Earth’s Heat – Geothermal Energy (page 530)
Geothermal Energy - Read pages 530 – 532
Tidal Energy (page 532)
Tidal power exploits the kinetic energy of the earth-moon-sun system.
Tidal bulges are caused by the gravitational attraction between the moon-earth and the sun-earth systems. The earth rotates under the bulges. The result is variations in coastal sea levels daily.
These fluctuations cause water to rush into tidal basins approximately twice each day. This flowing water can be used to turn turbines to generate electricity. Turbines are designed for work at both high and low tide (inflow or outflow).
The station generates power by allowing the incoming tide to fill the head pond through the sluice gates. When the head pond reaches its maximum level the sluice gates are closed, trapping the water in the head pond. When the tide recedes outside of the head pond and drops below by 1.6 m or more than 18 wicket gates to the distributor assembly open. The gates control the flow of the water through the turbine. When the gates are open water flows through at the rate of 400 cubic metres per second and turns a massive four-blade runner. The power generating phase lasts for approximately five hours, at which time the gates close and a new cycle begins. This is repeated twice daily.
Steps involved in the conversion of energy in tidal power generating systems are very similar to conventional hydro power generation
• The gravitational force of the moon transfers energy to the ocean water.
• The kinetic energy of the moving water is then converted to gravitational potential energy as it is stored in the tidal basin behind the barrage
• The gravitational energy of the water is converted back to kinetic energy as the water is released from the tidal basin
• This kinetic energy is converted to mechanical energy of the turning turbines, the turbine shaft and the rotor of the generator.
• With in the generator, the mechanical energy is finally converted to electrical energy.
Renewable Solar Energy Sources
Renewable energy is any type of energy which has an abundant and ongoing source, such as:Sun's rays • Wind
• Rivers
• Biomass (combustion of organic material
Solar Energy Sources
The sun is the fundumental source of energy that makes life possible. Nearly all the energy sources we use are indirecly solar. For example, the energy stored in the food we eat comes from the sun. Photosynthesis uses energy to make glucose out of carbon dioxide and water.
Photosynthesis: CO2(g) + H2O(g) + sunlight C6H12O6(s) + O2(g)
Plants use glucose as an energy source. Plants also store glucose as starch that animals consume as their energy source. Glucose is also stored as cellulose (wood), which humans have used as an energy source for millions of years. Even when animals eat other animals, they are gaining energy from the sun, because the sun provides the original energy to the producers in that food chain. When you eat a steak, your body is capturing the sun’s energy.
Burning wood and other biomass is a way to release the sun’s energy indirectly. Other indirect ways include harnessing the wind. Wind is caused by the sun’s energy. The kinetic energy of wind is used to generate electricity. In fact solar radiation energizes the whole of Earth’s climate. Solar radiation drives the
water. As water flows downhill it’s potenial energy becames kinetic energy, which can be used to generate electricity. Ocean waves are caused by wind (caused by solar energy). Waves can be used to generate electricity.
Even the fossil fuels are stored solar energy. Fossil fuels come from organic sediments. These organic sediments used to be plants and animals whom (when they were alive) got their energy from the sun.
Solar energy can also be used to generate electricity directly. Usually this is what people mean when they say “solar power.”
Solar Power
The sun heats the closed system of solar-designed house much the same way that it heats the closed system of the bioshpere.
Earth
House
Greenhouse effect:
• Sun’s energy passes through the atmosphere
• Electromagnetic energy reaching Earth’s surface is absorbed and converted to thermal energy
• Some is converted to long wavelength infra-red radiation, which is trapped by the atmosphere
• Unequal heating of the Earth’s surface results causes convection currents, creates weather systems and distributes heat around the globe
• Sun’s energy enter the house through large south-facing windows
• Electromagnetic energy is absorbed by the walls, floors and furniture and converted to thermal energy
• Some energy is reflected as long wave infra-red radiation which cannot escape through the
windows and is reflected around the house until it is absorbed and converted to thermal energy • Thermal energy trapped warms the air, causing
Solar energy can be used directly to heat homes. Every solar heating system does three basic things: 1. Captures the sun’s energy
2. Stores it for later use
3. Distributes the heat to where it is needed.
Passive Solar Heating
The basic elements-capture, storage,
distribution-are part of the building and do not
require any mechanical assistance. Most
passive solar houses take advantage of building materials such as concrete, brick, stone and ceramic tile that store thermal energy and release it when the air temperature drops in the evening.
Active Solar Heating
Many active solar heating systems include a
solar collector, a thermal storage tank and mechanical devices to distribute the heat. The most common collector is called a flat-plate collector.
1) Mounted on the roof, it consists of a thin, flat, rectangular box with a transparent cover that faces the sun. 2) Small tubes run through the box and carry the fluid – either water or other fluid, such as an antifreeze
solution – to be heated. The tubes are attached to an absorber plate, which is painted black to absorb the heat. 3) As heat builds up in the collector, it heats the fluid passing through the tubes.
4) The storage tank then holds the hot liquid. It can be just a modified water heater, but it is usually larger and very well insulated.
Photovoltaic cells: Solar Electricity Generation (page 540)
Photovoltaic or solar cells (PV for short) are made of silicon and can turn sunlight directly into DC electricity. Each cell produces a small amount of current. By connecting many cells together and placing them on larger panels, the electric current produced can be significant. This can be used directly in a DC appliance, stored in batteries, or converted to AC to operate AC appliances using an inverter.
Photovoltaic Cell
While extremely simple, photovoltaic cells are expensive compared to other generating sources. Also the cells themselves are fairly reliable, the sun's rays are not a very predictable resource in most areas. Therefore, other equipment such as battery storage systems and an inverter to convert the DC current AC are often needed. Solar or photovoltaic power has consequently mostly been used for specialized situations such as satellites, portable electronic equipment such as calculators, and power in remote locations.
