Lecture 4 Energy Sources

Energy Sources

Core Case Study: Conventional Oil Supplies

• Oil is a major energy supplier.
• Key questions:
  • How much oil is left?
  • When will we run out of oil?
• Three options for addressing oil depletion:
  • Look for more oil.
  • Reduce oil use.
  • Use other energy sources.

Predictions of Oil Depletion

• Past predictions of the world running out of oil:
  • 1914: U.S. Bureau of Mines predicted oil depletion in 10 years.
  • 1939 & 1950: U.S. Department of the Interior predicted oil depletion in 13 years.
  • 1973: Paul Erlich, Limits to Growth, predicted oil and other fossil fuel depletion by 1990.
  • 2002: Paul Erlich, Beyond the Limit, predicted oil depletion by 2030 and other fossil fuels by 2050.
  • 2021: International Energy Outlook stated the world's oil supply would meet global energy demand until at least 2050.

Major Sources of Energy

• Non-Renewable Energy (82%)
  • Fossil Fuel Oil: 33%
  • Coal: 22%
  • Natural Gas: 21%
  • Nuclear Power: 6%
• Renewable Energy (18%)
  • Biomass: 11%
  • Hydropower: 4.5%
  • Geothermal, Solar, Wind: 2.5%
• Fossil fuels supply most of our commercial energy.
  • Three-quarters of the world's commercial energy.
• Nonrenewable nuclear fuel and renewable sources provide one-quarter.
  • Includes direct solar energy and indirect solar energy (wind, hydropower, biomass, etc.).
• Net energy:
  • Amount of high-quality usable energy available from a resource after subtracting the energy needed to make it available.

Energy Sources: Conventional vs. Non-Conventional

• Non-Conventional Energy Sources:
  • Resources still in the process of development over the past few years.
  • Examples: Solar, Wind, Tidal, Biogas, Biomass, Geothermal.
• Conventional Energy Sources:
  • Sources of energy currently in use for a long time.
  • Examples: Coal, Petroleum, Natural Gas, Nuclear, and Water power (Hydropower).

Conventional vs. Non-Conventional Sources of Energy

Natural Capital: Important Nonrenewable Energy Resources

• Important nonrenewable energy resources that can be removed from the Earth’s crust:
  • Coal
  • Oil
  • Natural gas
  • Some forms of geothermal energy
  • Nonrenewable uranium ore

Global Energy Systems Transition (% of market)

• Historical energy source usage:
  • Wood dominated until 1850.
  • Coal increased from 1850 to 1950.
  • Oil increased from 1900 to 2000.
  • Natural gas increasing.
  • Hydrogen - future.

Advantages and Disadvantages of Oil

• Conventional Oil:
  • Advantages:
    • Currently abundant.
    • High net energy yield.
    • Relatively inexpensive.
  • Disadvantages:
    • Causes air and water pollution.
    • Releases greenhouse gases to the atmosphere.
• Heavy Oils (from oil sand and oil shale):
  • Advantages:
    • Exist in potentially large supplies.
  • Disadvantages:
    • Have low net energy yields.
    • Higher environmental impacts than conventional oil.

Dependence on Oil

• Fossil fuels:
  • Crude oil and natural gas.
  • Found deep within the Earth’s crust on land or under the seafloor.
  • Dispersed in pores and cracks in underground rock formations.
• Oil extraction and refining:
  • Drill a well vertically or horizontally into the deposit.
  • Oil, drawn by gravity (pressure difference) out of the rock pores.
  • Flows into the bottom of the well and is pumped.
  • Takes energy and money to find, drill, and pump.
• Petrochemicals:
  • Products of oil distillation.
  • Raw materials.

