INDEPTH: ENERGY
Sources of Energy
CBC News Online | May 20, 2004
Natural Gas
What is it?
Natural gas, consisting mainly of methane, is a colourless, odourless fuel that burns cleaner than many other traditional fossil fuels.
It's used for heating, cooling and production of electricity, and it finds many uses in industry. Increasingly, natural gas is being used in combination with other fuels to decrease pollution.
Natural gas is obtained, sometimes along with oil, by drilling into the earth's crust where pockets of natural gas were trapped hundreds of thousands of years ago. Once the gas is brought to the surface, it is refined to remove impurities like water, other gases and sand.
Burning natural gas produces virtually no atmospheric emissions of sulphur dioxide or small particulate matter. Emissions of carbon monoxide, reactive hydrocarbons, nitrogen oxides and carbon dioxide are also lower than those given off when other fossil fuels are burned.
The secret to the low emissions from natural gas is that it is composed mostly of methane. Methane molecules are made up of one carbon atom and four hydrogen atoms. When it's burned completely, the principal products are carbon dioxide and water vapour.
By comparison, oil and coal have much more complex molecular structures that include more carbon, as well as various sulphur and nitrogen compounds. Coal and industrial fuel oil combustion also produces ash particles, which don't burn at all.
Pros:
Easily transported.
Widely available.
Burns more cleanly than coal and oil (lower CO2 emissions).
Efficient.
Cons:
Even though it burns more cleanly, it still has emissions.
Non-renewable (reserves will be exhausted before coal reserves run out).
Mines and pipelines disrupt ecosystems.
Coal
What is it?
Coal was formed as trees and plants in vast primeval forests decayed. They formed peat bogs that were, over time, buried by soil and rock. As these sediments accumulated, pressure and heat transformed the peat into coal.
It's estimated that up to 2.5 metres of compacted vegetation was required to produce a coal seam 30 centimetres thick. Coal seams 10 or more metres in thickness are common.
In addition to carbon, coals contain hydrogen, oxygen, nitrogen and varying amounts of sulphur. The coal found in Western Canada started forming during the Cretaceous Period (65 - 135 million years ago). The coal deposits of Nova Scotia and New Brunswick were formed during the Carboniferous Period (280 million years ago).
Ontario and Alberta consume the greatest amounts of coal. In 1997, Alberta used 26.2 million tonnes, 47 per cent of the coal consumed in Canada. In the same year, Ontario used 13.8 million tonnes, 25 per cent of Canada's coal use. Four other provinces use coal to generate electricity: Saskatchewan, Manitoba, Nova Scotia and New Brunswick.
When coal is burned for energy, it produces exhaust thick with fly ash, which contains trace metals such as arsenic that pose potential health hazards if inhaled. The exhaust also contains nitrogen oxide, sulphur dioxide, mercury and other harmful pollutants.
Pros:
Currently inexpensive.
Highly efficient.
Plentiful resources still exist.
Cons:
Air pollution (including greenhouse gases, which are thought to lead to global warming).
Burning causes acid rain.
Liberates radioactive elements (in quantities higher than properly operated nuclear power plants).
Non-renewable.
High environmental impact (mining and burning combined).
Nuclear
What is it?
 The Pickering Nuclear Plant east of Toronto. The plant uses Canadian-designed CANDU reactors. (CP Photo/Kevin Frayer)
Nuclear energy is generated in nuclear power plants. Heat is used to boil water into steam, which turns a turbine and drives a generator to produce electricity. The heat comes from the fission of nuclear fuel in a reactor.
Canada Deuterium-Uranium or CANDU reactors are used in Canada. The unique design uses compressed uranium dioxide pellets that are baked at high temperatures. The pellets are loaded into a metal tube that acts as a concentrated source of fuel. A fuel bundle weighs 22 kilograms. A controlled chain reaction in a fuel bundle in a CANDU reactor can produce as much energy as burning about 400 tonnes of coal or 2,000 barrels of oil.
In a CANDU reactor, heavy water (a compound of hydrogen and oxygen that contains more of the hydrogen isotope deuterium than regular water) is used as a moderator. The heavy water and fuel channels are specially positioned to ensure a carefully controlled fission reaction occurs.
Control rods move in and out of the reactor core to adjust the power levels. If needed, the control rods can shut down the chain reaction.
