GB2488158A - Water driven reciprocating engine - Google Patents

Abstract

A power generation system utilizing differential tidal sea levels has an elevated body of water stored from the high tide in tanks 1 and 2, the water is released into and out of a chamber containing a mechanical reciprocating piston which drives a power generation apparatus. A draw pump enables the piston chamber to extend below the low tide mark by expelling water from waste tank 3 by use of a venturi driven by the flow of water from tank 2. The piston head acts alternatively as a float and an elevated weight on opposing strokes by adjusting the ballast water it contains. A water recycling system is used which has at least one recycling tank arranged to store water from the cylinder when it is being drained for reuse in refilling the cylinder.

Description

DESCRIPTION -GRAVITY WATER ENGINE

The invention relates to a design of generating power using the difference in level between high and low tide (see thawing 1). This proposed invention is an improvement and redesign of a type known as a positive displacement "hydrostatic engine".

Water from the high tide is stored in tanks and the pressure of gravity on this in relation to the low tide level results in a stored energy source. A piston type arrangement with a hollow chamber for a piston head is made to rise and fall within a chamber by the sequential controlling of the flow in and out of the appropriate tanks (see thawing 3). The rate of operation of this reciprocal piston chamber is not parallel to the rise and fall of the tide. The rate will be far higher and this is necessary for efficient operation of the power generators. The cyclic rate of the machine will be determined by a few factors, primary ones being A) a suitable surveyed site with sufficient mean height of tide (the example site used within this patent is Beachley on the River Severn in the United Kingdom. Approx lSm mean tide height maximum differential at the annual equinox in March and Sm differential at the smallest Neap tide of the year) B) a calculated suitable ratio and volume of primary holding tanks 1 and 2 and their associated sequential tanks, which is Tank 3 and the recycling tanks -in relation to the piston chamber, to enable continual acceptable cyclic operation through to the next high tide replenishment.

The height of water storage in tank 1 and 2 is more important than the vertical volume. A larger surface / volume area at a higher level is better than a more restricted height / volume capacity that extends at a lower level.

The piston head itself is hollow and part of the system sequence is to empty and fill the piston head with water to control the buoyancy during the rising and falling of the piston. Negative buoyancy when the piston is on the downward stroke and positive buoyancy when on the upward stroke. See drawing 7 and 8 for piston head buoyancy operation.

An important factor is that the piston chamber and piston head can be of a large magnitude. All it needs is for the matching tanks to be scaled to suit. The force of gravity acting upon a body of water held at an elevation above the surrounding sea level is very large indeed. This is why water is so heavy per volume. The greater the elevation and water volume the greater the pressure of gravity trying to pull it back to the Earth's surface. The force of this gravitational pressure acting on the contained and elevated volume of water can be harnessed to generate power, for example, the force of pressure acting in turn for both directions to drive the piston assembly will drive a mainshaft, which will be linked and geared up to drive power generators at an adequate speed.

Similar to Wind Turbines, whose central axis rotational speed is not that great, but the torque is and this drives a substantial electrical generator.

The back EMF of the generators and their design will be considered in the loading/cumulative force calculations for the efficient operation of the system.

One of the unique features of this design/patent are the incorporation of the ability to expel water from below the low tide level at the bottom of the piston chamber bore, by using the "draw pump" device as illustrated in the drawings ( see drawings 3,4,5&6). This allows the piston to travel deeper and thereby increases the stroke. This increases the efficiency of the machine and frees the system from the noimal tidal limits! The "thaw pump" works using the venturi principle. When the external tide level is high, then water is allowed to flow through into tank 2, until the levels are equal (see drawing 2). Then the valves are shut. This flow past the mouth of the "draw pump" toward tank 2 (see drawing 5), creates a venturi effect in the mouth of the draw pump and water is "sucked" by a partial vacuum effect from tank 3, through into the inletloutlet pipe. The draw pump design, as illustrated incorporates rolling ball valves that prevent back flow of water into tank 3(see drawing 4,58th). The system operates on the reverse tide cycle too. When the external tide level is low, the water stored in tank 2, which is at the elevation of the previous high tide, can now be released until the levels are equal, whereupon the valves are shut again. This flow back out the pipe to the external sea, as shown in the diagram, now operates the draw pump again (see drawing 4). Even though the water is flowing past the thaw pump mouth the opposite direction to earlier, it still results in the venturi effect in the mouth of the thaw pump. This thaws a volume of water out of tank 3 again and into the outlet pipe.

Water cannot flow back into Tank 3 due to the design of the "draw pump" which incorporates rolling ball valves that block any backflow (see drawings 4,58th). The balls are less dense than the water and so rise up within their cage runners to seal the orifices of the draw pump when there is no flow/pressure in either direction in the inlet/outlet pipe. My pressure back up the draw pump towards Tank 3 results in the balls rolling upwards to seal the draw pump orifice's. The venturi effect is the creation of a partial vacuum and has been used extensively in industry.