Oil Extraction and Recovery

• Primary recovery:
  • Underground pressure in the oil reservoir is sufficient to force the oil and gas to the surface.
• Secondary recovery:
  • Over the lifetime of a well, the pressure falls.
  • When there is insufficient underground pressure to force the oil to the surface, external energy is supplied by injecting fluids to increase reservoir pressure by water and gas injection.
• Enhanced recovery:
  • Steam is injected where the oil is thicker and heavier than normal crude oil to increase the mobility of the oil in order to increase extraction.

Light vs. Heavy Oil

• Light oil:
  • Petroleum, or crude oil, also known as conventional, or light oil
  • Comprises 30% of the world’s estimated supply of oil.
• Heavy oil:
  • Unconventional heavy oil
  • Thick
  • 70% of the world’s estimated supply of oil
  • Some thick oil is left behind in wells
  • Some is extracted from deposits of tar sands and oil shale rock
  • Takes considerable energy and money to extract, which reduces its net energy yield.

Refining Crude Oil

• Fractional distillation:
  • Process by which oil refineries separate crude oil into different, more useful hydrocarbon products.
  • Separation is based on differences in molecular weight of different components of the crude oil.
  • Different molecular weights → different boiling points.
  • Lighter components boil at lower temperatures.
  • As weight increases, boiling point increases, and thus compounds that are heavier are separated later during the process.

Trade-Offs: Conventional Oil

• Advantages:
  • Ample supply for several decades
  • High net energy yield but decreasing
  • Low land disruption
  • Efficient distribution system
• Disadvantages:
  • Water pollution from oil spills and leaks
  • Environmental costs not included in market price
  • Releases $CO_2$ and other air pollutants when burned
  • Vulnerable to international supply interruptions

Heavy Oil from Sand

• Oil sand, tar sand:
  • Mixture of sand, clay, water, and bitumen.
  • Bitumen: a thick, sticky, tarlike heavy oil with a high sulfur content.
• Extraction:
  • Serious environmental impact: air, water, wildlife, and climate.
  • Low net energy yield.
  • Is it cost-effective?
  • Oil sand is mixed with hot water and steam to extract the bitumen.

Oil Shales: Heavy Oil from Oily Rocks

• Oil shales (Oily rocks) contain kerogen; a solid combustible mixture of hydrocarbons must be heated to increase its flow rate processed to remove sulfur, nitrogen, and other impurities.
• Low net energy yield.

Trade-Offs: Heavy Oils from Oil Shale and Tar Sand

• Advantages:
  • Large potential supplies
  • Easily transported within and between countries
  • Efficient distribution system in place
• Disadvantages:
  • Low net energy yield
  • Releases $CO_2$ and other air pollutants when produced and burned
  • Severe land disruption and high water use

Natural Gas

• Conventional natural gas:
  • More plentiful than oil
  • High net energy yield
  • Fairly low cost
  • Lowest environmental impact of all fossil fuels
  • Mixture of gases, more than half is $CH_4$ (50-90%)
• Liquefied petroleum gas (LPG):
  • Propane and butane gases are liquefied under high pressure
• Liquefied natural gas (LNG):
  • Low net energy yield
  • Natural gas that has been cooled down to liquid form for ease and safety of non-pressurized storage or transport, about –162 ºC
  • Transported via refrigerated tanker ships

Natural Gas: Advantages and Disadvantages

• Will natural gas be the bridge fuel helping us make the transition to a more sustainable energy future?

Trade-Offs: Conventional Natural Gas

• Advantages:
  • Ample supplies
  • High net energy yield
  • Emits less $CO_2$ and other pollutants than other fossil fuels
• Disadvantages:
  • Low net energy yield for LNG
  • Releases $CO_2$ and other air pollutants when burned
  • Difficult and costly to transport from one country to another

Advantages and Disadvantages of Coal

• Conventional coal:
  • Very plentiful
  • High net energy yield
  • Low cost
  • But it has a very high environmental impact.
  • Severely degrades land and pollutes water and air.
  • When burned, it severely pollutes the air

Stages in Coal Formation

• Process occurs over millions of years with increasing heat and carbon content.
  • Peat: Partially decayed plant matter in swamps and bogs; low heat content (not a coal).
  • Lignite: (brown coal) Low heat content; low sulfur content; limited supplies in most areas.
  • Bituminous: (soft coal) Extensively used as a fuel because of its high heat content and large supplies; normally has a high sulfur content.
  • Anthracite: (hard coal) Highly desirable fuel because of its high heat content and low sulfur content; supplies are limited in most areas.