The reactors are highly radioactive so the reactor core is heavily shielded to protect the station's operators. The whole reactor and the primary coolant circuit are in a massive concrete structure to protect the public from any possible radiation releases.
Used fuel bundles are stored in a tank filled with water next to the reactor.
(Sources: Canadian Encyclopedia, Canadian Nuclear FAQ.)
Pros:
Nuclear power plants cause only 0.25 per cent of our exposure to radioactivity, while medical applications such as X-rays contribute 150 times more, according to figures from Germany.
Nuclear plants don't emit carbon dioxide or other greenhouse gases.
More efficient at transforming energy into electricity compared to coal plants.
Uranium reserves are abundant.
Nuclear plants need to be refuelled once a year versus coal plants, which need trainloads of coal every day.
Nuclear Energy Quick Facts
|
In Canada, nuclear power contributes about 14 per cent of the total electricity supply.
In the province of Ontario in 1997 about 48 per cent of the electricity supply was nuclear (along with 27 per cent hydro, 24 per cent fossil, 1 per cent "other").
New Brunswick and Quebec receive about 21 per cent and 3 per cent, respectively, of their supply from nuclear energy.
The energy available in one pound of uranium equals the energy produced by about 1.3 million pounds of coal.
60 per cent of all harmful rays come from natural sources such as cosmic rays and radioactive isotopes; remaining 40 per cent is man-made.
Background radiation of 200 millirems per year comes from everyday objects and outer space; fraction of this comes from nuclear power plants.
(Source: Electric Power in Canada 1997, Natural Resources Canada as quoted in Canadian Nuclear FAQ)
|
Cons:
Many Soviet-designed reactors like Chernobyl are outdated and lack containment features, computer-controlled instruments and modern fire-prevention systems.
Meltdowns result from mechanical and operator failure when coolant escapes into the environment (Three Mile Island accident in Pennsylvania resulted from failure to supply coolant).
Cooling water heats up rivers and reservoirs, causing potential harm to aquatic life.
Chemical processing of uranium ore leaves residues that can lead to radon exposure to the public (but radon risk is less than that of coal).
Cooling effluent would solve thermal pollution problem but is costly.
Distinguishing between military and civilian use of nuclear energy can be difficult (e.g. unemployed nuclear physicists from former Soviet Union could be attracted to countries like Iran, Iraq or North Korea to help develop atomic bombs).
Two types of waste are produced: high level and low level, which vary in how much radiation they produce. High-level waste is stored on site under high security to prevent any unused uranium from falling into the hands of terrorists.
Simplest solution is burial but burial sites could be breached by an earthquake.
Transport of waste poses risk if a traffic accident happens.
Solar
What is it?
 Pat Ricchiuti stands on his solar roof, Tuesday, June 21, 2005, at his P-R Farms packing shed in Clovis, Calif. Ricchiuti's P-R Farms may be installing one of the state's largest privately financed solar energy systems. (AP Photo/Gary Kazanjian)
Photovoltaic (PV) cells convert sunlight directly into electricity. When sunlight strikes a PV cell, electrons are dislodged, creating an electrical current.
Photovoltaic cells already power many small calculators, wrist watches and other gadgets. More complex systems provide electricity to pump water, power communications equipment, light homes and run appliances.
Pros:
PV is often the lowest-cost means to provide electricity, and almost always simplest and cleanest to operate.
Cons:
Setup is currently expensive.
Production is weather-dependent and inefficient.
Large surface areas are required to lay out panels of PV cells.
Oil
What is it?
Oil is a mixture of primarily two elements: carbon and hydrogen.
Oil was formed from the remains of microscopic animals and plants - zooplankton and phytoplankton - that floated on the surfaces of lakes and seas millions of years ago.
The plankton died and drifted downward, mixing with mud and silt. As the centuries passed, layers of sediment covered over the decaying materials. Pressure and temperature increased, transforming the plankton into oil.
Oil naturally seeps to the Earth's surface along fault lines and cracks in rocks.
Crude oil ranges in colour from almost clear to green, amber, brown or black. It may flow like water or creep like molasses. It is described as "sweet" or "sour" depending on the presence or absence of sulphur and other impurities.
Crude oil can be refined into other products like kerosene, gasoline and various other fuel oils.
Oil is most often used as a source for energy, especially for fuels for transportation. It's also used in the manufacture of many products, from prescription drugs to plastics.
Pros:
Currently inexpensive.
