, the reciprocating engine of this invention can extract power directly from flow without sequestering it behind barriers or dams. In fact, an engine of this invention can be simply suspended below a moored barge. A system using a single drogue chute can follow rapidly shifting water currents without entanglement. Systems using a pair of drogue chutes can better extract energy from flowing water currents where rapid direction shifts are not a problem. The cyclic opening and closing of soft fabric structures such as drogue chutes at ambient pressure pose no threat to aquatic life; such movement is also conducive to self-cleaning from encrustation as from barnacles. The fact that very large drogue chutes can be deployed at very modest capital outlay compared to that of erecting and maintaining permanent civil works for alternate approaches implies lower system costs are indicated. Note that the systems of this invention for water applications are portable; they can be moved seasonally to optimize power generation or to accommodate other seasonal uses of a particular water area. 
     The advantages for wind energy conversion systems of this invention over traditional wind turbines are many. One important factor is that no towers are required. Heavy base equipment such as power transmissions and generating equipment is at ground level where it can be safely maintained without climbing towers. No very large elements are needed for this invention. Even large capacity systems can be transported over normal roads or even taken up elevators and erected on building roofs since no moment loading is involved and vibration is controlled as for any large mechanical device by known techniques. Using two self-buoyant helium or hydrogen inflated airfoils or a pair of non-buoyant fabric airfoils such as flexifoils attached to buoyant aerostats, the airfoils are simply suspended in the air regardless of the amount of wind. When wind picks up, the airfoils will synchronously reciprocate by virtue of mechanisms which adjust their angle of attack to control lift and/or drag to produce low pull and high pull modes as needed. Because of the inherent safety factors and lack of towers, these systems would be more easily integrated in populated commercial or industrial areas where adequate distribution lines exist and markets for generated electric power are in the local vicinity. Thus, the wind systems of this inventions are ideal for distributed wind energy in urban environments. Because of their integration with populated areas and the opportunity available by virtue of highly visible areas on the airfoils or their aerostats, the display of commercial logos or advertising messages can constitute a second revenue stream to enhance the profitability of such wind energy systems. Besides the urban deployment, other unique factors enhance the suitability of these wind systems where wind turbines with towers cannot compete. These systems can be deployed in hurricane prone areas since the airfoils can just be reefed at ground level and secured in case of impending storms. Small systems are so compact that they can even be back-packed and instantly deployed for camping use or for powering scientific instruments in remote windy areas. Similarly, they can be used on pleasure craft or recreational vehicles. Major wind farm installations off-shore can be simply installed on moored barges, no permanent towers below water level need be erected. On a grand scale, special airfoil designs with “super-tethers” can be used to extract power from the jet stream. For wind farm applications, it may be possible to locate these systems in non-picturesque areas with good wind resource that would be prohibitive to harvest due to the high towers that would be necessary with conventional wind turbines. With these systems, airfoil height is simply a function of the length of a tether. 
     For water pumping applications on farms, it is possible to erect simple single airfoil systems that even use non-buoyant techniques by employing a tall light weight tower that just supports an airfoil at its lowest stroke position if the wind ceases to blow. This type of system can be built locally of indigenous materials. Buoyant techniques would eliminate the need for even this light weight tower. In either case, no power drum is necessary if reciprocating motion can be used directly for powering a reciprocating pump. Simple techniques for valving of the single airfoil can be implemented using an auxiliary tether from ground level, or these systems can use a self-regulating wind turbine powered mechanism situated aloft adjacent to the airfoil. This mechanism would cyclically adjust the airfoil in high-pull and low-pull modes as long as the wind is blowing. The difference in pull force would operate the water pump in a reciprocating fashion. These systems for water pumping save money in erection costs and first costs by eliminating the high cost of towers used by conventional water pumping windmills. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention can best be understood in connection with the accompanying drawings. It is noted that the invention is not limited to the precise embodiments shown in drawings, in which: 
     FIG. 1 is a Side elevation of water current system using a single drogue chute; 
     FIG. 2 is a Side elevation of a wind system using a single buoyant airfoil; 
     FIG. 3 is a Side elevation of a water current system using two drogue chutes; 
     FIG. 4 is a Side elevation of a wind system using two buoyant airfoils; 
     FIG. 5 is a Perspective view of mechanism for converting reversing rotation to unidirectional rotation; 
     FIG. 6 is a Side elevation of electrically operated mode switching mechanism for water system use; 
     FIG. 7 is a Side elevation of flow-operated continuous mode adjustment mechanism for water system use; 
     FIG. 8 is a Side elevation in partial crossection of a complete water current system; 
     FIG. 9 is a Side elevation of water-pumping wind system using a light tower structure; 
     FIG. 10 is a Side elevation of wind-operated mode switching mechanism; and, 
     FIG. 11 is a High level perspective view of a complete wind energy system using two buoyant airfoils. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The most important cost metrics for assessing the suitability of renewable energy systems for generating electric power are $/installed kW and cents/kWh. Both factors are a function of many parameters that range from cost for real estate to hourly wages for maintenance crews. These metrics are also related to the technology used. The technology used in this invention tends to minimize capital and labor-related installation costs as described in the summary. The low environmental impact and the serendipitous linking of advertising revenue for the wind energy versions are other factors which relate to the feasibility of an installation. The operations and maintenance (O&amp;M) side of the equation is more questionable especially for the wind versions using buoyant elements. However, materials advances point to favorable outcomes. NASA&#39;s Ultra Long Duration Balloon (ULDB) project describes a multi-layer composite balloon material known as DP6611.25/PE which can have application to the airfoils and aerostats of this invention. It is a very light weight durable low-permeability fabric with the potential for extending preventive maintenance schedules to attractive intervals. It is a five layer composite with a polyester woven fabric load bearing layer, a 0.25 mil Mylar film fabric stability/barrier layer, a 0.25 mil PE film for toughness/tear resistance/back up barrier, and two adhesive layers. 