Science: Coal-Burning Power Plant

• Coal-fired plants produce electricity by burning coal in a boiler to produce steam.
• The steam produced, under tremendous pressure, flows into a turbine, which spins a generator to create electricity.
• The steam is then cooled, condensed back into water, and returned to the boiler to start the process over.

Environmental Impacts of Coal Mining

• Surface mining of coal:
  • Completely eliminates existing vegetation
  • Destroys the genetic soil profile
  • Displaces or destroys wildlife and habitat
  • Degrades air quality
  • Alters current land uses
  • Scarred landscape with no scenic value
  • Movement, storage, and redistribution of soil during mining.
  • Disrupt the community of soil microorganisms.

Coal: A Plentiful but Dirty Fuel

• World’s most abundant fossil fuel
• Environmental costs of burning coal:
  • Severe air pollution
  • Sulfur released as $SO_2$
  • Large amount of Soot (black powdery substance consisting largely of amorphous carbon)
  • $CO_2$
  • Trace amounts of mercury (Hg) and radioactive materials

Trade-Offs: Coal

• Advantages:
  • Ample supplies in many countries
  • High net energy yield
  • Low cost when environmental costs are not included
• Disadvantages:
  • Severe land disturbance and water pollution
  • Fine particle and toxic mercury emissions threaten human health
  • Emits large amounts of $CO_2$ and other air pollutants when produced and burned

Top 3 Countries by Resource (Fall 2024 Estimation)

• Coal: China/USA, USA/Russia, India/Australia
• Natural Gas: Russia/USA, Iran/Russia, Qatar/Iran
• Light Oil: KSA/USA, Kuwait/KSA, USA/Russia
• Tar Sands: Canada, Venezuela/Kazakhstan, USA/Russia
• Oil Shale: KSA/US, US/Russia/Estonia, Russia/China/Brazil

Nuclear Energy

• Low environmental impact, very low accident risk, but high costs.
• Low net energy yield, long-lived radioactive wastes, vulnerability to sabotage, and the potential for spreading nuclear weapons technology have limited its use.

How a Nuclear Fission Reactor Works

• Controlled nuclear fission reaction in a reactor.
• Fueled by uranium ore and packed as pellets in fuel rods and fuel assemblies.
• Water is the usual coolant
• Containment shell around the core for protection.
• Water-filled pools or dry casks for storage of radioactive spent fuel rod assemblies.

Management of Spent Fuel Rods

• After 3 or 4 years in a reactor, spent fuel rods are removed and stored in water.

Radioactivity of Nuclear Waste

• Diminishes with time.
• Waste must be isolated for sufficient time to reduce radioactivity below acceptable limits.
• Days to years (for short-lived isotopes).
• Spent fuel rods from nuclear power plants:
  • 5 years of cooling (up to 10 years in some cases).
  • Wastes must be stored safely for thousands of years.
• A major environmental concern related to nuclear power is the creation of radioactive wastes such as spent (used) reactor fuel. These materials can remain radioactive and dangerous to human health for thousands of years.

Example of Nuclear Waste Storage

• Dry cask storage is a method of storing high-level radioactive waste, such as spent nuclear fuel (after the spent rods have cooled already).

The Nuclear Fuel Cycle

• Steps:
  1. Mine the uranium
  2. Process the uranium to make the fuel
  3. Use it in the reactor
  4. Safely store the radioactive waste
  5. Decommission the reactor

What Happened to Nuclear Power?

