UNIT4 -NON-CONVENTIONAL POWER GENERATION

1. UNIT4 -NON-CONVENTIONAL POWER GENERATION • Solar Energy • Geothermal resources • Wind power plants • Tidal power plants • MHD power generation-principle

2. Solar Energy ….and it’s many uses

3. SOLAR ENERGY A FEW FACTS • Every day the earth receives thousands of times more energy from the sun than is consumed in all other resources. • If a 140x140 mile parcel of land in Arizona was covered with solar cells, the electricity needs of the entire United States could be met. • The sunlight falling on a typical house can provide from 1/3 to 1/2 of the heating needs of that house. • Today solar energy accounts for only 1% of the total renewable energy consumed in the United States

4. Characteristics of Isolation • Isolation is the amount of solar radiation reaching the earth. Also called Incident Solar Radiation. • The sun’s energy is created from the fusion of hydrogen nuclei into helium nuclei. • Components of Solar Radiation: • Direct radiation • Diffuse radiation • Reflect radiation

5. SOLAR HEATING TODAY • Used mostly for heating pools and domestic hot water (DHW) • Two types of solar heating systems: • Active Solar Heating System • Passive Solar Heating System

6. ACTIVE SOLAR HEATING SYSTEM • A system that uses water or air that the sun has heated and is then circulated by a fan or pump. • Three Types: • Flat Plate Collectors • Batch Water Heaters • Thermosiphon

7. FLAT PLATE COLLECTORS • A thin flat metal plate is used to absorb the sun’s radiation. • Tubes carry water into the absorber plate where it is heated by the sun and sent to a pump or fan into storage and distributed from there to the living space.

8. BATCH WATER HEATERS • Pre-heats water using the sun by having a black tank inside an isolated box with a glass cover. • Solar energy is absorbed within the box to heat the water. • The water outflow is sent into a conventional water heater for further heating. • They are also called “Bread-Box” heaters.

9. THERMOSIPHEN • This method places the storage tank above the solar collector. • Cold water is put into the bottom of the storage tank where it is circulated through a flat plate collector and pumped back into the top of the storage tank. The heated water can then be taken from the top and used.

10. PASSIVE SOLAR HEATING SYSTEMS • The house itself acts as the solar collector and storage facility. • No pumps or fans are used. • This system makes use of the materials of the house to store and absorb heat. • Three Types: • Direct-Gain • Indirect-Gain • Attached Greenhouse

11. DIRECT-GAIN • Large south facing windows that let in the sunlight. • Thermal mass is used to absorb the radiation. • At night the absorbed heat is radiated back into the living space.

12. INDIRECT-GAIN • Collects and stores the solar energy in one part of the house and use natural heat transfer to distribute heat to the rest of the house. • Popular method is to use a Trombe Wall which is a massive black masonry that acts as a solar collector and a heat storage medium.

13. GEOTHERMAL ENERGY

14. Sources of Earth’s Internal Energy • 70% comes from the decay of radioactive nuclei with long half lives that are embedded within the Earth • Some energy is from residual heat left over from Earths formation. • The rest of the energy comes from meteorite impacts.

15. Different Geothermal Energy Sources • Hot Water Reservoirs: As the name implies these are reservoirs of hot underground water. There is a large amount of them in the US, but they are more suited for space heating than for electricity production. • Natural Stem Reservoirs: In this case a hole dug into the ground can cause steam to come to the surface. This type of resource is rare in the US. • Geopressured Reservoirs: In this type of reserve, brine completely saturated with natural gas in stored under pressure from the weight of overlying rock. This type of resource can be used for both heat and for natural gas.

16. Normal Geothermal Gradient: At any place on the planet, there is a normal temperature gradient of +300C per km dug into the earth. Therefore, if one digs 20,000 feet the temperature will be about 1900C above the surface temperature. This difference will be enough to produce electricity. However, no useful and economical technology has been developed to extracted this large source of energy. • Hot Dry Rock: This type of condition exists in 5% of the US. It is similar to Normal Geothermal Gradient, but the gradient is 400C/km dug underground. • Molten Magma: No technology exists to tap into the heat reserves stored in magma. The best sources for this in the US are in Alaska and Hawaii.

17. How Direct Uses Work • Direct Sources function by sending water down a well to be heated by the Earth’s warmth. • Then a heat pump is used to take the heat from the underground water to the substance that heats the house. • Then after the water it is cooled is injected back into the Earth.

