Natural Energy Processing Company (NEPC) was started with water pumping wind mills and aerogenerators in the year 1986.
NEPC India is a public company promoted by the Khemka Group with the primary objective of promoting wind energy. This successful group has a multi crore turnover from diversified activities in the field of power generation from wind energy and manufacture and marketing of wind turbine generator (a renewable energy device).
The NEPC group, born out of the vision of Ravi Prakash Khemka, chairman of the group, and the driving spirit behind every endeavor, making it a practical success.
NEPC India - The pioneers in harnessing wind energy, has installed over 2500 Wind mills of different capacities totaling to more than 548 MW in India . The company also has set up demonstration wind farms in various wind-prone states in India .
Now, the company has diversified into manufacturing solar technology compatible power systems- Inverters / UPS of various capacities available with or without solar panels. Through collaborative research and development work carried out within the frame work of the company for the photovoltaic power systems, they have also entered into thin film solar module manufacturing at the capacity of 250MW which will be set up in a phased manner.
Product range of the company includes:
Tower- The commonly used tower in the present proposal is tubular tower which has a door at the bottom. The door can be used to enter into the tower for operation and maintenance. The door is usually provided with locking arrangement to prevent unauthorised entry of outsiders. All the towers are provided with ladder to climb up to the top so as to do the maintenance. In these towers at certain intervals, platforms are fitted inside the tower for inspection of joints of the tower section.
Blades- The turbines are provided with three blades. The blades are self supporting in nature made up of fibre reinforced polyester. The blades are mounted on the hub. The blades are built with aerodynamic brakes that prevent over speed of the wing.
Nacelle- The Nacelle is the one which contains all the major parts of a turbine. The nacelle is made up of thick rugged steel and mounted on a heavy slewing ring. Under normal operating conditions the nacelle would be facing the upstream wind direction.The nacelle is fitted with a cover to protect the parts from climatic damages.
Hub - The Hub is intermediate assembly between the wing and the main shaft of the turbine. Inside the hub, a system to actuate the aerodynamic brake is fitted. The hub is covered with nose cone.
Main Shaft- The shaft is to connect the gear box and the hub. Solid high carbon steel bars or cylinders are used as main shaft. The shaft is supported by two bearings.
Main Bearing -The main bearings are placed inside housing. The main bearings are usually roller bearings. The bearing house has the provision to fit temperature sensors and has the facility to apply lubrication.
Gear Box - The gearbox is used to increase the speed ratio so that the rotor speed is increased to the rated generator speed. The helical gears are used in the gearbox. Oil cooling is employed to control the heating of the gearbox. Gearboxes are mounted over dampers to minimise vibration.
Brake- Brake is employed in the Wind Turbines to stop the turbine mainly for maintenance check. Brakes are also applied during over speed conditions of the turbine.The brakes are placed on the high speed shaft. There are different types of brakes used in Wind Turbines. But Hydro-spring pressure disc brakes are widely used. During the operation of the turbine the brake system is active and keeps the brakes in released condition. For this purpose, electrical power is used to pressurise the hydraulic oil or hold the spring in compressed state. Once the power falls, the brakes are applied. Hence during braking, the control system cuts off the electrical continuity to brake the system.
Yaw System- The Yaw Ring is fitted at the top of the tower over which the nacelle is seated. The nacelle is able to rotate 360 deg. around the yaw ring. The yaw ring is fabricated in such a way that it allows the nacelle to rotate freely but prevents lifting up from the tower. The yaw gear is in contact with yaw ring. The rotation of the yaw gear turns the nacelle to the desired direction. The yaw gear is coupled with an electric motor called yaw motor. Single or double yaw gear is used to operate the yaw ring. Yaw brakes are used to keep the nacelle in a steady position when it is not yawing. During yawing the nacelle is able to rotate smoothly. The yaw brake has brake liners loaded by springs, which act as brakes. While yawing the yaw gear overcomes the braking force of the yaw brake.
Coupling- Couplings are fabricated with rubber elements over metallic shaft to reduce the strain and vibration due to error in the alignments.
Generator- The generator invariably uses induction type of generator depending upon the RPM selection. For better efficiency two generators with different cu-in wind speed requirements are mounted on the same shaft. The generators are provided with monitoring sensors in each phase winding to prevent damage to the generators.
Sensor- Different sensors are used in turbines for monitoring.
They are as listed below :
a. Anemometer - to measure the wind speed.b. Wind Vane - to sense the wind directionc. Tacho rotor sensor - to measure the rotor RPM.d. Tacho gen. sensor - to measure the generator RPMe. Yaw sensor - to measure the yawing angle of the nacellef. Vibration sensor - to sense the vibration of the towerg. Twisted cable sensor - to feel the twist in the power cable of the generator.h. Temperature sensors - to measure the temperature of main bearing, gear oil, generation winding etc.
Power Panel- The power panel is equipped with number of contractors, auxiliary contactors, thermo relays, soft components, phase compensation batteries and circuit braker etc. The contactors are used to connect and disconnect the generator, yaw motor, hydraulic pump motor and brake magnetic coil, etc. The auxiliary contacts used to feed information to the control system about the status of different contactors and components. Thermo relays are used as protection to the motors used in the turbines. Soft cu-in components are either thyristers or heaters controlled by suitable module. Phase compensation batteries are the capacitors used to reduce the reactive power consumption of the turbines.
The circuit breakers used at the incoming side of the panel is to protect the electrical systems of the turbines from damage on fault conditions and also used to shut down and attend servicing on the electrical system.
Control Panel- Micro processor based control circuits are provided in this panel. It receives input signals from the sensors and auxiliary contacts of the power panel and sends output signals to different contactors to on/off the related systems as per the programme fed into the micro processor. It has a display module, which displays instantaneous records of power produced, wind speed, grid instantaneous records of power produced, wind speed, grid voltage/current, fault status and so on. A programmable key board facility is available in the micro processor system to feed the set parameters and see different datas logged in the control processor.