La Rance tidal power plant in La Rance, France Tidal and Wave Energy
Tides Tides are caused by the pull of the moon. Tides involve the rise and fall of sea levels. Around the coast of Ireland, the sea level rises and falls twice daily. Tidal energy can be used to generate electricity. The movement in an out of water can be harnessed by Barrages or Dams.
Waves are caused by wind, Waves wind is caused by the uneven heating of the Earths atmosphere and the heat comes from the sun. Wave energy can be used to produce electricity. Irelands location, on the edge of the Atlantic Ocean has some of the best wave-power sites in the world!
What is tidal energy? Tidal power facilities harness the energy from the rise and fall of tides. Two types of tidal plant facilities. Tidal barrages Tidal current turbines Ideal sites are located at narrow channels and experience high variation in high and low tides.
What is the Tidal force? The tidal force is the vectorial difference between the gravitational force of the Earth and the gravitational force of the Moon.
Energy from the moon Tides generated by the combination of the moon and sun s gravitational forces Greatest affect in spring when moon and sun combine forces Bays and inlets amplify the height of the tide In order to be practical for energy production, the height difference needs to be at least 5 meters Only 40 sites around the world of this magnitude Overall potential of 3000 gigawatts from movement of tides
What Causes Tides? http://www.pbs.org/wgbh/nova/earth/what-causes-the-tides.html
Tidal power, sometimes called tidal energy, is a form of hydropower that exploits the movement of water caused by tidal currents or the rise and fall in sea levels due to the tides. Although not yet widely used, tidal power has potential for future electricity generation and is more predictable than wind energy and solar power. About tidal power
high tide low tide
History of Tidal Tidal energy is one of the oldest forms of energy used by humans Dating back to 787 A.D., tide mills were constructed, consisting of a storage pond and a sluice (gate that controls water flow). During the incoming tide (flood), the sluice would open to allow rising waters to fill the storage pond During the outgoing tide (ebb), the stored water would be released over a waterwheel In the early 1960 s, the first commercial scale tidal power plant was built in St. Malo, France, consisting of twenty four 10MW turbines.
History of Tidal power stations An early attempt to build a tidal power plant took place at Aber- Wrac'h in the Finistere in 1925, but due to financial problems, it was abandoned in 1930. Tidal mills have long existed in areas affected by tides. In Europe, tide mills have been used for over a thousand years, mainly for grinding grains.
Tidal Barrages The ocean s tides can be used to accumulate potential energy, which can be converted to mechanical energy by turning a turbine in a manner quite similar to hydropower. As the tides rise and fall daily, basins along the shoreline naturally fill and empty. A complete tidal cycle takes 12.5 hours, so there are two high tides and two low tides a day. Dam-like structures called barrages can be built across the mouths of natural tidal basins with sluice gates. Water can be allowed to rise on one side of the sluice until enough of a hydraulic head is built up to power a turbine. The turbines are designed to work in either direction to maximize the utilization of the changing tide.
Tidal Barrages
Rance River Tidal Power Station The first commercial tidal power plant in the world is the La Rance Tidal Barrage in France built in 1967. The average tidal range is 28 ft, with a max of 44 ft. The barrage extends 2500 ft across. Produces 5.4 GWh of electricity per year, which is only 18% of the available energy in the basin.
Tidal Turbines Efforts are underway to anchor turbines to the ocean floor to harness tidal energy. This concept is proven, and in practice in a handful of locations on a small scale. This form of generation has many advantages over its other tidal energy rivals. The turbines are submerged in the water and are therefore out of sight. They don t pose a problem for navigation and shipping and require the use of much less material in construction. Tidal turbines are vastly better than wind turbines in terms of efficiency. A tidal turbine produces 4 times the output power per square meter of sweep area as a wind turbine, with a substantially smaller environmental impact.
Siemens SeaGen (S) Tidal Turbine
Domestic Tidal Power There are no tidal power stations in the U.S., but plans are underway to build a small tidal power farm in the East River of NYC. 300 underwater turbines On average, 10 MW of power (44GWh of electricity per year, enough for 8000 households) Alaska, Maine, and southeast Canada are potential target areas for barrages.
