Energy Efficiency and Renewable Energy

Chapter 16

We Waste Huge Amounts of Energy

Energy conservation• A decrease in energy use as a result of a decrease in

the amount of wasted energy – “Use less”

Energy efficiency • The measure of work we can get out of a unit of

energy we use – “Use it better”

Wasting Energy

Four widely used devices waste large amounts of energy: Incandescent light bulb: 95% lost as heat Internal combustion engine: 94% of the energy

from fuel wasted Nuclear power plant: 92% of energy is wasted

through nuclear fuel and energy needed for waste management

Coal-burning power plant: 75-80% of the energy released by burning coal is lost

Flow of Commercial Energy through the U.S. Economy

84% of all commercial energy used in the U.S. is wasted.

41% wasted due to the 2nd law of thermodynamics.

Only 9% of the total energy put into the U.S. economy results in useful energy.

Advantages of ReducingUnnecessary Energy Waste

Prolong fossil fuels supplies Reduces oil imports and improves energy

security Very high net energy yield Low cost Reduces pollution and environmental

degradation Buys time to phase in renewable energy Creates local jobs

Industry accounts for 38% of U.S. energy consumption. It can save energy and money by:• Produce both heat and electricity from one energy source

(cogeneration or combined heat and power, CHP)• Use more energy-efficient electric motors• Recycle materials• Switch from low-efficiency incandescent lighting to higher-

efficiency compact fluorescent (CFL) and LED lighting• Update the old/wasteful electrical grid system (how electricity

is transmitted from the power plant to the consumer)• Utility companies promote use of energy

• Instead, should promote conservation

We Can Save Energy and Money in Industry

We Can Save Energy and Money in Transportation

Transportation accounts for 2/3 of U.S. oil demand and is a major source of air pollution.

We can save energy in transportation by:• Increasing fuel efficiency • Making vehicles from lighter and stronger materials.

We Can Save Energy and Money in Transportation

Corporate Average Fuel Economy (CAFE) standards• The average fuel economy, in miles per gallon (mpg), of a

manufacturer’s fleet of passenger cars and/or light trucks

Fuel-efficient cars are on the market Tax breaks for buying fuel-efficient cars

Average Fuel Economy of New Vehicles Sold in the U.S. and Other Countries

CAFE standards had not increased since 1985. In May 2009, President Obama increased the standards

5% per year towards a goal of 35.5 MPG by 2016.• This represents an average of an 8 MPG increase.• Still well below Europe and Japan.

Hybrid vehicles have two types of engines working together to achieve higher gas mileage (15-70% more) and lower engine exhaust emissions:• A standard gas powered engine• An electric motor assist powered by a rechargeable

nickel-metal hydride (NiMH) battery pack

Gasoline-electric hybrid car• Mostly gas…some electric

Plug-in hybrid electric vehicle• Mostly electric…some gas

Electric vehicle (EV’s)• ALL electric

More Energy-Efficient Vehicles Are on the Way

Solutions: A Hybrid-Gasoline-Electric Engine Car and a Plug-in Hybrid Car

Plug-in hybrids can get twice the mileage of gasoline-electric hybrid cars, but…• How is the electricity generated?• Electricity from coal or nuclear power plants =

JUST AS BAD• Electricity produced by wind or solar energy =

GOOD

More Energy-Efficient Vehicles Are on the Way

Science Focus: The Search for Better Batteries

Current obstacles to hybrid or electric vehicles: Storage capacity of battery Charging time Use of rare earth metals for battery construction

We Can Design Buildings That Save Energy and Money

Green architecture• Makes use of passive solar heating, natural lighting, natural

ventilation, rain water collection, cogeneration of heat/electricity, geothermal heat pumps, and recycled building materials

Living or green roofs Superinsulation U.S. Green Building Council’s Leadership in Energy

and Environmental Design (LEED)

Graded on 100 possible points:Certified - 40 - 49 pointsSilver - 50 - 59 pointsGold - 60 - 79 pointsPlatinum - 80 points up

We Can Save Energy and Money in Existing Buildings

Insulate and plug leaks Use energy-efficient windows Stop other heating and cooling losses Heat houses more efficiently Heat water more efficiently Use energy-efficient appliances Use energy-efficient lighting

About 1/3 of the heated air in typical U.S. homes and buildings escapes through closed windows, holes, and cracks.

