Patent Application
20100283244
This disclosure relates generally to a power generation system. In particular, the disclosure relates to an energy system utilizing buoyant forces from a body of water to store energy, such as from wind energy.
World energy demand is growing, particularly for energy sources that are renewable and emit less carbon into the atmosphere. Consequently, wind energy captured through the use of wind turbines is rapidly expanding as one available means to fulfill energy demand. Moreover, wind turbines are increasingly located in bodies of water (“off-shore”). Locating a wind turbine off-shore may use favorable winds that can occur over a body of water. In addition, land constraints and other factors, such as aesthetic concerns and government regulation, may make it advantageous to locate a wind turbine off-shore instead of on land.
However, despite considerable recent advances in wind energy technology, wind energy still has certain drawbacks. First, because the wind is intermittent, the energy produced by a wind turbine may be variable and uncertain. Second, demand for energy is also variable. If there is insufficient demand for the energy produced by a wind turbine at any particular moment in time, then the energy produced by that turbine from available wind forces is lost. Means exist to store excess energy, such as batteries; however there is transmission loss in power lines from off-shore turbines to energy storage devices, as well as increased cost.
Various systems have attempted to take advantage of the placement of a wind turbine in a body of water. For example, U.S. Pat. No. 4,266,403 to Hirbod (“Hirbod”) discloses an apparatus to harvest both wind and wave energy. Specifically, Hirbod discloses an apparatus with a first housing held at a fixed height above the bottom of a body of water and having an internal cavity, and a buoyant second housing having an internal cavity surrounded by sleeves. The walls of the internal cavity of the first housing are slidably contained for allowing relative movement between the first and second housings in response to wave action. However, Hirbod does not disclose an energy storage system for harvesting energy for later use. Prior art devices such as those disclosed in Hirbod do not overcome intermittency problems of wind energy discussed above.
The present disclosure is directed to overcoming or mitigating one or more of the problems set forth above.
In one aspect of the disclosure, an energy generation and storage apparatus is provided. The apparatus has a power generation assembly and an energy storage assembly operably coupled to the generator assembly. The energy storage assembly has at least one buoyant device, and is configured to store energy by lowering the buoyant device to a lower depth of water. The energy storage assembly is also configured to release energy by allowing the buoyant device to rise to a higher depth of water.
In another aspect of the disclosure, a method of storing power is disclosed. The method includes the step of lowering a buoyant device to a first depth of water. The method also includes the step of permitting the buoyant device to rise to a second depth of water; and the further step of converting the buoyant force acting on the buoyant device into electricity as the buoyant device rises to the second depth of water.
In another embodiment of the disclosure, an energy storage apparatus is disclosed. The energy storage apparatus includes a power generation assembly and an energy storage assembly operably coupled to the power generation assembly. The energy storage assembly has a buoyant device, a cable, a pulley, and a spool. The energy storage assembly stores energy by lowering the buoyant device to a lower depth of water and releases energy by allowing the buoyant device to rise to a higher depth of water.
As shown in
Power system 100 also includes energy storage assembly 120, which, in the embodiment shown in
Each buoyant device 126 in energy storage assembly 120 may include a pressure vessel or any suitable structure that exerts an upward force on cables 124. For example, buoyant device 126 might be constructed of a hollow container that would float on water when subjected to no other artificial forces. Buoyant device 126 need not be hollow, however. A structure is suitable as long as a buoyant force is created by a pressure difference between water at the top and bottom of the buoyant device 126.
Pulleys 128 attached to the sea floor act to ensure that the force transmitted on buoyant devices 126 from cables 124 is mostly or entirely in a plane perpendicular to the surface of the water. As used herein, a “higher” depth of water means a depth of water closer to the surface of the water, and a “lower” depth of water means a depth of farther below the surface of the water.
It should be noted that embodiments according to the present disclosure are sufficiently adaptable to a variety of situations. Power system 100 may be located in any body of water suitable for common wind turbines, such as a lake or ocean. Moreover, any number and size of buoyant devices 126 may be used.
Further, although in the embodiment of
In this embodiment, energy storage assembly 220 includes a spool 222 mounted above water about turbine support 214. Spool 222 may rotate as blades 212 turn from wind forces, or spool 222 may be disengaged from rotating with blades 212 by using known means such as a clutch. Cables 224 wrap around spool 222 and connect to buoyant devices 226 via one or more pulleys 228 near base 216 at the sea floor.
In this embodiment, an attachment member 230 connects buoyant devices 226, which acts to at least partially constrain the lateral range of motion of each buoyant device 226. In this configuration, multiple buoyant devices 226 may be affixed at or near turbine support 214 in an annular fashion around the diameter of turbine support 214. This may be helpful if it is necessary to constrain the lateral movement of buoyant devices 226.
The present disclosure provides an advantageous apparatus and method to efficiently produce and store energy from wind power. In operation, and returning to
Various control parameters may be utilized to optimally control operation of power system 100. For example, a remote signal may be sent to power system 100 to engage the energy storage assembly 120, and thereby divert at least a portion of the wind force energy to lower the buoyant devices 126 when there is insufficient demand from external sources for the energy produced by power system 100. Therefore, one control parameter may be immediate energy demand. Another potential control parameter may be the spot price of electricity in the energy markets. If the current spot price falls below a specified threshold, the energy storage assembly 120 may be engaged to store energy for release when the price exceeds a threshold amount. Power system 100 may be used, therefore, to generate power during off-peak hours for storage and later release during peak energy demand times.
Alternatively, and still referring to
Additionally, it can be seen that the total energy storage capacity of the power system 100 is smaller in shallower water. However, the overall energy storage capacity of the system may be increased by increasing the number of buoyant devices 126 in the system and/or by increasing the volume of each buoyant device 126, thereby increasing the total buoyant force exerted when the buoyant devices 126 are allowed to rise towards the surface of the water. In this fashion, multiple buoyant devices 126 could be attached in series and/or in parallel along each cable 124 to increase the total volume of water displaced, and thereby increase the total amount of energy storage capacity in energy storage assembly 120.
In addition, buoyant devices 126 need not be raised completely to the surface of the water, nor be lowered entirely to the sea floor, if the location of power system 100 does not permit it due to terrain, weather conditions, or other factors. The overall length of cables 124 may be adjusted to permit the desired range of motion of buoyant devices 126.
Other embodiments, features, aspects, and principles of the disclosed examples will be apparent to those skilled in the art and may be implemented in various environments and systems.
