This present invention relates to the construction of a foundation for a wind turbine tower of industrial wind power plants which are constructed on onshore or nearshore with low water level, and particularly to the foundation for turbines with tower of steel or cylindrical concrete with capacity ranging from 1 MW to 10 MW or larger in the future.

Background of the invention

Now, with climate change and the development of science and technology, the development of renewable energy plants is an indispensable need, especially industrial wind-power plants. Typically, wind turbines consist of the generator (rotor and stator), tower, and foundation. Common wind turbine tower foundations include the following types:

Shallow foundation: The shallow foundation is usually built in the place where the ground at a depth of about 3 to 4 meters has a good load capacity. The common shallow foundations for wind turbines usually consist of two components, the foundation slab and the pedestal. The foundation slab is usually in thick round shape form of circular or polygon with an average thickness ranging from 2.0 meters to 4 meters. The pedestal has a embeded anchor system that allows the link of the tower and the foundation in the form of circular or polygon with an average height of 3.0 meters to 4.0 meters and diameter about 6.0 meters.

Pile foundation: Pile foundations are built on the ground with poor surface load capacity, on which the shallow foundation solution cannot be used. The pile cap of the pile foundation has the same shape and structure as that of the shallow foundation and is connected to the pile system to transmit force from the foundation to the good ground below the soft soil layer. The foundation structure for the wind turbine ensures the transmission of compressive force, shear force and bending moment into good soil layer, and ensures good operating conditions in static, dynamic and fatigue states as well as meets the requirements of the wind turbine manufacturers. The torque component caused by the wind is very large. Conventional foundation structures use the foundation slab as a bending plate to transfer the torque caused by the wind to the ground, therefore the foundation slab will bear a great torque and cutting force that requires a large plate thickness. The shape of the said turbine foundations is not the optimal structural shape to take full advantage of good compressive concrete materials and tensile steel.

With the current size, common foundations (or pile cap with pile foundations) have a volume of about 600 m ³ of concrete. Today with higher and higher capacity wind turbines, the above types of foundation will be in big size with a volume up to more than 1000 m ³ of concrete and even more. Therefore, the construction and control of construction quality is very difficult, construction costs are high leading to high total investment costs and reducing feasibility. This is the main disadvantage of common concrete foundations. The reasons are:

Concrete pouring should comply with the standards of mass concrete construction due to the large thickness and large volume of foundation;

Large volume of concrete and volume of reinforcement steel leads to high construction costs;

In difficult transportation areas, the larger the construction volume, the higher the cost and the longer construction time.

Therefore, it is necessary to have appropriate design solutions to reduce the material volume and construction time.

Summary of the invention The objective of the present invention is to provide the foundation of wind turbine tower to overcome the problems that exist in technical solutions as described above.

In the main aspect, the present invention provides a method of designing, manufacturing and constructing industrial wind power turbine foundation to take advantage of existing design and construction advantages, and overcome disadvantages of traditional methods to save costs, control quality and accelerate construction progress.

The present invention provides a foundation for the wind turbine tower in the form of cylindrical or a circular rotating prisms with an inverted V-shaped cross section (A). In addition, the present invention provides a method for constructing the foundation for the wind turbine tower for wind power conduction built in locations with different geological conditions.

The present invention provides the foundation for the wind turbine tower v

with a cylinder shape (as shown in Fig. 1) or a n-sided regular polygon prism (n > 3) (as shown in Fig. 2) with an inverted V-shaped cross section (L) (as shown in Fig. 3). With this foundation shape, the invention’s solution allows to make the most of the capabilities of wind turbine tower’s foundation materials. According to this invention, the foundation allows to transmit the load and transform the working principle from the main bending moment component to the main compression-tension force component by taking advantage of the space arch effect by adjusting the slope angle and wall thickness of the hollow cone block (4). Because the main internal force acting on the structure is the compression-tension force in the hollow cone block (4), the thickness of the hollow cone block (4) does not need to be thick but still ensures the bearing capacity. Towers are linked to the foundation by the anchor bolts (6) embeded in the pedestal (3). The internal force from the tower is converted into internal compression-tension force in the hollow cone block (4) by the arch effect and the thin wall structure. The smaller the arch height, the more the internal force tends to shift to bending moments and vice versa. So the structure of the foundation has an inclination suitable for the horizontal plane to best optimize the bending moment component in the foundation structure. The entire internal force of the hollow cone block (4) will be transmitted to the ground in the case of shallow foundation or through the annular ring (5) in the case of pile foundation. The annular ring has a tendency to extend away from the foundation center to make the most of the area with high stress, unlike the conventional foundation with a large contact area but the inner part of the near-by foundation center is less resistant. In addition, the annular ring also allows to add a lot of weight of backfill soil to stabilize the foundation.

The foundation is built according to two methods, namely the cast-in- place method and the semi-assembled or assembled method.

The present invention’s solution is suitable for all specific conditions at the construction site with many advantages.