• Slowest-growing energy source; expected to decline more.
• Why?
  • Economics
  • Poor management
  • Low net yield of energy of the nuclear fuel cycle
  • Safety concerns
  • Need for greater government subsidies
  • Concerns of transporting uranium

Case Study: Three Mile Island Accident (U.S.)

• March 29, 1979, near Harrisburg, PA, U.S.
• Nuclear reactor lost its coolant, leading to partial uncovering and melting of the radioactive core.
• Unknown amounts of radioactivity escaped.
• People fled the area.
• Increased public concerns for safety.
• Led to improved safety regulations in the U.S.

Case Study: Chernobyl Accident (Ukraine)

• April 26, 1986, in Chernobyl, Ukraine
• Series of explosions caused the roof of a reactor building to blow off
• Partial meltdown and fire for 10 days
• Huge radioactive cloud spread over many countries and eventually the world
• 350,000 people left their homes
• Effects on human health, water supply, and agriculture

Trade-Offs: Conventional Nuclear Fuel Cycle

• Advantages:
  • Low environmental impact (without accidents)
  • Emits 1/6 as much $CO_2$ as coal
  • Low risk of accidents in modern plants
• Disadvantages:
  • Very low net energy yield and high overall cost
  • Produces long-lived, harmful radioactive wastes
  • Promotes spread of nuclear weapons

Trade-Offs: Coal vs. Nuclear

Radioactive Wastes

• Dealing with Radioactive Wastes Produced by Nuclear Power: Difficult Problem
• High-level radioactive wastes:
  • Must be stored safely for 10,000–240,000 years
• Where to store it?
  • Deep burial: safest and cheapest option
  • Would any method of burial last long enough?
  • There is still no facility

Nuclear Fusion

• Power of the future?
• Still in the laboratory phase, after 50 years of research and $34 billion dollars.
• 2006: U.S., China, Russia, Japan, South Korea, and European Union.
• Will build a large-scale experimental nuclear fusion reactor by 2040.

Top 3 Countries Nuclear Energy (Fall 2024 Estimation)

• US, China - France, Russia
• Site Location Examples
  • Cordova (50 miles)
  • International distance approximately 26 km

Renewable Energy

• Energy produced from sources that do not deplete or can be replenished within a human’s lifetime.
• Most common examples:
  • Wind
  • Solar
  • Geothermal
  • Biomass
  • Hydropower

Comparison Chart: Incandescent vs. CFL vs. LED

• Efficiency is an Important Energy Resource

Reducing Energy Waste

• Advantages of reducing energy waste:
  • Quick and clean
  • Cheapest way to provide more energy
  • Reduce pollution and degradation
  • Slow global warming
  • Increase economic and national security

More Energy-Efficient Vehicles

• Super-efficient and ultralight cars
• Gasoline-electric hybrid car
• Plug-in hybrid electric vehicle
• Energy-efficient diesel car
• Electric vehicle with a fuel cell (Hydrogen Power)

Saving Energy and Money in Existing Buildings

• Insulate and plug leaks:
  • One-third of heated air in typical homes escapes: air leaks, and sealing Insulate and plug.
• Use energy-efficient windows:
  • Highly efficient super-windows that have the insulating effect of a window with 3 to 20 panes cut expensive heat losses.
• Stop other heating and cooling losses:
  • Leaky heating and cooling ducts; white or light-colored roofing or living roofs.
• Heat houses more efficiently: Superinsulation

Energy Efficiency in Existing Buildings

• Heat water more efficiently: Solar heaters
• Use energy-efficient appliances:
  • Refrigerators
  • Electric stoves
• Use energy-efficient lighting

Renewable Energy

• Is it a solution?
• We Can Use Renewable Energy in Place of Nonrenewable Energy Sources
  • Solar energy
  • Geothermal energy
• Benefits of shifting toward a variety of locally available renewable energy resources

Solar Energy

• “Solar” is the Latin word for sun, and solar power is the energy from the sun.
• Solar energy technology comprises two different categories, thermal conversion and photo-conversion.
  • Photovoltaic: Sunlight directly converts into electrical energy.
  • Thermal Energy: Sunlight focuses to thermal receptors and converts water to steam, then turbines rotary power produces electricity.

