ap enviro alt energy sources

How can you save electricity at home?

Turn thermostat down in winter and up in summer

Use energy efficient appliances

Install better insulated windows

Take faster showers to reduce hot water use

How can we save energy on a larger scale?

Use more efficient vehicles with higher miles per gallon Use hybrid vehicles, Use electric vehicles which are about 77% efficient compared to about 20% for gasoline vehicles, Use mass transportation or carpooling

Subsidies

Money from the government given to industry so the price of a service stays low or competitive

How have subsidies affected energy sources?

Fossil fuels and nuclear power have been subsidized far more than renewable energy creating an uneven playing field

How can renewable energy be improved?

Through government investment

Who are the top three users of nuclear power?

United States France and Japan

Which country gets the highest percent of energy from nuclear per capita?

France

Nuclear fission

Process that splits the nucleus of uranium-235 using neutrons to release heat energy

Fuel rods

Uranium organized into rods used in nuclear reactors

Pros of nuclear fission

No carbon emissions very efficient and no radiation released unless a meltdown occurs

Cons of nuclear fission

Nonrenewable radioactive waste storage issues potential meltdowns expensive plants and thermal pollution

How long must radioactive waste be stored to be considered safe?

At least 10 half lives

How is electricity generated in nuclear fission?

Heat creates high pressure steam which turns turbines that spin a generator

How is electricity produced in most large scale power plants?

Heat is used to create steam that turns turbines

What produces heat in different power plants?

Coal oil natural gas trash geothermal rocks and solar thermal

What comes out of coal power plant towers?

Pollutants such as CO2 SO2 NOx mercury and particulates

What comes out of nuclear power plant towers?

Steam

Half-life

The amount of time it takes for half of the radioactive atoms to decay

Do all radioisotopes have the same half-life?

No different radioisotopes have different half lives

Half-life of uranium-235

About 700 million years

Half-life of cobalt-60

5.27 years

How many half-lives turn 10 g into 1.25 g?

Three half lives

How much radon-222 remains after 4 days from 100 g?

50 g

How much radon-222 remains after 16 days from 100 g?

6.25 g

How old is a rock with 25% potassium-40 remaining?

2.5 billion years

Which is cleaner for the environment coal or nuclear?

Nuclear

Three Mile Island accident

1979 Pennsylvania accident caused by human error and mechanical failure resulting in a partial meltdown with radiation contained

Chernobyl accident

1986 explosion in Ukraine caused by human error poor design and a failed test releasing radiation across the Northern Hemisphere

Fukushima Daiichi accident

2011 earthquake and tsunami in Japan caused power failure and radiation release at about one tenth the level of Chernobyl

Pros of renewable energy sources

They do not run out produce little to no emissions create jobs and reduce dependence on other countries

Cons of renewable energy sources

Intermittent generation high construction cost lower efficiency and location dependence

Bioenergy

Energy derived from biomass

Biomass

Organic material from living or recently living organisms that is burned for energy

Examples of biomass

Wood animal waste and peat

Why biomass can be carbon neutral

Carbon released was previously absorbed during growth

Does biomass produce pollution?

Yes particulates CO CO2 and NOx

Biodiesel

A biofuel made from used vegetable oils for diesel engines

Ethanol

Alcohol fuel derived from plant sugars used in gasoline blends

E85

Fuel made of 85% ethanol and 15% gasoline

Pros of biofuels

Renewable can be carbon neutral and reduce dependence on other countries

Cons of biofuels

Uses food crops lower efficiency low EROI and environmental impacts from farming

EROI Energy Return on Investment

Amount of energy gained compared to energy used to produce it

Why corn ethanol is not very sustainable

Low EROI high land water fertilizer and pesticide use

Hydroelectric power

Electricity generated by flowing water turning turbines

How hydroelectric dams work

Water flows through a dam spins turbines and turns a generator

Dam reservoir

Area flooded to create a hydroelectric dam

Benefits of dams

Renewable electricity no emissions irrigation drinking water and flood control

Drawbacks of dams

High cost habitat destruction fish migration disruption population displacement sediment buildup and altered flooding patterns

