Chapter 16:

Energy Efficiency & Renewable Energy

Energy Units• Power = Energy/Time = Work/Time: watts• Energy = Power x Time: watt-hour

○ kWh = kilowatt-hour (103)○ MWh = megawatt-hours (106)○ GWh = gigawatt-hours (109)○ TWh = terrawatt-hour (1012)

The Joule is another common energy unit1 kWH = 3,600,000 Joules

Energy EfficiencyImproving the percentage of total energy input that does useful work.

A lot of energy is lost due to the _____________ Law of Thermodynamics: In every energy transfer, some energy is transferred to a less useful type (usually ______)

Energy Efficiency

If 1.2 million households replaced a 60 watt incandescent bulb with a 15 watt compact fluorescent bulb for light used 4 hrs/day, ~______________ kWh/year would be saved —enough energy for ____________ homes.

http://www.cbsnews.com/video/watch/?id=7393284n

• Lighting uses 19% of the world’s energy

• There are 4.4 billion incandescent bulbs in the US.

• Law to phase them out was _______________

We could save as much as 43% of all the energy we use by improving energy efficiency.

Four widely used devices that waste a large amount of energy: • Incandescent light

bulb• Motor vehicle with an

internal __________ engine

• _______ power plant• ________-fired

power plant

EnergyInputs

System Outputs

9%7%

41%85%U.S.

economy

43%8%4%3%

Nonrenewable fossil fuels Useful energyNonrenewable nuclear Petrochemicals

Unavoidable energy waste

Biomass Unnecessary energy waste

Hydropower, geothermal, wind, solar

Energy EfficiencyNet energy efficiency: the net efficiency of the entire energy delivery process is determined by the efficiency of each __________ in the energy conversion process.

Ways to Improve Energy Efficiency

• _______________ (Combined Heat and Power- CHP): the production of two useful forms of energy from the same fuel source

Example: waste heat from generator used to heat water.

• Better insulated homes

• Use of energy efficient lighting & appliances

• Increase the fuel efficiency of motor vehicles

Energy Efficient Homes

Renewables are increasing

rapidly

Change in Electric Power Generation by State: 2004-2014

http://www.npr.org/2015/09/10/319535020/coal-gas-nuclear-hydro-how-your-state-generates-power?utm_source=facebook.com&utm_medium=social&utm_campaign=npr&utm_term=nprnews&utm_content=20150910

• Use of coal down in ____ states, only 1 has an increase (KY)

• Natural Gas has increased (ex. DE)

• Many Renewables have increased, although they are still relatively a small _____________

United States Electricity Sources• _____% from fossil fuels• Of the ____% in the

renewable (non-hydro) category, 67% is biomass

• Percentage of total US energy consumption used to generate electricity: 1940: ____%1970: ____%2010: ____%

• Nation’s electric bill = $247 Billion

• Average cost/kWh = $0.07• $247 billion/$0.07/kWh =

~3.5 TWh (3.5 x 1012)

• US has ~10,000 power plants• Average efficiency ~ ________%• Majority of plants are > _____ years old• Newer plants using ______________

can have efficiencies of 65-90%

America’s “Grid”

• 157,000 miles of high voltage transmission lines

America’s “Grid”

Substation

• _________ decreasevoltage for use in homes, etc.

• ______________ and distribution losses increased from ~5% in 1970 to ~9.5% in 2001, due to heavier use and more frequent “congestion” of the grid

• _____________ transmission lines have lower losses, but are 10x more expensive to build and are harder to maintain

America’s “Grid”: Electricity Infrastructure• Demand has increased by _______ since 1990• Construction of new lines has decreased by ________• Resulting congestion of transmission pathways create

bottlenecks, and higher costs because customers cannot get access to lower-cost electricity supplies

• Estimated cost of power outages and power quality disturbances due to congestion is $25-$180 billion per year

• Increased use of information technologies has decreased public ____________ for power quality problems

• Construction of new facilities is often tied up in __________• America’s aging infrastructure versus increased demand for

power will require large investments to upgrade the system

http://www.pbs.org/wgbh/nova/tech/power-grid.html

Renewable Energy ResourcesOriginal Energy from Sun:• Solar power• __________ • (dams, waves, solar ponds)• Wind power• BiomassEnergy Independent of Sun:• _____________ power• ____________ Fuel (maybe)• Tidal Energy (mostly)

Solar Energy_________solar _____________

•Sunlight is captured directly within a structure & converts it into low–temperature heat for space heating.