Solar Techniques and Applications

• Solar water heating
• Solar air conditioning
• Solar drying
• Solar green-house
• Solar desalination
• Solar refrigeration
• Solar cooking
• Solar furnace
• Solar electricity (Photovoltaic)
• Solar electricity (Thermal)

Advantages of Solar Energy

• Solar energy is free
• Solar energy does not cause pollution
• It can be used in remote areas where it is too expensive to extend electricity power grid.
• Calculators and other low power consuming devices can be powered by solar energy effectively.

Passive and Active Solar Heating Systems

• Heat water and buildings effectively.
• Costs of using direct sunlight to produce high-temperature heat and electricity are coming down.

Solar Thermal Systems

• Central receiver system for widespread use.
• High cost.
• Low net energy yields.
• Limited suitable sites.
• Sunny, desert sites.

Trade-Offs: Solar Energy for High-Temperature Heat and Electricity

• Advantages:
  • Moderate environmental impact
  • No direct emissions of $CO_2$ and other air pollutants
    • Lower costs with natural gas turbine backup
• Disadvantages:
  • Low net energy and high costs
  • Needs backup or storage system on cloudy days
  • High water use for cooling

Photovoltaic (PV) Cells (Solar Cells)

• Convert solar energy to electric energy
• Thin wafers of silicon (Si) or with trace amounts of metals that allow them to produce electricity free energy?
• Solar-cell power plants
• Many examples around the world
• Key problem: High cost of producing electricity
• Will the cost drop with:
  • Mass production
  • New designs
  • Nanotechnology

Photovoltaic: Direct Conversion of Light into Electricity

• Photovoltaics is the direct conversion of light into electricity at the atomic level.
• Some materials exhibit a property known as the photoelectric effect that causes them to absorb photons of light and release electrons.
• When these free electrons are captured, an electric current results that can be used as electricity.

Trade-Offs: Solar Cells

• Advantages:
  • Moderate net energy yield
  • Little or no direct emissions of $CO_2$ and other air pollutants
  • Easy to install, move around, and expand as needed
  • Competitive cost for newer cells
• Disadvantages:
  • Need access to sun
  • Need electricity storage system or backup
  • High costs for older systems but decreasing rapidly
  • Solar-cell power plants could disrupt desert ecosystems

Hydroelectricity

• Electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water.
• It is the most widely used form of renewable energy, accounting for 16 percent of global electricity generation.

Electricity from the Water Cycle

• Over dams, tidal flows, ocean waves
• Water flowing, environmental concerns
• Limited availability of suitable sites.
• Limited use of these energy resources used to generate electricity
• World’s leading renewable energy source used to produce electricity
  • Hydroelectric power
  • Micro-hydropower generators

Trade-Offs: Large-Scale Hydropower

• Advantages:
  • Moderate to high net energy
  • Large untapped potential
  • Low-cost electricity
  • Low emissions of $CO_2$ and other air pollutants in temperate areas
• Disadvantages:
  • Large land disturbance and displacement of people
  • High $CH_4$ emissions from rapid biomass decay in shallow tropical reservoirs
  • Disrupts downstream aquatic ecosystems

Small Hydro Power (SHP)

• Small hydropower can provide clean, renewable, and relatively inexpensive energy.
• Unlike large hydropower schemes, small hydropower does not necessitate a reservoir.
• They can be constructed in any location where there is enough water flow and head to make energy generation viable.
• Since no reservoir is created on the upstream, there is minimal impact on nearby communities with respect to displacement.

