An energy conversion system with an electric machine for multiple purposes

Abstract

An Energy Conversion System with an Electric Machine for Multiple Purposes This invention relates to a single machine system shared for wind energy harnessing, water potential energy harnessing and gravity storage. Two common turbines, each of which has multiple circular layers of discrete blades or buckets and is installed on a common shaft and at either side of the machine, are developed for harnessing wind and water energy simultaneously. On each side of the machine, wind and water are fed from separate channels into a common direction-change tube. The common shaft is coupled with that of the machine through pairs of gearboxes to increase angular speed for running the machine more effectively. The water falls from high terrain to low terrain to gain speed while the wind is accelerated by using funnel shaped accelerator in wind tower to reach tens of metres per second for effective energy conversion. A lifting mechanism is installed in the system to fulfill the potential energy storage of concrete or other heavy blocks when there is neither wind nor water. The system could be modified for 1) harnessing wind energy only but can operate as a motor to drive mechanical loads when there is no wind; 2) harnessing water and wind energy at river or lakes' side without gravity storage.

Description

Field of invention

[0001] This invention relates to a single machine system shared for wind energy harnessing, water potential energy harnessing, gravity storage or driving mechanical loads. When there is wind and / or water, the system is used to convert their kinetic energy into electricity fed into a power system. When there is neither wind nor water, the system is used to store gravity potential energy by lifting up concrete or other heavy blocks from lower platform to high platform if the power system has extra power or release potential energy by lowering down the concrete or other heavy blocks from high platform to lower platform if the power system is short of power.

[0002] The system could be modified for 1) harnessing wind energy only but can run as a motor to drive mechanical loads when there is no wind; 2) harnessing water and wind energy at rivers or lakes’ side without gravity storage.Background

[0003] Although our earth is abundant of metals and other materials, their exploration and mining are costly. To convert wind and water kinetic energy into electricity, it is indispensable to use iron, aluminium, copper and other materials to build electric machines. To reduce the use of such materials, one may increase the operating time of each machine across a year. There have been many efforts to achieve this target so far. For example, one electric machine is used for harnessing water kinetic energy and it can also be used to drive mechanic load when there is no water but abundance of other power supply in a power system. In the invention, a new system is developed to harness wind kinetic energy, water kinetic energy and also to achieve gravity storage using a common electric machine.Brief description of the drawings

[0004] Figure la Multi-stage single-phase inverter;

[0005] Figure lb AC microgrid;

[0006] Figure 2a Landscape and system arrangement for the development of three-in-one machine system;

[0007] Figure 2b Part of the side view and top view of the system;

[0008] Figure 3a Cut cross sections of partitioned water / wind guides feeding water / wind to the entrances of the direction-change tubes through connectors A and B (upper graph) and their top view (lower graph);

[0009] Figure 3b Switch from water guide to wind guide;

[0010] Figure 4a Vertical cut cross section view of the three-in-one machine system;

[0011] Figure 4b Gearbox coupling the common shaft with that of the machine;

[0012] Figure 4c Mechanism for preventing water leak;

[0013] Figure 5a View of unfolded cross section of the direction-change tube with multiple layered segmented passages for water and wind from a cylindrical surface;

[0014] Figure 5b Skew view 1 of a practical direction-change tube (5b, 5c, 5d drawn MY Wang);

[0015] Figure 5c Skew view 2 of a practical direction-change tube with joining parts hidden ;

[0016] Figure 5d Side view of a practical direction-change tube with passing-through hole for the common shaft;

[0017] Figure 5e Second design of direction-change tube for water / wind;

[0018] Figure 5f Illustration of part of the cross section of direction-change tubes and the corresponding buckets in the water / wind turbine;

[0019] Figure 6a Conveying systems between auxiliary wheels and driving machine;

[0020] Figure 6b Belt sheet sided with modified bicycle chain for lifting concrete or other heavy blocks (Drawn MY Wang);

[0021] Figure 6c Vertical cut cross section view of the auxiliary and driving wheels.List of numbers used in drawings