The solution allows to reduce the amount of concrete and steel materials because the backfill soil has been used instead of a part of concrete to make gravity and allows to reduce costs.

The solution allows to reduce complexity due to the strict requirements of large, high-volume concrete pouring as in common designs.

The solution is suitable for all construction methods such as the cast-inplace method and the precast method.

The solution allows to reduce construction time by reducing the amount of materials used. From the comparison of the present invention’s solutions, the estimated volume of materials can be reduced by 20 to 30% that lead to the reduction of the construction costs.

Brief description of the drawings

Fig. 1 is a partial perspective drawing of a foundation for a wind turbine tower of the present invention with a cylindrical form on the ground;

Fig. 2 is a partial perspective drawing of the foundation for the wind turbine tower of the present invention with a prism form on the pile; and

Fig. 3 is a cross-section showing the foundation in an inverted V-shape (A) consisting of a pedestal (3) that connects the tower to the foundation, a solid or hollow cylinder that allows the installation of electric cable systems, the upper part of the pedestal linked to a metal working platform (10) to allow the installation of electrical systems for turbines; a hollow cone block (4) with truncated or polygon-shaped cones, the generatrix of the lower and upper surface of the hollow cone block can be a straight line or a combination of zigzag and curves, the wall thickness can be variable; the pedestal (3) and an annular ring (5) are linked by the hollow cone block (4) that creates an arch effect. The annular ring (5) has a ring shape with a variable thickness to allow the transmission of the load from the foundation into the ground (7) in the case of shallow foundation or through the pile system (8) in the case of pile foundation.

Detail description of the invention

The present invention provides a foundation for a wind turbine tower in the form of cylindrical shape as shown in Fig. 1 or a n-sided regular polygon prism shape as shown in Fig. 2 with an inverted V-shaped cross section (L) as shown in Fig. 3. The structure of the foundation consists of a pedestal 3, a hollow cone block 4, and an annular ring 5. The pedestal 3 is the structure connecting the tower and the foundation structure to allow the transmission of the load from the tower base to the foundation. The pedestal 3 may be of a cylindrical or polygonal shape, which may be solid or hollow in the middle as shown in Fig. 1 to place the equipment on the foundation if necessary. The top surface of the pedestal 3 is linked to the working platform 10 allowing the installation of operating equipment for wind turbines. The size of the pedestal 3 may vary depending on the specific design.

The hollow cone block 4 is the structure that transmits force from the pedestal 3 to the the annular ring. The hollow cone block 4 has a rounded circular conical shape or a regular polygonal trapezoidal shape. It has a reasonable slope and thickness to optimize and maximize the ability of concrete and reinforcement stelel by creating a space arch effect and a shell structure to convert from the moment to main compression-tensional moment. The generatrix of the upper and lower sides of the hollow cone block 4 can be straight, curved or zigzag. The size of the hollow cone block 4 may vary depending on the specific design.

The annular ring 5 is the transmission structure from the hollow cone block 4 to the ground or pile system. The annular ring 5 has a ring shape with the thickness can be changed to allow the transfer of the load from the annular ring 5 to the ground or the pile system in case of weak soil. In addition, the annular ring 5 also has another important function that it can extend away from the center of the foundation to allow additional gravity to create stability for the turbine foundation by taking advantage of the backfill soil and at the same time taking advantage of maximum area under high stress, different from the normal type of foundation with large contact area but the inner part of the foundation center is less resistant.

The size of the annular ring 5 may change in the specific conditions. The shape of the foundation according to the present invention, allows to save 20 to 30% of the volume of materials as compared to traditional foundation in the prior art.

Advantageous effects of the invention

The present invention has advantageous effects that:

Create a reasonable foundation structure, make the most of the capacity of the constituent material, transfer the main internal force from bending moment and cutting force in the foundation to the main internal force of main compression-tensional force, due to the relatively small torque in the the hollow cone block model (see Figs. 1 to 3). Due to the main internal force acting on the structure is the compression-tension force in the hollow cone block, the hollow cone block does not need to be thick but still ensures the bearing capacity.

At the same time, the annular ring tends to extend away from the foundation center to make the most of the area of high stress, unlike the normal foundation with large contact area but the inner part of the foundation center is less resistant.

In addition, the shape of the foundation according to the present invention, allows saving and eliminating the volume of excess non-bearing capacity materials to reduce cost. Therefore, the further advantageous effects of the present invention include:

Reducing concrete and steel materials thanks to a part of concrete to make gravity has been replaced by backfill soil. This reduces costs of the foundation;

Reducing the complexity due to the strict requirements of large concrete pouring with a large thickness of traditional foundation in the prior art;

Suitable for all construction methods such as prefabricated construction or cast-in-place; Allow to reduce construction time by reducing many materials used;

The middle hollow part of the foundation allows easy installation of turbine equipment systems;

The cost of foundation decreases due to the combination of the above factors.

Although above detailed description only specifies the feasible embodiments of the present invention, many changes and variations can be made basing on the principle of the present invention. These changes and variations are covered in the scope of protection of the present application.