Hydroelectric Power (page 541)
Hydroelectric power harnesses the potential energy of water. Water is lifted to higher elevations by the hydrologic cycle (below). This difference in potential energy is just like an electrical potential difference (voltage).
As the water flows back to lower elevations, it’s like a current of electrons. In fact, this energy can be changed from the kinetic energy of water to the kinetic energy of electrons.
Wind power is expanding in Pincher Creek, Alberta
Wind Energy (page 545)
Wind energy has become the world's fastest-growing source of new electricity supply - thanks to several factors,
including electricity industry deregulation, lower technical costs, more reliable technology and growing concerns over harmful emissions from other, competing energy sources. Today, wind-generated electric power is becoming cost-competitive with most other conventional sources. Unlike oil and natural gas, for example, wind energy is not subject to frequent price fluctuations. And unlike coal, wind power
does not involve high emissions of greenhouse gases, particulates and other pollutants. Remember, wind power is an indirect
form of solar power. The
electromagnetic radiation from the sun heats the earth. The earth re-emits this thermal energy creating convection currents, which in turn, generate wind. The kinetic energy of the wind is converted to the mechanic energy of a spinning turbine. The turbine spins a magnetic rotor inside of a coil of wire converting mechanical energy to electrical energy.
Biomass Energy (page 546)
Biomass is organic material, which has
stored sunlight in the form of chemical energy. Biomass fuels include wood, wood waste, straw, manure, sugar cane, and many other byproducts from a variety of agricultural processes. The real environmental benefit of biomass will come when we can use large amounts of biomass to
generate electricity, thereby reducing consumption of fossil fuels.
There are three major ways of converting biomass to useable energy:
1. Simple combustion to produce heat and or electricity.
When burned, the chemical energy is released as heat. If you have a fireplace, the wood you burn in it is a biomass fuel. What we now call biomass was the chief source of heating homes and other buildings for thousands of years. In fact, biomass continues to be a major source of energy in much of the
2. Thermochemical conversion, utilizes heat to break down biomass into new solid, liquid and gaseous fuels such as methanol. These biomass fuels can be used for transportation, electricity and industrial process heat
3. Biochemical conversion, uses enzymes and microorganisms to produce alternative fuels. For example glucose can be converted through a series of reaction to ethanol. 10% ethanol can be blended with gasoline to produce gasohol.
Biogas Digester Methane Gas Extraction - Case Study
THE CLOVER BAR PROJECT, Edmonton
Background
Landfilled material often yields methane gas (natural gas) as a product of oxygen-free decomposition. This gas is often collect from the landfill and flared off, because methane can be dangerous in high concentrations and is a very strong greenhouse gas.
Edmonton is fortunate in having a large landfill site close to the natural gas-fired Clover Bar Generating Station, owned and operated by Edmonton Power. This station is power on natural gas and can generate 660 MW at full load
Edmonton power uses the methane/carbon dioxide mixture (with trace impurities removed) as a fuel supplement for the Clover Bar Generating Station. Unlike many projects where landfill gas is used in its raw condition, landfill gas at Clover Bar is filtered, compressed, and scrubbed
Production Rates
There will be occasions when the Clover Bar Generating Station will be unable to accept landfill gas due to low demand. Under these circumstances it is planned for landfill gas to be flared at the purification plant to prevent the release of methane to the atmosphere.
It is difficult operating a landfill gas plant in Alberta where natural gas prices are low. Tight control on costs has been needed to ensure an economically successful project. During times of low natural gas prices and low electrical
demand, a landfill gas project may operate at a loss. However there will be other times when such an operation can be quite profitable.
Environmental Benefits
Besides needing to make good business sense, a significant benefit of the Clover Bar Landfill Gas Project is environmental in nature. Methane and carbon dioxide are both regarded as greenhouse gases but do not exhibit the same global warming impact. The Intergovernmental Panel on Climate Change (IPCC) consider the global warming potential of methane to be 21 times that of carbon dioxide on a weight basis over a 100 year time integration. Methane is more detrimental to the environment than carbon dioxide so its capture, purification and conversion to carbon dioxide is very desirable.
The use of landfill gas also reduces the natural gas demand by the Clover Bar Generating Station and conserves supplies of this resource. It directionally reduces the load on sour natural gas purification facilities elsewhere in the province with the accompanying environmental benefits.
Landfill gas is contaminated with traces of other chemical compounds such as hydrogen chloride, hydrogen sulphide, benzene, vinyl chloride and disiloxane. The amounts will depend on the composition of the garbage. As an example, the presence of gypsum wallboard waste will increase the sulphate concentration in the landfill and hence the hydrogen sulphide and sulphur dioxide content of landfill gas. There can therefore be a variety of toxic gases that can vent from a landfill site to the environment in small but uncontrolled amounts.
Biomass can be exploited on almost any scale. A farmer (right) displays his homemade chicken fuel (made from chicken manure). In fact, people have been using manure/dung as an energy source for millennia (below).
In fact, your manure may be powering the Gold Bar Wastewater treatment plant in Edmonton. The methane produced during the anaerobic decomposition of your feces is used and an energy source. The facility is looking for ways to increase their use of this methane, as more is produced than is required to power the plant. Much of it is flared off.
As you know manure, is a problem in Alberta, as it can lead the nitrate pollution of bodies of water. Some farmers are proposing ways to turn this problem into a source of energy.
Biomass Energy
– Read pages 546-548 and Fill in the following chart
A woman in Nepal collects yak dung for a fire