[0022] 1A,1B: stationary direction-change tubes for wind / water;

[0023] 2A, 2B: wind / water turbines installed on the common rotational shaft;

[0024] 3 A, 3B: disc-shape water block (rotational with shaft);

[0025] 4, 5, 6, 7: bearings;

[0026] 8: machine;

[0027] 9A, 9B: wheel mounted on the common shaft for gravity storage;

[0028] 9C, 9D: two auxiliary wheels for gravity storage;

[0029] 10: common shaft shared by wheels, water / wind turbines;

[0030] 11A, 1 IB: water vapor blocks (stationary);

[0031] 12A, 12B: boxes of gear coupling;

[0032] 13A,13B: water guide with cover at the top;

[0033] 20: underpass for transferring concrete blocks;

[0034] 30A, 30B: shape-change guides, also named as connectors A and B;

[0035] 50A, 50B, 50C, 50D: Steel reinforced concretes;

[0036] 60A, 60B: docking areas (high);

[0037] 60C, 60D: docking areas (low);

[0038] 70A,70B,70C: metal wire nets with slot for the belt to pass through.Detailed description

[0039] Although nuclear fusion generation has attracted tremendous investment from both governments and private agencies and is evolving very fast, renewable energy generation will be still indispensable within next twenty years. Such systems, especially economical, environmentally friendly and sustainable ones are being developed equally prosperously and have been widely used in power generation.

[0040] One of the circuit topologies which can be adopted for renewable energy generation is shown in Fig. la. Such a circuit not only can be used to build single -phase or three-phase autonomous microgrid operated at constant frequency but also can be adopted for grid-connected operation. One detailed application is shown in Fig. lb, where the upstream cluster is formed by a grid-forming generator, DSTATCOMs and back-up gridforming generators running as grid-supporting generators under normal operation, each of which is built using three identical units as in Fig. la in either delta or wye connection. A separate 50 / 60Hz transformer with small power level in delta-wye connection with its secondary side in wye-connection is adopted and connected in parallel with the inverters. The neutral of the transformer and metal casings or enclosures of the inverters are connected to a common large grounding or earthing grid. At downstream, multiple local microgrids with autonomous operation capability are built. The total generation of multiple local microgrids could be several times greater than that from upstream cluster. Therefore, if the system is designed in such a way that the power from the upstream into each local microgrid only takes a small fraction of its local generation, then even if the upstream is disconnected due to a fault, each local microgrid still can sustain the power supply to its local loads.

[0041] Although many types of sources for the DC microgrid including fuel-cell unit, battery unit, conventional gas / diesel generation with AC / DC rectifier, PV panels with DC / DC converters, wind generation with AC / DC / DC converters, and gravity storage with its converter circuits etc could be used, more are being intensively sought to make our civilization sustainable.

[0042] In many countries, there are vast undeveloped or underdeveloped regions between neighbouring cities which could be potentially used for harnessing renewable energy. One may identify those suitable terrains with enough sea-level or altitude differences for manmade lakes. Even for those plain regions, one may excavate one large upper lake and multiple lower lakes with their surfaces having enough vertical differences.

[0043] Such a system could also be built at the bottom of a mountain where one upper lake and multiple lower lakes are built or along a riverside with sufficient altitude difference across a realistic distance. Then the used water will be fed back to the river without influencing the water consumption downstream. High-power DC microgrids could be built in such regions where generations from multiple renewable sources and storages are adopted to reduce the level of energy crisis.

[0044] In this invention, a three-in-one renewable generation system is proposed to use one common machine to facilitate water potential energy harness, wind energy-based generation and gravity storage -based generation. The inventor proposed very briefly about this technology in the paper titled “Simulation and Analysis of Single-phase Multistage DC-AC Inverter with Medium-frequency Transformer Isolated DC / DC Converters” in the 5th International Conference on Power Engineering (ICPE 2024), Shanghai, China, December 13-15 2024. Details on this technology are disclosed here in this patent application. Such a system could be a new member in a large-scale DC microgrid. It could also be operated in the grid-connection mode.

