Multi stage wind turbine - DIY

CONSTRUCTION DETAILS OF EACH STAGE

It includes construction of one conical lift device three leaf blade horizontal axis wind rotors. These are explained below,

Construction of conical lift device:

At first sheet metal strips are fastened over the surface of hollow cone element using rivet. Then the hub which holds the device at the beginning of the shaft is inserted into the inner side of the device. The metal plates are used to connect the hub with conical lift device.

Table: Specification of conical lift device

Length
Larger diameter	155
Smaller diameter	15
Metal blade thickness	0.2
Tapper of blades	(1-3”)
No of blades	10

Construction of wind blades from PVC pipes and hub:

At first take PVC with particular length depending upon the diameter of the pipe. The length of pipe will be 5 times of its diameter (for example 8” pipe length must be 40”). The conical lift device hub is coupled with the shaft through the hub’s bush. The beginning 30cm of the 2.1m shaft are occupied by the conical device.

Fig PVC pipe cuttings

Divide the pipe into 6 equal parts by the angle 60 deg longitudinally. Then cut these rectangle shaped pieces into tapered blade shape.

Fig : Angle of cutting

Remove the excess materials from the blades by cutting the materials from the PVC to form a perfect blade. The edges of the blades are machined to form a shape of aerofoil.

Fig : Hub

Then make two holes to fastening the blades with respective hubs.

Fig : Final shape of blade

Construction details of leaf blade rotors.

First stage:

The specifications of the last three stages are explained below in table. The blades are first fastened with extension plate for the purpose of increasing the rotor diameter and also make the blades to receive the fresh wind.

Fig : Fixing of blades with hub

Fig : First stage rotor

Table : First stage specifications

No of blades	6
Length of extending plate	0.03m
Length of blade	0.67m
Diameter of hub	0.16m
Distance from beginning stage	0.20m

Second stage:

The second stage preparation is same as that of the first stage. The only differences between these two stages are by its length of blade. The second stage rotor blades are from 6” pipe.
Fig : Second stage rotor


Table : Second stage specification

No of blades	6
Length of extending plate	0.035m
Length of blade	0.100m
Diameter of hub	0.20m
Distance from beginning stage	0.75m

Third stage:

The third stage contains 12 blades each blade is made from 8” PVC pipe. The construction of the third stage is same as that of the last two stages

Fig: Third stage rotor

Table 7.3.3: Third stage specification

No of blades	12
Length of extending plate	0.04m
Length of blade	0.150m
Diameter of hub	0.20m
Distance from beginning stage	0.85m

WORKING PRINCIPLE FOR WIND TURBINES:

When an airfoil-shaped body moved through a fluid produces an aerodynamic force due to the Bernoulli’s principle (the pressure of air at lower end is higher than top surface). The component of this force perpendicular to the direction of motion is called lift. This lift force is only responsible for rotation of the wind turbine.

Fig : Working principle of wind turbine

In PVC wind blades the cross are made as aerofoil to convert the velocity of wind into mechanical rotary motion.

PRINCIPLE BEHIND MULTISTAGE WIND TURBINE:

The principle for the multistage wind turbine is the modification from the principle of multi rotor wind turbine. Our new multistage principle increases the no of rotors in a single rotating shaft for the purpose of increasing the speed of the rotor and also the power. The principle for multistage wind turbine is explained below.

Principle for multi-rotor wind turbine:

By the principle of Bertz there is nothing possibility to built a multi rotor wind turbines at      series in horizontal position. It’s only material waste.

But at the same time from the principle of Doug Selsam by increase the angle of shaft ( horizontal to +ve angles)  (or) inclined the angle position there is some chances to built a multi rotor wind turbines by giving  wind to all rotors. From this we will construct a multi stage wind turbine.

Fig : Working principle of multistage wind turbine

Principle for multi-rotor wind turbine:

From the Selsam’s multi-rotor wind turbine principle, in our multi stage wind turbine we just use various diameter rotors in a single rotating shaft by increasing the distance between the rotors and we use a new type of double plate tail for conical lift device to receive air flow first.

We also inclined the rotating shaft for the purpose of receiving the fresh air for each stage. The diagram below shows the principle for multi-rotor wind turbine.

