Source: www.eia.doe.gov 0.3% Waste 1.2% Dung 8% 6.6% Wood 2.0% Hydro 0.13% Uranium 92% 19.0% Gas 38.5% Oil 32.5% Coal Total Energy Consumption Source
Non-commercial / Non-conventional Energy Sources
Bio-mass / Bio-gas
Non-commercial / Non-conventional Energy Sources Several multiple megawatt wind turbines are in operation and many more are in construction. There are number of small wind turbines and wind Pumps in use. Electricity Mechanical Energy (Pumping Transport) Wind The kinetic energy Millions of solar water heaters and solar cookers are in use. Solar cells and Power Towers are in operation. Low temperature heat (Space heating water heating and electricity) Solar Total solar radiation absorbed by the earth and its atmosphere is 3.8 x 10 24 J/Yr. Comment From / Application Resource
Non-commercial / Non-conventional Energy Sources There are million of biogas plants in operation, most of them are in China. Bio-gas (Cooking, mechanical power etc.) The world’s standing bio-mass has a energy content of about 1.5X10 22 J Biomass (principally wood accounts for about 15% of the world’s (commercial fuel) Consumption; It provides over 80% of the energy needs of many developing countries. High temperature heat (Cooking, Smelting) Biomass Total solar radiation absorbed by plants is 1.3X10 21 J/Yr Comment From / Application Resource
Non-commercial / Non-conventional Energy Sources Installed capacity Is more than 2500 MW but output is expected to Increase more than seven fold by 2000. Electricity The total amount of heat stored in water or steam to a depth of 10 km is estimated to be 4 X 10 21 J that stored In the First 10 km of dry rock Is around 10 27 J/yr Geothermal energy supplies about 5350 MW of heat for use in bathing principally in Japan, but also in Hungary Ice land and Italy. More than one lakh houses are supplied with heat from geothermal wells. The installed capacity is more than 2650 MW (thermal) Low temperature heat (Bathing space and water heating) Geothermal The heat flux from the Earth's interior through the surface is 9.5 X 10 20 J/Yr. Comment From / Application Resource
Non-commercial / Non-conventional Energy Sources The Japanese wave energy research vessel, the Kaimel. has an Installed capacity of about 1 MW. There are In addition several hundred waves powered navigational buoys designs after large prototype Electricity Wave The amount of energy stored as Kinetic Energy in weaves may be of the order of 10 18 J Only one large tidal barrage is in operation (In France) and three are small schemes In Russia and China total Installed. Capacity is about 240 MW and the out put around OS TWh/Yr. In addition China has several small tidal pumping stations. Electricity Tidal Energy dissipated In connection with slowing down the rotation of the earth. Comment From / Application Resource
Non-commercial / Non-conventional Energy Sources Large hydro schemes provide about one quarter of worlds total electricity supply and more than 40% of the electricity used in developing counties. The installed capacity is more than 363GW. The technically usable Potential is estimated to be 2215GW or 19000 TWh/Yr There are no accurate estimates of the number of capacity of small hydro-plants currently in operation. Electricity Hydro The annual precipitation land amounts to about 1.1 x 10 17 Kg. of water. Taking the average elevation of land area as 840 m. The annually accumulated potential energy would be 9 x 10 20 J Comment From / Application Resource
Economies of Wind Power Wind Power cost v/s conventional Power Cost Years of Operation
Earth's rotation causes Coriolis force resulting in
an easterly wind velocity component in the northern hemisphere
Boundary layer frictional effects between the moving air and the earth's rough surface (mountains, trees, buildings and similar obstructions )
Differential heating of land and water. Unequal solar absorption and thermal time constants of land and water. During daylight the land heats up rapidly compared to nearby sea or water bodies and there tend to be a surface wind flow from the water to the land. At night the wind reverses, because the land surface cools faster than the water.
Hills and mountainsides. The air above the slopes heats-up during the day and cools down at night more rapidly than the air above the low lands. This causes heated air during the day to rise along the slopes and relatively cool heavy air to flow down at night
2% of all solar radiation falling on the face of earth is converted to kinetic energy of wind. 30% of this occurs in lowest 1000m elevation of the atmosphere.
Kinetic energy of any particle is equal to one half of its mass (M) times the square of its velocity (V) : P a = ½ MV 2
The amount of air passing in unit time, through an area (A), with velocity (V) is A*V; and its mass (M) is equal to its volume multiplied by its density ( ) of air (1.225 kg/m 3 at sea level) M = AV a = ½ AV * V 2 Pa = ½ AV 3 Watts Available Wind energy is proportional to the cube of the wind speed
Larger machines are usually able to deliver electricity at a lower cost than smaller machines.
The reason is that the cost of foundations, road building, electrical grid connection, plus a number of components in the turbine (the electronic control system etc.), are somewhat independent of the size of the machine.
Maintenance Costs are largely independent of the size of the machine.