[0045] Throughout a whole year, most regions on the earth experience four seasons with different weather conditions. Therefore, it is necessary to use a complementary combination of wind energy, solar energy, potential energy from rainwater and necessary diesel / gas-based generation etc to provide sufficient power to consumers across a whole year. Using a machine system to harness several types of energy could reduce the usage of iron, copper and aluminium and other materials. Figure 2a illustrates the landscape and system arrangement for the development of such a three-in-one generation system. An upper lake is built to accumulate water, which could be pumped by using siphonage with pipes built across its dam for reducing erosion of its bank as shown in Fig. 2a. A lower lake or multiple lower lakes are built some distance away from the upper one with sufficient space reserved for gravity storage. If the water in lower lakes is supplied for daily consumption by the residents nearby, then the scale of each downstream or lower lake can be reduced. Multiple three-in-one generation systems are built some distance LI from the upper lake as shown in Fig. 2a to avoid water leakage to gravity storage region.In the meantime, there should be some distance L2 away from the lower lakes for reserving sufficient space for accommodating gravity storage.

[0046] Multiple wind towers with funnel accelerators are installed as well to harness wind energy at the top terrain as shown in Fig. 2a and long partitioned tubes are used to guide the wind from the exits of the accelerating funnels to the machine system. It is necessary to build a mechanic switch to block the wind when the machine system is used for other purposes. Therefore, wind acceleration can be achieved by using multiple stages. In the first stage, the wind speed is increased by only several times. At its exit, a mechanic switch is installed to fulfil the block of the wind. In the following stages, the wind will be further accelerated to reach useable speed range.

[0047] Figure 2b shows part of the side view and top view of the machine system, direction-change tubes 1A, IB, connectors 30A, 30B between the exits of partitioned water / wind guides and the entrances of the direction-change tubes 1A, IB, docking areas 60A, 60B, 60C, 60D for loading / unloading concrete or cement or other heavy blocks, tunnels for linking low docking areas 60C, 60D to low parking platforms, water guides with covers 13 A, 13B, two sets of four- metal-guide poles along which container or heavy concrete blocks’ holder moves. It is also necessary to build metal wire nets and fences 70A, 70B, 70C for such areas to prevent fatality from happening. All the areas in Fig. 2b together with low and high platforms need to be covered by a roof to ward off erosion by rain and other weather conditions.

[0048] Instead of using three-in-one generations, one can also use two-in-one generations: wind + rainwater or wind + gravity storage or rainwater + gravity storage or just use it solely for wind energy harnessing. Gravity storage could play a significant role as it can be used to store solar energy when there is neither water nor wind energy. By doing so, the generation system use rate across a year is sharply increased. This could compensate for the inefficient design of the three-in-one machine system. Then compared with other remote generations with long transmission lines, the proposed method is economical and could be material- saving as it could be built relatively close to end users.

[0049] One may just use the system to harness wind and / or water energy without gravity storage. For this design, at the time of having little or no wind / water but surplus of solar energy or other energy in the power system, the machine could run as a motor to drive mechanical loads.

[0050] Figures 3 through 6 show more details of the system to meet three-in-one generation target.

[0051] Figure 3a illustrates the cut cross sections of partitioned water / wind guides feeding water / wind to the entrances of the direction-change tubes through connectors A and B (upper graph) and their top view (lower graph). Downward partitioned water guides along slopes are built to guide the water to flow from the top located at the exit of the water conduit to the bottom of the slope. The purpose of the partition is to reduce friction between water molecules, thereby retaining water speed. Then the exits of partitioned water guides are joined with the entrances of each direction-change tube either 1A or IB through either connector A or connector B as shown in Fig. 3a. Large wind towers, each of which is pivoted on its supports are built at high terrain as shown in Fig. 2a. On top of each wind tower, there are large multiple-faceted wind entrances. By using funnel-shaped guides, the wind speed is accelerated. Long partitioned guiding tubes are adopted to connect the exits of each of the funnels to the multiple entrances of either connector 30A or connector 30B. Then the accelerated wind is fed into the entrances of direction-change tubes 1A, IB. The connectors 30A and 30B are the conglomerates for both wind and water. For a practical application, each sub-exits of the partitioned tubes for water and wind can be connected directly to the entrances of the direction-change tubes 1A, IB without using connectors A and B.