18. Ground Heat Collectors This system uses horizontal loops filled with circulating water at a depth of 80 to 160 cm underground. Borehole Heat Exchange This type uses one or two underground vertical loops that extend 150 meters below the surface.

19. Generation of Electricity is appropriate for sources >150oC • Dry Steam Plants: These were the first type of plants created. They use underground steam to directly turn the turbines.

20. Flash Steam Plants: These are the most common plants. These systems pull deep, high pressured hot water that reaches temperatures of 3600F or more to the surface. This water is transported to low pressure chambers, and the resulting steam drives the turbines. The remaining water and steam are then injected back into the source from which they were taken.

21. Binary Cycle Plants: This system passes moderately hot geothermal water past a liquid, usually an organic fluid, that has a lower boiling point. The resulting steam from the organic liquid drives the turbines. This process does not produce any emissions and the water temperature needed for the water is lower than that needed in the Flash Steam Plants (2500F – 3600F). Casa Diablo

22. Hot Dry Rocks: The simplest models have one injection well and two production wells. Pressurized cold water is sent down the injection well where the hot rocks heat the water up. Then pressurized water of temperatures greater than 2000F is brought to the surface and passed near a liquid with a lower boiling temperature, such as an organic liquid like butane. The ensuing steam turns the turbines. Then, the cool water is again injected to be heated. This system does not produce any emissions. US geothermal industries are making plans to commercialize this new technology.

23. Geothermal’s Harmful Effects • Brine can salinate soil if the water is not injected back into the reserve after the heat is extracted. • Extracting large amounts of water can cause land subsidence, and this can lead to an increase in seismic activity. To prevented this the cooled water must be injected back into the reserve in order to keep the water pressure constant underground. • Power plants that do not inject the cooled water back into the ground can release H2S, the “rotten eggs” gas. This gas can cause problems if large quantities escape because inhaling too much is fatal.

24. Geothermal’s Positive Attributes • Useful minerals, such as zinc and silica, can be extracted from underground water. • Geothermal energy is “homegrown.” This will create jobs, a better global trading position and less reliance on oil producing countries. • US geothermal companies have signed $6 billion worth of contracts to build plants in foreign countries in the past couple of years. • In large plants the cost is 4-8 cents per kilowatt hour. This cost is almost competitive with conventional energy sources.

25. Geothermal plants can be online 100%-90% of the time. Coal plants can only be online 75% of the time and nuclear plants can only be online 65% of the time. • Flash and Dry Steam Power Plants emit 1000x to 2000x less carbon dioxide than fossil fuel plants, no nitrogen oxides and little SO2. • Geothermal electric plants production in 13.380 g of Carbon dioxide per kWh, whereas the CO2 emissions are 453 g/kWh for natural gas, 906g g/kWh for oil and 1042 g/kWh for coal. • Binary and Hot Dry Rock plants have no gaseous emission at all. • Geothermal plants do not require a lot of land, 400m2 can produce a gigawatt of energy over 30 years.

26. Electricity generated by geothermal plants saves 83.3 million barrels of fuel each year from being burned world wide. This prevents 40.2 million tons of CO2 from being emitted into the atmosphere. • Direct use of geothermal energy prevents 103.6 million barrels of fuel each year from being burned world wide. This stops 49.6 tons of CO2 from being emitted into the atmosphere.

27. Availability of Geothermal Energy • On average, the Earth emits 1/16 W/m2. However, this number can be much higher in areas such as regions near volcanoes, hot springs and fumaroles. • As a rough rule, 1 km3 of hot rock cooled by 1000C will yield 30 MW of electricity over thirty years. • It is estimated that the world could produce 600,000 EJ over 5 million years. • There is believed to be enough heat radiating from the center of the Earth to fulfill human energy demands for the remainder of the biosphere’s lifetime.

