The present invention relates to the field of renewable energy, specifically to a method and system that produces electric power utilizing sea energy.
There has been much research and practical attempts to utilize marine energy resources. Wave power devices are generally categorized by the method used to capture the energy of the waves. The main types are: point absorbers or buoys; surface following devices or attenuators oriented parallel to the direction of wave propagation; terminators, oriented perpendicular to the direction of wave propagation; oscillating water columns; and overtopping devices.
Existing technologies face serious challenges harming the cost-effectiveness. Among the challenges are included the following. The wave powered device has to efficiently convert wave motion into electricity. Generally speaking, wave power is available at low speed and high force, and the motion of forces is not in a single direction. Furthermore the potential impact on the marine environment is a concern. All this requires special engineering solutions to harness wave energy, leads to higher costs of the projects and badly affects the competitiveness of wave power generation.
Instead of wave powered devices, others have used submerged power generators.
US 2009/0302613 publication of Ullman discloses a method for generating power, having a step-by-step process of: (a) submerging a housing into a body of water, the housing defining a chamber therein; (b) maintaining the chamber at a pressure lower than the pressure exerted by the body of water on the housing; (c) admitting water from the body of water into the chamber and driving a turbine with the water flowing into the chamber to generate electric power; (d) discharging water from the chamber into the body of water; and (e) sequentially repeating steps (c) and (d).
The system described therein which performs this method requires a compressed gas source to discharge the waste water from the chamber. This requires additional energy input and furthermore leaves residue of discharge gas in the sea, which could be potentially harmful to marine environment.
U.S. Pat. No. 4,092,828 issued to Garza discloses a hydroelectric plant positioned on the bottom of the ocean floor and extending well above the ocean surface. A chamber on the ocean floor has openings that allow ocean water to be fed through channels to drive a turbine which in turn drives a generator to create power. The water that drives the turbine falls to a lower chamber. A piston adjacent to this lower chamber moves up and down in a hydraulic cylinder and discharges the used ocean water back into the ocean adjacent to the chamber on the ocean floor. The movement of the piston is controlled by a float at the ocean surface.
This float control system requires a complex set of lever arms and electronic controls at the surface to control the discharge piston. The entire structure also has a large expanse above the ocean surface which may have an environmental impact.
U.S. Pat. No. 7,188,471 issued to Walters discloses a submerged power plant chamber resting on the sea bed. The chamber has an intake valve for admitting high pressure water from the surrounding sea into the chamber. The incoming sea water rotates a turbine within the chamber and generates electricity. The sea water falls to the bottom of the chamber. A piston in the bottom of the chamber is moved up and down by a buoy on the sea surface and forces the sea water from the bottom of the chamber back into the sea.
GB Pub 2,428,071 of Shepherd discloses a hydroelectric power plant chamber positioned below the surface of a body of water. Water entering the chamber via ducts drives a turbine that generates electricity. The waste water passing through the turbine is then fed into waste tanks. Compressed air is then injected into these tanks and the waste water is forced back into the body of water.
None of the above references disclose the use of suction pumps at the surface of a body of water controlled by a buoy at the surface to remove water from their underwater chambers.
Also, none of the references disclose the ease of assembly and disassembly of their apparatus that permits both expansion or reduction of their facilities.
The present invention not only has the above capabilities, and uses no gas, as did two of the above references, and also has only one moving part below the sea namely a turbine. The latter capability means less maintenance problems than the prior art.
It is an object of the invention to improve wave power generation cost-efficiency and reduce the cost of power produced.
The invention advantageously provides a method and apparatus for generating power, which includes simultaneous processes of: (a) admitting water into underwater tanks, and driving a turbine with the water flowing into the tanks to generate electric power; and (b) discharging water from the underwater tanks to the surface of the body of water.
The invention advantageously provides a system of interconnected underwater tanks that provide the ability to use many buoy activated pumps associated with these tanks to harvest wave energy on a large area using only one or several large turbines.
