GB2539943A

GB2539943A - System for recovering energy from transient weight applied to a path

Info

Publication number: GB2539943A
Application number: GB1511583.5A
Authority: GB
Inventors: Nankali Ali
Original assignee: Nazanin Nankali; Powerdea Ltd
Current assignee: Nazanin Nankali; Powerdea Ltd
Priority date: 2015-07-01
Filing date: 2015-07-01
Publication date: 2017-01-04
Anticipated expiration: 2035-07-01
Also published as: GB2539943B; GB201511583D0

Abstract

A system for recovering energy from transient weight e.g. pedestrians applied to a path, has a support assembly 1 with a support 2 suspended by springs 4 above a base 3. The support 2 and base 3 form a variable volume sealed chamber 6. When a weight loads the support 2 the chamber volume decreases, exhausting a pulse of primary fluid to a primary motor 12. The primary motor 12 increases the pressure of a secondary working fluid stored in an accumulator 15 until the pressure in the accumulator exceeds predetermined value. The controller 20 then controls a discharge valve 19 to open the accumulator and discharge secondary fluid at high pressure to a turbine driven power generation sub-system. A plurality of supports may form a tiled area to cover a path, and may be covered by a resiliently flexible carpet.

Description

System for Recovering Energy from Transient Weight Applied to a Path

Technical Field

The invention concerns a mechanical power producing system able to extract energy from the transient weight of pedestrian or vehicular traffic passing over a region of a path. The energy recovered can be accumulated, stored indefinitely and efficiently converted to electrical energy.

Prior Art US 2007,246,940 A1 discloses an energy recovery system having multiple energy recovery units. Each unit consists of a platform suspended on a piston disposed in a hydraulic cylinder filled with hydraulic oil. When a vehicle overrides the platform the weight of the vehicle depresses the platform driving the piston and thereby discharging the oil to a reservoir. Multiple units are connected to deliver oil under elevated pressure to a common reservoir. The reservoir is arranged to deliver the oil to drive a turbine coupled to a generator. Exhausted oil is recirculated from the turbine to a supply reservoir and hence to each platform. Check valves and governors regulate the direction and pressure of oil flow.

The system of US 2007,246,940 requires the provision of a deep weil in the road surface to accommodate each platform and piston assembly as well as trenches and other groundworks to accommodate reservoirs, the turbine and generator.

Such works are disruptive, expensive and limited to locations where subterranean features such as services and water table are compatible.

Energy is delivered to recovery systems of this sort in impulses of irregular duration and size because vehicles arrive on the platform at irregular intervals, at various speeds and weigh different amounts. The oil in US 2007,246,940 will therefore be delivered to the turbine in pulses of variable duration, speed and pressure.

Turbines are only energy efficient over narrow ranges of working fluid parameters such as pressure and speed. They are generally only efficient when operating for prolonged periods within the range of their designed operating parameters so that frequent stopping and starting associated with unpredictable oil pressure and speed fluctuations will render the system inefficient and have deleterious impact on its endurance. DE 199857660A1 proposes a system generally similar to US 2007,246,940 A1 except that the platform and well are replaced by a surface mounted ramp comprising two flat inclined plates hingedly connected at the apex. As a vehicle climbs the ramp the vehicle weight causes the ramp to articulate about the hinge moving down to displace a piston in a cylinder which pumps an hydraulic fluid from a reservoir to a turbine. This concept addresses the problem of the well required by US2007,246,940 but is only of any potential use where a speed ramp type device is acceptable. US6091159A discloses in one embodiment a platform suspended by coil springs above a compressible bladder trapped between the platform and road surface.