Individuals Matter: Ways in Which You Can Save Money Where You Live

Low-priced fossil fuels and few government tax breaks or other financial incentives for saving energy promote energy waste.

Why Are We Still Wasting So Much Energy?

A variety of renewable-energy resources are available but their use has been hindered by a lack of government support (subsides) compared to nonrenewable fossil fuels and nuclear power.• Direct solar • Moving water • Wind • Geothermal

We Can Use Renewable Energy in Place of Nonrenewable Energy Sources

Solar Power

We Can Heat Buildings and Water with Solar Energy

Passive solar heating system• Absorbs and stores heat from the sun directly within

a structure without the need for pumps to distribute the heat.

• House faces South

We Can Heat Buildings and Water with Solar Energy

Active solar heating system • Pumping a liquid such as water or an oil through

rooftop collectors• Can also be used to provide hot water

Large arrays of solar collectors in sunny deserts Costs are high and energy yield is low.

We Can Use Sunlight to Produce High-Temperature Heat and Electricity

Solar thermal systems• Sunlight is directed

towards a central tower where and oil absorbs the heat and is used to create high temperature steam to turn a turbine.

Solutions: Woman in India Uses a Solar Cooker

Solution to the “fuel wood crisis”?

Photovoltaic (PV) cells (solar cells)• Convert solar energy to electric energy • Can be made in all shapes and sizes and can be included

in the building design and construction.

We Can Use Solar Cells to Produce Electricity

We Can Use Solar Cells to Produce Electricity

Costs are high, but expected to fall with mass production & new designs

Solar cells can be used in rural villages with ample sunlight who are not connected to an electrical grid.• Mostly for pumping water

Solar cells currently only 0.2% of the world’s electricity

Solar power has the largest POTENTIAL for supplying electrical power to the world.

Hydropower

We Can Produce Electricity from Falling and Flowing Water

Hydropower Build a high dam across a large river Water builds up into a reservoir Let water flow through large pipes and turn

turbines to produce electricity

World’s leading renewable energy source used to produce electricity• 16% of the world’s electricity• 99% in Norway, only 7% in the U.S.

We Can Produce Electricity from Falling and Flowing Water

Ocean tides and waves and temperature differences between surface and bottom waters in tropical waters are not expected to provide much of the world’s electrical needs.• Few suitable sites• High costs• Equipment corrosion

Only two large tidal energy dams are currently operating: one in La Rance, France and Nova Scotia’s Bay of Fundy (where the tidal difference can be as high as 63 feet).

Tides and Waves Can Be Used to Produce Electricity

Wind

Using Wind to Produce Electricity Is an Important Step toward Sustainability

Wind power is a very promising energy resource abundant inexhaustible widely distributed cheap, clean, and emits no greenhouse gases.

Second fastest-growing source of energy

Capturing only 20% of the wind energy at the world’s best energy sites could meet all the world’s energy demands.

Solutions: Wind Turbine and Wind Farms on Land and Offshore

Wind• Captured by turbines• Converted into electrical energy

They are also used interconnected in arrays on wind farms – both on land and offshore.

Solutions: Wind Turbine and Wind Farms on Land and Offshore

Wind power is capable of becoming a major contributor to America's electricity supply over the next three decades.

According to U.S. Department of Energy, a network of wind farms in just four states could meet all U.S. electricity means.

Using Wind to Produce Electricity Is an Important Step toward Sustainability

Countries with the highest total wind power capacity:

Producing Electricity from Wind Energy Is a Rapidly Growing Global Industry

The textbook says that Germany is the world’s top wind producer, but the U.S. passed them in 2008.

Biomass

Plant materials and animal wastes can be burned to provide heat/electricity or converted into biofuels.