Cons:
Non-renewable.
High emissions (smog, contributes to global warming, acid rain).
Chance of spills.
Hydroelectricity
What is it?
Hydro power converts the energy in flowing water into electricity. The amount of electricity generated is determined by how much water is flowing and the amount of "head" created by the dam. "Head" is the distance from the turbines in the power plant to the water's surface. The greater the flow and the height, the more electricity produced.
A typical hydropower plant includes a dam, reservoir, pipes, a powerhouse and an electrical power substation. The dam stores water, pipes carry it from the reservoir to turbines inside the powerhouse. The water rotates the turbines, which drive generators that produce electricity.
The electricity is then transmitted to a substation where transformers increase voltage to allow transmission to homes, businesses and factories.
Pros:
Reliable.
Capable of generating large amounts of power (large plant's typical capacity = 300-400 megawatts).
No emissions.
Renewable.
Currently inexpensive.
Cons:
Dams cause disruption in aquatic and terrestrial ecosystems.
Locations aren't always reliable (drought) or easy to come by.
More expensive than fossil fuels.
Inefficient energy source.
Wind power
What is it?
 Cattle graze near an array of wind turbines at the McBride Lake East location near Fort Macleod, Alta., Thursday, July 10, 2003. (CP Photo/Adrian Wyld)
Mechanical energy is most commonly used for pumping water in rural or remote locations. Wind electric turbines generate electricity for homes and businesses and for sale to utilities.
The most economical application of wind electric turbines is in groups of large machines (700 kW and up), called "wind power plants" or "wind farms."
Wind plants can range in size from a few megawatts to hundreds of megawatts in capacity. Wind power plants are "modular," which means they consist of small individual modules (the turbines) and can easily be made larger or smaller as needed. Turbines can be added as electricity demand grows.
Pros:
No emissions.
Abundant and renewable.
Turbines can be set up without disturbing ecosystems.
Existing technology is relatively high output and affordable.
Cons:
Wind dependent (output proportional to wind speed).
Not feasible for all locations (coastlines and high ridges are best).
Currently expensive.
Relatively heavy land use.
Some say turbines are unsightly and noisy.
Biomass
What is it?
Biofuels are alcohols, ethers, esters and other chemicals made from cellulosic biomass such as herbaceous and woody plants, agricultural and forestry residues, and a large portion of municipal solid and industrial waste.
Biofuels are used to produce electricity, and as fuel for transportation methods. They add fewer emissions to the atmosphere than petroleum fuels and use up wastes for which we currently have no use. Unlike other sources of energy, biofuels are a renewable source.
Bioethanol is the most widely used biofuel. It's added to gasoline to improve vehicle performance and reduce air pollution.
Ethanol is an alcohol, and most of it is made using a process similar to brewing beer. Starch crops are converted into sugars, the sugars are fermented into ethanol, and the ethanol is distilled into its final form. Ethanol made from cellulosic biomass materials instead of starch crops is called bioethanol.
Pros:
Renewable.
Proven technology.
Plentiful sources in waste products (from agriculture, forestry and food processing).
Not dependent on fossil fuels.
Cons:
Burning biomass causes some polluting gases and liquid waste collection.
Fuel Cell
What is it?
A fuel cell works like a battery that doesn't need to be recharged. Fuel cells have two electrodes in an electrolyte. By passing oxygen over one electrode and hydrogen over the other, electricity is generated.
With the help of a catalyst, hydrogen is split into a proton and an electron. As the electrons return to the electrode, an electrical circuit is created.
Conventional heat engines must burn a fuel before the heat can be converted into work. The heat-to-work step is inefficient, but fuel cells don't have this step.
Fuel cells are used to generate electricity onboard spacecraft. On Earth, fuel-cell-powered locomotives, buses and even electricity stations are in the works.
(Sources: Canadian Encyclopedia, Fuel Cell 2000 Web page, How Fuel Cells Work web page)
Pros:
Hydrogen gas could be produced in power plants during non-peak hours and scientists have recently discovered algae produce hydrogen gas under certain conditions.
Cons:
Hydrogen is larger by volume than gasoline so it may pose distribution problems.
Hydrogen gas is not found naturally anywhere; must be produced.
High start-up costs until mass production kicks in.
^TOP
|
|
 |
 MENU |
|
|
| MEDIA: |
|
|
| MORE: |
|
|
|