Fluid contained in the bladder is discharged to an accumulator and then a turbine before being recycled to the bladder via a reservoir. The turbine is coupled to a generator. This system requires a specially adapted ribbed road surface to retain each bladder. In a second embodiment the platform is suspended above the road surface by coil springs. A lever attached to one side of the platform is moved up and down by the depression and recovery of the platform. This in turn actuates a positive displacement primary pump which pumps a working fluid in a primary hydraulic circuit to an accumulator in the primary circuit. The accumulator discharges fluid to a turbine and coupled generator before recycling to the pump. The maximum operating pressure of the system is therefore determined by the maximum pressure achievable by the primary pump. WO 2009/037559 discloses a platform suspended above a road by coil springs to sit at a rest height when unloaded. A plurality of primary piston and cylinder pumps is situated under the platform in direct fluidic communication with an oleodynamic motor. The oleodynamic motor is coupled to a generator. As a weight provided by a motor vehicle impinges on the platform the platform falls driving each piston of the hydraulic pumps to propel hydraulic oil to the oleodynamic motor. The motor is caused to spin rotating the generator and generating electricity. Oil is discharged from the motor to a reservoir and returned to each pump as the platform rises in reaction to the weight being removed. A problem with all the above referenced systems is that the pressure developed in the working fluid is dependent on the weight applied to each platform. Achieving high and preferably nearly constant operating pressures for prolonged periods is essential to efficient operation of the turbine generator couple. This problem is exacerbated where it is desired to use the energy recovery system in pedestrian locations because the weight applied to any platform is relatively much less than for a vehicle. Use in pedestrian locations is preferred from an ecological standpoint since the energy recovered is actually renewable, whereas the energy derived from vehicles is generally generated from fossil fuels.

It is an object of the present invention to provide an energy recovery system to derive energy from transient weight which alleviates at least some of the technical problems exhibited by the prior art described above.

Statement of Invention /(3i?/7According to the present invention there is provided a transient weight energy recovery system comprising: a support assembly, adapted to be deployed on a pre-existing path, said support assembly comprising a support, a resilient suspension mechanism and a primary pump, the suspension mechanism being arranged to urge the support up to a rest position and allowing the support to fall in response to a weight applied to the support, the primary pump arranged to be powered by the motion of the support to pump a primary working fluid around a primary circuit, the motion of the primary working fluid powering a primary motor/pump, to increase the pressure of a secondary working fluid in an accumulator, a controller responsive to accumulation of the secondary working fluid above a predetermined pressure, to discharge the secondary working fluid to a turbine generator assembly, until the secondary working fluid pressure falls below an efficient operating range.

In a preferred deployment of the system a plurality of support assemblies are shaped to be tiled together. Support assemblies can therefore be tiled to form a long and wide region of support platforms covering a region of a path.

As a weight is applied to a single platform, or group of adjacent platforms a kerb will form between each depressed platform and the adjacent un-weighted platforms. The region of platforms may be covered by a continuous carpet of flexible fabric which minimises the effect of the kerbs forming as each platform is depressed by generating progressive ramps between each platform. A system consisting of a plurality of tiled platforms will necessarily require each platform to have a sliding clearance with adjacent platforms which may therefore be vulnerable to fouling. An overlying carpet can protect the underlying support assemblies from fouling or abuse. The carpet may be adapted to provide any one or more of: a. An enhanced traction surface. b. Heated by the inclusion of conductors to prevent freezing. c. Illumination by the inclusion of light sources. d. Information display via printing, painting, or control of regions of illumination for purposes such as advertising or guidance.

Where the support assemblies are tiled together each pump of a tiled region of support assemblies is preferably configured to have a fluid inlet port and a fluid outlet port arranged to communicate with corresponding passages of adjacent support assembly such that multiple support assemblies may communicate outlet ports to a single primary motor. A single primary motor may deliver exhausted primary circuit working fluid to a primary reservoir. The primary reservoir may serve to deliver primary working fluid on demand to the plurality of primary pumps.

Each support assembly may be adapted to be mounted directly onto a pre-existing pathway which serves as a foundation with minimal preparation. Each support assembly may include foot means to accommodate irregular features in the pre-existing pathway so that the support assemblies can be adjusted to a uniform rest position height.

