energy & power sources

ENERGY & POWER SOURCES

[email protected] www.edutalks.org

Al- Ameen Engg. College 1 www.edutalks.org

• Fossil Fuels• Nuclear Power• Solar Energy• Fuel Cells

Energy Sources and Uses

• Fuel Cells• Biomass• Energy From the Earth’s Forces• Future Power Sources



ENERGY SOURCES AND USES

• Work is the application of force through a distance.• Energy is the capacity to do work.• Power is the rate of flow of energy, or the rate at

which work is done.which work is done.– A small calorie is the metric measure of energy necessary to heat

1 gram of water 1oC, whereas a British Thermal Unit (BTU) is the energy needed to heat 1 pound of water 1oF

– A joule is the amount of work done by a force needed to accelerate 1 kilogram 1 meter per second per second. Another definition for joule is the force of an electrical current of 1 amp/second through a resistance of 1 ohm.



Important Nonrenewable Energy Sources



Worldwide Commercial Energy [email protected] www.edutalks.org


How We Use Energy• What are the commercial uses of energy?

– Industry uses 38%; – Residential and commercial buildings use 36%; and,– Transportation uses 26%.

• Half of all energy in primary fuels is lost during conversion to more useful formsm while being shipped or during use.– Nearly two-thirds of energy in coal being burned to generate

electricity is lost during thermal conversion in the power plant. Another 10% is lost during transmission and stepping down to household voltages.

• Natural gas is the most efficient fuel.– Only 10% of its energy content is lost during shipping and

processing. Ordinary gas-burning furnaces are about 75% efficient. High-economy furnaces can be 95% efficient.



PART 1: FOSSIL FUELS• Fossil fuels are organic chemicals created by living organisms that were buried

in sediments millions of years ago and transformed to energy-rich compounds.• Because fossil fuels take so long to form, they are essentially nonrenewable

resources.

Coal Oil Natural Gas



Oil

Coal

Natural Gas



Coal – What is it?

• Solid fossil fuel formed in several stages • Land plants that lived 300-400 million years

ago• Subjected to intense heat and pressure over

many millions of years• Mostly carbon, small amounts of sulfur



Coal Formation and Types



OIL and NATURAL GAS

• Accumulations of dead marine organisms on the ocean floor were covered by sediments.

• Muddy rock gradually forms rock (shale) containing dispersed oil.containing dispersed oil.

• Sandstone formed on top of shale, thus oil pools began to form.

• Natural gas often forms on top of oil.• Primary component of natural gas is

methane



PART 2: NUCLEAR POWER

• President Dwight Eisenhower, 1953, “Atoms for Peace” speech.– Eisenhower predicted that nuclear-powered electrical generators would

provide power “too cheap to meter.”– Between 1970-1974, American utilities ordered 140 new reactors, but

100 were subsequently canceled.100 were subsequently canceled.

• Nuclear power now produces only 7% of the U.S. energy supply.

• Construction costs and safety concerns have made nuclear power much less attractive than was originally expected. – Electricity from nuclear power plants was about half the price of coal

in 1970, but twice as much in 1990.



How Do Nuclear Reactors Work• The common fuel for nuclear reactors is U235 that occurs

naturally (0.7%) as a radioactive isotope of uranium.• U235 is enriched to 3% concentration as it is processed into

cylindrical pellets (1.5 cm long). The pellets are stacked in hollow metal rods (4 m long).

• 100 rods are bundled together into a fuel assembly. Thousands of these fuel assemblies are bundled in the reactor core.

• When struck by neutrons, radioactive uranium atoms undergo nuclear fission, releasing energy and more neutrons. This result nuclear fission, releasing energy and more neutrons. This result triggers a nuclear chain reaction.

• This reaction is moderated in a power plant by neutron-absorbing solution (Moderator Heavy Water (D2O)).

• Control Rods composed of neutron-absorbing material are inserted into spaces between fuel assemblies to control reaction rate.

• Water or other coolant is circulated between the fuel rods to remove excess heat.



Nuclear fission occurs in the core of a nuclear reactor



Kinds of Reactors

• 70% of nuclear power plants are pressurized water reactors (PWRs). Water is circulated through the core to absorb heat from fuel rods. The heated water is then pumped to a steam generator where it heats a secondary loop. Steam from the secondary loop drives a high-speed turbine making electricity.