Difficult sites Locations
In areas where it is difficult to find sites for more than a single turbine, a large turbine with a tall tower uses the existing wind resource more efficiently.
The local electrical grid may be too weak to handle the electricity output from a large machine. This may be the case in remote parts of the electrical grid with low population density and little electricity consumption in the area.
Wind Park Fluctuations
Wind fluctuations occur randomly, and therefore tend to cancel out. Again, smaller machines may be an advantage in a weak electrical grid.
A large machine really does not attract as much attention as many small, fast moving rotors.
The cost of using large cranes, and building a road strong enough to carry the turbine components may make smaller machines more economic in some areas.
If we used an ordinary generator, directly connected to a 50 Hz AC three phase grid with two, four, or six poles, we would have to have an extremely high speed turbine with between 1000 and 3000 revolutions per minute (rpm).
With a 43 m. of rotor diameter that would imply a tip speed far more than twice the speed of sound !!
Another possibility is to build a slow-moving AC generator with many poles. But it may need a 200 pole generator to arrive at a reasonable rotational speed of 30 rpm.
Another problem is, that the mass of the rotor of the generator has to be roughly proportional to the amount of torque (moment, or turning force) it has to handle. So a directly driven generator will be very heavy (and expensive) in any case.
Export of k VARh Reactive Power supplied to grid e.g. over compensation.
Import of kVARh Reactive power drawn from Grid e.g. for magnetizing current of generator (These units of kVARh charged as penalty to the owner by State Electricity Board at a rate decided by respective SEBs)
The reason why it is called a synchronous Generator is that the magnet in the centre will rotate at a constant speed which is synchronous with (running exactly like the cycle in) the rotation of the magnetic field.
Consequently, with this type of generator you will normally want to use an indirect grid connection of the generator.
If we double the number of magnets in the Rotor, however, we can ensure that the magnetic field rotates at half the speed.
This generator has four poles at all times, two South and two North. Since a four pole generator will only take half a revolution per cycle, it will obviously make 25 revolutions per second on a 50Hz grid, or 1500 revolutions per minute (rpm).
When we double the number of poles in the Stator of a synchronous generator we will have to double the number of magnets in the Rotor, as you see on the picture. Otherwise the poles will not match.
When the current is connected, the machine will start turning like a motor at a speed which is just slightly below the synchronous speed of the rotating magnetic field from the stator.
If we look at the rotor bars from above we have a magnetic field which moves relative to the rotor. This induces a very strong current in the rotor bars which offer very little resistance to the current, since they are short circuited by the end rings.
The rotor then develops its own magnetic poles, which in turn become dragged along by the electromagnetic force from the rotating magnetic field in the stator.
Now, what happens if we manually crank this rotor around at exactly the synchronous speed of the generator, e.g. 1500 rpm
Nothing. Since the magnetic field rotates at exactly the same speed as the rotor, we see no induction phenomena in the rotor, and it will not interact with the stator.
But if we increase speed above 1500 in the rotor. The harder you crank the rotor, the more power will be transferred as an electromagnetic force to the stator, and in turn converted to electricity which is fed into the electrical grid.
The speed of the asynchronous generator will vary with the turning force (moment, or torque) applied to it. In practice, the difference between the rotational speed at peak power and at idle is very small, about 1 per cent. This difference in per cent of the synchronous speed , is called the generator's slip.
The advantage of indirect grid connection is that it is possible to run the wind turbine at variable speed.
Disadvantages of Indirect Grid Connection is cost . The turbine will need a rectifier and two inverters, one to control the stator current, and another to generate the output current.
Other disadvantages are the energy lost in the AC-DC- AC conversion process
The power electronics may introduce harmonic distortion of the alternating current in the electrical grid, thus reducing power quality. The problem of harmonic distortion arises because the filtering process mentioned above is not perfect, and it may leave some "overtones" (multiples of the grid frequency) in the output current.
Wind speeds are usually measured as 10 minute averages
Wind roses : vary from one location to the next As an example, take a look at this wind rose : Although the primary wind direction is the same, Southwest, you will notice that practically all of the wind energy comes from West and Southwest, so on this site we need not concern ourselves very much about other wind directions.
Isovents : Contours of constant average wind velocity, (Monthly / Quarterly / Yearly average )
Isodynes : Contours of constant wind power ( Watts / m3 of the area@ perpendicular to the wind flow )
There should be no tall obstructions for a radius of 3 km.
An open plain or an open shore line may be a good location
The top of a smooth, well rounded hill with gentle slopes laying on a flat plain or located on an island in a lake or sea.
A mountain gap which produces to wind tunneling is good
Wind Energy Worldwide World Leaders in Wind Capacity December 2003 Country Capacity (MW) Germany 14,609 United States 6,374 Spain 6,202 Denmark 3,110 India 2,110 Netherlands 912 Italy 904 Japan 686 United Kingdom 649 China 568
Wind Energy Potential in India State-wise Power Installed Capacity in India (As on 31 st December, 2003) Source: MNES