The support, suspension mechanism and primary pump may be formed in an integrated support assembly, which may include flow control valves to control the flow of primary working fluid into and out of the support assembly.

The primary motor may consist of a positive displacement hydraulic motor driving a arranged to achieve an increase in the secondary circuit hydraulic pressure. An object of this arrangement is to allow the primary circuit to operate at low pressure and respond to the relatively small weight and motion tolerable to pedestrian installations as well as vehicle installations. The low pressure primary circuit can safely operate using relatively inexpensive components and environmentally safe fluids.

The primary motor is arranged to increase the pressure of the secondary working fluid in an accumulator from a minimum pressure Pmin compatible with the operation of the turbine to a maximum safe storage pressure Pmax which may be around 200Bar.

An exhaust valve is arranged to prevent the secondary working fluid from discharging from the accumulator until a controller determines that conditions are appropriate for discharge to occur. The accumulator may store energy generated from the support assembly. The secondary working fluid may be a compressible fluid, however the discharge of a compressible fluid to the turbine is liable to be noisy and it may be preferable to employ an incompressible fluid as the secondary fluid.

The accumulator may also store energy via a spring piston wherein a spring is compressed by the secondary motor/pump and urges a piston which acts on the fluid in the accumulator. A controller is may be arranged to determine the store and discharge conditions for the accumulator. The controller will preferably be responsive to the pressure of secondary working fluid stored in the accumulator. Normally the controller will only open the accumulator exhaust valve to allow discharge where the accumulator pressure has reached Pmax. The controller may also respond to other conditions, for example is some applications discharge might only be allowed when there is demand for power. In some installations multiple accumulators may supply a singled turbine/generator sub-assembly and the controller may constrain the discharge of each accumulator in a sequence, one after another to prolong power generation. Because a turbine will only operate efficiently above a specific operating pressure the controller may operate to close the discharge valve when the accumulator pressure falls to a minimum pressure Pmin.

The pressure at the accumulator discharge may also be regulated to a constant pressure to further improve the efficiency of the turbine.

The turbine will discharge exhausted secondary fluid to a reservoir which will return secondary working fluid to the accumulator at a pressure above Pmin.

Brief Description of Figures

An embodiment of the system for recovering energy from transient weight applied to a path will now be described, by way of example only, with reference to the accompanying illustrative figures, in which:

Figure 1 is a diagram illustrating the principle components of a first embodiment of the system;

Figure 2 is a flow chart illustrating the process steps and control parameters of the first embodiment system;

Figure 3A is an exploded perspective view of a support assembly;

Figure 3B is a partially exploded perspective view of the support assembly of figure 3A,

Figure 3C is a perspective view of the support assembly of figure 3B assembled Figure 3D is a sectional view of the support assembly of figure 3C, and Figure 4 is a perspective view of tiled support assemblies.

Figure 5 is a diagram of the principle components of a second embodiment of the system;

Figures 6A-6G illustrate the components and operation of an hydraulic amplifier of the second embodiment of the invention.

Detailed Description of Drawings A transient weight energy recovery system has a support assembly generally identified by 1. The support assembly 1 is adapted to be deployed on a pre-existing path “P”. The support assembly 1 has a support 2 and a base 3. A resilient suspension mechanism comprises four springs 4 is arranged to urge the support 2 up to a rest position and allows the support to fall in response to a weight applied to the support. The support 2 and the base 3 cooperate with a sleeve 5 to form a fluid sealed chamber 6 the volume of which varies as the support 2 falls towards or rises from the base 3. The primary chamber 6 is formed with an inlet port 7 which communicates with a one way valve 8 configured to allow a primary working fluid to flow into the chamber only. The primary chamber 6 also includes an outlet port 9 which communicates with a one way outlet valve 10 configured to allow the primary working fluid to flow out of the primary chamber 6 only. Thus a primary pump is formed between the support 2 and base 3.