The major benefit of incorporating this design is that the Tank 3 can be sited below the low tide level and can still be emptied, resulting in a deeper/longer piston chamber/travel and that this is not directly limited by the external tide levels (see drawings l&2). Also the number of "Draw Pumps" is not limited to one. It is envisaged that four or more may be used to empty Tank 3 with increased efficiency. Only one is shown in the drawings etc to aid simplicity of theoretical understanding.

Another of the unique features of this system design and to greatly improve efficiency is the incorporation of a recycling system of external tanks, coupled to the main piston chamber by short pipes and controlled by a main "Air Control Valve" (see drawing 3). In drawing 3, two "air control valves" are shown, whereas only one linked to all the recycling tanks is envisaged as part of the system design. Two are shown in thawing 3 to help visual understanding of the recycling tank pipework control.

The recycling tanks are incorporated to maximise the energy output using a limited and quantifiable amount of water. These recycling tanks are shown in two columns each side of the piston chamber in the drawings, but this is just for simplicity in the drawings to convey the information. In practice it is envisaged that these recycling tanks would spiral consecutively around the piston chamber. Also the piston chamber would be most efficient as a symmetrical cylinder but other shapes that the piston head is matched to may be incorporated in the system design.

With the features of this system combined together it is key and fundamental to realise that the cyclic action of the piston/chamber is directly independent of the timings of the tidal daily rise and fall! That is that the system is free of the direct constraints of the tide cycle and in that the tide cycle is only used to fill and help empty the system tanks 1, 2 and 3. The daily tidal cycle is indirectly linked through the water capacity in these tanks to the actual piston chamber itself Whilst being slow moving, the volume of water displaced by the "piston head assembly" can be large. The size of the piston head and chamber and associated tanks etc can be scaled up considerably.

The design here proposed utilises the rise and fall of tide (or of a simulated set up as could be achieved at a suitable river catchment site with the system outlet draining downriver at a lower height or by using a tidal pool to receive the outlet drainage pipe) to retain a large head of water in Tank I (see drawing 2). This is the supply water tank to the main piston chamber. Supplementary sources (not shown) can also be used to further increase the max height of Tank l& 2 and so then the piston chamber with its recycling tanks. For example a small nearby watercourse feed or even rainwater catchment from the roof or around the systems buildings etc. Tank 1 has its primary water feed by a direct pipe from the sea (or suitable river etc). This will be sited below the "Low Tide" level. Water is stored within this tank and the inlet is controlled by a one way valve. Originally water from this tank 1 is fed through a one way valve into the main piston chamber until frill. Initially and once off this will use a lot of water, but in subsequent operation, due to the adjacent recycling tanks, then only a limited replenishment amount will be necessary. It is important to note, that tanks 1, 2 & 3 and the piston chamber will have a constant open vent to the atmosphere. The recycling tanks are not vented directly to the atmosphere but are controlled by a main "air control valve" which controls the timing and sequential venting to the atmosphere. These recycling tanks also have an air lock at theft connection to the piston chamber (see drawing 3). This prevents the air in the recycling tank from escaping into the piston chamber after the water that was previously in the recycling tank has been emptied into the piston chamber, so that it now contains air and now that the water level in the piston chamber has subsequently risen past the mouth of that particular recycling tank.

The piston operation is as follows. (see drawings 7 & 8) Initially at the very first fill of the piston chamber, the water can be supplied from the inlet / outlet pipe and then topped up to the correct operating level.

All subsequent cycles will fill the piston chamber first from the recycling tanks in sequence from bottom to top. The top levels for that cycle will be empty due to no recycling tanks at a higher level having any stored water available, so the shortfall is topped up by Main Tank 1.

To enable full utilization of the travel of the piston at the top of the stroke, the following sequence takes place. Tank 1 will at this time be topping up the piston chamber to the maximum operating level. The piston head assembly is allowed to "float" to the uppermost of its travel.

The piston head acting as a float will ride slightly out of the water. At this time the water level surrounding the head but within the piston chamber will be slightly higher than the level inside the the piston head due to the down pressure on the contained water due to the air trapped inside the piston head and the weight of the mechanical assembly bearing down upon it, ie displacement and that this results in a different height to the surrounding water which will be at the same height as that within Tank 1.

At this time and to preserve maximum upward piston travel, the piston shaft is temporarily locked in place and the piston head air vent is opened at the same time as water from tank 1 is being fed into the piston chamber. This will only be a very brief continuation of feed from Tank 1 until the level inside the piston head will equal that surrounding it and so will be at the same height as that within Tank 1. Tank 1 feed is now shut off.