• Both reactor vessel and steam generator are housed in a special containment building. This prevents radiation from escaping and provides extra security in case of accidents. Under normal operations, a PWR releases little radioactivity.



Reactor [email protected] www.edutalks.org


Radioactive Waste Management

• Production of 1,000 tons of uranium fuel typically generates 100,000 tons of tailings and 3.5 million liters of liquid waste.– Now approximately 200 million tons of radioactive waste exists in

piles around mines and processing plants in the U.S.• About 100,000 tons of low-level waste (clothing) and about 15,000

tons of high-level (spent-fuel) waste in the US.– For past 20 years, spent fuel assemblies have been stored in deep

water-filled pools at the power plants. (designed to be temporary).water-filled pools at the power plants. (designed to be temporary).– Many internal pools are now filled, and a number plants are storing

nuclear waste in metal dry casks outside.• A big problem associated with nuclear power is the disposal of

wastes produced during mining, fuel production, and reactor operation.– U.S. Department of Energy announced plans to build a high-level

waste repository near Yucca Mountain Nevada in 1987.– Cost is $10-35 billion, and earliest opening date is 2010.– This allows the government to monitor & retrieve stored uranium.



•Distributional Surcharges–Small charge levied on all utility customers to help finance research and development.

•Renewable Portfolio–Mandate minimum percentage of energy from renewable sources.

Promoting Renewable Energy

–Mandate minimum percentage of energy from renewable sources.•Green Pricing

–Allow utilities to profit from conservation programs and charge premium prices for energy from renewable sources.



PART 3: SOLAR ENERGY

• Photosynthesis• Passive solar heat is using

absorptive structures with no moving parts to gather and hold heat. Greenhouse design

• Active solar heat is when a system pumps a heat-absorbing medium through absorbing medium through a collector, rather than passively collecting heat in a stationary object. Water heating consumes 15% of US domestic energy budget.

Mean solar energy striking the upper atmosphere is 1,330 watts per square meter. The amount reaching the earth’s surface is 10,000 times > all commercial energy used annually. Until recently, this energy source has been too diffuse and low intensity to capitalize for electricity production.



High-Temperature Solar Energy

•Parabolic mirrors (left) are curved reflective surfaces that collect light and focus it onto a concentrated point. It involves two techniques:

–Long curved mirrors focus on a central tube containing a on a central tube containing a heat-absorbing fluid.–Small mirrors arranged in concentric rings around a tall central tower track the sun and focus light on a heat absorber on top of the tower where molten salt is heated to drive a steam-turbine electric generator.



Photovoltaic Solar Energy

• During the past 25 years, efficiency of energy capture by photovoltaic cells has increased from less than 1% of incident light to more than 10% in field conditions, and 75% in laboratory conditions.– Invention of amorphous silicon collectors has allowed

production of lightweight, cheaper cells.

• Photovoltaic cells capture solar energy and convert it directly to electrical current by separating electrons from parent atoms and accelerating them across a one-way electrostatic barrier.– Bell Laboratories - 1954

• 1958 - $2,000 / watt• 1970 - $100 / watt• 2002 - $5 / watt



Photovoltaic energy -solar energy converteddirectly to electricalcurrent



Transporting & Storing Electrical Energy

• Electrical energy storage is difficult and expensive.– Lead-acid batteries are

heavy and have low energy density.

• Typical lead-acid battery • Typical lead-acid battery sufficient to store electricity for an average home would cost $5,000 and weigh 3-4 tons.

– Pumped-Hydro Storage– Flywheels



PART 4: FUEL CELLS

• Fuel cells use ongoing electrochemical reactions to produce electrical current

• Fuel cells provide direct-current electricity as long as supplied with hydrogen and oxygen.

• Hydrogen is supplied as pure gas, or a reformer can be used to strip hydrogen from other fuels.

• Fuel cells run on pure oxygen and hydrogen produce only drinkable water and radiant heat.

• Reformer releases some pollutants, but far below conventional fuel levels.

