Wind Energy

Introduction
Wind results from air in motion which arises from a pressure gradient.  a) To the absorption of solar energy on the earth’s surface and in the atmosphere.  b) Due to the rotation of f earth about its axis and its motion around the sun.

Winds are created a) Due to unequal arborvitaes f land and water and thermal time constant.  b) Due to hills and mountains.

Frictional effects between the moving air and earth’s rough surface and mountains trees and buildings are the major factors that weaken the stream line airflow.

Historically wind energy was used for sailing ship, grinding grain and pumping water. 

7. Advantages of wind Energy:-
(a) Free source of Energy
(b) Pollution free and its source of energy is free.
(c) It is a renewable source of energy.
(d) Its potential as a source of power is reasonably good. Estimated energy
     overall earth surface is 1.6*107mw.
(e) Wind energy systems avoid fuel provision and transport

8. Limitations or disadvantages of wind energy
(a) Wind energy is uncertain & irregular, unsteady and often not reliable.
(b) It is a dilute form of energy and needs storage capacity.
(c) Wind energy systems are noisy in operation.
(d) Large area is needed.

 

Wind as a Renewable Source of Energy in Nepal
Where wind power is the fastest growing exploited energy resource and is a well developed power in many countries around the world it is in still at an experimental stage even though it has been a well developed power in many countries around the world.  Lack of technical expertise and the unavailability of the wind data are the major problem in implementing the wind projects. 

Under the financial assistance f Danish Government a 30 kW wind power plant was installed by the Nepal Electricity Authority in Kagbeni, Mustang, but was totally damaged by high wind after only a few months of operation.

Anecdotal evidence of high wind speeds in various parts of countries shows that there is a possibility of manufacturing wind turbines in Nepal.

 

6. Wind energy scenario in Nepal
                  (a) It is concentrated in a few valleys such as mustang, Palpa and Khumbu.
                  (b) Wind potential identified in Jomsom is 200mw
                  (c) Wind potential in kagbeni is 20 kw.
                  (d) No. of major institute and organization on are involved in wind Energy
                       Sectors are:-

  1. Govt./semi Govt. is b,
  2.  NGO/INGO is 2,
  3.  Manufacture/ Installer/ Consultant is 3.

 

9. Wind Energy converter:-
                     (i) Wind turbine
                     (ii) Aero generator

APPENDIX
Recent Development:-
(a) Large scale electric power generation ( 800 kwc in france 1958-1960) ( total 
                  installed capacity in the world exceeds 2500 mw)

                     (e) Relatively expensive t maintain
10. Basic principle of wind energy conversion
                     (a) Nature of the wind                wind speed and direction
                                    (i) un uniform heating of the earth by the sun.
                                    (ii) Rotation of earth in its own axis & around the sun.
                                    (iii) Hills and coastal areas

  1. availability of water surface
  2. Height from tertian (earth surface)

                     (b) The power in the wind:-
                                    Wind energy output from a wind energy converter, depends upon:-

  1. The wind speed
  2. Cross-section of wind swept by motor.
  3. Overall conversion efficiency of the motor, transmission system & generator or pump


(c) Forces on the blades & thrust on turbine.
       There are two types of forces are acting on the blades:-

  1. Circumferential force:- acting in the direction of wheel rotation that provides torque.
  2.  Axial force:-  acting in the  direction of wind stream  that provides axial thrust.

                     (d) Wind Energy conversion:
                             (i) Small producers: - way of Back up energy:-
                                    a) Battery storage.
                                    b) Connection with Local electricity distribution system.
                                    c) A stand by generator powered by liquid or gasouse fuels
                            (ii) Large Producer:-
                        The choice of generator type depends upon the size local distribution grid and its generating capacity.
Type of generator:

  1. Induction generator: - used for significant amount of generating capacity. It is strong, reliable and required minimal control equipment.
  2. Synchronous generator:- used where the generating capacity is limited and required. And it is more complex and expensive than induction machine.