•Heat is stored in walls & floors & is released slowly throughout the day.

•A passive solar & superinsulated ____________ is the cheapest way to heat a home in regions where sunlight is available more than 60% of daylight hours.

http://www.nytimes.com/2010/09/26/business/energy-environment/26smart.html?emc=eta1&pagewanted=print

Passive Home Design

Solar Energy

____________ solar heating

•solar collectors absorb solar energy & a fan or pump supplies the building’s space or water heating needs

Pros•solar energy is free•net energy yield is high for __________ & moderate for ________

•technology is well developed & easily installed

•takes up little_____space•does not emit polluting or greenhouse gases

Cons•need to secure __________________

• solar collectors are ugly to some people

•active systems are _____

Active & Passive Solar Heating

Solar Energy to Produce Electricity

•solar energy can be converted into electrical energy by _______________ cells

•sunlight striking _________ atoms creates an electrical current

•electrical energy is stored in ___________ for use when the sun is not shining, or excess energy is sent back to the grid (________________)

Solar Energy

Solar Farm

• _______________: selling excess electricity generated by solar back to the grid.

• Gives financial incentive to homeowners, and does not waste electricity when it is produced.

Solar collectors reflect light. And are used to heat a liquid that can spin a turbine to generate electricity.

Solar Energy: Producing ElectricityWays to Generate Electricity from Sunlight________________________________________(CST)

Large-scale Solar Power Generation

Pros:• No greenhouse emissions• ___________ and reliable• _______ net energy yield• Plentiful supply in some

areasCons:• Currently _____________• Large land area required• Only some parts of country suitable• Electricity __________ for night or cloudy day use

We Can Cool Buildings Naturally TooTechnologies available:– Superinsulation and high-efficiency __________– Overhangs or awnings on windows– Light-colored _________– Reflective insulating foil in an attic– _________________ pumps– Plastic earth tubes underground

Producing electricity from

waterHydroelectric dams

Hoover Dam

• Built 1933-1942• 550 ft high• Required 12 million cubic

yards of concrete• _______ largest hydroplant in

the world)• Generates over 4.1 billion

kWh in electricity each year, enough for 2.3 million households in 11 states

Grand Coulee Dam

Three Gorges Dam: China• 607 ft high, 1.4 miles long• 1,200 towns and villages ______________• Chinese government says in addition to providing

needed energy will help control flooding on Yangtze

• 18,200 Megawatts

Hydropower Production• US is 4th in the world for hydropower production• Columbia River basin provides ______ of the US’s

hydroelectric capacity• Norway gets the highest

percentage from hydropower

HydropowerPros•No emission of greenhouse gases • _________ net energy yields•Technology well-developed, inexpensive once in

place

Cons• Dams flood ___________ habitats & alter downstream habitats• Dams interfere with _________ runs•Requires abundant water & large elevation differences•Water supplies are often ______________• In arid areas, high loss of water in reservoirs due to ________________

Producing electricity from water

TidesPros: • No greenhouse emissions

Cons: • new/developing technology, • few areas with enough

tidal or wave energy, • Potential disturbance of

tidal ____________ and fish • Limited useful areas• Tides only moving fast enough

~10 hours/day

Producing electricity from water

WavesPros: • No greenhouse emissions• Can run ________, as long as waves are large enough• Does not disturb near-shore ecosystems/animals

Cons: • often ___________• must transmit energy

to shore• Must be in areas with

significant wave action

Producing electricity from water•Ocean thermal energy conversion & solar ponds

Pros: • no greenhouse emissionsCons: • not currently _____________, • moderate energy yields, • large space required

