Chapter 13 Renewable Energy and Conservation

I. Direct Solar Energy

• A. Perpetually available – we will only run out when the sun’s nuclear fire burns out – found all over the earth

• B. Varies with latitude, season, time of day, and cloud cover

• C. Heating Buildings and Water

– 1. Passive solar energy

• System of putting the sun’s energy to use without requiring mechanical devices to distribute the collected heat

– 2. Certain design features can enhance passive solar energy’s heating potential – can save as much as 50% on heating costs – more expensive to install (about 7% of new homes have this)

• South facing windows (in N. hemisphere)

• Well insulated buildings

• Attic vents

• Overhangs and solar sunspaces

– 3. Solar Sunspace

• Utilizes passive solar energy to heat and cool homes

• Can be added to existing homes

Typically used to heat water

8% of energy in US is used to heat water

This technology could supply large amount of US energy demand

– 4. Active Solar Energy

• System of collecting and absorbing the sun’s energy, and using pumps or fans distribute the collected heat

– 5. Solar Thermal Electric Generation

• Means of producing electricity in which the sun’s energy is concentrated by mirrors or lenses to either heat a fluid filled pipe or drive a Stirling engine

– 6. More efficient than other solar technologies

• No air pollution

• No contribution to global warming or acid precipitation

Solar Thermal Electric Generation

• 7. Photovoltaic Solar Cells

– a. A wafer or thin film that is treated with certain metals so that they generate electricity when they absorb solar energy

b. No pollution and minimal maintenance

c. . Used on any scale

Lighted road signs

Entire buildings

d. currently provide 13,000 MW of electricity worldwide = 13 large nuclear power plants

• e. Can be incorporated into building materials – Roofing

shingles

– Tile

– Window glass

e. More economical than running electrical lines to rural areas

II. Cost of Electrical Power Plants

• A. Alternative power sources are becoming competitive with traditional power sources

III. Indirect Solar Energy

• A. Biomass

– Plant materials, such as wood, crop wastes and animal waste, used as fuel

• B. Wind energy

– Electric or mechanical energy obtained from surface air currents caused by solar warming of air

• C. Hydropower

– Form of renewable energy reliant on flowing or falling water to generate mechanical energy or electricity

IV. Biomass

• A. Contains energy from sun via photo-synthesizing plants – Oldest known fuel to humans - still used by half the

world’s population – Renewable when used no faster than it can be

produced

B. Can convert to biogas or liquids

Ethanol and methanol

Clean fuel

• C. Advantages – Reduces dependence on fossil fuels – Often uses waste materials – If trees are planted at same rate biomass is

combusted, no net increase in atmospheric CO2

• D. Disadvantages – Requires land, water and fossil fuel energy – Can lead to

• Deforestation • Desertification • Soil erosion

V. Wind Energy

• A. World’s fastest growing source of energy

• B. Wind results from sun warming the atmosphere

– Varies in direction and magnitude

• C. New wind turbines harness wind efficiently

– Most profitable in rural areas with constant wind

• E. No waste - clean source of energy

• F. Biggest constraints: – Cost

– Public resistance (NIMBY)

D. Few environmental problems

Kills birds and bats

VI. Hydropower

• A. Most efficient energy source (90%)

• B. Most widely used form of solar energy – sun powers the water cycle

– 19% of world’s energy

• D. traditional hydropower

– Suited only to large dams

• E. New technology

– Utilize low flow systems

Hydropower

VII. Other Indirect Solar Energy

• A. Ocean waves

– Produced by winds

– Has potential to turn a turbine- and create electricity

• B. Ocean Temperature Gradients

– Use difference in temperature of surface and deep water to create electricity

VIII. Other Renewable Energy Sources

• A. Geothermal energy

– Energy from the Earth’s interior for either space heating or generation of electricity

• B. Tidal Energy

– Form of renewable energy that relies of the ebb and flow of the tides to generate electricity

A. Enormous energy source

1% of heat in upper 10 km of earth crust is equal to 500x the earth’s fossil fuel sources

IX. Geothermal Energy

• B. From Hydrothermal Reservoirs

– Created by volcanoes

– Reservoirs used directly for heat or to generate electricity

• C. From hot, dry rock – fracture the rock and then run water into the fractures to make an artificial reservoir – Ex. New Mexico

• D. Geothermal heat pumps

– Use difference in temperature between surface and subsurface

– Great for heating buildings

– Expensive installation

X. Tidal Energy

• A. Typical difference between high and low tide is 1–2 ft

– Narrow bays may have greater variation

• B. Potential energy difference between low and high tide can be captured with

– A dam across a bay

– A turbine similar to a wind turbine

XI. High and Low Technology Energy Solutions

• A. Most promising “energy sources” are energy conservation and energy efficiency

• B. Energy Conservation

– Using less energy by reducing energy use and waste

• C. Energy Efficiency

– Using less energy to accomplish a given task

XII. Hydrogen as a Fuel Source

• A. Hydrogen gas (H2)

– Comprised of two hydrogen molecules

– Large amounts of available energy

– Explodes when combined with oxygen releasing energy and forming water

• B. Advantages

– Very high energy density so it could be used for gasoline in automobiles and other forms of transportation unlike coal and nuclear energy

– Can be produced from any electrical source

• Electrolysis (see illustration on next slide)

– No greenhouse gases and few other pollutants

• C. Disadvantages

– Highly volatile (requires special storage)

– Relatively inefficient

Hydrogen as a Fuel Source - Electrolysis

D. Hydrogen Fuel Cell

• Fuel cell – Device that directly converts chemical energy into

electricity

Requires hydrogen from a tank and oxygen from the air

Similar to a battery, but reactants are supplied from outside source

E. Future Applications of Fuel Cells

• Hydrogen Fuel Cell Vehicles – Hydrogen is not yet

readily available as a fuel source • 61 hydrogen

fueling stations in US

• Batteries in cell phones or laptops

XIII. Energy Consumption Trends and Economics

XIV. Energy Efficient Technologies

• Super-insulated buildings (right)

• Energy efficient appliances

• Automobiles

• Aircraft technology

• Compact Fluorescent

light bulbs

• Condensing furnaces

XV. Cogeneration

• Production of two useful forms of energy from the same fuel – generation of electricity through some thermal process (often natural gas); the residual low-temp. steam left over after electricity production is used for building or industrial heating

– Most effective on small scale

XVI. Energy Savings in Commercial Buildings

XVII. Saving Energy at Home