[0052] As there are days with little rain but strong wind, it is more effective to channel the wind to the passage of water by using a series of mechanical switches as shown in Fig. 3b, each of which can be switched on separately to join the respective entrance of the partitioned water passage. By doing so, water energy and wind energy generations can complement each other.

[0053] One possible design for the machine system and wind / water turbines 2A, 2B is shown in Fig. 4. Two nearly symmetrical water / wind entrances into water / wind turbines 2A, 2B at each side of the machine 8 are adopted in the design. Then there are two nearly equal circumferential pushing forces produced and acting on the shaft from the two sides of the electric machine 8, which is installed on a sufficiently thick and large steel or other solid block chassis with necessary vibration buffers on steel reinforced concrete foundation 50A, 50B, 50C, 50D as shown in Fig. 6c. Compared with force acting only from one side, this arrangement could reduce torsional force on the shaft 10, thereby extending its life span.

[0054] The exits of each partitioned water guide and wind guide could be in circular or rectangular shape. That is why it is necessary to have a pair of connectors A and Bcommon for both wind and water, also named as shape-change guides 30A, 30B that need to be installed as shown in Fig. 3a.

[0055] As the directions of wind and water from the exits of the shape-change guides 30A, 30B are along the axis of the machine system, a direction-change tube needs to be introduced to change the direction of water / wind before they are applied to water / wind turbines 2 A, 2B as shown in Fig. 2b and Fig. 3a.

[0056] As there are necessities for mechanical stand support for the direction change tubes 1A, IB, a design as shown in Fig. 4a can be adopted. In this design, longer common shaft 10 is adopted, and its two terminals sit on two different bearing supports 5, 7. Then the multi-layered segmented donut shaped or other-shaped direction-change tubes 1A, IB just sit on their respective support. Space is left in the centre of the direction-change tubes 1A, IB to allow the common shaft 10 passing through them as shown in Fig. 4a.

[0057] Figure 4b shows the gearbox coupling between the common shaft and that of the electric machine. As the angular velocity of the common shaft driven by water / wind is not high enough to drive the machine effectively, multiple pairs of high-ratio gearboxes are necessary to increase the angular speed to higher one. By doing so, the machine would work effectively to convert mechanical energy into electricity.

[0058] Figure 4c illustrates a system for blocking leak water from water guides 13 A, 13B. By doing so, the areas with the machine would stay immune from water.

[0059] Fig. 5a shows the unfolded cut cross section along a cylindrical surface of the direction-change tube either 1A or IB. Such a change of water / wind direction needs to be coordinated with the shape and geometries of water / wind turbines 2A, 2B in order to maximize conversion of kinetic energy to electricity, or mainly for producing maximum forces along circumferential directions simultaneously from two water / wind turbines on two sides of the electric machine.

[0060] Fig. 5b through 5d show a practical design of the direction-change tubes 1A, IB. One may design each passage one-by-one and join them together with necessary bonds and fixtures. Certainly, one may also build hollow passages with their walls being sufficiently thick as shown in Fig. 5c, join them with necessary fixing connections, and then immerse them with melted aluminium or other alloys to cohere them together to form a complete one as shown in Fig. 5b. Figure 5c shows all the hollow passages without their joining parts. From it, one can see that the direction of the wind / water can be altered effectively.

[0061] Another design of the direction-change tubes 1A, IB is shown in Fig. 5e where rectangular cross sections of the water / wind passages are adopted, and compensating passages are introduced to compensate those areas occupied by bearing supports 5, 7. The compensating passages could be placed either side so long the rotation direction of the machine is properly coordinated. By using the design in Fig. 5e, the length of the common shaft 10 could be shortened. Other shapes of water / wind passages in the direction-change tubes 1A, IB could be taken to facilitate fabrication and friction reduction for the water / wind. For the water passage, same cross sectional areas at the entrance and exit along the direction-change tube could be taken. For the wind passages, it is feasible to have entrance area slightly greater than that at the exit.