Producing electricity from wind

Pros

•unlimited source of energy at favorable sites

•moderate to high net energy yield

•_____ to build & expand

•emit no pollutants or greenhouse gases

•land can also be used for agriculture or __________

Solutions: Wind Turbine and Wind Farms on Land and Offshore

Advantage of offshore sites: winds less ____________, and often more _________________

Disadvantage: Obstructed __________ of ocean. Corrosion in seawater.http://www.cbsnews.com/videos/battle-over-wind/

Producing electricity from windCons

•economical only in areas with _________ winds (Grid can not currently handle transport)

•back–up energy sources are necessary since winds are not always steady (doesn’t run 24/7)

•mass production takes up a great deal of land space

•________ pollution

•may interfere with migrating birds

Geothermal Energy

Using water heated from volcanic activity to create electricity.

Pros:• No greenhouse emissions• Plentiful supply in volcanic areas• Moderate net energy yields• Can run _________

Geothermal Energy

Iceland

Geothermal Energy

Cons:• Heat must be _________ to surface to be useful• Scarcity of easily ______________ sites• Extraction of water can cause land to _______• Costly in all but most concentrated sources

TRADE-OFFS

Advantages Disadvantages

Geothermal Energy

Very high efficiency Scarcity of suitable sites

Moderate net energy at accessible sites

Can be depleted if used too rapidly

Environmental costs not included in market priceLower CO2 emissions

than fossil fuelsCO2 emissions

Low cost at favorable sites

Moderate to high local air pollution

Low land use and disturbance Noise and odor (H2S)

Moderate environmental impact

High cost except at the most concentrated and accessible sources

Geothermal Heat Pumps:The ground temperature stays relative_____________year round. Geothermal pumps move a fluid through underground tubes that will be heated in the winter and cooled in the summer.

Producing energy from biomass

Producing energy from biomass

Pros

• a __________ renewable energy resource

• high net energy yield if burned near source

• Less need for imported oil

Using wood or other plantsCons

• currently exploited in nonrenewable & unsustainable ways

• single–species biomass plantations reduce ________________

• burning wood produces air pollutants such as particulates

• Biofuels have a lower __________ ____________yield than fossil fuels

• Using arable land for biomass production may reduce available lands for ________________

BiodieselProduced from vegetable oil.Sources: Palm oil, Rapeseed, Soybeans95% of biodiesel produced in the ____________________.

YieldL/ha US gal/acre

Algae ~3,000 ~300, 1500-3000Palm oil 4752 508Coconut 2151 230Rapeseed[ 954 102Soy (Indiana) 554-922 59.2-98.6Jatropha Shrub

Palm Oil Production 2006

Endangered Orangutan in Borneo

Palm Oil Production—The downside• Increases rate of clear cutting of forests in ___________ areas

Palm Oil Plantation

TRADE-OFFSBiodiesel

Advantages DisadvantagesReduced CO emissions

Increased NOxemissions and more smog

Reduced CO2emissions (78%) Higher cost than

regular dieselHigh net energy yield for oil palm crops

Environmental costs not included in market priceLow net energy yield for soybean cropsModerate net

energy yield for rapeseed crops May compete with

growing food on cropland and raise food prices

Reduced hydrocarbon emissions

Loss and degradation of biodiversity from crop plantations

Better gas mileage (40%)

Potentially renewable

Can make engines hard to start in cold weather

EthanolSources: Corn

Sugar CaneCellulosic (switch grass, crop residue)

______ is the “Saudi Arabia” of sugar cane ethanol.- Saved 50% on oil import costs since the 70’s

TRADE-OFFSEthanol Fuel

Advantages DisadvantagesHigh octane Lower driving range

Low net energy yield (corn)Some reduction in

CO2 emissions (sugarcane bagasse)

Higher CO2 emissions (corn)Much higher cost

High net energy yield (bagasse and switchgrass)

Environmental costs not included in market priceMay compete with growing food and raise food prices