The invention advantageously provides mechanical devices to discharge the water from the tanks.
The invention provides the following advantages: there is no need to build large structures some extending above the water surface or to use compressed air or gas as required by some prior art; it is possible and economically feasible to increase the capacity of the apparatus by adding onto the apparatus tank-by-tank; it is relatively easy and inexpensive to remove tanks or deconstruct the apparatus; there is no need to halt the operation of all the systems if a leakage or other technical problem occurs, or for regular maintenance.
The invention, when compared to the prior art, requires less hardware.
A power generation station, according to the invention has the following key elements: one or many interconnected underwater water-accumulating tanks; one or many turbines and generators; air conduits communicating the tanks with the atmosphere for pressure control in the tanks; and the pumps discharging the wastewater out of the tanks to the surface utilizing wave motion. Electricity generated is transmitted ashore by power lines.
A key part of the proposed construction is the system of hollow interconnected tanks, each interconnected to one another on the seabed. This system is located on a large area of the seabed or above the seabed, but below the water surface. The tanks have air conduits communicating the tanks with the atmosphere for pressure control in the tanks. The water from the sea is admitted into the tanks. The energy of the water coming into the tanks is used to produce electric power. The water is distributed among all interconnected tanks. According to the invention, simultaneously other key processes are being executed. In particular, the waste water in the tanks is being lifted onto the sea surface by piston or diaphragm pumps at the surface utilizing wave motion. Discharging the water out of the tanks frees the space for new volumes of incoming water, while simultaneously generating electric power, which will be described in detail hereinafter.
The apparatus and the method described above tackles major challenges of wave power generation, because it ensures the unbroken, regulated, and always one direction water flow coming through the turbine until the tanks are full.
Discharging the water out of the tanks utilizing the energy of waves becomes the main task and the challenge.
The invention will be better understood and further objects and advantages thereof will become more apparent from the ensuing detailed description of preferred embodiments taken in conjunction with the drawings, in which:
As shown in
The tanks 1 are sealed such that the only way the water can come into the tank system is through a channel 4 at the entrance to turbine tank T. Water coming in through the channel 4 causes the rotation of a turbine 5. The turbine is connected to a generator 6, enabling the hydraulic energy of water to be converted into rotational mechanical energy by the turbine 5, and the mechanical energy to be converted into electrical energy. Furthermore, the water coming into the first tank is being distributed among all the interconnected tanks 1 via the water collection area 1B at the rear of the turbine tank T. As the water becomes accumulated in the tanks T and 1 the water pushes the air out of the tanks T and 1 through air conduits 7 positioned in the tanks and positioned above at sea level by binding joists 10. The energy of the air being discharged through the conduits can be utilized as well, i.e. converted into electrical energy.
Understandably, the underwater tank system can be installed in different sizes and shapes. The size of an installation can vary from one or several tanks to massive concrete structures that can be parts of an artificial island. It is also possible to use natural caverns or hollow structures as water-accumulating tanks.
Note that
The pumps are located near sea surface in pump housings 18 which are mounted to the binding joists 10. Pump housings 18 together with additional ballast 14 and binding joists 10 allow keeping the pumps in the upright position. The group of the binding joists 10 is moored to the tanks 1 or another underwater structure by steel ropes 11, or in other suitable manners. In operation, air conduits 7 are mounted in one or more of the tanks 1B and 1 to keep them at atmospheric pressure and are extended above the sea surface and mounted to binding joist 10. Water pipes 8 are positioned in one or more of the tanks T and 1 and are extended above to connect to the pumps mounted in the pump housings 18. The pumps are operated by buoys 9 which have movements following wave motions.
There are also many different modifications, not shown in the drawings. Among them are using different types of the pumps, to be described hereinafter, maintaining higher or lower pressure in the tanks, and other modifications, subject to engineering solutions.
According to the invention, a number of subtypes of positive displacement pumps can be used.