[0062] Instead of using separate shape-change guides 30A, 30B for wind and water, one may connect the exits of the downward partitioned water guides and the exits of the partitioned wind guides directly to the multiple entrances of the direction-change tubes 1A, IB.

[0063] As the energy density for wind is much lower than the water, several times more layers of the passages for the wind could be built and arranged at outer layers for higher torque generation.

[0064] Each of the layered wind turbines or water turbines 2A, 2B could be in segmented donut or other shapes to match the exits of the direction-change tubes 1A, IB. Their blade shapes are similar to those buckets or blades in conventional turbines with necessary modifications to match the water / wind flow from the direction-change tubes 1A, IB in order to have maximum circumferential pushing forces from both sides of the electric machine. Fig. 5f shows the sketch of one structure for the action of flowing water / wind on water / wind turbines.

[0065] A possible design for lifting up or lowering down the cement or concrete or other blocks in the gravity storage is shown in Fig. 6, where four wheels 9A, 9B, 9C, 9D, two 9 A 9B being installed on either side of the machine 8 and on the common shaft 10, each of another two 9C, 9D being installed on separate round bars, are adopted for having adequate space to accommodate the movement of concrete or other heavy blocks with sufficient weight along two vertical wells, in each of which there are four vertical guide poles along which each container or concrete block holder with / without the concrete blocks moves. As shown in Fig. 6a, the belt for lifting up or lowering down the heavy blocks is a combination of modified bicycle chains and thin metal sheets. Each metal sheetis sided with two modified bicycle chains with fins inserted in the chains. Fig. 6b shows the construction of such a design.

[0066] Separate pair of bicycle-chain-teeth like conveying mechanism is adopted to couple the driving wheels 9A, 9B with each of two auxiliary support wheels 9C, 9D. Another coupling mechanism for the purpose could be obtained from modifying that in Fig. 6b with only one thin metal sheet sided with two modified bicycle chains, one on each side.

[0067] The belt for lifting up the concrete blocks mechanically couples with two auxiliary wheels 9C, 9D without contact with the driving wheels 9A, 9B as shown in Fig. 6c.

[0068] The system is designed to harness wind, solar and rainwater energy from time to time. So, it is necessary to decouple conveying belt for the container or concrete block holders from the rotation machine system. One method of decoupling as shown in Fig. 6c is to use lifting motors together with a suction mechanism which is designed to be automatic for frequent operating mode change. When it is time for the generation using wind and / or rainwater, the belt is decoupled from the rotation machine system. Then the system only rotates in one direction for electricity generation. When there is neither wind nor rainwater but there are some other sources such as solar energy generation fed to the common DC or AC bus in the system, the belt is placed back and coupled with two auxiliary wheels 9C, 9D for converting solar energy to gravity potential energy. When there is a shortage of power in the power system, stored potential energy is released and converted to electricity. In this operation, the machine 8 rotates in both clockwise and anticlockwise directions alternately.

[0069] For the machine 8 to have higher efficiency when running in the mode of gravity storage, the water / wind turbines 2A, 2B could be designed to be able to decouple from the shaft 10. This is not a desirable approach as it needs more mechanical components which would lead to higher failure rates.

[0070] A design example on water turbine generation and wind turbine generation is shown in Table I and Table II, where the energy and power are estimated by using the formulas (1) and (2) respectively.TABLE I Water based generation>>TABLE II Wind based generation>>

[0071] One can see that potentially such a system is capable of producing quite good amount of energy from each generation. To make full use of the machine’s magnetic materials, one can use greater vertical height of the slope instead of 24m in the example. By doing so, the machine 8 would be pushed to operate at higher speed and the frequency of the induced voltages in the machine 8 reaches higher value. Alternatively, one can also use multiple pairs of gearboxes 12A, 12B to couple the common shaft 10 with that of the machine 8 as shown in Fig. 4b. Then a compact high-speed permanent magnet or other machine could be used.