We Can Get Energy by Burning Solid Biomass

As the population increases, fuelwood is being harvested at unsustainable rates in developing countries. It is used for:• Cooking• Heat• Sterilization of water

We Can Get Energy by Burning Solid Biomass

We Can Convert Plants and Plant Wastesto Liquid Biofuels

Motor vehicles can run on ethanol, biodiesel, and methanol produced from plants and plant wastes.

Liquid biofuels• Biodiesel• Ethanol

Biggest producers of biofuel:• Brazil (45% of cars run on ethanol)• The United States• The European Union (large biodiesel

production/use)• China

Case Study:Is Biodiesel the Answer?

Biodiesel production from vegetable oil from a variety of different plants or even from animal fats.

95% produced by The European Union Biodiesel has the potential to supply about 10% of

the U.S.’s diesel fuel needs

Ethanol involves fermenting the sugars in certain crops such as sugarcane, corn, and switchgrass and agricultural, forestry and municipal wastes.

The ethyl alcohol is then added to gasoline.• Regular ethanol = 15% ethanol & 85% gasoline• E85 = 85% ethanol & 15% gasoline

Case Study:Is Ethanol the Answer?

Cellulosic ethanol: alternative to corn ethanol• Sources: switchgrass, crop residues, municipal wastes

Case Study:Is Ethanol the Answer?

Brazil: “Saudi Arabia of sugarcane” • Saved $50 billion in oil import costs since the 1970s

United States: ethanol from corn • Competition with the food industry over the use of corn• Drive food prices up?

Processing all corn grown in the U.S. into ethanol would cover only about 55 days of current driving.

Case Study:Is Ethanol the Answer?

GEOTHERMAL

Geothermal energy is heat stored in the soil, underground rock, and fluids in the earth’s mantle.

We can use geothermal energy stored in the earth’s mantle to heat and cool buildings.

Getting Energy from the Earth’s Internal Heat

• Geothermal heat pump (GHP) can heat and cool a house by exploiting the difference between the earth’s surface and underground temperatures.

The house is heated in the winter by transferring heat from the ground into the house.

In the summer the heat from the house is discharged into the ground.

Getting Energy from the Earth’s Internal Heat

Depending on latitude, starting at a depth of 5-10 feet, the temperature remains a constant 50-55˚ F.

Open Loop systems actually pump water from an underground aquifer through the geothermal heat pump and then discharge that water to a drainage ditch or pond.

Getting Energy from the Earth’s Internal Heat

Many times a re-injection well is used to return the water to the aquifer.

Getting Energy from the Earth’s Internal Heat

Closed Loop systems involve passing an antifreeze solution through a closed loop of tubes or pipes.• The liquid is re-circulated over and over

Deeper more concentrated hydrothermal reservoirs can be used to heat homes and buildings and spin turbines to make electricity.• Iceland

Geothermal energy problems:• High cost of tapping large-scale hydrothermal reservoirs• Dry- or wet-steam geothermal reservoirs could be depleted

Getting Energy from the Earth’s Internal Heat

HYDROGEN

Hydrogen Problems: Hydrogen is chemically locked up in water an

organic compounds (electrolysis).

It takes energy and money to produce it so the net energy is low.

Hydrogen Is a Promising Fuel but There Are Challenges

Fuel cells are the best way to use hydrogen. Fuel-efficient vehicles powered by a fuel cell that

runs on hydrogen gas are being developed.• Combines hydrogen gas (H2) and oxygen gas (O2) to

produce electricity.(2H2+O2 2H2O)

Hydrogen Is a Promising Fuel but There Are Challenges

Emits no air pollution or CO2 if the hydrogen is produced from renewable energy sources. Only water vapor!

Fuel Cell Vehicles

A more sustainable energy policy would improve:• energy efficiency• rely more on renewable energy• reduce the harmful effects of fossil fuels and

nuclear energy.

Choosing Energy Paths

Governments can use a combination of subsidies, tax breaks, rebates, taxes and public education to promote or discourage use of various energy alternatives:

• Can keep prices artificially low to encourage selected energy resources.

• Can keep prices artificially high to discourage other energy resources.

• Emphasize consumer education.

Choosing Energy Paths

Solutions: Making the Transition to a More Sustainable Energy Future