When a weight causes the support to fall, the volume of the primary chamber 6 is reduced causing an fluid filling the chamber to be discharged through the outlet port 9 via the one way valve 10 into a chamber to primary hydraulic motor conduit 11 whereby pressurised hydraulic fluid is delivered to motivate a primary motor 12.

The primary motor consists of a piston 12A captured in a cylinder 12B and connected to the hydraulic ram 13 via a connecting rod 12C.

Each incremental motivation of the primary hydraulic motor 12 incrementally actuates an hydraulic ram 13. The incremental actuation of the hydraulic ram 13 compresses a spring piston assembly 14 in an accumulator 15 to increase the pressure applied to a volume of fluid 16 contained in a cylinder chamber 17 of the accumulator. The pressure accumulated in the accumulator provides the means to pump the secondary hydraulic fluid around a secondary hydraulic circuit such that the accumulator acts as a secondary circuit pump. The pressure of fluid in the accumulator and secondary hydraulic circuit is greatly in excess of the pressure in the primary hydraulic circuit. The pressure (Pmax) may reach 200Bar.

The spring piston assembly 14 comprises a ram 14A connected to the hydraulic ram 13 via a connecting rod 14B. The ram 14A engages a coil spring 14C captured between the ram and a piston 14D. The piston 14D is sealingly engaged in the cylinder chamber 17. The coil spring 14C acts as an energy storage device and may be replaced by other resilient means including other spring means. A discharge port 18 provides a passage for the discharge of high pressure secondary fluid controlled by a motorised discharge valve 19. The discharge valve is controlled by a controller 20 responsive to a pressure sensor 21 arranged to sense the fluid pressure in the accumulator chamber 17. A high pressure discharge conduit 19A conveys secondary fluid to a turbine 22. A governor valve (not shown) may be included in the discharge conduit 19A to govern the pressure at which secondary hydraulic fluid is discharged from the accumulator chamber to a substantially constant predetermined discharge pressure.

Turbine 22 may be any kind of rotary machine designed to convert hydraulic pressure to torque and thereby turn the shaft of an electrical generator 23. The turbine generator couple forms an energy generating sub-system.

Exhausted fluid is discharged from the turbine 22 via a turbine discharge conduit 24 to a secondary fluid reservoir 25.

When the accumulator 15 is discharged secondary hydraulic fluid can be pumped from the reservoir 25 to refill the accumulator 15 via accumulator fill conduit 26. A one way valve 27 is provided in the fill conduit 26 to prevent fluid discharging from the accumulator 15 to the reservoir.

In the primary circuit fluid is discharged from the motor 12 via a primary discharge conduit 28 to a reservoir 29. When the transitory weight is removed from the support 2 the springs 4 raise the support to its rest position expanding the primary chamber 6 and drawing fluid from the reservoir 29 through a return conduit 30 back into the primary chamber to keep it filled.

As can best be seen in figures 3A-D and 4 each support assembly 1 comprises a base 3 formed of a ground engaging bottom panel 31 of generally rectangular cross planform. The bottom 31 is surrounded by an upstanding continuous base wall 32. Four guide tubes 33 extend up from the interior surface of the bottom 31. Extending continuously around the exterior surface of the base wall 32 is formed an endless channel 34. Coil springs 4 are mounted, one each, around each guide tube 33.

The bottom, guide tubes and side walls are preferably formed from a single integral plastics moulding.

The sleeve 5 is rigid and generally rectangular in planform to correspond to the shape of the outside of the bottom wall 32. A resiliently deformable ridge 35 is provided extending around a bottom edge of the sieeve 5, inwardiy facing and sized to seaiingiy snap engage in the channei 34 whereby it is secured to the base 3.

The support 2 is aiso of generaiiy rectanguiar pianform and has a generally flat top 36 from which depends top waii 37 which may be of similar shape and configuration to the base waii 32. The top waii 37 has an exterior surface formed to slidably fit into the upstanding sieeve 5. A channel 38 extends around the lower rim of the top waiis 37 to receive a seaiing ring 39. Thus when the top walls 37 are slidably received into the sieeve 5, a variable volume fluid sealed chamber is formed within the support assembiy.

