RENEWABLE AND ALTERNATIVE ENERGY SOURCESMrs. Paul

Environmental Science

Chapter 17 (pgs. 264-283)

Renewable Energy Today

Renewable Energy: energy from sources constantly being formed. Include: solar energy, wind energy, water

energy, Earth’s heat. Even renewable energy affects the

environment.

Solar Energy

Solar energy: energy from the sun; absorbed by plants and used as fuel.

Sun Medium-sized star. Radiates energy from nuclear fusion reaction in

its core. High temperatures cause hydrogen nuclei to fuse,

forming helium nuclei and a loss of mass occurs. Lost mass converted to heat and light energy.

Only little bit (2-billionth) of energy reaches Earth.

All renewable energy comes from the sun. Energy reaches us as visible light and

infrared radiation.

Pros Free, clean, nonpolluting. Savings on fuel bills Collected energy can be stored.

Cons Energy source is not constant (limited

sunlight on cloudy or rainy days, none at night).

Passive Solar Heating Passive solar heating: sun’s energy is

collected, stored, and distributed naturally in an enclosed dwelling.

Not used to produce electricity. Example: Northern Hemisphere-windows

facing south receive most solar energy; passive solar buildings have windows facing south. Energy enters windows and warms the house! Heat released slowly at night.

Buildings must be well insulated with thick walls and floors to prevent heat loss.

Oriented to sun’s yearly movement.

Passive Solar Features:

Active Solar Heating

Active solar heating: energy from sun gathered by collectors and used to heat water or buildings. Solar collectors capture sun’s energy. Liquid heated as it passes through

collectors. Hot liquid pumped through heat exchanger,

which heats water for building.

Photovoltaic cells: solar cells; convert the sun’s energy into electricity, using thin wafers of semiconductor material. No moving parts, electric current generated when

electrons on negative side move to positively charged side.

Nonpolluting Produce little electrical current, need extended

sunshine to produce electricity (stored in batteries when not shining).

Energy production from solar cells has doubled every 4 years from 1985.

Wind Power-Cheap and Abundant Wind: movement of air masses as

Earth’s surface is warmed unevenly by the sun.

Wind power: converts the movement of wind into electric energy. Wind turbines are cost effective and can by

constructed quickly. Aerogenerators: windmills used to

generate electricity; also called wind turbine generators.

Wind Farms

Wind farms: large arrays of wind turbines. Take up little space. Land can still be used for farming.

Biomass-Power from Living Things Biomass Fuel: organic material that is

used as an energy source. Renewable Ex: wood, dung, plant material. Wood

Used for heating and cooking Renewable Careful-can lead to habitat loss, deforestation,

soil erosion; pollution from burning

Methane Produced when bacteria decompose organic

wastes. Burned to generate heat or electricity

Alcohol Can be made from fermenting fruit or

agricultural waste. Gasohol (gasoline and ethanol) produces less

pollution.

Hydroelectricity-Power from Moving Water Hydroelectric energy: energy produced

from moving water. Dam across river to hold back water. Water released to turn a turbine. Motion of turbine transferred to coils of wire

inside generators. Coils spin in magnetic field.

Benefits: Inexpensive to operate No air pollution Last long

Disadvantages: Dam changes river flow. Resevoir floods habitat above the dam. Water flow below dam is reduced. Dam failure can kill or injure people.

Modern Trends Micro-hydropower: electricity produced in a

small stream without having to build a big dam.

Energy from the Tides Generate electricity similarly to how

generated in river. Turbine must be able to turn in BOTH

directions.

Geothermal Energy-Power from the Earth Geothermal Energy: energy from heat in

the Earth’s crust; can be used to generate electricity.

Geothermal heat pump: a loop of piping that circulates a fluid underground, using the stable underground temperatures to warm and cool homes.

Enough heat present in the earth to melt rock. Magma: molten rock.

When it reaches the surface it is called lava.

Alternative Energy and Conservation Alternative energy: energy sources that

are still in development. To become viable, source must prove to

be cost effective, and environmental effects must be acceptable.

Tidal Power Movement of water in oceans caused by

gravitational attraction between the sun, Earth and moon.

Marked by rising and falling of sea level. As tide rises, water trapped behind the

dam. Released to turn turbine and generate electricity.

High cost to build, not many good locations.

Ocean Thermal Energy Conversion (OTEC) Warm surface water is used to boil sea

water in a vacuum chamber. The water turns to steam and turns a turbine, generating electricity.

Pumping the water up uses about 1/3 of the generated electricity.

Hydrogen Burned as a fuel. When burned, it combines with oxygen to

form water. Current production of hydrogen is not

efficient and a LOT of hydrogen is needed to produce energy.