Reduced CO emissions

Higher NOx emissions and more smog

Can be sold as E85 or pure ethanol

Corrosive

Can make engines hard to start in cold weather

Potentially renewable

Electric Cars

Note: from a pro-Tesla website

Electric Motor Combustion Engine

Electric Cars

Source: Union of Concerned Scientists:http://blog.ucsusa.org/rachael-nealer/gasoline-vs-electric-global-warming-emissions-953?utm_source=fb&utm_medium=fb&utm_campaign=fb

Based on “grid emissions” (i.e. amount of fossil fuels used to generate electricity by region

Electric CarsPros:• CO2 emission-free while driving• Electricity is cheaper than gas

Cons:• Limited _____________• Time to charge vs. time to fill with gas• Lack of_________________(nation-

wide rapid-charging stations)• Currently expensive• Most electricity is currently produced

from _________________• Battery replacement/disposal

But…many of these cons are changing fairly rapidly as the technology progresses

Tesla Model 3 (2017)

Hydrogen Fuels

Fig. 16–21

• Energy is used to split water into hydrogen and oxygen

• The hydrogen is stored in fuel cells

• The hydrogen then combusts with oxygen to produce water

Note: Law of Conservation of __________: The energy required to split H2O to make H2 = amount of energy obtained by combusting H2to make water

Hydrogen FuelPros:• the source of hydrogen, water, is plentiful• when burned, hydrogen produces no carbon dioxide, but

instead water vapor & nitrogen oxides• reduce _____________problems & greenhouse gas emissions

Cons:• requires energy source to split hydrogen from water• currently nonrenewable energy sources are used to produce

hydrogen, negating many benefits

• Hydrogen is highly flammable (but less explosive than gasoline)

• some hydrogen fuel is produced from _________ (CH4) , a greenhouse gas

Fig. 16-31, p. 430

TRADE-OFFSHydrogen

AdvantagesFuel cell

DisadvantagesCan be produced from plentiful water

Not found as H2 in natureEnergy is needed to produce fuelLow environmental

impact Negative net energyRenewable if produced from renewable energy resources

CO2 emissions if produced from carbon-containing compounds

No CO2 emissions if produced from water

Environmental costs not included in market price

Good substitute for oil Nonrenewable if

generated by fossil fuels or nuclear powerCompetitive price if

environmental and social costs are included in cost comparisons

High costs (that may eventually come down)

Easier to store than electricity

Will take 25 to 50 years to phase inShort driving range for current fuel-cell carsSafer than gasoline

and natural gas No fuel distribution system in placeNontoxic

High efficiency (45–65%) in fuel cells

Excessive H2 leaks may deplete ozone in the atmosphere

Hydrogen FuelSolutions• use renewable sources of energy,

most notably ________, to produce hydrogen for combustion

• currently it costs more to use solar energy than other non-renewable energies

• Sandia currently is experimenting with nanodevices that use sunlight to split water (www.sandia.gov)

• For more info on the future of hydrogen in the US, go to www.hydrogen.gov

Hydrogen FuelSolutions

• Iceland is planning to be fossil fuel-free within the next few decades by using _______________ energy to produce hydrogen fuel

Hydrogen fuel station in Reykjavik, Iceland, December, 2011Photos by Weston

Renewable Energy Solutions• Improve ______________ • Diversify the _____: use many different

energy sources so that we are not too reliant on any one source

• Give___________to individuals, cities, energy utilities to use renewable energy

• Create __________ to support renewables• Develop new technologies to improve the

implementation/feasibility of renewables

Wind Farm

Energy from

W t t

Wave Power

Solutions: Battery Technology• Most renewables energy

sources cannot run 24/7.• Diversifying the grid is a

good solution, but in the long-term, creating batteries that can store enough energy to power a city could revolutionize the grid.

Daily winter heat demand

Daily electricity demand

Home battery system

New Ideas: Battery Technology For Your Home• Tesla Powerwall: a home

battery that charges using electricity generated from solar panels, or when utility rates are low.

• Can provide a backup electricity supply if there’s a power outage.

• ___________energy storage capacity, sufficient to power most homes during

https://www.teslamotors.com/powerwall

the evening using electricity generated by solar panels during the day. Multiple batteries may be installed together for homes with greater energy needs.