The springs 4 are sized to act in compression between the top 36 and the bottom 31. The top 36 overhangs the depending top wall so that when multiple support assemblies are nested together on a path iittle or no space remains between the tops but space is provided between the waiis of adjacent support assemblies to accommodate suppiy and discharge conduits, the iniet vaives 8 and outlet valves 10.

As diagrammatically illustrated in figure 1, the support assembiies are preferabiy depioyed in a tiied formation to cover a substantiai region of a path. When a weight, such as a passing pedestrian vehicie is appiied to any one or severai adjacent support assembiy tops, the support falis against the resistance of the springs 4.

The support is oniy permitted to faii a smaii maximum distance of between 0.5 cm and 2 cm because more than this is excessiveiy discomfiting to a pedestrian or vehicie. However, a smaii kerb is inevitabiy created between any adjacent faiien top 36 and any top at its rest height. To minimise the effect of this kerb and to protect the supports from wear and fouling they are preferably covered with a resiliently flexible carpet 40. The carpet 40 may extend beyond the extent of the tiled region of support assemblies to provide a substantially rigid ramp 41 at the approach or exit from the tiled region.

Figure 2 shows the process and control of the system. When the system is initiated at step 1, each primary chamber of each support assembly is filled with a primary working fluid which may be water, hydraulic oil or any other incompressible fluid.

The primary motor 12 will have the piston 12A at the bottom of the largely evacuated cylinder 12B as shown in figure 1. The accumulator 15 will be charged to capacity with secondary fluid at pressure Pmin. The accumulator ram 14A will be at the top of the cylinder with the spring 14C. The motorised valve 19 will be closed.

At S2 a transient load such as a pedestrian or vehicle moves onto the region tiled with support assemblies and the load is therefore applied to one or more supports 2. The support 2 falls in response to the transient load overcoming the spring force of springs 4 and this reduces the volume of the primary chamber 6 therefore ejecting a pulse of fluid through the one way outlet valve 10 at S4. The pulse of pressurised fluid is delivered via conduit 11 to the primary motor 12 at S5. Primary motor 12 actuates the hydraulic ram 13 which in turn compresses the spring piston 14. The primary motor 12 and hydraulic ram constitute a pressure amplifier capturing each pulse of low pressure delivered from the primary hydraulic circuit as high pressure in the secondary circuit. Thus at step S6 each application of a transient weight to a support incrementally increases the pressure of the fluid in the accumulator chamber.

The accumulator chamber also acts as an energy store holding a charge of energy for use when desired at S7.

At S8 the pressure sensor 21 detects the pressure in the accumulator. At S9 the controller 20 compares the detected pressure to Pmin. At S10 if the pressure is below Pmin the controller drives the motorised valve 19 to the closed condition or to maintain the closed condition. If the pressure is above Pmin the control goes to S11 where the sensed accumulator pressure is compared to a maximum safe storage pressure Pmax. If the pressure is below Pmax the controller drives the valve 19 to the closed condition at SI 2 however if the pressure detected exceeds Pmax the control goes to step SI 3 where the valve 19 is opened to discharge secondary fluid to the turbine and generate power.

The control then goes to step SI5 where the detected pressure is compared to Pmin. If the pressure still exceeds Pmin the control goes to steps SI3 and valve 19 is kept open. If the pressure is determined to be below Pmin the control goes to S14 where the valve 19 is closed. The control then goes from S14 to S9.

Figure 4 illustrates how each support assembly is provided with an inlet valve 8 and an outlet valve 10 disposed asymmetrically on opposite side walls of the base 32. If each support assembly is notionally bisected by a horizontal lateral line “L” in figure 4; then the one way inlet valve 8 is on a wall opposite to the one way outlet valve 9 and each vale is on opposite sides of the lateral line “L”. Thus when nested together it is possible to arrange each inlet valve of each adjacent support assembly to face left and each outlet valve to face right facilitating communication of adjacent support assemblies with common inlet and outlet conduits.