28. WIND POWER • What is it? • How does it work? • Efficiency • U.S. Stats and Examples

29. WIND POWER - What is it? • All renewable energy (except tidal and geothermal power), ultimately comes from the sun • The earth receives 1.74 x 1017 watts of power (per hour) from the sun • About one or 2 percent of this energy is converted to wind energy (which is about 50-100 times more than the energy converted to biomass by all plants on earth • Differential heating of the earth’s surface and atmosphere induces vertical and horizontal air currents that are affected by the earth’s rotation and contours of the land  WIND. ~ e.g.: Land Sea Breeze Cycle

30. Winds are influenced by the ground surface at altitudes up to 100 meters. • Wind is slowed by the surface roughness and obstacles. • When dealing with wind energy, we are concerned with surface winds. • A wind turbine obtains its power input by converting the force of the wind into a torque (turning force) acting on the rotor blades. • The amount of energy which the wind transfers to the rotor depends on the density of the air, the rotor area, and the wind speed. • The kinetic energy of a moving body is proportional to its mass (or weight). The kinetic energy in the wind thus depends on the density of the air, i.e. its mass per unit of volume. In other words, the "heavier" the air, the more energy is received by the turbine. • at 15° Celsius air weighs about 1.225 kg per cubic meter, but the density decreases slightly with increasing humidity.

31. WINDMILL DESIGN • A Windmill captures wind energy and then uses a generator to convert it to electrical energy. • The design of a windmill is an integral part of how efficient it will be. • When designing a windmill, one must decide on the size of the turbine, and the size of the generator.

32. LARGE TURBINES: Able to deliver electricity at lower cost than smaller turbines, because foundation costs, planning costs, etc. are independent of size. Well-suited for offshore wind plants. In areas where it is difficult to find sites, one large turbine on a tall tower uses the wind extremely efficiently. WIND TURBINE

33. SMALL TURBINES: • Local electrical grids may not be able to handle the large electrical output from a large turbine, so smaller turbines may be more suitable. • High costs for foundations for large turbines may not be economical in some areas. • Landscape considerations

34. Wind Turbines: Number of Blades • Most common design is the three-bladed turbine. The most important reason is the stability of the turbine. A rotor with an odd number of rotor blades (and at least three blades) can be considered to be similar to a disc when calculating the dynamic properties of the machine. • A rotor with an even number of blades will give stability problems for a machine with a stiff structure. The reason is that at the very moment when the uppermost blade bends backwards, because it gets the maximum power from the wind, the lowermost blade passes into the wind shade in front of the tower.

35. WIND TURBINE GENERATOR • Wind power generators convert wind energy (mechanical energy) to electrical energy. • The generator is attached at one end to the wind turbine, which provides the mechanical energy. • At the other end, the generator is connected to the electrical grid. • The generator needs to have a cooling system to make sure there is no overheating.

36. SMALL GENERATORS: • Require less force to turn than a larger ones, but give much lower power output. • Less efficient i.e.. If you fit a large wind turbine rotor with a small generator it will be producing electricity during many hours of the year, but it will capture only a small part of the energy content of the wind at high wind speeds. • LARGE GENERATORS: • Very efficient at high wind speeds, but unable to turn at low wind speeds. i.e.. If the generator has larger coils, and/or a stronger internal magnet, it will require more force (mechanical) to start in motion.

37. Advantages of Wind Power • The wind blows day and night, which allows windmills to produce electricity throughout the day. (Faster during the day) • Energy output from a wind turbine will vary as the wind varies, although the most rapid variations will to some extent be compensated for by the inertia of the wind turbine rotor. • Wind energy is a domestic, renewable source of energy that generates no pollution and has little environmental impact. Up to 95 percent of land used for wind farms can also be used for other profitable activities including ranching, farming and forestry. • The decreasing cost of wind power and the growing interest in renewable energy sources should ensure that wind power will become a viable energy source in the United States and worldwide.

38. Tidal Power

39. Tidal power is dependant on tides created by the moons gravitational pull on the earth

40. Types of Tidal Power Generation • Barrages • Tidal Streams

41. Tidal Barrage • Turbines • Sluice gates • Embankments

42. Bulb Turbine

43. Straflo or Rim Generator Turbine

44. Tubular Turbine

45. Benefits • Renewable • Can help protection of ports in storms • Can help navigation for shipping • Reliable, more so than solar or wind

46. Tidal streams • Instead of damming estuaries the tidal currents are harnessed using wind like turbines

47. Benefits of Tidal stream • Far less intrusive • Can generate same amount of power as wind with smaller blades moving slower due to density of water • More available sites • More reliable than wind • Usually less expensive than barrage

48. Magnetohydrodynamic (MHD)Generator

49. MHD power generation uses the interaction of an electrically conducting fluid with a magnetic field to convert part of the energy of the fluid directly into electricity • Converts thermal or kinetic energy into electricity

50. Where • F is the force of the acting particle (vector) • V is the velocity of the particle (vector) • Q is the charge of the particle (scalar) • B is the magnetic field (vector) Lorentz Force Law: F = QvB