Now the piston shaft is unlocked and the piston head air vent remains open, causing the piston head to "sink" until it is full of water, whereupon the air valve closes. This "sink" of the piston head is actually the start of the descent of the piston assembly.

While this piston assembly has started to descend, the water level sw-rounding the piston head is lowered by evacuation into the recycling tank system. The rate of this lowering of the surrounding water is at a steady advance of the rate at which the piston assembly is allowed to descend. It must be remembered that the piston head contains its full volume of trapped water and the water/air tight seal at its base must not be broken by allowing the surrounding water level to descend below the hollow base rim of the piston head. This balance point needs to be controlled and maintained.

This sub operation gains the downward pressure of the majority of the volume of water contained within the piston head. This is achieved by the way the system operates when the piston head is descending and in conjunction with the control of the water release from within the piston chamber. It is an act of balance and control. The back pressurefEMF of the power generating set up is controlled so that the rate of descent of the piston head is matched to maintaining the descending water level in the surrounding piston chamber to be slightly higher than the bottom edge of the hollow piston head. This prevents the water that fills the piston head from being able to run out and equalise its level with that in the piston chamber itself Tn so doing this, the weight of the water within the piston head, which will be considerable, is utilized to increase the downward pressure of the piston assembly in relation to the opposing forces of the generation assembly and additional friction within the system.

The main piston chamber wall has outlet ports at descending heights. These drain sequentially downwards into the corresponding recycling tanks around the outside of the piston chamber (see thawing 3).

During the draining/downward piston stroke, the volume that drains into a recycling tank is transferred from the preceding or next higher recycling tank level, but is actually from the matched water volume within the piston chamber. These two volumes should be matched, so that a recycling tank is equal to or greater than the next available volume within the piston chamber that cart drain into it or on the upward piston stroke, that the recycling tank can empty into and fill the next lower volume level of the piston chamber! At the bottom internal volume level of the piston chamber, there will be no effect to having an adjacent recycling tank to receive and hold any water. The recycling tank adjacent to the second level is there to receive water from the equivalent third internal piston chamber level before feeding it back into the piston chamber at the bottom level upon the main system refill. The same is the case at the very top level of the piston chamber in that no recycling tank can be efficiently utilized. All volume dimensions and build measurements will be scaled to suit the site and other design considerations.

Continuing with the downward piston stroke/drainage cycle, the water contained within the bottom 2 piston chamber levels, including the water contained within the hollow head piston assembly is quickly flushed out into Tank 3 and the valve then sealed shut again. This is the operation of the downward piston stroke.

Now for the operation of the upward piston stroke. With the hollow head piston assembly air release valve shut, the recycling tanks empty in a controlled sequence from bottom to top to fill a large proportion of the piston chamber back up. The piston will be buoyant and rising in relation to this sequence. Volume and timings to be co-ordinated with engineering, water stored volume and power generation considerations.

The upper levels of the piston chamber and are now topped up and the head itself partially filled by the main Tank I. This is the only time water from Tank 1 needs to be used! Tank I, as also all other tanks and the piston chamber are size matched to suit the design capacity. The piston chamber volume will be decided in relation to the site and amount of water supply to it and in relation to the tidal level variation and any supplementary input. The recycling tanks will be size matched to the piston chamber. Tank 1& 2 will then be calculated to hold enough volume at a high enough level within it, to be able to supply the cyclic operation of the system through enough cycles until the high tide replenishes Tank 1 and 2 to the maximum possible of that tidal cycle. Within this practice, Tank l& 2 must hold enough water so as the level does not drop low so that the stroke of the piston is not minimized below a determined economical level. All parts of the system are size matched. Pipework and valves and all other parts of the system are matched to suit.

The system will be controlled by sensors and actuators linked to a control network. For example, each recycling tank and its corresponding internal volume of the piston chamber will be monitored by level sensors which will feed information to the control network, which will then operate the valves and other actuators appropriately (a closed loop system).

The relative dimensions of the structure, tanks, pipes etc are shown "Not To Scale" in the drawings. The drawing portrays the simplified theoretical model of the system. The number of recycling tanks for example may be increased in number or their volume altered. They will however be cumulatively matched to the main tanks recyclable volume as determined by the site and its design parameters. The main drawing shows a hypothetical ground surface for ease of drawing, whereas the system may well be sited farther inland where there is a more gradual inclination of the ground surface. This is one ecological advantage of the system. Underwater turbines with their spinning prop and clearance issues or the build and maintenance practicality of them is avoided with this design. The main inlet/outlet pipe is built out into the sea, but this is of minimal impact by comparison and the main system apparatus is built and maintained inland from the natural waters edge. The structure will be mainly below ground level and visual ecological impact will be negligible. Maintenance will be easier and conventional, Turbines incorporated into dams give a good efficiency, but the dams are a considerably greater construction proposal along with all the ecological issues and that the suitable sites are more limited. Many of the here proposed system installations can be sited out of the way at suitable locations along the UK coastline and then electrically linked together in a nodal or semi network if desired for power generation utility. Mother advantage is that security can be maintained due to the underground nature of the installation.