[0072] The system could be in the grid-connected operation to harness water potential energy and wind energy without gravity storage. Then one may use DFIG or other machines to reduce cost. The drive circuits and their control over the machine are similar to those established and disclosed in the literatures.

[0073] The applicant appreciates the conducive discussion on machine drives part with Dr Matthew Priestley.

[0074] By using multiple such units and together with other sources like PV panel-based generation, three-blade turbine-based wind energy harness, battery or other storage etc, a large DC microgrid in the scale of tens of Megawatts or even higher could be built. Therefore, AC microgrid as shown in Fig. lb could be constructed.

Claims

The claims defining the invention are as follows:

1. A three-in-one machine system, whereinthere are two sets of wind and water turbines on either side of the machine;there are two separate direction-change tubes on either side of the machine to serve the purpose of changing directions of water or wind for maximum circumferential forces generation on the water / wind turbines;there are multiple wind towers sitting at high terrain with funnel shaped accelerators to increase wind speed;there are partitioned channels to guide the water flowing from high terrain to the entrances of the direction-change tubes located at lower terrain through necessary connectors; there are partitioned channels to guide the wind to flow from the exits of funnels to the entrances of the direction-change tubes through necessary connectors;there are two driving wheels for gravity storage, located on either side of the machine system;there are auxiliary wheels for conveying machine driving forces for lifting up or lowering down concrete or other heavy blocks;water / wind turbines, multiple pairs of gear-box couplers and two driving wheels are installed on a common shaft;multiple pairs of gear-box couplers couple the mechanic forces between the shaft of the machine and the common shaft;four guiding metal poles in each well through which concrete block’s holders move vertically;steel reinforced concrete foundation for supporting the machine system, water / wind turbines, direction-change tubes, connectors, water guides, metal poles;tunnels which lead to low platform from the docking areas located at the bottom of each well.

2. A system modified from the one as claimed in Claim 1, whereinthere is no gravity storage unit;the system is used either by itself or used for running as a motor to drive mechanic loads when there is no wind / water energy harnessing.

3. A system modified from the one as claimed in Claim 1, whereinthere is no water energy harnessing unit but the modified system contains wind energy harnessing and gravity storage units;the modified system runs in either of three possible modes alternately: wind energy harnessing, gravity storage and driving mechanic loads.

4. A method for operating the system as claimed in claim 1, which consists of the following operation modes:in the first operation mode, the belts for lifting up or lowering down the concrete or other blocks are de-coupled from the auxiliary wheels for starting the system to harness wind / water energy;in the second operation mode, the machine is controlled by its controller to draw power from a power system to run as a motor to drive mechanic loads; in this operation, the belt for the gravity storage stays de-coupled from the auxiliary wheels;in the third operation mode, the belts for lifting up or lowering down the concrete or other blocks are placed back to the auxiliary wheels for starting the system to fulfil conversion of energy between potential energy and electricity when there is no wind / water energy; operation from mode 1 to mode 3 alternates for different energy conversions.

5. A method for operating the system as claimed in claim 2, which consists of the operation modes as follows:in the first operation mode, the system is operated to harness water / wind and electric machine runs as a generator;in the second operation mode, the electric machine runs as a motor to drive mechanic loads when there is no wind / water energy to harness;operation from mode 1 to mode 2 alternates for different energy conversions.

6. A method for operating the system as claimed in claim 3, which consists of the following operation modes:in the first operation mode, the belts for lifting up or lowering down the concrete or other heavy blocks are de-coupled from the auxiliary wheels for starting the system to harness wind energy;in the second operation mode, the machine is controlled by its controller to draw power from a power system to run as a motor to drive mechanic loads; in this operation, the belt for the gravity storage stays de-coupled from the auxiliary wheels;in the third mode, the belts for lifting up or lowering down the concrete or other blocks are placed back to the auxiliary wheels for starting the system to fulfil conversion of energy between potential energy and electricity when there is no wind / water energy; operation from mode 1 to mode 3 alternates for different energy conversions.

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