Ocean Thermal Energy Conversion (OTEC) The world s oceans constitute a vast natural reservoir for receiving and storing heat energy from the sun Nearly 75% of the surface area of Earth is water. Due to the high heat capacity of water, the, water near the surface is maintained at significant higher temperatures than water at greater depth It is possible to extract energy from the oceans through the use of heat engines in order to exploit the temperature differences between warm surface water and the cold, deep water
How it works First generation, barrage-style tidal power plants Works by building Barrage to contain water after high tide, then water has to pass through a turbine to return to low tide Sites in France (La Rance), Canada (Annapolis), and Russia Future sites possibly on Severn River in England, San Francisco bay, Passamaquoddy
Tidal streams Instead of damming estuaries the tidal currents are harnessed using wind like turbines
Main methods of current generation Marine current generator Stingray Tidal fence
How it works: Tidal Barrages
Wave Energy The kinetic energy of moving waves can be used to power a turbine. In this simple example the wave rises into a chamber. The rising water forces the air out of the chamber. The moving air spins a turbine which can turn a generator. When the wave drops, this creates a vacuum in the chamber, causing air to flow in the opposite direction
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
Benefits Renewable Can help protection of ports in storms Can help navigation for shipping Reliable, more so than solar or wind
Advantages Renewable and clean Tides are predictable There is a vast potential for energy generation With tidal turbines, the structures are out of sight Less required material for tidal turbines than wind
Environmental factors Change in currents Change in sediments Salinity and quality of water Migratory species
disadvantages Presently costly Expensive to build and maintain A 1085MW facility could cost as much as 1.2 billion dollars to construct and run Connection to the grid Technology is not fully developed Barrage style only produces energy for about 10 hours out of the day Barrage style has environmental affects Such as fish and plant migration Silt deposits Local tides change- affects still under study
Disadvantages Like wind and solar, tidal power is intermittent In addition, the hydraulic head obtained from tides is also variable Tides do not align with peak energy demand times With regard to barrages, some of the environmental impacts of dams are present with this technology as well, though to a much lower extent VERY, VERY, VERY EXPENSIVE Only produces 1/3 of the electricity that a hydropower plant of equal size would produce Wave power sites produce low energy output
Hydropower is an important renewable energy source world wide...
In 1880, the Grand Rapids Electric Light and Power Company used a water turbine to generate enough electricity to power 16 lights. Soon after, in 1882, the world s first hydroelectric power plant began operation on the Fox River in Appleton, WI. The plant, later named the Appleton Edison Light Company, was initiated by Appleton paper manufacturer H.F. Rogers, who had been inspired by Thomas Edison's plans for an electricity-producing station in New York. When you look at rushing waterfalls and rivers, you may not immediately think of electricity but hydroelectric power plants are responsible for lighting many of our homes and neighborhoods.
World s First Hydropower Plant
High-head Hydropower Tall dams are sometimes referred to as high-head hydropower systems. That is, the height from which water falls is relatively high.
Low-head Hydropower Many smaller hydropower systems are considered lowhead because the height from which the water falls is fairly low. Low-head hydropower systems are generally less than 20 feet high.
Environmental Considerations High-head hydropower systems can produce a tremendous amount of power. However, large hydropower facilities, while essentially pollution-free to operate, still have undesirable effects on the environment.
Installation of new large hydropower projects today is very controversial because of their negative environmental impacts. These include: upstream flooding declining fish populations decreased water quality and flow reduced quality of upstream and downstream environments Glen Canyon June 1962 Glen Canyon June 1964
Low-head and Low Impact Hydropower Scientists today are seeking ways to develop hydropower plants that have less impact on the environment. One way is through low-head hydropower. Low-head hydropower projects are usually low impact as well that is, they have fewer negative effects on the environment. Example of a low-head, low impact hydropower system.
