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Energy: Alternative Energy

presentation for the Alternative Energy lesson of the Environmental Science course. Text and diagrams from the AP textbook Environment: The Science behind the Stories.

jeremy haas

on 25 March 2014

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Transcript of Energy: Alternative Energy

Environmental Science
Case Study: Mining for … cell phones?
Cell phones and other electronic devices require tantalum, which is mined in the Democratic Republic of the Congo.
1. As high technology boomed in the late 1990s, global prices for tantalum skyrocketed.

2. At the same time, the Congo was in a civil war and armies forced people to mine tantalum to raise money to fund the war.
·The case shows how our wealthy high-tech economy can be integrally linked to poor miners in poor and developing parts of the world.
Hydrogen Fuel
Conventional Technologies
"New" Renewables

Why Sweden continues to use nuclear power- technology has not made the transition possible.
The people would rather use nuclear power than fossil fuels.
Case Study: Sweden’s search for alternative energy
In 1980, Sweden’s people voted to phase out nuclear energy.
The government has promoted hydroelectric, biomass, and wind power.
Case Study: Germany goes solar
Germany produces the world’s most solar power.
German leaders see renewables as a great economic opportunity.
The feed-in tariff system requires utilities to buy power from anyone who generates it.
Case Study: Prospecting for wind in Idaho
Idaho has regions with strong winds, but no one knew which areas could support large-scale commercial wind farms.
Anemometers, devices that measure wind speed, were given to more than 80 landowners to collect local data on wind speed and direction.
The Shoshone-Bannock tribal lands were identified as an optimal site for wind farming.
Case Study: Algae as a Hydrogen Fuel Source
Certain green algae produced hydrogen when they are not doing photosynthesis.
Researchers removed sulfur from the alga’s environment to inhibit photosynthesis, but left the algae in bright light to increase its metabolic rate.
This increased its hydrogen production.
We have alternatives to Fossil Fuels.
·We need to shift to resources that are less easily depleted and environmentally gentler.

·But they are more expensive in the short term.
Nuclear energy, biomass energy and hydropower are the three most widely used alternatives to fossil fuels.

·Globally the U.S. generates the most electricity from nuclear power.

·But only 20% of U.S. electricity comes from nuclear.
Nuclear power does not create air pollution.
Nuclear fission = the splitting apart of atomic nuclei
We use 235U (half-life of 700 million years), which are incorporated into fuel rods, and release radiation in nuclear reactors.
Its ratio of energy created to the energy needed to produce it is 16:1
Uranium mining damages less land than coal mining.
If an accident or sabotage occurs, the consequences can be catastrophic.
The destroyed reactor was encased in a massive concrete sarcophagus, which is still leaking radioactive material.
Radioactivity spread widely from the Chernobyl accident.
Aging plants require maintenance and are less safe.
Governments must subsidize and operate nuclear power.
Waste disposal remains a problem.
Waste is held at 125 sites in 39 states and they are running out of room.
It is safer to store all waste in a central repository, because it can be heavily guarded.
Shipments over thousands of miles could cause a high risk of accident or sabotage.
·Some nations are rethinking this because of concerns over fossil fuels and climate change.

·Asian nations are increasing nuclear capacity and have 56 plants are under construction.

·The U.S. nuclear industry has stopped building plants.
The future of nuclear energy.
Biomass power increases recycling by using wood debris and crop residues.

Farmers, ranchers, or villages use manure & wood waste to generate electricity.
Biomass is only renewable if it is not over harvested.
Over harvesting causes deforestation, erosion, and desertification.
Biopower = biomass sources are burned in power plants.
Biofuels are liquid fuels that can power automobiles.
Ethanol = a biofuel made by fermenting crops.
·Ethanol is added to U.S. gasoline to reduce emissions.
·Flexible-fuel vehicles run on 85% ethanol, 15% gasoline.
Biodiesel = produced from vegetable oil, cooking grease, or animal fats.
Vehicles can run on 100% biodiesel.
Algae produce lipids that can be converted to biodiesel.

Their carbohydrates can be fermented to make ethanol.

Algae can be grown in wastewater/ocean water and can be harvested every few days.
New biofuels are being developed.
Cellulose ethanol = produced from structural plant material (e.g., corn stalks) that has no food value.
Ethanol may not be sustainable.
Ethanol competes with food and drives up food prices.

