February 19, 2014

Chapter 17: Energy Efficiency and Renewable Energy

February 19, 2014

February 19, 2014

Energy conservation - reducing or eliminating unnecessary waste of energy

Energy efficiency - one way to conserve by using less to accomplish same task (more work/unit of energy)

*Quickest, cheapest, cleanest way to provide more energy.

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*net energy efficiency

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Some strategies to improve energy efficiency in industry...

1. Cogeneration or combined heat and power (CHP) systems

2. Replace energy-wasting electric motors

3. Switch from incandescent to fluorescent lighting

February 19, 2014

Strategies for improving energy efficiency in transportation

1. Fuel economy standards (CAFE--corporate average fuel economy standards)

2. More fuel-efficient cars• hindered by low gas prices (subsidies and tax

breaks, military protection)• government $ to allow people to buy fuel-efficient

vehicles

3. Redesign urban transportation system

February 19, 2014

Hybrid Vehicles• gasoline-powered motor + electric motor

Plug-in hybrid• 2nd battery to plug in and charge

*where does electricity come from?

February 19, 2014

Fuel cell in cars

2H2 + O2 2H2O

Advantages?

February 19, 2014

Green Architecture: Energy efficient buildings• Capture solar energy• block out sun to reduce cooling costs• use efficient lighting• thermostats• insulation• living roofs

• LEED: Leadership in Energy and Environmental design> certifies buildings based on standards> *tax breaks, rebates, grants to encourage

meeting LEED standards?

February 19, 2014

Alternative Forms of Energy• Solar• Hydropower*• Wind*• Biomass*• Geothermal• Hydrogen

*Indirect form of solar energy

February 19, 2014

Hydropower• Water flowing from higher to lower elevation• Dams Reservoir Turbines• *US largest producer of electricity from hydropower

> 7% US, 50% west coast> Little room for expansion: 98% rivers already

dammed, some need to be taken down (silt)• micro-hydrogenerator

*Not true for US

February 19, 2014

Hydropower• Tides

> Need big difference in high/low tide> expensive

• Waves• Ocean thermal energy conversion (OTEC)

> Large temperature difference between surface and deep water in tropical oceans

http://en.wikipedia.org/wiki/Ocean_thermal_energy_conversion

February 19, 2014

Windpower• difference in solar

heating of earth• Taller = more reliable

wind

February 19, 2014

Windpower: expansion?• Anemometers

> wind speed at different heights• Locations?

> land– in US: midwestern states could potentially

supply all of nation's electricity needs> offshore*

– winds are stronger and steadier– sounds– high cost

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February 19, 2014

Biomass• Directly burn organic materials (plants, animal

waste) or convert into liquid/gaseous biofuels

• mostly burned for heat not to generate electricity

• 95% energy in poorest countries

February 19, 2014

Biomass• Plants are potentially plentiful

> sustainable harvest> biomass plantation

– depletes soils, degrade biodiversity• Other sources?

> crop residue> animal manure

February 19, 2014

Biomass: Liquid biofuels • Ethanol produced by fermentation and distillation

of sugars (starch and cellulose can be broken down)> microbes> cellulosic ethanol> sugar cane and switchgrass rather than corn?

• Replace gasoline and diesel• Environmental impacts?

*Made affordable by government subsidies!

February 19, 2014

Biodiesel• alcohol + vegetable oil

*Environmental impacts of conventional farming

February 19, 2014

Geothermal Energy• Heat stored in soil, underground rocks, and fluids

in earth's mantle> original formation> radioactive decay

• Using just 1% stored heat in uppermost 5km of earth's crust provide 250x more energy than in all earth's oil and natural gas reserves

*Geothermal energy most available at volcanoes: boundaries of plates and hot spots

*US biggest producer

February 19, 2014

Geothermal Energy• Hydrothermal reservoirs

> dry steam> wet steam> hot water

February 19, 2014

Geothermal Energy

Geothermal heat pump (GHP)• difference in surface and underground temperature• fluid flowing through pipes• Winter: Heat from underground to home• Summer: Heat from home to underground

February 19, 2014

Geothermal Energy

Geothermal heat pump (GHP)• energy-efficient, reliable, environmentally clean• no pollutants, no CO2

February 19, 2014

Turning Geothermal Energy into Electricity

1. Dry steam

2. Flash steam

3. Binary cycle

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*Recirculate hot water back into ground to slow depletion

February 19, 2014

Hydrogen gas (H2)• H2 + O2 H2O• Where is the hydrogen?

> Locked up in water, organic compounds> Energy and money to produce* low energy

yield> Fuel cells are expensive> Whether it produces less air pollution than fossil

fuel depends on how hydrogen is produced– burning fossil fuels v. hydro/wind/solar power

February 19, 2014

Hydrogen• How to apply technology?

> home fueling units> energy farmers not energy hunter-gatherers> nanomaterials> store hydrogen in tanks or carbon nanofibers

February 19, 2014

Sustainable Energy Strategy• Takes at least 50 years + $$ to phase in new

energy alternatives to 10-20% total energy use• Things to consider:

> Resource> Net energy yield> $$ required?> Government research and subsidies> Environmental effects

*US

February 19, 2014

Trends:• shift from large centralized macropower systems to

smaller, decentralized micropower systems> diversity of energy resources

• energy efficiency + natural gas + sustainably produced biofuel to transition to renewable-energy resources

• continued use of fossil fuels + reduce harm while phase-in renewable energy

February 19, 2014

Policy to shift to more sustainable energy resources1. Keep price of sustainable energy resources low

> research subsidies, tax breaks2. Keep energy prices artificially high to discourage

use of a resource> eliminate tax breaks and subsidies, restrictive

regulation, add tax on use3. Consumer education

February 19, 2014

Tuesday (2/18):• Guest presentation on using solar power• Finish up chapter 17

Thursday (2/20): Start Chapter 18

Monday (2/24): Unit 6 Test (Chapter 16 and 17) *including calculations