Low Impact Hydropower A hydropower project is considered low impact if it considers these environmental factors: river flow water quality watershed protection fish passage and protection threatened and endangered species protection cultural resource protection recreation facilities recommended for removal
Small Francis Turbine & Generator "Water Turbine," Wikipedia.com 44
Francis Turbine Grand Coulee Dam "Water Turbine," Wikipedia.com 45
Fixed-Pitch Propeller Turbine "Water Turbine," Wikipedia.com 46
Kaplan Turbine Schematic "Water Turbine," Wikipedia.com 47
Kaplan Turbine Cross Section "Water Turbine," Wikipedia.com 48
1. Introduction What is fuel cell? A Fuel cell is a electrochemical device that converts chemical energy into electrical energy Every fuel cell has two electrodes, one positive and one negative, called, respectively, the cathode and anode. The reactions that produce electricity take place at the electrodes In all types of fuel cell, hydrogen is used as fuel and can be obtained from any source of hydrocarbon. The fuel cell transform hydrogen and oxygen into electric power, emitting water as their only waste product. PH 0101 Unit-5 Lecture-6 49
Every fuel cell also has an electrolyte, which carries electrically charged particles from one electrode to the other, and a catalyst, which speeds the reactions at the electrodes. A single fuel cell generates a tiny amount of direct (DC) electricity. A converter is used to produce AC current current In practice, many fuel cells are usually assembled into a stack. Cell or stack, the principles are the same. In 1932, Francis Bacon developed the first successful FC. He used hydrogen, oxygen, an alkaline electrolyte, and nickel electrodes. PH 0101 Unit-5 Lecture-6 50
2. A fuel cell configuration A fuel cell consists of two electrodes namely an anode and a cathode and sandwiched around an electrolyte. (+) (-) An electrolyte is a substance, solid or liquid, capable of conducting oving ions from one electrode to other. Anode Electrolyte Cathode PH 0101 Unit-5 Lecture-6 51
3. Types of fuel cells There are diffrent types of fuel cells, differentiated by the type of electrolyte separating the hydrogen from the oxygen.the types of fuel cells are: Alkaline fuel cells (AFC) Direct methanol fuel cells (DMFC) Molten carbonate fuel cell (MFFC) Phosphoric acid fuel cells (PAFC) Polymer electrolyte membrane fuel cells (PEMFC) Solid oxide fuel cells (SOFC) PH 0101 Unit-5 Lecture-6 53
4. Principle, construction and working of H2-O2 fuel cell Principle: The fuel is oxidized on the anode and oxidant reduced on the cathode. One species of ions are transported from one electrode to the other through the electrolyte to combine there with their counterparts, while electrons travel through the external circuit producing the electrical current. Fuel Fuel Permeable Anode Electrons (e - ) Cations (+ve) Anions (-ve) Electrolyte Oxidant Permeable Cathode Oxidant PH 0101 Unit-5 Lecture-6 54
Working The Fuel gas (hydrogen rich) is passed towards the anode where the following oxidation reaction occurs: H 2 (g) = 2H + + 2e - The liberated electrons from hydrogen in anode side do not migrate through electrolyte. Therefore, they passes through the external circuit where work is performed, then finally goes into the cathode. On the other hand, the positive hydrogen ions (H + ) migrate across the electrolyte towards the cathode. PH 0101 Unit-5 Lecture-6 55
At the cathode side the hydrogen atom reacts with oxygen gas (from air) and electrons to form water as byproduct according to: The overall cell reaction is fuel + oxidant H 2 + 1/2 O 2 +2e - product + Heat H 2 O + Heat PH 0101 Unit-5 Lecture-6 56
The liberated electrons from the hydrogen are responsible for the production of electricity. The water is produced by the combination of hydrogen, oxygen and liberated electrons and is sent out from the cell. The DC current produced by fuel cell is later converted into AC current using an inverter for practical application. The voltage developed in a single fuel cell various from 0.7 to 1.4 volt. More power can be obtained by arranging the individual fuel cell as a stack. In this case, each single cell is sandwiched with one another by a interconnect. Therefore, electricity power ranging from 1 kw to 200 kw can be obtained for domestic as well as industrial application. PH 0101 Unit-5 Lecture-6 57
Electrical power production by fuel cell Hydrogen Oxygen Rotating shaft connected to generator for electricity production PH 0101 Unit-5 Lecture-6 58
5. Advantage, disadvantage and applications Advantages Zero Emissions: a fuel cell vehicle only emits water vapour. Therefore, no air pollution occurs. High efficiency: Fuel cells convert chemical energy directly into electricity without the combustion process. As a result, Fuel cells can achieve high efficiencies in energy conversion. High power density: A high power density allows fuel cells to be relatively compact source of electric power, beneficial in application with space constraints. PH 0101 Unit-5 Lecture-6 59
Quiet operation: Fuel cells can be used in residential or built-up areas where the noise pollution can be avoided. No recharge: Fuel cell systems do not require recharging. Disadvantages It is difficult to manufacture and stores a high pure hydrogen It is very expense as compared to battery PH 0101 Unit-5 Lecture-6 60
Applications 1. Portable applications They used in portable appliances and power tools They can be used in small personal vehicles They are used Consumer electronics like laptops, cell phones can be operated They can be used in Backup power PH 0101 Unit-5 Lecture-6 61
2. Transportation applications They can be used for transport application in the following areas, Industrial transportation Public transportation Commercial transportation (truck, tractors) Marine and Military transportation PH 0101 Unit-5 Lecture-6 62
3. Power distribution application Fuel cells can be used for the distribution of power in various fields such as, Homes and small businesses Commercial and industrial sites Remote, off-grid locations (telecom towers, weather stations) PH 0101 Unit-5 Lecture-6 63