In most installations it is envisioned that multiple support assemblies tiled over a region of a path will communicate hydraulically with a single accumulator. In some applications multiple accumulators may communicate with a single generator sub-assembly. Such multi accumulator assemblies may be configured to cascade discharge the accumulators to the common generator sub-assembly to provide more prolonged or continuous power generation.

Figure 5 illustrates a second embodiment of the invention wherein the mechanical pressure amplifier components 12A-13 of the first embodiment are replaced by hydraulic components. Where components are common to both embodiments they are similarly enumerated.

In the second embodiment the primary hydraulic motor conduit 11 communicates with an hydraulic cylinder 112 containing a float piston 112A above a first chamber 112B. A first float chamber 112C is provided in the cylinder 112 above the float piston 112A. The primary circuit exhaust passage 28 is normally closed by a pilot operated check valve 128A. Thus each pulse of hydraulic fluid delivered from the primary chambers 6 is accumulated in the low pressure chamber 112B causing the float piston 112B to rise towards the top of the chamber and urge the hydraulic fluid in the top of the chamber to discharge through a check valve 113 through a conduit 113A into a secondary ram piston chamber 114A which is closed by a ram piston 114B.

The fluid may exit from the ram piston chamber 114A via a return passage 117 normally closed by a pilot valve 118 communicating with an hydraulic fluid reservoir 119. The surface area of the ram piston 114B is sufficiently much greater than the surface area of the float piston 112B so that the force applied to the spring 14C exceeds the maximum spring force required to fully compress the spring 14C and the underlying fluid 16 in the chamber 17. When the stroke of the float piston 112A impinges on a line control port 112D the pressure in control line 128B is altered causing the check valve 128A to open and allowing the primary hydraulic fluid to discharge from the bottom float chamber 112B to the primary reservoir 29. Fluid is prevented from returning to the top float chamber 112C from the secondary piston chamber 114A by the check valve 113, instead the drop in pressure in the top float chamber opens a check valve 115 in a circuit supply line 116 leading from a low pressure reservoir 119 to fill the top float chamber 112C. When the float piston 112A reaches the bottom of the cylinder 112 the discharge to the primary circuit exhaust passage is stopped with the closure of the check valve 128A. Thus the cylinder 112 is reinitiated to continue pumping fluid to the secondary piston chamber 114A and charging the spring 14C.

Having described the system components which differ from the first embodiment figures 6A to 6G show diagrammatically the stages of operation of the second embodiment as follows:

In figure 6A the hydraulic amplifier is primed ready to respond to impulses of pressurised fluid from the primary chamber.

In figure 6B the float piston 112A has been displaced by the pulses to the top of the cylinder 112 driving fluid into the ram piston chamber 114A and therefor urging the ram piston 114B down to compress the spring 14C.

In figure 6C the float piston 112A is recycled back to the bottom of the float cylinder 112 to reinitiate the float cylinder and enable further charging of the ram cylinder 114A.

In figure 6D the float piston 112A has recycled to the top of the float chamber 112 causing further compression of the piston spring 14C to its maximum compression. In figure 6E the control unit has opened the control valve 18 to discharge the secondary fluid to the turbine and generator.

Claims

1. A transient weight energy recovery system comprising: a support assembly (1), adapted to be deployed on a pre-existing path (P), said support assembly comprising, a resiliently suspended support (2) responsive to application of a weight to power a primary pump, said primary pump being responsive to the weight to pump a primary working fluid around a primary hydraulic circuit to power a primary motor, said primary motor arranged to incrementally increase the pressure of a secondary working fluid in an accumulator (15) of a secondary hydraulic circuit until sufficient energy is stored to efficiently power an energy generating sub-system, and a controller (20) sensitive to the magnitude of energy stored in the accumulator (15) to discharge the accumulator to the energy generating sub-system when a predetermined energy level is achieved.