When a wave rises up the buoy 9 rises with the wave which causes via the connection of the steel bars 33 the piston 16 to be pulled up, and consequently the diaphragm 31 expands upward, the volume of the chamber increases, the pressure decreases, and water is drawn into the chamber via an inlet valve not shown. Later, when the wave goes down, the diaphragm 31 deflates downward, for example, under the weight of the buoy 9 and the water is pushed out of the chamber 32 through the outlet valve 36.
Additionally, the buoy movement direction can be varied as an option.
Additionally, the buoy form can be varied as an option, wherein a body taking wave motion can be not only a buoy, but it can have different shapes as well.
Although the plate 20 described above is used with a diaphragm pump, a piston pump could also be used with the plate being attached to an angled piston pump to move the piston up and down.
Many other options of lifting the water with surface positive displacement pumps are possible.
The tanks can be submerged in the water only in part. In this case the top of the tanks is not needed, but maintaining a difference between sea level and water level in the tanks is essential. Taking into consideration that the tanks can exist in different size, it is possible to build a dam in the sea around a certain area, and use the inner area as a top-free tank. Suction pumps will be placed around the dam in this case.
There are many ways to assemble the offshore hydro power station shown in
According to one way, the first most challenging step is to install the turbine tank T which has two sections 1A and 1B as shown in
The second step is to assemble the water tanks 1. Just as the turbine tank T, the water tanks 1 are assembled on shore. The water pipes 8, buoys 9, pump housings 18, ballasts 14 and air conduits 7 are all preassembled to the tanks 1 onshore. It is also possible to assemble a set of interconnected tanks 1 on shore by adding water pipe couplings 3 and stopcocks between the tanks 1. These pipe couplings 3 connect with stopcocks 3A on the adjacent tanks 1. These assembled tanks are then pulled by ship to the desired location. When on location, water is added to the tanks to sink them. As the tanks sink, the pumps, the buoys, the ballasts and top parts of the water pipes and air pipes stay near the surface and become vertical. As with the turbine tank, cranes and other devices can be used to ensure undistorted sinking. It is relatively easy to move the tanks and correct the trajectory until the tanks are on the seabed. Pressure is high and the buoyant force is low because the tanks are on the seabed. Nevertheless, it is possible to moor the tanks. Temporary binding joist can be used to avoid splicing the pipes. They are easy to add and easy to remove by just putting them on the buoys.
The third and final steps are done by diver teams in this stage. However, it is not very difficult work because the depth is not high due to atmospheric pressure limitations for suction pumps.
First, everything on the seabed should be done. The diver teams connect all unconnected tanks 1 and open all stopcocks 3A among the tanks. A pipe coupling 3 connects one or more of the tanks 1 to the water collection area 1B of the turbine tank.
All outer gates 12 and outer stopcocks 3A remain closed. So the tanks 1 are filled with water, but sealed from the ocean.
Next work is done near the surface. As shown in
Another option for the whole process described above is to pin pump housings 18 and air conduits 7 to the binding joists 10 on shore and complete other steps needed.
The buoys 9 are then unpinned from the pump housing 18 and are allowed to move up and down along the pump housing 18. Water will now be pumped out of the water collection area 1B of the tank T and the tanks 1. At this time the turbine tank is double checked to see that everything is all right and that a power line from on shore is connected to the generator to transmit generated power to shore. All tanks are checked for leaks. The final step is to open the gates 12 of the turbine tank 1A and the system is in operation.
A second way to assemble the power station is to assemble all parts of the power station on shore, including the turbine tank and the attached tanks. The entire assembled power station would then be pulled by ship to the desired location and sunk. As the station is sinking the water pipes upper ends, air conduits upper ends, buoys and joists will remain near sea level.
Maintenance and repairs are an easy process. Also the system can be easily expanded by adding additional tanks 1 to the system.
If it is decided to end the operation, the entire system can be easily dismantled and removed.
The foregoing relates to preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.