     The inventor has personal experience with drogue chutes for the water versions of this invention. Experiments using a heavy fabric parachute style drogue chute which can be placed in a low-pull mode by pulling on a center “dump cord” (which causes the chute to fold down into a low crossection profile perpendicular to flow) showed promise. The ratio of high to low pull at usable river flow velocities were 4:1 or greater. The inventor also has personal experience with parasail type airfoils of nylon ripstop construction using attached weather balloons as buoyant elements. These also had acceptable high-pull to low-pull ratios although the lift was limited; however aerodynamic drag can be used effectively as an surrogate parameter. A variety of airfoil shapes are described in the drawings of this invention. An exhaustive performance comparison or airfoil design for this application has not as yet been performed; the shapes described are presumed to be sub-optimal. 
     FIG. 1 shows a side view of a water power concept to extract energy from water current  1  using a single drogue chute  4  which is alternately placed in a high pull mode as shown by mode adjuster  6  to pull on tether  5  unwinding from reversing power drum  2  and providing useful torque on shaft  3 . The adjacent low-pull configuration shown attached to a dashed tether  5  is achieved by shortening dump cord  7 . In this configuration, drogue chute  4  is rewound onto power drum  2 . 
     A similar wind system version is shown in FIG. 2 wherein bridle lines  14  are shortened by adjuster  13  to achieve the low-pull configuration shown at the right. On the left, wind from direction  10  is used to provide lift on high-pull configured buoyant airfoil  15  to unwind tether  12  from reversing power drum  13 . Tethers  5  and  12  are wound onto and the ends attached to their respective power drums  2  and  11 . 
     FIGS. 3 and 4 show two conceptual versions for dual flow engaging elements. The water version of FIG. 3, shows a two section power drum  20  on which tethers  21  and  22  are wound in reverse directions such that when tether  22  is unwinding as shown, tether  21  pulling low-pull configured chute  4  is being pulled back by winding onto drum  20 . Similar action is illustrated for a two airfoil wind system as shown in FIG.  4 . Power drum  28  within base equipment housing  29  rotates either clockwise or counter-clockwise (as shown) depending on the airfoil  15  modes at the instant. 
     FIG. 5 shows a mechanism to convert the reversing rotation of power drum  28  attached to shaft  36  to a unidirectional rotation of shaft  35 . While other known mechanisms using either belts or gears to achieve this purpose are known, the operating principles are similar. Although only a mild step-up ratio of a single stage is shown from power drum  28  to generator  47 , in an actual transmission, additional stages would often be used. Flywheel  46  is used to provide ride-through during mode switching at the ends of a stroke. Gear set  37  and  39  drive shaft  35  at a higher speed than drum  28  but only when drum  28  is turning counter-clockwise. This is accomplished by having one-way clutch  37  decouple gear  37  from shaft  36  whenever it is turning clockwise. Similarly, the pulley/belt drive at the distal end incorporating drive pulley  41 , timing belt  45 , and driven pulley  44  drive shaft  35  clockwise when shaft  36  is rotating clockwise (no reversal) at the same ratio as the gear set only when shaft  36  is rotating clockwise. This is accomplished by one-way clutch  40  which decouples pulley  41  from shaft  36  when it is turning counter-clockwise. Power drum  28  is driven by either tether  26  or tether  27  when they are respectively unwinding from drum  28 . 