2. A system according to claim 1 wherein the support assembly comprises a base (3) adapted to engage the surface of the pre-existing path (P).

3. A system according to claim 1 or claim 2 wherein the support and the base cooperate to form a variable volume primary chamber (6) and a one way inlet valve (8) and a one way outlet valve (10) are formed on the base (3) to form the primary pump.

4. A system according to one of claims 1 to 3 wherein the resilient suspension is provided by at least one compression spring (4) disposed within the chamber (6) acting between the base (3) and support (2)

5. A system according to any one of the preceding claims wherein the primary motor (12) is arranged to incrementally displace a spring piston assembly (14) whereby the spring is compressed to store the energy imparted from the primary working fluid.

6. A system according to claim 5 wherein the spring piston (14) is arranged in a chamber of the accumulator (15) to compress the secondary working fluid.

7. A system according to any one of the preceding claims wherein a pressure sensor (21) is arranged to sense the pressure of secondary working fluid in the accumulator.

8. A system according to claim 7 wherein the controller (20) is arranged to drive a motorised discharge valve (19) to open and close a secondary fluid discharge port in the accumulator to control the discharge of high pressure secondary fluid to the energy generating sub-system.

9. A system according to claim 8 wherein the controller is responsive to the pressure sensor (21) sensing a pressure in excess of a predetermined maximum pressure (Pmax) to open the motorised valve (19), and responsive to the pressure sensor (21) sensing a pressure falling below a minimum pressure (Pmin) to close the discharge valve (19).

10. A system according to claim 9 wherein a pressure regulator is provided at the discharge port of the accumulator (15) to reduce the discharge pressure to a constant pressure.

11. A system according to claim 10 wherein the constant pressure is optimised to maximise the efficiency of the generator sub-assembly.

12. A system according to any one of the preceding claims wherein the support assembly is shaped to tile a region overlying a path.

13. A system according to claim 12 wherein multiple tiled support assemblies covering a region are covered by a resiliently flexible carpet.

14. A system according to any one of the preceding claims wherein a ramp is provided at a kerb formed at the entrance and/or exit from a tiled region of support assemblies.

15. A system according to claim 14 wherein the ramp is integral with the carpet.

15. A system according to claim 14 wherein the ramp is integral with the carpet. Amendments to the claims have been made a follows: Claims

1. A transient weight energy recovery system comprising: a support assembiy (1), adapted to be depioyed on a pre-existing path (P), said support assembiy comprising, a resiiientiy suspended support (2) responsive to appiication of a weight to power a primary pump, said primary pump being responsive to the weight to pump a primary working fluid around a primary hydrauiic circuit to power a primary motor, said primary motor arranged to incrementaiiy increase the pressure of a secondary working fluid in an accumuiator (15) of a secondary hydrauiic circuit to exceed the pressure in the primary circuit, untii sufficient energy is stored to efficiently power an energy generating sub-system, and a controller (20) sensitive to the magnitude of energy stored in the accumulator (15) to discharge the accumulator to the energy generating sub-system when a predetermined energy level is achieved; wherein the support assembly is shaped to tile a region overlying a path; and the support assembly comprises a ground engaging base, supporting a continuous upstanding base wall and a top from which depends a top wall, and a sleeve formed to slidably receive each of the bottom and top walls to form a variable volume fluid sealed chamber.

12. A system according to claim 1 wherein the top overhangs the depending top wall so that when multiple support assemblies are nested together on a path no space remains between adjacent top edges of adjacent support assemblies but space is provided between the walls of adjacent support assemblies to accommodate supply and discharge conduits, inlet valves and outlet valves.

13. A system according to any of claims claim 1 to 12 wherein multiple tiled support assemblies covering a region are covered by a resiliently flexible carpet.