PRIOR ART

Energy generation techniques that have been popular so far are facing an enormous challenge due mainly to the increase in carbon emission in the environment. This has promoted the development of green energy which is now-a-days achieved through many ways like solar, wind, tidal etc. In all these practices pollution free energy is produced but there are some major draw backs in them. Major obstacle has been the economic feasibility of these methods increasingly more and more efficient techniques are introduced to these modes of power generation. Wind mills have been in existence for more than a century. They were replaced by other economical technologies in the past. With the newer techniques being introduced, wind mills have become more widespread in the recent past increasingly they have become bigger and better in the past there have been many attempts to increase the efficiency and also enable the energy tapping at low wind speeds.

US 8747070 B2 discloses horizontal axis wind turbine in which the blades can simultaneously rotate in a vertical axis and a horizontal axis when subjected to a wind.

US 20160208772 A1 discloses a propeller type wind turbine for low wind speeds. A counterweight is attached to balance the forces developed, and the blades rotate in a plane parallel to the main rotor.

CA 2354686 A1 discloses horizontal axis wind turbine with bucket type blades designed to operate under low wind velocities. It includes a horizontal turntable frame mounted for rotation on a vertical axis. A wind rotor is fixed to the rotatable shaft and includes at least four pairs of oppositely disposed arms radiating outwardly from the rotatable shaft with one or two concave surfaced wind catching bucket mounted across between each pair of arms. US 20110081243 A1 discloses helical airfoil wind turbine and claims to be an improved wind energy generator. This invention is a wind turbine that utilizes lightweight airfoils in unique designs.

US 20070177977 A1 discloses a horizontal multi-blade wind turbine. A blade system has a plurality of blades supported in rows along the length and having a blade axis extending radially and each row being spaced around the circumference of a rotor of a wind turbine which is particularly suited for use in remote locations.

IN201721004140 discloses a horizontal axis wind turbine consisting of smaller, sturdier and faster blades having fixed airfoil shape and mounted on fixed shaft as stator and a set of moving blades mounted on a moving shaft.

The present invention is capable of overcoming many of the disadvantages in the systems in prior art. It has a very low speed threshold for operation. Having a twin turbine setup gives a substantial increase in efficiency.

The newly invented blade system described here will be used in each horizontal axis wind turbine. In the prior art wind mills of this type, the blades or wind facing elements catch the wind and transforms that energy into the rotating motion while the blades opposite to the wind create a resistance. Because of this, energy is lost by a few percentage. The present invention addresses such drawbacks and deficiencies of the prior art solutions.

SUMMARY OF THE INVENTION

The present invention discloses a twin turbine system where the two turbines are mounted on a horizontal axis. This axel is free to rotate about a vertical axis at its midpoint. The two turbines mounted on the two sides of the axel provide a gravitational balance. The bucket shaped blade comprises a set of louvers. These louvers can rotate about one of the longitudinal edges. The position of each louver is determined by a tie-rod, the movement of which is guided by a cam and a cam follower mechanism. The cam is rigidly fixed to the axle and rotates with it. When a blade is above the axle level, the louvers are in the closed position. The louvers form a bucket and catches the full effect of the on-coming wind. When the blade moves downwards, the louvers are opened using the tie-rod. This ensures that the louvers of the blades are not resisted by the wind as the wind passes through freely.

NOMENCLATURE

BRIEF DESCRIPTION OF FIGURES

Figure 1 Wind mill with horizontally curved blades (showing the complete assembly) Figure 2 Working mechanism of louvers (Illustration showing four blades)

Figure 3 Cam mechanism for louver operation (showing only two blades) DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION

The present invention is a twin turbine windmill mounted on a single horizontal axle (3). The axle is supported at its midpoint on a tower sufficiently high to face the wind blowing in the atmosphere. In the present embodiment, a range of the height can be above 50m going up to 100m. The axle is firmly mounted on a bearing assembly (2) at the top of the tower (1). The axle passes through a bearing assembly (2) comprising the nacelle, and the two turbines will balance their weight as they are equally spaced from the midpoint of the axle(3). In the present embodiment, each turbine has four blades. Each blade comprises two side pates (11) rigidly coupled with a solid frame. A number of louvers (13,14) are placed between the two side plates (11). The louvers can rotate about a longitudinal edge (15) so that they can be opened or closed when needed. The louvers have a slight overlap so that when they are closed, there is no leakage of air through. When the louvers are opened, air can freely pass through.

A yaw mechanism of prior art is used to command axle of the turbine operating system to rotate in such a direction that the blades face the maximum wind velocity direction. As a result the extraction of output power from the turbine is maximized. The set of louvers is connected to each other using a tie-rod (22). The movement of the tie-rod is regulated by a cam follower (24) which moves based on the angular position of the cam (23) keyed to the horizontal axle (3). The cam system is so designed to ensure that the louver opening is limited to 90 degrees. For a major part of the revolution, the louvers are in the closed position (26). The cam system will open the louvers during part of the rotation. This is normally done when the blade is in the lower sector of rotation (25). This ensures that there is no resistance to the wind flow when the blade is in the non-active sector. This results in the maximum power output from the turbine. Similar mechanism for louvers could be installed in the turbine to keep all the louvers in the open position for some locations where excessive wind speeds are experienced.

Naturally other attachments like instrument to detect wind direction to get the best yaw and for safety precautions and attachments like braking mechanisms and lightning arresters, are fixed to the total windmill complex, but which are not parts of the invention.