     FIG. 6 is an embodiment of an electrically operated mode switching mechanism of this invention for water use. This is the only illustrated embodiment requiring the use of tether  58  which has conductive traces embedded carrying current to operate drive motor  50  (which is submersible). Motor  50  is an electrically reversible motor with two or more rotation resisting vanes  53  attached to the housing. It drives lead screw  51  in either direction. Nut  52  with rotation resisting vanes  54  is urged either left or right depending on the direction of rotation of motor  50 . Bridle terminator  56  is coupled via free rotation coupling  57  to the end of screw  51 . Dump cord  7  is attached to nut  52 . In operation, brief periods of motor  50  operation in alternate directions select the opposite operating mode of attached drogue chute  4 . This mechanism can be used for either single drogue chute systems or for those using two since electrical synchronization can be used to simultaneously change the modes of both drogue chutes in different directions at the end of a stroke. 
     FIG. 7 shows a different embodiment of a mode changing mechanism which is continuously driven by water current. This embodiment is usable for single chute systems only since there is no means of synchronization. Tether  65  which may be conductive or non-conductive is attached to reversing screw  68  via swivel coupling  66 . Propeller  67  is rigidly attached to screw  68  and turns it continuously in the same direction as long as water current  10  is flowing. Nut  69  with rotation resisting vanes  70  is continuously driven back and forth since the characteristic of a reversing screw is that a nut driven by one changes direction at the end of travel without a change of rotation direction. Thus drogue chute  4  is continuously opened and closed at a constant rate for constant current  10  flow. A tension sensor on tether  65  can be used to trigger the rewind phase upon sensing a tension lower than a threshold set into the system; the latter can be dynamically set as a function of current  10  velocity. 
     FIG. 8 is a side view in partial crossection of a complete system for extracting energy from moving water currents. In this embodiment, the system is mounted within and below a barge  80  which is moored by virtue of tether  80  and anchor  82  on the bottom  99  of the water channel. Two drogue chutes  4  are used such that one is always placed in the mode opposite the other with modes synchronously switching at the extreme ends of a stroke. As tether  83  unwinds from reversing power drum  86 , tether  84  wound in the opposite direction is wound back on. Outer shaft  85  drives pully  87  which is the power take-off point feeding power to transmission  94  which creates a high RPM unidirectional drive to generator  95  which feeds power conditioner  96 . The output from power conditioner  96  is utility grade power wheeled to shore via cable  98 . Control box  97  feeds controlled pulses of current via slip rings  92  to braked motor  91  which drives planetary gearbox  90  driving inner concentric shaft  88  driving mode control drum  89 . Since gearbox  90  with motor  91  atop is attached to pulley  87 , it rotates with power drum  86 . Shaft  88  can change the length of each dump cord  7  relative to tether  83  or  84 . This is done synchronously every time motor  91  is energized for a short burst at the end of a stroke, then the chute  4  that was closed (low-pull) will open simultaneously with the formerly open chute  4  being closed by shortening cord  7  relative to tether  83 . Motor  91  has a brake which resists rotation when motor  91  is not energized. In this manner, the lengths of dump cords  7  are dynamically moved with tethers  83  and  84  via drum  89  while maintaining their length differentials relative to tethers  83  and  84 . 
     FIG. 9 illustrates an embodiment for a water pumping system built with low-tech indigenous materials. It uses a single parasail type airfoil and no buoyant elements. This is the only embodiment of this invention that uses a tower. Tower  105  is a light weight structure that operationally just has to survive direct wind load and to support airfoil  106  in periods of no wind. Practically, it should also safely support the weight of a service person climbing it during initial installation or for maintenance or repair. Reciprocating pump cylinder  111  and piston rod  112  constitute the well pump which is operated by long rod  110  (a long bamboo pole would suffice). Pivot  109  locates and controls the motion of rod  110 . Parasail  106  pulls power tether  107  up when parasail  106  is in its high lift/drag configuration as shown and wind is blowing. The rest of the system relates to a low-tech mechanism for mode switching; a working model has been built. It consists of rod or tube  118  which can be a wooden dowel or a piece of PVC pipe; its purpose is to guide two hollow elements which ride along it. Top element  116  has springy grippers  117  which will grab onto the upper lip of dump cord  108  weight  114 . This hollow weight element  114  has a latch  115  which prevents it from falling due to gravity but can be easily overwhelmed by a medium pull as by top element  116  being lifted by tether  107  while being mated with weight  114 . Dump cord  108  is of such length that it is slack at the top resting point of  114  as determined by the length of cord  113  which limits travel. In operation, assume that at the start of a cycle, both  114  and  116  are mated and at ground level. If wind is blowing, it will force airfoil  106  open and start lifting rod  110 ,  114  and  116 . When  113  becomes taut,  114  stays at that level while  116  snaps off and continues up until cord  108  becomes taut releasing latch  115  at which point weight  114  falls, thereby closing airfoil  106 . Airfoil  106 , distal end of rod  110 ,  114 , and  116  all go down and  116  mates with  114  at ground level. The cycle has returned to its starting position. This reciprocating action continues as long as sufficiently strong wind blows; it operates water pump  111  by this action. 