• Fuel cell efficiency is 40-45%.• Positive electrode (cathode) and

negative electrode (anode) separated by electrolyte which allows charged atoms to pass, but is impermeable to electrons. Electrons pass through external circuit, and generate electrical current.



PART 5: BIOMASS



Fuelwood



Fuelwood Crisis in Less-Developed Countries

• About 40% of the world’s population depends on firewoodand charcoal as their primary energy source.

• Supplies diminishing• Supplies diminishing• Half of all wood

harvested worldwide is used as fuel.



Using BIOGAS As a Fuel



Alcohol from Biomass• Ethanol (grain alcohol) production could be a solution

to grain surpluses but thermodynamic considerations question it being practical on a sustainable basis. Gasohol (a mixture of gasoline and alcohol) reduces CO emissions when burned in cars. Ethanol raises octane ratings, and helps reduce carbon monoxide octane ratings, and helps reduce carbon monoxide emissions in automobile exhaust.

• Methanol (wood alcohol)• Both methanol and ethanol make good fuel for fuel

cells.



PART 6: ENERGY FROM EARTH'S FORCES

HydropowerWindGeothermalTidalWave

• Water power produces 25% of the world’s electricity and it is clean, renewable energy.

• Dams cause social and ecological damage.



• Hydropower– By 1925, falling water generated 40% of world’s electric power.

• Hydroelectric production capacity has grown 15-fold, but fossil fuel use has risen so rapidly that now hydroelectric only supplies one-quarter of electrical generation.

• Total world hydropower potential estimated about 3 million MW.– Currently use about 10% of potential supply.

• Energy derived from hydropower in 1994 was equivalent to 500 million tons of oil. Much of recent hydropower development is in very large dams.

• Drawbacks to dams include:• Drawbacks to dams include:– Human Displacement– Ecosystem Destruction– Wildlife Losses– Large-Scale Flooding Due to Dam Failures– Sedimentation– Herbicide Contamination– Evaporative Losses– Nutrient Flow Retardation



The theory is to build a dam on a large river that has a large drop in elevation. The dam stores lots of water behind it in the reservoir. Near the bottom of the dam wall there is the water intake. Gravity causes it to fall through the penstock inside the dam. At the end of the penstock there is a turbine propeller, which is turned by the moving water. The shaft from the turbine goes up into the generator, which produces the power.



Wind Energy

• Wind power is extracted from air flow using wind turbines or sails to produce mechanical or electrical power. Windmills are used for their mechanical power, windpumps for water pumping, and sails to propel ships. Wind power as an alternative to fossil fuels, is plentiful, renewable, widely distributed, clean, produces no greenhouse gas emissions during operation, and uses little land.



Wind [email protected] www.edutalks.org


Geothermal Energy

This energy source involves the use of high-pressure, high-temperature steam fields that exist below the earth’s surface.



Tidal & Wave Energy

•Ocean tides and waves contain enormous amounts of energy that can be harnessed.

–Tidal Station - Tide flows through turbines, creating electricity. It requires a high tide/low-requires a high tide/low-tide differential of several meters.–Main worries are saltwater flooding behind the dam and heavy siltation.–Stormy coasts with strongest waves are often far from major population centers.



Tidal & Wave [email protected] www.edutalks.org


The best way to visualise a floating device is like a giant snake that floats on the water. The floating device is made up of large metal tubes that are connected together by hinges. The group of tubes is attached to the sea bed using cables, so the device is fixed in one place.

As the swell passes underneath the snake, one tube will move upward and the tube that it is connected to will move downward. This movement is repeated down the snake of metal tubes as the wave passes underneath.The hinges between the tubes are connected to a pump. This pumps oil through a hydraulic motor as the tubes move, which in turn generates electricity as it spins around.The electricity generated can be taken to land via cables attached to the seabed.



PART 7: FUTURE POWER SOURCES



ANTIMATTERIt is the twin of matter, made up of antiparticles that have the same mass as ordinary matter but with opposite atomic properties known as spin and charge. When the opposed particles meet, they annihilate each other and release tremendous amounts of energy as dictated by Einstein’s famous equation, E=mc2.


TIDAL TURBINES & TIDAL ENERGY

An individual tidal turbine will generate most electricity when the tide is running fastest. This will be at approximately the mid point between high and low tides.



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