Advantages of SHP

• SHP is a clean energy source, producing no water or air pollution
• As a non-consumptive water use, small hydropower is a renewable energy source.
• There is minimal impact on the environment.
• Long useful life and low running cost

Disadvantages of SHP

• To be economical, energy consumers need to be located near the hydropower scheme.
• Seasonal variation in stream flow causes variation and disturbance in energy supply.
• The stream flow limits the power generation

Energy Derived from Oceans

• Marine energy refers to the energy carried by ocean waves, tides, salinity, and ocean temperature differences.
• The movement of water in the world’s oceans creates a vast store of kinetic energy, or energy in motion.
• This energy can be harnessed to generate electricity to power homes, transport, and industries.

Tides and Waves for Electricity

• Produce electricity from flowing water
• Ocean tides and waves
• So far, power systems are limited
• Disadvantages:
  • Few suitable sites
  • High costs
  • Equipment damaged by storms and corrosion

Wind Energy

• Using Wind to Produce Electricity Is an Important Step toward Sustainability
• Wind: indirect form of solar energy
• Captured by turbines and converted into electrical energy
• Wind farms on land and offshore
• If environmental costs of energy resources are included in market prices wind energy is the least expensive and least polluting way to produce electricity

Wind Turbines

• We can use the energy in the wind by building a tall tower with a large propeller on the top.
• The wind blows the propeller round, which turns a generator to produce electricity.

Electricity Generation from Wind

• When wind flows through the blades of a turbine, they rotate and spin, powering a rotor inside the generator to produce electricity.
• Multiple turbines function independently.
• Electricity from each turbine flows through cables and combines with energy from other turbines, is power conditioned and then distributed.

Advantages of Wind Energy

• Wind energy is a renewable resource, so it will never run out
• Has little direct effect on the environment as there has NO green house gas (GHG) problems
• Modern turbines available up to 1MW and wind farms of 100 to 150 MW installed.
• Individual turbines are repairable and no need of farm shutdown.
• The farm land can be used for agriculture or farming activities – means eco-friendly and promotes tourism.

Disadvantages of Wind Energy

• It covers large areas usually on ridges and hill tops.
• They are noisy.
• Need huge amount of cabling and complex Electrical Engineering technology.
• Generation of waste materials from damaged wind mills.
• Regular monitoring and recurring repair of electronics.

Trade-Offs: Wind Power

• Advantages:
  • Moderate to high net energy yield
  • Widely available
  • Low electricity cost
  • Little or no direct emissions of $CO_2$ and other air pollutants
  • Easy to build and expand
• Disadvantages:
  • Needs backup or storage system when winds die down
  • Visual pollution for some people
  • Low-level noise bothers some people
  • Can kill birds if not properly designed and located

Biomass

• Biomass fuels come from things that once lived: wood products, dried vegetation, crop residues, aquatic plants, and even garbage.
• Plants used up a lot of the sun's energy to make their own food (photosynthesis).
• They stored the foods in the plants in the form of chemical energy.
• As the plants died, the energy is trapped in the residue.

Biomass Process

1. Energy from the sun is transferred and stored in plants. When the plants are cut or die, wood chips, straw and other plant matter is delivered to the bunker.
2. This is burned to heat water in a boiler to release heat energy (steam).
3. The energy/power from the steam is directed to turbines with pipes.
4. The steam turns a number of blades in the turbine and generators, which are made of coils and magnets.
5. The charged magnetic fields produce electricity, which is sent to homes by cables.

Biomass Categories

• Biomass in traditional form (Wood and Agricultural residue is burnt to produce energy).
• Biomass in non-traditional form (Biomass converted to ethyl alcohol and methyl alcohol to be used as liquid fuels in engine).
• Biomass for domestic use: Organic waste is decomposed anaerobically to produce a mixture of gases (Biogas) namely methane, Carbon dioxide, Hydrogen Sulfide etc.
  *Biogas is a good biofuel used for cooking and lighting).