     FIG. 10 is a detail of another embodiment of a mode control mechanism for single airfoil systems. A model to demonstrate the operation of this mechanism has been built. It is shown in a system with a single non-buoyant airfoil  106  attached to a buoyant aerostat or balloon  144  which has enough buoyant lift to support airfoil  106  as well as mechanism  131  (which is enlarged relative to  106  to show more detail). Frame  132  is attached to power tether  107  by swivel joint  143 . Small wind turbine  134  turns worm gear  135  which is mated with spur gear  136  driving top timing belt pulley  137 . The timing belt which rides between driving pulley  137  and idler pulley  138  has a single nib  139  which goes up and down continuously at a slow rate determined by wind  10  velocity and the gear ratio between worm gear  135  and gear  136 . Carrier  148  rides on rail  147  and is biased downward by spring  146 . As shown, it is latched at the top position by latch  140 . When nib  139  reaches latch trip  142 , trip cable  141  will release carrier  148  which is quickly pulled down by spring  146 . Since dump cord  130  is attached to carrier  148 , airfoil  106  is closed. It stays closed until nib  139  works it way up engaging arm  149  lifting it toward the latched position and gradually opens airfoil  106 . Thus the cycle is repeated. The percentage of on versus off time can be regulated by moving the location of trip point  142  anywhere along the path of nib  139 . Tether  107  can be attached to a rod which drives a reciprocating pump as in FIG.  9 . Alternatively, tether  107  can be wound around a power drum during low-pull periods and unwound during high-pull periods. Note that an advertising logo  145  or message can be emblazoned on aerostat  144 . 
     FIG. 11 shows a two airfoil system using buoyant airfoils. This embodiment is ideal for larger systems but may also be used on small capacity systems. A subsystem  162  adjacent to each airfoil,  160  shown in high lift configuration or  161  shown in a low lift configuration, is used to perform synchronized precision mode switching. As shown, airfoil  160  is lifting tether  171  which is unwinding from a reversing power drum within base equipment housing  168 . At the same time, tether  172  is being rewound on the same power drum thereby pulling down airfoil  161  through remote pulley  170 . The ground separation is used to minimize the chance of tangling of one airfoil around the other in case of exposure to brief cyclonic wind conditions. Airfoils  160  and  161  are modeled on SkyDoc balloons available from Big Ideas Corp. of Syracuse, N.Y. While probably not optimal, these omnidirectional designs have a fair amount of lift and can be easily placed in a stall position by manipulating the length of part of the bridle. They also have large unencumbered surfaces which are ideal for display of logo&#39;s  174  or other advertising material. The subsystems consist of a bottom swivel coupling to tethers  171  or  172 , a small Savonius rotor  165 , housing  175  containing several items, top swivel connector with slip rings  176 , tail shaft and receiver antenna  167 , anti-rotation tail  166 , short electric cable  177  and extendable electric actuator  163 . The items in housing  175  are a small dc generator for charging a storage device such as a large value capacitor and/or storage battery, a radio receiver for receiving mode switch signals, and driver circuitry for operating actuator  163 . Note that the Savonius rotor  165  adaptively generates more or less electric power as a function of wind velocity; mode switching power demand (number of switches per unit time) is also a function of wind velocity. Signals for precise mode change at the extreme ends of a stroke are perfectly synchronized by radio signals from transmitter  169  with antenna  173  attached to the side of housing  168 . Note that for safety reasons (lightning protection) tethers  171  and  172  are not electrically conductive. Subsystem  162  are small and light weight; power is locally self-generated eliminating the need for long conductive elements. The electronics for subsystems  162  have been proven in hundreds of applications such as industrial controls and radio-controlled model airplanes and cars. 
     In the foregoing description, certain terms and visual depictions are used to illustrate the preferred embodiment. However, no unnecessary limitations are to be construed by the terms used or illustrations depicted, beyond what is shown in the prior art, since the terms and illustrations are exemplary only, and are not meant to limit the scope of the present invention. 
     It is further known that other modifications may be made to the present invention, without departing the scope of the invention, as noted in the appended claims.