Fig : Principle for multistage wind turbine

WORKING OF CONICAL LIFT DEVICE:

When the air flows in-between the two blades horizontally then there is a pressure difference is produced due to the shape of the blades. By the application of Bernoulli's theorem the total device is moved to the low pressure side (clock wise from front). At the bigger side of the cone the air was completely blocked by the bending blades. This makes more pressure differences to turn device at slow wind speeds.  

Fig : Working of conical lift device

The conical lift device works as an initiator in the multi stage wind turbine. The cut in speed for the conical lift device will be 3.8m/s. that help to speed up the turbine at low wind speed.

CONSTRUCTION DETAILS

The construction of the multistage wind turbine consists of three major parts, these are explained below.

• Supporting unit.
• Rotor and tail unit.
• Transmission unit.

SUPPORTING UNIT:

The supporting unit consists of supporting c –channels with inclined positions by the principle of multistage wind turbine. The supporting columns are not equal and also they are not perpendicular with the bottom horizontal channel. The value of angle for the rotating shaft is given as 10 deg; by this we designed the angular positions of the supporting columns. The dimensions and positions of the supporting columns are explained in diagram below.

The total supporting column sets are fitted over the thrust bearing which is in the top of the supporting tower. The total top weight of the upper supporting setup was loaded over the thrust bearing using the iron rod.

Fig : Supporting unit


ROTOR AND TAIL UNIT:

Each rotor are situated in the 2meter length shaft with some space interval them, with respect to the diameter of the rotor. For larger diameter rotor requires more space interval from the beginning rotor. By the new principle of multistage wind turbine these rotors are situated with different space intervals.

Fig 12.2 (a): Rotor and tail in turbine

The twin tail helps to turn the turbine to face the wind and also for conical lift device to receive the air first for the purpose increase the output power of the turbine.

Fig : View of tail from top


POWER TRANSMISSION UNIT:

Belt type power transmission is the cheapest power production system, with optimum efficiency. There is one larger pulley is fixed at the end of the shaft to transfer the power to smaller pulley which is fixed at the rotor’s alternator. The specifications of the belt drive transmission system are given below.

Type of the belt                                = v- belt
Larger pulley diameter                     = 254mm
Smaller pulley diameter                    = 5.08mm
Length of belt                                    = 3200.4mm
Material of the pulley                        = cast iron


Fig : Power transmission unit

WORKING OF MULTI STGE WIND TURBINE

When the air first hits the conical lift device then turbine starts rotating. That lift device helps to rotate the turbine. After the sufficient torque for the turbine are offered by another three stages in the unit. Fresh air is entered into the each stage for achieving maximum torque.

Then that torque was transmitted to the alternator by using belt drive transmission system. Considering the distance between the rotor shaft and the alternator we use belt drive for power transmission.

The alternator that helps to transfers the mechanical torque into electrical power. The tail that helps to turn the turbine to face the maximum wind power by receive wind conical lift device first.

POWER OUTPUT

S.NO	STAGES	RPM	WIND SPEED              (m/s)	OUTPUT POWER  (w)
1	Conical lift device only	105	4.5	4.3
2	Conical lift device and first stage rotor	85	4.5	7.5
3	Conical lift device, first stage rotor and second stage rotor	52	4.5	12.6
4	Conical lift device, first stage rotor, second stage rotor and third stage rotor	39	4.5	16

At 12.5 m/s the output power will be more than 300 watts. We expect 50 watts at 4.5m/s but due to belt drive transmission and poor alternator reduces the power.

ADVANTAGES

• Alternate power generating unit.

• Cost effective then compared to other single stage turbines.

• Easy installation.

• Medium power production is possible up to 10KW.

• Maintenance cost is low.

• Cut in speed is 3.8m/s, at lower wind speed maximum power is possible.

• Non- polluting.

• Space occupied by the multistage wind turbine is lower compared to single stage wind turbines.

DISADVANTAGES

• Technical person is required for construction.

• Higher fixing cares to be taken avoid accident due to heavy wind flow.

• Additional power pack unit required for storing power in day time and use the power in night times.

• Proper rectifier is required for charging the battery.

Increase the power of the turbine by using super alternator and use light weight material like carbon fiber. By using the light weight materials to blades and also rotating shaft we can add more rotors to increase the power. Add furling units and better gear drive transmission system for better efficiency. Give better design for rotating the turbine to face the wind depending upon the flow direction. 

- Work done by arjun [selvaarjunanpts@gmail.com]