The system proposed here incorporates a recyclic method to increase efficiency. It relies more on bulk of water with less head/height of the water required than a dam turbine system which uses greater height to produce higher pressure at the turbine and is an "open loop" type system. Dam Turbine sytems are often represented in an environmentally green light by referring to the fact that they pump water back up to a higher level at night when the electricity rate is cheaper. This is not actually environmentally friendly or efficient as far as generating electricity is concerned as it uses more power to pump back up than is generated by the same volume flowing through the turbines. It only is efficient in the sense of a financial market/money generation model. The here proposed invention is of a "closed loop system" and all the water of the main input to the system in Tank 1, then actually passes through and directly acts as a force to drive the piston. So whilst being of a low revolution over time system compared to a combustion engine, the efficiency of the fuel used is very high! The water in Tank 2 to operate the "Draw Pump" is a secondary system function and will adequately empty Tank 3. In conclusion of this closed loop sensor controlled system, all sub parts of the system relate and are scaled and matched to each other and the surrounding environment.

This proposed invention is a localised and independent system model. The system can be multiplied and extended or minimized as required. Many countries have long coastlines with many areas of high tide which are ideal for utilization.

Drawing 2 is generally not to scale, except the tide heights which were drawn originally at 1:25. The drawings scale has since been altered, but the relative spatial ratio of these tide heights is correct.

Tide heights used as an example are from Beachley on the River Severn in the United Kingdom (see data below). The tide height data is for Mean heights and the actual annual height varies to some degree, so the system herein proposed and described will need a slightly larger capacity than the Mean height data suggests. Also any usable extra water input sources may increase this again. If creating an artificial water volume height differential, for example an inland structure utilizing water sources and dams, then it is possible that the volume height differential may be artificially greater again.

Date -22/03/2011 Spring Equinox High Tide 14.3 im at 8.49am MHS Low Tide -0.25 mat 3.55pm MHN Date -29/3/2011 Neap Tide High Tide 8.85 m at 4.3 9pm MEN LowTide 3.8Omatll.4lpm MLN The piston shaft as described is linked to power generators. The main beneficiary would probably be electrical generators The housing structure for these would best be sited underground but above the piston shaft assembly to provide direct drive and for design and security considerations. (see thawing 1) It is proposed that the system be automated.

Drawing 1 shows a Hypothetical setting at I3eachley in the Rivern Severn Estuary in the United Kingdom.

Drawing 2 shows a block diagram of the system operation layout but not showing the Recycling tanks for reasons of clarity.

Drawing 3 shows the Piston Chamber operation with the Recycling tanks and Draw Pump.

Drawing 4 shows the Draw Pump operating by pulling from Tank 3 due to the main flow towards the main Outlet from Tank 2.

Drawing 5 shows the same process but with the main flow reversed and now from the main Inlet towards Tank 2.

Drawing 6 shows the Draw Pump self sealing if any flow tries to re-enter Tank 3 Drawing 7 shows the flushing of water from the Piston Chamber and Piston Head when the piston has reached its furthest downward travel.

Drawing 8 shows the release of trapped air from the Piston Head when the piston has reached its furthest upward travel.

All drawings are "Not To Scale"

Claims (6)

1. CLAIMS1) A Power generation system created by harnessing the force of gravity acting upon differential tidal sea levels. Using a mechanical piston in a chamber to be powered by the physical energy of the force of gravity acting on an elevated, contained and controlled release of a volume of headwater within the system. The efficiency of the system to be so improved by the incorporation of an integrated recycling system and an increased piston stroke afforded by the systems "draw pump" expelling of water and also by the "piston head internal topping up" configuration as described.The same reciprocating piston coupled to a mechanical drive assembly connected to power generators. The herein described system being governed by a control system.
2. 2) A system as in claim 1, where parts of the system described and illustrated may be applied where the differential of the water levels to supply and operate the system may be derived from any other water source.
3. 3) A system as in claim 1, where the tanks and chambers described may be of any deemed suitable shape, proximity and orientation.
4. 4) A system as in claim 1, where the parts of the system described and illustrated may be so multiplied, extended and enlarged, as deemed appropriate for the described system objective.
5. 5) A system as in claim 1, where the term water as used for the example given, may also be ascribed to as any fluid used to power the herein proposed system.
6. 6) A system, substantially as herein described and illustrated in the accompanying drawings,