Its ratio of energy created to the energy needed to produce it is about 1.5:1, so it is inefficient.
Is bioenergy carbon-neutral?
Yes: Photosynthesis removes carbon that is released when biomass is burned.

No: clear cutting land (for additional fields) adds carbon emissions.

No: we use fossil fuel energy (tractors, fertilizers, etc.) during farming.
Hydroelectric power (hydropower)
Storage technique = water stored in reservoirs behind dams passes through the dam and turns turbines.
Run-of-river = generates electricity without disrupting the river’s flow.
Hydroelectric power is widely used.
Hydropower accounts for 15.6% of the world’s electricity production.
Hydropower is clean, renewable, and efficient.

Its ratio of energy created to the energy needed to produce it is 10:1.
Hydropower has negative impacts
Damming rivers destroys wildlife habitats.
Developing nations with rivers will increase hydropower.
China’s Three Gorges Dam is the world’s largest dam.
It generates as much electricity as dozens of coal-fired or nuclear plants.
It displaced 1 million people.
·Upstream areas are submerged.
·Downstream water is shallower and warmer.
·Downstream floodplains don’t get nutrients.
·Dams block fish migration and fragment habitats.
Sun, wind, geothermal heat, and ocean are referred to as “new” because:
They are not yet used on a wide scale.

Their technologies are still in a rapid phase of development.
They create jobs, income, and taxes, especially in rural areas.

They are generating more jobs than a fossil fuel economy.
Solar technologies use no fuels, are quiet and safe, contain no moving parts, and require little maintenance.
Flat plate solar collectors =
dark-colored, heat-absorbing metal plates mounted on rooftops.

Water runs through the collectors, transferring heat throughout the building.

Heated water is stored and used later.
Concentrated solar power (CSP) =
technologies that concentrate solar energy with mirrors.
Heat is transported to a steam-driven generator to create electricity.
Solar cookers = ovens that use reflectors to focus sunlight onto food.
Photovoltaic (PV) cells = convert sunlight directly into electrical energy.
Thin-film solar cells = PV materials are compressed into thin sheets.
Less efficient but inexpensive
Can be incorporated into roofing shingles, roads, etc
When light hits the two silicon plates, electrons flow and create an electric current.
Location and cost are the drawbacks.
Solar power is the most expensive way to produce electricity.
Net metering = the value of the power the consumer provides is subtracted from the monthly utility bill.
Governments have proposed economic incentives.
Wind turbines = devices that convert wind’s kinetic energy into electric energy
Wind farms = turbines erected in groups of up to hundreds of turbines.
Wind speeds are 20% greater over water than over land, and have less air turbulence.

The first U.S. offshore wind farm will have 130 turbines off Cape Cod, Massachusetts.
Wind power has many benefits.
Its ratio of energy created to the energy needed to produce it is very high, 23:1 (coal is 11:1).

Farmers and ranchers can lease their land, while still using the land for agriculture.

35,000 new U.S. wind jobs were created in 2008.
Wind sources are not always near population centers that need energy, and transmission lines need to be expanded.

Local residents often oppose them.
Wind power has some downsides.
We can take advantage of natural temperature differences between the soil and air.
Soil temperatures are nearly constant year round.
Ground source heat pumps =
geothermal pumps heat buildings in the winter by transferring heat from the ground to the building.
In summer, heat is transferred from the building to the ground.
Geothermal power plants use hot water and steam for heating homes and generating electricity.
Cold water is pumped in and heated to form steam.
Geothermal power has limits.

It may not be sustainable if the power plant withdraws water faster than it can be recharged.

It is limited to certain regions.
The rising and falling of ocean tides move large amounts of water.
Tidal energy =
dams cross the outlets of tidal bays

Water is trapped behind gates, and then outgoing tides turn turbines to generate electricity.
A hydrogen economy would provide a clean, safe, and efficient energy system by using the world’s simplest and most abundant element (hydrogen) as fuel.
Electricity produced from intermittent sources (sun, wind) would be used to produce hydrogen.
Electrolysis = electricity splits hydrogen from water

H2O -> H2 + O2
Hydrogen gas can be used as a fuel to produce electricity within fuel cells.

The chemical reaction is the reverse of electrolysis.
H2 + O2 -> H2O
Hydrogen fuel cell economy would require a massive and costly development of infrastructure.
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