Methods for Converting Biomass to Energy

• Burning: Direct burning of biomass is the simple method of energy production. Wood and other forms of biomass burnt for thousands of years, to warm, to cook food, and other tools.
• Alcohol Fermentation: In alcohol fermentation, the starch in organic matter is converted to sugar. This sugar is then fermented by yeast. The resulting ethanol is distilled and then blended with another fuel. The end product “Gasohol” has been used successfully in various countries as an alternative to regular gasoline.

Types of Liquid Biofuels

• Liquid biofuels:
  • Biodiesel (From Vegetable oil).
  • Bio-Ethanol (from agricultural and vegetable waste).
• Major advantages over gasoline and diesel fuel produced from oil
  • Biofuel crops can be grown almost anywhere
  • No net increase in $CO_2$ emissions if managed properly
• Biggest producers of biofuel
  • Brazil
  • The United States
  • The European Union
  • China

Other Methods for Converting Biomass to Energy

• Anaerobic Digestion: Anaerobic digestion converts biomass, especially waste products, into methane and carbon dioxide. The biomass is mixed with water and stored in an airtight tank.
• Pyrolysis: Pyrolysis involves the heating of biomass in the absence of oxygen. Biomass such as wood or agriculture waste is heated at or above 500°C and allowed to decompose into gas and charcoal. The major advantage of pyrolysis is that carbon dioxide is not produced and produces ethylene, many forms of carbon, and other chemicals from petroleum, coal, and even wood.

Solid Biomass as an Energy Source

• Solid biomass:
  • A renewable resource, but burning it faster than it is replenished results in a net gain in atmospheric greenhouse gases.
  • Creating biomass plantations degrades soil biodiversity.
• Liquid biofuels (Example: Bio-Ethanol):
  • Derived from biomass and can be used in place of gasoline and diesel fuels.
  • Creating biofuel plantations could degrade soil and biodiversity and increase food prices and greenhouse gas emissions.

Trade-Offs: Biodiesel

• Advantages
  • Reduced CO and CO₂ emissions
  • High net energy yield for oil palm
  • Reduced hydrocarbon emissions
  • Better mileage(up to 40%)
• Disadvantages
  • Increased NOx emissions and smog
  • Low net energy yield for soybean crops
  • Competes with food for cropland
  • Clearing natural areas for plantations reduces biodiversity and increases atmospheric CO₂ levels

Ethanol Production

• Can be made from plants such as sugarcane, corn, and switchgrass, and from agricultural, forestry, and municipal wastes.
• Conversion involves converting plant starches into simple sugars.
• These sugars are then processed to produce ethanol.

Cooling Buildings Naturally

• Technologies available:
  • Superinsulation and high-efficiency windows
  • Light-colored roof
  • Reflective insulating foil in an attic
  • Geothermal pumps
  • Plastic earth tubes underground

Geothermal Energy

• The term Geothermal originates from two Geek words 'GEO' and 'THERM'. The Greek word ‘geo’ means the earth and ‘thermal’ means heat. Hot water trapped below the surface acts as a geothermal reservoir

Geothermal Electricity

• One way of producing electricity from geothermal energy is by drilling wells into the geothermal reservoirs. The hot water that rises emerges at the surface as steam.
• The steam is used to drive turbines producing electricity. If the water is not hot enough to produce steam, it can still be used to heat homes and businesses, saving gas/electricity.

Utilizing Geothermal Energy

• Heat stored in:
  • Soil
  • Underground rocks
  • Fluids in the earth’s mantle
• Geothermal energy:
  • Great potential for supplying many areas with heat and electricity.
  • Low environmental impact
  • Locations are limited
• Geothermal energy issues:
  • High cost of tapping large-scale hydrothermal reservoirs
  • Geothermal reservoirs could be depleted
  • Hot, dry rock as another potential source of geothermal energy

Noise Pollution from Geothermal Energy

• Geothermal energy requires pumps to move the water that provides the heating and cooling which means that some noise pollution may be generated in nearby spaces (when used in a residence there is no noise pollution