Run-of-river technique

Diverts a portion of a river’s flow through a powerhouse and then returns it to the river

Run-of-river technique pros and cons

Less disruptive to the river’s natural flow but generates less power

Pumped storage hydropower

Moves water from a lower reservoir to a higher reservoir when electricity demand and prices are low

Wave energy

Uses the up and down motion of ocean waves to generate electricity

Tidal energy

Captures incoming tidal flow to turn turbines or stores tidal water and releases it later to generate electricity

Pros and cons of tidal energy

Renewable with no emissions but location dependent requires strong tides disrupts habitat and is expensive

Pros and cons of wave energy

Renewable with no emissions but location dependent needs consistent waves and is expensive

Solar energy

Energy from the sun

Solar energy potential

The Earth receives enough solar energy each day to power human consumption for 25 years

Major challenge of solar energy

Finding cost effective ways to efficiently collect and convert solar energy

Passive solar

Designing buildings to maximize sunlight absorption in winter and stay cool in summer using design and vegetation

Active solar

Uses devices to capture move or store solar energy

Solar water heaters

Dark heat absorbing plates collect solar heat and transfer it to hot water tanks

Solar cookers

Portable ovens that use reflectors to focus sunlight to cook food

Concentrated solar power CSP

Uses mirrors to focus sunlight onto a single point to intensify solar energy

Photovoltaic PV cells

Convert sunlight directly into electricity using silicon plates and electron transfer

Pros and cons of photovoltaic solar

Produces electricity directly with no emissions and no fuel but is expensive affected by clouds night location and transmission issues

Solar thermal power

Uses concentrated sunlight to heat water and produce steam to drive generators

Solar energy advantages

Renewable no fuel needed little maintenance and enough energy reaches Earth to power civilization

Solar energy drawbacks

Location and timing issues high equipment cost need for energy storage and toxic metals from manufacturing

Wind energy

Uses wind to spin turbines which turn generators to produce electricity

What creates wind

Uneven heating of Earth by the sun causing air movement

Pros and cons of wind energy

Renewable with no emissions and green jobs but location dependent kills birds and bats causes noise visual concerns transmission issues and cost

Wind power generation

Produced from air movement caused by differentially heated air masses

Wind turbine function

Converts mechanical wind energy into electrical energy

Wind power location factors

Depends on geography and is strongest in mountainous areas Great Plains and offshore

Wind energy benefits

Renewable no emissions high EROI about 20 to 1 and easily scalable

Geothermal energy

Thermal energy originating from beneath Earth’s surface

How geothermal energy works

Water is pumped into boreholes heated by Earth to create steam that turns turbines

Pros and cons of geothermal energy

Renewable but location dependent expensive to build releases some gases and heat sources can cool

Ground source geothermal heat pumps

Use constant underground temperatures to heat and cool buildings

Geothermal pollution

Can release CO2 methane ammonia and hydrogen sulfide but at lower levels than fossil fuels

Limitation of geothermal energy

Can be depleted if heat is removed faster than it is naturally replenished

Hydrogen fuel cell vehicles

Vehicles that use hydrogen gas to produce electricity with water as waste

Electrolysis of water

Uses electricity to split water into hydrogen and oxygen

Hydrogen from methane

Produces hydrogen more easily but releases carbon dioxide

How hydrogen fuel cells work

Hydrogen ions recombine with oxygen and electrons to form water without combustion

Hydrogen as energy storage

Excess renewable electricity can be used to make hydrogen which stores energy like a battery

Pros of hydrogen fuel cells

No carbon emissions reduce oil dependence and store excess renewable energy

Cons of hydrogen fuel cells

Expensive technology lack of infrastructure and emissions depend on energy source used to make hydrogen